PubMed Health⌕ Search

Biomedical subjects

E W TAYLOR

Publications and source records attributed to E W TAYLOR.

16 recordsLinked to original sources
PubMed1965

THE MECHANISM OF COLCHICINE INHIBITION OF MITOSIS. I. KINETICS OF INHIBITION AND THE BINDING OF H3-COLCHICINE.

H(3)-colchicine of high specific activity (2.5 curies per mM) was prepared in order to study the mechanism of colchicine inhibition of mitosis in cultures of human cells, strain K.B. No direct effects on the duration of the cell cycle or macromolecular synthesis were demonstrable at a concentration of colchicine which completely inhibited mitosis. The radioactive compound was bound to the cells at a rate proportional to colchicine concentration. The binding appeared to be reversible since the radioactivity of the cells reached a maximum value for a given concentration and was slowly lost after resuspension of the cells in fresh medium. A suitable exposure to colchicine produced accumulation of metaphase-blocked mitoses after the colchicine was removed from the medium. An exposure of 6 to 8 hours at 10(-7)M was sufficient to block essentially all the cells in metaphase, thus indicating that colchicine is bound to the majority of interphase cells. The data are in quantitative agreement with a mechanism involving reversible binding of colchicine to a set of cellular sites. Based on the correlation between the time of first appearance of blocked mitoses and the radioactivity per cell, it is suggested that if a critical fraction (3 to 5 per cent) of the sites are complexed, the cell is unable to form a functional mitotic spindle.

Adenine↗
PubMed1963

Birefringence of protein solutions and biological systems. I.

The quantitative interpretation of birefringence of biological structures such as muscle requires a knowledge of intrinsic birefringence of the components. The intrinsic birefringence of fibrous structures as determined by variation of solvent index is positive while the intrinsic birefringence of proteins in solution is negative as calculated by the Peterlin-Stuart theory. As a first step in clarifying this discrepancy the basis of the Peterlin-Stuart theory has been re-examined. The theory has been recalculated from the standpoint of light scattering and extended to particles whose length is not small compared to the wavelength. The birefringence of a system of particles possessing a shell with index different from the bulk solvent has been obtained in order to interpret measurements in mixed solvents.

Biophysical Phenomena↗
PubMed1963

Birefringence of protein solutions and biological systems. II. Studies on TMV, tropocollagen, and paramyosin.

The intrinsic birefringences of TMV, tropocollagen, and paramyosin were calculated from flow birefringence measurements using the theory of Peterlin and Stuart. The values are -0.029, -0.029, and -0.030, respectively. The intrinsic birefringences of TMV and tropocollagen were measured as a function of the refractive index of the solvent in glycerol-water mixtures. In both cases the values were not constant and became less negative as the refractive index increased. Theoretical calculations showed that the large solvent effect could not be caused by a hydration shell of index different from that of the bulk solvent. It is concluded that either (a) the intrinsic birefringence calculated from the Peterlin-Stuart theory is incorrect or (b) the intrinsic birefringence depends markedly on the solvent. These results are of importance to the problem of quantitative polarized light microscopy since the separation of form and intrinsic birefringence contributions is based on the assumption that intrinsic birefringence is independent of solvent.

Biophysical Phenomena↗
PubMed1963

RELATION OF PROTEIN SYNTHESIS TO THE DIVISION CYCLE IN MAMMALIAN CELL CULTURES.

Protein synthesis in suspension cultures of human cells in logarithmic growth was inhibited with puromycin or chloramphenicol, and the growth rate and mitotic index were measured as a function of time. The mitotic index remained constant for about 1 hour after addition of inhibitor; this indicates that any protein synthesis necessary for mitosis is completed before the beginning of prophase. For rates of protein synthesis equal to or greater than 0.3 that of untreated cells, the index decreased over a 5- to-7-hour period and then remained constant. The final value of the index relative to that of the uninhibited control was approximately equal to the relative rate of protein synthesis. The period from the end of DNA synthesis to mitosis (G(2)) was increased by partial inhibition of protein synthesis. A mathematical model of the inhibition process has been formulated which predicts the shape of the mitotic index curves and the increase in the G(2) period. An interpretation of the model is that the rate-limiting step is the synthesis of an enzyme which catalyzes the formation of a compound necessary to initiate mitosis.

Anti-Bacterial Agents↗
PubMed1960

Physical-chemical studies of proteins of squid nerve axoplasm, with special reference to the axon fibrous protein.

The proteins in the axoplasm of the squid, Dosidicus gigas, have been resolved electrophoretically into a major fraction including the fibrous protein, and possibly its structural subunits, and a minor fraction including at least two proteins with low sedimentation coefficients. A partially reversible change in the structure of the fibrous protein occurs under the action of 0.4 M salt or high pH. These experiments have been interpreted to indicate that in the intact fiber one, or a few, protofibrils are arranged helically or longitudinally along the fiber axis, and linked by electrostatic bonds. On the dissociation of these bonds the separated protofibrils assume a less extended form and sediment more rapidly than the intact fibers. Some material with a lower sedimentation rate is also released on the dissociation. This fraction may comprise smaller chain fragments. The volume fraction and the approximate refractive index of the fibers have been calculated.

Animals↗
PubMed1959

Dynamics of spindle formation and its inhibition by chemicals.

The formation of the mitotic spindle of the newt cell in tissue culture has been studied, using polarized light. The rate of formation was measured and it was shown that the spindle increased in length at a constant rate until the maximum was attained. During metaphase the spindle shortened to about 50 to 60 per cent of its original length, reaching a minimum just before anaphase. No birefringence was detected in late anaphase in the spindle region after the chromosome masses had separated. The effects of certain compounds which are believed to inhibit protein synthesis were investigated. Chloramphenicol added in early prophase prevented the formation of a spindle of normal length. The possible relation of chloramphenicol to the synthesis of spindle proteins is discussed.

Anaphase↗
PubMed1956

Potable water.

Explore the source record for details and available documents.

Drinking Water↗