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Biomedical subjects

M Koga

Publications and source records attributed to M Koga.

At least 271 records · Page 15Linked to original sources
PubMed1995

Activation of renal dopamine system by physical exercise.

Physical exercise is one of the life-style modifications used for lowering blood pressure. Except for diminished norepinephrine spill over, the mechanism by which physical exercise exerts its effects was not known. Based on our preliminary finding that the reduction of blood pressure was inversely correlated to the baseline plasma renin activity, we have consequently revealed that mild exercise reduces plasma volume and hence the cardiac index. In order to elucidate the mechanism, we have investigated all possible parameters relevant to plasma volume regulation. Among them, urinary free dopamine and urinary active kallikrein increased in the early stages (weeks 2-4) while atrio-natriuretic factor (week 4) and endogeneous ouabain-like substance (EOLS) consequently (weeks 7-10) decreased. Serum taurine increased and plasma norepinephrine decreased in the late stages. The conclusion reached is that mild exercise seems to first activate the renal dopamine and kallikrein systems and second trigger other mechanism, such as an increase in taurine and decreases in EOLS and norepinephrine.

Adult↗
PubMed1995

Determination of cardiac output by echocardiography.

To determine cardiac output using a non-invasive manner, we examined correlations between cardiac output values determined by ten different kinds of echocardiography and those determined by the thermodilution method. With respect to the M-mode method, one of the rotary ellipsoid approximation methods using a short axial section at the papillary muscular level, namely the GIBSON method, showed the highest correlation with the thermodilution method (r = 0.84; p < 0.01). Among the Doppler mode method, the highest correlation (r = 0.93; p < 0.01) was exhibited by the method in which the area of the luminal section of the outflow tract was accurately measured using a trace method on a short axial cross section of the tract flowing out of the left ventricle. These findings suggest that it is possible to determine cardiac output by echocardiography in the same was as with the thermodilution method. Moreover, non-invasive determination methods using echocardiography have been confirmed to be highly beneficial in clinical settings.

Animals↗
PubMed1995

[The effects of fitness-type exercise on iron status and hematological status for female college students].

Forty-two female college students underwent fitness-type exercise over a 13 week period. The students exercised an average of two times a week for 30 minute periods at 50% levels of VO2 . max. Iron status and hematological laboratory data were monitored at three points in time; at the initiation of exercise, at the termination of exercise and 3 months later. Serum ferritin levels in a third of the students were lower than 12ng/ml. Red blood cell counts decreased during exercise, and returned to the pre-exercise levels 3 months later. The number of circulatory reticulocytes and mean corpuscular hemoglobin concentration were increased significantly after the exercise and the effects were still observed 3 months later, independent of the iron status. In the lower ferritin group, erythropoietin levels decreased significantly during the post-exercise period. The average serum ferritin levels while showing no significant changes during exercise, increased significantly during the post-exercise period, in the normal ferritin group. We discussed possible mechanisms, among them iron metabolism, by which physical training may facilitate erythropoiesis. However, no definite conclusions have been reached.

Adult↗
PubMed1995

[Isolated aortic valve regurgitation due to degeneration of the valve leaflet--a clinical study].

From 1989 through 1993 thirty-eight patients underwent aortic valve replacement at our institution for isolated aortic regurgitation (AR) caused by idiopathic degeneration of the valve. There were 32 male and 6 female patients aged between 33 and 74 years with a mean of 59 years. Preoperative New York Heart Association functional class, cardiothoracic ratio, cardiac index, and left ventricular end-diastolic pressure were 2.6, 57%, 3.1 L/min/m2, and 18 mmHg, respectively. Cross-sectional echocardiography clarified aortic valve prolapse in seven patients. Excised valvular cusps were thin, redundant and translucent in association with cuspal fenestration in 9 cases and idiopathic commissural disruption in 2 cases. Histological study revealed significant disruption of the fibrosa and cystic degeneration of the spongiosa layer filled with mucopolysaccharide. Actuarial survival rate, including 3 operative deaths, was 89% at 3 years after AVR with no apparent valve related complications. Idiopathic degeneration of the aortic valve is a common cause of AR, occurring in half of the surgically treated patients. We emphasize the importance of this lesion as a cause of AR.

Adult↗
PubMed1995

Deuterium MR in vivo imaging of the rat eye using 2H2O.

In vivo deuterium MR imaging (2H MR) was investigated in rats after intraperitoneal administration of deuterated saline, and a dynamic study of the water movement in rat eyes was performed. Deuterium MR imaging was carried out by means of a gradient-echo (GRE) and a spin-echo (SE) pulse sequence. The rat eye was imaged in 2H MR more selectively by SE than by GRE, but a lower signal-to-noise ratio was obtained in 2H MR imaging using the SE sequence. The MR signal intensity of the rat eye was followed by a 3-compartment model, which enabled determination of the flow rate constant of the water in the eye (0.359/min). Deuterium MR imaging is useful to visualize the dynamic change of water in rat eyes using 2H MR at the same magnetic field (2 T) that can also be used for conventional MR imaging in humans.

Animals↗
PubMed1995

[Management of patients with closing aortic dissection].

Acute aortic dissection is a catastrophic event requiring immediate diagnosis and definitive treatment, while the clinical characteristics of closing aortic dissection are not well known. From Jan. 1991 through Dec. 1994 a total of 24 patients with closing aortic dissection (CAD) was managed at our institution. There were 19 men and 5 women, ranging in age from 49 to 74 years with a mean of 65 years. All patients presented with a sudden onset of severe chest and back pain. Twenty patients had a history of hypertension with a wide mediastinal silhouette on chest X-ray. The diagnosis of CAD was established by contrast computed tomographic (CT) scans in all patients with no evidence of patent false lumen. The descending thoracic aorta was involved in 17 patients and the ascending in 5. Conservative medical management was initially attempted for all. Seven patients (Stanford type A/B: 2/5) ultimately required surgical intervention, and 2 patients died. The follow-up was 100% complete with a mean term of 14.6 months. The overall survival rate was 74% at 3 years after the initial presentation. Based on our clinical experience, all patients with CAD need careful antihypertensive therapy and frequent follow-up studies to assess the aorta.

Aged↗
PubMed1995

[Farber's lipogranulomatosis].

Farber's lipogranulomatosis is a disorder of lipid metabolism due to deficiency of lysosomal acid ceramidase. Since Farber described the first case in 1947, at least 50 cases have been reported. Clinical manifestations include progressive arthropathies with periarticular swelling, hoarse voice, multiple subcutaneous nodules and growth and developmental retardation. The histological findings indicate granuloma formation with infiltrated lipid-laden macrophages and fibroblasts. Curvilinear tubular structures, so-called "Farber bodies", are observed on electron microscopy. The specific diagnosis can be made by demonstration of a deficiency of acid ceramidase, ceramide accumulation in tissue or characteristic morphological features on biopsy or postmortem specimens. Bone marrow transplantation may be effective during the early stage of this disease.

Acid Ceramidase↗
PubMed1995

Synthesis and properties of 5-fluorouracil oligonucleotides.

Oligonucleotides of 5-fluoro-2'-deoxyuridine (FUdR) 1 and 5-fluorouridine (FUR) 2 have been prepared by the standard phosphoramidite method. Homo oligomers (24 mer) of 1, 2 and hetero oligomers of those will be described.

Antimetabolites, Antineoplastic↗
PubMed1995

A new type of advanced third-stage larvae of the genus Gnathostoma in freshwater eels, Fluta alba, from Nakhon Nayok, central Thailand.

Five advanced third-stage larvae of a newly identified type of genus Gnathostoma were collected from freshwater eels, Fluta alba, which were purchased at a market in Nakhon Nayok, central Thailand. The most remarkable characteristic of the newly identified larvae was the larger body size compared with any other larva of Gnathostoma spp. They were also distinguishable from other species by the shape of their hooklets, which branched in a complex manner at the base: this had not been previously observed in any other larval Gnathostoma. The newly described larvae had an average number of 44.5, 45.0, 49.0 and 55.1 hooklets on the head-bulb from the first to the fourth rows, respectively, which were comparable to those of larval G. spinigerum. However, the average number of nuclei in each intestinal cell was 2.21 and fewer than those of the larvae of G. spinigerum. These results suggest that the new type of larvae belong to either G. vietnamicum, G. malaysiae, or constitute a new species of the genus Gnathostoma.

Animals↗
PubMed1994

Unsaturated fatty acids are required for continuous proliferation of transformed androgen-dependent cells by fibroblast growth factor family proteins.

Increase in dietary fat intake has been reported to be associated with progression of hormone-dependent cancers. To explore its mechanism, we examined the effects of fatty acids on the growth of androgen-dependent SC-3 cells cloned from mouse mammary cancer (Shionogi carcinoma 115). Their androgen-dependent growth was potentiated by linoleic acid in the defined medium. The effect of linoleic acid on fibroblast growth factor (FGF)-dependent growth was also addressed because androgen had been demonstrated to exert its mitogenic activity on SC-3 cells through an induction of the unique FGF family protein termed as androgen-induced growth factor. Exposure of SC-3 cells to basic FGF or androgen-induced growth factor exhibited only transient growth response. However, simultaneous addition of linoleic acid to the medium sustained the proliferation of FGF-stimulated, but not FGF-unstimulated, cells, although linoleic acid did not exert the significant effect on the process of S-phase entry of basic FGF-stimulated cells. Palmitoleic acid and oleic acid appeared to exert the actions similar to linoleic acid, while stearic acid was without any effect. Neither cyclooxygenase inhibitor nor 5-lipoxygenase inhibitor could block the growth-promoting ability of linoleic acid. Linoleic acid also enhanced their anchorage-independent growth in the presence of basic FGF. These results indicate that these unsaturated fatty acids play a role in sustaining the proliferation of FGF-stimulated SC-3 cells.

Animals↗
PubMed1994

Evolution of the hepatitis B virus gene during chronic infection in seven patients.

We analyzed the evolution of the precore/core gene of hepatitis B virus (HBV) over a period of 6 to 11 years in seven patients with chronic HBV infection, who exhibited a variety of clinical features. Sequence analysis revealed the following results: (1) HBeAg to anti-HBe seroconversion was correlated roughly with the occurrence of precore-defective mutants, and several years appeared to be required for complete replacement of wild types by mutants; (2) core gene mutations preceded precore-defective mutations and tended to increase with time, although not cumulatively. They occurred not only during serum alanine aminotransferase (ALT) elevations but also after ALT returned to normal; (3) ALT fluctuations appeared to subside with complete replacement of the wild type by the mutant type and/or substantial accumulation of core gene mutations; (4) unexpectedly, the anti-HBe-positive "healthy" carrier was found to harbor the wild type precore gene, as did the HBeAg-positive "healthy" carrier; however, the core gene of the former evolved at a rapid rate; and (5) a partial deletion was recognized in the core gene at the onset of fatal hepatic failure in one patient. Thus, the precore/core mutation was closely related with the clinical features in the patients.

Adolescent↗
PubMed1994

Differentiation of herpes simplex virus 1 and 2 in cerebrospinal fluid of patients with HSV encephalitis and meningitis by stringent hybridization of PCR-amplified DNAs.

Differentiation of herpes simplex virus (HSV) types 1 and 2 in cerebrospinal fluid of 17 patients with serologically diagnosed HSV encephalitis and meningitis or acute limbic encephalitis was determined by stringent hybridization of polymerase chain reaction--amplified DNAs. Ten of 17 patients were positive; six with HSV 1 isolates and four with HSV 2 isolates. We detected HSV type 1 in two cases of meningitis, although meningitis is generally thought to be caused by type 2. Additionally, HSV type 2 was found in one case of acute adult encephalitis, which is generally due to HSV type 1. HSV DNAs could be detected for over 1 month after onset, although our patients included several prolonged and recurrent cases. HSV DNA genomes were not detected in three cases of acute limbic encephalitis. Our study indicates that this method can be used for type differentiation in HSV CNS infections.

Adolescent↗
PubMed1994

Effects of hypo- and hyperglycemia on brain energy metabolites in mice exposed to carbon monoxide.

Hypoglycemia and hyperglycemia were induced in mice by fasting and by injecting with glucose, respectively. These and normally fed (normoglycemic) animals were exposed to 0.5% carbon monoxide (CO) for 10 min. This altered concentrations of energy metabolites in the brain, including decreases in phosphocreatine (PCr) and increases in creatine and lactate. The only difference between normoglycemic and hypoglycemic mice was lower lactate in the latter. In hyperglycemic mice, PCr and ATP were better preserved during CO exposure and lactate was lower than in normoglycemic mice. Blood glucose concentrations correlated well with glucose but not with lactate in the brain. Thus, moderate hypo- or hyperglycemia seems not to exacerbate CO-induced alterations of brain energy metabolism.

Animals↗
PubMed1994

Facilitation of autonomous phenotype acquisition in androgen-dependent Shionogi carcinoma 115 cells by transfection of androgen-induced growth factor expression vector.

Androgen-induced growth factor (AIGF) is an autocrine growth factor for androgen-dependent SC-3 cells, which is induced by androgen stimuli. To elucidate the mechanism of the progression from hormone-dependent to -independent tumor, we transfected an expression vector of cDNA encoding AIGF into SC-3 cells and established a stable transfectant (A1) expressing AIGF. A1 cells showed enhanced DNA synthesis. This enhanced DNA synthesis was blocked by exposing the cells to AIGF antisense oligonucleotides, heparin, or suramin, indicating that enforced AIGF expression is responsible for the increase in DNA synthesis. However, A1 cells did not grow in serum-free medium unless stimulated with androgen. Recloning from A1 cells in semi-solid agar supplemented with fetal calf serum but without androgen quickly generated an autonomous subline that was able to grow rapidly in the serum-free medium irrespective of androgen stimulus. Mock-transfected SC-3 cells failed to form any colony under identical conditions. These results suggest that stable expression of AIGF alone is not sufficient for, but facilitates the conversion of SC-3 cells from androgen-dependent to -independent phenotype.

Androgens↗