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Biomedical subjects

J Hong

Publications and source records attributed to J Hong.

At least 217 records · Page 12Linked to original sources
PubMed1986

Enkephalin contained in dentate granule cells is important for kainic acid-induced wet dog shakes.

Kainic acid (KA) caused an initial decrease and a subsequent rebound in hippocampal enkephalin (ENK) in rats exhibiting wet dog shakes (WDS) without behavioral convulsions. Antibody to methionine-enkephalin but not dynorphin A(1-8) injected into lateral ventricles attenuated KA-induced WDS, as did naloxone. Granule-cell destroying injections of colchicine into ventral but not dorsal hippocampus caused a 60% reduction of hippocampal ENK and a complete elimination of KA-induced WDS. These studies suggest that release of granule cell ENK, which is 3 times more concentrated in ventral than dorsal hippocampus, plays an important role in KA-induced WDS.

Animals↗
PubMed1985

Neuropeptides in human brain--postmortem studies.

Four neuropeptides (substance P, methionine-enkephalin, neurotensin and cholecystokinin) were measured by radioimmunoassays in a number of brain regions of deceased patients with mental illnesses and controls. The most striking finding in these studies was that methionine-enkephalin concentrations in caudate nuclei of chronic paranoid schizophrenic patients were reduced relative to several control groups. Neuroleptics had no obvious effects on any of the four measured neuropeptides. These findings are not inconsistent with the hypothesis that methionine-enkephalin may be involved in some of the pathology of the schizophrenic syndrome.

Adult↗
PubMed1985

The nature of microsomal N-nitrosodimethylamine demethylase and its role in carcinogen activation.

The subcellular localization of N-nitrosodimethylamine (NDMA) demethylase in rat liver cells and the role of this enzyme in the activation of NDMA were studied. The enzyme activity was predominantly located in the microsomal fraction and the addition of cytosol to the microsomes did not produce a synergistic effect. The microsomal NDMA demethylase activity appeared to correspond to the ability of the microsomes to convert NDMA to the alkylating species. The alkylation of DNA was assayed by the measurement of O6-methylguanine and 7-methylguanine by fluorescence after isolation by h.p.l.c. The induction of microsomal NDMA demethylase activity by isopropanol, ethanol, acetone, and fasting was closely related to the increase of DNA methylation by NDMA in an incubation system in vitro. Pretreatment of rats with ethanol, which induced hepatic NDMA demethylase activity, enhanced DNA alkylation in vivo with a high dose of NDMA (75 mg/kg body weight) but not with low doses of NDMA (less than or equal to 25 mg/kg body weight). The role of NDMA demethylase in the activation of NDMA is discussed.

Animals↗
PubMed1985

Stenotic lesions in dialysis-access fistulas: treatment by transluminal angioplasty using high-pressure balloons.

Eighty-four balloon dilatations of dialysis-access fistulas have been performed over a five year period. Fifty-two were done with polyethylene balloons and the last 32 with high-pressure Olbert balloons. Initial success was significantly greater with the high-pressure balloons, but long-term patency rates were similar. Use of high-pressure balloons and long inflation times is the method of choice for dilating venostenotic lesions in access fistulas.

Angioplasty, Balloon↗
PubMed1984

Dialysis access fistulas: treatment of stenoses by transluminal angioplasty.

Fifty-six balloon dilatations in 51 patients with upper-extremity dialysis access fistulas were performed over a 4-year period. Forty-four venous anastomotic lesions in patients with either internal or graft fistulas were dilated. Three arterial anastomotic lesions and nine distant venous stenoses were treated. Thirty-nine of 56 (70%) dilatations were initially successful. Of the initial successes, 28/35 (80%) were patent at 3 months, 19/27 (70%) at 6 months, 12/22 (55%) at 1 year, 7/14 (50%) at 2 years, and 3/9 (33%) at 3 years. Three complications (5%) were encountered. These included two graft thromboses and one pseudoaneurysm at the dilatation site. The procedure may be performed on an outpatient basis.

Adult↗
PubMed1984

Metabolism of nitrosamines by cytochrome P-450 isozymes.

Results are presented to show that N-nitrosodimethylamine demethylase is P-450 mediated and N-nitrosodimethylamine is efficiently metabolized by specific P-450 isozymes inducible by a group of new inducers. The P-450-mediated N-nitrosodimethylamine demethylase also responds differently to inhibitors when activities are compared with those of classical monooxygenase systems.

Animals↗
PubMed1983

Involvement of histidine and tryptophan residues of glutamine binding protein in the interaction with membrane-bound components of the glutamine transport system of Escherichia coli.

We treated the glutamine binding protein with diethyl pyrocarbonate (DEPC) and N-bromosuccinimide (NBS) to modify respectively the sole histidine and tryptophan residues and examined the effect of these modifications on the ability of the binding protein to bind glutamine as well as the ability to restore glutamine transport in membrane vesicles of Escherichia coli. Under the conditions used, both DEPC and NBS markedly inhibited the ability to restore glutamine transport in vesicles without any significant effect on glutamine binding. Moreover, saturating quantities of glutamine had no protective effect on the inactivation of the binding protein by DEPC or NBS. Fluorometric measurement and amino acid analysis indicate that the inactivation of the binding protein in restoring vesicle transport by NBS can be attributed to the oxidation of a single tryptophan residue. Similar analysis and the inability of hydroxylamine to reverse the effect of DEPC indicate that the effects of DEPC can probably be attributed to alterations of the sole histidine and/or one or more lysine residues of the binding protein. We conclude that the glutamine binding protein possesses at least two largely nonoverlapping functional domains, one responsible for glutamine binding and the other for the interaction with the other components of the glutamine transport system.

Biological Transport, Active↗
PubMed1983

Percutaneous transrenal balloon dilatation of the ureter.

Six strictures of the ureter were dilated with balloon angioplasty catheters. Two obstructed ureterovesical junctions in transplant patients were successfully treated. One obstructed ureteropelvic junction in a transplant kidney with a redundant ureter failed to respond. One of 2 uretero-ileostomy junction strictures was successfully treated, though one mid-ureteral stricture remained unchanged. Multiple dilatations were necessary in several patients. No significant complications were noted. Pre- and post-dilatation assessment of obstruction using the Whitaker test was helpful in transplant patients.

Adult↗
PubMed1981

The reconstitution of binding protein-dependent active transport of glutamine in isolated membrane vesicles from Escherichia coli.

The reconstitution of binding protein-dependent glutamine transport in isolated membrane vesicles from Escherichia coli is described. The reconstituted glutamine transport is shown to be energy-dependent and does not involve the metabolism of glutamine or the trapping of liganded binding protein with the vesicles. The preparation of vesicles capable of transporting glutamine in a binding protein-dependent manner required the incorporation of NAD into vesicles and the use of a binding protein point mutant as the source of the vesicles.

Biological Transport, Active↗
PubMed1981

Reconstitution of binding protein dependent active transport of glutamine in spheroplasts of Escherichia coli.

In order to directly prove that the periplasmic glutamine binding protein is an essential component of the osmotic shock sensitive active transport system for glutamine in Escherichia coli, we demonstrated the reconstitution of binding protein dependent glutamine transport in spheroplasts of that organism. It was shown by arsenate inhibition that the reconstituted transport system was energy dependent, and the use of azaserine, an inhibitor of glutamine-utilizing enzymes, indicated that the restoration of transport by binding protein did not require the metabolizing of the transport substrate. Furthermore, the binding protein dependent transport of glutamine was shown to require at least one other macromolecular component, presumably membrane bound, which was absent in a strain containing a deletion of the genes coding for the glutamine transport system but was present in a strain carrying a mutation only in the structural gene for the glutamine binding protein.

Arsenates↗
PubMed1980

Combination of enzymatic and mass fragmentographic assays for the identification and measurement of [met5]-enkephalin.

Dipeptidyl-aminopeptidase I (DAP I) was used to hydrolyze the pentapeptide-[met5]-enkephalin into the dipeptides Tyr-Gly and Gly-Phe and methionine. The dipeptides could be derivatized and resolved by gas chromagraphy (GC); quantification of these dipeptides was obtained by single ion monitoring. Tissue samples were prepurified with Bio-Beads SM-2 and used as substrate for DAP I. The yield of methionine and of the two dipeptides increases with time. Since the same dipeptides are produced by [met5]-enkephalin (ME) and [leu5]-enkephalin, the use of the ratios of the quantities of the two dipeptides with methionine could be used for recognition. Since the only internal standard available was one with deuterated methionine, the measurement of methionine released by DAP I from the prepurified tissue could be used to measure ME content in tissues that contain a small amount of heterogeneity in the molecular forms of ME. The present GC-mass spectrometric method can be used to quantify ME in brain but not in adrenal medulla because this tissue contains a high degree of molecular heterogeneity.

Animals↗