| 1. |
- West, Jay B., et al.
(författare)
-
Comparison and evaluation of retrospective intermodality image registration techniques
- 1997
-
Ingår i: SPIE - The International Society for Optical Engineering. - : SPIE - International Society for Optical Engineering. ; , s. 332-347
-
Konferensbidrag (refereegranskat)abstract
- All retrospective image registration methods have attached to them some intrinsic estimate of registration error. However, this estimate of accuracy may not always be a good indicator of the distance between actual and estimated positions of targets within the cranial cavity. This paper describes a project whose principal goal is to use a prospective method based on fiducial markers as a ’gold standard’ to perform an objective, blinded evaluation of the accuracy of several retrospective image-to-image registration techniques. Image volumes of three modalities – CT, MR, and PET – were taken of patients undergoing neurosurgery at Vanderbilt University Medical Center. These volumes had all traces of the fiducial markers removed, and were provided to project collaborators outside Vanderbilt, who then performed retrospective registrations on the volumes, calculating transformations from CT to MR and/or from PET to MR, and communicated their transformations to Vanderbilt where the accuracy of each registration was evaluated. In this evaluation the accuracy is measured at multiple ’regions of interest,’ i.e. areas in the brain which would commonly be areas of neurological interest. A region is defined in the MR image and its centroid C is determined. Then the prospective registration is used to obtain the corresponding point C’ in CT or PET. To this point the retrospective registration is then applied, producing C’ in MR. Statistics are gathered on the target registration error (TRE), which is the disparity between the original point C and its corresponding point C’. A second goal of the project is to evaluate the importance of correcting geometrical distortion in MR images, by comparing the retrospective TRE in the rectified images, i.e., those which have had the distortion correction applied, with that of the same images before rectification. This paper presents preliminary results of this study along with a brief description of each registration technique and an estimate of both preparation and execution time needed to perform the registration.
|
|
| 2. |
- Andersson, Siv GE, et al.
(författare)
-
The genome sequence of Rickettsia prowazekii and the origin of mitochondria
- 1998
-
Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 396:6707, s. 133-140
-
Tidskriftsartikel (refereegranskat)abstract
- We describe here the complete genome sequence (1,111,523 base pairs) of the obligate intracellular parasite Rickettsia prowazekii, the causative agent of epidemic typhus. This genome contains 834 protein-coding genes. The functional profiles of these genes show similarities to those of mitochondrial genes: no genes required for anaerobic glycolysis are found in either R. prowazekii or mitochondrial genomes, but a complete set of genes encoding components of the tricarboxylic acid cycle and the respiratory-chain complex is found in R. prowazekii. In effect, ATP production in Rickettsia is the same as that in mitochondria. Many genes involved in the biosynthesis and regulation of biosynthesis of amino acids and nucleosides in free-living bacteria are absent from R. prowazekii and mitochondria. Such genes seem to have been replaced by homologues in the nuclear (host) genome. The R. prowazekii genome contains the highest proportion of non-coding DNA (24%) detected so far in a microbial genome. Such non-coding sequences may be degraded remnants of 'neutralized' genes that await elimination from the genome. Phylogenetic analyses indicate that R. prowazekii is more closely related to mitochondria than is any other microbe studied so far.
|
|
| 3. |
|
|
| 4. |
- Johansson, Hans-Olof, et al.
(författare)
-
Driving forces for phase separation and partitioning in aqueous two-phase systems
- 1998
-
Ingår i: Journal of Chromatography. B. - 1387-2273. ; 711:1-2, s. 3-17
-
Tidskriftsartikel (refereegranskat)abstract
- A set of simple analytical equations, derived from the Flory-Huggins theory, are used to identify the dominant driving forces for phase separation and solute (e.g., protein) partitioning, in the absence and presence of added electrolyte, in every general class of aqueous two-phase systems. The resulting model appears to capture the basic nature of two-phase systems and all trends observed experimentally. Case studies are used to identify fundamental differences in and the magnitudes of enthalpic and entropic contributions to partitioning in polymer-polymer (e.g., PEG-dextran), polymer-salt, and thermoseparating polymer-water (e.g., UCON-water) two-phase systems. The model therefore provides practitioners with a better understanding of partition systems, and industry with a simple, fundamental tool for selecting an appropriate two-phase system for a particular separation.
|
|
| 5. |
- Lemm, Julie A, et al.
(författare)
-
Template-dependent initiation of Sindbis virus RNA replication in vitro
- 1998
-
Ingår i: Journal of Virology. - 0022-538X .- 1098-5514. ; 72:8, s. 6546-6553
-
Tidskriftsartikel (refereegranskat)abstract
- Recent insights into the early events in Sindbis virus RNA replication suggest a requirement for either the P123 or P23 polyprotein, as well as mature nsP4, the RNA-dependent RNA polymerase, for initiation of minus-strand RNA synthesis. Based on this observation, we have succeeded in reconstituting an in vitro system for template-dependent initiation of SIN RNA replication. Extracts were isolated from cells infected with vaccinia virus recombinants expressing various SIN proteins and assayed by the addition of exogenous template RNAs. Extracts from cells expressing P123C>S, a protease-defective P123 polyprotein, and nsP4 synthesized a genome-length minus-sense RNA product. Replicase activity was dependent upon addition of exogenous RNA and was specific for alphavirus plus-strand RNA templates. RNA synthesis was also obtained by coexpression of nsP1, P23C>S, and nsP4. However, extracts from cells expressing nsP4 and P123, a cleavage-competent P123 polyprotein, had much less replicase activity. In addition, a P123 polyprotein containing a mutation in the nsP2 protease which increased the efficiency of processing exhibited very little, if any, replicase activity. These results provide further evidence that processing of the polyprotein inactivates the minus-strand initiation complex. Finally, RNA synthesis was detected when soluble nsP4 was added to a membrane fraction containing P123C>S, thus providing a functional assay for purification of the nsP4 RNA polymerase.
|
|
| 6. |
|
|
| 7. |
- Zetterström, Maria, 1970-
(författare)
-
Role of interleukin-1 in fever and inflammation
- 1998
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The proinflammatory cytokines interleukin (IL) -1α, IL-1β and IL-6 are key mediators in the host's response to injury and infection. One of the systemic responses elicited by these proinflammatory cytokines, when injected peripherally or centrally, is fever. Thus, these proteins may act as endogenous pyrogens.We have shown that for a functional IL-1 mediated febrile response in vivo, both IL-1 receptor type I (IL-1RI) and IL-1 receptor accessory protein (IL-1RAcP) are necessary components, as knockout (KO) mice, lacking either IL-1RI or IL-1RAcP proteins, do not mount febrile responses to rrIL-1 (25-50 μg/kg, i.p.) injections, whereas they responded with fever when challenged by LPS (50 μg/kg, i.p.). These results suggest that IL-1 induces fever via signalling through a receptor complex, consisting of both IL-1RI and IL-1RAcP. We have also shown that IL-1β cannot induce NFκB translocation to the nucleus in primary astrocyte cultures derived from IL-1RAcP KO mice, suggesting a signalling role for this protein in mouse astrocytes.When the regulation of interleukin-1β converting enzyme (ICE, caspase-1) was studied in rat after peripheral LPS treatment (2 mg/kg, i.p.), elevations were seen, on both mRNA levels and enzyme activity in the pituitary, whereas in adrenal glands, an increase of mRNA levels did not coincide with upregulated enzyme activity. However, LPS was further shown to differentially regulate ICE isoforms, some of which are supposed to act as endogenous inhibitors of ICE activity. Thus, ICE activity seems to be tightly controlled on a transcriptional level, where regulation of ICE isoforms play an important role, as well as at the post transcriptional level.We have also shown that treatment with a neurotoxic fragment of β-amyloid, βA(25-35), induces a reactive phenotype of rat primary astrocyte cultures. The progression of this reactive phenotype was shown to coincide with elevated mRNA levels of IL-1α and IL-6. In addition, βA(25-35) treatment of primary astrocyte cultures derived from IL-1RI KO mice, induced a hypersensitive IL-1α response and a decreased IL-6 response. IL-1a and IL-6 are therefore proposed to be important molecules for development of reactive gliosis, and we also propose that signalling via IL-1RI is necessary for a full-scale induction of IL-6 mRNA.
|
|
