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Biomedical subjects

H Ohta

Publications and source records attributed to H Ohta.

At least 397 records · Page 22Linked to original sources
PubMed1994

Effect of conformation of the substrate on enzymatic decarboxylation of alpha-arylmalonic acid.

The configuration and conformation of a compound are critical factors that determine whether it can be accepted by an enzyme as a substrate or not. We have examined enzyme-catalyzed decarboxylation of some alpha-substituted malonic acids and proposed that the syn-periplanar conformation is required for the substrates to be bound to the active site of the enzyme. Theoretical calculation of potential energy surfaces also supports the conclusion from experimental results.

Alcaligenes↗
PubMed1994

Endoscopic ultrasonography in the diagnosis of extraluminal compressions mimicking gastric submucosal tumors.

We evaluated the diagnostic usefulness of endoscopic ultrasonography (EUS) in 19 patients with extragastric compression. In these 19 cases, the causes of the compression were normal organs or structures in 16 cases (splenic artery 7, spleen 5, normal pancreas two, gall-bladder one, colon one) and extraluminal tumors in three cases (two hepatic hemangiomas, one neurogenic tumor of the omentum minor). In 12 of these 19 cases, the site of the submucosal compression was located in the upper part of the stomach. All three tumors were confirmed by other procedures, and in the remaining 16 patients with compression by normal organs or structures, negative follow-up results (mean: 14 months) supported the absence of a true submucosal tumor. EUS was 100% accurate in the differentiation of an extragastric compression from a submucosal tumor, and in the identification of the compressing organ. EUS was also far superior to other procedures, such as ultrasonography and CT. It significantly shortens the diagnostic procedure, especially in patients with compressions by normal extraluminal structures, making other diagnostic modalities unnecessary.

Adult↗
PubMed1994

HN proteins of human parainfluenza type 4A virus expressed in cell lines transfected with a cloned cDNA have an ability to induce interferon in mouse spleen cells.

Primary monkey kidney cells infected with human parainfluenza type 4A virus (HPIV-4A) were treated with various concentrations of formaldehyde. Formaldehyde (0.275%) treatment completely blocked virus production. However, when mouse spleen cells were cocultured with the fixed virus-infected cells, interferon was produced in the culture fluid. On the other hand, when mouse spleen cells were incubated with the fixed virus-infected cells in the presence of anti-HPIV-4A antiserum or a mixture of anti-HN protein monoclonal antibodies, interferon activity could scarcely be detected in the culture fluid. These findings indicated that the fixed virus-infected cells had an ability to induce interferon in mouse spleen cells and that the HN protein was related to interferon induction. Subsequently, a recombinant plasmid was constructed by inserting the cDNA of the HN gene of HPIV-4A into a pcDL-SR alpha expression vector. Mouse spleen cells produced interferon when cocultured with COS7 cells transfected with the recombinant plasmid, but did not when cocultured with COS7 cells transfected with the vector alone. Furthermore, we established HeLa cells constitutively expressing HPIV-4A HN (HeLa-4aHN cells) or F protein (HeLa-4aF cells). Type I (alpha/beta) interferon was detected in culture fluids of mouse spleen cells with HeLa-4aHN cells, but was not detected in those with HeLa-4aF cells. Therefore, it was concluded that the HN glycoproteins on the cell surface were sufficient for interferon induction to occur.

Animals↗
PubMed1994

Metabolic and energetic aspects of the growth response of Streptococcus rattus to environmental acidification in anaerobic continuous culture.

Streptococcus rattus, a serotype b strain of mutans streptococci, was grown in an anaerobic glucose-limited chemostat. The molar growth yield of glucose [Yglucose, g dry wt (mol glucose)-1] together with the maximum growth yields (Ymax) and maintenance coefficients for glucose utilization and calculated ATP generation were estimated as a function of pH. When the pH was lowered from 7.0 to 5.0, Yglucose decreased, with a concomitant gradual change in the composition of the end product from a mixture of formate, acetate and ethanol to one mostly of lactate. Whereas the Ymax for glucose decreased without any change in the Ymax for ATP on acidification, both of the maintenance coefficients markedly increased. Kinetic and immunochemical examinations indicated the presence of an F1F0-type proton-translocating ATPase in the membrane fraction prepared from bacterial cells grown under acidic conditions; no detectable level of the enzyme was found in cells grown at neutral pH. However, when incubated with glucose under non-growing conditions, these acid-adapted and unadapted cells showed an insignificant difference in the ability to maintain the intracellular pH alkaline relative to the acidic environments. These results suggest that the organism responds and adapts to environmental acidification by sacrificing some energy cost in terms of both the efficiency of glucose utilization to generate ATP and the extra maintenance required to continue biomass production as efficiently as under neutral pH.

Adenosine Triphosphate↗
PubMed1994

Baroreflexes influence autoregulation of cerebral blood flow during hypertension.

Cerebral blood flow (CBF) is autoregulated at mean arterial pressures (MAP) ranging from approximately 50 to 150 mmHg. When MAP exceeds the upper limit, autoregulation breaks through, vasodilatation occurs, and CBF increases rapidly. Earlier studies have shown that the arterial baroreflex does not influence autoregulation. However, CBF may rise to a lesser degree during abrupt hypertension immediately after interruption of the baroreceptor reflex than it would at comparable levels of blood pressure in intact animals. Generally this shift of the breakthrough point has been attributed to an increase in sympathetic nerve activity immediately after sinoaortic denervation. We hypothesized that denervation of arterial baroreceptors would blunt vasodilatation during slow controlled increases of arterial pressure, and we sought to determine whether sympathetic nerves contributed to regulation of CBF during hypertension in baroreceptor-denervated animals. Thirty-eight rats were studied to determine whether sinoaortic denervation affected autoregulation or breakthrough during acute hypertension. In five intact rats, when arterial pressure was raised by phenylephrine to 155 +/- 4 mmHg, cerebrovascular resistance fell by 60% and CBF increased by 434%. After interruption of the baroreflex in six rats, such dramatic increases in CBF with breakthrough did not occur despite greater increases in MAP (to 185 +/- 2 mmHg). Similar results were obtained when arterial pressure was raised by infusion of arginine vasopressin in four intact and three denervated rats. The effects of baroreceptor reflex interruption were not significantly affected by bilateral removal of the superior cervical ganglia. Rates of rise of MAP and increases of pulse pressure were equivalent between groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Both NMDA and non-NMDA receptors in the NTS participate in the baroreceptor reflex in rats.

In this study, we determined whether either N-methyl-D-aspartate (NMDA) receptors or non-NMDA receptors in the nucleus tractus solitarii (NTS) participate in the baroreceptor reflex in rats. Microinjection of an NMDA receptor antagonist, MK-801, and a non-NMDA receptor antagonist, 6,7-dinitroquinoxaline-2,3-dione, into the NTS decreased the sensitivity of the baroreceptor reflex by 51 and 41%, respectively. Simultaneous administration of both agents further reduced the sensitivity of the baroreceptor reflex to 28% of control. A competitive NMDA receptor antagonist, 2-amino-5-phosphonovaleric acid, also attenuated reflex bradycardia or tachycardia elicited by a single dose of phenylephrine or nitroprusside, respectively. Specificity of each antagonist's effects was supported by selective blockade of depressor responses produced by agonists that act at the NMDA and non-NMDA receptors, respectively. Results of this study indicate that both non-NMDA- and NMDA-sensitive receptors are involved in baroreceptor reflex transmission in the NTS.

2-Amino-5-phosphonovalerate↗
PubMed1994

Hemodynamic effects elicited by stimulation of the nucleus tractus solitarii.

Microinjection of the excitatory amino acid L-glutamate into the nucleus tractus solitarii (NTS) elicits decreases in arterial pressure and heart rate. In the present study, we sought to determine the regional hemodynamic effects that were correlated with changes in arterial pressure and heart rate produced by stimulation of the NTS. In anesthetized rats, blood flow in the renal (RBF), superior mesenteric (MBF), and hindquarter (HBF) vascular beds was measured by pulsed Doppler flowmeters. Relative vascular resistances (RVR, MVR, and HVR) were calculated by dividing mean arterial pressure (mm Hg) by the Doppler shift (kHz). Microinjection of L-glutamate into the NTS caused rapid, transient, dose-related decreases in mean arterial pressure and heart rate. MVR and RVR were minimally changed immediately after injections, but both demonstrated delayed dilatation. In contrast, HVR fell immediately but demonstrated delayed constriction. Identical changes occurred in intact rats and in those with interruption of the baroreflex by sinoaortic denervation. Ganglionic blockade with hexamethonium abolished virtually all L-glutamate-induced responses. This study suggests that NTS neurons exert differential effects on renal, mesenteric, and hindquarter vascular beds and that glutamate-induced regional hemodynamic changes are mediated predominantly through autonomic pathways.

Animals↗
PubMed1994

Estrogen deficiency stimulates B lymphopoiesis in mouse bone marrow.

We have found that an estrogen deficiency causes a marked increase in bone marrow cells. To examine the effect of estrogen on hemopoiesis, we characterized the increased population of bone marrow cells after ovariectomy (OVX). In OVX mice, the percentage of myeloid cells and granulocytes was decreased, whereas that of B220-positive B lymphocytes was selectively increased 2-4 wk after surgery. The total number of myeloid cells and granulocytes did not change appreciably, but that of B220-positive cells was greatly increased by OVX. When OVX mice were treated with estrogen, the increased B lymphopoiesis returned to normal. B220-positive cells were classified into two subpopulations, B220low and B220high. The majority of the B220low cells were negative for the IgM mu chain, whereas most of the B220high cells were mu-positive. OVX selectively increased the precursors of B lymphocytes identified by B220low. mu-negative phenotype, suggesting that an estrogen deficiency stimulates accumulation of B lymphocyte precursors. When bone marrow-derived stromal cells (ST2) were pretreated with estrogen then co-cultured with bone marrow cells in the presence of estrogen, the stromal cell-dependent B lymphopoiesis was greatly inhibited. The present study suggests that estrogen plays an important role in the regulation of B lymphocyte development in mouse bone marrow.

Animals↗
PubMed1994

Case report: splenic vein aneurysm--report of a lesion that progressively expanded.

A case of splenic vein aneurysm is reported. The patient was diagnosed as having a cirrhotic liver with portal hypertension. Computed tomography and angiography demonstrated a splenic vein aneurysm with saccular dilatation. The splenic vein aneurysm increased in size as the hepatic cirrhosis deteriorated; however, there were no complications such as rupture or thrombosis. To our knowledge this is the first report describing the development of a portal system aneurysm.

Aneurysm↗
PubMed1994

Long-term follow-up of mitomycin C nephropathy.

Two cases of mitomycin C nephropathy, which occurred after postoperative chemotherapy for advanced gastric cancer, were followed up for 6 (case 1) and 10 years (case 2). Hemolytic uremic syndrome developed 68 days (case 1) and 160 days (case 2) after the last administration of MMC with a total dose of 60 mg (case 1) and 40 mg (case 2). Serum creatinine levels were normalized in case 1 and they remained at about 2 mg/dl in case 2. Hyporeninemic hypoaldosteronism was transiently seen in case 2. These data suggest that recovery from the acute phase of hemolytic uremic syndrome leads to a good long-term prognosis in MMC nephropathy.

Hemolytic-Uremic Syndrome↗