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Biomedical subjects

K Kamata

Publications and source records attributed to K Kamata.

At least 217 records · Page 12Linked to original sources
PubMed1988

Structural characterization of recombinant human interferon-gammas derived from two different mammalian cells.

Recombinant human interferon-gammas (rHuIFN-gamma s) were obtained from two different mammalian cells (mouse C127 cells and Chinese hamster ovary, CHO, cells) cultured in a microcarrier culture system. Both rHuIFN-gamma s were purified using sequential chromatographies for their comparison of structural properties. The peptide maps of HuIFN-gamma s digested with V8 protease and Western blot analysis demonstrated that C127 cells yielded mainly about 25kDa component and CHO cells produced about 25kDa and about 20kDa components. By the identification of glycosylated peptides, it was suggested that 20kDa and 25kDa components are glycosylated at one and at two sites, respectively. C-terminal amino acid sequence analysis indicated that both rHuIFN-gamma s consisted of at least six different species lacking 2 to 16 amino acid residues from C-terminus, so that C-termini of both rHuIFN-gamma s were slightly different from each other. Amino acid sequence and composition analyses of N-terminal peptides demonstrated that N-termini of both rHuIFN-gamma s were blocked and were supposed to be identical with that of natural HuIFN-gamma. These results suggested that different molecular heterogeneities of rHuIFN-gamma s resulted from the difference of post-translational modifications of host cells.

Amino Acid Sequence↗
PubMed1988

Treatment of depression with clonazepam.

The antidepressive effect of an anticonvulsant clonazepam was studied with maximum daily dose of 1.5 to 6.0 mg (mean 3.4 mg) in 27 patients with major depression (n = 18) or bipolar disorder (n = 9). Two of them dropped out at an early stage of the treatment, and the antidepressive effect of clonazepam was evaluated for the remaining 25 patients. A marked to moderate improvement was obtained for 21 patients (84%), and the onset of the antidepressive effect of clonazepam appeared within 1 week in most of the cases who responded to the therapy. The total scores on the Hamilton Depression Rating Scale and the Beck Self-Rating Scale were significantly reduced after the clonazepam treatment. Side effects occurred in 14 patients, but most of them were not severe. From these results, it is thought that clonazepam might be useful as an antidepressant for patients in whom conventional antidepressant treatment are contraindicated.

Adult↗
PubMed1988

Virulence-associated genetic regions comprising 31 kilobases of the 230-kilobase plasmid in Shigella flexneri 2a.

By random transposon Tn5 insertions, we previously identified six virulence-associated SalI fragments, B, D, F, G, H, and P, in the 230-kilobase plasmid pMYSH6000 of Shigella flexneri 2a. In this study, we analyzed the sites of 134 independent Tn5 insertions on four contiguous SalI fragments, B, P, H, and D, of pMYSH6000 and identified five virulence-associated regions; four were associated with inducing a positive Sereny test (Ser), invasion into epithelial cells (Inv), binding to Congo red (Pcr), and inhibition of bacterial growth (Igr), and one was associated with the Ser and Inv but not with the Pcr or Igr phenotypes. Hybridization studies revealed that these virulence-associated DNA regions were highly conserved among 15 other virulence plasmids of four species of Shigella and enteroinvasive Escherichia coli. These data indicate that at least seven separate genetic determinants on the virulence plasmid are required for full expression of the virulence phenotype of shigellae.

DNA Restriction Enzymes↗
PubMed1988

Constitutive long-term production and characterization of recombinant human interferon-gammas from two different mammalian cells.

Two expression plasmids (pSVIFN gamma/BPV97 and pSVIFN gamma/AdDHFR) for constitutive production of human interferon-gamma (HuIFN-gamma) were constructed and introduced into the two different mammalian cell lines, mouse C127 cells and Chinese hamster ovary (CHO) cells. Genetically engineered C127 and CHO cells grew on microcarriers having high productivity of HuIFN-gammas for at least six months. Isoelectric focusing patterns and molecular weight analyses suggest that C127- and CHO-HuIFN-gammas are glycoproteins and that both HuIFN-gammas have different molecular structures. The development of a microcarrier culture system for genetically engineered mammalian cells has enabled us to prepare glycosylated HuIFN-gammas on a large scale.

Animals↗
PubMed1988

The effects of intracerebroventricular administration of adrenergic agonists and antagonists on adrenaline secretion from the adrenal medulla in stressed conscious rats.

The effects of intracerebroventricular (i.c.v.) administration of adrenergic agonists and antagonists on the increase in serum adrenaline (Ad) induced by immobilization stress were examined in unanesthetized, unrestrained rats. The serum Ad of rats showed a significant linear increase as time elapsed after the induction of immobilization stress. This immobilization stress-induced increase was inhibited by the i.c.v. administration of a small amount of noradrenaline (NA) and phenylephrine. Isoproterenol and clonidine failed to inhibit the immobilization stress-induced increase. The inhibition of the immobilization stress-induced increase by i.c.v. administration of NA was antagonized by pretreatment with phentolamine and prazosin, but not by pretreatment with yohimbine and propranolol. These results suggested that NA administered via an i.c.v. route may inhibit the stress-induced increase in adrenomedullary Ad secretion by an action on the central alpha 1-adrenoceptor.

Adrenal Medulla↗
PubMed1988

Mechanisms of increased responses of the aorta to alpha-adrenoceptor agonists in streptozotocin-induced diabetic rats.

To investigate the influence of diabetes on the responsiveness of the cardiovascular system, we have examined the effects of various agents on the reactivity of the vascular smooth muscle of aortic strips obtained from age-matched control and diabetic rats. Norepinephrine (NE) contracted the aortic strips obtained from age-matched control and diabetic rats in a concentration-dependent manner, but maximal contraction of aortic strips in response to NE was enhanced in diabetic rats. The EC50 value for NE in the diabetic aortic strips was similar to that in the aorta from age-matched controls. Ca-induced contracture of the aortic strips which were depolarized with isotonic K+ (60 mM) was potentiated in aortic strips from diabetic rats, when compared with those from age-matched controls. Ca-induced contracture of aortic strips, preincubated with 10(-6) M NE and 10(-6) M nicardipine in Ca2+-free Krebs-Henseleit solution (KHS), was not significantly different in age-matched control and diabetic rats. Bay K 8644, an activator of calcium channels, produced an increase in the force of contraction of the slightly depolarized aorta from diabetic rats. Phasic contraction induced by phenylephrine (PE) in the presence of 10(-6) M nicardipine in Ca2+-free KHS was significantly enhanced in aortic strips obtained from diabetic rats. These results demonstrate that NE-induced contraction of the aortic strips obtained from diabetic rats was significantly enhanced, and that this increased contractile response of the aorta to NE may be due to an increased influx of extracellular calcium through the voltage-dependent Ca2+ channels, but not through the receptor-operated Ca2+ channels.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1988

Effect of intracerebroventricular administration of opioid peptides on basal serum adrenaline levels in conscious rats.

It is considered that adrenomedullary secretion of adrenaline is centrally regulated by various endogenous substances. Recently, opioid peptides have been reported as one of this group of endogenous substances. However, the receptor through which these endogenous opioid peptides regulate adrenomedullary adrenaline secretion has not been elucidated. In the present study, various opioid peptides were administered intracerebroventricularly in conscious, unrestrained rats, and blood catecholamine levels were measured at various periods to determine which cerebral opioid peptide receptor is involved in the mechanism of basal adrenomedullary adrenaline secretion. The results indicate that delta-receptor stimulation has a positive effect on basal adrenomedullary adrenaline secretion, while mu- and kappa-receptors are not involved in this mechanism.

Adrenal Medulla↗
PubMed1988

Changes in sensitivity of the rat stomach fundus to various drugs in streptozotocin-induced diabetic rats.

The changes in sensitivity of the rat stomach fundus to acetylcholine (ACh), norepinephrine (NE), isoproterenol (ISO) and to vasoactive intestinal peptide (VIP) were examined in control rats and in streptozotocin (STZ)-induced diabetic rats. The dose-response curves for drugs were constructed 8 weeks after treatment with STZ. The dose-response curve for ACh in diabetic rats was shifted to the left as compared to the control curve, whereas the dose-response curves for NE, ISO and VIP were shifted to the right. These results suggest that functional changes in the autonomic nervous systems of the rat stomach fundus may occur in STZ-induced diabetic rats.

Acetylcholine↗
PubMed1988

Molecular genetic approaches to the pathogenesis of bacillary dysentery.

Bacillary dysentery is an invasive infectious disease of the human colon. At least three genetic loci on the chromosome and a huge plasmid have been implicated in its pathogenesis. Results obtained from molecular genetic studies, mainly of the genes, virG, virF and kcpA are discussed.

Animals↗
PubMed1987

Atrophy of the striatum and motor disturbance induced by colchicine.

To determine the functional role of the striatonigral system in the circling behavior of rats and the mode of action of colchicine, we investigated the circling behavior induced by dopamine agonists after microinjection of colchicine into the unilateral striatum. Both apomorphine and methamphetamine produced ipsilateral circling behaviors in rats injected with colchicine, indicating that ipsilateral striatonigral pathways were damaged by the drug. Histological and biochemical examinations showed that intracaudate injection of colchicine damaged not only the dopaminergic neurons but also caused atrophy of the striatum with loss of neuronal perikarya. These results suggest that treatment with colchicine may be used as a model of senile atrophy or degenerative atrophy in these animals.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1987

Influence of acidosis on inotropic effect of catecholamines in newborn rabbit hearts.

The influence of acidosis on the inotropic effect of isoproterenol was studied in the isolated arterially perfused heart of the newborn rabbits. Baseline mechanical function during acidosis (pH 6.8) was not different from control (pH 7.4). However, the inotropic effect of isoproterenol was significantly suppressed in the acidotic muscles. The increment of myocardial adenosine 3',5'-cyclic monophosphate (cAMP) content during isoproterenol infusion was also reduced in acidosis. Inotropic effects of Ca and dibutyryl cAMP in the acidotic muscles were not significantly different from those in the control muscles. beta-Receptor number and affinity in the respiratory acidotic muscle was similar to those in the control muscle. Effects of pH on myocardial beta-receptor and adenylate cyclase activity were further determined in the membrane fraction by changing the pH of the reaction medium from 7.4 (control) to 6.8 or 6.0. beta-Receptor numbers were significantly decreased at pH 6.0 but not at pH 6.8. Adenylate cyclase activity was depressed at pH 6.8 and 6.0. These data suggest that the inotropic effect of isoproterenol is diminished in the acidotic muscle. This may be due to the decreased activation of cAMP production, which in turn most likely results from depressed adenylate cyclase activity.

Acidosis↗
PubMed1987

Development of myocardial contractile system in the fetal rabbit.

Developmental changes in the myocardial contractile system were evaluated in the fetus at 18, 21, and 28 days of gestation (full term 31 days) and in 3- to 5-day-old newborn rabbits. Mechanical function was studied using the isolated arterially perfused heart. Perfusion with ryanodine (10(-5) M), an inhibitor of Ca release from the sarcoplasmic reticulum, decreased contractile force and increased the time to peak tension in the 28-day fetus and newborn but these changes were minimal in the 18- and 21-day fetus. Postextrasystolic potentiation, which is thought to be caused by Ca release from the sarcoplasmic reticulum, was observed in the 28-day fetus and the newborn, but was not significant in the 18- and 21-day fetus. An ultrastructural study showed poorly developed sarcoplasmic reticulum and myofibrils in the 18- and 21-day fetus. Although the maximum developed tension observed at high extracellular calcium increased with development, the relative value of developed tension at various extracellular calcium was similar in the three fetal groups and only in the newborn the extracellular calcium-developed tension curve shifted to the right. Myofibrillar yield increased with development but sensitivity of myofibrillar ATPase activity to Ca was similar in the fetus and newborn. These data suggest that 1) the sarcoplasmic reticulum does not function significantly in the 18- and 21-day fetus, 2) although sarcoplasmic reticulum starts to function at late gestation, it does not cause significant changes in intracellular calcium in the fetal period, 3) myocardial contractility remains similar in the fetus from the 18th to 28th day of gestation and major changes in contractility occur after birth.

Animals↗
PubMed1987

Effect of milrinone on myocardial mechanical function and cyclic AMP content in the fetal rabbit.

The effect of milrinone on mechanical function was studied in the isolated arterially perfused heart of the fetal (28th day of gestation) and newborn rabbits. The inotropic effect of milrinone in the fetus was significantly less than in the newborn. After milrinone infusion, myocardial cyclic AMP levels increased significantly in the two age groups and the fetal values before and after milrinone infusion were not significantly different from the newborn values. In our previous study the inotropic effects of dibutyryl cyclic AMP and high extracellular calcium in the fetus were significantly less than in the newborn. These data suggest that the diminished inotropic effect of milrinone in the fetus may be due, at least in part, to the decreased inotropism of cyclic AMP and calcium.

1-Methyl-3-isobutylxanthine↗
PubMed1987

Pharmacological studies on the interrelation between the dopaminergic, GABAergic and opioid peptidergic systems in the central nervous system of the rat.

To elucidate the functional connections between dopaminergic, GABAergic and opioid peptidergic systems in rats, electrophysiological, behavioral, neurochemical and histological investigations have been undertaken, focusing on the changes in drug sensitivity in the central nervous system (CNS). Changes in sensitivity in the CNS can be induced by denervation, chronic administration of antagonists or agonists, and by the inhibition of the axoplasmic transport system. It is conceivable that the changes in sensitivity of the CNS to transmitters may be related to the etiology of mental illnesses such as schizophrenia and mania and may be related to the symptoms of Parkinson's disease. Investigation of changes in sensitivity of the CNS to transmitters or drugs may provide the key for elucidating the biological nature of mental illness.

Animals↗