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Biomedical subjects

H Mabuchi

Publications and source records attributed to H Mabuchi.

At least 127 records · Page 7Linked to original sources
PubMed1997

Decreased expression of 20-kD homologous restriction factor (HRF20, CD59) on T lymphocytes in Epstein-Barr virus (EBV)-induced infectious mononucleosis.

HRF20 (CD59) is one of the membrane-associated complement regulatory proteins. The characteristic function of CD59 is to prevent membrane attack complex (MAC) formation on the cell surface and to protect the cell from complement-mediated cell lysis. We examined the expression of CD59 antigen on T cell subpopulations in patients with acute infectious mononucleosis (IM) and analysed the relationship between the amount of CD59 expression and activation-induced cell death of mature T cells with apoptosis. Decreased expression of CD59 on CD8+ T cells, especially on CD45RO+ and HLA-DR+ activated T cells, was marked in acute IM patients. In contrast, activated CD4+ T cells from IM patients expressed as much CD59 antigen as CD4+ T cells from healthy volunteers. After incubation-induced cell death, viable CD8+ T cells showed normal amounts of CD59 antigen on their surface. CD59dim CD8+ T cells were more susceptible to apoptosis than CD59bright CD8+ T cells. These findings suggest that decreased expression of CD59 on CD8+ T cells may discriminate the susceptibility of activated CD8+ T cells to activation-induced cell death in IM.

Acute Disease↗
PubMed1997

Angiotensin-converting enzyme inhibitors are associated with the need for increased recombinant human erythropoietin maintenance doses in hemodialysis patients. Risks of Cardiac Disease in Dialysis Patients Study Group.

The influence of angiotensin-converting enzyme inhibitors (ACEIs) on recombinant human erythropoietin (rhEPO) maintenance doses in hemodialysis patients was studied. One hundred and eight chronic hemodialysis patients (55 males and 53 females, mean age 61.2+/-12.6 years) were investigated. The rhEPO maintenance doses in the ACEI-treated group (n = 49) were 101.7+/-51.7 U/kg/week and in the nontreated group (n = 59) 79.2+/-37.8 U/kg/week (p < 0.05). No difference was observed in hematocrit between the ACEI-treated and nontreated groups. In stepwise regression analysis, the parameters associated with increased rhEPO maintenance doses were female gender, ACEI administration, low total iron binding capacity, and low serum free carnitine levels. In conclusion, ACEI administration might reduce the response to rhEPO. In hemodialysis patients who need high-dose rhEPO to maintain the target hematocrit in the absence of iron deficiency, hyperparathyroidism, infection, malignancy, malnutrition, and aluminum toxicity, ACEI administration should be considered.

Adult↗
PubMed1997

Cholesteryl ester transfer protein activity enhances plasma cholesteryl ester formation. Studies in CETP transgenic mice and human genetic CETP deficiency.

The plasma cholesteryl ester transfer protein (CETP) promotes the removal of HDL cholesteryl esters and is thought to stimulate reverse cholesterol transport (RCT). However, mechanisms by which CETP may stimulate RCT are poorly understood. Thus, we examined the relationship between plasma CETP expression and plasma cholesteryl ester formation in CETP transgenic (Tg) mice, hamsters, and human subjects with genetic CETP deficiency. Incubation of CETP Tg mouse plasma showed a 20% to 40% increase in plasma cholesterol esterification rate (CER, P < .05) compared with control mice. Injection of a neutralizing CETP monoclonal antibody (MAb) (TP2) into natural flanking region CETP Tg mice resulted in an increase in plasma free cholesterol (FC) concentration, FC/CE ratio, FC/phosphatidylcholine ratio, and hepatic CETP mRNA. In hamsters, CETP inhibition also resulted in an increase in plasma FC/phosphatidylcholine ratio and increased CETP mRNA in adipose tissue. In humans with two common CETP gene mutations (an intron 14 splicing defect and a D442G missense mutation), mean plasma CERs were 39 and 60, respectively, compared with 89 nmol x mL-1 x h-1 in normal subjects. By contrast, lecithin:cholesterol acyltransferase (LCAT) mass was normal in CETP-deficient subjects. MAb neutralization of CETP activity in incubated human plasma did not alter the LCAT reaction, even after supplementation with discoidal HDL and VLDL. Thus, genetic alterations in CETP levels lead to secondary changes in the plasma LCAT reaction, possibly because of remodeling of HDL by CETP acting in concert with other factors in vivo. In human genetic CETP deficiency, a moderate impairment in the plasma LCAT reaction may contribute to a defect in RCT, providing a potential mechanism to explain the recently observed excess of coronary heart disease in these subjects.

Animals↗
PubMed1997

Vascular aldosterone in genetically hypertensive rats.

We have reported that aldosterone is synthesized and cytochrome P450aldo mRNA exists in the vasculature. To clarify the pathophysiological role of vascular aldosterone in hypertension, we compared aldosterone production in the mesenteric arteries of stroke-prone spontaneously hypertensive rats (SHRSP) with that in Wistar-Kyoto rats (WKY). The expressions of mRNA of cytochrome P450aldo, mineralocorticoid receptor, and alpha 1, Na,K-ATPase in the mesenteric arteries were compared between the two groups. Aldosterone concentration in the perfusate of the vasculature was measured by radioimmunoassay after purification with high-performance liquid chromatography. Cytochrome P450aldo and mineralocorticoid receptor mRNA levels were quantified by Southern blot analysis of the products of reverse-transcribed polymerase chain reaction. Levels of alpha 1 Na,K-ATPase mRNA were measured by Northern blot analysis. Vascular aldosterone and cytochrome P450aldo mRNA levels of 2-week-old SHRSP were significantly increased compared with those of age-matched WKY. However, vascular aldosterone in 4- and 9-week-old SHRSP did not differ from that in age-matched WKY. Expression levels of mineralocorticoid receptor mRNA in the vasculature of 4- and 9-week-old SHRSP were significantly increased compared with those in age-matched WKY. Concentrations of vascular alpha 1 Na,K-ATPase mRNA of 2-, 4-, and 9-week-old SHRSP also were significantly higher than those in age-matched WKY. These results suggest that vascular aldosterone contributes to the pathophysiology of hypertension in SHRSP in the early stage.

Aldosterone↗
PubMed1997

Brain nitric oxide synthase messenger RNA in central mineralocorticoid hypertension.

The mechanism underlying the central hypertensinogenic effects of mineralocorticoids remains unclear. Given that nitric oxide (NO) is thought to act at autonomic sites in the brain to regulate arterial blood pressure, the effects of the potent mineralocorticoids aldosterone and 19-noraldosterone on the abundance of neuronal NO synthase (nNOS) mRNA in the brain were investigated. Wistar-Kyoto rats received a continuous intracerebroventricular infusion of aldosterone or 19-noraldosterone (5 ng/h) from an implanted osmotic minipump for 4 weeks. Total RNA was purified from microdissected tissue blocks containing the hypothalamus, dorsal medulla, rostral ventrolateral medulla, or caudal ventrolateral medulla, and changes in the abundance of nNOS mRNA were determined with a semiquantitative competitive polymerase chain reaction method. Blood pressure was significantly increased in rats 2, 3, and 4 weeks after the onset of intracerebroventricular aldosterone or 19-noraldosterone infusion compared with that in animals receiving vehicle. Subcutaneous infusion of either mineralocorticoid had no effect on blood pressure. Compared with controls, rats treated with aldosterone or 19-noraldosterone for 4 weeks showed significant decreases in the amount of nNOS mRNA in the hypothalamus and rostral and caudal ventrolateral medulla. These data suggest that reduced nNOS activity may contribute to the increase in blood pressure in rats with central mineralocorticoid-induced hypertension.

Aldosterone↗
PubMed1997

Quantitative evaluation of the rate of myocardial interstitial fibrosis using a personal computer.

We investigated the reliability and reproducibility of an image-analyzing system run on a personal computer for measurement of myocardial interstitial fibrosis. Measurements of myocardial interstitial fibrosis in right ventricular endomyocardial biopsies obtained from patients with hypertrophic cardiomyopathy determined by this image-analyzing system were compared with measurements determined by the point-counting method. We also investigated the correlation between measurements of interstitial fibrosis obtained by image analysis and biochemical measurements of myocardial levels of hydroxyproline in normal and cardiomyopathic hamsters. The intra- and interobserver variability were significantly lower for measurements obtained by the image-analyzing system than for measurements obtained by the point-counting system. Reproducibility was superior with the image-analyzing method. The rate of myocardial interstitial fibrosis determined by the computer image-analyzing method was positively correlated with the hydroxyproline measurement (r = 0.89). Our results suggest that an image-analyzing system using a personal computer provides reproducible results with a high level of reliability.

Adult↗
PubMed1997

Catalytically inactive lecithin: cholesterol acyltransferase (LCAT) caused by a Gly 30 to Ser mutation in a family with LCAT deficiency.

Plasma lecithin:cholesterol acyltransferase (LCAT) plays an important role in early steps of reverse cholesterol transport, i.e., cholesterol efflux from peripheral tissues and cholesterol esterification in HDL. However, structural and functional relationships of LCAT have not been fully elucidated. We described a missense mutation of Gly 30-to-Ser in a patient with classical LCAT deficiency. The proband was homozygous for the mutation and had a very low level of HDL cholesterol (2 mg/dl), with a half of normal LCAT mass (2.75 micrograms/ml), but no detectable or very low LCAT activity in endogenous and exogenous substrate assays. Both his mother and sister were heterozygous for the mutation, and had slightly decreased levels of HDL cholesterol (34 and 36 mg/dl, respectively). Transient expression study using COS cells indicated that mutant cDNA produces similar amounts of media protein as compared to wild type, but no detectable LCAT activity. The missense mutation may result in a near-native conformation without large effects on cellular secretion but a catalytically defective protein. Thus, the N-terminal domain appears crucial for enzymatic activity, in addition to the catalytically active consensus sequence of Gly179 to Gly183 and a putative sterol binding domain of Glu154 to Lys173.

Animals↗
PubMed1996

Absence of CD69 expression on peripheral eosinophils in episodic angioedema and eosinophilia.

A 45-year-old woman with episodic angioedema and eosinophilia is presented. CD69, which is one of the surface antigens of activated eosinophils, was not expressed on the peripheral eosinophils in this patient, in contrast to hypereosinophilic syndrome. This suggests that CD69, which is not dependent on eosinophil density, may be another useful activation marker of eosinophils to distinguish episodic angioedema and eosinophilia from hypereosinophilic syndrome.

Angioedema↗
PubMed1996

Long-term probucol treatment results in regression of xanthomas, but in progression of coronary atherosclerosis in a heterozygous patient with familial hypercholesterolemia.

A 66-year-old male heterozygous familial hypercholesterolemia (FH) patient with significant coronary atherosclerosis has been treated by us with probucol (1000 mg daily) for eight years. This treatment has produced significant reductions in the cholesterol levels of his serum, low density lipoprotein (LDL), and high density lipoprotein (HDL) from 237 +/- 20 mg/dl (mean +/- S.D.) to 156 +/- 15, from 175 +/- 8 to 111 +/- 16 mg/dl, and from 23 +/- 4 to 19 +/- 2 mg/dl, respectively. These reductions have been maintained for eight years. Serum triglyceride levels also decreased, from 220 +/- 54 to 146 +/- 36 md/dl. During this period, marked regression of xanthomas on the eyelids and finger extensor tendons was observed, while thickness of the Achilles tendons was reduced from 21.0 mm to 13.0 mm. On other hand, effort-induced anginal symptoms requiring additional antianginal medication have been noticed, and angiographically-demonstrated coronary atherosclerosis has progressed significantly during these eight years. These observations lead us to suggest that maintaining low levels of HDL cholesterol with probucol, even though resulting in satisfactory reduction of LDL cholesterol and marked regression of xanthomas, appears to be associated with the progression of atherosclerosis in the coronary arteries.

Aged↗
PubMed1996

The expression of steroidogenic enzyme genes in human vascular cells.

Recently, we demonstrated that aldosterone is produced by human vascular cells, and that vascular aldosterone is linked to angiotensin II-induced hypertrophy of vascular smooth muscle cells. We therefore examined whether genes encoding steroidogenic enzymes responsible for aldosterone biosynthesis from cholesterol are expressed in vascular cells. Using polymerase chain reaction after reverse transcription, type I and II 3 beta-HSD (3 beta-hydroxysteroid dehydrogenase), P-450c21 (21-hydroxylase), and P-450c18 (18-hydroxylase/oxidase) genes were found to be expressed both in endothelial cells and smooth muscle cells cultivated from human pulmonary arteries. However, P-450scc (cholesterol side chain cleavage enzyme) and P-45011 beta (11 beta-hydroxylase) mRNAs could not be detected. These findings suggest that the enzyme system responsible for aldosterone production in human vascular cells is different from that found in the adrenal cortex and that vascular aldosterone may be synthesized from metabolic intermediates which originate from the circulation. Extra-adrenal 3 beta-HSD and steroid 21-hydroxylase occur in a wide variety of tissues. Thus, human vascular cells can retain the ability to produce aldosterone by expressing the P-450c18 gene.

3-Hydroxysteroid Dehydrogenases↗
PubMed1996

Severe gastrointestinal complications of dialysis-related amyloidosis in two patients on long-term hemodialysis.

Two patients undergoing long-term hemodialysis developed severe gastrointestinal complications due to dialysis-related amyloidosis (DRA). Case 1, a 68-year-old male on hemodialysis for 18 years developed marked gastric dilatation and severe paralytic ileus. Five years later he died of peritonitis. Autopsy showed extensive amyloid deposits in the muscle layers and blood vessels throughout the gastrointestinal tract. Case 2, a 56-year-old male on hemodialysis for 19 years, developed panperitonitis due to perforation of the sigmoid colon. The resected colon showed massive amyloid deposits in the muscle layers. In both cases, immunological studies revealed positive staining for antihuman beta2-microglobulin antibody. In long-term hemodialysis patients with gastrointestinal symptoms, gastrointestinal complications of DRA should be considered.

Aged↗
PubMed1996

Correlation between serum carnitine levels and erythrocyte osmotic fragility in hemodialysis patients.

The relationship between serum carnitine levels and erythrocyte osmotic fragility was investigated in 26 chronic hemodialysis patients (10 males and 16 females, mean age: 57.3 +/- 13.5 years). Serum total-carnitine (TC), free-carnitine (FC) and acyl-carnitine (AC) levels were determined by a spectrophotometric method. Erythrocyte osmotic fragility was measured with a coil planet centrifuge. Serum TC levels were 39.9 +/- 13.4 mumol/l (mean +/- SD), FC levels were 21.8 +/- 7.8 mumol/l and AC levels were 18.0 +/- 9.6 mumol/l. The mean hemolysis end point (HEP) was 67.4 +/- 5.4 mOsM, the hemolysis maximum point (HMP) was 86.3 +/- 5.4 mOsM and the hemolysis start point (HSP) was 101.2 +/- 4.4 mOsM. Each hemolysis point in hemodialysis patients was elevated in comparison with the normal range. There were no significant differences in hemolysis points between a recombinant human erythropoietin (rhEPO)-treated group and nontreated group. HEP correlated with serum TC (r = -0.56, p < 0.01) and AC levels (r = -0.58, p < 0.01). HMP correlated with serum TC (r = -0.42, p < 0.05) and FC levels (r = -0.41, p < 0.05). Dose requirement of rhEPO maintaining target hematocrit correlated with serum TC (r = 0.54, p < 0.05) and FC levels (r = 0.50, p < 0.05). These data support that low serum carnitine levels accelerate erythrocyte osmotic fragility. Carnitine may contribute to the metabolism of erythrocyte membrane and have an impact on the efficacy of rhEPO in correcting renal anemia.

Adult↗
PubMed1996

Effect of adrenocorticotropin stimulation on the synthesis of 19-noraldosterone in man.

The hormone, 19-noraldosterone, which was recently shown to be synthesized and produced in the human adrenal gland, exhibits potent mineralocorticoid and hypertensinogenic activities. This hormone is controlled in part by the renin-angiotensin system. We studied the effects of ACTH stimulation on the synthesis of 19-noraldosterone in vitro and in six normal men. 19-Noraldosterone was measured by a specific RIA after the urine extract or incubation medium was purified by high performance liquid chromatography. The 24-h urinary excretion of 19-noraldosterone increased approximately 4-fold during the administration of ACTH (40 U, injected im twice daily for 3 days). Virtually identical responses were observed with aldosterone, 18-hydroxycorticosterone, 18,19-dihydroxycorticosterone, and 18-hydroxy-19-norcorticosterone. Glomerulosa cells isolated from human adrenals were incubated with angiotensin II (10(-7), 10(-8), and 10(-9) mol/L) or ACTH (10(-8), 10(-9), and 10(-10) mol/L). Angiotensin II and ACTH increased the production of 19-noraldosterone dose-dependently from isolated glomerulosa cells. The secretion of aldosterone, 18-hydroxycorticosterone, 18,19-dihydroxycorticosterone, and 18-hydroxy-19-norcorticosterone in response to angiotensin II and ACTH was identical to that of 19-noraldosterone. These observations suggest that 19-noraldosterone is stimulated by the renin-angiotensin system as well as ACTH.

18-Hydroxycorticosterone↗
PubMed1996

Regulation of aldosterone synthase in human vascular endothelial cells by angiotensin II and adrenocorticotropin.

Mineralocorticoids have been suggested to act on blood vessels, leading to increased vasoreactivity and peripheral resistance. Aldosterone is synthesized locally in blood vessels and participates in the hypertrophy of vascular smooth muscle cells. In this study we examined the effects of angiotensin II (ANG II), potassium, and ACTH on the production of aldosterone, the activity of aldosterone synthase, and the expression of CYP11B2 and CYP11B1 messenger ribonucleic acid (mRNA) in cultured human vascular endothelial cells. Human vascular endothelial cells were incubated with ANG II, potassium, or ACTH with or without [14C]deoxycorticosterone ([14C]DOC). Incubation medium was collected, and chromatography was preformed in a reverse phase high performance liquid chromatography system. The concentration of aldosterone in the incubation medium was measured using RIA after separation with the high performance liquid chromatography system. The activity of aldosterone synthase was estimated by the conversion of [14C]DOC to [14C]aldosterone. The levels of CYP11B2 and CYP11B1 mRNA were determined by competitive PCR. ANG II, potassium, and ACTH increased the production levels of aldosterone in a dose-dependent fashion. Both ANG II and potassium increased the conversion of [14C]DOC to [14C]aldosterone, but ACTH did not significantly increase the conversion. Both ANG II and potassium increased the concentration of CYP11B2 mRNA, but not that of CYP11B1 mRNA. Tumor necrosis factor reduced ANG II- and potassium-induced aldosterone synthesis and CYP11B2 mRNA levels. ACTH did not influence the expression of CYP11B2 mRNA. These results suggest that vascular aldosterone synthase is controlled by ANG II and potassium at the transcriptional level.

Adrenocorticotropic Hormone↗