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Biomedical subjects

T Fujimura

Publications and source records attributed to T Fujimura.

At least 235 records · Page 13Linked to original sources
PubMed1983

Mechanism of glutamate transport in Escherichia coli B. 1. Proton-dependent and sodium ion dependent binding of glutamate to a glutamate carrier in the cytoplasmic membrane.

Specific binding of glutamate to its carrier was investigated by using cytoplasmic membrane vesicles prepared from Escherichia coli B. The binding activity was specifically affected by the Na+ and H+ concentrations of the medium. Cytoplasmic membrane vesicles from the mutant strain 36-39 that is defective in the Na+-dependent glutamate transport system showed no binding of glutamate. Addition of the protonophore uncoupler 3,5-di-tert-butyl-4-hydroxy-benzylidenemalononitrile or carbonyl cyanide m-chlorophenylhydrazone, or the ionophore monensin or nigericin, did not inhibit the binding, indicating that the binding reaction is not energy dependent. The parameters of binding were determined in reaction media with various combinations of H+ and Na+ concentrations. The maximum number of binding sites was constant and determined to be 70 pmol/mg of membrane protein, irrespective of the concentrations of H+ and Na+ in the medium. The apparent dissociation constant, however, was greatly affected by changes in the concentrations of both H+ and Na+, in such a way that it was expressed by a linear combination of the reciprocals of the H+ and Na+ concentrations. The characteristics of binding can be explained best by supposing that glutamate can bind only to a H+/Na+/carrier complex that is formed by random binding of H+ and Na+ to the unloaded carrier. The physiological role of this elementary binding reaction and of this quaternary complex as an active intermediate in the process of glutamate transport is discussed.

Biological Transport↗
PubMed1983

Mechanism of glutamate transport in Escherichia coli B. 2. Kinetics of glutamate transport driven by artificially imposed proton and sodium ion gradients across the cytoplasmic membrane.

Simultaneous imposition of a pH gradient (delta pH, interior alkaline) and a sodium gradient (delta pNa, [Na+]out greater than [Na+]in) across cytoplasmic membrane vesicles from Escherichia coli B led to a several hundred fold accumulation of glutamate. Although less effective, delta pH (interior alkaline)( alone caused accumulation of glutamate in the presence of Na+. In addition, delta pNa ([Na+]out greater than [Na+]in) alone also drove the transport system, where the maximum level of glutamate accumulation was affected by the pH of the medium. A membrane potential imposed by valinomycin-induced K+ diffusion (interior negative) enhanced the accumulation, indicating that the system operation in an electrogenic manner. The Michaelis constant of glutamate transport was greatly affected by changes in the concentrations of both Na+ and H+ and could be expressed by a linear combination of the reciprocals of the Na+ and H+ concentrations in the medium. On the contrary, a membrane potential (interior negative) exerted its effect by increasing the maximum velocity. When membrane vesicles were loaded with glutamate and Na+, but not with glutamate alone, rapid efflux of glutamate with Na+ as the cocation down the concentration gradients took place upon dilution. These results indicate that both Na+ and H+ are syn-coupled ions of glutamate transport in E. coli B and that the carrier/Na+/H+/Glu- complex observed in the binding reaction is an intermediate in the transport.

Biological Transport↗
PubMed1977

Acute obstructive suppurative cholangitis in a man with an enlarged inferior pancreaticoduodenal lymphnode.

A case report of a 55-year-old male, who was seen with epigastric pain and hyperamylasemia, is to be presented. He failed to respond to the intensive antibiotic therapy, and subsequently acute obstructive suppurative cholangitis fully developed. At laparotomy, an inflammatory enlarged inferior pancreaticoduodenal lymphnode, which apparently compressed the common bile duct, was found. To our knowledge, no prior case of acute obstructive suppurative cholangitis provoked by an enlarged lymphnode has been reported. A plea is made for attention to lymphnodes involved by inflammatory or neoplastic disorders, as well as common provoking agents such as calculi.

Acute Disease↗
PubMed1975

Gamma camera images of the salivary gland using 99mTc. Report of four cases.

Following the intravenous injection of 99mTc pertechnetate, the gamma camera enabled us to define the dynamic characteristics of salivary gland function as well as morphologic characteristics in a normal patient and in three patients with diseased parotid glands. We will continue this study in an attempt to define further the functional and morphologic characteristics of abnormal salivary glands.

Adenocarcinoma↗