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Biomedical subjects

A Lewis

Publications and source records attributed to A Lewis.

At least 199 records · Page 11Linked to original sources
PubMed1986

Phosphorylation of the human interleukin-2 receptor and a synthetic peptide identical to its C-terminal, cytoplasmic domain.

The recombinant human interleukin-2 (IL-2) receptor was expressed in mouse mammary epithelial cells following the transfection of these cells with an expression vector containing the human IL-2 receptor cDNA. The recombinant IL-2 receptor in these cells was rapidly phosphorylated in response to phorbol myristate acetate (PMA), but its phosphorylation could not be detected in the absence of PMA or upon addition of human IL-2. The C-terminal, cytoplasmic peptide domain of the IL-2 receptor, Gln-Arg-Arg-Gln-Arg-Lys-Ser-Arg-Arg-Thr-Ile, was synthesized and used as a substrate for protein kinase C. The Km for phosphorylation of the peptide by protein kinase C was 23 microM. The stoichiometry of phosphorylation was 1 mol of phosphate/mol of peptide and serine was the predominant amino acid phosphorylated. Because this peptide was a good substrate for protein kinase C in vitro, it was possible that the same serine (serine 247) was also phosphorylated in the receptor in the cell. The IL-2 receptor gene in the expression vector was therefore altered by site-directed mutagenesis to code for an IL-2 receptor containing an alanine in the place of serine 247. The IL-2 receptor expressed by these cells was not phosphorylated in the presence of PMA. These data suggest that protein kinase C, in response to PMA, phosphorylates the C-terminal serine residue (serine 247) in the human IL-2 receptor.

Amino Acid Sequence↗
PubMed1986

High level stable expression of human interleukin-2 receptors in mouse cells generates only low affinity interleukin-2 binding sites.

A bovine papilloma virus-derived vector was used to direct the high level expression in mouse C127 cells of three different cDNAs encoding the human interleukin-2 receptor. These were: the previously described cDNA clone isolated from the T-cell lymphoma, HUT-102; a cDNA clone isolated from mitogen-activated, normal peripheral blood T cells; and an altered version of the HUT-102 receptor in which Ser247, believed to be the site of protein kinase C-mediated phosphorylation, has been changed to an Ala residue. Fluorescence-activated cell-sorting using a monoclonal antibody directed against the human IL-2 receptor was used to derive stable lines of C127 cells expressing from 2-6 X 10(6) IL-2 binding sites per cell. However, all of these receptors bound IL-2 with low affinity.

Amino Acid Sequence↗
PubMed1986

Increasing kidney transplantation in Britain: the importance of donor cards, public opinion and medical practice.

The Department of Health and Social Security has recently spent over three-quarters of a million pounds advertising the merits of kidney donor cards. The advertising campaign stresses that carrying signed cards requesting the removal of kidneys and other organs after death both increases the number of kidneys available and increases the number of kidney transplants that actually take place. This paper examines the relative success of the kidney donor card campaign in Britain and the nature of the relationship between a more widespread distribution of donor cards and the frequency of kidney transplantation. This is done in two main ways: Through a review of the evidence detailing public support expressed in the media and from social surveys (including original empirical work conducted at Bath University). By an analysis of previously unpublished statistical evidence made available by the Department of Health and Social Security. The paper concludes that the battle for public sympathy towards kidney donation has largely been won and the kidney donor card campaign has been a success. However these success perhaps deflect attention away from more important issues in the transplant equation, as the link between card carrying and increased transplantation is neither direct nor simple.

Advertising↗
PubMed1986

The differential diagnosis of Alzheimer's disease: conceptual and methodological issues.

The study of Alzheimer's disease is hampered by insufficient knowledge of its cause. It can best be described as a syndrome whose clinical and pathological features, and their associations over time, need to be more carefully examined. Issues which impede our understanding of this syndrome include the lack of: a singular "gold standard" for its identification; longitudinal studies with appropriate comparison groups and neuropathological follow-up; and standardized multifaceted clinical assessment procedures. Our awareness of the significance of these issues has led us to undertake a large-scale prospective, longitudinal investigation of 399 dementing and normal individuals at Sunnybrook Medical Centre. As a result of problems identified, it is proposed that research efforts across various Canadian centres be coordinated to best utilize available resources and expertise.

Alzheimer Disease↗
PubMed1985

Vanadate, tungstate and molybdate activate rod outer segment phosphodiesterase in the dark.

Anionic activation of rod outer segment phosphodiesterase by vanadate, molybdate and tungstate is demonstrated. Comparisons are made to adenylate cyclase, which is known to be activated by vanadate and molybdate but not by tungstate. In view of the differences in anionic activation between these two important enzymatic regulators of intracellular cyclic nucleotide metabolism, it is possible that tungstate can be used as a selective probe for the effects of phosphodiesterase activity in photoreceptors and other cells. The known electrophysiological stimulation of Limulus photoreceptors by these anions is also interpreted in light of our results. If anionic production of quantum bumps in Limulus photoreceptors is mediated by changes in cyclic nucleotides, then the electrophysiological response of Limulus photoreceptors to tungstate may indicate a role for phosphodiesterase rather than adenylate cyclase in mediating light-induced cyclic nucleotide alterations in this cell.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1985

Structure of the Epstein-Barr virus nuclear antigen as probed with monoclonal antibodies.

Five hybridoma cell lines secreting antibodies directed against an Epstein-Barr virus (EBV) nuclear antigen (BamHI K antigen) have been isolated. All five antibodies detect this antigen in a variety of EBV-positive lymphoblastoid cell lines. The reaction of these antibodies with several mutant forms of this protein has allowed the antibody binding site(s) to be predicted.

Animals↗
PubMed1985

Monoclonal antibodies prepared against the major Drosophila nuclear Matrix-pore complex-lamina glycoprotein bind specifically to the nuclear envelope in situ.

A high molecular weight glycoprotein found associated with a nuclear matrix-pore complex-lamina (NMPCL) preparation obtained from Drosophila melanogaster embryos has been shown by in vitro analyses to be largely confined to this subcellular fraction. In contrast with several of the NMPCL proteins, this glycoprotein remains completely insoluble after treatment with 5 M urea. It has, therefore, been possible to separate the glycoprotein from other NMPCL components by differential urea extraction. The glycoprotein in the 5 M urea-extracted pellet has been solubilized by boiling in sodium dodecyl sulfate and purified to near-homogeneity by sequential steps of chromatography on hydroxylapatite and Sephacryl S-300 (both run in the presence of 0.1% sodium dodecyl sulfate), followed by affinity chromatography on lentil lectin-Sepharose. Over 30 hybridoma cell lines producing antibodies against this glycoprotein have been obtained. Monoclonality has been established for two of these lines (designated AGP-26 and AGP-78), and the antibodies they secrete have been further characterized. Western blot analysis has shown both antibodies to be monospecific (with respect to other Drosophila embryo polypeptides) for the major NMPCL glycoprotein; in addition, antibody AGP-78 has been shown to be weakly cross-reactive with glycoproteins of similar or identical molecular weight found associated with isolated nuclear fractions obtained from Xenopus oocytes, as well as chicken, opossum, and rat livers. Finally, both antibodies AGP-26 and AGP-78 react exclusively with the Drosophila nuclear periphery (nuclear envelope) in situ as demonstrated by indirect immunofluorescence analysis of larval cryosections. Based on these results as well as upon those of biochemical studies reported previously (Berrios, M., Filson, A. J., Blobel, G, and Fisher, P. A. (1983) J. Biol. Chem. 258, 13384-13390), we conclude that the major Drosophila NMPCL glycoprotein is the specific homolog of the high molecular weight glycoprotein recently shown using immunoelectron microscopy to be a distinct component of the rat liver nuclear pore complex (Gerace, L., Ottaviano, Y., and Kondor-Koch, C. (1982) J. Cell Biol. 95, 826-837).

Animals↗
PubMed1985

Fluoride hypersensitivity in mains tap water demonstrated by skin potential changes in guinea-pigs.

Changes in skin electric potential following immune challenge provide a sensitive measure of the intensity of the allergic challenge. In guinea-pigs sensitised to Sodium Fluoride, Fluoridated Mains Tap Water, or Ovalbumen with Sodium Fluoride, and then challenged with one part in one million Sodium Fluoride, significant allergic responses were produced. Ovalbumen alone caused an allergic response only after a second challenge. Purified Water did not result in any immune response. It is concluded that Fluoridated Mains Tap Water is capable of causing an allergic response similar to that produced by Sodium Fluoride alone, and that Ovalbumen potentiates the immune response to Sodium Fluoride.

Animals↗
PubMed1985

Prosthetic materials and muscle flaps in the repair of extensive diaphragmatic defects: an experimental study.

Relative merits of three methods of diaphragmatic hernia repair were evaluated in growing animals. Twenty-five puppies underwent laparotomy. In four controls, the left hemidiaphragm was incised and sutured primarily. In the remaining dogs, it was partially resected sparing the phrenic nerve. The defects were repaired in six with silastic sheeting, in eight with polytetrafluoroethylene (PTFE; trademark, Gore-Tex), and in seven with a thoracoabdominal muscle flap. Dogs were killed at 1, 4, and 7 months for gross and microscopic evaluation of the repair. Diaphragmatic function was evaluated by inspiratory force against a closed airway and by selective phrenic nerve stimulation (PNS). Serial fluoroscopy was used to evaluate diaphragmatic motion. Grossly the diaphragms in all groups showed compensatory growth. Microscopically the silastic was encapsulated without adherence, while PTFE showed tissue ingrowth. Maximal inspiratory force was equivalent in all groups but selective PNS revealed left-sided impairment in all experimental groups. Fluoroscopy showed paradoxical motion of the diaphragm in the muscle flap group for 1 to 2 months, and in the silastic repair group for 2 to 3 weeks, with near normal motion in the PTFE group for the entire postoperative period. These differences disappeared by 6 months. Prosthetic materials or muscle flaps are all safe for repair of large diaphragmatic hernias. Diaphragmatic growth occurs and the prosthesis remains in place. Physiologic impairment is minimal and not of clinical importance. Use of PTFE may be the preferred method as it develops better tissue incorporation and results in more normal diaphragmatic motion in the critical early postoperative period.

Animals↗
PubMed1984

Extraction of an intravascularized pacemaker lead--a new approach to an unusual problem.

A new catheter approach to removing an intravascularized, nonfunctional pacemaker lead which was fixed at both distal (right ventricular endocardium) and proximal (brachiocephalic vein/superior vena cava) ends is described. This case also emphasizes the need for removal of an old pacemaker lead that caused bacteremia in a patient with a prosthetic aortic valve even when infection was presumed to be cured.

Aged↗
PubMed1984

Membrane structural alterations in malignant and normal avian lymphocytes: a Raman investigation.

Resonance and nonresonance Raman spectra have been obtained from neoplastically transformed and normal avian lymphocytes. The acyl chains of membrane phospholipids of neoplastic cells are more highly unsaturated than those of normal cells. The observation of prominent carotenoid bands in both cell populations indicates the availability of a sensitive, intrinsic probe of membrane potential and local membrane environment.

Animals↗
PubMed1983

Calcium-dependent activation and deactivation of rod outer segment phosphodiesterase is calmodulin-independent.

ATP-dependent activation and deactivation of retinal rod outer segment phosphodiesterase is affected by calcium [Kawamura, S. and Bownds, M. D., J. Gen. Physiol. 77:571-591(1981)]. Our data demonstrate that although calmodulin has been found in rod outer segments [Liu, Y. P. and Schwartz, H., Biochim. Biophys. Acta 526:186-193(1978); Kohnken, R. E. et al, J. Biol. Chem. 256:12517-12522(1981)], this protein is not involved in calcium-dependent phosphodiesterase activation at light levels at which calcium clearly affects this enzyme's activity. Furthermore, calmodulin does not mediate the calcium-dependent deactivation of phosphodiesterase.

Animals↗