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Y Oki

Publications and source records attributed to Y Oki.

At least 127 records · Page 7Linked to original sources
PubMed1987

Purification and characterization of aquacobalamin reductase (NADPH) from Euglena gracilis.

Euglena aquacobalamin reductase (NADPH: EC 1.6.99.-) was purified, and its subcellular distribution was studied to elucidate the mechanism of the conversion of hydroxocobalamin to 5'-deoxyadenosylcobalamin. The enzyme was found in the mitochondria. It was purified about 150-fold over the Euglena mitochondrial extract in a yield of 38%. The purified enzyme was homogeneous in polyacrylamide gel electrophoresis. Spectra of the purified enzyme showed that it was a flavoprotein. The molecular weight of the enzyme was calculated to be 66,000 by Sephadex G-100 gel filtration and 65,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme was specific to NADPH with an apparent Km of 43 microM and to hydroxocobalamin with an apparent Km of 55 microM. The enzyme did not require FAD or FMN as a cofactor. The optimum pH and temperature were 7.0 and 40 degrees C, respectively.

Animals↗
PubMed1987

[Biological and hematochemical characteristics of herbivorous common voles (Microtus arvalis Pallas)].

In 1979, some pairs of voles (Microtus arvalis Pallas) were introduced to our laboratory from Hungary. Thereafter, they were successfully bred and increased in number, as experimental small animals for herbivorous domestic animals. They have been raised in a room and fed with pelleted feed for herbivores and chopped hay-cubes. We can change the high-fiber-containing rations from the chopped hay-cube to the alfalfa pellet that is widely available in laboratories. Regarding the breeding characteristics of the voles, the average litter size was 5.44 +/- 1.64, and the age at the first birth was 55.4 +/- 10.7 days. Some voles with white coats were found during the breeding process in our laboratory. Hematochemical characteristics of the voles were determined and the following characteristics were noted. Red blood cell counts of the voles were higher than those of other experimental animals (rat, mouse). White blood cell counts of the voles were lower than those of the other animals. The electrophoretic patterns of serum protein differed markedly from those of other experimental animals. The gamma-globulin concentrations of the voles were very low, and A/G ratios were high. Blood glucose concentrations of the voles were lower than those of the other mono-gastric experimental animals. Activities of serum enzymes (GOT, GPT, ALP) were higher than those of other experimental animals (rat, mouse, cow).

Animal Feed↗
PubMed1985

Effects of water deprivation and administration of hypertonic saline on dopamine concentrations in posterior pituitary and vasopressin release in rats.

Changes in concentrations of arginine vasopressin (AVP) in plasma and the neurointermediate lobe of the pituitary and those in dopamine (DA) in the neurointermediate lobe in rats were studied simultaneously after depriving the animals of water as well as after giving intraperitoneal (i.p.) injections of hypertonic saline (4.5% saline, 25 ml/kg of body weight). After water deprivation for 24 h, both AVP in plasma and DA in the neurointermediate lobe increased without any changes in AVP in the neurointermediate lobe. Water deprivation for 48-72 h caused further increases in both AVP in plasma and DA in the neurointermediate lobe with a significant decrease in AVP in the neurointermediate lobe. Rehydration for 24 h subsequent to 72 h of water deprivation made AVP in plasma and DA in the neurointermediate lobe return to the values of normally hydrated rats, whereas AVP in the neurointermediate lobe was still depressed. Thirty min after the i.p. injection of hypertonic saline, both AVP in plasma and DA in the neurointermediate lobe increased markedly with no change in AVP in the neurointermediate lobe. The time course of change in DA in the neurointermediate lobe was similar to that in plasma AVP when plasma osmolality was changed chronically or acutely. These results may make questionable the preconception that the tuberohypophyseal DA neurons are not involved in or regulated by early changes in vasopressin secretion.

Animals↗
PubMed1984

[A sensitive and specific radioimmunoassay for arginine vasopressin and its validation].

A sensitive and specific radioimmunoassay (RIA) for arginine vasopressin (AVP) has been developed and validated. Synthetic AVP was coupled to bovine serum albumin (BSA) with glutaraldehyde. Antisera against AVP were raised in three rabbits immunized with AVP-BSA complex. After 6 months, at the 16th injection, one of the antisera had a titer high enough to be utilizable for RIA at a final dilution of 1:400,000. The labeling of AVP with 125I Na was performed with the modified chloramine T method, and the purification of iodinated AVP was done with gel filtration chromatography on a Sephadex G-25 fine column (1 X 20 cm) with an elution buffer of 0.01 M acetic acid containing 0.1% BSA. Radioactivities from the Sephadex G-25 were eluted in three peaks. 125I-AVP, which was reactive to the antiserum, was contained in the third peak, and 125I-AVP in the fractions on the down slope of the peak was used for the radioligand in the amount of 1000 cpm. The specific activity of purified 125I-AVP was about 400 muCi/microgram. Diluted antiserum and samples, unlabeled AVP or related peptides were preincubated at 4 degrees C for 24 hr, and then 125I-AVP was added to the mixture and incubated for a further 72 hr. Separation of B and F was done with polyethyleneglycol. The minimal detection limit of AVP, which was 95% of the confidence limit of the mean value of B0, was 0.4 pg/tube. The cross-reactivities with lysine vasopressin, arginine vasotocin, DDAVP and oxytocin were 0.1%, 30%, 1% and 0%, respectively. AVP in plasma was extracted with cold acetone and petroleum ether. The recoveries of synthetic AVP from plasma which was added (2-16 pg) were more than 94%. The intra and inter-assay coefficients of variation determined by plasma of AVP concentration of about 4.8 pg/ml were 8.7% and 11.3%, respectively. The RIA detected AVP of concentration as low as 1 pg/ml following the extraction procedure. AVP immunoreactivity was detected without extraction in urine, and the lyophilized cerebrospinal fluid and acid extract of tissues of the central nervous system, and the reactivities in these samples were demonstrated to be immunologically identical to that of synthetic AVP when diluted serially. The changes of plasma and urinary AVP concentration on water intake, water deprivation and smoking in humans were clearly demonstrated.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

Microtus species as new herbivorous laboratory animals: reproduction; bacterial flora and fermentation in the digestive tracts; and nutritional physiology.

In a study of the possible introduction of Japanese field vole (Microtus montebelli ) and Hungarian voles (M. arvalis) as herbivorous experimental animals, the following biological characteristics were investigated: breeding and reproductive performance; bacterial flora and fermentation in the digestive tracts; and nutritional physiology. The animals are polyestrus , show postpartum estrus on the day of parturition, and there is little or no delay in implantation due to lactation, especially in M. arvalis. On examination of vaginal smears, Japanese field vole did not show any definite pattern, whereas most Hungarian voles showed 6- to 18- day cycles. From the esophageal sac of voles fed rations with a high fiber content, cellulolytic bacteria similar to Ruminococcus albus, Ruminococcus flavefaciens , and Bacteroides succinogenes were isolated. More than 1 000 000/g anaerobic bacteria were present in the esophageal sac and the pattern and the types of bacteria resembled those found in the rumen. Gastric fermentation took place in the esophageal sac. The pH and total VFAs were much smaller in the fundic and pyloric regions of the stomach than in the esophageal sac. Acetic and lactic acids were the major fermentation products in the esophageal sac. Following deficiency or lowering of the cellulose decomposing abilities, a decrease of VFAs and an increase in lactic acid production in the esophageal sac were observed. These effects resulted in high glucose, FFA and ketone bodies in the blood, and a higher incidence of glucosuria. Diabetes induced by administrations of drugs such as alloxan, streptozotocin and phloridzin were compared using Microtus and mice. Microtus had low sensitivity to alloxan but high sensitivity to streptozotocin. The influence of monensin on Microtus was also investigated by using diets containing 20 and 80 mg/kg monensin. Diets containing 80 mg/kg monensin led to 50 % mortality in 7 weeks and growth was hindered. Gas production from the esophageal sac contents of voles in the monensin-medicated group was much smaller than that of the non-medicated group. In the monensin group the total VFA concentrations of the esophageal sac contents was decreased.

Animal Nutritional Physiological Phenomena↗
PubMed1983

[Induction of dietetic diabetes in Microtus arvalis Pallas and its developmental mechanism].

In Microtus arvalis Pallas, new born voles were fostered to ICR mice and supplied with pellets for mice after weaning. A high concentration of glycosuria was shown in about 50% of the voles and continued for over ten weeks. Concentrations of blood glucose and plasma FFA iun glycosuric voles were three or four times as high as those in normal controls. The fermentation ability and pH lowered in the esophageal sac, and comparatively large amount of starch existed in the pyloric stomach of the glycosuric voles. This demonstrated that the dietary starch were tolerably transported to the pyloric stomach without being fermented in the esophageal sac. Glycosuria was also induced in about 50% of the voles supplied with an acidified water (0.02 N HCl, pH 1.7), and the glycosuric voles showed a low pH (1.4-4.2) and lowering of the fermentative ability in esophageal sac. Such an abnormal fermented conditions in the esophageal sac is considered to induce glycosuria in the voles. Glucose tolerance in the diabetic voles which were supplied with pellets for mice lowered considerably with the progress of the disease. On the other hand, plasma insulin levels in the slight diabetic cases rose to eight times as high as normal level, but they lowered considerably with the progress. In the serious cases, the voles fell into complete insulin deficiency. From the above results, the herbivorous Microtus species was considered to be useful as an "animal model" of the dietetic diabetes.

Animals↗