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Biomedical subjects

M Minato

Publications and source records attributed to M Minato.

At least 37 records · Page 2Linked to original sources
PubMed1994

Indonesian medicinal plants. X. Chemical structures of four new triterpene-glycosides, gongganosides D, E, F, and G, and two secoiridoid-glucosides from the bark of Bhesa paniculata (Celastraceae).

Four new triterpene-glycosides, named gongganosides D (4), E (5), F (6), and G (7), and two new secoiridoid-glucosides, (7R)-7-caffeoyloxysweroside (8) and (7S)-7-caffeoyloxysweroside (9), were isolated from the bark of the Indonesian medicinal plant Bhesa paniculata (Celastraceae). The chemical structures have been elucidated on the bases of their chemical and physiocochemical properties.

Carbohydrate Sequence↗
PubMed1993

Porous polyurethane tubes as vascular graft.

A vascular graft with the inner diameter of about 3 mm was prepared from segmented poly (ether urethane) with an extrusion technique. To make the wall of the vascular grafts porous, NaCl salts were added to the polyurethane solution to be extruded and removed with water extraction after evaporating the solvent in the extruded tube. The wall was reinforced with elastic fiber to prevent dilation. The compliance of the vascular graft measured with the method of Hayashi et al. ranged from 0.2 to 0.3% mmHg -1. The initial Young's modulus was close to that of canine carotic artery, to which the porous polyurethane graft 4-cm long was anastomosed. Vascular grafts were occluded within 2 weeks after implantation, when their pore size was 0, 1.7, or 4.4 mum, whereas those with the pore size of 5.5, 7.4, and 30 mum were patent for longer than 4 weeks. When the vascular graft with the pore size of 30 mum was implanted for 6 months, the luminal surface was covered with neointima, but the endothelium-like cells appearing in the middle of the intima of the vascular graft were immature and sometimes had a very big nucleus. In addition, spindle-shaped, modified smooth muscle cells were noticed in the deep layer of the neointima, especially in the tissue where anastomotic intimal hyperplasia occurred.

Animals↗
PubMed1993

Platelet deposition onto polymeric surfaces during shunting.

In an attempt to develop blood-contacting tubes that can be applied for short-term uses with a reduced heparin concentration or, ideally, without heparinization, we evaluated the blood compatibility of polymeric materials with a rabbit ex vivo shunt model. The shunt tubes employed were made of silicone, plasticized poly(vinyl chloride) (PVC), and segmented poly(ether urethane) (PU). In addition, two kinds of surface-modified tube were used: poly(vinyl alcohol) (PVA)-coated PVC and poly(dimethylacrylamide) (PDMAA)-grafted PU. The ex vivo shunt results correlated well with protein adsorption and platelet adhesion in vitro. The following order for the extent of platelet deposition was given, irrespective of the blood-contacting duration: PDMAA-grafted PU < PVA-coated PVC < PU < silicone, PVC. It is likely that many platelet aggregates detached from the PVA-coated PVC surface. For PDMAA-grafted PU, no trace of detachment of aggregates could be detected on any of the SEM photographs. The number and morphology of blood cells adhered onto the tube surfaces during ex vivo shunting were dependent on the kind of polymer surfaces, the blood exposure time, and the flow rate of blood.

Animals↗
PubMed1991

Autosomal recessive polycystic kidney in rats.

We evaluated the characteristics of renal lesions in rat autosomal recessive polycystic kidney (ARPK). In rat ARPK, small cysts appeared primarily in the medulla 2 months after birth and gradually extended to the cortex, forming large cysts involving the entire layer after 8 months. By immunofluorescence microscopy, type IV collagen was more strongly stained in the epithelial basement membrane of the rat ARPK than in the normal rat tubular basement membrane (TBM). Electron microscopy demonstrated a marked thickening, slight splitting and lamination of the TBM in the ARPK. As peroxidase-labeled lectins, dolichos biflorus very strongly stained the cyst epithelium whereas lens culinaris did not. These findings indicate that cysts in rat ARPK originate in the collecting duct.

Age Factors↗
PubMed1991

Low doses of endothelin-3 elicit endothelium dependent vasodilation which accompanies with elevation of cyclic GMP.

Low doses (10(-16)-10(-10) M) of endothelin-3 (ET-3) elicited continuous vasodilations of mesenteric arteries preconstricted with norepinephrine (NE) but not with KCl. In arteries perfused with Ca2+ free solution, ET-3 did not affect the perfusion pressure. In endothelium-denuded arteries preconstricted with NE, ET-3 significantly elevated the perfusion pressure in a dose-related manner. The levels of cyclic GMP and cyclic AMP from the intact arteries were significantly elevated by ET-3; the cyclic GMP elevasion disappeared with methylene blue. Following endothelium-denudation, cyclic GMP elevation was abolished, but cyclic AMP elevation was unaffected. Levels of 6-Keto-PGF1 alpha in the arteries were not changed appreciably by ET-3. These data indicate that the vasodilating effects of ET-3 depend on the presence of extracellular Ca2+ and the existence of endothelium. They are accompanied by elevations of cyclic nucleotides and the elevation of cyclic GMP depends on the endothelium. It is possible that the vasodilating effects of low doses of ET-3 are associated with endothelium-derived relaxing factor.

Animals↗
PubMed1991

Cyclic GMP formation of resistance vessel in the development of hypertension in spontaneously hypertensive rats.

We investigated the basal levels and responses of cyclic GMP (cGMP) derived from perfused mesenteric arteries to acetylcholine (ACh) and sodium nitroprusside (SNP) in spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY) at different ages, in order to evaluate the basal and stimulated release of endothelium-derived relaxing factor (EDRF) from the resistance vessel during the development of hypertension. The mesenteric arteries were removed from 8-, 12- and 20-week-old WKY and SHR, and were perfused with Krebs-Henseleit solution containing 0.2 mM isobutyl methyl xanthine. The effluents from the perfused arteries were corrected before and after infusions of graded doses of ACh or SNP, and the levels of cGMP were measured. The basal levels of cGMP from the mesenteric arteries in the 12- and 20-week-old SHR were significantly lower than those in age-matched WKY. A negative correlation was observed between the basal levels of cGMP and the systolic blood pressure in SHR, but not in WKY, among all ages. On the other hand, there were no differences in the responses of cGMP to infusion of ACh between the WKY and SHR at each age. Moreover, the responsiveness of cGMP to infusion of SNP in the 12-week-old SHR was much higher than that in age-matched WKY. These data suggest that the basal cGMP formation in the arteries which may reflect the basal release of EDRF is reduced in older SHR and is associated with the development of hypertension, and that the stimulated release of EDRF is not associated with the development of hypertension.

Acetylcholine↗
PubMed1990

[A comparative study of C19 steroid-induced hypertension and deoxycorticosterone acetate (DOCA)-salt hypertension].

In order to evaluate the hypertensinogenic action of 19-hydroxyandrostenedione (19-OH-AD), which has been reported to be an amplifier of mineralocorticoid, the changes in several humoral factors were observed in 19-OH-AD treated rats as compared to those in DOCA hypertensive rats. Twenty-five male Wistar rats were castrated at 11 weeks of age, and the experiments were begun at 12 weeks of age. The rats were divided into 3 groups. The control group (n = 8) was given an s.c. injection of 0.2 ml of sesame oil. The 19-OH-AD group (n = 10) was injected s.c. with 10 mg of 19-OH-AD dissolved in 0.2 ml of sesame oil, and the DOCA group (n = 8) was injected s.c. with 10 mg of DOCA dissolved in 0.2 ml of sesame oil three time weekly. The urine was collected for a period of 24 hours, and the urine volume, and urinary excretions of electrolytes, prostaglandin E2 (PGE2), kinin and catecholamine were measured before and after the start of the experiment. The systolic blood pressure (S.B.P.) was measured by the tail-cuff method. The S.B.P. values before and at 9 weeks after the start of the experiments were 136.7 +/- 3.8 and 156.0 +/- 2.6 mmHg in the 19-OH-AD group, and 140.6 +/- 5.6 and 179.3 +/- 5.5 mmHg in the DOCA group, respectively. Body weight, which was elevated in both groups, was higher in the 19-OH-AD group than in the DOCA group. Water intake and urine volume were significantly (p less than 0.001) increased only in the DOCA group. The urinary Na/K ratio was significantly (p less than 0.001) elevated in the DOCA group as compared to that in the other two groups. However, there was no significant difference in urinary Na/K ratio between the control and 19-OH-AD groups. The urinary PGE2 and kinin excretions were significantly (p less than 0.01) increased in the DOCA group but did not change appreciably in the 19-OH-AD group. The urinary catecholamine excretion was significantly increased in the DOCA group. However, there were no differences in the catecholamine excretion between the control and 19-OH-AD groups.(ABSTRACT TRUNCATED AT 400 WORDS)

Androstenedione↗
PubMed1990

Adenylate cyclase activities of vascular smooth muscle in early and established DOCA/salt hypertensive rats.

It has been demonstrated that the adenylate cyclase activity of vascular smooth muscle regulates its tonus. The present study was undertaken to examine adenylate cyclase activity in early and established deoxycorticosterone acetate (DOCA)/salt hypertensive rats. Early and established DOCA/salt hypertensive rats were prepared by injecting 30 mg of DOCA weekly for 3 and 10 weeks, respectively, into male Wistar rats given drinking water with 1% saline. The membrane protein fraction medium containing the protein, 50 microM isoproterenol, 100 microM GTP, 50 microM forskolin or 25 microM calmodulin was applied. The adenylate cyclase activity was determined by a modified method developed in our laboratory using double isotope counting. The adenylate cyclase activity in the early DOCA/salt hypertensive rats was significantly higher (p less than 0.05) than that in the control rats in the basal condition, which was unaffected by additions of isoproterenol, GTP or forskolin. There was no significant difference in basal adenylate cyclase activity between the established DOCA/salt hypertensive and control rats. The adenylate cyclase activities in the established DOCA/salt hypertensive rats were significantly lower with GTP (p less than 0.02) and forskolin (p less than 0.01) as compared with the control rats. Calmodulin elevated the adenylate cyclase activity significantly (p less than 0.05) in the established DOCA/salt hypertensive rats as well as in the control rats. However, enzyme activity with calmodulin in the established DOCA/salt hypertensive rats was significantly lower (p less than 0.05) than that in the control rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗
PubMed1990

Preventive effect of angiotensin I on weight reduction in the adrenal glands of DOCA/salt hypertensive rats.

We examined the effect of angiotensin I (AI), without the effect of angiotensin II (AII) converted from AI, on the weight of the adrenal glands, adrenal corticosterone (B) and adrenal aldosterone under conditions where the renin-angiotensin system was suppressed, since a reduction in the size of the adrenal glands is often observed in DOCA/salt hypertensive rats. Sixty male Wistar rats fed on a 1% NaCl solution were divided into 6 groups as follows: a) Salt group: received sesame oil and vehicle, b) Salt + C group: received sesame oil and MK422 (0.14 mg/day), an angiotensin converting enzyme inhibitor (CEI), c) DOCA group: received DOCA (30 mg/week) and vehicle, d) DOCA + A group: received DOCA and AI (0.5 mg/kg/day), e) DOCA + A + C group: received DOCA and AI with MK422, and f) DOCA + C group: received DOCA and MK422. After 4 weeks, the rats were sacrificed to sample their blood and remove their adrenal glands. There was no significant difference in adrenal B among the groups apart from the DOCA + C group. Adrenal aldosterone was lower in the groups of DOCA/salt hypertensive rats than in the Salt group and Salt + C group. Furthermore, the DOCA + A + C group and DOCA + C group had lower adrenal aldosterone levels than the DOCA group and DOCA + A group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Glands↗
PubMed1990

[A study of an autosomal recessive polycystic kidney disease with facial and skeletal abnormalities in rat].

Clinico-pathological studies were made on rats with polycystic kidney disease (PCK), a congenital renal disorder transmitted as an autosomal recessive trait and characterised by facial and skeletal anomalies, with the results summarised as follows: 1) Affected animals had a poor weight gain and slightly increased urinary excretion of low molecular weight protein from 2 months after birth, and developed polyuria and hypocalciuria 5 months postnatally. They had elevation of serum urea nitrogen, increased urinary excretion of urea nitrogen and hypoproteinemia 8 months postnatally though without showing elevated serum creatinine and died around 10 months of life. 2) Kidneys of chin rats appear granular in surface, enlarge little by little while preserving the entire kidney morphology; a small cyst is formed in the renal medulla 2 months postnatally, then enlarges gradually to encroach upon the cortex and grows to involve all cortical layers by 8 months of life. This cyst was revealed by lectin staining to be derived from the collecting ducts and was assumed to correspond, both morphologically and clinically, to the infantile or juvenile form of PCK in humans. Pathogenetic factors of the characteristic facies and skeletal abnormalities were also investigated.

Animals↗
PubMed1990

[Improvement in the mechanical properties of artificial blood vessel suitable for the extracranial cerebral artery].

Saphenous vein interposition grafts have been commonly used for the reconstruction of occlusive lesions in the extracranial cerebral vessels, such as carotid or vertebral arteries. In contrast, cerebral revascularization using an artificial blood vessel has not been so common. This is due to the fact that conventional artificial blood vessels have been too firm or too rigid for use in the neurosurgery. Another reason is that the long term patency rate of small caliber artificial blood vessels has usually been inferior to that found in autologous vein grafts. The purpose of this study was to develop a soft and compliant artificial blood vessel suitable for cerebrovascular surgery. This new artificial blood vessel is made of polyurethane, porous in structure (porous polyurethane). Thus, multiple small-sized pores exist both in the inner and outer surfaces, and in the wall of the porous polyurethane graft. To test its mechanical properties, we evaluated stress-strain curves and compliance. In comparison to expanded polytetrafluoroethylene graft (Goretex), which has been one of the most commonly used artificial blood vessels in the cardiovascular surgery, the mechanical properties of the porous polyurethane graft more closely resembled those of the common carotid artery in dogs. Thus, porous polyurethane graft was shown to be a soft and compliant new artificial blood vessel. This means not only that it can be maneuvered with technical ease for anastomosis but also that there is a reduction of compliance-mismatch between the host vessel and the artificial vessel. Compliance mismatch has been documented as a major factor in the inducement of intimal hyperplasia, which causes a delayed occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

[Studies on the pressor mechanism of 19-hydroxyandrostenedione].

In the present study, the pressor activity of 19-hydroxyandrostenedione (19-OH-AD) (which is a kind of androgen) and the presence or absence of the possibility of its role as an amplifier of mineralocorticoid were investigated. 34 Wistar rats of 8 weeks of age were used as the experimental subjects. The rats were divided into 3 groups, the control group (n = 12), 19-OH-AD group (n = 12) and DOCA group (n = 10). The control group was given 0.2 ml of sesame oil, the 19-OH-AD group was given 10 mg of 19-OH-AD dissolved in 0.2 ml of sesame oil, and the DOCA group was given 10 mg of DOCA dissolved in 0.2 ml of sesame oil. This was subcutaneously administered three times a week for 4 weeks, and body weight and blood pressure were observed. At the termination of the experiment, blood was sampled by decapitation, and the serum sodium concentration, erythrocyte sodium content, plasma renin activity (PRA), plasma atrial natriuretic hormone (alpha-rANP), and contents of DOC, corticosterone and aldosterone in adrenal gland were determined. The following results were obtained. The blood pressure at the termination of the experiment was higher than that at the initiation of the experiment by 9.9 +/- 1.9 (S.E.), 31.3 +/- 1.7, and 46.2 +/- 2.0 mmHg in the control, 19-OH-AD and DOCA groups, respectively, where significant elevations were observed in both the 19-OH-AD and DOCA groups as compared with the control group. As to the serum sodium concentration, only the DOCA group showed a significant elevation (p less than 0.001) as compared with the other two groups. However, the erythrocyte sodium contents of both the 19-OH-AD and DOCA groups increased significantly as compared with the control group. Moreover, the increase of the DOCA group was significantly higher (p less than 0.001) than that of the 19-OH-AD, and a significant positive correlation between the elevation of blood pressure and the erythrocyte sodium content was observed (p less than 0.001). As to the PRA value, only the DOCA group showed a significant lowering as compared with the other two groups, whereas alpha-rANP value of the DOCA group showed a significant elevation as compared with the other two groups. As to the contents of steroid hormones in the adrenal gland, all of the steroid hormones were significantly lower in the DOCA group, while those of the 19-OH-AD group were unchanged as were those of the control group.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenal Cortex Hormones↗
PubMed1987

Suppression of plasma aldosterone by chronic ACTH administration is offset by converting enzyme inhibitor.

In order to elucidate the mechanism of suppression of plasma aldosterone by chronic ACTH administration, especially the role of the renin-angiotensin system and dopamine, we administered ACTH with or without MK422, a converting enzyme inhibitor, to reduce the endogenous angiotensin II in rats, and measured the plasma renin activity, plasma corticoid concentrations and urinary dopamine excretion. The plasma aldosterone concentration (PAC) was decreased after chronic ACTH administration. However, in the ACTH + MK422 administered group, aldosterone suppression was not observed. It appeared therefore that the aldosterone suppressing mechanism was independent of the weakened renin-angiotensin system following chronic ACTH administration, since PAC was not decreased in the ACTH + MK422 administered group when angiotensin II might be completely eliminated. The urinary excretion of dopamine was significantly increased in the chronic ACTH + MK422 administered group as well as in the chronic ACTH administered group. This suggested that the inhibitory effect of dopamine on aldosterone did not contribute significantly to the suppression of plasma aldosterone. The present results suggest therefore that the mechanism of suppression of plasma aldosterone following chronic ACTH administration was not dependent on the renin-angiotensin system and dopamine.

Adrenocorticotropic Hormone↗