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H Nakamoto

Publications and source records attributed to H Nakamoto.

At least 109 records · Page 6Linked to original sources
PubMed1991

Effects of L-arginine on systemic and renal haemodynamics in conscious dogs.

1. The effects of L-arginine on systemic and renal haemodynamics were investigated in conscious dogs. L-Arginine was administered intravenously at doses of 15 and 75 mumol min-1 kg-1 for 20 min. 2. Mean arterial blood pressure, heart rate and cardiac output were not changed significantly by L-arginine infusion. However, L-arginine infusion induced a significant elevation of renal blood flow from 50 +/- 3 to 94 +/- 12 ml/min (means +/- SEM, P less than 0.01). 3. Simultaneous infusion of NG-monomethyl-L-arginine (0.5 mumol min-1 kg-1) significantly inhibited the increase in renal blood flow produced by L-arginine (15 mumol min-1 kg-1) without significant changes in mean arterial blood pressure or heart rate. 4. Pretreatment with atropine completely inhibited the L-arginine-induced increase in renal blood flow, whereas pretreatment with indomethacin attenuated it (63 +/- 4 versus 82 +/- 10 ml/min, P less than 0.05). 5. A continuous infusion of L-arginine increased renal blood flow in the intact kidney (55 +/- 3 versus 85 +/- 9 ml/min, P less than 0.05), but not in the contralateral denervated kidney (58 +/- 3 versus 56 +/- 4 ml/min, P greater than 0.05). 6. These results suggest that intravenously administered L-arginine produces an elevation of renal blood flow, which may be mediated by facilitation of endogenous acetylcholine-induced release of endothelium-derived relaxing factor and vasodilatory prostaglandins.

Animals↗
PubMed1991

Different effects of low and high doses of endothelin on haemodynamics and hormones in the normotensive conscious dog.

The effects of low-dose endothelin on systemic haemodynamics and vasoactive hormones were examined in conscious dogs. In addition, we examined the effects of endothelin on pressor responses to noradrenaline and angiotensin II and the baroreflex regulation of heart rate in conscious dogs. Continuous infusion of 40 fmol/kg per min endothelin for 40 min induced a mild but significant reduction in mean arterial pressure from 89.1 +/- 1.7 to 82.7 +/- 2.0 mmHg (P less than 0.05), associated with decreases in total peripheral resistance 20 min later. A 400 fmol/kg per min dose of endothelin, on the other hand, induced a gradual elevation of mean arterial pressure from 89.2 +/- 2.3 to 96.8 +/- 2.0 mmHg (P less than 0.05), associated with increases in total peripheral resistance over 30 min. The 40 fmol/kg per min dose of endothelin infusion induced a significant reduction in plasma arginine vasopressin (AVP; P less than 0.05) and elevations of plasma atrial natriuretic peptide (ANP; P less than 0.05), plasma prostaglandin E2 (PGE2; P less than 0.05) and plasma 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha; P less than 0.05). The 400 fmol/kg per min dose produced elevations of AVP, ANP, PGE2 and 6-keto-PGF1 alpha (P less than 0.05). Pressor responses to noradrenaline and angiotensin II were significantly attenuated during continuous infusion of 40 fmol/kg per min endothelin, whereas 400 fmol/kg per min endothelin did not induce any significant changes compared with the control. Furthermore, baroreflex sensitivity was attenuated with 40 fmol/kg per min endothelin but did not show any significant changes at 400 fmol/kg per min.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1991

Repeated intestinal ulcerations in a patient with systemic lupus erythematosus and high serum antiphospholipid antibody levels.

We report the case of a patient with SLE who had repeated ulceration of the small intestine requiring emergency surgery. Pathologic examination revealed microthrombosis and vasculitis at the site of the intestinal ulcers. High levels of antiphospholipid antibodies, thrombocytopenia, and prolonged prothrombin time coincided with the episodes of intestinal ulceration. Antiphospholipid antibodies may be involved in the development of thrombosis resulting in the repeated episodes of intestinal ulceration in this patient. This possibility should be considered in patients with SLE who have intestinal ulceration and appropriate antithrombotic medication should be administered.

Adult↗
PubMed1991

Calcitonin gene-related peptide modulates adrenal hormones in conscious dogs.

The effects of a small dose (2 pmol/kg) of human calcitonin gene-related peptide I on plasma renin activity and hormones, including, aldosterone, ACTH, cortisol, AVP and ANH, were investigated in 14 conscious dogs. In addition, we studied the effects of calcitonin gene-related peptide on aldosterone secretion when it is stimulated by angiotensin II and ACTH. An intravenous bolus injection of 2 pmol/kg of calcitonin gene-related peptide raised plasma renin activity (by 216%, p less than 0.05), ACTH (by 85%, p less than 0.05), AVP (by 89%, p less than 0.05), and ANH (by 36%, p less than 0.05). Despite the elevation of plasma renin activity, aldosterone was decreased (by 52%, p less than 0.05). Cortisol did not change significantly. Infusion of 1 pmol.kg-1.min-1 of angiotensin II produced an elevation of aldosterone (by 186%, p less than 0.01), which was completely inhibited by pretreatment with an injection of 2 pmol/kg of calcitonin gene-related peptide. On the other hand, aldosterone secretion stimulated by ACTH was not altered significantly by pretreatment with an injection of 2 pmol/kg of calcitonin gene-related peptide. These results suggest that calcitonin gene-related peptide inhibits aldosterone secretion, especially when aldosterone is stimulated by angiotensin II. In addition, calcitonin gene-related peptide may be involved as an endocrine modulator in the physiological control of other several hormones closely related to the hemodynamics.

Adrenal Cortex Hormones↗
PubMed1991

Characterization of alterations of hemodynamics and neuroendocrine hormones in dexamethasone induced hypertension in dogs.

The serial changes in systemic and renal hemodynamics, water and electrolyte balances and various vasoactive hormones were examined in 12 conscious dogs before, during (10 days) the administration of dexamethasone (DEX: 0.5 mg/kg/day) and after the cessation of DEX. In addition, during the administration of DEX, pressor responses to angiotensin II, norepinephrine, an angiotensin II analogue, saralasin, and an alpha-1-blocker, prazosin, were studied. Abrupt elevation of blood pressure to 106 +/- 5 mmHg on Day 1 (vs. 91 +/- 6 mmHg control: P less than 0.05) associated with marked increases in total peripheral resistance (P less than 0.01) was shown in DEX treated animals. Accompanied with these changes, renal blood flow increased to 146 +/- 12 ml/min (vs. 103 +/- 8 ml/min control: P less than 0.05) on Day 1 and maintained. In contrast, the results of serial alterations in hormones could not show any significant changes except significant elevations in atrial natriuretic peptide and reductions of cortisol and arginine vasopressin. Also, marked natriuresis and diuresis were observed in DEX administration dogs. Pressor response to norepinephrine was significantly increased and administration of either saralasin and prazosin significantly reduced the blood pressure of DEX treated animals. These results in DEX-treated conscious dogs confirmed our previous findings in human and rats. Glucocorticoid-induced hypertension mainly depends on the increases in total peripheral resistance but not volume factors.

Animals↗
PubMed1990

Regulation of expression of carbon-assimilating enzymes by nitrogen in maize leaf.

We have utilized the cellular differentiation gradient of the developed, youngest leaf to examine the regulation by nitrogen of levels of phosphoenolpyruvate carboxylase (PEPCase), pyruvate orthophosphate dikinase (PPDK), and ribulose 1,5-bisphosphate carboxylase in maize (Zea mays L.). The protein whose level regulated most preferentially by N availability was PEPCase, followed by PPDK, and the changes in level occurred most conspicuously at the photosynthetically maturing cells. Pulse and pulse-chase experiments to analyze photosynthetic fixation of [(14)C]CO(2) indicate that maize leaf primarily exploited a C(4)-mode of photosynthetic fixation of carbon dioxide even under a selective reduction in levels of these proteins. The effects of N on the synthesis of these proteins and the accumulation of corresponding mRNAs during recovery from a deficiency were examined by pulse and pulse-chase labeling with [(35)S]Met and by hybridization, respectively. The rate of turnover of PPDK was substantially higher than that of the other proteins. Results also showed that the reduced accumulation of PEPCase, as well as PPDK, under N deficiency could largely be accounted for a reduced level of synthesis of protein with a concomitant reduction in level of their mRNAs. This indicates that the N-dependent selective accumulation of these enzymes is primarily a consequence of level of its mRNAs.

Journal Article↗
PubMed1990

Effects of antihypertensive agents on blood pressure and the progress of renal failure in partially nephrectomized spontaneously hypertensive rats.

The purpose of this study was to investigate the effects of antihypertensive agents on blood pressure and the development of glomerular changes in salt-loaded, 5/6 nephrectomized spontaneously hypertensive rats (SHR). Thirty-two spontaneously hypertensive rats with 5/6 nephrectomy were divided into 4 groups: a control group (N = 8), and group treated with 10 mg/kg/day trichlormethiazide. (N = 8), 30 mg/kg/day captopril (N = 8), and 200 mg/kg/day nicardipine (N = 8). Each of these antihypertensive drugs was added to the drinking water for 10 weeks and the rats were given the drugs and a high-salt diet (5% NaCl). During the experiment, body weight and systolic blood pressure were measured every 2 weeks. At the end of the study, blood was collected for determination of serum creatinine, blood urea nitrogen, serum protein, serum sodium and potassium, and plasma renin activity and aldosterone concentration. Also renal tissues were obtained for light and electron microscopic examination at the end of the study. Systolic blood pressure in 5/6 nephrectomized SHR loaded with a high salt was significantly reduced by administration of trichlormethiazide (155 +/- 12 versus 204 +/- 12 mm Hg), but not by administration of either captopril or nicardipine. However, levels of serum creatinine were not significantly elevated in rats treated with captopril and nicardipine (control: 0.93 +/- 0.11 mg/dl, captopril: 0.62 +/- 0.01 mg/dl, nicardipine: 0.55 +/- 0.05 mg/dl). In contrast to changes in blood pressure, marked glomerular sclerosis with hyalinosis, which was found in the control group was not ameliorated by treatment with trichlormethiazide. However, these changes were not observed in rats treated with either captopril or nicardipine in spite of the absence of a prominent fall in blood pressure. These data suggest that captopril and nicardipine ameliorated glomerular injury regardless of the level of systolic blood pressure through the direct and/or indirect actions on the glomerulus.

Animals↗
PubMed1989

Differences in the effects of angiotensin converting enzyme inhibitors with or without a thiol group in chronic renal failure in rats.

1. We have investigated the effects of the non-renin-mediated actions of angiotensin converting enzyme inhibitors on the progression of chronic renal failure accelerated by hypertension. For this purpose, we studied the effects of captopril (a thiol-containing angiotensin converting enzyme inhibitor), enalapril (an angiotensin converting enzyme inhibitor without a thiol group) and cysteine (a thiol-containing amino acid which has no angiotensin converting enzyme-inhibitory action) in adriamycin-treated rats with deoxycorticosterone acetate-salt hypertension, in which the renin-angiotensin system was suppressed. 2. There were no significant differences in blood pressure between these groups and the control group [adriamycin-treated group with deoxycorticosterone acetate-salt loading, 206 +/- 7 mmHg (27.4 +/- 0.9 kPa) at week 10]. 3. Massive proteinuria occurred in all groups. At the end of the experiment (at week 10), urinary protein excretion was significantly reduced in the captopril and cysteine groups compared with the control group. No manifest improvements appeared in the enalapril group. 4. Levels of serum creatinine and blood urea nitrogen increased progressively. At week 10, the increases in the serum levels of creatinine were less in the captopril (87 +/- 16 mmol/l) and cysteine (80 +/- 19 mmol/l) groups than in the control group (124 +/- 27 mmol/l) (P less than 0.01). No marked differences were found between the control and enalapril groups. 5. Captopril and cysteine caused more than a three-fold reduction in the focal glomerulosclerosis score when compared with that in the control group, but enalapril did not decrease the score. The extent of tubulointerstitial change was parallel with the focal glomerulosclerosis score. 6. We conclude that the thiol group is possibly involved in the mechanism of the beneficial effects of some angiotensin converting enzyme inhibitors on the progression of chronic renal failure exacerbated by hypertension.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1989

Effects of endothelin on systemic and renal haemodynamics and neuroendocrine hormones in conscious dogs.

1. The effects of endothelin on systemic and renal haemodynamics and plasma concentrations of neuroendocrine hormones including plasma renin activity, aldosterone, adrenocorticotropic hormone, cortisol, catecholamines and arginine vasopressin were investigated in 18 conscious dogs. 2. Bolus injection of 4 pmol of endothelin/kg did not cause any significant changes in haemodynamics. Mean arterial pressure was elevated by both doses of 40 pmol/kg [91 +/- 2 to 99 +/- 2 mmHg (12.1 +/- 0.3 to 13.2 +/- 0.3 kPa), P less than 0.05] or 200 pmol/kg [93 +/- 2 to 107 +/- 3 mmHg (12.4 +/- 0.3 to 14.3 +/- 0.4 kPa), P less than 0.01], the latter dose increasing cardiac output (14%, P less than 0.05) and heart rate (9%, P less than 0.05), and the former reducing these parameters (14% and 8%, P less than 0.05, respectively). 3. In contrast with the various changes in systemic haemodynamics, renal blood flow transiently increased immediately after bolus injection in a dose-dependent manner (28%, P less than 0.05, 50%, P less than 0.01 and 110%, P less than 0.01 with 4, 40 and 200 pmol of endothelin/kg, respectively). This transient elevation of renal blood flow was followed by a gradual decrease (16%, P less than 0.05; 31%, P less than 0.01 and 36%, P less than 0.01) at 10 min. 4. All neurohormones were elevated in a dose-dependent manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗
PubMed1989

Purification and Characterization of NAD Malic Enzyme from Leaves of Eleusine coracana and Panicum dichotomiflorum.

NAD malic enzyme (EC 1.1.1.39), which is involved in C(4) photosynthesis, was purified to electrophoretic homogeneity from leaves of Eleusine coracana and to near homogeneity from leaves of Panicum dichotomiflorum. The enzyme from each C(4) species was found to have only one type of subunit by SDS polyacrylamide gel electrophoresis. The M(r) of subunits of the enzme from E. coracana and P. dichotommiflorum was 63 and 61 kilodaltons, respectively. The native Mr of the enzyme from each species was determined by gel filtration to be about 500 kilodaltons, indicating that the NAD malic enzyme from C(4) species is an octamer of identical subunits. The purified NAD malic enzyme from each C(4) species showed similar kinetic properties with respect to concentrations of malate and NAD; each had a requirement for Mn(2+) and activation by fructose- 1,6-bisphosphate (FBP) or CoA. A cooperativity with respect to Mn(2+) was apparent with both enzymes. The activator (FBP) did not change the Hill value but greatly decreased K(0.5) (the concentration giving half-maximal activity) for Mn(2+). The enzyme from E. coracana showed a very low level of activity when NADP was used as substrate, but this activity was also stimulated by FBP. Significant differences between the enzymes from E. coracana and P. dichotomiflorum were observed in their responses to the activators and their immunochemical properties. The enzyme from E. coracana was largely dependent on the activators FBP or CoA, regardless of concentration of Mn(2+). In contrast, the enzyme from P. dichotomiflorum showed significant activity in the absence of the activator, especially at high concentrations of Mn(2+). Both immunodiffusion and immunoprecipitation, using antiserum raised against the purified NAD malic enzyme from E. coracana, revealed partial antigenic differences between the enzymes from E. coracana and P. dichotomiflorum. The activity of the NAD malic enzyme from Amaranthus edulis, a typical NAD malic enzyme type C(4) dicot, was not inhibited by the antiserum raised against the NAD malic enzyme from E. coracana.

Journal Article↗
PubMed1989

Calcitonin gene-related peptide is an inhibitor of aldosterone secretion.

This study examined the effects of calcitonin gene-related peptide (CGRP) on aldosterone secretion both in vivo and in vitro. Intravenous administration of CGRP (0.01 micrograms/kg) in 6 conscious dogs produced a significant decrease in plasma aldosterone concentration from 68 +/- 12 pg/ml to 28 +/- 11 pg/ml (p less than 0.05) despite a mild but significant elevation of plasma renin activity. In an in vitro study using isolated rabbit adrenal glomerulosa cells CGRP reduced the basal aldosterone secretion in a dose-related manner and furthermore 10(-9) M CGRP inhibited the aldosterone secretion stimulated by 10(-8) M angiotensin II. From these results it is suggested that CGRP has an inhibitory effect on aldosterone secretion.

Aldosterone↗
PubMed1989

The influence of dietary protein on the synthesis of vasoactive substances in subtotally nephrectomized spontaneously hypertensive rats.

The effects of dietary protein alterations on the synthesis of prostaglandins and kallikrein were examined in subtotally nephrectomized spontaneously hypertensive rats. Three diets containing 40, 24 and 8% protein were prepared. After subtotal nephrectomy, rats were given one of the three diets for the next 12 weeks. During the study, systolic blood pressure, urinary excretions of protein, 6-keto-prostaglandin F1 alpha, thromboxane B2 and kallikrein were measured every 2 weeks. Although the diets did not prevent the further elevation of systolic blood pressure, the rats on the low protein diet displayed lower serum creatinine levels and urinary protein levels. The urinary excretion of thromboxane B2 was unaffected by the amount of dietary protein, but the urinary excretion of 6-keto-prostaglandin F1 alpha was lower in the low protein diet group. Furthermore, the urinary excretion of kallikrein increased significantly in rats on high protein diet. These results suggest that manipulation of dietary protein may alter the natural course of renal failure induced by subtotal nephrectomy in spontaneously hypertensive rats.

6-Ketoprostaglandin F1 alpha↗
PubMed1988

[2 surgically treated cases of adrenocortical carcinoma producing steroid hormones without endocrinological symptoms--case report and a review of cases in the Japanese literature].

We have experienced two male cases of an adrenocortical carcinoma that have produced steroid hormones without endocrinological symptoms. Both men were admitted to hospital because of an abdominal pain and left hypochondral tumors. In each case, an abdominal CT, an ultrasonogram and an angiogram demonstrated a left adrenal tumor, and levels of blood dehydroepiandrosterone sulfate, etiocholanolone, pregnenolone sulfate and urine 17 KS were elevated. The tumors were resected and the histology revealed that they were adrenocortical carcinomas. Postoperatively, the levels of their urine hormones returned to normal values, though in one man recurrence occurred a year later. Only 8 cases of an adrenocortical carcinoma that has produced steroids without specific endocrinological symptoms have been reported in Japan, and we also report on two cases herein.

17-Ketosteroids↗
PubMed1987

Influence of leaf age on photosynthesis, enzyme activity, and metabolite levels in wheat.

The rate of photosynthesis under high light (1000 micromole quanta per square meter per second) and at 25 degrees C was measured during development of the third leaf on wheat plants and compared with the activity of several photosynthetic enzymes and the level of metabolites. The rate of photosynthesis reached a maximum the 7th day after leaf emergence and declined thereafter. There was a high and significant correlation between the rate of photosynthesis per leaf area and the activities of the enzymes ribulose 5-phosphate kinase (r = 0.91), ribulose 1,5-bisphosphate (RuBP) carboxylase (r = 0.94), 3-phosphoglycerate (PGA) kinase (r = 0.82), and fructose 1,6-bisphosphatase (r = 0.80) per leaf area. There was not a significant correlation of photosynthesis rate with chlorophyll content. The rate of photosynthesis was strongly correlated with the level of PGA (r = 0.85) and inversely correlated with the level of triose phosphate (dihydroxyacetone phosphate and glyceraldehyde 3-phosphate) (r = 0.92). RuBP levels did not change much during leaf development; therefore photosynthesis rate was not correlated with the level of RuBP. The rate of photosynthesis was at a maximum when the ratio of PGA/triose phosphate was high, and when the ratio of RuBP/PGA was low. Although several enzymes change in parallel with leaf development, the metabolite changes suggest the greatest degree of control may be through RuBP carboxylase. The sucrose content of the leaf was highest under high rates of photosynthesis. There was no evidence that later in leaf development, photosynthesis (measured under high light and at 25 degrees C) was limited by utilization of photosynthate.

Journal Article↗