| 1. |
- Achen, M G, et al.
(författare)
-
Vascular endothelial growth factor D (VEGF-D) is a ligand for the tyrosine kinases VEGF receptor 2 (Flk1) and VEGF receptor 3 (Flt4).
- 1998
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424 .- 1091-6490. ; 95:2
-
Tidskriftsartikel (refereegranskat)abstract
- We have identified a member of the VEGF family by computer-based homology searching and have designated it VEGF-D. VEGF-D is most closely related to VEGF-C by virtue of the presence of N- and C-terminal extensions that are not found in other VEGF family members. In adult human tissues, VEGF-D mRNA is most abundant in heart, lung, skeletal muscle, colon, and small intestine. Analyses of VEGF-D receptor specificity revealed that VEGF-D is a ligand for both VEGF receptors (VEGFRs) VEGFR-2 (Flk1) and VEGFR-3 (Flt4) and can activate these receptors. However. VEGF-D does not bind to VEGFR-1. Expression of a truncated derivative of VEGF-D demonstrated that the receptor-binding capacities reside in the portion of the molecule that is most closely related in primary structure to other VEGF family members and that corresponds to the mature form of VEGF-C. In addition, VEGF-D is a mitogen for endothelial cells. The structural and functional similarities between VEGF-D and VEGF-C define a subfamily of the VEGFs.
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| 2. |
- Agerberth, B, et al.
(författare)
-
FALL-39, a putative human peptide antibiotic, is cysteine-free and expressed in bone marrow and testis.
- 1995
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 92:1, s. 195-9
-
Tidskriftsartikel (refereegranskat)abstract
- PR-39, a proline/arginine-rich peptide antibiotic, has been purified from pig intestine and later shown to originate in the bone marrow. Intending to isolate a clone for a human counterpart to PR-39, we synthesized a PCR probe derived from the PR-39 gene. However, when this probe was used to screen a human bone marrow cDNA library, eight clones were obtained with information for another putative human peptide antibiotic, designated FALL-39 after the first four residues. FALL-39 is a 39-residue peptide lacking cysteine and tryptophan. All human peptide antibiotics previously isolated (or predicted) belong to the defensin family and contain three disulfide bridges. The clone for prepro-FALL-39 encodes a cathelin-like precursor protein with 170 amino acid residues. We have postulated a dibasic processing site for the mature FALL-39 and chemically synthesized the putative peptide. In basal medium E, synthetic FALL-39 was highly active against Escherichia coli and Bacillus megaterium. Residues 13-34 in FALL-39 can be predicted to form a perfect amphiphatic helix, and CD spectra showed that medium E induced 30% helix formation in FALL-39. RNA blot analyses disclosed that the gene for FALL-39 is expressed mainly in human bone marrow and testis.
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| 3. |
- Alheim, K, et al.
(författare)
-
Interleukin 1 expression is inducible by nerve growth factor in PC12 pheochromocytoma cells.
- 1991
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424 .- 1091-6490. ; 88:20, s. 9302-6
-
Tidskriftsartikel (refereegranskat)abstract
- Expression of the cytokine interleukin 1 alpha (IL-1 alpha) was demonstrated in the rat PC12 pheochromocytoma cell line by (i) immunohistochemistry using rabbit polyclonal antisera raised against the recombinant murine IL-1 alpha, (ii) an ELISA, and (iii) a specific cell conversion bioassay based on the use of LBRM33-1A5 cells. IL-1 alpha mRNA was demonstrated in the PC12 cells, by PCR amplification. Constitutive expression of IL-1 alpha in PC12 cells was demonstrated in all experiments, although the cellular levels of IL-1 alpha-like immunoreactivity varied. The expression of IL-1 alpha, as studied at the mRNA level, was inducible by mouse nerve growth factor (7S NGF), and the gene product level was inducible in a dose- and time-dependent fashion by 7S NGF. The maximum induction corresponds to a 600% increase in IL-1 alpha-like immunoreactivity above the expression level found in noninduced cells and occurred after a 3-day incubation of the cells with NGF at 0.75 micrograms/ml of culture medium. The significance of the ability of NGF to induce IL-1 expression lies in the fact that IL-1 itself also acts as a growth factor that promotes glial proliferation and, even more importantly, IL-1 itself induces the expression of NGF at peripheral nerve injury [Lindholm, D., Heumann, R., Meyer, M. & Thoenen, H. (1987) Nature (London) 330, 658-659].
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| 4. |
- Andersson, Dan I, et al.
(författare)
-
Muller's ratchet decreases fitness of a DNA-based microbe
- 1996
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424 .- 1091-6490. ; 93:2, s. 906-907
-
Tidskriftsartikel (refereegranskat)abstract
- Muller proposed that an asexual organism will inevitably accumulate deleterious mutations, resulting in an increase of the mutational load and an inexorable, ratchet-like, loss of the least mutated class [Muller, H.J. (1964) Mutat. Res. 1, 2-9]. The operation of Muller's ratchet on real populations has been experimentally demonstrated only in RNA viruses. However, these cases are exceptional in that the mutation rates of the RNA viruses are extremely high. We have examined whether Muller's ratchet operates in Salmonella typhimurium, a DNA-based organism with a more typical genomic mutation rate. Cells were grown asexually under conditions expected to result in high genetic drift, and the increase in mutational load was determined. S. typhimurium accumulated mutations under these conditions such that after 1700 generations, 1% of the 444 lineages tested had suffered an obvious loss of fitness, as determined by decreased growth rate. These results suggest that in the absence of sex and with high genetic drift, genetic mechanisms, such as back or compensatory mutations, cannot compensate for the accumulation of deleterious mutations. In addition, we measured the appearance of auxotrophs, which allowed us to calculate an average spontaneous mutation rate of approximately 0.3-1.5 x 10(-9) mutations per base pair per generation. This rate is measured for the largest genetic target studied so far, a collection of about 200 genes.
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| 5. |
- Aparicio, S, et al.
(författare)
-
Detecting conserved regulatory elements with the model genome of the Japanese puffer fish, Fugu rubripes.
- 1995
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 92:5, s. 1684-1688
-
Tidskriftsartikel (refereegranskat)abstract
- Comparative vertebrate genome sequencing offers a powerful method for detecting conserved regulatory sequences. We propose that the compact genome of the teleost Fugu rubripes is well suited for this purpose. The evolutionary distance of teleosts from other vertebrates offers the maximum stringency for such evolutionary comparisons. To illustrate the comparative genome approach for F. rubripes, we use sequence comparisons between mouse and Fugu Hoxb-4 noncoding regions to identify conserved sequence blocks. We have used two approaches to test the function of these conserved blocks. In the first, homologous sequences were deleted from a mouse enhancer, resulting in a tissue-specific loss of activity when assayed in transgenic mice. In the second approach, Fugu DNA sequences showing homology to mouse sequences were tested for enhancer activity in transgenic mice. This strategy identified a neural element that mediates a subset of Hoxb-4 expression that is conserved between mammals and teleosts. The comparison of noncoding vertebrate sequences with those of Fugu, coupled to a transgenic bioassay, represents a general approach suitable for many genome projects.
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| 6. |
- Arbiser, JL, et al.
(författare)
-
Oncogenic H-ras stimulates tumor angiogenesis by two distinct pathways
- 1997
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 94:3, s. 861-866
-
Tidskriftsartikel (refereegranskat)abstract
- The switch from a quiescent tumor to an invasive tumor is accompanied by the acquisition of angiogenic properties. This phenotypic change likely requires a change in the balance of angiogenic stimulators and angiogenic inhibitors. The nature of the angiogenic switch is not known. Here, we show that introduction of activated H-ras into immortalized endothelial cells is capable of activating the angiogenic switch. Angiogenic switching is accompanied by up-regulation of vascular endothelial growth factor and matrix metalloproteinase (MMP) bioactivity and down-regulation of tissue inhibitor of MMP. Furthermore, we show that inhibition of phosphatidylinositol-3-kinase leads to partial inhibition of tumor angiogenesis, thus demonstrating that activated H-ras activates tumor angiogenesis through two distinct pathways. Finally, we show evidence for two forms of tumor dormancy.
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| 7. |
- Aspan, A, et al.
(författare)
-
CDNA CLONING OF PROPHENOLOXIDASE FROM THE FRESH-WATER CRAYFISH PACIFASTACUS-LENIUSCULUS AND ITS ACTIVATION
- 1995
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424 .- 1091-6490. ; 92:4, s. 939-943
-
Tidskriftsartikel (refereegranskat)abstract
- Prophenoloxidase (proPO), an enzyme that is the terminal component of the so-called proPO activating system, a defense and recognition system in crustaceans and insects, has been purified and cloned from a crayfish blood cell cDNA library. The deduced ami
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| 8. |
- BAKALKIN, G, et al.
(författare)
-
[Leu5]enkephalin-encoding sequences are targets for a specific DNA-binding factor
- 1995
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 92:20, s. 9024-9028
-
Tidskriftsartikel (refereegranskat)abstract
- A DNA-binding factor with high affinity and specificity for the [Leu5]enkephalin-encoding sequences in the prodynorphin and proenkephalin genes has been characterized. The factor has the highest affinity for the [Leu5]-enkephalin-encoding sequence in the dynorphin B-encoding region of the prodynorphin gene, has relatively high affinity for other [Leu5]enkephalin-encoding sequences in the prodynorphin and proenkephalin genes, but has no apparent affinity for similar DNA sequences coding for [Met5]-enkephalin in the prodynorphin or proopiomelanocortin genes. The factor has been named [Leu5]enkephalin-encoding sequence DNA-binding factor (LEF). LEF has a nuclear localization and is composed of three subunits of about 60, 70, and 95 kDa, respectively. The highest levels were observed in rat testis, cerebellum, and spleen and were generally higher in late embryonal compared to newborn or adult animals. LEF activity was also recorded in human clonal tumor cell lines. LEF inhibited the transcription of reporter genes in artificial gene constructs where a [Leu5]enkephalin-encoding DNA fragment had been inserted between the transcription initiation site and the coding region of the reporter genes. These observations suggest that the [Leu5]enkephalin-encoding sequences in the prodynorphin and proenkephalin genes also have regulatory functions realized through interaction with a specific DNA-binding factor.
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| 9. |
- Balciunas, Darius, et al.
(författare)
-
The Med1 subunit of the yeast mediator complex is involved in both transcriptional activation and repression
- 1999
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences (PNAS). - 0027-8424 .- 1091-6490. ; 96:2, s. 376-381
-
Tidskriftsartikel (refereegranskat)abstract
- The mediator complex is essential for regulated transcription in vitro. In the yeast Saccharomyces cerevisiae, mediator comprises >15 subunits and interacts with the C-terminal domain of the largest subunit of RNA polymerase II, thus forming an RNA polymerase II holoenzyme. Here we describe the molecular cloning of the MED1 cDNA encoding the 70-kDa subunit of the mediator complex. Yeast cells lacking the MED1 gene are viable but show a complex phenotype including partial defects in both repression and induction of the GAL genes. Together with results on other mediator subunits, this implies that the mediator is involved in both transcriptional activation and repression. Similar to mutations in the SRB10 and SRB11 genes encoding cyclin C and the cyclin C-dependent kinase, a disruption of the MED1 gene can partially suppress loss of the Snf1 protein kinase. We further found that a lexA-Med1 fusion protein is a strong activator in srb11 cells, which suggests a functional link between Med1 and the Srb10/11 complex. Finally, we show that the Med2 protein is lost from the mediator on purification from Med1-deficient cells, indicating a physical interaction between Med1 and Med2.
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| 10. |
- Balzarini, J, et al.
(författare)
-
Mechanism of anti-HIV action of masked alaninyl d4T-MP derivatives
- 1996
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 93:14, s. 7295-7299
-
Tidskriftsartikel (refereegranskat)abstract
- So324 is a 2',3'-dideoxy-2',3'-didehydrothymidine-5'-monophosphate (d4T-MP) prodrug containing at the phosphate moiety a phenyl group and the methylester of alanine linked to the phosphate through a phosphoramidate linkage. So324 has anti-HIV activity in human CEM, MT4, and monocyte/macrophage cells that is superior to that of d4T. In contrast to d4T, So324 is also able to inhibit HIV replication in thymidine kinase-deficient CEM cells. After uptake of So324 by intact human lymphocytes, d4T-MP is released and subsequently converted intracellularly to d4T-TP. In addition, accumulation of substantial amounts of a novel d4T derivative has been found. This d4T metabolite has been characterized as alaninyl d4T-MP. The latter metabolite accumulates at approximately 13- to 200-fold higher levels than d4T-TP depending the experimental conditions. Alaninyl d4T-MP should be considered as an intra- and/or extracellular depot form of d4T and/or d4T-MP. These findings may explain the superior anti-retroviral activity of So324 over d4T in cell culture.
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| 11. |
- BALZARINI, J, et al.
(författare)
-
Suppression of the breakthrough of human immunodeficiency virus type 1 (HIV-1) in cell culture by thiocarboxanilide derivatives when used individually or in combination with other HIV-1-specific inhibitors (i.e., TSAO derivatives)
- 1995
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 92:12, s. 5470-5474
-
Tidskriftsartikel (refereegranskat)abstract
- Five structurally related thiophene and furane analogues of the oxathiin carboxanilide derivative NSC 615985 (UC84) (designated UC10, UC68, UC81, UC42, and UC16) were identified as potent inhibitors of HIV-1 replication in cell culture and HIV-1 reverse transcriptase activity. These compounds were markedly active against a series of mutant HIV-1 strains, containing the Leu-100-->Ile, Val-106-->Ala, Glu-138-->Lys, or Tyr-181-->Cys mutations in their reverse transcriptase. However, the thiocarboxanilide derivatives selected for mutations at amino acid positions 100 (Leu-->Ile), 101 (Lys-->Ile/Glu), 103 (Lys-->Thr/Asp) and 141 (Gly-->Glu) in the HIV-1 reverse transcriptase. The compounds completely suppressed HIV-1 replication and prevented the emergence of resistant virus strains when used at 1.3-6.6 microM--that is, 10- to 25-fold lower than the concentration required for nevirapine and bis(heteroaryl)piperazine (BHAP) U90152 to do so. If UC42 was combined with the [2',5'-bis-O-(tert-butyldimethylsilyl)-3'-spiro-5"-(4"-amino-1",2"- oxathiole-2",2"-dioxide)]-beta-D-pentofuranosyl (TSAO) derivative of N3-methylthymine (TSAO-m3T), virus breakthrough could be prevented for a much longer time, and at much lower concentrations, than if the compounds were used individually. Virus breakthrough could be suppressed for even longer, and at lower drug concentrations, if BHAP was added to the combination of UC42 with TSAO-m3T, which points to the feasibility of two- or three-drug combinations in preventing virus breakthrough and resistance development.
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| 12. |
- Bao, L, et al.
(författare)
-
Localization of neuropeptide Y Y1 receptors in cerebral blood vessels
- 1997
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 94:23, s. 12661-12666
-
Tidskriftsartikel (refereegranskat)abstract
- The localization of neuropeptide Y (NPY) Y1 receptor (R) -like immunoreactivity (LI) has been studied in cerebral arteries and arterioles of the rat by immunohistochemistry using fluorescence, confocal, and electron microscopy. High levels of Y1-R-LI were observed in smooth muscle cells (SMCs) in the small arterioles of the pial arterial network, especially on the basal surface of the brain, and low levels in the major basal cerebral arteries. The levels of Y1-R-LI varied strongly between adjacent SMCs. Y1-R-LI was associated with small endocytosis vesicles, mainly on the outer surface of the SMCs, but also on their endothelial side and often laterally at the interface between two SMCs. NPY-immunoreactive (Ir) nerve fibers could not be detected in association with the Y1-R-rich small arterioles but only around arteries with low Y1-R levels. A dense network of central NPY-Ir nerve fibers in the superficial layers of the brain was lying close to the strongly Y1-R-Ir small arterioles. The results indicate that NPY has a profound effect on small arterioles of the brain acting on Y1-Rs, both on the peripheral and luminal side of the SMCs. However, the source of the endogenous ligand, NPY, remains unclear. NPY released from central neurons may play a role, in addition to blood-borne NPY.
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| 13. |
- Barg, Sebastian, et al.
(författare)
-
The stimulatory action of tolbutamide on Ca2+-dependent exocytosis in pancreatic beta cells is mediated by a 65-kDa mdr-like P-glycoprotein
- 1999
-
Ingår i: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 96:10, s. 5539-5544
-
Tidskriftsartikel (refereegranskat)abstract
- Intracellular application of the sulfonylurea tolbutamide during whole-cell patch-clamp recordings stimulated exocytosis >5-fold when applied at a cytoplasmic Ca2+ concentration of 0.17 microM. This effect was not detectable in the complete absence of cytoplasmic Ca2+ and when exocytosis was elicited by guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS). The stimulatory action could be antagonized by the sulfonamide diazoxide, by the Cl--channel blocker 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), by intracellular application of the antibody JSB1 [originally raised against a 170-kDa multidrug resistance (mdr) protein], and by tamoxifen (an inhibitor of the mdr- and volume-regulated Cl- channels). Immunocytochemistry and Western blot analyses revealed that JSB1 recognizes a 65-kDa protein in the secretory granules. This protein exhibited no detectable binding of sulfonylureas and is distinct from the 140-kDa sulfonylurea high-affinity sulfonylurea receptors also present in the granules. We conclude that (i) tolbutamide stimulates Ca2+-dependent exocytosis secondary to its binding to a 140-kDa high-affinity sulfonylurea receptor in the secretory granules; and (ii) a granular 65-kDa mdr-like protein mediates the action. The processes thus initiated culminate in the activation of a granular Cl- conductance. We speculate that the activation of granular Cl- fluxes promotes exocytosis (possibly by providing the energy required for membrane fusion) by inducing water uptake and an increased intragranular hydrostatic pressure.
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| 14. |
- BARK, IC, et al.
(författare)
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Differential expression of SNAP-25 protein isoforms during divergent vesicle fusion events of neural development
- 1995
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 92:5, s. 1510-1514
-
Tidskriftsartikel (refereegranskat)abstract
- The presynaptic plasma membrane protein SNAP-25 (synaptosome-associated protein of 25 kDa) has been implicated as one of several neural-specific components that direct constitutive fusion mechanisms to the regulated vesicle trafficking and exocytosis of neurotransmitter release. There exist two alternatively spliced isoforms of SNAP-25, a and b, which differ in a putative membrane-interacting domain. We show that these two isoforms have distinct quantitative and anatomical patterns of expression during brain development, in neurons, and in neuroendocrine cells and that the proteins localize differently in neurites of transfected PC12 pheochromocytoma cells. These findings indicate that alternative isoforms of SNAP-25 may play distinct roles in vesicular fusion events required for membrane addition during axonal outgrowth and for release of neuromodulatory peptides and neurotransmitters.
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| 15. |
- Bergquist, Jonas, et al.
(författare)
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Discovery of endogenous catecholamines in lymphocytes and evidence for catecholamine regulation of lymphocyte function via an autocrine loop.
- 1994
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424 .- 1091-6490. ; 91:26, s. 12912-6
-
Tidskriftsartikel (refereegranskat)abstract
- Evidence has been obtained that catecholamines and their metabolites are present in single lymphocytes and extracts of T- and B-cell clones by use of capillary electrophoresis with electrochemical detection. Pharmacological inhibition of tyrosine hydroxylase reduces observed catecholamine levels, suggesting catecholamine synthesis by lymphocytes. Intracellular dopamine levels are shown to be increased by extra-cellular dopamine, suggesting a cellular-uptake mechanism. Furthermore, incubation with either dopamine or L-dihydroxyphenylalanine, a precursor of dopamine, results in a dose-dependent inhibition of lymphocyte proliferation and differentiation. Together, these results suggest the presence of an autocrine loop whereby lymphocytes down-regulate their own activity.
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| 16. |
- Bergström, F, et al.
(författare)
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The use of site-directed fluorophore labeling and donor-donor energy migration to investigate solution structure and dynamics in proteins.
- 1999
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424 .- 1091-6490. ; 96:22, s. 12477-81
-
Tidskriftsartikel (refereegranskat)abstract
- The use of molecular genetics for introducing fluorescent molecules enables the use of donor-donor energy migration to determine intramolecular distances in a variety of proteins. This approach can be applied to examine the overall molecular dimensions of proteins and to investigate structural changes upon interactions with specific target molecules. In this report, the donor-donor energy migration method is demonstrated by experiments with the latent form of plasminogen activator inhibitor type 1. Based on the known x-ray structure of plasminogen activator inhibitor type 1, three positions forming the corners of a triangle were chosen. Double Cys substitution mutants (V106C-H185C, H185C-M266C, and M266C-V106C) and corresponding single substitution mutants (V106C, H185C, and M266C) were created and labeled with a sulfhydryl specific derivative of BODIPY (=the D molecule). The side lengths of this triangle were obtained from analyses of the experimental data. The analyses account for the local anisotropic order and rotational motions of the D molecules, as well as for the influence of a partial DD-labeling. The distances, as determined from x-ray diffraction, between the C(alpha)-atoms of the positions V106C-H185C, H185C-M266C, and M266C-V106C were 60.9, 30.8, and 55.1 A, respectively. These are in good agreement with the distances of 54 +/- 4, 38 +/- 3, and 55 +/- 3 A, as determined between the BODIPY groups attached via linkers to the same residues. Although the positions of the D-molecules and the C(alpha)-atoms physically cannot coincide, there is a reasonable agreement between the methods.
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| 17. |
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| 18. |
- Bertilsson, G, et al.
(författare)
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Identification of a human nuclear receptor defines a new signaling pathway for CYP3A induction
- 1998
-
Ingår i: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 95:21, s. 12208-12213
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Nuclear receptors regulate metabolic pathways in response to changes in the environment by appropriate alterations in gene expression of key metabolic enzymes, Here, a computational search approach based on iteratively built hidden Markov models of nuclea
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| 19. |
- Bjorkman, J, et al.
(författare)
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Virulence of antibiotic-resistant Salmonella typhimurium
- 1998
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Ingår i: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA. - : NATL ACAD SCIENCES. - 0027-8424. ; 95:7, s. 3949-3953
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We show that most Salmonella typhimurium mutants resistant to streptomycin, rifampicin, and nalidixic acid are avirulent in mice, Of seven resistant mutants examined, sis were avirulent and one was similar to the wild type In competition experiments in mi
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| 20. |
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| 21. |
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| 22. |
- Bonetto, V, et al.
(författare)
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Two alternative processing pathways for a preprohormone: a bioactive form of secretin
- 1995
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 92:26, s. 11985-11989
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Tidskriftsartikel (refereegranskat)abstract
- An N-terminally 9-residue elongated form of secretin, secretin-(-9 to 27) amide, was isolated from porcine intestinal tissue and characterized. Current knowledge about peptide processing sites does not allow unambiguous prediction of the signal peptide cleavage site in preprosecretin but suggests cleavage in the region of residues -10 to -14 counted upstream from the N terminus of the hormone. However, the structure of the isolated peptide suggests that the cleavage between the signal peptide and the N-terminal propeptide occurs at the C-terminal side of residue -10. Moreover, the isolated peptide demonstrates that secretin can be fully processed C-terminally prior to the final N-terminal cleavage. The results from this report, and those from earlier studies, where C-terminally elongated variants were isolated, show that the processing of the secretin precursor may proceed by one of two alternative pathways, in which either of the two ends is processed first. The bioactivity of the N-terminally extended peptide on exocrine pancreatic secretion was lower than that of secretin, indicating the importance of the finally processed free N terminus of the hormone for interaction with secretin receptors.
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| 23. |
- BONFOCO, E, et al.
(författare)
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Apoptosis and necrosis: two distinct events induced, respectively, by mild and intense insults with N-methyl-D-aspartate or nitric oxide/superoxide in cortical cell cultures
- 1995
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 92:16, s. 7162-7166
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Tidskriftsartikel (refereegranskat)abstract
- N-Methyl-D-aspartate (NMDA) receptor-mediated neurotoxicity may depend, in part, on the generation of nitric oxide (NO.) and superoxide anion (O2.-), which react to form peroxynitrite (OONO-). This form of neurotoxicity is thought to contribute to a final common pathway of injury in a wide variety of acute and chronic neurologic disorders, including focal ischemia, trauma, epilepsy, Huntington disease, Alzheimer disease, amyotrophic lateral scelerosis, AIDS dementia, and other neurodegenerative diseases. Here, we report that exposure of cortical neurons to relatively short durations or low concentrations of NMDA, S-nitrosocysteine, or 3-morpholinosydnonimine, which generate low levels of peroxynitrite, induces a delayed form of neurotoxicity predominated by apoptotic features. Pretreatment with superoxide dismutase and catalase to scavenge O2.- partially prevents the apoptotic process triggered by S-nitrosocysteine or 3-morpholinosydnonimine. In contrast, intense exposure to high concentrations of NMDA or peroxynitrite induces necrotic cell damage characterized by acute swelling and lysis, which cannot be ameliorated by superoxide dismutase and catalase. Thus, depending on the intensity of the initial insult, NMDA or nitric oxide/superoxide can result in either apoptotic or necrotic neuronal cell damage.
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| 24. |
- Bremer, K, et al.
(författare)
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East Gondwana ancestry of the sunflower alliance of families
- 1997
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Ingår i: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA. - : NATL ACAD SCIENCES. - 0027-8424. ; 94:17, s. 9188-9190
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The sunflower alliance of families comprises nearly 10% of all flowering plant species and includes the largest of all plant families, the sunflower family Asteraceae, which has 23,000 species, and the bellflower family Campanulaceae, Both are worldwide i
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| 25. |
- Brismar, H, et al.
(författare)
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Dopamine-induced recruitment of dopamine D1 receptors to the plasma membrane
- 1998
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 95:10, s. 5573-5578
-
Tidskriftsartikel (refereegranskat)abstract
- The recruitment of G protein-coupled receptors from the cytoplasm to the plasma membrane generally is believed to be a constitutive process. We show here by the use of both confocal microscopy and subcellular fractionation that, for at least one such receptor, this recruitment is regulated and not constitutive. Cells from a proximal tubular-like cell line, LLCPK1 cells, were incubated with either a D1 agonist, a dopamine precursor, or an inhibitor of dopamine metabolism to increase dopamine availability in the cell. Each of the three procedures led to a rapid translocation of dopamine D1 receptors from the cytosol to the plasma membrane.
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| 26. |
- Broberger, C, et al.
(författare)
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The neuropeptide Y/agouti gene-related protein (AGRP) brain circuitry in normal, anorectic, and monosodium glutamate-treated mice
- 1998
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 95:25, s. 15043-15048
-
Tidskriftsartikel (refereegranskat)abstract
- Neuropeptide Y (NPY) and the endogenous melanocortin receptor antagonist, agouti gene-related protein (AGRP), coexist in the arcuate nucleus, and both exert orexigenic effects. The present study aimed primarily at determining the brain distribution of AGRP. AGRP mRNA-expressing cells were limited to the arcuate nucleus, representing a major subpopulation (95%) of the NPY neurons, which also was confirmed with immunohistochemistry. AGRP-immunoreactive (-ir) terminals all contained NPY and were observed in many brain regions extending from the rostral telencephalon to the pons, including the parabrachial nucleus. NPY-positive, AGRP-negative terminals were observed in many areas. AGRP-ir terminals were reduced dramatically in all brain regions of mice treated neonatally with monosodium glutamate as well as of mice homozygous for the anorexia mutation. Terminals immunoreactive for the melanocortin peptide α-melanocyte-stimulating hormone formed a population separate from, but parallel to, the AGRP-ir terminals. Our results show that arcuate NPY neurons, identified by the presence of AGRP, project more extensively in the brain than previously known and indicate that the feeding regulatory actions of NPY may extend beyond the hypothalamus.
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| 27. |
- BRUNGS, M, et al.
(författare)
-
Sequential induction of 5-lipoxygenase gene expression and activity in Mono Mac 6 cells by transforming growth factor beta and 1,25-dihydroxyvitamin D3
- 1995
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 92:1, s. 107-111
-
Tidskriftsartikel (refereegranskat)abstract
- 5-Lipoxygenase (5-LO; EC 1.13.11.34) activity in the human monocytic cell line Mono Mac 6 was upregulated by combined treatment with transforming growth factor beta 1 (TGF-beta) and 1,25-dihydroxyvitamin D3 (VD3). In undifferentiated cells, 5-LO enzyme activity was undetectable. After the addition of TGF-beta plus VD3, the activity of intact cells was 800 ng per 10(6) cells--500 times more than the assay detection limit. Also 5-LO protein and mRNA expression were induced > 128-fold and 64-fold, respectively, as compared to undifferentiated cells. Both TGF-beta and VD3 were required for these prominent responses. Either agent alone gave small amounts of 5-LO protein and mRNA but very low 5-LO activities. After the addition of TGF-beta and VD3, the induction of 5-LO protein was obvious after 1 day, but the increase in activity was delayed and did not appear until the second day. Pretreatment of cells with TGF-beta or VD3 alone for 2 days led to 5-LO protein expression but very low enzyme activity. Addition of the lacking second inducer was required for full induction of 5-LO protein expression and for upregulation of enzyme activity. Partial purification of 5-LO from Mono Mac 6 cells and recombination with soluble cellular proteins from different sources indicated the presence of cytosolic factors that affect the activity of 5-LO.
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| 28. |
- Bry, L, et al.
(författare)
-
Genetic engineering of carbohydrate biosynthetic pathways in transgenic mice demonstrates cell cycle-associated regulation of glycoconjugate production in small intestinal epithelial cells
- 1996
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 93:3, s. 1161-1166
-
Tidskriftsartikel (refereegranskat)abstract
- Proliferation, migration-associated differentiation, and cell death occur continuously and in a spatially well-organized fashion along the crypt-villus axis of the mouse small intestine, making it an attractive system for studying how these processes are regulated and interrelated. A pathway for producing glycoconjugates was engineered in adult FVB/N transgenic mice by expressing a human alpha 1,3/4-fucosyltransferase (alpha 1,3/4-FT; EC 2.4.1.65) along the length of this crypt-villus axis. The alpha 1,3/4-FT can use lacto-N-tetraose or lacto-neo-N-tetraose core chains to generate Lewis (Le) blood group antigens Le(a) or Le(x), respectively, and H type 1 or H type 2 core chains to produce Leb and Le(y). Single- and multilabel immunohistochemical studies revealed that expression of the alpha 1,3/4-FT results in production of Le(a) and Leb antigens in both undifferentiated proliferated crypt cells and in differentiated postmitotic villus-associated epithelial cells. In contrast, Le(x) antigens were restricted to crypt cells. Villus enterocytes can be induced to reenter the cell cycle by expression of simian virus 40 tumor antigen under the control of a promoter that only functions in differentiated members of this lineage. Bitransgenic animals, generated from a cross of FVB/N alpha 1,3/4-FT with FVB/N simian virus 40 tumor antigen mice, expand the range of Le(x) expression to include villus-associated enterocytes that have reentered the cell cycle. Thus, the fucosylations unveil a proliferation-dependent switch in oligosaccharide production, as defined by a monoclonal antibody specific for the Le(x) epitope. These findings show that genetic engineering of oligosaccharide biosynthetic pathways can be used to define markers for entry into, or progression through, the cell cycle and to identify changes in endogenous carbohydrate metabolism that occur when proliferative status is altered in a manner that is not deleterious to the system under study.
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| 29. |
- Campbell, D, et al.
(författare)
-
The cyanobacterium Synechococcus resists UV-B by exchanging photosystem II reaction-center D1 proteins
- 1998
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424 .- 1091-6490. ; 95:1, s. 364-369
-
Tidskriftsartikel (refereegranskat)abstract
- Current ambient UV-B levels can significantly depress productivity in aquatic habitats, largely because UV-B inhibits several steps of photosynthesis, including the photooxidation of water catalyzed by photosystem II, We show that upon UV-B exposure the cyanobacterium Synechococcus sp, PCC 7942 rapidly changes the expression of a family of three psbA genes encoding photosystem II D1 proteins, In wild-type cells the psbAI gene is expressed constitutively, but strong accumulations of psbAII and psbAIII transcripts are induced within 15 min of moderate UV-B exposure (0.4 W/m(2)), This transcriptional response causes an exchange of two distinct photosystem II D1 proteins, D1:1 is encoded by psbAI, but on UV-B exposure, it is largely replaced by the alternate D1:2 form, encoded by both psbAII and psbAIII, The total content of D1 and other photosystem II reaction center protein, D2, remained unchanged throughout the UV exposure, as did the content and composition of the phycobilisome, Wild-type cells suffered only slight transient inhibition of photosystem II function under UV-B exposure, In marked contrast, under the same UV-B treatment, a mutant strain expressing only psbAI suffered severe (40%) and sustained inhibition of photosystem II function, Another mutant strain with constitutive expression of psbAII and psbAIII was almost completely resistant to the UV-B treatment, showing no inhibition of photosystem II function and only a slight drop in electron transport, In Synechococcus the rapid exchange of alternate D1 forms, therefore, accounts for much of the cellular resistance to UV-B inhibition of photosystem II activity and photosynthetic electron transport, This molecular plasticity may be an important element in community-level responses to UV-B, where susceptibility to UV-B inhibition of photosynthesis changes diurnally.
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| 30. |
- Cao, RH, et al.
(författare)
-
Suppression of angiogenesis and tumor growth by the inhibitor K1-5 generated by plasmin-mediated proteolysis
- 1999
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 96:10, s. 5728-5733
-
Tidskriftsartikel (refereegranskat)abstract
- Proteolytic enzymes are involved in generation of a number of endogenous angiogenesis inhibitors. Previously, we reported that angiostatin, a potent angiogenesis inhibitor, is a proteolytic fragment containing the first four kringle modules of plasminogen. In this report, we demonstrate that urokinase-activated plasmin can process plasminogen to release an angiogenesis inhibitor, K1–5 (protease-activated kringles 1–5). K1–5 inhibits endothelial-cell proliferation with a half-maximal concentration of approximately 50 pM. This inhibitory effect is endothelial-cell-specific and appears to be at least approximately 50-fold greater than that of angiostatin. A synergistic efficacy of endothelial inhibition was observed when angiostatin and kringle 5 (K5) were coincubated with capillary endothelial cells. The synergistic effect is comparable to that produced by K1–5 alone. Systemic treatment of mice with K1–5 at a low dose significantly blocked the fibroblast growth factor-induced corneal neovascularization, whereas angiostatin had no effect at the same dose. K1–5 also suppressed angiogenesis in chicken embryos. Systemic administration of K1–5 at a low dose at which angiostatin was ineffective significantly suppressed the growth of a murine T241 fibrosarcoma in mice. The antitumor effect correlates with the reduced neovascularization. These findings suggest that the plasmin-mediated proteolysis may be involved in the negative switch of angiogenesis.
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| 31. |
- Castellazzi, M., et al.
(författare)
-
Overexpression of c-jun, junB, or junD affects cell growth differently
- 1991
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 88:20, s. 8890-8894
-
Tidskriftsartikel (refereegranskat)abstract
- The coding sequences of murine c-jun, junB, or junD, which code for proteins with practically identical dimerization and DNA binding properties, were introduced into a nondefective retroviral vector, and the phenotype of primary avian fibroblasts chronically infected with each of these viruses was studied. Cells expressing c-jun grew in low-serum medium and developed into colonies in agar, two properties characteristic of in vitro transformation. Cells expressing junB grew in agar, with a reduced efficiency as compared to c-jun, but did not grow in low-serum medium. Finally, no effect of junD expression on cell growth was observed. These different phenotypes suggest that these three closely related transcription factors play distinct roles during normal cell growth. Analysis of c-jun deletion mutants and of c-jun/junB and c-jun/junD chimeric genes showed that the N-terminal portion (amino acids 2-168) of the c-Jun protein that is involved in transcriptional activation is required for efficient transformation. On the contrary, cells expressing a truncated mouse c-Jun lacking this N-terminal domain grew slower than normal embryo fibroblasts. The reduced growth rate may be related to the finding that expression of the intact or the truncated mouse c-jun repressed the endogenous avian c-Jun homologue, suggesting that functional c-Jun product is required for normal cell growth.
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| 32. |
- Chapman, K B, et al.
(författare)
-
Initiator methionine tRNA is essential for Ty1 transposition in yeast
- 1992
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academies Press. - 0027-8424 .- 1091-6490. ; 89:8, s. 3236-3240
-
Tidskriftsartikel (refereegranskat)abstract
- The yeast retrotransposon Ty1 transposes through an RNA intermediate by a mechanism similar to that of retroviral reverse transcription and integration. Ty1 RNA contains a putative minus strand primer binding site (-PBS) that is complementary to the 3' acceptor stem of the initiator methionine tRNA (tRNA(iMet)). Here we demonstrate that the tRNA(iMet) is used as a primer for Ty1 reverse transcription. Mutations in the Ty1 element that alter 5 of 10 nucleotides that are complementary to the tRNA(iMet) abolish Ty1 transposition, even though they are silent with regard to Ty1 protein coding. We have constructed a yeast strain lacking wild-type tRNA(iMet) that is dependent on a mutant derivative of tRNA(iMet) that has an altered acceptor stem sequence, engineered to restore homology with the Ty1 -PBS mutant. The compensatory mutations made in the tRNA(iMet) alleviate the transposition defect of the Ty1 -PBS mutant. The mutant and wild-type tRNA(iMet) are enriched within Ty1 virus-like particles irrespective of complementarity to the Ty1 -PBS. Thus, complementarity between the Ty1 -PBS and tRNA(iMet) is essential for transposition but is not necessary for packaging of the tRNA inside virus-like particles.
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| 33. |
- Chung, J S, et al.
(författare)
-
A remarkable, precisely timed release of hyperglycemic hormone from endocrine cells in the gut is associated with ecdysis in the crab Carcinus maenas
- 1999
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 96:23, s. 13103-7
-
Tidskriftsartikel (refereegranskat)abstract
- Molting or ecdysis is the most fundamentally important process in arthropod life history, because shedding of the exoskeleton is an absolute prerequisite for growth and metamorphosis. Although the hormonal mechanisms driving ecdysis in insects have been studied extensively, nothing is known about these processes in crustaceans. During late premolt and during ecdysis in the crab Carcinus maenas, we observed a precise and reproducible surge in hemolymph hyperglycemic hormone (CHH) levels, which was over 100-fold greater than levels seen in intermolt animals. The source of this hormone surge was not from the eyestalk neurosecretory tissues but from previously undescribed endocrine cells (paraneurons), in defined areas of the foregut and hindgut. During premolt (the only time when CHH is expressed by these tissues), the gut is the largest endocrine tissue in the crab. The CHH surge, which is a result of an unusual, almost complete discharge of the contents of the gut endocrine cell, regulates water and ion uptake during molting, thus allowing the swelling necessary for successful ecdysis and the subsequent increase in size during postmolt. This study defines an endocrine brain/gut axis in the arthropods. We propose that the ionoregulatory process controlled by CHH may be common to arthropods, in that, for insects, a similar mechanism seems to be involved in antidiuresis. It also seems likely that a cascade of very precisely coordinated release of (neuro) hormones controls ecdysis.
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| 34. |
- Claesson-Welsh, Lena, et al.
(författare)
-
Angiostatin induces endothelial cell apoptosis and activation of focal adhesion kinase independently of the integrin-binding motif RGD
- 1998
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424 .- 1091-6490. ; 95:10, s. 5579-5583
-
Tidskriftsartikel (refereegranskat)abstract
- Angiostatin, a fragment of plasminogen, has been identified and characterized as an endogenous inhibitor of neovascularization. We show that angiostatin treatment of endothelial cells in the absence of growth factors results in an increased apoptotic index whereas the proliferation index is unchanged. Angiostatin also inhibits migration and tube formation of endothelial cells. Angiostatin treatment has no effect on growth factor-induced signal transduction but leads to an RGD-independent induction of the kinase activity of focal adhesion kinase, suggesting that the biological effects of angiostatin relate to subversion of adhesion plaque formation in endothelial cells.
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| 35. |
- CLARKE, AK, et al.
(författare)
-
2 FUNCTIONALLY DISTINCT FORMS OF THE PHOTOSYSTEM-II REACTION-CENTER PROTEIN D1 IN THE CYANOBACTERIUM SYNECHOCOCCUS SP PCC 7942
- 1993
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 90:24, s. 11985-11989
-
Tidskriftsartikel (refereegranskat)abstract
- The cyanobacterium Synechococcus sp. PCC 7942 possesses a small psbA multigene family that codes for two distinct forms of the photosystem II reaction-center protein D1 (D1:1 and D1:2). We showed previously that the normally predominant D1 form (D1:1) was rapidly replaced with the alternative D1:2 when cells adapted to a photon irradiance of 50 mumol/m-2.s-1 are shifted to 500 mumol.m-2.s-1 and that this interchange was readily reversible once cells were allowed to recover under the original growth conditions. By using the psbA inactivation mutants R2S2C3 and R2K1 (which synthesize only D1:1 and D1:2, respectively), we showed that this interchange between D1 forms was essential for limiting the degree of photoinhibition as well as enabling a rapid recovery of photosynthesis. In this report, we have extended these findings by examining whether any intrinsic functional differences exist between the two D1 forms that may afford increased resistance to photoinhibition. Initial studies on the rate of D1 degradation at three photon-irradiances (50, 200, and 500 mumol.m-2.s-1) showed that the rates of degradation for both D1 forms increase with increasing photon flux density but that there was no significant difference between D1:1 and D1:2. Analysis of light-response curves for oxygen evolution for the mutants R2S2C3 and R2K1 revealed that cells with photosystem II reaction centers containing D1:2 have a higher apparent quantum yield (almost-equal-to 25%) than cells possessing D1:1. Further studies using chlorophyll a fluorescence measurements confirmed that R2K1 has a higher photochemical yield than R2S2C3; that is, a more efficient conversion of excitation energy from photon absorption into photochemistry. We believe that the higher photochemical efficiency of reaction centers containing D1:2 is causally related to the preferential induction of D1:2 at high light and thus may be an integral component of the protection mechanism within Synechococcus sp. PCC 7942 against photoinhibition.
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| 36. |
- CLARKE, AK, et al.
(författare)
-
RAPID INTERCHANGE BETWEEN 2 DISTINCT FORMS OF CYANOBACTERIAL PHOTOSYSTEM-II REACTION-CENTER PROTEIN-D1 IN RESPONSE TO PHOTOINHIBITION
- 1993
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 90:21, s. 9973-9977
-
Tidskriftsartikel (refereegranskat)abstract
- We have studied photoinhibition of photosynthesis in the cyanobacterium Synechococcus sp. PCC 7942, which possesses two distinct forms of the photosystem II reaction-center protein D1 (D1:1 and D1:2). We report here that when cells adapted to a growth irradiance of 50 mumol.m-2.s-1 are exposed to an irradiance of 500 mumol.m-2.s-1, the normally predominant D1 form (D1:1) is rapidly replaced with the alternative D1:2. This interchange is not only complete within the first hour of photoinhibition but is also fully reversible once cells are returned to 50 mumol.m-2.s-1. By using a mutant that synthesizes only D1:1, we show that the failure to replace D1:1 with D1:2 during photoinhibition results in severe loss of photosynthetic activity as well as a diminished capacity to recover after the stress period. We believe that this interchange between D1 forms may constitute an active component in a protection mechanism unique among photosynthetic organisms that enables cyanobacteria to effectively cope with and recover from photoinhibition.
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| 37. |
- Collingwood, T N, et al.
(författare)
-
A natural transactivation mutation in the thyroid hormone beta receptor: impaired interaction with putative transcriptional mediators.
- 1997
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424. ; 94:1, s. 248-53
-
Tidskriftsartikel (refereegranskat)abstract
- The syndrome of resistance to thyroid hormone is characterized by elevated serum free thyroid hormones, failure to suppress pituitary thyrotropin secretion, and variable peripheral refractoriness to hormone action. Here we describe a novel leucine to valine mutation in codon 454 (L454V) of the thyroid hormone beta receptor (TR beta) in this disorder, resulting in a mutant receptor with unusual functional properties. Although the mutant protein binds ligand comparably to wild-type receptor and forms homo- and heterodimers on direct repeat, everted repeat, or palindromic thyroid response elements, its ability to activate transcription via these elements is markedly impaired. The hydrophobic leucine residue lies within an amphipathic alpha-helix at the carboxyl terminus of TR beta and the position of the homologous residue in the crystal structure of TR alpha indicates that its side chain is solvent-exposed and might interact with other proteins. We find that two putative transcriptional mediators (RIP140 and SRC-1) exhibit hormone-dependent association with wild-type TR. In comparison, the interaction of this natural mutant (L454V) and artificial mutants (L454A, E457A) with RIP140 and SRC-1 is markedly reduced. Furthermore, coexpression of SRC-1 is able to restore the transcriptional activity of the L454V mutant receptor, indicating that the interaction of this residue with accessory proteins is critical for transcriptional activation. Finally, the occurrence of the L454V mutation in resistance to thyroid hormone, together with impaired negative regulation of the thyroid-stimulating hormone alpha promoter by this mutant, suggests that the amphipathic alpha-helix also mediates hormone-dependent transcriptional inhibition, perhaps via interaction with these or other accessory factors.
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| 38. |
- Colucci, Francesco, et al.
(författare)
-
Apoptosis resistance of nonobese diabetic peripheral lymphocytes linked to the Idd5 diabetes susceptibility region
- 1997
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 94:16, s. 8670-8674
-
Tidskriftsartikel (refereegranskat)abstract
- Defects in lymphocyte apoptosis may lead to autoimmune disorders and contribute to the pathogenesis of type 1 diabetes. Lymphocytes of nonobese diabetic (NOD) mice, an animal model of autoimmune diabetes, have been found resistant to various apoptosis signals, including the alkylating drug cyclophosphamide. Using an F2 intercross between the apoptosis-resistant NOD mouse and the apoptosis-susceptible C57BL/6 mouse, we define a major locus controlling the apoptosis-resistance phenotype and demonstrate its linkage (logarithm of odds score = 3.9) to a group of medial markers on chromosome 1. The newly defined gene cannot be dissociated from Ctla4 and Cd28 and in fact marks a 20-centimorgan region encompassing Idd5, a previously postulated diabetes susceptibility locus. Interestingly, we find that the CTLA-4 (cytotoxic T lymphocyte-associated antigen 4) and the CD28 costimulatory molecules are defectively expressed in NOD mice, suggesting that one or both of these molecules may be involved in the control of apoptosis resistance and, in turn, in diabetes susceptibility.
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| 39. |
- Connell, H., et al.
(författare)
-
Type 1 fimbrial expression enhances Escherichia coli virulence for the urinary tract
- 1996
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 93:18, s. 9827-9832
-
Tidskriftsartikel (refereegranskat)abstract
- Type 1 fimbriae are adhesion organelles expressed by many Gram-negative bacteria. They facilitate adherence to mucosal surfaces and inflammatory cells in vitro, but their contribution to virulence has not been defined. This study presents evidence that type 1 fimbriae increase the virulence of Escherichia coli for the urinary tract by promoting bacterial persistence and enhancing the inflammatory response to infection. In a clinical study, we observed that disease severity was greater in children infected with E. coli O1:K1:H7 isolates expressing type 1 fimbriae than in those infected with type 1 negative isolates of the same serotype. The E. coli O1:K1:H7 isolates had the same electrophoretic type, were hemolysin-negative, expressed P fimbriae, and carried the fim DNA sequences. When tested in a mouse urinary tract infection model, the type 1-positive E. coli O1:K1:H7 isolates survived in higher numbers, and induced a greater neutrophil influx into the urine, than O1:K1:H7 type 1-negative isolates. To confirm a role of type 1 fimbriae, a fimH null mutant (CNI016) was constructed from an O1:K1:H7 type 1-positive parent. E. coli CNI016 had reduced survival and inflammatogenicity in the mouse urinary tract infection model. E. coli CNI016 reconstituted with type 1 fimbriae (E. coli CN1018) had restored virulence similar to that of the wild- type parent strain. These results show that type 1 fimbriae in the genetic background of a uropathogenic strain contribute to the pathogenesis of E. coli in the urinary tract.
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| 40. |
- DAHLMANWRIGHT, K, et al.
(författare)
-
Structural characterization of a minimal functional transactivation domain from the human glucocorticoid receptor
- 1995
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 92:5, s. 1699-1703
-
Tidskriftsartikel (refereegranskat)abstract
- A 58-amino acid polypeptide containing the functional core region, the tau 1 core, of the major transactivation domain of the human glucocorticoid receptor has been expressed in Escherichia coli and purified to homogeneity. The polypeptide retains 60-70% of the activity of the intact domain when assayed in vivo or in vitro. This report describes a structural characterization of the tau 1 core peptide fragment. Circular dichroism spectroscopy shows that the tau 1 core and a larger fragment encompassing the intact tau 1 domain are largely unstructured in water solution under a variety of pH conditions. The tau 1 core, however, acquires a significant alpha-helical structure when analyzed in the presence of trifluoroethanol, an agent that favors secondary structure formation in regions that have propensity for alpha-helical conformation. Two- and three-dimensional NMR spectroscopy of 15N-labeled tau 1 core, in the presence of trifluoroethanol, has allowed sequential assignment of 1H and 15N resonances and identification of three protein segments with alpha-helical character. Potentially helix-breaking proline substitutions, in proposed alpha-helical regions, lead to reduced activity, suggesting that alpha-helices are important for transactivation in vivo.
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| 41. |
- Edman, L, et al.
(författare)
-
Conformational transitions monitored for single molecules in solution
- 1996
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 93:13, s. 6710-6715
-
Tidskriftsartikel (refereegranskat)abstract
- Phenomena that can be observed for a large number of molecules may not be understood if it is not possible to observe the events on the single-molecule level. We measured the fluorescence lifetimes of individual tetramethylrhodamine molecules, linked to an 18-mer deoxyribonucleotide sequence specific for M13 DNA, by time-resolved, single-photon counting in a confocal fluorescence microscope during Brownian motion in solution. When many molecules were observed, a biexponential fluorescence decay was observed with equal amplitudes. However, on the single-molecule level, the fraction of one of the amplitudes spanned from 0 to unity for a collection of single-molecule detections. Further analysis by fluorescence correlation spectroscopy made on many molecules revealed a process that obeys a stretched exponential relaxation law. These facts, combined with previous evidence of the quenching effect of guanosine on rhodamines, indicate that the tetramethylrhodamine molecule senses conformational transitions as it associates and dissociates to a guanosine-rich area. Thus, our results reveal conformational transitions in a single molecule in solution under conditions that are relevant for biological processes.
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| 42. |
- Ellegren, H, et al.
(författare)
-
Sex ratio adjustment in relation to paternal attractiveness in a wild bird population
- 1996
-
Ingår i: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA. - : NATL ACAD SCIENCES. - 0027-8424. ; 93:21, s. 11723-11728
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- When the relative fitness of sons and daughters differs, sex-allocation theory predicts that it would be adaptive for individuals to adjust their investment in different sexes of offspring. Sex ratio adjustment by females in response to the sexual attract
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| 43. |
- Eriksson, Mats, 1966-, et al.
(författare)
-
Discovery of an algal mitochondrial carbonic anhydrase : molecular cloning and characterization of a low-CO2-induced polypeptide in Chlamydomonas reinhardtii
- 1996
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424 .- 1091-6490. ; 93:21, s. 12031-12034
-
Tidskriftsartikel (refereegranskat)abstract
- In green unicellular algae, several polypeptides are induced upon exposure to limiting CO2. We report here on the localization and characterization of one of these, a 22-kDa polypeptide in Chlamydomonas reinhardtii. This nuclear-encoded polypeptide is induced in the mitochondria by a lowering of the partial pressure of CO2 in the growth medium from 5% to air CO2 levels. Sequencing of two different cDNA clones coding for the polypeptide identified it as a 20.7-kDa beta-type carbonic anhydrase (CA; carbonate dehydratase, carbonate hydro-lyase, EC 4.2.1.1). The two clones differ in their nucleotide sequences but code for identical proteins, showing that this CA is encoded by at least two genes. Northern blot hybridization reveals that mRNA transcripts are only present in cells transferred to air CO2 levels. A comparison of the deduced amino acid sequence with those of other beta-CAs shows the largest degree of similarity with CA from the cyanobacterium Synechocystis (50% identity and 66% similarity). To our knowledge, this is the first identification and characterization of a mitochondrial CA from a photosynthetic organism.
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| 44. |
- ERIKSSON, P, et al.
(författare)
-
Allele-specific increase in basal transcription of the plasminogen-activator inhibitor 1 gene is associated with myocardial infarction
- 1995
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 92:6, s. 1851-1855
-
Tidskriftsartikel (refereegranskat)abstract
- Increased plasminogen-activator inhibitor 1 (PAI-1) activity is a common finding in patients with coronary heart disease. Here we provide evidence for an independent, etiological role of PAI-1 in myocardial infarction. The 4G allele of a recently described common 4/5-guanine-tract (4G/5G) polymorphism in the PAI-1 promoter is associated with higher plasma PAI-1 activity. The prevalence of the 4G allele is significantly higher in patients with myocardial infarction before the age of 45 than in population-based controls (allele frequencies of 0.63 vs. 0.53). Both alleles bind a transcriptional activator, whereas the 5G allele also binds a repressor protein to an overlapping binding site. In the absence of bound repressor, the basal level of PAI-1 transcription is increased.
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| 45. |
- ERIKSSON, S, et al.
(författare)
-
Alpha 1-antichymotrypsin regulates Alzheimer beta-amyloid peptide fibril formation
- 1995
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 92:6, s. 2313-2317
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Tidskriftsartikel (refereegranskat)abstract
- The major component of the cerebral plaques in Alzheimer disease is the beta-amyloid peptide, but serine proteinase inhibitors like alpha 1-antichymotrypsin (ACT) are also present. Their role in the pathogenesis of amyloid formation is unsettled. In addition to their function as proteinase inhibitors, serine proteinase inhibitors can interact with various hydrophobic compounds, a reaction accompanied by a transition from the stressed to the relaxed conformation. We report here on the ability of ACT to regulate the formation of beta-amyloid fibrils in vitro. In a molar ratio of 1:10 (ACT to beta-amyloid) ACT inhibits beta-amyloid fibril formation. Furthermore, ACT promotes rapid disaggregation of beta-amyloid fibrils when added in the same molar ratio to preformed beta-amyloid fibrils. These processes are accompanied by increased thermostability of ACT and loss of its biological activity, consistent with a conformational transition of ACT from the stressed to the relaxed state. The influence of ACT on beta-amyloid fibril formation may be an example of a hydrophobic interaction between the beta-amyloid peptide and the hydrophobic domain C terminal to the reactive center of ACT.
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| 46. |
- FAGERBERG, J, et al.
(författare)
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Human anti-idiotypic antibodies induced a humoral and cellular immune response against a colorectal carcinoma-associated antigen in patients
- 1995
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 92:11, s. 4773-4777
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Tidskriftsartikel (refereegranskat)abstract
- Induction of immunity against antigens expressed on tumor cells might prevent or delay recurrence of the disease. Six patients operated on for colorectal carcinoma were immunized with human monoclonal anti-idiotypic antibodies (h-Ab2) against the mouse 17-1A anti-colon carcinoma antibody, mimicking a nominal antigen (GA733-2). All patients developed a long-lasting T-cell immunity against the extracellular domain of GA733-2 (GA733-2E) (produced in a baculovirus system) and h-Ab2. This was shown in vitro by specific cell proliferation (DNA-synthesis) assay as well as by interleukin 2 and interferon gamma production and in vivo by the delayed-type hypersensitivity reaction. Five patients mounted a specific humoral response (IgG) against the tumor antigen GA733-2E (ELISA) and tumor cells expressing GA733-2. Epitope mapping using 23 overlapping peptides of GA733-2E revealed that the B-cell epitope was localized close to the N terminus of GA733-2. Binding of the antibodies to the tumor antigen and to one 18-aa peptide was inhibited by h-Ab2, indicating that the antibodies were able to bind to the antigen as well as to h-Ab2. The results suggest that our h-Ab2 might be able to induce an anti-tumor immunity which may control the growth of tumor cells in vivo.
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| 47. |
- FALK, PG, et al.
(författare)
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Expression of a human alpha-1,3/4-fucosyltransferase in the pit cell lineage of FVB/N mouse stomach results in production of Leb-containing glycoconjugates: a potential transgenic mouse model for studying Helicobacter pylori infection
- 1995
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 92:5, s. 1515-1519
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Tidskriftsartikel (refereegranskat)abstract
- Helicobacter pylori is a human pathogen associated with the development of gastric and duodenal ulcers and gastric adenocarcinoma. To test the hypothesis that the human Lewis(b) blood group antigen (Le(b)) functions as a receptor for the bacteria's adhesins and mediates its attachment to gastric pit and surface mucous cells, a human alpha-1,3/4-fucosyltransferase was expressed in these cell lineages in FVB/N transgenic mice. The fucosyltransferase directed production of the Leb epitope without any apparent effect on the proliferation and differentiation programs of this lineage. Moreover, clinical isolates of H. pylori bound to these cells in transgenic mice but not in their normal littermates. Binding was blocked by pretreatment of the bacteria with soluble Le(b). This mouse model could be useful for examining the molecular pathogenesis of diseases caused by H. pylori infection. Creating novel pathways for production of specific oligosaccharides in selected cell lineages of transgenic animals represents an approach for examining the role of complex carbohydrates in regulating cellular differentiation and host-microbe interactions.
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| 48. |
- Fridberger, Anders, 1966-, et al.
(författare)
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Acoustic overstimulation increases outer hair cell Ca2+ concentrations and causes dynamic contractions of the hearing organ
- 1998
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 95:12, s. 7127-7132
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Tidskriftsartikel (refereegranskat)abstract
- The dynamic responses of the hearing organ to acoustic overstimulation were investigated using the guinea pig isolated temporal bone preparation. The organ was loaded with the fluorescent Ca2+ indicator Fluo-3, and the cochlear electric responses to low-level tones were recorded through a microelectrode in the scala media. After overstimulation, the amplitude of the cochlear potentials decreased significantly. In some cases, rapid recovery was seen with the potentials returning to their initial amplitude. In 12 of 14 cases in which overstimulation gave a decrease in the cochlear responses, significant elevations of the cytoplasmic [Ca2+] in the outer hair cells were seen. [Ca2+] increases appeared immediately after terminating the overstimulation, with partial recovery taking place in the ensuing 30 min in some preparations. Such [Ca2+] changes were not seen in preparations that were stimulated at levels that did not cause an amplitude change in the cochlear potentials. The overstimulation also gave rise to a contraction, evident as a decrease of the width of the organ of Corti. The average contraction in 10 preparations was 9 microm (SE 2 microm). Partial or complete recovery was seen within 30-45 min after the overstimulation. The [Ca2+] changes and the contraction are likely to produce major functional alterations and consequently are suggested to be a factor contributing strongly to the loss of function seen after exposure to loud sounds.
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| 49. |
- Funakoshi, H, et al.
(författare)
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Targeted expression of a multifunctional chimeric neurotrophin in the lesioned sciatic nerve accelerates regeneration of sensory and motor axons
- 1998
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 95:9, s. 5269-5274
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Tidskriftsartikel (refereegranskat)abstract
- Peripheral nerve injury markedly regulates expression of neurotrophins and their receptors in the lesioned nerve. However, the role of endogenously produced neurotrophins in the process of nerve regeneration is unclear. Expression of a multifunctional neurotrophin, pan-neurotrophin-1 (PNT-1), was targeted to the peripheral nerves of transgenic mice by using a gene promoter that is specifically activated after nerve lesion but that is otherwise silent in all other tissues and during development. PNT-1 is a chimeric neurotrophin that combines the active sites of the neurotrophins nerve growth factor, brain-derived neurotrophic factor, and neurotrophin-3 and binds and activates all known neurotrophin receptors. In adult transgenic mice, PNT-1 was highly expressed in transected but not in intact sciatic nerve. Morphometric analyses at the electron microscopy level showed increased and accelerated recovery of axon diameter of myelinated fibers in crushed peripheral nerves of transgenic mice compared with wild type. Examination of nerve bundles in target tissues indicated accelerated reinnervation of foot pad dermis and flexor plantaris muscle in transgenic mice. Moreover, transected sensory and motor axons of transgenic mice showed faster and increased return of neurophysiological responses, suggesting an accelerated rate of axonal elongation. Importantly, transgenic mice also showed a markedly ameliorated loss of skeletal muscle weight, indicating functional regeneration of motor axons. Together, these data provide evidence, at both the anatomical and functional levels, that neurotrophins endogenously produced by the lesioned nerve are capable of significantly accelerating the regeneration of both sensory and motor axons after peripheral nerve damage. In addition, our results indicate that exogenous PNT-1 administration may be an effective therapeutic treatment of peripheral nerve injuries.
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| 50. |
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