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Biomedical subjects

K Okuda

Publications and source records attributed to K Okuda.

At least 667 records · Page 37Linked to original sources
PubMed1988

Effect of methotrexate on the deoxyuridine suppression test: results with different cell preparations.

Recently, the deoxyuridine suppression test was used to detect folate deficiency. Several cell preparations were used in this test, and the sensitivity of the test seems to vary with them. We used whole blood (micro-dU test) and bone marrow cells for the deoxyuridine suppression test, and the effects of methotrexate were compared. [3H]Thymidine incorporation into DNA was highest when the concentration of methotrexate was 1 microM in the whole blood culture and bone marrow culture. Methotrexate concentrations from 100 nM to 1 mM did not affect the results of the micro-dU test. However, the bone marrow deoxyuridine test became abnormal with methotrexate, and the abnormality in test values was corrected by the addition of N5-formyltetrahydrofolate. Differences in the results between the micro-dU test and the bone marrow deoxyuridine suppression test seem to represent specificity of each dU test.

Bone Marrow↗
PubMed1988

Experimental portal fibrosis produced by intraportal injection of killed nonpathogenic Escherichia coli in rabbits.

An attempt was made to develop an animal model for the study of the etiology of noncirrhotic portal fibrosis or idiopathic portal hypertension based on the assumption that it is related to chronic abdominal infection. Rabbits were given killed nonpathogenic Escherichia coli intraportally or intravenously. The animals to which a mixture of killed E. coli and rabbit antiserum (aggregated E. coli) was given intraportally developed remarkable histologic changes in the liver. The early inflammatory reactions in the portal area and parenchyma were followed by rapid disappearance of inflammation and development of portal fibrosis with bile duct proliferation. Three intraportal challenges with aggregated E. coli were sufficient to produce pronounced portal fibrosis, although there was considerable variation in response among individual animals. This procedure also produced splenomegaly, and in some animals marked portal hypertension. Injection of nonaggregated killed E. coli into the portal vein or aggregated E. coli into the ear vein also caused similar hepatic changes, but they were milder in degree. These histologic changes resemble portal fibrosis seen in idiopathic portal hypertension and, less closely, pericholangitis associated with inflammatory bowel disease in humans.

Animals↗
PubMed1988

Portal hemodynamics in patients with gastric varices. A study in 230 patients with esophageal and/or gastric varices using portal vein catheterization.

The hemodynamic features of gastric varices are not well documented. The purpose of this study was to investigate the nature of hepatofugal collateral veins, their origins, the direction of blood flow in the major veins and collateral veins, and portal venous pressure. To this end, 230 patients, mostly cirrhotic, who had esophageal or gastric varices, or both, demonstrated by endoscopy were investigated by portal vein catheterization. The findings were correlated with endoscopically assessed degrees of varices. Gastric varices were seen in 57% of the patients with varices due to portal hypertension. In most of the patients with advanced gastric varices, esophageal varices were minimal or absent. When patients with gastric varices were compared with those having predominantly esophageal varices, it was found that advanced gastric varices were more frequently supplied by the short and posterior gastric veins, they were almost always associated with large gastrorenal shunts, and portal venous pressure in patients with large gastric varices was lower. Chronic portal systemic encephalopathy was more common in patients with large gastric varices due to hepatofugal flow of superior mesenteric venous blood in the splenic vein than in patients with predominantly esophageal varices. Thus, the hemodynamics in patients with large gastric varices are distinctly different from those in patients with mainly esophageal varices, and such differences seem to account for the differing incidence of chronic encephalopathy and variceal bleeding.

Adult↗
PubMed1988

Inhibitory effects of prostaglandin E1 on T-cell mediated cytotoxicity against isolated mouse liver cells.

The effects of prostaglandin E1 on cell-mediated cytotoxicity against hepatocytes were investigated using an in vitro cytotoxic assay system. Isolated liver cells from normal C57BL/6 mice were used as the target cells, and effector cells were obtained from spleens of C57BL/6 mice in which experimental hepatitis had been induced by immunization with syngeneic liver antigens. In this assay system, spleen T cells adhering to nylon wool demonstrated a high cytotoxic activity against target liver cells. The cytotoxicity was markedly reduced by prostaglandin E1 at concentrations greater than 10(-7) M. Maximum suppressive activity was obtained when prostaglandin E1 was continuously present during the assay period. By contrast, indomethacin, a specific inhibitor of prostaglandin synthesis, enhanced the cytotoxic activity of effector cells. These data seem to indicate that exogenously added prostaglandin E1 has an inhibitory effect on cell-mediated cytotoxicity of effector spleen cells against target hepatocytes.

Alprostadil↗
PubMed1988

Effects of gonadotropin releasing hormone and prostaglandin F(2)alpha on the reproductive performance in postpartum cows.

A study was conducted to determine whether treatment with gonadotropin releasing hormone (GnRH) in combination with prostaglandin F(2)alpha (PGF(2)alpha) could enhance ovarian activity and uterine involution in postpartum dairy cows to reduce the calving interval. Cows were randomly assigned to one of three treatment groups. Cows (n = 8) in Group 1 received 100 mug GnRH intramuscularly (i.m.) twice on Day 20 and Day 35 postpartum, and 25 mg PGF(2)alpha i.m. on Day 47 postpartum. Group 2 (n = 8) received a single i.m. injection of 100 mug GnRH on Day 25 postpartum and 25 mg PGF(2)alpha i.m. on Day 37 postpartum. The Control Group (n = 9) did not receive hormonal treatment. Palpation per rectum of the reproductive organs and serum progesterone (P) determination were performed twice a week to monitor ovarian activity and uterine involution. Postpartum interval to the first ovulation was short in treated groups (Group 1, 21.0 d; Group 2, 26.3 d) compared with Control Group (30.1 d, P < 0.05). Likewise, mean frequency of ovulation was increased in both treated groups compared with the Control Group (P < 0.05). Cows in treated groups required fewer days to complete uterine involution than in the Control Group. The mean interval to the first service, the conception rate at first service and the number of services per conception showed no significant differences among the three groups, but the mean days from calving to conception were shorter for the treated groups (78.7 d in Group 1; 83.3 d in Group 2) than (109.1 d, P < 0.05) for the Control Group. Our results suggest that combined treatment with GnRH and PGF(2)alpha may enhance ovarian activity in the postpartum cow, resulting in improved reproductive performance.

Journal Article↗
PubMed1988

Effects of fluocinolone acetonide on mouse skin sterol metabolism and two-stage carcinogenesis.

Fluocinolone acetonide (FA) is one of the most potent synthetic glucocorticoids and is known to possess an anti-tumor promoting activity. An attempt was made to evaluate this activity by estimating tumor promoting activity. Unexpectedly, when 10 micrograms of FA was applied alone or after a single application of a subcarcinogenic dose of 3-methylcholanthrene to mouse skin, results suggested that FA itself may be a tumor promoter or a complete carcinogen. Other glucocorticoids tested, e.g. dexamethasone, hydrocortisone and prednisolone, also revealed similar effects but were less potent than FA. To verify the possibility that glucocorticoid is a complete carcinogen or a tumor promoter, a tumor incidence experiment was performed for 24 weeks. As a result it was found that FA possesses a tumor promoting activity at some dose levels but no tumor initiating activity.

Animals↗
PubMed1988

Immunochemical evidence for the catalysis of vitamin D3 25-hydroxylation and testosterone 16 alpha-hydroxylation by homologous forms of cytochrome P-450 in rat liver microsomes.

Polyclonal antibody elicited in a rabbit against purified cytochrome P-450cc25, which catalyzes 25-hydroxylation of vitamin D3, inhibited not only 25-hydroxylation of cholecalciferol and 1 alpha-hydroxycholecalciferol, but also 16 alpha- and 2 alpha-hydroxylation of testosterone catalyzed by the purified P-450cc25 preparation. Antibody inhibition experiments with microsomes revealed that most 16 alpha- and 2 alpha-hydroxylation of testosterone and most 25-hydroxylation of cholecalciferol by male rat liver microsomes were catalyzed by P-450cc25. In order to examine the identity of cholecalciferol 25-hydroxylase and testosterone 16 alpha-hydroxylase, monoclonal antibodies recognizing three different epitopes of P-450cc25 were prepared from hybridoma clones produced by fusion of mouse myeloma cells (P3X63Ag8U1) with the spleen cells of immunized BALB/c mouse. All of these monoclonal antibodies inhibited both 25-hydroxylation of 1 alpha-hydroxycholecalciferol and 16 alpha-hydroxylation of testosterone by purified P-450cc25. These observations suggested that immunochemically indistinguishable form(s) of cytochrome P-450 catalyzed both reactions.

Animals↗
PubMed1988

Expression of a rat liver microsomal cytochrome P-450 catalyzing testosterone 16 alpha-hydroxylation in Saccharomyces cerevisiae: vitamin D3 25-hydroxylase and testosterone 16 alpha-hydroxylase are distinct forms of cytochrome P-450.

Rat cytochrome P-450(M-1) cDNA was expressed in Saccharomyces cerevisiae TD1 cells by using a yeast-Escherichia coli shuttle vector consisting of P-450(M-1) cDNA, yeast alcohol dehydrogenase promoter and yeast cytochrome c terminator. The yeast cells synthesized up to 2 X 10(5) molecules of P-450(M-1) per cell. The microsomal fraction prepared from the transformed cells contained 0.1 nmol of cytochrome P-450 per mg of protein. The expressed cytochrome P-450 catalyzed 16 alpha- and 2 alpha-hydroxylations of testosterone in accordance with the catalytic activity of P-450(M-1), but did not hydroxylate vitamin D3 or 1 alpha-hydroxycholecalciferol at the 25 position. The expressed cytochrome P-450 also catalyzed the oxidation of several drugs and did not show 25-hydroxylation activity toward 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha-triol. However, it cross-reacted with the polyclonal and monoclonal antibodies elicited against purified P-450cc25 which catalyzed the 25-hydroxylation of vitamin D3. These results indicated that P-450(M-1) cDNA coded the 2 alpha- and 16 alpha-hydroxylase of testosterone, and that these two positions of testosterone are hydroxylated by a single form of cytochrome P-450. Vitamin D3 25-hydroxylase and testosterone 16 alpha- and 2 alpha-hydroxylase are different gene products, although these two hydroxylase activities are immunochemically indistinguishable.

Animals↗
PubMed1988

Sex-related difference in vitamin D3 25-hydroxylase of rat liver microsomes.

Cholecalciferol 25-hydroxylase was partially purified by polyethylene glycol fractionation and chromatographies on octylamino-Sepharose and hydroxylapatite columns starting from the liver microsomes of female rats, and compared with P-450cc25 purified from the liver microsomes of male rats (Hayashi, et al. (1986) J. Biochem. 99, 1753-1763). On octylamino-Sepharose 4B column chromatography, most of the activity was recovered in the fraction eluted with 0.08% Emulgen 913 in the case of the male enzyme, whereas the female enzyme was recovered in the fraction eluted with 0.2% Emulgen. Anti-cc25 antibodies against purified male P-450cc25 inhibited the 25-hydroxylation activity of male polyethylene glycol (PEG) fraction and partially purified male enzyme, but did not inhibit the activities of the corresponding female fractions. The antibodies formed a single precipitation line with male P-450cc25, but did not form a precipitation line with partially purified female 25-hydroxylase on immuno-diffusion. These observations indicated that the vitamin D3 25-hydroxylase in female rat liver microsomes is a different entity from that of male rats.

Animals↗
PubMed1988

Adherence of streptococci to surface-modified glass.

Four types of surface-modified glass were prepared. Aminopropyl glass was prepared by alkylsilylation of glass slides with gamma-aminopropyltriethoxysilane. This glass carries primary amino groups which may be protonated at pH 7.2. Owing to the presence of both positively charged ions and hydrophobic ethoxyl groups, the glass is considered to be amphipathic. Three other types of surface-modified glass slides were prepared from aminopropyl glass by forming Schiff's bases with three aldehydes: glucose, glyoxylic acid and hexanal. The aldehyde-treated slides were subsequently reduced using sodium borohydride. Thus, the surface of the glass was rendered hydrophilic, ampholytic or hydrophobic, respectively. The adherence of two Streptococcus sanguis strains and two Streptococcus mutans strains to the surface-modified glass slides was studied. Different strains showed differences in adherence to these slides depending on their physico-chemical surface properties. For S. sanguis ATCC 10556, hydrophobic bonds seemed to be most important, while in S. mutans OMZ 176, ionic interactions made the highest contribution to adhesion. Hydrogen bonds seemed to contribute least to adherence.

Bacterial Adhesion↗
PubMed1988

Suppressor T cells in mice made unresponsive to skin allografts.

We have induced suppressor T cells (Ts), capable of delaying allogeneic skin graft rejection, through the intravenous administration of allogeneic spleen cells under normal conditions. H-2 and non-H-2 incompatibility between recipient mice and donor skins induced strong graft rejection. However, when the Ts were transferred into recipient mice, the mean survival time was prolonged for every combination between recipient mice and donor skin. Studies using several strains of congenic mice revealed the antigen specificity of these Ts. Treatment with monoclonal anti-Lyt-2.2 or anti-Thy-1.2 antibody and complement abolished the suppression shown by the Ts of skin graft rejection. The suppression induced by these Ts, however, was resistant to treatment with monoclonal anti-Lyt-1.2, anti-L3T4, or anti-I-A antibody and complement. These results showed that the Ts were Lyt-1-2+, L3T4-, Ia-, T cells.

Animals↗
PubMed1988

Histological changes in the liver and portal hypertension subsequent to repeated intraportal injections of killed E. coli in the dog.

The etiology of idiopathic portal hypertension (IPH) is not known. To obtain clues to the pathogenesis, an attempt was made to produce a hepatic lesion similar to that in IPH by repeated injections of aggregated killed non-pathogenic E. coli directly into the portal vein. In the treated dogs, histology of the liver showed dense fibrosis in the portal tract and an aberrant vasculature around the portal area after 1 month. Portal pressure was elevated and middle-to-small-sized portal branches were decreased in number as studied by portography. These changes closely mimic those seen in human IPH. The possibility is discussed that chronic entrance of an antigen such as bacteria from the intestine to the portal venous system plays an etiologic role in IPH.

Animals↗
PubMed1988

Light and electron microscopic study of the liver in paraquat poisoning.

Intrahepatic cholestasis in paraquat poisoning in man has been thought to be secondary to extensive bile duct injuries, though its exact mechanism remains unsettled. We have examined liver biopsy specimens from two cases of paraquat poisoning. Case 1 (fatal) presented severe intrahepatic jaundice, and liver biopsy showed centrilobular cholestasis with extensive bile duct loss. Ultrastructurally, dilatation of bile canaliculi with decrease of microvilli and thickening of pericanalicular ectoplasm was found in the hepatocytes. Case 2 (alive) showed mild liver dysfunction without jaundice. While liver biopsy showed nonspecific reactive changes with intact bile ducts and ductules, electron microscopy disclosed dilatation of bile canaliculi with decrease of microvilli and thickening of pericanalicular ectoplasm in the hepatocytes, suggesting that damage to the bile secretory apparatus in the hepatocytes develops irrespective of extensive bile duct loss. These findings suggest that bile secretory apparatus in the hepatocytes as well as biliary epithelial cells could be a target of paraquat or its metabolites.

Adult↗