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Biomedical subjects

S Alexander

Publications and source records attributed to S Alexander.

At least 181 records · Page 10Linked to original sources
PubMed1984

Carbohydrate dramatically influences immune reactivity of antisera to viral glycoprotein antigens.

Analysis of the ability of heteroantisera, monoclonal antibodies, and antibodies to synthetic peptides to react with viral glycoproteins deglycosylated with endoglycosidase F revealed that the reactivities of most of the antibodies to these glycoprotein antigens were influenced by the attached carbohydrate moieties. All heteroantisera prepared in rabbits or goats to either fully glycosylated retroviruses or influenza virus were virtually unreactive toward the viral glycoproteins after carbohydrate removal. Analyses with a panel of monoclonal antibodies to purified Rauscher murine leukemia virus gp70 indicated that the reactivity of most of these antibodies improved while the reactivity of others decreased or remain unchanged after carbohydrate removal. Most of the antibodies to synthetic peptide sequences in the influenza virus hemagglutinin also improved in reactivity after carbohydrate removal. These data indicate that carbohydrate side chains on viral glycoproteins influence the immune response to these antigens, and the more native the glycoprotein immunogen, the more dramatic the carbohydrate influence. Thus the immune response to these glycoproteins is not simply a function of the immunogenicity of certain domains over others but rather is a direct measure of carbohydrate influences on the host's perception of the foreign antigen.

Antibodies, Monoclonal↗
PubMed1984

Demonstration of peptide:N-glycosidase F activity in endo-beta-N-acetylglucosaminidase F preparations.

Endo-beta-N-acetylglucosaminidase F preparations from Flavobacterium meningosepticum have been found to contain peptide:N-glycosidase activity. Only the second activity, designated as peptide:N-glycosidase F, readily cleaves the beta-aspartylglycosylamine linkage of a fetuin triantennary complex glycopeptide, as shown by the isolation of the corresponding carbohydrate-free peptide containing aspartic acid and of an intact oligosaccharide with a di-N-acetylchitobiosyl moiety at the reducing end. Both activities in the mixture will hydrolyze a high mannose octaglycopeptide from ovalbumin, with the type of product formed being influenced by pH. At pH 4.0, only the endo-beta-N-acetylglucosaminidase F activity is functional, releasing octapeptide-GlcNAc and oligosaccharide-GlcNAc. At pH 9.3, the predominant cleavage is by peptide:N-glycosidase F at the glycosylamine bond, releasing octapeptide and oligosaccharide-GlcNAc-GlcNAc. This latter oligosaccharide is then hydrolyzed by endo-beta-N-acetylglucosaminidase F to oligosaccharide-GlcNAc plus GlcNAc.

Acetylglucosaminidase↗
PubMed1984

Lethal multiple pterygium syndrome.

We report on two fetuses with a lethal form of multiple-pterygium syndrome born to first cousins. The two pregnancies aborted spontaneously in the 2nd trimester, the fetuses, 10-11 weeks of embryonic age, showing multiple pterygia and multiple cartilaginous fusions. One had cleft lip and palate. In both cases the microscopic anatomy of the placenta showed villi with scalloped border and intravillous trophoblastic invaginations.

Abnormalities, Multiple↗
PubMed1984

Intracranial metastases in the initial staging of bronchogenic carcinoma.

We evaluated the effectiveness of neurologic examination, electroencephalography (EEG), and computed tomography (CT) in the initial staging of patients with nonsmall cell carcinoma. Eight of 66 patients had evidence of intracranial metastases. Three of these had no other metastases and would otherwise have been surgical candidates. Thus, thorough investigation for evidence of intracranial metastases is warranted at the time of initial staging. The CT proved to be more effective than clinical evaluation or EEG, alone or in combination, in detecting intracranial metastases. The CT screening of patients prior to curative resection should increase the success rate for such procedures by eliminating patients with preexisting metastases.

Brain Neoplasms↗
PubMed1984

HLA-DR antigens of autologous melanoma and B lymphoblastoid cell lines: differences in glycosylation but not protein structure.

The HLA-DR antigen expressed on the surface of the human melanoma cell line SK-MEL-37 was characterized and compared with the HLA-DR antigen from the MU B lymphoblastoid cell line originating from the same individual. The HLA-DR heavy chain from SK-MEL-37 cells had an apparent mobility on SDS-PAGE slightly slower than that isolated from MU cells. In contrast, the HLA-DR light chains and the HLA-A,-B heavy chains from the two cell lines had identical mobilities. Double-labeled tryptic peptide mapping and limited N-terminal sequencing showed that the SK-MEL-37 HLA-DR antigen, like all previously examined B lymphoblastoid cell HLA-DR antigens, was homologous to the murine I-E/C subregion antigens and that the mobility difference of the SK-MEL-37 HLA-DR heavy chain was not attributable to differences in the primary structure of the polypeptide. Treatment of the cells with tunicamycin abolished the m.w. difference, suggesting that it was due to a change in glycosylation in SK-MEL-37. This was confirmed by analysis of the glycopeptides from pronase-digested HLA-DR light and heavy chains and HLA-A,B heavy chains purified from the two cell types. The results suggest 1) there is a difference in asparagine-linked oligosaccharide processing in the two cell types, with more of the larger complex glycans synthesized in the melanoma cells than in the B lymphoblastoid cells, 2) the effect is more pronounced with HLA-DR heavy chains than with HLA-DR light chains or HLA-A,B heavy chains, and 3) the oligosaccharide size difference is not solely due to sialic acid content.

Amino Acid Sequence↗
PubMed1983

Auranofin versus placebo in the treatment of rheumatoid arthritis.

In a six-month, multicenter, double-blind study involving 340 patients, auranofin, 3 mg twice daily, was compared with placebo in the treatment of adult-onset rheumatoid arthritis. All patients were continued on a therapeutic regimen of salicylates and/or a newer nonsteroidal anti-inflammatory drug. Patients in both treatment groups who completed six months of therapy with coded medications showed significant improvement in the clinical features of rheumatoid arthritis (that is, number of tender and swollen joints, severity of pain, grip strength and duration of morning stiffness); however, the mean improvement was greater in the auranofin-treated group. Fifty-two percent of the auranofin-treated patients compared with 24 percent of the placebo-treated patients (p less than 0.05) were judged by their physician to have shown marked or moderate improvement. Only in the auranofin-treated patients was there significant improvement from baseline in the laboratory parameters of disease activity: erythrocyte sedimentation rate, IgA, IgG, and IgM. After at least three months of therapy, 30 percent (46 of 152) of the placebo-treated patients but only 9 percent (13 of 152) of the auranofin-treated patients (p less than 0.05) withdrew from coded medication due to insufficient therapeutic effect. Study medication was discontinued by 5 percent (eight of 152) of the auranofin-treated patients and 3 percent (four of 152) of the placebo-treated patients because of adverse therapy events (p = 0.24). This study demonstrates the efficacy of auranofin when added to salicylates and/or nonsteroidal anti-inflammatory drugs in the treatment of rheumatoid arthritis.

Anti-Inflammatory Agents↗
PubMed1983

The T3 complex on human T lymphocytes involves four structurally distinct glycoproteins.

Monoclonal antibodies allow for the detection of antigens which are specific for human thymus-derived lymphocytes. Among these antigens, the T3 complex is of particular interest since it is involved in several T cell functions. The main target antigen of the anti-T3 reagents is borne by a 20-kDa glycoprotein. In addition, glycoproteins of 25-28, 37, and 44 kDa are found in anti-T3 immunoprecipitates derived from surface-labeled cells. The four antigens appeared to be strongly associated with each other in detergent-containing solutions. Comparative studies of the four proteins, facilitated by the use of endo-beta-N-acetylglycosaminidase F, revealed that their polypeptide backbones have different molecular weights and pI values. Moreover, peptide maps of the 20-kDa T3 and the 25-28-kDa T3 were quite different. Metabolic labeling experiments suggested that the 25-28-kDa protein might become associated with the 20-kDa T3 antigen during biosynthesis. The 37-kDa and 44-kDa proteins could not, however, be detected and, therefore, might become associated with the 20-kDa T3 on the cell surface. Evidence has been found for the existence of a fifth member of the T3 complex, namely an unglycosylated 20-kDa T3 species.

Antibodies, Monoclonal↗
PubMed1983

Mutants of Dictyostelium discoideum blocked in expression of all members of the developmentally regulated discoidin multigene family.

Mutant strains of D. discoideum are described that can complete morphogenesis and cytodifferentiation but which express vastly reduced levels of the galactose-binding lectins discoidin I and II (less than 1% and 1%-2% respectively) compared to the wild-type control. Mutant cells proceeding through development lack lectin activity, lectin protein, and specific lectin mRNA. In contrast, the genes encoding these proteins are present in their wild-type configurations in the genome. Since these proteins are encoded by four to five discrete genes, the mutations in these strains are most likely in genes involved in the regulation of the expression of members of this multigene family. The results also indicate that the discoidin lectins may not be required for fruiting body construction in this organism. Finally, coupled with the recent ability to transform D. discoideum, these mutants open the way to identification and isolation of regulatory genes and their products.

Cell Differentiation↗
PubMed1982

Fatal pneumothorax in "BCNU lung".

A patient with recurrent glioma treated with BCNU developed pneumothorax and interstitial pulmonary fibrosis. She died from "BCNU lung" and its complications, although she was free of her initial disease.

Adult↗