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K Murakami

Publications and source records attributed to K Murakami.

At least 1,117 records · Page 62Linked to original sources
PubMed1984

Structure of the human renin gene.

The human renin gene was isolated from a Charon 4A human genomic library and characterized. The gene spans about 11.7 kilobases and consists of 10 exons and 9 introns that map at points that could be variable surface loops of the enzyme. The complete coding regions, the 5'- and 3'-flanking regions, and the exon-intron boundaries were sequenced. The active site aspartyl residues Asp-38 and Asp-226 are encoded by the third and eighth exons, respectively. The extra three amino acids (Asp-165, Ser-166, Glu-167) that are not present in mouse renin are encoded by the separate sixth exon, an exon as small as 9 nucleotides. The positions of the introns are in remarkable agreement with those in the human pepsin gene, supporting the view that the genes coding for aspartyl proteinases have arisen as the result of duplication of a common ancestral gene. As in most eukaryotic genes, the putative T-A-T-A and C-A-A-T sequences, which may play a role in the initiation of gene transcription, are found in the vicinity of -29 and -51 nucleotides of the cap site. Further upstream, at nucleotides -456 to -451, is located the hexanucleotide T-G-T-T-C-T, which has recently been suggested as a binding site for the glucocorticoid receptor. In the 3'-flanking region, there is the conserved hexanucleotide sequence A-A-T-A-A-A, thought to be necessary for polyadenylylation. Blot-hybridization analyses of the isolated gene clone and the total cellular DNA after digestion with restriction enzymes revealed that human renin is encoded by a single gene.

Amino Acid Sequence↗
PubMed1984

Clofibrate enhances the affinity of insulin receptors in non-insulin dependent diabetes mellitus.

Glucose-lowering mechanism by clofibrate was studied in non-insulin dependent diabetics managed with dietary therapy alone. Clofibrate 1500 mg was administered for 1 month to 15 patients, and 75 g oral glucose tolerance test and insulin tolerance test were carried out before and after 1 month of the treatment. Fasting plasma glucose values were decreased from 9.34 +/- 0.53 mmol/l to 7.58 +/- 0.33 mmol/l (P less than 0.01), and fasting insulin levels were decreased from 13.8 +/- 1.7 microunits/ml to 10.1 +/- 1.5 microunits/ml (P less than 0.05). However, insulinogenic index and sigma IRI/sigma glucose ratio during 75 g oral glucose tolerance test were not changed. Enhanced glucose fall in insulin tolerance test was also observed. As these results suggested the enhanced tissue sensitivity to insulin, we examined the insulin binding to erythrocytes before and at 3 months' treatment of clofibrate in 10 non-insulin dependent diabetics. Insulin bindings were increased from 3.41 +/- 0.17% to 4.11 +/- 0.20% in the presence of 1 ng/ml of native insulin (P less than 0.01). This increased binding was due to an increased affinity without a change in the number of insulin receptors. These results suggest that improved glucose tolerance by clofibrate might be derived from the enhanced tissue sensitivity to insulin, probably through an enhanced affinity of insulin receptors.

Blood Glucose↗
PubMed1984

Nitroglycerine-induced biphasic relaxation in vascular smooth muscle of rat aorta.

Nitroglycerine induced biphasic relaxation in the rat aorta, previously contracted by noradrenaline; a rapid decrease in tension was followed by a gradual increase reaching a steady level below the control contractile tension. No initial transient relaxation was induced by nitroglycerine in high K-stimulated muscle. The initial transient relaxation, but not the sustained relaxation, was dependent on the concentration of external K; maximum relaxation was observed in the presence of 2.7 mM K solution and only a slight relaxation was observed in 0 mM or 10.8 mM K solution. The initial transient relaxation was also inhibited by ouabain or low Na solution. On an appropriate increase in the concentration of external K, noradrenaline-induced contraction was transiently relaxed. Previous application of nitroglycerine potentiated this K-induced relaxation. Pretreatment of the muscle with methylene blue, an inhibitor of guanylate cyclase, inhibited both the initial transient and the sustained relaxations induced by nitroglycerine, but not the K-induced transient relaxation. It is suggested that the nitroglycerine-induced initial transient relaxation, but not the sustained relaxation, may be due to a stimulation of an electrogenic Na pump. Both relaxation phases may be mediated by cyclic GMP.

Animals↗
PubMed1984

Interaction of synthetic ovine corticotropin releasing factor and arginine vasopressin on in vitro ACTH release by the anterior pituitary of rats.

Synthetic ovine corticotropin releasing factor (CRF) at 0.03-30 ng/ml evoked a significant linear release of ACTH in pituitary monolayer cell cultures. Arginine vasopressin (AVP) at 3-30 ng/ml induced a slight ACTH release in the same culture system. CRF at 100 ng/ml greatly increased the medium ACTH with intracellular ACTH remaining relatively constant. In perifused pituitary quarters, both AVP and CRF evoked significant release of ACTH. When AVP was added in combination with synthetic ovine CRF, an additive or synergistic effect was observed on the CRF-induced ACTH release in both in vitro systems. Preincubation of cultured pituitary cells with synthetic ovine CRF for 1 h did not have a significant effect on the subsequent AVP-induced ACTH release. However, when cells were preincubated for 6 h with CRF at 1 and 100 ng/ml, the AVP-induced ACTH release was significantly increased, but preincubation with AVP suppressed both the basal and AVP-induced ACTH release. These results suggest that synthetic ovine CRF stimulates not only the release of ACTH but also the synthesis of ACTH and that AVP can evoke significant ACTH release from corticotrophs which have enough releasable ACTH or substances needed for ACTH release under the influence of CRF.

Adrenocorticotropic Hormone↗
PubMed1984

Reduction in the mitochondrial membrane potential of Toxoplasma gondii after invasion of host cells.

The membrane potential of Toxoplasma gondii, an obligatory intracellular protozoan parasite, was monitored with the cationic permeant fluorescent dye rhodamine 123 (R123). Fluorescence microscopy revealed R123 to be partitioned predominantly in a restricted part of the parasite, which consisted of twisted or branched tubules, or of granular bodies. These structures were frequently connected to each other. The dye retention by these structures was markedly reduced by treating R123-labelled parasites with the proton ionophore, carbonylcyanide m-chlorophenylhydrazone, the potassium ionophore, valinomycin and the inhibitor of electron transport, antimycin A. Thus, these structures are regarded as the parasite mitochondria. Another cationic fluorescent dye, rhodamine 6G, stained the parasite mitochondria, whereas a negatively charged fluorescent dye, fluorescein, and the neutral compounds, rhodamine 110 and rhodamine B, did not. This fact indicates that R123 monitored the parasite mitochondrial membrane potential. T. gondii-infected 3T3 cells were also stained with R123. In contrast to the mitochondria of extracellular parasites, those of intracellular parasites failed to take up the dye. The absence of fluorescence in intracellular parasites persisted until the infected host cells ruptured and liberated daughter parasites 1 day after infection. Parasites, liberated from the host cells, either spontaneously or artificially by passing the infected cells through a 27G needle, regained the ability to take up the dye. After direct microinjection of R123 into the vacuole in which the parasite grows and multiples, the dye appeared in the host-cell mitochondria but not in the parasite's mitochondria. Thus, we conclude that the mitochondrial membrane potential of T. gondii was reduced after invasion of host cells by the parasite.

Animals↗
PubMed1984

Corticotropin releasing factor (CRF)-like immunoreactivity in the hypothalamus and posterior pituitary of the goat, bovine, rat, monkey and human.

Goat hypothalamic extract prepared by HCl extraction and chromatographed on a Sephadex G-50 column showed two immunoreactive CRF peaks. Most of the immunoreactivity coeluted with synthetic ovine CRF, and a small peak eluted near the void volume. Bovine, monkey, rat and human hypothalamic extracts prepared by acid-acetone or acid-methanol extraction showed three immunoreactive peaks. Most of the immunoreactivity coeluted with ovine CRF, and other smaller peaks eluted near the void volume and slightly before arginine vasopressin. Goat hypothalamic extract showed the highest cross-reactivity with anti-ovine CRF serum, followed by bovine hypothalamic extract. Less cross-reactivity was found in human, rat and monkey hypothalamic extracts. CRF immunoreactivity in goat hypothalamic extract coeluted with ovine CRF on reversed phase high performance liquid chromatography (HPLC) and main CRF immunoreactivity in human and rat hypothalamic extracts eluted slightly later than ovine CRF. These results suggest that there is a heterogeneity among the CRF molecules in these species and that goat CRF may be more similar to that of sheep CRF and the amino acid sequence or molecular weight of other animals CRF may be different from that of sheep CRF. The monkey posterior pituitary and rat neurointermediate lobe showed similar elution patterns of CRF immunoreactivity to their hypothalamic extracts on Sephadex gel filtration and HPLC. These results indicate that the posterior pituitary contains a similar CRF to hypothalamic CRF.

Animals↗
PubMed1984

Effect of angiotensin II, catecholamines and glucocorticoid on corticotropin releasing factor (CRF)-induced ACTH release in pituitary cell cultures.

The effects of angiotensin II, catecholamines and glucocorticoid on CRF-induced ACTH release were examined using rat anterior pituitary cells in monolayer culture. Synthetic ovine CRF induced a significant ACTH release in this system. Angiotensin II produced an additive effect on CRF-induced ACTH release. The ACTH releasing activity of CRF was potentiated by epinephrine and norepinephrine. Dopamine itself at 0.03-30 ng/ml did not show any significant effect on ACTH release, but it inhibited CRF-induced ACTH release. Corticosterone at 10(-7) and 10(-6)M inhibited CRF-induced ACTH release. These results indicate that angiotensin II, catecholamines and glucocorticoid modulate ACTH release at the pituitary level.

Adrenocorticotropic Hormone↗
PubMed1984

Synergistic interaction of corticotropin releasing factor and arginine vasopressin on adrenocorticotropin and cortisol secretion in Macaca fuscata.

Plasma immunoreactive CRF measured by radioimmunoassay decreased rapidly after intravenous injection of synthetic ovine corticotropin releasing factor (CRF) and showed a bi-exponential decay curve in five macaca fuscatas. Half lives of plasma immunoreactive CRF were 5.8 +/- 1.4 (Mean +/- SEM) min for the fast component and 38.3 +/- 2.4 min for the slow component. A bolus injection of 5 micrograms/kg CRF significantly increased the plasma cortisol level. CRF at 5 micrograms/kg induced a delayed response of ACTH and cortisol. Arginine vasopressin (AVP) at 0.5 micrograms/kg induced a slight increase in plasma ACTH and cortisol, but AVP at 0.1 micrograms/kg evoked no significant increase. When 0.5 micrograms/kg CRF and 0.1 micrograms/kg AVP were administered simultaneously, significant ACTH and cortisol responses occurred. The results indicate that CRF and AVP act synergistically to stimulate ACTH secretion in vivo.

Adrenocorticotropic Hormone↗
PubMed1984

The effects of insulin on the cardiovascular system in patients with coronary heart disease.

In order to clarify the effects of insulin on the cardiovascular system in patients with and without coronary heart disease (CHD), we studied the changes of electrocardiogram (ECG), blood pressure, pulse rate, along with those of blood glucose, free fatty acid, immunoreactive insulin, cortisol and potassium during insulin tolerance test (ITT). The presence or absence of CHD was verified by the coronary angiography and various stress testings beforehand. In patients with CHD, ischemic ST-T wave changes were recorded following the increment of double product after insulin injection and these changes were quite similar to those recorded during exercise test. In patients without CHD, although hypoglycemia and suppression of lipolysis were achieved, ischemic ST-T wave changes were not recorded after insulin injection. Furthermore, in a patient with Triple Vessel Disease, ischemic changes of ECG provoked by ITT were abolished completely by the administration of nifedipine and propranolol. ITT may induce ischemic changes of ECG in patients with CHD by different mechanisms from those of exercise tests and it may provide a useful tool for the diagnosis of CHD in clinical applications.

Aged↗
PubMed1984

Biochemical and immunohistochemical localization of renin in human pituitary.

The renin content of human pituitaries obtained at autopsy of eight patients (four males and four females) within 3 hours after death from various diseases was determined. The pituitaries contained a significant amount of renin (5.5 +/- 1.6 mg of angiotensin I/mg of protein/hour). Although much less (1/1000) than that in human kidneys (4.5 micrograms of angiotensin I/mg of protein/hour), this content was about 10 times higher than that in normal plasma (0.5 ng of angiotensin I/mg of protein/hour). More than 50% of the renin activity was inhibited by antihuman renin antibody. These results are the first detection of a significant amount of renin in the human pituitary. No difference in pituitary renin content between males and females was detected; the pituitaries from the two youngest patients showed the highest levels. Immunohistochemical staining showed no positive cells in the intermediate and posterior lobes and many positive cells in the anterior lobe. Serial sections were examined, and renin-containing cells were immunohistochemically identified as polactin-producing cells without distinction as to the sex of the donor. This demonstration of the intracellular presence of immunoreactive renin lends strong support to the idea that renin is not a contaminant of pituitary preparations due to entrapped plasma, but is endogenous to the human pituitary.

Adolescent↗
PubMed1984

A new sensitive direct radioimmunoassay for human plasma renin and its clinical application.

We developed new sensitive direct radioimmunoassay for human plasma renin. Renin was purified from Haas' preparation utilizing a pepstatin-C6-Sepharose affinity chromatography. Antiserum, prepared by immunizing rabbits with the purified renin, was used for the direct radioimmunoassay at a final dilution of 1:30,000. The antibody was specific for human renal and plasma renin, but did not cross-react with cathepsin D, trypsin, or renins of mouse, dog, and rat. Radioimmunoassay was performed by the double antibody technique using the delayed tracer addition method. In this method, a standard curve was obtained over a range from 0.2 to 8.0 ng/ml. The values from our assay correlated well with total renin activity measured as the generation rate of angiotensin I after trypsin activation (r = 0.78, p less than 0.01), but correlated weakly with active renin activity. This finding disclosed that both active and inactive renin were detected by this method. In normal participants, plasma renin concentration determined by direct radioimmunoassay was increased by standing and furosemide injection. The plasma renin concentration determined by direct radioimmunoassay of patients with essential hypertension (0.7 to 1.7 ng/ml) was not significantly different from values in normal controls (0.8 to 1.9 ng/ml). The values were higher in patients with renovascular hypertension (1.6 to 2.7 ng/ml), malignant hypertension (2.8 to 3.4 ng/ml) and Bartter's syndrome (1.8 to 2.5 ng/ml), but lower in patients with primary aldosteronism (0.4 to 0.8 ng/ml) than in normal controls. This newly developed radioimmunoassay for human renin was sensitive enough to estimate the levels of renin in plasma of patients with low renin hypertension. It provides a new tool for the understanding of the renin-angiotensin system under various clinical conditions.

Adult↗