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Biomedical subjects

T H Wilson

Publications and source records attributed to T H Wilson.

At least 91 records · Page 5Linked to original sources
PubMed1984

Volume regulation in Mycoplasma gallisepticum.

Cells of Mycoplasma gallisepticum incubated in 250 mM NaCl in the absence of glucose for several hours show swelling and eventual lysis. This swelling is believed to be due to colloid osmotic and Donnan forces, since it is prevented by the addition of nondiffusable solutes such as sucrose or MgSO4. The addition of glucose during the swelling stage (but before lysis) caused shrinkage and return to initial volume. Experiments on Na+ and H+ movement are consistent with the operation of an ATP-driven H+ pump and a Na+/H+ exchange reaction.

Adenosine Triphosphate↗
PubMed1982

Altered cation coupling to melibiose transport in mutants of Escherichia coli.

The alpha-galactoside transport system of Escherichia coli utilizes either H+ of Na+ as a coupling cation for melibiose transport. Mutants were isolated which showed altered cation recognition for melibiose transport. The transport carrier of the mutants has lost the ability to accept H+ but can utilize either Na/ or Li+ for co-transport with melibiose. Such mutants might be predicted if the melibiose carrier were viewed as a descendant of an evolutionary transition between the H+-substrate co-transport systems of primitive cells and the Na+-substrate systems of more complex organisms. A second mutation was found in these mutants which involves the Na+ (Li+)-H+ exchange carrier. The maximal rate of Li+-H+ exchange in one of the mutants was 11 times higher than the parent and the Km for Li+ by this carrier was one-sixth that of the parent.

Biological Transport, Active↗
PubMed1982

Solubilization and reconstitution of the melibiose carrier from a plasmid-carrying strain of Escherichia coli.

A strain of EScherichia coli was constructed containing a plasmid from the Clarke-Carbon collection that showed high levels of melibiose transport activity. Membranes from the plasmid-containing strain were extracted with octyl-beta-D-glucopyranoside and melibiose transport was reconstituted in liposomes. The proteoliposomes exhibited counterflow activity, as well as membrane potential and sodium gradient-driven melibiose accumulation.

Escherichia coli↗
PubMed1981

Inhibition of growth of Escherichia coli by lactose and other galactosides.

A study has been made of the inhibition of growth caused by the addition of lactose or other galactosides to lac constitutive Escherichia coli growing in glycerol minimal medium. The effect was greater at pH 5.9 and pH 7.9 than at pH 7.0. Inhibition of growth by lactose was observed also in the case of a beta-galactosidase negative mutant. However, a lacY mutant, which has a defect in the entry of protons normally coupled with galactoside transport, showed only slight inhibition of growth on the addition of galactosides. In the case of the parental strain the addition of lactose resulted in a sharp fall in delta pH across the cell membrane and a reduction in intracellular ATP, and the recovery was slow. Under the same conditions the lacY mutant showed a smaller and only transient effect. It is postulated that the sudden entry of protons associated with lactose uptake lowers the protonmotive force, reducing the ATP levels and inhibiting growth of the cells. This hypothesis would account also for the selection of lacY mutants found when E. coli is grown in the presence of isopropyl-beta-D-thiogalactoside.

Escherichia coli↗
PubMed1981

Purification and reconstitution of functional lactose carrier from Escherichia coli.

The lactose carrier protein of Escherichia coli was purified by a simple procedure employing differential solubilization and ion-exchange chromatography and reconstituted into liposomes by octylglucoside dilution. The proteoliposomes exhibited both membrane potential-driven lactose transport and lactose counterflow. Furthermore, the purified protein was identified as the product of the lac y gene. These and other results demonstrate that the lactose carrier is the only polypeptide species essential for energy-coupled lactose transport and counterflow.

Amino Acids↗
PubMed1981

Posterior transsphincteric approach for surgery of the rectum: the Bevan operation.

This report presents the history and technique of, and some clinical experience with, the posterior transsphincteric approach for surgery of the rectum. On the basis of an extensive historical review, it is suggested that the procedure be called the Bevan operation. The method deserves a definite place in the armamentarium of the rectal surgeon, especially in the management of villous tumors.

Aged↗
PubMed1981

Proton motive force across the membrane of Mycoplasma gallisepticum and its possible role in cell volume regulation.

A proton motive force (delta (-) microH+) of 70 to 130 mV was measured across the membrane of Mycoplasma gallisepticum cells. The membrane potential was measured utilizing the lipid-soluble cation tetraphenylphosphonium. The method was validated by showing that in the presence of valinomycin the ratio of the concentrations (in/out) of tetraphenylphosphonium agreed well with those for K+ and Rb+. The pH gradient was calculated from the measured distribution ratio of benzoic acid. The proton motive force was approximately the same in cells harvested at early exponential, midexponential, and stationary phases of growth. The proportion of pH gradient to membrane potential varied with external pH. In the absence of glucose, cells incubated in an isosmotic NaCl solution showed low adenosine triphosphate and delta (-) microH+ levels and a tendency to swell and lyse compared with cells incubated with added glucose. It is concluded that energy is required for normal cell volume regulation.

Adenosine Triphosphate↗
PubMed1981

Secondary aorto-enteric fistulas: prosthetic and paraprosthetic.

Four cases of aortoenteric and paraprosthetic-enteric fistulization are presented. Particular emphasis is placed on the distinct clinicopathologic characteristics of these two types of graft-enteric fistula which, if unrecognized, result in an almost invariably fatal outcome. Available data as well as the cases herein reported clearly demonstrate the need for a higher index of suspicion and strict adherence to well-established principles for management of complicated aortic grafts. Best results can be obtained with prompt surgical intervention, total removal of all prosthetic material and lower extremity revascularization by means of extra-anatomic bypass.

Aged↗
PubMed1980

Membrane transport of p-nitrophenyl-alpha-galactoside by the melibiose carrier of Escherichia coli.

p-Nitrophenyl-alpha-galactoside (alpha-pNPG) was found to be a substrate for the melibiose transport system of Escherichia coli. This sugar enters induced cells via the carrier and is split by alpha-galactosidase to galactose and p-nitrophenol. In mutant cells lacking the alpha-galactosidase [3H]-alpha-pNPG accumulated to concentrations 15 times higher than the external medium. The transport of alpha-pNPG is inhibited by both Na+ and Li+. Na+ (10 mM) reduced the Km for alpha-pNPG from 0.45 to 0.18 mM and reduced the Vmax from 6.7 nmoles/min/mg dry wt to a value of 3.0.

Biological Transport, Active↗