Biomedical subjects

J A Forrester

Publications and source records attributed to J A Forrester.

32 records · Page 2Linked to original sources

PubMed1981

Concanavalin A-induced modification of the electrophoretic mobility of lymphocytes. Effect of colchicine and cytochalasin B.

Concanavalin A induces redistribution, i.e. "capping" and endocytosis of its receptors, on the surface of lymphocytes. This phenomenon has been shown to alter the cellular surface charge density. Colchicine, which depolymerises cytoplasmic microtubules, and cytochalasin B, which inactivates microfilaments, were used to determine the transmembrane control of the changes in the electrophoretic mobility of mouse lymphocytes. Colchicine neither inhibited nor modified the lectin-induced changes, irrespective of whether the cells were exposed to this agent before or after the interaction with concanavalin A. Pre-incubation with cytochalasin B, on the other hand, inhibited the alterations induced by concanavalin A. Cytochalasin B also reversed the altered electrophoretic mobilities of concanavalin A-treated lymphocytes. These data provide further confirmation of the relationship between lectin-induced redistribution and the electrokinetic behaviour of lymphocytes and establish that "capping" but not endocytosis of the glycoprotein receptors is responsible for the electrophoretic changes.

Animals↗

PubMed1980

Peanut lectin binding properties of germinal centres of mouse lymphoid tissue.

Peanut (Arachis hypogaea) lectin (PNL) has been shown to agglutinate the 90% of cells from murine thymus which are supposed to be immature cortical thymocytes. Further studies on the numbers of thymocytes binding fluorescein isothiocyanate conjugated PNL (FITC-PNL) confirmed the large proportion of PNL binding cells. In other organs such as bone marrow, spleen and peripheral lymph nodes, smaller proportions of PNL positive cells have been recorded. PNL-positive cells outside the thymus have been reported to be either Thy 1-positive or null cells. It has also been suggested that PNL binding may be a marker for immaturity not only in relation to T lymphocytes but also amongst haematopoietic stem cells. Thus PNL binding as an aspect of lymphocyte differentiation is a matter of considerable interest. The current study describes the distribution of horseradish peroxidase-conjugated PNL (HRP-PNL) on frozen sections of mouse lymphoid organs. It seems that PNL binds to cells in germinal centres but not to those in some other areas containing activated lymphocytes. There is good correlation between the presence of PNL-binding germinal centres in frozen sections of lymphoid organs and the number of PNL-binding cells counted in cell suspensions from the same organs.

Animals↗

PubMed1978

Surface charges on chloroplast membranes as studied by particle electrophoresis.

1. Particle microelectrophoresis mobility studies have been conducted with chloroplast thylakoid membranes and with isolated intact chloroplasts. 2. The pH dependence of the electrophoretic mobility indicated that at pH values above 4.3 both membrane systems carry a net negative charge. 3. Chemical treatment of thylakoids has shown that neither the sugar residues of the galactolipids in the membrane nor the basic groups of the membrane proteins having pK values between 6 and 10 are exposed at the surface. 4. However, treatment with 1-ethyl-3(3-dimethylaminopropyl)carbodiimide, together with glycine methyl ester, neutralized the negative charges on the thylakoid membrane surface indicating the involvement of carboxyl groups which, because of their pH sensitivity, are likely to be the carboxyl groups of aspartic and glutamic acid residues. 5. The nature of the protein giving rise to the negative surface charges on the thylakoids is not known but is shown not to involve the coupling factor or the light harvesting chlorophyll a/chlorophyll b pigment . protein complex. 6. No significant effect of light was observed on the electrophoretic mobility of either thylakoids or intact chloroplasts. 7. The striking difference in the ability of divalent and monovalent cations to screen the surface charges was demonstrated and explained in terms of the Gouy-Chapman theory. 8. Calculations of the zeta-potentials for thylakoid membranes gave values for the charge density at the plane of shear to be in the region of one electronic charge per 1500--2000 A2. 9. The significance of the results is discussed in terms of cation distribution in chloroplasts and the effect of cations on photosynthetic phenomena.

Cell Membrane↗

PubMed1977