Search PubMed⌕ Search

Biomedical subjects

H Oka

Publications and source records attributed to H Oka.

At least 469 records · Page 26Linked to original sources
PubMed1984

Improvement of chemical analysis of antibiotics. VII. Comparison of analytical methods for determination of impurities in tetracycline pharmaceutical preparations.

In order to examine the suitability of our four established methods for the analysis of tetracyclines (high-performance liquid chromatography, reversed-phase thin-layer chromatographic densitometry, reversed-phase thin-layer chromatographic spray reagents and silica gel high-performance thin-layer chromatographic densitometry) for the determination of impurities in tetracycline pharmaceutical preparations, sixteen samples available on the Japanese market were analysed. Because these methods did not always give satisfactory results, their analytical conditions were modified. The comparative studies indicated these methods were accurate and reliable. Therefore, we recommend a combination of these methods for the analysis of impurities, in which the spray reagents are used first as a screening method, and then if the results exceed the limits, a precise determination is carried out using either high-performance liquid chromatography or reversed-phase thin-layer chromatographic densitometry.

Anti-Bacterial Agents↗
PubMed1984

Nigral inputs to the pedunculopontine region: intracellular analysis.

Intracellular recordings were made from neurons of the pedunculo-pontine region (PPR), the midbrain-pontine tegmentum around the brachium conjunctivum, in pentobarbital-anesthetized cats. Stimulation of the substantia nigra (SN) induced inhibitory postsynaptic potentials (IPSPs) in PPR neurons at a short latency (mean 2.17 ms, S.D. 0.66, n = 34) with a considerably long duration (mean 65.3 ms, S.D. 22.6). These neurons were distributed not only in the pedunculopontine tegmental nucleus (27 cells), but also in the cuneiform nucleus (5 cells) and the parabrachial nucleus (2 cells). Out of 34 cells, only two cells showed convergent synaptic inputs from SN and the cerebellar nuclei. Thus, it is concluded that PPR neurons receive mainly the inhibitory inputs from SN, one of the outputs of basal ganglia, and are infrequently influenced by the cerebellar outflow.

Animals↗
PubMed1984

Improvement of chemical analysis of antibiotics. V. A simple method for the analysis of tetracyclines using reversed-phase high-performance liquid chromatography.

An isocratic high-performance liquid chromatographic method for the determination of tetracyclines is described using a mobile phase containing oxalic acid and C8- and C18-modified silica gel columns. For good separations of tetracyclines, oxalic acid concentrations of above 0.01 and 0.2 M respectively for parent tetracyclines (group I) and impurities in tetracycline (group II) are required. The optimum pH of the aqueous oxalic acids solution in the mobile phase is 2.0. The combinations of the C8-modified silica gel column with methanol-acetonitrile-0.01 M aqueous oxalic acid solution pH 2.0 (1:1.5:5) and the C18-modified silica gel column with methanol-acetonitrile-0.2 M aqueous oxalic acid solution pH 2.0(1:1:3.5) gave satisfactory results for groups I and II, respectively.

Acetonitriles↗
PubMed1984

Effects of the ratio of exogenous eicosapentaenoic acid to arachidonic acid on platelet aggregation and serotonin release.

We added arachidonic acid (AA) and eicosapentaenoic acid (EPA) to washed platelet suspensions in the absence of albumin, holding the total amount of the fatty acids constant at 2 microM, and changing the ratio of EPA to AA. Platelet aggregation, serotonin release and the amount of thromboxane (TX) B2, a cyclooxygenase product synthesized from exogenous AA, decreased as the ratio was increased. The decreases were greater than the expected ones from the diminution of the amount of exogenous AA. On the other hand, 12-hydroxyeicosatetraenoic acid (HETE), a lipoxygenase product synthesized from exogenous AA, increased in the presence of EPA. Although EPA was reported to be a poor substrate for platelet cyclooxygenase, the amount of TXB3 synthesized from exogenous EPA increased markedly by the simultaneous addition of AA. These results suggest that the EPA/AA ratio-dependent decrease in platelet aggregation and serotonin release is caused at least by both the decrease in the absolute amount of AA and the inhibitory effect of EPA on AA-metabolism via the cyclooxygenase pathway. Further studies on effects of EPA-metabolites via the cyclooxygenase pathway on platelet responses will be needed.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1984

Effect of an intracellular calcium antagonist (TMB-8) on carbamylcholine-induced amylase release from dispersed rat pancreatic acini.

During 10-min incubation with increasing concentrations of carbamylcholine (carbachol), amylase release from dispersed rat pancreatic acini increased, became maximal at 2 X 10(-6)M and then decreased. In the concentration range of 10(-7)M to 10(-4)M, 8-(N,N-diethylamino)-octyl 3,4,5-trimethoxybenzoate hydrochloride (TMB-8) caused a dose-dependent inhibition of amylase release induced by a submaximal concentration of carbachol. No inhibitory effect was observed on basal and secretin-stimulated amylase release. TMB-8 showed a significantly greater ability of blocking the action of carbachol than verapamil and diltiazem. TMB-8 could reverse the submaximal stimulation of amylase release caused by supramaximal concentrations of carbachol to a maximal stimulation, while verapamil and diltiazem could not. These results confirm the hypothesis that mobilization of intracellular calcium is the primary step in the action of carbachol on pancreatin acinar cells and contributes to the submaximal secretory response of acinar cells induced by high concentrations of carbachol.

Amylases↗
PubMed1984

Experimental evaluation of the resistance of the skin grafted rectum to ileal contents.

There are three general approaches to prevent the development of cancer in patients with premalignant colorectal diseases. One method requires total colectomy and excision of the rectal mucous membrane. For 35 years, patients have had their rectal muscle tube covered by a variety of full-thickness ileal pullthrough operations. For 30 years, various types of pelvic ileal pouches have been tried in attempts to improve bowel function. This report attempts to evaluate another approach in experimental animals. The rectal submucosa was skin grafted and subsequently anastomosed to the ileum to assess its ability to stand up to that milieu. The results were promising with a maximum follow-up of 1 year. This may prove to be another option to ileoanastomy with or without a pouch.

Anal Canal↗
PubMed1984

Sugar specificity of the receptor of rat thymocytes in rosette formation with guinea pig erythrocytes.

Most rat thymocytes form rosettes with guinea pig erythrocytes only in the presence of nonheated fetal calf serum. The sugar specificity of the receptors of rat thymocytes were studied using the sugar inhibition test with various monosaccharides and glycoproteins, exoglycosidases treatment on rat thymocytes, and adsorption of fetal calf serum with lectins and sugar gels. The following observations were made; L-fucose and D-mannose completely inhibited rosette formation, whereas addition of D-galactose had no inhibitory effect on rosette formation. The rosette-forming ability of thymocytes was reduced by mannosidase treatment, but fucosidase treatment did not show any inhibitory effect on rosette formation. These results suggest that mannose residue on the surface of thymocytes participated in the rosette formation.

Animals↗
PubMed1984

Identification of vasopressin and determination of its corticomedullary levels in rat kidney tissue.

To investigate the kidney tissue level of arginine vasopressin (AVP), tissue AVP was extracted, identified and assayed. Rat kidney tissue was separated into the papilla (P), medulla (M), and cortex (C). After homogenization, AVP was extracted with acetone and determined by radioimmunoassay. Fractionation of the tissue extract by Sephadex G25 column chromatography showed that the peak of immunoreactive AVP was identical to that of synthetic AVP. There was good correlation between bioassayable and immunoassayable AVP for the tissue extracts. Tissue AVP concentrations (pg/g wet weight) after 36 hr of dehydration were: P, 164.3 +/- 13.0; M, 93.8 +/- 8.4; and C, 28.9 +/- 3.9 with a plasma AVP (pg/ml) of 11.7 +/- 1.0 (mean +/- SE, N = 18). Thus, the papilla/plasma AVP concentration ratio was high. When 125I-AVP was administered, the papilla/plasma ratio was very low. Under water diuresis, the tissue AVP level was very low. The kidney tissue level of dDAVP, which was administered exogenously, was much higher than that of AVP when compared at similar plasma levels. Thus, the present study demonstrated the existence of a corticomedullary concentration gradient of AVP with a medullary level much higher than the plasma level. The accumulation of AVP seemed to result from receptor-mediated processes, since 125I-AVP, which is biologically inactive and does not bind to hormone receptors, showed only a slight accumulation. The higher tissue level of dDAVP suggested that the tissue level was determined by the balance between accumulation and inactivation, since dDAVP is known to be scarcely inactivated in the kidney.

Animals↗
PubMed1984

Analysis of apolipoproteins in high density lipoproteins by high performance liquid chromatography.

A simple and rapid method for the analysis of apolipoproteins in high density lipoprotein (HDL) by high performance liquid chromatography (HPLC) has been developed (Kinoshita et al. (1983) J. Biochem. 94, 615-617). With this method, using a sodium phosphate buffer containing 0.1% sodium dodecyl sulfate (SDS) as an eluent, apolipoproteins can be analyzed from a very small amount of HDL fraction without delipidation using organic solvents. Separation profiles of apolipoproteins by this method were examined using several techniques. The elution pattern monitored by A280 can give precise quantitative as well as qualitative information about size-distribution of apolipoproteins, except for the apo C group. Moreover, separation of apo E from apo A-I was found to be improved by column elongation.

Apolipoproteins↗
PubMed1984

Reconstruction of pulmonary artery with substitute valve--with special reference to size of conduit and valve.

Operative risk factors and postoperative late results were evaluated in 26 patients undergoing pulmonary artery reconstruction with a substitute valve. Seventeen extracardiac conduits bearing a valve were used in 16 patients and an in situ pulmonary valve insertion was carried out in the other 10. The surgical results were influenced by complexity of the underlying cardiac lesions and pulmonary vascular status, with a high mortality rate in patients with several cardiac defects including single ventricle, asplenia syndrome, complete atrioventricular canal etc. The mortality rate was 6% in patients with an immediate post-repair Ppv/sv of less than 0.75 and 77.8% in those with a Ppv/sv over 0.75. Postoperative Ppv/sv was mainly regulated by valve area index and a close correlation was obtained for the regression equation Ppv/sv = 0.41/(VAI)2 + 0.36 (r = -0.61, p less than 0.05). To obtain excellent hemodynamics with a Ppv/sv of less than 0.50, valve area index should be over 1.7 cm2/M2, and to eliminate re-implantation of the conduit after reaching adulthood, the diameter of the conduit should be 18 mm or more and the valve size 23 A, or more when a SJM valve is used.

Adolescent↗
PubMed1984

A case of chronic pancreatitis successfully treated by endoscopic removal of protein plugs.

A 56 years old male with chronic pancreatitis complained of intractable abdominal pain, anorexia, emaciation and peripheral edema. Medical treatment initiated only partial improvement in the general condition and hypoproteinemia. Endoscopic retrograde cholangiopancreatography revealed multiple filling defects in the dilated main pancreatic duct. Endoscopic aspiration of pure pancreatic juice yielded numerous protein plugs. The endoscopic removal of protein plugs from the pancreatic duct resulted in remarkable improvement in symptoms, laboratory findings and ERCP findings. We consider this procedure to be an important new treatment of chronic pancreatitis.

Cholangiopancreatography, Endoscopic Retrograde↗
PubMed1984

A new antitumor antibiotic, kazusamycin.

A new antibiotic kazusamycin, was isolated from the culture broth of Streptomyces sp. No. 81-484, which shows antitumor activity against experimental murine tumors. This antibiotic did not possess antibacterial activity against Gram-positive and Gram-negative bacteria, but showed strong cytotoxic activity against HeLa cells in vitro. The chemical and physico-chemical properties of kazusamycin suggest that the molecular formula of this antibiotic is C33H48O7 (MW 556).

Animals↗