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Biomedical subjects

J Bryan

Publications and source records attributed to J Bryan.

At least 199 records · Page 11Linked to original sources
PubMed1978

Differences among 100-A filamentilament subunits from different cell types.

The protein subunit of 100-A filaments constitutes approximately 50% of the cytoskeleton protein of chick fibroblasts. In addition to the 43,000-dalton protein (constitutive actin) common to all cell types, fibroblast cytoskeletons contain a 58,000-dalton protein likely to be the 100-A filament subunit, whereas smooth muscle contains, instead, a 55,000-dalton protein. Additional differences among 100-A filaments are shown by immunofluorescence using antibodies angainst chick fibroblast 58,000-dalton component (anti-F58K) and against chick brain 100-A filament subunits (anti-BF). Anti-F58K binds to 100-A filaments in chick fibroblasts, presumptive myoblasts, chondroblasts, pigment cells, and neurons, but not to 100-A filaments in mouse or human fibroblasts. This antibody stains cables of 100-A filaments induced by sequentially treating cells with cytochalasin B and Colcemid. Anti-BF binds only to neurofilaments and not to 100-A filaments of other cell types studied. Absorption or antibodies with purified subunits from gizzard 100-A filaments eliminates binding of anti-F58K to the filaments of all cell types but does not diminish binding of anti-BF to neurofilaments. Various IgGs also bind nonspecifically to induced cables of 100-A filaments. The problem of nonspecific binding of labeled antibodies, as well as the problem of cell and species specificity of the 100-A filaments, is discussed.

Actins↗
PubMed1976

High uptake of myo-inositol by rat pancreatic tissue in vitro stimulates secretion.

A recent study by Hokin-Neaverson, M., Sadeghian, K., Majumder, A.L., and Eisenberg, F. (1975) Biochem. Biophys. Res. Commun. 67, 1537-1544, demonstrates that free myo-inositol in the pancreas is significantly increased during intense cholinergic stimulation of secretion. Incubation of rat pancreatic tissue in medium with 100 mM myo-inositol increases 10-fold the endogenous content of free myo-inositol and elicits a prompt and sustained 50% increase in the rate of release of amylase activity. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis reveals that the electrophoretic pattern of the protein mixture released in the presence of 100 mM myo-inositol is the same as that of the secretory output released in the presence of 10 muM carbamylcholine. Microscopic examination of tissue pieces indicates that there is no significant decrease in zymogen granule content of the pancreatic acinar cells during incubation in medium with 100 mM myo-inositol. Jamieson, J.D., and Palade, G.E. (1967) J. Cell Biol. 34, 597-615, have shown that pulse-labeled secretory proteins in guinea pig pancreas first appear in zymogen granules 1 hour postpulse, becoming maximally accumulated in these storage sites by 2 hours postpulse. myo-Inositol (100 mM) stimulates release of pulse-labeled secretory proteins only if incubation in medium with 100 mM myo-inositol is initiated anytime during the first 80 min postpulse. The findings thus indicate that a high uptake of myo-inositol by rat pancreatic tissue in vitro selectively stimulates the release of just those secretory proteins being packaged in newly forming zymogen granules.

Amylases↗
PubMed1976

Remission induction with L-asparaginase, vincristine, and prednisone in children with acute nonlymphoblastic leukemia.

Forty-five children with acute nonlymphoblastic leukemia in relapse received a total of 56 courses of L-asparaginase combined with vincristine and prednisone. The complete remission rate of 40% (12 of 30 trials) in patients resistant to vincristine and prednisone was almost identical to that in children still sensitive to vincristine and prednisone (42%, 11 of 26 trials). The complete remission rate of 38% (14 of 37 exposures) in those children who had not received L-asparaginase previously compared favorably with the complete remission rate in those children who had received prior L-asparaginase (47%, 9 of 19 exposures). Forty-seven of the 56 induction trials were in children with 1 or more remissions and 14 of these were in children with 3 or more prior remissions. Toxicity was minimal.

Acute Disease↗
PubMed1976

A quantitative analysis of microtubule elongation.

Methods have been developed for differentially inhibiting microtubule nucleation and elongation in vitro. By use of polyanions, assembly-competent tubulin solutions of several milligrams/milliliter can be prepared which do not exhibit appreciable spontaneous assembly during the time-course of an experiment. Microtubule elongation can be initiated by the addition of known numbers of microtubule fragments. A detailed analysis of the resulting process demonstrates that: (a) rings are not obligatory intermediates in the nucleation sequence, and neither rings nor protofilament sheets are obligatory intermediates in the elongation reaction. (b) The end of an elongating microtubule often has a short region of open protofilament sheet or "C-microtubule" similar to that observed in vivo. (c) The development of turbidity follows a simple exponential approach to an equilibrium value. (d) The final equilibrium values are independent of the number of added nucleating fragments, while the initial growth rates and half-times to reach equilibrium are dependent on the number of added nuclei. (e) The final lengths of the microtubules at equilibrium are inversely proportional to the number of added fragments. (f) The equilibrium constants are independent of microtubule length. (g) The number of assembly and disassembly sites per microtubule is not a function of microtubule length. (h) The forward rate constants, the final polymer concentrations, and growth rates of microtubules are dependent upon the concentration of polyanion present. These results are strongly supportive of the idea that microtubule assembly is a "condensation-polymerization" and provide basic information on the kinetics and length distributions of the elongation in vitro.

Cellulose↗
PubMed1973

Microtubules: evidence for 13 protofilaments.

When microtubules are fixed in glutaraldehyde in the presence of tannic acid and thin sections cut, the subunit structure of the microtubule is readily observed without the need of image reinforcement. Seven types of microtubules were analyzed: those in the heliozoan axoneme, the mitotic apparatus, the contractile axostyle, repolymerized microtubules derived from the chick brain, the central pair in flagella, and the A tubules of flagella and the basal body. In all cases microtubules were composed of 13 equally spaced protofilaments. The B tubules in flagella and the basal body appear to be composed of 11 subunits. The connections of the B to the A and the C to the B are described. A model of a microtubule is presented.

Animals↗