| 21. |
- Beier, Frank, et al.
(författare)
-
Localization of silencer and enhancer elements in the human type X collagen gene.
- 1997
-
Ingår i: Journal of Cellular Biochemistry. - : John Wiley & Sons. - 0730-2312 .- 1097-4644. ; 66:2, s. 210-218
-
Tidskriftsartikel (refereegranskat)abstract
- Collagen type X is a short, network-forming collagen expressed temporally and spatially tightly controlled in hypertrophic chondrocytes during endochondral ossification. Studies on chicken chondrocytes indicate that the regulation of type X collagen gene expression is regulated at the transcriptional level. In this study, we have analyzed the regulatory elements of the human type X collagen (Col10a1) by reporter gene constructs and transient transfections in chondrogenic and nonchondrogenic cells. Four different promoter fragments covering up to 2,864 bp of 5'-flanking sequences, either including or lacking the first intron, were linked to luciferase reporter gene and transfected into 3T3 fibroblasts, HT1080 fibrosarcoma cells, prehypertrophic chondrocytes from the resting zone, hypertrophic chondrocytes, and chondrogenic cell lines. The results indicated the presence of three regulatory elements in the human Col10a1 gene besides the proximal promoter. First, a negative regulatory element located between 2.4 and 2.8 kb upstream of the transcription initiation site was active in all nonchondrogenic cells and in prehypertrophic chondrocytes. Second, a positive, but also non-tissue-specific positive regulatory element was present in the first intron. Third, a cell-type-specific enhancer element active only in hypertrophic chondrocytes was located between -2.4 and -0.9 kb confirming a previous report by Thomas et al. [(1995): Gene 160:291-296]. The enhancing effect, however, was observed only when calcium phosphate was either used for transfection or included in the culture medium after lipofection. These findings demonstrate that the rigid control of human Col10a1 gene expression is achieved by both positive and negative regulatory elements in the gene and provide the basis for the identification of factors binding to those elements.
|
|
| 22. |
|
|
| 23. |
- Beier, Frank, et al.
(författare)
-
Variability in the upstream promoter and intron sequences of the human, mouse and chick type X collagen genes.
- 1996
-
Ingår i: Matrix Biology. - : Elsevier. - 0945-053X .- 1569-1802. ; 15:6, s. 415-422
-
Tidskriftsartikel (refereegranskat)abstract
- The type X collagen gene is specifically expressed in hypertrophic chondrocytes during endochondral ossification. Transcription of the type X collagen gene by these differentiated cells is turned on at the same time as transcription of several other cartilage specific genes is switched off and before mineralization of the matrix begins. Analysis of type X collagen promoters for regulatory regions in different cell culture systems and in transgenic mice has given contradictory results suggesting major differences among species. To approach this problem, we have determined the nucleotide sequences of the two introns and upstream promoter sequences of the human and mouse type X collagen genes and compared them with those of bovine and chick. Within the promoter regions, we found three boxes of homology which are nearly continuous in the human gene but have interruptions in the murine gene. One of these interruptions was identified as a complex 1.9 kb repetitive element with homology to LINE, B1, B2 and long terminal repeat sequences. Regulatory elements of the human type X collagen gene are located upstream of the region where the repetitive element is inserted in the mouse gene, making it likely that the repetitive element is inserted between the coding region and regulatory sequences of the murine gene without interfering with its expression pattern. We also compared the sequences of the introns of both genes and found strong conservation. Comparisons of the mammalian sequences with promoter and first intron sequences of the chicken type X collagen gene revealed that only the proximal 120 nucleotides of the promoter were conserved, whereas all other sequences displayed no obvious homology to the murine and human sequences.
|
|
| 24. |
- Belting, Mattias
(författare)
-
On the binding of growth-promoting polyamines to proteoglycans: Implications for growth-regulation and polycation-mediated gene transfer
- 1999
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Initial investigations were directed at studying the interaction between polyamines and various glycosaminoglycans (GAGs). The polyamine spermine displayed binding to dermatan sulphate (DS) and heparan sulphate (HS) with similar (Kd, 3.9 x 10-4 M) and higher (Kd, 0.37 x 10-6 M) affinity, respectively, than to DNA. Antiproliferative spermine-binding DS fragments (tetra- to decasaccharides), and affinity-subfractionated HS chains were obtained by enzyme protection and affinity chromatography experiments, respectively. A clear correlation between high spermine-affinity and strong growth-inhibition was observed. Subsequent studies addressed the possible functional roles of the interaction. Pre-treatment of cells with GAG lyases, chlorate, or xylosides, all of which reduce the amount of cell-associated proteoglycans (PGs), resulted in diminished polyamine uptake. Mutant cells, deficient in PG, exhibited i) reduced polyamine uptake, ii) increased sensitivity to inhibition of polyamine biosynthesis, and iii) decreased growth-restoration by extracellular polyamines, as compared with wild-type cells. Moreover, one of the mutants exhibited the wild-type phenotype upon ectopic expression of the defective gene. The fact that several, widely used non-viral gene delivery vehicles, i.e. cationic lipids (CLs), make use of the physiological interaction between DNA and the polyamines, prompted us to investigate the possible role for PGs in CL-mediated gene transfer. Secreted PGs were shown to compete with DNA plasmid for binding to CL, leading to exchange of DNA for PG, intracellular accumulation of CL-PG complexes, nuclear deposition of GAG, and, consequently, a 100- 1000-fold decrease in reporter gene expression. In contrast, cell-associated PGs were shown to serve a protective role against CL cytotoxicity, thus allowing optimal transfection efficiency. In conclusion, the results suggest a role for PGs in 1) polyamine uptake, 2) polyamine-dependent cell growth, and 3) non-viral gene transfer.
|
|
| 25. |
|
|
| 26. |
|
|
| 27. |
- Berggård, Tord, et al.
(författare)
-
Alpha1-microglobulin is found both in blood and in most tissues
- 1998
-
Ingår i: The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society. - : SAGE Publications. - 0022-1554. ; 46:8, s. 94-887
-
Tidskriftsartikel (refereegranskat)abstract
- In this study we demonstrate that, in addition to blood, alpha1-microglobulin (alpha1m) is present in most tissues, including liver, heart, eye, kidney, lung, pancreas, and skeletal muscle. Western blotting of perfused and homogenized rat tissue supernatants revealed alpha1m in its free, monomeric form and in high molecular weight forms, corresponding to the complexes fibronectin-alpha1m and alpha1-inhibitor-3-alpha1m, which have previously been identified in plasma. The liver also contained a series of alpha1m isoforms with apparent molecular masses between 40 and 50 kD. These bands did not react with anti-inter-alpha-inhibitor antibodies, indicating that they do not represent the alpha1m-bikunin precursor protein. Similarly, the heart contained a 45-kD alpha1m band and the kidney a 50-kD alpha1m band. None of these alpha1m isoforms was present in plasma. Immunohistochemical analysis of human tissue demonstrated granular intracellular labeling of alpha1m in hepatocytes and in the proximal epithelial cells of the kidney. In addition, alpha1m immunoreactivity was detected in the interstitial connective tissue of heart and lung and in the adventitia of blood vessels as well as on cell surfaces of cardiocytes. alpha1m mRNA was found in the liver and pancreas by polymerase chain reaction, suggesting that the protein found in other tissues is transported via the bloodstream from the production sites in liver and pancreas. The results of this study indicate that in addition to its role in plasma, alpha1m may have important functions in the interstitium of several tissues. (J Histochem Cytochem 46:887-893, 1998)
|
|
| 28. |
- Berglund, Jan, et al.
(författare)
-
Rapid increase in volume of the remnant after hemithyroidectomy does not correlate with serum concentration of thyroid stimulating hormone
- 1998
-
Ingår i: European Journal of Surgery. - : Oxford University Press (OUP). - 1102-4151 .- 1741-9271. ; 164:4, s. 257-262
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To study the effect of postoperative thyroxine on the volume of the thyroid remnant after lobectomy for benign nontoxic goitre. DESIGN: Prospective, randomised study. SETTING: University hospital, Sweden. SUBJECTS: 50 consecutive patients who underwent lobectomy for benign non-toxic goitre. INTERVENTIONS: Patients were randomised postoperatively to take thyroxine 0.1 mg or placebo daily. MAIN OUTCOME MEASURES: The median volume of the remaining thyroid lobe measured by ultrasound. Serum concentrations of thyroxine, triiodothyronine (T3) and thyroid stimulating hormone (TSH) were measured preoperatively and 1, 3, 6, 12 months postoperatively. RESULTS: The median volume of the remaining lobe had increased significantly compared with preoperatively by 1 month postoperatively by 30% in the thyroxine group and 25% in the placebo group (p < 0.01). The difference between the groups was not significant. After the first month the volume did not change significantly. In the thyroxine group, the TSH concentration was unchanged and the thyroxine concentration increased significantly throughout the study. In the placebo group there was a significant increase in TSH concentration and a significant decrease in that of thyroxine at all follow-up examinations. CONCLUSIONS: There is a significant increase in the volume of the remaining thyroid 1 month after lobectomy that persisted throughout the first year. Thyroxine given in a dose that kept the serum TSH concentration at the same level as preoperatively did not seem to influence volume changes; consequently we consider that these are caused by factors other than TSH.
|
|
| 29. |
- Berts, Alf, et al.
(författare)
-
Oscillatory Ca2+ signaling in somatostatin-producing cells from the human pancreas
- 1997
-
Ingår i: Metabolism. - 0026-0495 .- 1532-8600. ; 46:4, s. 366-369
-
Tidskriftsartikel (refereegranskat)abstract
- Oscillatory Ca2+ signaling was studied in human somatostatin-releasing pancreatic δ cells identified by immunostaining. A ratiometric fura-2 technique was used for measuring cytoplasmic concentrations of Ca2+ and Sr2+ in δ cells exposed to the respective cation. Rhythmic activity in terms of slow (frequency, 0.1 to 0.4 per minute) oscillations from close to the basal level was seen in the presence of 3 to 20 mmol/L glucose during superfusion with medium containing 2.6 to 5 mmol/L Ca2+ or 5 mmol/L Sr2. These oscillations could be transformed into a sustained increase by decreasing extracellular Ca2+ or adding 1 mmol/L tolbutamide or 20 nmol/L glucagon. Addition of glucagon to a medium containing 20 mmol/L glucose resulted in the generation of short (< 30 seconds) transients, which disappeared upon exposure to 100 nmol/L of the intracellular Ca2+-adenosine triphosphatase (ATPase) inhibitor thapsigargin. When analyzing small aggregates of islet cells, it became evident that oscillatory activity in δ cells can be synchronous with that in adjacent non—δ cells. It is concluded that secretion of pancreatic somatostatin in man involves Ca2+ signaling similar to that regulating the pulsatile release of insulin.
|
|
| 30. |
- Billker, Oliver, et al.
(författare)
-
Identification of xanthurenic acid as the putative inducer of malaria development in the mosquito
- 1998
-
Ingår i: Nature. - : Macmillan Publishers Ltd.. - 0028-0836 .- 1476-4687. ; 392:6673, s. 289-292
-
Tidskriftsartikel (refereegranskat)abstract
- Malaria is transmitted from vertebrate host to mosquito vector by mature sexual blood-living stages called gametocytes. Within seconds of ingestion into the mosquito bloodmeal, gametocytes undergo gametogenesis. Induction requires the simultaneous exposure to at least two stimuli in vitro: a drop in bloodmeal temperature to 5 degrees C below that of the vertebrate host, and a rise in pH from 7.4 to 8.0-8.2. In vivo the mosquito bloodmeal has a pH of between 7.5 and 7.6. It is thought that in vivo the second inducer is an unknown mosquito-derived gametocyte-activating factor. Here we show that this factor is xanthurenic acid. We also show that low concentrations of xanthurenic acid can act together with pH to induce gametogenesis in vitro. Structurally related compounds are at least ninefold less effective at inducing gametogenesis in vitro. In Drosophila mutants with lesions in the kynurenine pathway of tryptophan metabolism (of which xanthurenic acid is a side product), no alternative active compound was detected in crude insect homogenates. These data could form the basis of the rational development of new methods of interrupting the transmission of malaria using drugs or new refractory mosquito genotypes to block parasite gametogenesis.
|
|
