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Biomedical subjects

K Murakami

Publications and source records attributed to K Murakami.

At least 1,189 records · Page 66Linked to original sources
PubMed1982

Brain renin from bovine anterior pituitary. Isolation and properties.

Brain renin has been purified 1,670,000-fold to homogeneity from bovine anterior pituitary in seven steps, including affinity chromatography on pepstatin-aminohexyl-agarose. The molecular weight of this enzyme is 36,000 as determined by gel filtration on Ultrogel AcA 44 and by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme has an isoelectric point of 5.25 and works best at physiological pH. In contrast to renal renin, bovine brain renin fails to bind to concanavalin A and four other lectins. The angiotensin I-forming activity of the purified brain renin was completely neutralized by anti-hog renal renin antibody. Rabbit antisera against pure brain renin showed a low degree of species and tissue specificity, reacting readily with hog brain renin and bovine and hog kidney renins. These results provide definite evidence for the presence of a functional brain renin-angiotensin system.

Amino Acids↗
PubMed1982

AMP deaminase reaction as a control system of glycolysis in yeast. Activation of phosphofructokinase and pyruvate kinase by the AMP deaminase-ammonia system.

The role of AMP deaminase (EC 3.5.4.6) reaction in the stimulation of the regulatory enzymes of glycolysis was investigated using permeabilized yeast cells. 1) The addition of polyamine activated AMP deaminase in situ, resulting in the subsequent increase in ammonium production, which can stimulate the activity of 6-phosphofructokinase (EC 2.7.1.11) and pyruvate kinase (EC 2.7.1.40). 2) Zn2+ inhibited AMP deaminase activity, followed by a decrease in ammonium ion concentration which reduced the activity of phosphofructokinase. 3) Polyamine and Zn2+ did not activate or inhibit directly the activity of phosphofructokinase and pyruvate kinase. 4) A simple Michaelis-Menten relationship was observed between the various levels of ammonium ion and of fructose 1,6-biphosphate formed in situ, indicating that phosphofructokinase activity or glycolytic flux was dependent upon the level of ammonium produced through the action of AMP deaminase. 5) The increase in Pi concentration resulted in the decreased magnitude of activation by NH4+ and marked stimulation by Pi itself of phosphofructokinase, and further reduced the production of NH4+ through the inhibition of AMP deaminase, suggesting that phosphofructokinase activity may not be regulated by the level of NH4+ but by Pi concentration under conditions of increased Pi levels. The AMP deaminase-ammonium system shows a regulatory function in glycolysis of yeast cells in the presence of physiological Pi levels, whereas glycolysis may be principally controlled by Pi level under the conditions of elevated Pi concentration. Polyamines may play a part in the stimulation of glycolysis through the elevated level of ammonium ion under the conditions of increased ATP utilization during cell proliferation, and can participate in the catabolic processes as well as anabolic processes through the stimulation of the AMP deaminase-ammonium system.

AMP Deaminase↗
PubMed1982

Simultaneous determination of chlorpromazine and levomepromazine in human plasma and urine by high-performance liquid chromatography using electrochemical detection.

A rapid, selective and sensitive method for the simultaneous determination of chlorpromazine and levomepromazine in human plasma and urine has been developed using high-performance liquid chromatography with electrochemical detection. The unchanged drugs and internal standard extracted from plasma and urine were separated by reversed-phase high-performance liquid chromatography. The influence of acetonitrile concentration and of the pH of the mobile phase were investigated. The detection limits were 100 pg for chlorpromazine and for levomepromazine. In comparison with three other detection systems this was found to be the most sensitive method. This method was successfully applied to the simultaneous determination of chlorpromazine and levomepromazine in human plasma and urine for pharmacokinetic studies.

Chlorpromazine↗
PubMed1982

Presence of insulin-like immunoreactivity and its biosynthesis in rat and human parotid gland.

Extracts from homogenates of rat and human parotid glands contained insulin-like immunoreactivity. The values were 5.6 +/- 2.8 ng/g wet tissue in six groups of rat parotid glands and 23.8 and 39.7 ng/g wet tissue in two human extracts. Upon gel filtration immunoreactive insulin of rat origin was eluted in a peak corresponding to the elution volume of isotopically labelled insulin. The material obtained from the two peak fractions showed an immunoassay dilution curve identical with that of rat insulin. Furthermore, biosynthesis of insulin-like immunoreactivity in rat and human parotid glands was confirmed in vitro by a specific separation method using anti-insulin antibody. These findings suggest that the parotid gland may be a further extrapancreatic source of insulin, and that insulin biosynthesis does occur in extrapancreatic tissues.

Animals↗
PubMed1982

Optimal association with partly missing key vectors.

A new association scheme which can still recall appropriate data when some key elements are missing (blank) is presented. The traditional associative memory models are designed to deal with complete (memorized) keys, but in the real world, key elements are often missing due to error, equipment failure, observation difficulty, etc. The traditional models, in this case, can not have an optimal association except for special cases. When an incomplete key containing blanks is given, we wish to get the same data, as nearly as possible, as would be obtained with the complete key. In this paper, the optimal associative memory model which operates with partly missing keys is proposed. The model is constructed on the basis of the theory of the pseudoinverse of matrices. Even from the incomplete keys which contain a large percentage of blanks, the model recalls the appropriate data optimally under the MSE criterion. From the results of computer simulations, we can show that the model has the expected ability.

Animals↗
PubMed1982

Activation of kidney prorenin by kidney cathepsin B isozymes.

Kidney protein was converted to a form of active renin by kidney cathepsin B isozymes. The three isozymes showed similar catalytic behavior for prorenin. The optimal pH for the activation was in the range of 4.0-5.0 and the reaction was completely inhibited by leupeptin. The molecular weight and the isoelectric point of the activated prorenin were 40,000 and pH 4.9. As a minor product, an activated prorenin having an isoelectric point of 5.2 was also produced.

Animals↗
PubMed1982

Polypeptide elongation factors of the developing chick brain.

The polypeptide elongation factors (EF-1L, EF-1H, and EF-2) of the developing chick brain were separated and purified by means of a combination of gel chromatographic methods. The molecular weight of EF-1H of the chick brain ranged from 5 to 10 x 10(5), and was different from that of the chick liver (about 7 x 10(5). The molecular weight of other purified factors was about 5 x 10(4) for EF-1L and 9.4 x 10(4) for EF-2. High activities of polyphenylalanine (poly-Phe) synthesis per mg protein in the developing chick brain were observed between the 3rd embryonic week and the 1st post-hatch week and declined afterwards. On the other hand, the levels of both EF-1 and EF-2 per mg protein in the brain were observed to be high in an early embryonic stage, gradually declining afterwards to the adult level. The brain EF-1L was a major component of EF-1 in an early embryonic stage, while EF-1H became recognizable in the 3rd embryonic week. Moreover, the EF-1H activities were found to be more than double with regard to the binding reaction and to be more than 10-fold as active in respect to poly-Phe synthesis in comparison with the activities of EF-1L. It is proposed that the brain EF-1H could be due to aggregates consisting of Ef-1L, a stimulatory factor, and other components.

Animals↗
PubMed1982

Effects of calmodulin antagonists on tension and cellular calcium content in depolarized vascular and intestinal smooth muscles.

1 Several putative calmodulin antagonists have been examined for their inhibitory action on muscle tension and cellular Ca content in the K-depolarized vascular and intestinal smooth muscles. 2 The 65.4 mM K-induced sustained contraction in the media-intimal layer of rabbit aorta and the 45.4 mM K-induced sustained contraction in guinea-pig taenia coli were inhibited by the calmodulin antagonists, prenylamine, chlorpromazine, N2-dansyl-L-arginine-4-t-butylpiperadine amide (No. 233), and N-(6-aminohexyl)-5-chloro-1-naphthalenesulphonamide (W-7), and also by the organic Ca antagonists, verapamil and diltiazem. 3 The cellular Ca content in rabbit aorta and guinea-pig taenia coli as measured by a modified lanthanum technique increased in the high-K solutions. The increments were inhibited by these antagonists at concentrations similar to those required to inhibit the K-induced contractions. However, W-7 did not change (in aorta) or only slightly decreased (in taenia coli) the K-induced increase in the cellular Ca content. 4 A high concentration (2 X 10(-4)M) of W-7 increased the resting cellular Ca content without increasing the muscle tension in aorta. The increment was inhibited by verapamil, sodium nitroprusside or hypoxia (N2 aeration). 5 It is suggested that the inhibitory effects of prenylamine, chlorpromazine and No. 233 may be attributed mainly to the Ca antagonistic effect whereas W-7 may inhibit the process beyond the transmembrane Ca influx.

Animals↗
PubMed1982

Penetration of cephalosporins and corresponding 1-oxacephalosporins through the outer layer of Gram-negative bacteria and its contribution to antibacterial activity.

1-Oxacephalosporins had a higher ability to penetrate through the outer layer of the envelope of gram-negative bacteria than the corresponding cephalosporins. In spite of the liability of 1-oxa congeners to beta-lactamases, they attained higher periplasm concentrations at a given concentration outside the cells. The replacement of sulfur in the cephem nucleus by oxygen was accompanied by an increment of the hydrophilic character of the molecule, which suggests that this character was favorable for outer layer penetration. 1-Oxacephalosporins showed enhanced antibacterial activity in short-term measurement and exerted their antibacterial action at lower periplasm concentrations. Thus, the enhanced antibacterial activity of 1-oxacephalosporins seems to be due to their higher penetrability and their intrinsic inhibitory activity against the peptidoglycan biosynthesis system.

Absorption↗
PubMed1982

Responses of active and inactive plasma renin and changes in urinary kallikrein and plasma prekallikrein to various conditions in normal subjects.

Little is known about changes in inactive plasma renin in various conditions or the in vivo activation mechanism of inactive renin. The effects of various factors known to stimulate or suppress renin release on active and inactive PRA were examined in normal subjects. Inactive PRA was determined as the difference between the total PRA after trypsin activation and active PRA. Concurrent measurements of urinary kallikrein excretion and plasma prekallikrein activity were performed to assess the possible role of renal or plasma kallikrein in in vivo activation of inactive renin. Short term stimulation with iv furosemide and ambulation, infusion of isoproterenol, and administration of captopril increased active PRA, but had little or no effect on inactive PRA. Sodium restriction and sodium loading, each for 4 days, induced parallel changes in active and inactive PRA. The administration of propranolol for 4 days decreased active PRA but did not change inactive PRA. There were no significant correlations between the changes in urinary kallikrein excretion and those in active PRA or in the proportion of active to total PRA after any short term treatments, except furosemide administration. Plasma prekallikrein activity was correlated with the proportion of active renin only during the long term sodium balance study. The present data suggest that the mechanisms ofr the control of inactive and active renin are different. Neither renal nor plasma kallikrein seems to be consistently involved in the in vivo activation of inactive renin.

Adult↗
PubMed1982

The effect of serotonin agonist 1-(trifluoromethylphenyl)-piperazine on corticotropin releasing factor and arginine vasopressin in rat hypothalamic nuclei.

Effects of 1-(m-trifluoromethylphenyl)-piperazine, a serotonin agonist, were examined on rat plasma levels of adrenocorticotropin (ACTH) and arginine vasopressin (AVP), and on hypothalamic contents of corticotropin releasing factor (CRF) and AVP, to investigate the role of brain serotonin in ACTH regulation. Both plasma ACTH and AVP levels increased markedly 30 min after injection of the compound and were still elevated at 80 min. CRF and AVP contents in the median eminence decreased 30 min after injection but returned to the basal levels by 80 min. The AVP content in the supraoptic nucleus was elevated 80 min after injection. The CRF and aVP content did not significantly change in the paraventricular, suprachiasmatic and arcuate nuclei. Serotonin or 1-(m-trifluoromethylphenyl)-piperazine did not stimulate the release of ACTH in pituitary cell cultures. These results suggest that both CRF and AVP were secreted into the portal vessels by 1-(m-trifluoromethylphenyl)-piperazine to release ACTH from the anterior pituitary and that both the ACTH and AVP release were stimulated via the brain serotonergic mechanism.

Adrenocorticotropic Hormone↗
PubMed1982

Modulation of somatostatin release by endogenous glucagon and insulin: physiological relationship between A, B and D cells in rat pancreatic islets.

In order to understand the physiological role of endogenous insulin or glucagon in somatostatin release, isolated rat pancreatic islets were treated with antiinsulin or antiglucagon antiserum in the presence of physiological amounts of glucose. The release of somatostatin was unchanged by treatment with antiinsulin antiserum which neutralized insulin released by 3.3, 8.3 and 16.7 mM of glucose. However, somatostatin release after treatment with antiglucagon antiserum was much reduced at all concentrations of glucose when compared with the release from control serum. Exogenous rat insulin (0.11, 1.11 micrograms/ml) had no effect, but exogenous glucagon (1, 5 micrograms/ml) resulted in a significant increase. Somatostatin release was stimulated by glucose, but the effect was insignificant. These results clearly indicate the physiological role of endogenous glucagon in the modulation of somatostatin release from the islets of Langerhans. Furthermore, the physiological relationship between A, B and D cells may be mediated through the paracrine mechanism.

Animals↗
PubMed1982

Dynamic responses of active and inactive renin and plasma norepinephrine during exercise in normal man.

Active and inactive plasma renin, plasma angiotensin II, and plasma norepinephrine were measured during graded exercise. Five health subjects exercised on bicycle ergometer at three different loads (50, 70, and 100% of maximal oxygen uptake). Active plasma renin and plasma angiotensin II were elevated significantly during graded exercise, but plasma inactive renin decreased during the heaviest exercise; the mean ratio of active renin to total renin increased from 57 to 92% after the heaviest load. Plasma norepinephrine was also elevated during graded exercise. There is a positive correlation between plasma norepinephrine and active plasma renin during graded exercise (r = 0.916, p less than 0.01). Similar norepinephrine and active renin responses to graded exercise suggest that the mechanism(s) for activation of inactive renin and the release of active renin from the kidney may be partially related to sympathetic nervous system activity.

Adult↗
PubMed1982

Coma preceded by severe dysphagia in type II diabetes mellitus.

A 62-year-old man with 11 years' duration of type II diabetes was hospitalized because of non-ketotic diabetic coma. He had never noted any symptoms of swallowing difficulty until 3 days before admission when they developed gradually and he became comatous. He had never received special medication such as diuretics except anticonvulsants. Even after the recovery from diabetic coma he could hardly swallow solid foods or saliva for about 15 days, but these symptoms subsided gradually. Motility dysfunction of esophagus and pharynx in diabetes mellitus, in most cases they are mild, has been described, although diabetic coma preceded by dysphagia has not been documented except in one report. We studied, therefore, the autonomic nerve function of the present patient and discussed the relationship between dysphagia and diabetic coma together with the description of the clinical course of this patient. The relationship between this case and the previously reported cases were compared in terms of the sex, age, type of diabetes, clinical course, medication and the autonomic nerve function.

Autonomic Nervous System Diseases↗