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Biomedical subjects

R Kato

Publications and source records attributed to R Kato.

At least 433 records · Page 24Linked to original sources
PubMed1989

Expression of a human P-450IIC gene in yeast cells using galactose-inducible expression system.

A cDNA of a human liver cytochrome P-450, corresponding to P-450 human-2, was expressed in Saccharomyces cerevisiae cells by the use of a galactose-inducible expression vector containing the GAL7 promoter and terminator. In Western blots using anti-P-450 human-2 IgG, a single band, which exhibited mobility identical to that of authentic P-450 human-2 purified from human liver, was detected in microsomes of the yeast cells. The amount synthesized in yeast was estimated to be approximately 1% of the total cell protein, and approximately 25% of the cytochrome existed in the holoenzyme state. Microsomes from the P-450 human-2-producing yeast showed a catalytic activity towards benzo(a)pyrene, and the activity was significantly enhanced by the addition of purified NADPH-cytochrome P-450 reductase. The yeast microsomes also catalyzed (S)-mephenytoin 4-hydroxylation but not the demethylation. The present results indicate that the yeast cells containing P-450 human-2 cDNA synthesize a functionally active form of the enzyme, the chemical and catalytic properties of which are identical to those of the human liver preparation.

Antigen-Antibody Reactions↗
PubMed1989

Regulation of hepatic cortisol sulfotransferase in rats by pituitary growth hormone.

Cytosolic sulfating activities of 4-pregnen-11 beta, 17 alpha, 21-triol-3,20-dione (cortisol) to the 21-sulfate were 4 to 5 times higher in livers of female than male adult rats. The activity was decreased by administration of testosterone propionate (TP) to ovariectomized, but not to intact, female rats. In male rats, the rate of cortisol sulfation was elevated by neonatal castration and was restored in part by the administration of TP to the castrated rats. In addition, the sulfating activity in adult male rats was increased by the treatment with estradiol benzoate. Hypophysectomy almost completely decreased cytosolic cortisol-sulfating activity in male rats. The activity in hypophysectomized male rats was not increased by the treatment with hydrocortisone, TP, estradiol benzoate, or somatomedin C but was restored by the intermittent injection of human growth hormone (hGH). Further, the continuous infusion of hGH, to mimic the female secretory pattern, increased more efficiently the rate of cortisol sulfation. Hypophysectomy of female rats also decreased, but not completely, the sulfating activity. Treatment of female hypophysectomized rats intermittently with hGH had no appreciable effect, but the continuous infusion increased the activity effectively. The involvement of pituitary growth hormone in the hepatic cortisol sulfation was also supported by the experiment using neonatally glutamate-treated rats and by the observation of developmental changes in the cortisol-sulfating activity. These results indicate that pituitary growth hormone is one of the major factors regulating hepatic levels of cortisol sulfation in rats and that the higher activity in the female than the male is due mainly to the difference in the secretory pattern of growth hormone in the adult animals.

Age Factors↗
PubMed1989

[The prognosis of intermittent claudication].

The purpose of this study is to obtain the informations about the fate of the limbs and lives of claudicants due to arteriosclerosis obliterans. Two hundred and seven lower limbs of 165 patients suffering from intermittent claudication were observed for an average period of about six years. Eighty-seven limbs of 69 patients were managed nonsurgically (Group A). Ninety-eight percent of limbs in Group A remained unchanged or improved, and no limb was amputated. One hundred and twenty limbs of 96 patients had arterial reconstructions (Group B). Although 75 percent of limbs in Group B had benefits by successful operations, 26 percent of them experienced graft failures, and 2.7 percent of them were amputated. Five year graft patency rates in the limbs with supra- and infra-inguinal reconstructions were 82.1 percent and 65.7 percent, respectively. Operative mortality rate was 2.1 percent, and mortality rate due to late complications was 3.3 percent. The prognosis of intermittent claudication with regular follow-up was relatively good, therefore, it is important to recognize that arterial reconstruction is not the only way to treat limbs with mild intermittent claudication. About 30 percent of claudicants died within 5 years, and 60 percent of them died from cardiac or cerebrovascular disease. The results suggested that much attention should be paid to the lives as well as the limbs of claudicants.

Aged↗
PubMed1989

Traumatic pulmonary pseudocyst. Report of twelve cases.

Twelve cases of traumatic pulmonary pseudocyst were seen between January 1966 and July 1987 at Saiseikai Kanagawaken Hospital. The cause of the traumatic pulmonary pseudocyst was closed blunt chest trauma in all patients. For the first few days after the injury, computed tomographic scan was more useful in diagnosis than chest roentogenogram. Tube drainage of the pleural cavity was performed in 10 patients who had hemothorax or hemopneumothorax, and antibiotics were administered to all patients. No patient underwent a surgical procedure, and all traumatic pulmonary pseudocysts eventually resolved, without any specific treatment, within 1 to 4 months (average 1.8 month) after the trauma. We conclude that pulmonary resection is not indicated except in the rare instance in which the traumatic pulmonary pseudocyst becomes infected.

Adolescent↗
PubMed1988

Gene conversion and differential regulation in the rat P-450 IIA gene subfamily. Purification, catalytic activity, cDNA and deduced amino acid sequence, and regulation of an adult male-specific hepatic testosterone 15 alpha-hydroxylase.

Previous studies on regulation of the rat hepatic P-450 IIA1 cDNA have provided evidence for a second gene closely related to but regulated in a manner quite distinct from P-450 IIA1. Experiments were carried out to isolate the cDNA for this second P-450 gene, designated IIA2, in order to study more directly its regulation and relationship to IIA1. A full length cDNA to IIA2 was isolated from an adult male rat liver lambda gt11 library and sequenced completely. The IIA2 cDNA shared 93% nucleotide and 88% deduced amino acid similarities with the previously characterized IIA1 cDNA (Nagata, K., Matsunaga, T., Gillette, J., Gelboin, H. V., and Gonzalez, F. J. (1987) J. Biol. Chem. 262, 2787-2793). The protein, deduced from the cDNA, contained 492 amino acids and a calculated Mr of 56,352. Comparison of the IIA1 and IIA2 cDNAs revealed areas of low nucleotide similarity interspersed with areas of absolute identity, suggesting that gene conversions have played a role in the evolution of the IIA subfamily. Expression of IIA1 and IIA2 mRNAs in rat liver during development was studied with use of specific oligonucleotide probes. IIA1 mRNA was increased within 1 week after birth in both male and female rats; however, its postpubertal expression was decreased in males yet remained elevated in females. In contrast, IIA2 mRNA was markedly induced in male rat liver at puberty but was not detectable in females at any age examined. Furthermore, only IIA1 mRNA was induced by treatment of rats with 3-methylcholanthrene. Although IIA1 and IIA2 mRNAs were actively expressed in hepatic tissue, no evidence for their expression was found in lung, kidney, or intestine, suggesting that the IIA genes have tissue-specific promoters. Reconstituted enzyme assays on the purified protein products P-450 IIA1 and P-450 IIA2 showed that, although both enzymes share considerable sequence similarity, their positional specificities toward the prototype substrate testosterone are strikingly different.

Amino Acid Sequence↗
PubMed1988

[Studies on serum ketone bodies in patients with hyperthyroidism].

In order to investigate effects of thyroid hormone on ketone bodies metabolism, fasting levels of serum ketone bodies, serum free fatty acids (FFA), serum insulin (IRI), plasma glucagon (IRG) and plasma glucose were examined in 29 untreated patients with hyperthyroidism and 20 healthy subjects. In 21 patients the levels of serum ketone bodies were re-examined when euthyroidism was achieved after treatment. In all of healthy subjects and 17 patients changes in the levels of serum ketone bodies after oral glucose load were examined. The results were as follows: 1). Fasting levels of serum FFA and total ketone bodies (TK), acetoacetate (AcAc), 3-hydroxy-beta-butylate (3OHBA), ratio of 3OHBA to AcAc in the patients were significantly higher than those in healthy subjects. The levels of IRI, IRG or ratio of IRG to IRI in the patients were not different from those in healthy subjects. In the patients, the fasting level of TK was significantly correlated with the level of FFA. 2). After oral glucose load the levels of TK and FFA in the patients decreased gradually. 3). The fasting levels of TK and FFA in the patients decreased when euthyroidism was achieved after treatment. It was suggested that the fasting levels of serum ketone bodies in patients with hyperthyroidism elevated probably due to activated lipolysis.

Blood Glucose↗
PubMed1988

Alteration of hepatic drug metabolizing activities and contents of cytochrome P-450 isozymes by neonatal monosodium glutamate treatment.

By the treatment of newborn male rats with monosodium glutamate (MSG), microsomal benzo[a]pyrene hydroxylation, propoxycoumarin O-depropylation, and testosterone (T) 6 beta- and 2 beta-hydroxylations in the adult rats were decreased significantly, while microsomal aniline and T 7 alpha-hydroxylations were increased. However, the treatment of newborn female rats did not significantly alter any of the drug-metabolizing activities examined, except that T 6 beta-hydroxylation and androstenedione formation were slightly increased. The hepatic contents of male-specific cyt. P-450, P-450-male and P-4506 beta, which show high catalytic activities on respective T 16 alpha/2 alpha-, and T 6 beta/2 beta-hydroxylations, decreased in MSG-treated male rats. The level of the female specific enzyme, P-450-female, slightly decreased in the MSG-treated female rats, whereas higher phenobarbital (PB)-induction of PB-inducible isozymes, P-450b and P-450e, was observed in MSG-treated than in control female rats. These results are consistent with the idea that disruption of a pulsatile secretion of growth hormone, which is induced by the neonatal MSG treatment, leads to changes in drug metabolizing activities through the alteration of the levels of sex-specific cyt. P-450s, but also indicate that MSG-treated rats are not an animal model equivalent to hypophysectomized rats.

Animals↗
PubMed1988

Functional shift from muscarinic to nicotinic cholinergic receptors involved in inositol trisphosphate and cyclic GMP accumulation during the primary culture of adrenal chromaffin cells.

Specificities of cholinergic receptors for the accumulation of inositol trisphosphates (InsP3) and cyclic GMP and mobilization of intracellular Ca2+ in relation to culture periods were investigated in primary cultures of bovine adrenal chromaffin cells. At 0.5 day in culture, muscarine, a specific agonist for muscarinic receptors, caused a greater effect on intracellular Ca2+ mobilization and the accumulation of Ins(1,3,4)P3 than did the nicotinic-specific agonist nicotine. On the contrary, at 5 days, nicotine produced a greater effect on the accumulation of Ins(1,3,4)P3 and intracellular calcium mobilization than did muscarine. Furthermore, at 0.5 day, the muscarinic antagonist atropine strongly inhibited the increase in InsP3 accumulation that was induced by the nonspecific agonist carbachol, whereas at 5 days the inhibitory effect of atropine was greatly lowered. On the other hand, the nicotinic receptor antagonists hexamethonium and d-tubocurarine showed a much higher inhibitory potency at 5 days compared with 0.5 day in culture. Cholinergic receptor subtypes involved in cyclic GMP accumulation showed functional shifts similar to those in InsP3 formation. Binding experiments with a muscarinic ligand excluded the possibility that the reduction in muscarinic effects on InsP3 and cyclic GMP formation and intracellular Ca2+ mobilization were due to disappearance of the muscarinic receptor itself. These data show that cholinergic receptors linked to the accumulation of InsP3 and cyclic GMP and Ca2+ mobilization functionally shift from muscarinic to nicotinic during primary culture of adrenal chromaffin cells.

Adrenal Medulla↗
PubMed1988

Properties of cutaneous acetyltransferase catalyzing N- and O-acetylation of carcinogenic arylamines and N-hydroxyarylamine.

The role of skin for N- and O-acetylations of carcinogenic arylamine and N-hydroxyarylamine was studied in vitro. Unexpectedly high activities were observed in acetyl CoA-dependent N-acetylations of 2-aminofluorene (2-AF) and p-aminobenzoic acid (PABA) in skin cytosols of hamsters. The specific activity for 2-AF (4.52 nmoles/mg protein per min) was largely the same as that of rat liver cytosols. The cutaneous cytosols also catalyzed N,N-acetyltransfer reaction from N-hydroxy-4-acetylamino-biphenyl (N-OH-AABP) to 2-AF and acetyl CoA-dependent O-acetylation of 2-hydroxyamino-6-methyldipyrido[1,2-a:3',2'-d]imidazole (N-OH-Glu-P-1), suggesting that hamster skin cytosol has enzymes similar to hepatic acetyltransferases. In addition, remarkably high correlations were observed between the skin and liver in the activities for N-acetylations of PABA and 2-AF. In a colony of Syrian golden hamsters a clear polymorphism was detected in the cutaneous N-acetylations of PABA and 2-AF. These animals were divided into three groups according to their activities: rapid, intermediate and slow acetylators. On the other hand, the acetylating activities in the skin and liver of these three groups showed monomorphic distribution with N-OH-AABP-dependent N,N-acetyltransfer of 2-AF and acetyl CoA-dependent O-acetylation of N-OH-Glu-P-1. These results, together with the detection of N-acetylating activity in the skin of other experimental animals and humans, suggest that skin may play an important role in the metabolism of aromatic amines and that the cutaneous acetylation in hamsters may be under the common genetic control which regulates the individual difference in the hepatic activities.

Acetylation↗
PubMed1988

A case of Vibrio vulnificus infection.

Vibrio vulnificus, a recently described strain of the halophilic Vibrio species, was isolated from the blood of a 73-year-old man, who developed rapidly progressive wound infection and fatal septicemia. Twenty-one patients with Vibrio vulnificus infection have been reported in the Japanese literature. Vibrio vulnificus most frequently causes primary septicemia and necrotising cellulitis after the eating of raw fish or shellfish or after exposure to seawater. The infection is characterized by its occurring during the warm months of the year, in patients with underlying diseases, especially liver diseases, and the mortality rate is surprisingly high. Clinicians should therefore consider the possibility of Vibrio vulnificus infection in the differential diagnosis of severe wound infections. Early surgical intervention and intensive antibiotic therapy are recommended for preventing the progress of the septicemia.

Aged↗
PubMed1988

Electrophysiologic effects of desethylamiodarone, an active metabolite of amiodarone: comparison with amiodarone during chronic administration in rabbits.

During acute superfusion studies by means of the standard microelectrode technique, we previously showed that both amiodarone and its major metabolite, desethylamiodarone, had a modest effect on the lengthening of the action potential duration (APD) at high drug concentrations and produced a rate-dependent block of the sodium channel in cardiac muscle. In this study the comparative electrophysiologic effects of the two compounds in rabbits treated chronically with these compounds were determined with particular reference to repolarization and sinus node automaticity. The changes were correlated with those in serum and tissue drug levels and in thyroid hormone indices. After 1 week neither compound had a significant effect on atrial or sinus nodal potentials; after 3 weeks, amiodarone increased the atrial APD at 90% repolarization time by 10.5% (p less than 0.05) and the effective refractory period (ERP) by 6.7% (p less than 0.05). The corresponding figures for desethylamiodarone were 13% (NS) and 18% (NS). The sinus cycle length was increased 12% (NS) by amiodarone and 27.9% (p less than 0.05) after the metabolite. In animals treated for 6 weeks, amiodarone increased the ventricular APD at 90% repolarization by 58.8% (p less than 0.01) and desethylamiodarone by 42.0% the corresponding figures for the ERP were 63.4% (p less than 0.01 and 47.4% (p less than 0.01), respectively. At the stimulation frequency used, neither compound exerted a significant effect on Vmax. Both amiodarone and desethylamiodarone significantly decreased serum triiodothyronine and increased reverse triiodothyronine levels but had no effect on thyroxine.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1988

Electrophysiologic effects of a new antiarrhythmic agent, recainam, on isolated canine and rabbit myocardial fibers.

Recainam (Wy 42,362) is a new antiarrhythmic agent undergoing clinical evaluation, but its electrophysiologic effects in cardiac muscle are poorly defined. With microelectrode techniques, its profile in isolated preparations of dog and rabbit hearts was determined using drug concentrations of 10 to 300 microM. Recainam induced a concentration- and frequency-dependent decrease in the maximal rate of rise of the phase 0 of the action potential (Vmax), action potential amplitude and overshoot potential, with little or no change in the effective refractory period except in Purkinje fibers, in which it was markedly reduced. At a 300 microM concentration, Vmax was reduced 51% (p less than 0.001) in ventricular muscle and 44% (p less than 0.001) in atrial muscle, with no change in action potential duration or effective refractory period. At the same drug concentration in Purkinje fibers, Vmax was decreased by 41% (p less than 0.01), action potential duration at 90% repolarization by 36% (p less than 0.01) and effective refractory period by 34% (p less than 0.01). Recainam had no significant effect on the sinoatrial node, but it depressed phase 4 depolarization in isoproterenol-induced automaticity in Purkinje fibers. The drug had no effect on slow channel potentials induced by high concentrations of potassium and isoproterenol. The data indicate that the electrophysiologic profile of recainam in isolated cardiac muscle is consistent with the overall effects of class IC agents without having an effect on the slow calcium channel. Its major action is to depress Vmax, with little effect on refractoriness.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1988

Grayanotoxin opens Na channels from inside the squid axonal membrane.

External application of alpha-dihydro-grayanotoxin II (alpha-H2-GTX II) to squid giant axon under nonperfused condition caused substantial membrane depolarization. Intracellular perfusion of the fibers retarded this depolarization appreciably. Tritium-labeled alpha-dihydro-grayanotoxin II ([3H]alpha-H2-GTX II) in the external medium can permeate through the cell membrane, but permeation of alpha-H2-GTX II does not occur either with the carrier-mediated system or through the pores of the Na channel. The finding that the most hydrophilic grayanotoxin analogue, desacyl asebotoxin VII, is effective only when applied internally, strongly suggests that the receptor for grayanotoxin does not exist on the external surface of the membrane. The linear relationship between the concentration of [3H]alpha-H2-GTX II in the external medium and the count in the effluent from the perfused axon indicates that GTX II diffuses through the cell membrane's lipid phase and reaches the site of action only approached from the internal medium.

Aconitine↗
PubMed1988

Cellular electrophysiologic responses of isolated neonatal and adult cardiac fibers to d-sotalol.

The short-term cellular electrophysiologic actions of d-sotalol on isolated neonatal and adult canine ventricular myocardium and Purkinje fibers were evaluated using standard microelectrode techniques. d-Sotalol, 10(-6) to 10(-4)M, had no effects on action potential amplitude, maximal diastolic potential or action potential upstroke velocity (Vmax) in any neonatal or adult preparation. In five adult myocardial preparations, d-sotalol produced concentration-dependent increases in action potential duration at 50% (APD50) and 90% (APD90) repolarization and effective refractory period. In six neonatal myocardial preparations, d-sotalol produced a biphasic response; APD50, APD90 and effective refractory period decreased at 10(-6) and 10(-5)M. At 10(-4)M, these values increased significantly but to a lesser extent compared with values in adults. In seven adult Purkinje fibers, d-Sotalol significantly increased APD50, APD90 and effective refractory period in a concentration-dependent manner. All six neonatal Purkinje fibers responded in a biphasic manner, with values for APD50, APD90 and effective refractory period being less than control at 10(-6)M and near control values at 10(-5)M. At 10(-4)M, these variables were significantly increased, but to a lesser extent than in adult preparations. Our data confirm the typical class III effects of d-sotalol in adult cardiac tissues. The shortening of repolarization and refractoriness at lower drug concentrations in developing cardiac tissues may relate to age-dependent differences in cellular ionic function and basic electrophysiology.

Action Potentials↗
PubMed1988

Metabolic activation of a protein pyrolysate promutagen 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline by rat liver microsomes and purified cytochrome P-450.

The enzymatic activation of a promutagenic pyrolysate, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), was studied using the Ames mutagenesis test system. The enzyme catalyzing the mutagenic activation of MeIQx is mainly localized in the microsomal fraction. A large number of revertants was observed in the presence of hepatic microsomes obtained from 3-methylcholanthrene (3-MC)- or polychlorinated biphenyl (PCB)-treated rats but only a minimal number with the hepatic microsomes from untreated or phenobarbital (PB)-treated rats. In addition, the microsomal activation was reduced efficiently by known inhibitors of cytochrome P-450-mediated reactions such as 7,8-benzoflavone, ellipticine and flavone. Among five forms of purified rat cytochrome P-450, the highest sp. act. (no. of revertants induced/nmol cytochrome P-450) for the activation of MeIQx was observed with a high-spin form of cytochrome P-450, P-448-H, followed by the low-spin form, P-448-L, and to a lesser extent by PB-inducible forms, P-450b and P-450e. P-450-male, which is a main constitutive form of cytochrome P-450 in male rat livers, showed considerable catalysis for the mutagenic activation of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and MeIQx. These results indicate that the metabolic activation of MeIQx is catalyzed mainly by two forms of cytochrome P-450, P-448-H and P-488-L, in the livers of PCB- or 3-MC-treated rats, but also that P-450-male may play an important role in the activation in livers of intact male rats.

Animals↗