Search PubMed⌕ Search

Biomedical subjects

S J Davis

Publications and source records attributed to S J Davis.

At least 91 records · Page 5Linked to original sources
PubMed1991

Autonomous roles for the cytoplasmic domains of the CD2 and CD4 T cell surface antigens.

CD2 and CD4 are single chain transmembrane T cell surface molecules that are involved in signal transduction. Chimaeric constructs from rat CD2 and CD4 antigens were expressed in the Jurkat human T cell line to examine the role of extracellular, transmembrane and cytoplasmic domains in mediating functions controlled by CD2 and CD4. The results show that the large rise in concentration of cytoplasmic free Ca2+ mediated via CD2 crosslinking is controlled by the cytoplasmic domain and does not require the CD2 transmembrane and extracellular domains. Similarly the CD4 cytoplasmic domain alone was shown to encode the specificity for binding to the p56lck tyrosine kinase and to control down-modulation of CD4 after treatment with phorbol ester. Evidence was obtained that down-modulation of CD4 occurs when p56lck dissociates from the cytoplasmic domain due to phosphorylation of Ser 405.

Amino Acid Sequence↗
PubMed1991

Comparison of enzyme immunoassay and fluorescence polarization immunoassay as techniques for measuring anticonvulsant drugs on the same analytical instrument.

We have applied kits for enzyme immunoassay and fluorescence polarization immunoassay of anticonvulsant drugs to the same centrifugal analyser. There was a good correlation between the two techniques for the assay of phenytoin, carbamazepine, and phenobarbitone. Within- and between-batch reproducibility was also comparable but only the fluorescence polarization system allowed the use of stored calibration curves. The ability to use stored curves may be particularly advantageous to laboratories required to run a large number of stat assays or who are handling low workloads of particular analytes.

Carbamazepine↗
PubMed1991

Marked cerebrospinal fluid void: indicator of successful shunt in patients with suspected normal-pressure hydrocephalus.

The authors blindly reviewed the charts of 20 patients with normal-pressure hydrocephalus (a disease of unknown cause characterized radiologically as chronic communicating hydrocephalus and clinically by gait apraxia, dementia, and incontinence) who had undergone creation of a ventriculoperitoneal shunt. The initial clinical response to surgery was graded excellent, good, fair, or poor; 5-year follow-up was available in 55% of cases. The magnetic resonance (MR) images obtained in these patients were also blindly reviewed for the magnitude of cerebrospinal fluid (CSF) flow void (graded on the basis of extent rather than degree of signal loss) in the cerebral aqueduct. A significant (P less than .003) correlation existed between good or excellent response to surgery and an increased CSF flow void. The presence of associated deep white matter infarction on MR images did not correlate with a poor response to surgery. On the basis of these findings, it is suggested that patients who fulfill the clinical criteria of NPH and have an increased CSF flow void undergo creation of a shunt.

Aged↗
PubMed1991

Cervical spine hyperextension injuries: MR findings.

Cervical hyperextension injuries are common and often show minimal radiographic abnormalities, even with severe or unstable lesions. Fourteen patients, nine with acceleration hyperextension "whiplash" injuries and five injured by direct frontal head trauma, underwent magnetic resonance (MR) imaging within 4 months of injury. Five of seven patients with anterior spinal column injuries showed characteristic separation of the disk from the vertebral end plate, lesions still evident as late as 9 months after injury. The demonstration of this type of lesion and its delayed resolution may have prognostic and surgical implications. These lesions, anterior longitudinal ligament injuries, anterior annular tears, and occult anterior vertebral end-plate fractures usually occurred at multiple levels except when preexistent degenerative disk narrowing reduced spine mobility. Seven patients had acute cervical disk herniations causing cord impingement. Radiographically occult injuries are well demonstrated with MR imaging, and findings correspond to previously described surgical and anatomical pathologic conditions.

Adult↗
PubMed1991

Effect of arm rotation on MR imaging of the rotator cuff.

The effect of humeral rotation on the appearance of the rotator cuff tendon in oblique coronal magnetic resonance images was evaluated in 70 such images. Internal rotation produced overlap of the supraspinatus and infraspinatus tendons with soft-tissue interposition or apparent discontinuity of the tendon in 22 cases, including 14 of 15 shoulders positioned in the first 30 degrees between extreme internal and external rotation. Imaging in internal rotation makes assessment of the tendon difficult and should be avoided.

Humans↗
PubMed1991

Better MSP (Medicare secondary payer) process may boost payments.

Because the Federal government estimates large overpayments by Medicare, changes in the Medicare Secondary Payer (MSP) program may play a significant role in future Medicare budget cuts. A major contributor to MSP problems is providers' failure to adequately collect coverage information from Medicare beneficiaries. Along with data sharing between Federal agencies to help identify responsibility for Medicare claims, providers likely will face more pressure to properly collect Medicare beneficiary information. Because of MSP program payment structure, improving billing offices' procedures for collecting Medicare beneficiary information ultimately may increase providers' overall payments.

Admitting Department, Hospital↗
PubMed1990

High level expression in Chinese hamster ovary cells of soluble forms of CD4 T lymphocyte glycoprotein including glycosylation variants.

The CD4 cell surface antigen is of interest as a marker of T lymphocytes that recognize foreign antigens in the context of MHC Class II antigen, as a receptor for the human immunodeficiency virus (HIV) and as a member of the immunoglobulin superfamily (IgSF) with four Ig-like domains present in the extracellular domain. In order to produce large amounts of soluble CD4 for x-ray crystallography and other molecular studies, a recently developed expression system based on selection via glutamine synthetase was used. Expression was attempted for rat CD4 corresponding to the full extracellular sequence (sCD4; domains 1-4), the NH2-terminal half (domains 1 and 2) and the first domain alone. Stable transfected Chinese hamster ovary cell lines were obtained that expressed sCD4 and sCD4 (half) at typical maximal levels in spent tissue culture supernatant of greater than 80 and 25 mg/liter, respectively. Domain 1 alone was not expressed and introduction of a N-linked glycosylation site did not facilitate expression. The role of glycosylation in the expression of sCD4 was investigated by mutagenesis of the constructs to remove each of the two N-linked glycosylation sites in turn and both together. All three forms were expressed at 60-120 mg/liter. The sCD4 (half) was not expressed after deletion of its N-linked site. The disulfide bonds of sCD4 were determined to be within domains 1, 2, and 4 and isolation of glycopeptides showed that both N-linked sites were glycosylated. Analysis of the hydrodynamic properties of sCD4 suggested that the molecule adopted an extended conformation in solution rather than folding to form a compact structure like an Fab. The possibility of dimerisation of CD4 was investigated but sCD4 dimers were not seen at an affinity cut-off of about 4 x 10(5) M-1.

Amino Acid Sequence↗
PubMed1990

Crystallization of a soluble form of the rat T-cell surface glycoprotein CD4 complexed with Fab from the W3/25 monoclonal antibody.

The structure of the T-lymphocyte cell surface glycoprotein CD4 is of considerable biological and medical interest. Recombinant rat CD4 expressed in soluble form in mammalian cells and complexed with W3/25 monoclonal Fab fragments formed crystals that diffract to 3.5 A and have the orthorhombic space group P2(1)2(1)2 or P2(1)2(1)2(1). The unit cell has dimensions a = 317 A, b = 161 A and c = 41.8 A and the asymmetric unit consists of two CD4:Fab complexes. These crystals are of suitable quality for X-ray diffraction analysis.

Animals↗
PubMed1990

Distinctive echogenic lymphadenopathy in Whipples disease.

A case of Whipples disease presenting with polyarthropathy and weight loss is presented. Ultrasound revealed unusual distinctive diffusely echogenic retroperitoneal lymphadenopathy which resolved after treatment. These appearances, particularly in a young male, support this diagnosis.

Adult↗
PubMed1990

Characteristic appearances of colonic lipomas on barium enema: a guide to conservative management.

The double contrast barium enema appearances of seven colonic lipomas are reviewed. These lesions have submucosal features: intact mucosa, sharp margination and obtuse angles between the lesion and the adjacent colonic wall, as well as features characteristic of lipomas: pliability and shape change, broad pedicles and spherical appearances en face. They can be differentiated from the more significant colonic adenomas and then CT scanned to establish a histological diagnosis. The need for colonoscopic or surgical excision of these predominantly asymptomatic lesions occurring in elderly patients can be considerably reduced.

Aged↗
PubMed1990

The 1990-91 job outlook in brief.

To learn how employment in 250 occupations is expected to change between 1988 and 2000, all you have to do is look at this article.

Employment↗
PubMed1988

Oligosaccharide heterogeneity of glycoproteins sulfated during the vegetative growth of Dictyostelium discoideum.

Macromolecules are sulfated during the vegetative growth of Dictyostelium discoideum. A characterisation of the structures of sulfated oligosaccharides associated with these macromolecules indicates that the oligosaccharides are heterogeneous. Endoglycosidase and pronase digestion were used with gel-filtration chromatography to obtain two different oligosaccharide fractions and a glycopeptide fraction; these were further characterised by ion-exchange and lectin-affinity chromatography and by acid hydrolysis. The data indicate that up to 43% of the sulfate is associated with typical N-linked oligosaccharides, that up to 5% is associated with N-linked oligosaccharides that are either very large or extremely highly charged, and that the remaining sulfate is associated with oligosaccharides non-N-linked to protein. Each fraction was also shown to be heterogeneous at most other structural levels. Electrophoretic analyses following the endoglycosidase and pronase treatments indicated that all of the macromolecules are glycoproteins and suggested further that at least two of the oligosaccharide fractions are located on different groups of glycoproteins.

Chromatography, Affinity↗
PubMed1988

An immunological assessment of lysosomal enzymes and other macromolecules sulfated during vegetative growth of Dictyostelium discoideum.

Western blotting and immunoprecipitation data indicated that lysosomal enzymes represent a subset of the sulfated macromolecules present in vegetative Dictyostelium discoideum amoebae and account for less than 2.5% of the total sulfate incorporated during vegetative growth. These data suggest that the majority of the highly sulfated macromolecules of vegetative D. discoideum amoebae are not related to the lysosomal enzymes.

Acetylglucosaminidase↗
PubMed1988

Expression of class I and II major histocompatibility complex antigens in Wilms' tumour and normal developing human kidney.

The Wilms' tumour is a solid childhood tumour of the kidney, consisting of blastema, tubules and mesenchyme. Embryonic tumours, such as Wilms', may arise as a result of a developmental disturbance in differentiation. The expression of class I and II major histocompatibility complex (MHC) antigens was investigated on 6 Wilms' tumours and related to that in the developing human kidney in this immunohistological study, using a panel of monoclonal antibodies. The Wilms' tumour blastemal cells were class I MHC antigen negative, but differentiated structures were positive. Class II MHC antigens were not observed in Wilms' tumours. In the developing human kidney class I MHC antigen expression was observed on glomeruli from 8 weeks and on tubules from 13 weeks gestational age. Class II MHC antigen expression was observed on glomeruli from 11 weeks and on tubules from 13 weeks gestation. These results suggest that the blastemal cells within the Wilms' tumour may reflect an early stage of development with respect to the expression of MHC antigens.

Adult↗