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Biomedical subjects

M Higuchi

Publications and source records attributed to M Higuchi.

At least 505 records · Page 28Linked to original sources
PubMedDate not supplied

Influence of one bout of vigorous exercise on ascorbic acid in plasma and oxidative damage to DNA in blood cells and muscle in untrained rats.

We investigated the influence of a single exhaustive bout of downhill running on oxidative damage to DNA and changes of antioxidant vitamin concentrations in rats. Plasma vitamin E levels were unchanged up to 48 hr postexercise. However, plasma ascorbic acid (AA) levels increased after the exercise, then decreased thereafter. This increase corresponded to a marked decrease in AA concentration in the adrenal glands. The activity of hepatic l-gulono-gamma-lactone oxidase, which catalyzes AA synthesis, was unaltered after the exercise. The weight of the adrenal glands was significantly increased 24 hr postexercise. These results indicate that the change in the plasma AA concentration after vigorous exercise was due mainly to the release of AA from the adrenal glands. The plasma creatine phosphokinase (CPK) activity and white blood cell (WBC) count increased 3 to 6 hr postexercise. Over this same period, a marker of oxidative DNA damage, 8-hydroxydeoxyguanosine in DNA, increased in the WBC, but not in the foreleg muscle. Lipid peroxide and vitamin E levels were also unchanged in the foreleg muscle. There was a positive correlation between CPK activity in the plasma and DNA damage in the WBC, suggesting that the DNA damage in the WBC was closely related with muscle damage due to exercise.

Journal Article↗
PubMedDate not supplied

Effects of nitroglycerin on regional myocardial function in the underperfused canine heart.

Effects of nitroglycerin (3 micrograms/kg/min i.v.) on regional myocardial contractility during acute coronary stenosis were studied in open-chest dogs using a strain-gauge arch. Stenosis-induced stepwise decreases in coronary perfusion pressure (CPP) at less than 40 mm Hg correspondingly reduced contractility in the underperfused area and increased the left ventricular end-diastolic pressure (LVEDP). Nitroglycerin caused significant increases in contractility, along with decreases in arterial and left ventricular pressures; at stenosis-induced CPP less than 30 mm Hg, contractility in the underperfused are fell precipitously below the control, while LVEDP increased. When nitroglycerin infusion under coronary stenosis (CPP of 40 mm Hg) decreased CPP to less than 30 mm Hg, contractility fell. When CPP greater than 30 mm Hg was maintained, contractility increased and LVEDP decreased. In conclusion, at least in the absence of well-developed collateral circulation, the critical level of CPP was 40 mm Hg for contractility and LVEDP without nitroglycerin, which shifted to 30 mm Hg with the addition of nitroglycerin. Nitroglycerin resulted in a significant increase in plasma catecholamines, and the increase in contractility diminished with propranolol, indicating participation of beta-adrenoceptor in the positive inotropic effect of nitroglycerin. However, catecholamines at high concentrations probably further aggravated the impaired cardiac function at CPP less than 30 mm Hg.

Animals↗
PubMedDate not supplied

Postnatal histogenesis of the cartilage plate of the spinal column: electron microscopic observations.

The cartilage plate in the vertebral columns in mice, from birth to 45 weeks of age, were examined by light and electron microscopy. At the day of birth, the intermediate part of the vertebral body consisted of bone, and its cranial and caudal parts were composed of thick cartilage. The cartilage was divided into an outer and an inner zone, according to the shape and arrangement of chondrocytes. In the deep portion of the outer zone, calcification developed from one week, and ossification appeared at eight weeks of age. The matrix in the superficial layer of the outer zone remained metachromatic during the development of the vertebral body. The inner zone of the cartilage showed columnar arrangements of chondrocytes and a metachromatic matrix like cartilaginous growth plates in long bones. Thus, vertebral bodies show development similar to that of long bones. The findings suggest that histogenetically the cartilage plate belongs to the vertebral body but not to the intervertebral disc and that age-related changes in the cartilage plate are concerned with age-related degenerative changes of the nucleus pulposus.

Animals↗
PubMedDate not supplied

Postmortem changes in ultrastructures of the mouse intervertebral disc.

To elucidate the effects of nutrition and oxygen deficiencies on the intervertebral disc, cell components of mouse intervertebral discs and their postmortem changes were observed by electron microscopy. The annulus fibrosus could be divided into an inner and outer region. The main cell components of the annulus fibrosus were fibroblast-like cells in the outer region and chondrocytes in the inner region. The nucleus pulposus consisted of massively packed notochordal cells. The cartilage plates could also be divided into two zones: articular cartilage and growth cartilage containing chondrocytes. Postmortem degenerative changes proceeded from the peripheral to the central parts of the intervertebral disc, ie, showing degeneration of first the fibroblast-like cells, next the chondrocytes, and finally, the notochordal cells. The findings suggest that cells situated at the periphery predominantly depend on aerobic metabolism, whereas the cells situated more centrally depend on anaerobic metabolism. Furthermore, postmortem changes of the nucleus pulposus were similar to age-related changes. The age-related changes or degeneration in the intervertebral disc appear to be related to deficiencies of nutrition or oxygen caused by changes in structures of the disc and the surrounding tissues.

Animals↗
PubMedDate not supplied

CT of acquired abnormalities of the portal venous system.

Computed tomography (CT), including biphasic contrast material-enhanced helical dynamic scanning and three-dimensional CT angiography, is useful in evaluating acquired abnormalities of the portal venous system. At contrast-enhanced CT, portal venous thrombus usually manifests as low-attenuation intraluminal lesions combined with enlargement of the affected portal vein. Cavernous transformation, a masslike network of intertwined veins that provides an alternative pathway for a stenosed or occluded portal vein, is depicted as multiple, periportal vascular structures. At helical dynamic CT, arterioportal shunts manifest as early enhancement of the affected portal vein, transient hyperperfusion abnormalities with lobar or segmental distribution, or transient wedge-shaped enhancement peripheral to the tumor. In patients with portosplenic venous invasion by malignant neoplasms, peripancreatic or perigastric veins may dilate if they function as hepatopetal collateral veins. In patients with portal hypertension, a variety of hepatofugal collateral pathways can develop, including esophageal, paraesophageal, coronary gastric, inferior phrenic, paraumbilical, abdominal wall, splenorenal, gastrorenal, retrocaval, and mesocaval collateral pathways. An understanding of the varied CT appearances of acquired abnormalities of the portal venous system will allow more definitive diagnosis and help avoid false diagnosis of disease.

Collateral Circulation↗
PubMedDate not supplied

Plasmid DNA satellite bands seen in lysates of Streptococcus mutans that form insoluble extracellular polysaccharides.

A satellite band of plasmid DNA was seen in cell lysates prepared from two strains of S mutans using buoyant-density equilibrium centrifugation. Mutants, defective in their ability to synthesize insoluble extracellular polysaccharides, showed no detectable satellite DNA band when prepared by the same procedure. These mutants were induced by treatment with EB, acridine orange, or SDS, which are known to be effective agents for the elimination of extrachromosomal genetic inheritance. The derived mutants produced more soluble polysaccharides from sucrose than their parent strains. The decreased ability to synthesize insoluble polysaccharides was related to both glucan and fructan formation. These findings suggest that the plasmid DNA of the S mutans strains genetically controls formation or activity of the enzymes responsible for synthesis of extracellular insoluble glucan or fructan.

Bacteriolysis↗
PubMedDate not supplied

Comparative effects of the calcium antagonist isradipine and some other dihydropyridine derivatives on regional blood flow in anesthetized open-chest dogs.

The effects of isradipine (PN 200-110), isopropyl 4-(2,1,3-benzoxadiazol-4-yl)-1,4-dihydro-5-methoxycarbonyl-2,6-dim ethyl-3- pyridinecarboxylate, on some cardiovascular parameters and regional blood flow were compared with those of other dihydropyridine derivatives in anesthetized open-chest dogs. Intravenous (i.v.) administrations of isradipine 3 and 10 micrograms/kg, nifedipine 10 micrograms/kg, nicardipine 10 micrograms/kg and nisoldipine 10 micrograms/kg, decreased aortic blood pressure and increased aortic (AoF), vertebral (VBF) and coronary blood flow (CBF), but did not affect heart rate and left ventricular end-diastolic pressure. Renal blood flow was reduced by isradipine 10 micrograms/kg and nifedipine 10 micrograms/kg, but was not influenced by isradipine 3 micrograms/kg, nicardipine 10 micrograms/kg and nisoldipine 10 micrograms/kg. Left ventricular dP/dt was increased by isradipine 3 micrograms/kg, nicardipine 10 micrograms/kg and nisoldipine 10 micrograms/kg, but remained essentially unchanged following isradipine 10 micrograms/kg and nifedipine 10 micrograms/kg. The increase in AoF, VBF and CBF lasted 5-9 min following nifedipine 10 micrograms/kg or nicardipine 10 micrograms/kg, 17-30 min following nifedipine 10 micrograms/kg or nicardipine 10 micrograms/kg, 17-30 min following nisoldipine 10 micrograms/kg, and 16-44 min following isradipine 3 micrograms/kg i.v., but persisted for at least 60 min following isradipine 10 micrograms/kg. Under the experimental conditions and at the doses used in this study, all 4 drugs reduced total peripheral resistance as well as resistance in the vertebral, coronary and renal vascular beds. The results suggest that isradipine exerts cardiovascular effects similar to other calcium antagonists of the dihydropyridine group, but possesses a longer duration of action and shows a greater specificity in reducing coronary vascular resistance than nifedipine, nicardipine and nisoldipine.

Anesthesia↗