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Biomedical subjects

M Webb

Publications and source records attributed to M Webb.

At least 217 records · Page 12Linked to original sources
PubMed1972

Interaction of carcinogenic metals with tissue and body fluids.

In addition to cobalt, metallic nickel, cadmium and other metals (e.g. zinc and copper) dissolve when incubated with horse serum at 37°. The dissolving property of copper in serum resembles that of cobalt, its solubility being increased greatly in the presence of oxygen, whereas the solubilities of cadmium, zinc and most preparations of nickel are the same aerobically and anaerobically. In all of these "metal-sera" the cations are bound, although in different proportions, both by proteins and by small diffusible molecules.Although Co(2+) ions and cobalt-serum cause limited catalytic oxidation of fresh serum, most of the oxygen uptake by suspensions of metallic cobalt in serum, or by more simple model systems, is due to absorption of oxygen by the metal powder; the consequences of this are discussed.Metallic cobalt, cadmium and nickel dissolve readily when incubated with sterile homogenates of rat muscle (and other tissues), the dissolved cations being bound predominantly by small, diffusible molecules, rather than by the protein components. Binding by small molecules, in preference to proteins, also occurs when the metals dissolve in vivo. In both the in vivo and in vitro systems, the metallic ions are not bound by a specific cation carrier, but are distributed amongst a number of components. These components have greater affinities for the dissolved metals than serum proteins and seem likely to be the normal cation carriers in vivo. As in serum, solubility in muscle homogenates is not a specific property of the carcinogenic metals as other, non-carcinogenic metals also dissolve. The specificity of the former metals, therefore, is attributed to the subsequent effects of the dissolved cations after intracellular incorporation.

Animals↗
PubMed1972

Uptake of 63 Ni 2+ from its complexes with proteins and other ligands by mouse dermal fibroblasts in vitro.

A study has been made of the uptake of (63)Ni(2+) from its complexes with serum proteins and with the small molecules from a sterile autolysate of rat muscle by cells of the C57S/IP line of mouse dermal fibroblasts in vitro. Nickel from these complexes is incorporated intracellularly, the distribution being independent of the nature of the carrier. The cation is associated with all subcellular fractions, the largest amount being bound by the nuclei and the least by the microsomes. About half of the (63)Ni(2+) incorporated into the nuclei is located in the nucleoli.

Animals↗
PubMed1968

Pyruvate metabolism by aminopterin-inhibited Aerobacter aerogenes.

1. The synthesis and utilization of both alanine (by reductive amination, oxidative deamination and transamination) and valine (by transamination only) in Aerobacter aerogenes are unaffected by aminopterin. These amino acids, which accumulate in aminopterin-treated cultures of this organism, are therefore considered to be formed as secondary products from the excess of pyruvate that also accumulates. 2. Oxidative metabolism of pyruvate and the synthesis of acetylmethylcarbinol by A. aerogenes cells are unaltered by growth in the presence of aminopterin. 3. Cells from static and anaerobic cultures that have been treated with the folic acid antagonist in the early exponential phase have a decreased ability to cleave pyruvate to acetate and formate, and to effect the exchange of formate with the carboxyl group of pyruvate. 4. 3-Methyl-2-oxobutanoate, the keto acid precursor of valine, cannot replace pyruvate as substrate in either the phosphoroclastic or the exchange reaction.

Alanine↗
PubMed1968

Pyruvate accumulation in growth-inhibited cultures of Aerobacter aerogenes.

1. Accumulation of pyruvate occurs during the early stages of exponential growth of aerobic, anaerobic and static cultures of a strain of Aerobacter aerogenes. In normal cultures of this organism the content of pyruvate increases until most of the glucose of the medium has been consumed, and then declines rapidly. The presence of unconsumed sugar is not the sole reason for the accumulation of keto acid, since this is unaffected by the addition of extra glucose to either exponentialphase or stationary-phase cultures. 2. In aminopterin-inhibited cultures, the rate of glucose utilization is decreased greatly, and pyruvate continues to accumulate throughout the period of incubation. This prolonged phase of accumulation appears to be a consequence of the growth inhibition, and not to a specific action of aminopterin on the phosphoroclastic breakdown of pyruvate, since it occurs also when growth is restricted by the antibiotics streptomycin, chloramphenicol and neomycin. 3. A possible explanation is suggested for the accumulation of pyruvate in the inhibited cultures.

Aminopterin↗