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Biomedical subjects

I M Roberts

Publications and source records attributed to I M Roberts.

69 records · Page 4Linked to original sources
PubMed1977

Partial amino acid sequence of two major component polypeptides of hepatitis B surface antigen.

Determination of the amino acid sequence of the immunogenic polypeptides of hepatitis B surface antigen may not only permit molecular localization of the distinct determinants a, d, and y but may also lead to the synthesis of a hapten useful in prophylactic immunization against hepatitis B virus infection. For this purpose, purified monotypic hepatitis B surface antigen of adw subtype was resolved into equal amounts of two major polypeptides (22,000 and 28,000 daltons) and up to six other minor polypeptides by polyacrylamide gel electrophoresis. With the periodate staining reaction, only the 28,000-dalton polypeptide stained as a glycoprotein. Guinea pigs immunized with the 22,000-dalton polypeptide produced potent antisera against determinants a and d, but the 28,000-dalton glycoprotein did not induce a response. Both polypeptides isolated by preparative polyacrylamide gel electrophoresis showed amino acid composition identical with that of the intact antigen. For both polypeptides, hydrazinolysis gave Ile as the carboxyterminus, and carboxypeptidase A digestion gave the same terminal sequence, Val-Tyr-Ile. Both peptides also yielded an identical sequence of amino acids in nine steps of Edman degradation--Met-Glu-Asn-Ile-Thr-Ser(Cys)-Gly-Phe-Leu. Our data suggest that hepatitis B surface antigen contains a single major immunogenic 22,000-dalton polypeptide component, part of which is modified by the addition of carbohydrate to give rise to the glycopeptide of apparent molecular weight 28,000.

Amino Acid Sequence↗
PubMed1977

Radioimmunoassay of hepatitis B core antigen and antibody with autologous reagents.

Anti-HBc is the most sensitive indicator of current or recent hepatitis B virus infection, hence its detection is valuable in laboratory diagnosis of the infection. Dane particles isolated from the plasma of a single chronic carrier and his autologous IgG labeled with 125I were utilized in a solid-phase sandwich radioimmunoassay for anti-HBc. The principle of serologic neutralization of core antigen and consequent inhibition of binding of the cores to the solid-phase rendered the method to be a simple, sensitive, specific and rapid means of detecting anti-HBc.

Antibodies, Viral↗
PubMed1977

Experimental autoimmune encephalomyelitis in mice: antigen binding lymphocytes to basic protein of myelin in susceptible and resistant strains.

Antigen-binding lymphocytes (ABL) to basic protein of myelin (BPM) were demonstrable in the thymus and spleen of various strains of mice. Counts of ABL did not differ in strains resistant and susceptible to EAE, and did not differ when human or murine 125I-labelled BPM was used as a labelled antigen to detect ABL. After injection with mouse spinal cord and adjuvants, under conditions known to be immunogenic and encephalitogenic for susceptible strains of mice, counts of ABL increased two- to four-fold in suceptible strains but did not icnrease in resistant strains. Antigen binding could not be accounted for by the attachment to cells of cytophilic antibody with specificity for BPM, because such antibody was seldom demonstrable even after immunization. Inferences from the study were: (i) that tolerate (non-responsiveness) to certain autoantigens at least must depend on control over continually present antigen-reactive lymphocytes rather than on any lack of capacity to recognize antigen; (ii) differences in susceptible and resistant strains are evident after, rather than before, immunization.

Animals↗
PubMed1975

Tungsten coating--a method of improving glass microtome knives for cutting ultrathin sections.

Glass knives for ultramicrotomy were considerably improved by coating the cutting edge with a film of evaporated tungsten metal. Knives treated by this method gave up to tem times as many acceptable sections as uncoated glass knives. They could also cut thinner sections and harder tissues than ordinary glass knives, and eliminated some of the cutting artefacts produced by them. No explanation for this improvement was found although several possibilities were examined.

Glass↗
PubMed1975

Handling and staining epoxy resin sections for light microscopy.

Epoxy resin sections 0 1-1.0 mum thick of specimens embedded for electron microscopy, were collected from the ultramicrotome using strips of cover slip, and, after drying on a hot plate, were bulk stained in specially made troughs. After treatment with periodic acid, the sections were stained first in basic fuchsin at 70 degrees C and then in alkaline methylene blue at room temperature. The handling technique allows accurate collection of serial sections without interrupting the sectioning process, and the stain combination is suitable for different specimens in different epoxy resins and is unaffected by storage for more than 1 year.

Epoxy Resins↗
PubMed1975

Antigen-binding cells in human fetal liver.

Antigen-binding cells (ABC) could be detected regularly by autoradiography among haemic cells in the liver of human fetuses ranging in age from 8 to 24 weeks. For radioiodine-labeled thyroglobulin, the antigen mainly used in these studies, counts of ABC ranged from 5.0 to 24.3 per 1,000 cells scanned. There was a trend for counts of ABC in liver to be highest at 10-12 weeks of fetal life. Binding of labeled thyroglobulin was inhibited by excess unlabeled thyroglobulin, but not by other protein antigens. Artifacts due to binding of antigen to normoblasts, which comprised 90% of the haemic cells in fetal lines, and to cells with 'sticky' surfaces were excluded as far as possible. There was no response by fetal liver cells to phytohaemagglutinin. Although there was only minimal inhibition of binding by anti-immunoglobulin sera of known potency, the ABC in human fetal liver were assumed to correspond to immunoglobulin-bearing precursors of B cells described by others in the liver of the fetal mouse.

Antigens↗
PubMed1975

Populations of lymphocytes separated from human thymocytes.

Thymocytes from twenty-two human foetal and post-natal thymuses were separated according to their buoyant density. Thymocytes from eight were separated into multiple fractions by means of continuous gradients of bovine serum albumin (BSA), pH 5.1 and iso-osmolar with human cells, and thymocytes from fourteen were separated into two fractions of density less than and greater than 1.068 g/cm3. Fractions were tested for antigen-binding lymphocytes (ABL) to 125I-labelled human thyroglobulin, for response to phytohaemagglutinin (PHA) and for rosette-forming cells (RFC) using sheep red blood cells. For subjects of all ages there was a pronounced enrichment of both ABL and thymocytes responsive to PHA amoung low or 1.064-1.065 g/cm3 density thymocytes. In older subjects there was a second enrichment of ABL among high or 1.072-1.073 g/cm3 density thymocytes. RFC were distributed over a wider range of densities, and although they did not form a discrete subpopulation they predominated among high density thymocytes.

Cell Separation↗