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Biomedical subjects

Y Koga

Publications and source records attributed to Y Koga.

At least 451 records · Page 25Linked to original sources
PubMed1987

Repertoire of the human T cell gamma genes: high frequency of nonfunctional transcripts in thymus and mature T cells.

To further understand the structural diversity and function of the human T cell-specific gamma gene, 20 human gamma gene cDNA from both thymocyte and peripheral blood T lymphocyte libraries were sequenced and analyzed. Evidence of greater germ-line multiplicity and more extensive use of junctional flexibility, N-region diversity and perhaps D gamma gene segment incorporation was observed. In spite of the larger gamma gene repertoire found in humans compared to mice, the potential of the human gamma gene message to encode a functional product appears to be severely limited. In addition to the extremely low levels of gamma gene expression observed, each of the 20 gamma gene cDNA exhibit some form of deleterious mutation defect. This is in sharp contrast to the finding that human and mouse T cell antigen receptor alpha and beta messages isolated from various sources have functional coding potential in most cases. Thus, the role of the human T cell gamma gene becomes even more uncertain than before.

Amino Acid Sequence↗
PubMed1987

Positive effects of indomethacin on restoration of splenic nucleated cell populations in mice given sublethal irradiation.

Splenic cellularity during the recovery phase after 400-R irradiation was evaluated in mice, in which the level of prostaglandin was regulated by indomethacin and exogenous prostaglandin E2, following sublethal irradiation. Two weeks after irradiation, administration to these mice of indomethacin, an inhibitor of prostaglandin synthesis, augmented the recovery of all nucleated spleen cell populations, whereas the thymus was drastically depopulated. This treatment had little effect upon the total number of bone marrow cells but inversed the ratio of PNA+/PNA- cells. Cell transfer experiments using heavily irradiated mice as recipients showed that the stem cell proliferation was positively affected by indomethacin treatment in the bone marrow rather than in the spleen. These results suggest that cell migration from primary lymphoid organs, particularly from the bone marrow to the spleen, is regulated by a prostaglandin-mediated system and that a prostaglandin E2 synthesis inhibition would have a positive effect on the restoration of peripheral nucleated cells following irradiation.

Animals↗
PubMed1987

Cerebral atrophy and slow wave sleep of abstinent chronic alcoholics.

Although a considerable decrease of slow wave sleep (SWS) has been observed in abstinent chronic alcoholics, the under-lying mechanism is still obscure. In the present study CT scans and polysomnographic recording were repeatedly conducted in nine chronic alcoholics. SWS was remarkably reduced in all the patients, but it was slightly restored in six patients on the 6th month after abstinence. On the other hand, enlargement was observed in the cortical sulci, cerebral fissures and ventricles in these patients. The enlargement of the cortical sulci was improved in five patients, and four of the patients showed increase of SWS. Although enlargement of the cerebral fissures and ventricles was improved in a few patients, in most of the patients who showed improvement in the cortical sulci SWS was increased. The results indicate that the decrease in SWS in abstinent alcoholics may have resulted from the atrophy of the cerebral cortex.

Adult↗
PubMed1987

Structure determination of a quartet of novel tetraether lipids from Methanobacterium thermoautotrophicum.

The structures of three of the major polar lipids (PNL1a, GL1a, and PNGL1) of Methanobacterium thermoautotrophicum were elucidated. These lipids are derivatives of dibiphytanyl diglycerol tetraether (C40 tetraether; the proposed name is caldarchaeol). PNL1a is a C40 tetraether analog of phosphatidylethanolamine (proposed name: caldarchaetidylethanolamine). GL1a was identified as beta-D-glucopyranosyl-(1-6)-beta-D-glucopyranosyl C40 tetraether (diglucosyl caldarchaeol). PNGL1 has the polar head groups of both PNL1a and GL1a; one of the free hydroxyls of this tetraether is esterified with phosphoethanolamine while the other is linked to a glucosylglucose residue with the same structure as that of GL1a (proposed name: diglucosyl caldarchaetidylethanolamine). That is, PNL1a (aminophospholipid), GL1a (glycolipid), and PNGL1 (aminophosphoglycolipid) form structurally a quartet of lipids with the bare caldarchaeol. We propose a new systematic nomenclature of archaebacterial polar lipids in the "DISCUSSION," because the alternative names are too lengthy and laboratory designations of these lipids are not at all systematic. This nomenclature starts with giving the names archaeol and caldarchaeol to dialkyl diether of glycerol or other polyol and tetraether of glycerol or other polyol and alkyl alcohols, respectively, because these lipids are specific to archaebacteria. Phospholipids with a phosphodiester bond were named as derivatives of archaetidic acid or caldarchaetidic acid (phosphomonoesters of archaeol and caldarchaeol) by analogy with phosphatidic acid.

Ethanolamine↗
PubMed1987

Extraction and composition of polar lipids from the archaebacterium, Methanobacterium thermoautotrophicum: effective extraction of tetraether lipids by an acidified solvent.

The usual Bligh and Dyer method could extract only a small part of the lipids of Methanobacterium thermoautotrophicum. When the water in the solvent was replaced by 5% trichloroacetic acid, the lipid recovery reached the maximum level, which was 6 times higher than that by the former method. The use of HCl (2 M) or disruption of cells was also effective but prolonged extraction with the HCl-containing solvent caused degradation of some phosphoglycolipids. Twenty-three spots of polar lipids were detected on a thin-layer chromatogram of the total lipid. These were 10 phospholipids (18%), 6 aminophospholipids (17%), 3 aminophosphoglycolipids (15%), 2 phosphoglycolipids (31%), and 2 glycolipids (19%). The predominant polar lipids were a highly polar phosphoglycolipid (PGL1, 30%) and a glycolipid (GL1a, 16%). The other major lipids included an aminophospholipid (PNL1a, 9%), and an aminophosphoglycolipid (PNGL1, 7%). The complete structure determination of PNL1a, GL1a, and PNGL1 is described in the accompanying paper. Acetolysis of the total lipids followed by acid methanolysis was required for the complete cleavage of polar head groups, releasing core residues of diphytanyl glycerol diether (C20 diether) and dibiphytanyl diglycerol tetraether (C40 tetraether). A densitometric assay of a thin-layer chromatogram showed that the ratio of C20 diether and C40 tetraether was 1:14. GLC analysis of alkyl chlorides prepared from the total lipid by BCl3 treatment showed that phytanyl (C20), biphytanyl (C40), and unidentified alkyl chains accounted for 10, 83, and 7 mol% of the total alkyl chains, respectively. Strong acid hydrolysis of the macromolecular residue obtained after lipid extraction gave a significant amount of C40 tetraether, which had probably been bound covalently to other substances in the cells.

Ethers↗
PubMed1987

Direct effects of H2-receptor antagonists on airway smooth muscle and on responses mediated by H1- and H2-receptors.

Because it has been suggested that histamine H2-receptor antagonists may worsen airway constriction in asthmatic patients, we investigated the comparative effects of three histamine H2-receptor antagonists on guinea pig tracheal smooth muscle in vitro. When tested against resting tone, cimetidine, ranitidine and famotidine produced dose-related relaxation with pD2 values (negative log of ED50 for relaxation) (+/- SE, n; eq 5) of 3.20 +/- 0.04, 2.95 +/- 0.16 and 2.97 +/- 0.14, respectively. Concentrations that were below threshold for relaxation, did not elicit contraction. However, when the preparations were precontracted with histamine (10(-5)M), dose-response curves for relaxation were shifted to the right, and low-concentrations of all three histamine H2-antagonists augmented histamine-induced tone. When preparations were pretreated with cimetidine (10(-6) to 10(-4) M) and then tested for sensitivity to histamine, dose-response curves for histamine-induced contraction were shifted to the left (potentiated). These results provide further evidence for a modulatory effect of airway H2-receptors on the contractile response to histamine. In addition, since the concentrations associated with potentiation of histamine-induced contraction were about the same for all three H2-receptor antagonists (greater than or equal to 10(-5) M), our studies suggest a greater likelihood of airway constriction for the less potent H2-receptor antagonists that must be administered in higher clinical doses.

Animals↗
PubMed1987

Prevention of postischemic hypoperfusion after canine cardiac arrest by nicardipine.

We studied the effect of nicardipine (NC) on canine cerebral blood flow (CBF) after cerebral ischemia induced by cardiac arrest. Cerebral ischemia was produced by 10 min of electrically mediated ventricular fibrillation. An iv injection of NC (10 micrograms/kg) bolus was followed by continuous NC infusion (0.33 micrograms/kg X min) immediately after the circulation re-established itself. Local CBF was measured using the hydrogen-gas clearance method. The administration of NC maintained CBF at the pre-arrest level during postischemia, thus preventing the hypoperfusion observed in the control group with no NC. However, in the controls, CBF, reduced at 180 min after re-circulation, was not improved by NC infusion. Consequently, administering NC immediately after re-establishment of circulation may help maintain CBF during the postresuscitation period.

Animals↗
PubMed1987

An objective method of pulse diagnosis.

One component of Oriental medical diagnosis is pulse diagnosis. To make this method more objective, three pressure transducers were positioned over the radial artery and the absolute pressure of 50, 100 and 150 g was applied at three positions to simulate the classical pulse diagnosis. The transient pressure changes at the same absolute pressure were recorded. The pressure changes at the three positions were not equal even when the same absolute pressure was applied. Pressures were compared in superficial and deep locations, right and left wrist. The largest deflection was considered as excess and the smallest as depletion in twelve meridians.

Diagnostic Techniques and Procedures↗
PubMed1987

Inhibition of mitochondrial functions by margosa oil: possible implications in the pathogenesis of Reye's syndrome.

Margosa oil (MO), a fatty acid-rich extract of the seeds of the neem tree and a reported cause of Reye's syndrome, has been used in the induction of an experimental model of Reye's syndrome in rats. It has been reported that MO causes a decrease in in vivo mitochondrial enzyme activity similar to that seen in Reye's syndrome. We have attempted to uncover some of the biochemical mechanisms of MO's toxicity by examining its effect in vitro on isolated rat liver mitochondria. Male rat liver mitochondria were isolated by centrifugation; oxygen uptake, reduced forms of cytochrome b, c + c1, a + a3, and flavoprotein, intramitochondrial concentrations of acetyl coA, acid-soluble coA, acid-insoluble coA, and ATP content were measured after incubation with and without MO. Our results reveal that MO is a mitochondrial uncoupler. State 4 respiration was increased while the respiratory control ratio was decreased. The intramitochondrial content of ATP was also decreased. There were substantial changes in the reduction of the respiratory chain components after incubation of mitochondria with MO. This decelerative effect on mitochondrial electron transport was alleviated by the addition of coenzyme Q and/or carnitine. These effects of MO on mitochondrial respiration may be due to changes in fatty acid metabolism caused by MO as MO caused a shift in the proportion of acid-soluble or acid-insoluble coA esters. Supplementary therapy with L-carnitine and coenzyme Q may be useful in the management of MO-induced Reye's syndrome.

Animals↗
PubMed1987

Idiopathic pneumopericardium induced by forced coughing during coronary arteriography.

We report the induction of pneumopericardium by forced coughing during coronary arteriography in a 31-year-old male with anterior chest pain. The patient had no underlying disease and pneumopericardium could be reproduced by forced coughing. To our knowledge, there has been no report in the literature of pneumopericardium induced during coronary arteriography.

Adult↗
PubMed1987

Dilated cardiomyopathy: clinical significance of possible related factors.

The present study investigates the clinical significance of several possible causative or conditioning factors which have been proposed to be involved in the pathogenesis of dilated cardiomyopathy (DCM). By reviewing the medical records of 68 patients with DCM, we found a definite, and suggestive family history in 16%, and 28%, respectively, and antecedent flu-like symptoms in 43%. A history of hypertension was observed in 35%, habitual alcoholism in 49% and diabetic pattern on glucose tolerance test in 37%. We then classified the study patients into three groups; familial, myocarditic and acquired groups. The familial group showed advanced myocardial damage with the poorest prognosis. Abnormal T-cell subsets in this group suggested that genetically determined abnormal immune response is involved in the development of DCM. In the myocarditic group, endomyocardial biopsy demonstrated mononuclear cell infiltration in 53% and the myocardial damage and prognosis were of intermediate severity. The acquired group showed significantly more frequent histories of hypertension, habitual alcoholism or diabetes than their age- and sex-matched controls, suggesting that they developed the disease in association with these factors. The severity of hemodynamic impairment and myocardial damage was the least extensive and prognosis was relatively favorable in this group. These different clinical features in the three groups may provide evidence that these factors actually contribute to the development of myocardial damage in DCM and that the condition is a clinical syndrome associated with heterogeneous etiologies or conditioning factors. Determination and management of these factors would be of practical value in treating patients with DCM that has no established therapy against underlying etiologies.

Adult↗
PubMed1987

Effects of a mild and prolonged restriction in sodium or food intake on the circadian rhythm of aldosterone and related variables.

The effect of a mild reduction in dietary sodium intake (-30 mEq/24 hr) and body weight (-2 kg/2 months) on circadian rhythms of urinary aldosterone (UA), sodium (UNa), potassium (UK), creatinine (UC) and volume (UV) have been investigated in nine clinically healthy subjects. The mild reduction in dietary sodium is associated with: (1) a decrease in the 24-hr excretion rate of UNa, UK and UV, and an increased mesor of UA and UC; (2) a lowered extent of the circadian variation for UNa, UK, UV and a greater amplitude for UA and UC (3) a later crest in the temporal phase for UK, UA, UC, an earlier phasic wave for UNa. The mild reduction in calorie intake resulting in a body weight loss is associated with a more pronounced decrease in the 24-hr excretion rate of UNa and UK, and in the extent of circadian fluctuation for UNa. Peculiar events are: (1) the decreased 24-hr excretion rate for UA, and the increased mesor for UV; (2) the extent variability increased for UV, decreased for UC. Such effect may have a practical resonance for heuristic physiology since the role of dietary sodium and food intake has been better clarified. Dietary sodium and food can be regarded as 'chronomodulatory agents' for the adrenal cortex since their adrenotropic influence is extended to the tonic as well as phasic secretion of aldosterone.

Adult↗
PubMed1987

Partial deficiency of subunits in complex I or IV of patients with mitochondrial myopathies.

Subunits of Complexes I, III, IV, and V from skeletal muscle mitochondria isolated from four patients with mitochondrial myopathies were analyzed by immunoblotting. A deficiency was observed in Complex I or IV, or in both. The patterns of deficiency of subunits of each complex were similar both in patients with deficiency of a single complex and in patients with combined deficiency of the two complexes. The deficiency of any of these subunits was only partial, and no abnormalities in the electrophoretic mobilities of the subunits were observed. These results suggest that the deficiency of Complex I or IV in these patients are based on similar molecular defects which lead to decreased levels of these subunits.

Adolescent↗
PubMed1987

Surface marker studies on activated peripheral blood lymphocytes in idiopathic dilated cardiomyopathy.

Expression of interleukin 2 (IL-2) receptor on peripheral blood lymphocytes after stimulation with concanavalin A (Con A) or anti-T3 monoclonal antibody was analyzed in patients with dilated cardiomyopathy (DCM) in order to clarify the abnormalities of lymphocyte activation mechanism in DCM. The expression of IL-2 receptor after the stimulation with either Con A or anti-T3 monoclonal antibody was found to be reduced in the patients with DCM when the results were compared with those of controls. A significant correlation was noticed between the expression of IL-2 receptor after Con A stimulation and T4+/T8+ cell ratio, and between the expression of IL-2 receptor after anti-T3 monoclonal antibody stimulation and the left ventricular end-diastolic pressure (LVEDP). The results suggest that there are abnormalities of lymphocyte activation in DCM and that the alteration may be associated with the cause or clinical conditions of DCM.

Adult↗