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Biomedical subjects

H Ibayashi

Publications and source records attributed to H Ibayashi.

At least 37 records · Page 2Linked to original sources

Increased proportion of proapolipoprotein A-I in HDL from patients with liver cirrhosis and hepatitis.

We examined the isoform pattern of apolipoprotein A-I (apo A-I) in high density lipoprotein from patients with liver disease. An increase in the proportion of proapo A-I was evident in patients with decompensated liver cirrhosis, acute hepatitis and hepatocellular carcinoma. The rate of conversion from proapo A-I to apo A-I was low in sera from those with liver disease, compared to normal controls. The proportion of proapo A-I showed a tendency toward increase with advance in liver damage. These results suggest that the liver is participating in the reaction converting proapo A-I to the mature apo A-I.

Apolipoprotein A-I↗

Effects of insulin, dexamethasone and glucagon on the production of apolipoprotein A-I in cultured rat hepatocytes.

Cultured rat hepatocytes were used to study the effects of hormones on the production of apo A-I. In addition, we compared these effects with the production of albumin. Hepatocytes were isolated from normal adult rat livers and cultured in MEM, as nearly confluent monolayers. In the absence of hormones, apo A-I and albumin accumulated in the culture medium almost linearly for periods up to 24 h. The rates of accumulation of apo A-I and albumin in the medium were 22 ng/mg cell protein per h and 1.2 micrograms/mg cell protein per h, respectively. During the incubations the cellular contents of apo A-I remained constant. Insulin stimulated the production of albumin at concentrations over 10(-10) M, but inhibited the production of apo A-I at concentrations over 10(-8) M. Dexamethasone showed no significant effects on albumin production but stimulated apo A-I production at concentrations over 10(-6) M. Glucagon inhibited the production of albumin and apo A-I dose-dependently at concentrations over 10(-10) M. Thus, the production of albumin and apo A-I are presumably controlled by different regulatory mechanisms.

Albumins↗

RU486 inhibits induction of aromatase by dexamethasone via glucocorticoid receptor in cultured human skin fibroblasts.

Effects of RU486 on the induction of aromatase by dexamethasone via glucocorticoid receptor were determined using cultured human skin fibroblasts. Competition of [3H]dexamethasone binding to the cytosol receptor was 7 times stronger with RU486 than with dexamethasone. The order of the strength of competition was RU486 greater than dexamethasone greater than betamethasone greater than prednisolone greater than hydrocortisone. RU486 abolished a specific 8.6 S [3H]dexamethasone binding peak in the cytosol, determined using a sucrose density gradient analysis. Dexamethasone markedly induced aromatase and this event was strongly suppressed by RU486, in a dose-dependent manner, in the cultured skin fibroblasts. A linear correlation between the strength of competition and the induction of aromatase of various glucocorticoids was observed. RU486 non-competitively inhibited aromatase induction by dexamethasone determined from a double reciprocal plot of aromatase activity, with respect to [3H]androstenedione concentration in the presence of RU486. These results show that RU486 is a peripheral noncompetitive antiglucocorticoid on aromatase induction by glucocorticoid in human skin fibroblasts and that aromatase induction is a good marker for the biological function of glucocorticoid receptor in human skin fibroblasts.

Aromatase Inhibitors↗

Systemic triglyceride storage disease with normal carnitine: a putative defect in long-chain fatty acid metabolism.

A 45-year-old Japanese man presented with lipid storage myopathy, fatty liver, cardiomyopathy, vacuolated leukocytes (Jordans' anomaly) and perceptive deafness. His parents were consanguineous and his younger sister was also affected. Histopathological and biochemical studies revealed an abnormal accumulation of triglyceride in muscle, liver, leukocytes, gastrointestinal endothelial cells and cultured skin fibroblasts. On electron microscopy, the vacuoles lacked limiting membranes and were adjacent to the mitochondria. Total and free carnitines in muscle were normal levels. Production rate of 14CO2 or acid-soluble [14C]metabolites from [1-14C]palmitate in the patient's cells was decreased to about 50% of that in control cells, whereas that from [1-14C]butyrate was normal. Long-chain fatty acyl esterase activities in the patient's leukocytes were normal at both pH 4.0 and pH 8.0. Despite the strong suggestion of an impaired metabolism of long-chain fatty acids, there were no evidences of abnormalities in carnitine metabolism or uptake of fatty acids into cells. The disorder is clinically different from defects in carnitine metabolism, defects in the carnitine-acylcarnitine translocase system or in mitochondrial beta-oxidation enzymes. Although the underlying metabolic defect has not been elucidated, this disease seems to be an autosomal-recessively inherited disorder of systemic triglyceride storage, probably due to an impaired regulation of lipolysis and triacylglycerol synthesis.

Carnitine↗

Effect of taurine on growth hormone and prolactin secretion in rats: possible interaction with opioid peptidergic system.

The effect of taurine on growth hormone (GH) and prolactin (PRL) secretion was investigated in the urethane-alpha-chloralose anesthetized rats, considering the interaction with endogenous opioid peptidergic system. Intraventricular injection of taurine (0.25 and 1.0 mumol) stimulated GH and PRL secretion in a dose-dependent manner. However, 4.0 mumol taurine failed to show these effect. The intravenous infusion of naloxone (4 mg/kg b.w.) completely inhibited both the GH and PRL secretion induced by taurine (1.0 mumol). The combined treatment of taurine (1.0 mumol) and FK33-824 (Met-enkephalin derivative, 100 micrograms/kg b.w., i.v.) significantly increased GH and PRL responses induced by taurine or FK33-824 alone. These results indicate that taurine is an effective stimulator of GH and PRL secretion in rats, and that the mechanism of this action involves the opioid peptidergic system in the hypothalamus.

Anesthesia↗

Phenotypes of apolipoprotein E and abnormalities in lipid metabolism in patients with non-insulin-dependent diabetes mellitus.

Phenotypic expressions of apolipoprotein E (apo E) were studied in 94 Japanese patients with non-insulin-dependent diabetes mellitus (NIDDM) and in 91 normal controls. The apo E gene frequencies observed in patients with NIDDM (epsilon 4, 0.101; epsilon 3, 0.824; and epsilon 2, 0.075) were not significantly different from those in normal controls (epsilon 4, 0.093; epsilon 3, 0.863; and epsilon 2, 0.044). Subgrouping the diabetic patients with and without hyperlipidemia, the epsilon 2 allele was significantly more frequent in patients with hypertriglyceridemia. The levels of serum triglyceride, very low density lipoprotein-cholesterol (VLDL-C), and VLDL-triglyceride (VLDL-TG) were significantly higher in patients with the epsilon 2 heterozygote than in those without the epsilon 2 allele (P less than .01). The results suggest that variation in the apo E gene may be one factor related to the hypertriglyceridemia present in patients with NIDDM.

Adolescent↗

Difference of bone marrow adipocyte colony-forming capacity between aplastic anemia and iron deficiency anemia.

The bone marrow adipocyte colony-forming capacity (Adipo-CFC) in patients with aplastic anemia (AA), myelodysplastic syndrome (MDS) and iron deficiency anemia (IDA) was studied. Before treatment, Adipo-CFC in IDA was higher than that in AA and MDS. After treatment, Adipo-CFC decreased in IDA, but it increased in AA and MDS only at the responsive stage. In this context, it is suggested that increase of Adipo-CFC occurs during not only regenerating hemopoiesis but also accelerated erythropoiesis such as severe IDA. Colony-stimulating activity (CSA) production by marrow stromal cells (MSC) in AA was lower than that in normal subjects. Low Adipo-CFC and defective CSA production by MSC may explain in part the pathogenesis of microenvironmental defect in AA.

Adipose Tissue↗

Hematopoietic growth factors (BPA and Epo) induce the expressions of c-myc and c-fos proto-oncogenes in normal human erythroid progenitors.

We investigated serial expressions of eight proto-oncogenes during in-vitro differentiation of normal human burst-forming unit, erythroid (BFU-E), and found that c-myc and c-fos are expressed in progenies of BFU-E. The expressions of the two proto-oncogenes correlated to the replating efficiency and adversely to erythroid differentiation. The absence of hematopoietic growth factors decreased the expressions, but the addition of erythropoietin together with burst promoting activity induced a re-expression of the c-myc and c-fos after 2 h of incubation. These observations suggest that the c-myc and c-fos proto-oncogenes have a physiological role in the proliferation of erythroid progenitors and that activations of the two proto-oncogenes are early cellular events after the stimulation by hematopoietic growth factors.

Cell Differentiation↗

Plasma levels of 7B2 (a novel pituitary polypeptide) and its molecular forms in plasma and urine in patients with chronic renal failure: possible degradation by the kidney.

Plasma immunoreactive (IR)-7B2 was measured in patients with chronic renal failure (CRF), using a specific radioimmunoassay. The mean (+/- S.E.M.) concentration of plasma IR-7B2 in CRF patients under hemodialysis (502 +/- 36 pg/ml, n = 27) was significantly higher than that in normal subjects (men, 52.9 +/- 1.7 pg/ml (n = 179); women, 55.8 +/- 1.3 pg/ml (n = 198]. Significant correlations between plasma levels of IR-7B2 and those of blood urea nitrogen, creatinine and beta 2-microglobulin were evident in non-dialyzed CRF patients. In the analyses of pooled plasma and urine obtained from normal subjects on gel permeation chromatography, a major peak of IR-7B2 was observed at an apparent molecular weight of 20,000 in the plasma, and at a position of a smaller molecular weight in the urine. These results suggest that 7B2 is degraded mainly in the kidney and that measurement of plasma 7B2 may serve as an appropriate tool for assessing renal function.

Adult↗

Specific phosphorylation of 22-kD proteins by various inducers for granuloid differentiation in myeloid leukemic cells.

We studied the changes of protein phosphorylation in human leukemic cells by granuloid inducers, using two-dimensional electrophoresis. The phosphorylation of 22 kD, pI 6.0 and 5.8 proteins (pp22) in HL-60 cells or myeloid leukemic cells from patients, was enhanced by treatment with granuloid inducers such as retinoic acid, dimethyl sulfoxide or G-CSF, in common with prostaglandin E2 and theophylline, or dibutyryl c-AMP, which increased intracellular c-AMP. In contrast, pp22 phosphorylation was not induced by the monocytes/macrophages inducer in HL-60 cells, or by the granuloid inducers in lymphoid cells. This phosphorylation occurred within 30 min and continued for more than 48 h. These pp22 proteins were present in the cytosol and phosphorylated on the serine residues. We now present a possibility that granuloid differentiation in myeloid cells is closely linked with these pp22 phosphorylation.

Cell Differentiation↗

Lack of inhibitory effect of alpha-human atrial natriuretic polypeptide on cortisol secretion in cultured adrenocortical adenoma cells from the patients with Cushing's syndrome.

The effects of synthetic alpha-human atrial natriuretic polypeptide (alpha-hANP) on cortisol secretion by adrenocortical adenoma cells from patients with Cushing's syndrome (CS cells) in primary monolayer cultures, compared to cultured normal adrenal cells, were studied. alpha-hANP significantly inhibited cortisol secretion by human normal adrenal cells in culture, but had no direct effect on cortisol secretion from CS cells, in the presence or absence of 10(-8) M ACTH. alpha-hANP enhanced the accumulation of intracellular cyclic GMP in normal adrenal cells in culture, but not in CS cells. Visualization of [125I] iodo-alpha-hANP-specific binding sites by an in vitro receptor autoradiographic technique showed that these sites were lacking in adrenocortical adenoma tissues. These results suggest that the loss of alpha-hANP inhibitory effect on cortisol secretion in CS cells may be due to the absence of alpha-hANP receptor sites.

Adenoma↗

Human atrial natriuretic polypeptide in plasma of patients with anorexia nervosa.

To examine the effects of chronic dehydration and starvation on plasma levels of human atrial natriuretic polypeptide (hANP) in human subjects, the basal level and saline-induced rise of plasma hANP in 7 patients with anorexia nervosa were compared with those in age-matched healthy subjects. The unstimulated level of plasma hANP was markedly high in the patients with anorexia nervosa (patients vs. control; 55.4 +/- 9.0 pg/ml vs. 11.4 +/- 6.1 pg/ml, P less than 0.01). However, no significant increase of plasma hANP in the anorectic patients was observed in response to saline-infusion, while a 3-fold increase over the basal level of plasma hANP was noted in the saline-infused normal young subjects. These results show that hANP may be secreted to an inadequate extent, hence the release would be resistant to volume-loading. The pathophysiological meaning of such a high plasma concentrations of hANP in anorexia nervosa is the subject of ongoing studies.

Adolescent↗

Possible mechanism of ineffective erythropoiesis by an altered transferrin receptor cycle in erythroleukemia.

Involvement of the transferrin receptor cycle was noted in erythroblasts from a patient with erythroleukemia (FAB classification M6). The kinetics of transferrin receptor cycle in bone marrow erythroblasts was obtained by pulse-chase experiments before the initiation of therapy. Internalization of transferrin was impaired and resulted in a delayed peak of internalized transferrin, as compared with the kinetics pattern seen in healthy subjects. The subsequent exocytosis of the internalized ligand was also delayed. Thus, transferrin receptor cycle seems to be influenced all along the transferrin pathway, hence transferrin travels more slowly in erythroblasts in erythroleukemia. The altered transferrin receptor cycle led to a diminished iron uptake per surface transferrin receptor (approximately 30% of that in healthy subjects), and the incorporation of iron into heme was greatly reduced. Our observations suggest a possible role for the altered transferrin receptor cycle in the pathogenesis of defective heme synthesis and ineffective erythropoiesis in erythroleukemia.

Endocytosis↗

Hydrocortisone modulates colony-stimulating activity produced by human bone marrow-derived adherent cells.

In an attempt to clarify the significance of hydrocortisone (HC) in human long-term bone marrow cultures, the production of colony-stimulating activity (CSA) and colony-enhancing activity (CEA) by human bone marrow-derived adherent cells (MDAC) and the modulation by HC were examined. The CSA production by MDAC was demonstrated using bilayer agar cultures. After treatment of MDAC with 10(-6) mol/l HC, the CSA production was markedly enhanced, and after treatment of macrophages with 10(-6) mol/l HC, the CSA production was inhibited. When added to a granulocyte-macrophage precursor cells (CFU-GM) assay system, HC inhibited colony formation. These results suggest that HC treatment directly stimulates CSA production by nonmacrophage cells of MDAC. The conditioned medium of the confluent layer of MDAC contained CEA, which was not influenced by the HC treatment of MDAC. Thus, HC plays an essential role in granulopoiesis in vitro, enhancing the CSA production by MDAC and inhibiting the differentiation of CFU-GM.

Bone Marrow↗

Changes in muscarinic receptors and amylase secretion in regenerating acinar cells of rat pancreas.

Atrophic pancreatic acinar cells of copper-deficient rats recovered after copper supplementation. To clarify whether the recovered cells are regenerative and amylase secretion via muscarinic receptors alters, [3H]-thymidine uptake, [3H]-quinuclidinyl benzilate binding and amylase release were studied in these rats and compared with the values of 5-day-old and 21-week-old rats. The [3H]-thymidine uptake study indicated that the recovered acinar cells were regenerative. The number of muscarinic receptors in regenerating cells was equal to that in mature cells and was one third in cells of 5-day-old rats. The apparent dissociation constant of muscarinic receptors was about 0.73 x 10(-10) M for the regenerating cells, 0.65 x 10(-10) M for 5-day-old rats, and 1.70 x 10(-10) M for 21-week-old rats. Amylase release, as a percent of total amylase, was maintained relatively steady in spite of the low amylase content in regenerating cells. These observations suggest that the affinity of muscarinic receptors increases to compensate the impaired amylase synthesis in regenerating acinar cells and that their amylase secretion via muscarinic receptors is different from that in 5-day-old or mature rats.

Amylases↗

Regulation of erythropoietin and burst-promoting activity production in patients with aplastic anemia and iron deficiency anemia.

To clarify the control mechanism of production of erythropoietic growth factors in anemic states, we compared erythropoietin (Epo) and burst-promoting activity (BPA) in patients with aplastic anemia and iron deficiency anemia, using in vitro erythroid progenitor assays. Although serum levels of Epo activity increased in the presence of anemia, the rise was more marked in patients with aplastic anemia. BPA was high only in the sera of aplastic anemia patients. Serum levels of BPA of patients with aplastic anemia negatively correlated with hemoglobin concentrations, while those of patients with iron deficiency anemia did not correlate. In 2 patients with aplastic anemia who responded well to androgen therapy, serum levels of Epo activity and BPA decreased after the hemopoiesis had recovered. These results suggest that serum levels of BPA do not rise in response to anemia only. The elevated BPA levels in sera in cases of aplastic anemia are probably related to a reduction in the number of hemopoietic stem cells. Moreover, we observed that BPA in bone-marrow-conditioned medium (BMCM) from patients with severe aplastic anemia increased more than in the BMCM from patients with severe iron deficiency anemia. Therefore, our findings suggest that the enhanced BPA production depends on a decrease in hemopoietic precursors rather than the anemic state.

Adolescent↗

Age-related changes in glucocorticoid and androgen receptors of cultured human pubic skin fibroblasts.

In order to evaluate age-related changes in glucocorticoid receptor and androgen receptor of cultured human pubic skin fibroblasts in young and aged men, we determined both [3H]dexamethasone binding and [3H]methyltrienolone (R1881, potent androgenic steroid) binding, using dispersed whole cell assay. Scatchard analyses of specific [3H]dexamethasone binding to the fibroblasts of young and aged men showed a single class of high-affinity binding sites with a mean (+/- SD) binding site concentration (Bmax) of 12.69 +/- 2.36 X 10(4) and 12.87 +/- 12.21 X 10(4) sites/cell, respectively, and mean (+/- SD) dissociation constant (Kd) of 5.60 +/- 0.41 and 7.36 +/- 2.17 nM, respectively. Scatchard analyses of specific [3H]R1881 binding to the same cultured skin fibroblasts of young and aged men showed a single class of high-affinity binding sites with a mean Bmax of 5.77 +/- 1.02 X 10(3) and 2.82 +/- 0.97 X 10(3) sites/cell, respectively, and a mean Kd of 0.56 +/- 0.23 and 0.50 +/- 0.28 nM, respectively. These findings indicate that there were no significant age-related changes in binding site and affinity of glucocorticoid receptor in cultured human pubic skin fibroblasts, whereas binding sites of androgen receptor significantly decreased in those of aged men as compared to young men, without significant change in affinity.

Adult↗