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Biomedical subjects

R Niki

Publications and source records attributed to R Niki.

At least 19 recordsLinked to original sources
PubMed2004

Effects of a synthetic progestogen, altrenogest, on oestrus synchronisation and fertility in miniature pigs.

Groups of six, six and eight miniature gilts, respectively, received 5, 10 or 15 mg/day of altrenogest for 18 days, and the numbers of corpora lutea and residual follicles were counted approximately 14 days after the treatment by an exploratory laparotomy. They were compared with the numbers in a control group of eight gilts which were examined six to eight days after oestrus. The interval between the last dose of altrenogest and the onset of oestrus increased with the dose of altrenogest, and was significantly longer after the treatments with 10 or 15 mg/day than after 5 mg/day (P < 0.01). Significantly more corpora lutea were observed in the gilts receiving 5 or 10 mg/day of altrenogest than in the control gilts (P < 0.1). Groups of six, seven and six miniature gilts that had respectively received 5, 10 or 15 mg/day of altrenogest were artificially inseminated; four, six and five of the gilts in these groups farrowed, and their mean (sd) litter sizes were 5.5 (2.4), 6.8 (1.2) and 5.0 (2.3), respectively. All six of a group of control gilts farrowed and their mean litter size was 5.8 (1.2).

Animals↗
PubMed2001

Production of transgenic miniature pigs by pronuclear microinjection.

Miniature pig is an attractive animal for a wide range of research fields, such as medicine and pharmacology, because of its small size, the possibility of breeding it under minimum environmental controls and the physiology that is potentially similar to that of human. Although transgenic technology is useful for the analysis of gene function and for the development of model animals for various diseases, there have not yet been any reports on producing transgenic miniature pig. This study is the first successful report concerning the production of transgenic miniature pig by pronuclear microinjection. The huntingtin gene cloned from miniature pig, which is a homologue of candidate gene for Huntington's disease, connected with rat neuron-specific enolase promoter region, was injected into a pronucleus of fertilized eggs with micromanipulator. The eggs were transferred into the oviduct of recipient miniature pigs, whose estrus cycles were previously synchronized with a progesterone analogue. A total of 402 injected eggs from 171 donors were transferred to 23 synchronized recipients. Sixteen of them maintained pregnancy and delivered 65 young, and one resulted in abortion. Five of the 68 offspring (three of which were aborted) were determined to have transgene by PCR and Southern analysis. The overall rate of transgenic production was 1.24% (transgenic/injected eggs). This study provides the first success and useful information regarding production of transgenic miniature pig for biomedical research.

Animals↗
PubMed2001

Acclimatization and response of minipigs toward humans.

As a first step toward making an efficient acclimatization methodology for minipigs, the reaction of Göttingen minipigs, 3-24 months of age, toward humans was investigated. All minipigs were kept in an individual cage, and the reaction toward humans (acclimatization index) was evaluated by simple observations. The acclimatization index was evaluated as the total number of points scored (0-30 points) based on the following criteria: (1) the position of the minipig when the cage door was opened; (2) the reaction of the minipig when the observer approached; and (31 the reaction of the minipig when the observer touched it. Subsequently, each animal was ranked by total points scored: 30 points = AA, 20 points < or = A < 30 points, 10 points < or = B < 20 points, 0 points < or = C < 10 points. Based on this evaluation, the reactions of minipigs under three conditions were investigated. The following findings were confirmed: first, minipig reaction to humans was influenced by monthly age; second, taming was possible under ordinary conditions of care, but we had to wait until 10 months of age on average for this to occur; third, if simple contact was made during care time, minipigs became tame within less than 4 weeks after the commencement of contact. We therefore consider it possible to artificially control the reaction of minipigs toward humans, and to make minipigs more available for experiments by adding control of the hereditary factors that influence this reaction.

Acclimatization↗
PubMed2000

Induction of superovulation and recovery of fertilized oocytes in prepubertal miniature pigs after treatment with PG600.

The purpose of this study was to examine whether superovulation can be induced by hormonal treatment with PG600 (400 IU eCG and 200 IU hCG) at the prepubertal stage in miniature pigs. In Experiment 1, 14 prepubertal miniature pigs received 1, 1/2 or 1/4 vial of PG600, im on Day 0 (the first day of treatment). Presentation of estrus was monitored thereafter. On Days 10 to 13 (i.e., 6 to 8 d after estrus), the number of corpora lutea (CL) and residual follicles was counted by an exploratory laparotomy. Injection of 1/2 vial of PG600 effectively induced estrus and ovulation in the pigs. In Experiment 2, 15 prepubertal miniature pigs that received 1/2 vial of PG600 were artificially inseminated into the uterus by an exploratory laparotomy at 100 to 104 h after PG600 injection. Oocytes were recovered from the oviducts at 121 to 145 h after PG600 administration. The oocyte recovery rate was 66% (15 oocytes/pig, average), and 84% of these were at the 1-cell stage. In Experiment 3, 5 prepubertal miniature pigs that received 1/2 vial of PG600, followed by 100 IU hCG 70 h later, were artificially inseminated into the uterus. Oocytes were recovered synchronously at 120 to 122 h after PG600 treatment. The recovery rate was 80% (17 oocytes/pig, average) and 90% of the oocytes recovered were at the 1-cell stage. These results suggest that superovulation of prepubertal miniature pigs can be induced by 1/2 vial of PG600 injection, and by the combined treatment with PG600 and hCG injection, the fertilized ova can be synchronously recovered at around 120 h after PG600 injection. This procedure may provide a useful system for biomedical research using the miniature pigs, especially for producing transgenic animals for use in human disease models.

Animals↗
PubMed1998

Isolation and identification of acetyl-CoA carboxylase inhibitors from green tea (Camellia sinensis).

An aqueous methanol extract from green tea showed potent acetyl-CoA carboxylase inhibitory activity. An active compound was isolated from the extract and identified as (-)-epigallocatechin gallate by instrumental analyses. The IC50 value of (-)-epigallocatechin gallate was 3.1 x 10(-4) M. Among tea catechins and related compounds, nearly equal activity was found in (-)-epigallocatechin gallate and (-)-epicatechin gallate, whereas (+)-catechin, (-)-epicatechin, (-)-epigallocatechin, gallic acid and methyl gallate each had no inhibitory activity. These results indicate that the 3-O-gallate group of the catechin structure was necessary for this activity. (-)-Epigallocatechin gallate inhibited triglyceride accumulation in 3T3-L1 cells at a concentration of 1.0 x 10(-7) M or higher.

Acetyl-CoA Carboxylase↗
PubMed1997

Isolation and identification of alpha-glucosidase inhibitors from tochu-cha (Eucommia ulmoides).

alpha-Glucosidase inhibitory activity was found in aqueous methanol extracts of tochu-cha, dried leaves of Eucommia ulmoides (Eucommiaceae). Five active principles against yeast enzyme were isolated and characterized. Among them, quercetin (1, Ki: 8.5 x 10(-6) M) was considered to contribute mostly to the activity of the tochu leaves. In regard to an animal alpha-glucosidase, rat intestinal sucrase activity was also inhibited by 1.

Animals↗
PubMed1996

Upregulation of apolipoprotein A-IV gene expression in residual ileum after massive small bowel resection requires the biliary secretion in rats.

Small bowel resection results in adaptation of residual intestine, but little is known about the postresectional response of apolipoproteins synthesized mainly in the small intestine. We have investigated the postresectional response of apolipoprotein A-1 and A-IV gene expression in residual ileum and assessed the mechanism of response, particularly the role of biliary secretion. Time course of changes in apolipoprotein A-1 and A-IV mRNA levels was examined by Northern blotting in the residual terminal ileum for 24 hr after 85% jejunoileal resection in fasted rats. Localization of these mRNAs was studied using in situ hybridization histochemistry. Effect of biliary diversion on the postresectional response of mRNAs and proteins was estimated by Northern blotting and immunoblotting, respectively. Apolipoprotein A-IV mRNA began increasing at 1 hr postresection, achieved a maximum by 12 hr (5-fold increase) and remained stable to 24 hr, while apolipoprotein A-1 mRNA did not change. Apolipoprotein A-IV mRNA accumulated predominantly in the upper part of ileal villi and increased its intensity postresection, and apolipoprotein A-1 mRNA was detected in the villus base to tip. The postresectional increase in apolipoprotein A-IV MRNA and protein was completely abolished by concurrent biliary diversion. The results suggest that the enterocytes in the ileal villi rapidly adapt to massive small bowel resection by increase in apolipoprotein A-IV gene expression which is mediated by biliary constituents but not luminal nutrients.

Animals↗
PubMed1995

Apolipoprotein mRNA in liver and intestine of rats is affected by dietary beet fiber or cholestyramine.

Rats were fed a cholesterol-free diet with no added fiber (fiber-free) or with 15 g/100 g beet fiber or 5 g/100 g cholestyramine for 14 d. Final plasma total cholesterol concentrations were significantly lower in rats fed beet fiber than in those fed fiber-free or cholestyramine diets. This difference was due mainly to lower HDL cholesterol concentrations. The group fed beet fiber also tended (P < 0.1) to have lower apolipoprotein A-I concentration in plasma. Northern blot analysis revealed that the relative concentrations of jejunal apolipoprotein A-I and A-IV mRNA were the same in all groups, whereas ileal apolipoprotein A-I and A-IV mRNA levels were significantly lower in rats fed beet fiber or cholestyramine than in those fed the fiber-free diet. Hepatic apolipoprotein E mRNA concentrations were the same in all groups, but apolipoprotein A-I mRNA levels were significantly lower in rats fed beet fiber than in those fed the other diets. Apolipoprotein A-IV mRNA tended (P < 0.1) to be lower in rats fed the beet fiber diet. These data suggest that the hypocholesterolemic effect of dietary beet fiber is associated with diminished expression of the hepatic apolipoprotein A-I gene.

Animals↗
PubMed1995

Adaptive response of apolipoprotein A-I and A-IV mRNA in residual ileum after massive small bowel resection in rats.

The response of apolipoproteins, which are synthesized mainly in the small intestine, after small bowel resection has not been documented. In this study, we investigated the effect of small bowel resection on the expression of apolipoprotein mRNA in the residual ileum in rats. Wistar rats underwent either an 85% jejunoileal resection or a sham-operation. Plasma concentrations of total and HDL-cholesterol, apolipoprotein A-I and A-IV were measured on days 0, 3, 6, 9, 12, and 16 (surgery on day 1). The abundances of apolipoprotein mRNA in the residual ileum and liver on day 16 were determined. Plasma levels of total and HDL-cholesterol and apolipoprotein A-I and A-IV in resected rats were significantly lower than in sham-operated rats on days 3 and 6. Resected rats showed a significant increase in ileal apolipoprotein A-I (1.2-fold) and A-IV (3.2-fold) mRNA compared with sham-operated animals. Hepatic apolipoprotein mRNA were the same between two groups. These data suggest that the residual ileum adapts to jejunoileal resection by selective increases in apolipoprotein A-I and A-IV expression at a pretranslational stage. The recoveries of apolipoprotein A-I and A-IV in plasma appear to depend, at least in part, on the increased expression of these apolipoproteins in the residual ileum.

Adaptation, Physiological↗
PubMed1994

Cholestyramine and a fat-free diet lower apolipoprotein A-IV mRNA in jejunum and cholestyramine lowers apolipoprotein A-I mRNA in ileum of rats.

To investigate the effect of bile acids or dietary lipid on the expression of intestinal apolipoproteins, the mRNA levels of apolipoprotein A-I and A-IV in the intestine from rats fed a diet containing cholestyramine or a fat-free diet were compared with those from rats fed a control diet containing 25% casein and 5% corn oil. Plasma total cholesterol concentration was lower after 16 h in rats fed a diet containing cholestyramine or a fat-free diet than in rats fed a control diet. In rats fed the fat-free diet, HDL cholesterol concentration also was lower than in those fed the control diet. The pool of bile acid in intestinal contents was significantly lower in rats fed cholestyramine than in both other groups. The relative abundance of jejunal apolipoprotein A-I mRNA did not differ between groups. Jejunal apolipoprotein A-IV mRNA abundance was significantly lower than in controls in rats fed the fat-free and cholestyramine-containing diets. Abundance of apolipoprotein A-I mRNA in ileal mucosa was comparable to controls in rats fed a fat-free diet but was significantly lower in rats fed cholestyramine. Ileal apolipoprotein A-IV mRNA tended to be lower in rats fed cholestyramine and a fat-free diet than in controls. We propose that decreased absorption of dietary lipid may modulate changes in jejunal apolipoprotein A-IV mRNA level and low levels of bile acids in the lumen may modulate changes in ileal apolipoprotein A-I mRNA level.

Administration, Oral↗
PubMed1994

An intracranial epidermal cyst in a Sprague-Dawley rat.

An intracranial epidermal cyst was found incidentally in a 10-week-old female Sprague-Dawley rat. The cyst was located in the leptomeninx of the longitudinal cerebral fissure, ventral to the corpus callosum and dorsal to the third ventricle. It was approximately 0.7 mm in diameter, lined by stratified squamous epithelium and filled with concentric layers of desquamated keratin. The wall consisted of 2-4 layers of cells. Ultrastructurally, the sequence of epidermal differentiation was not normal in that the basal cell layer and was absent in certain areas. The adjacent brain tissues were slightly compressed but not otherwise damaged by the cyst.

Animals↗
PubMed1994

Bile diversion lowers apolipoprotein A-I and A-IV mRNA levels in rat ileum.

We recently reported that cholestyramine (a bile acid sequestrant) lowered ileal apolipoprotein A-I mRNA level in rats. To obtain further information about this phenomenon, in this study, we investigated whether bile diversion lowers apolipoprotein A-I mRNA level in the ileum of rats. Bile-diverted rats were fed a diet with no added Na taurocholate (control diet) or with 0.4% Na taurocholate for 7 days. Sham-operated rats were also fed the control diet for the same period. Northern blot analysis revealed that the relative concentrations of jejunal apolipoprotein A-I and A-IV mRNA at the end of experimental period did not differ between groups while ileal apolipoprotein A-I and A-IV mRNA concentrations were significantly lower in bile-diverted rats fed the control and Na taurocholate-containing diets than in sham-operated rats. Plasma total and HDL cholesterol concentrations were the same in all groups. Relative concentration of apolipoprotein A-I in plasma also did not change. These results suggest that the bile plays an important role in ileal apolipoprotein gene expression at the pretranslational stage, but it is still unclear whether the effector is the bile acid or not. The unchanged concentration of plasma apolipoprotein A-I may have resulted from the constant secretion independent of synthesis in the intestine or the larger contribution from the liver which is another principal site for apolipoprotein A-I expression.

Animals↗
PubMed1994

Food deprivation increases apoptotic cell counts induced by 1,2-dimethylhydrazine in rat descending colonic and rectal crypts.

The frequency of apoptosis after treatment with 1,2-dimethylhydrazine (DMH) was counted in the descending colonic and rectal crypts of food-deprived and fed rats. Food-deprived or fed rats were subcutaneously injected with DMH (100 mg/kg body weight). Six hours after the injection, apoptotic cells were observed in crypt regions by light microscopy. The incidence of DMH-induced apoptosis in food-deprived rats was significantly higher than in fed rats. The incidence appeared to be higher in descending colon than in rectum. PAS staining revealed that DMH treatment lowered mucin secretion in crypts, which was substantially lowered by food deprivation. The effect of food deprivation on apoptosis induced by DMH may be due to the decrease in mucus barrier against DMH.

1,2-Dimethylhydrazine↗
PubMed1993

Cholestyramine and bile diversion lower the aminopeptidase activity in the intestinal brush border membrane of rats.

To examine the effect of bile acids on the activity of intestinal aminopeptidase in vivo, we measured the activity of aminopeptidase in the intestinal mucosa from rats fed the diet containing cholestyramine which sequesters luminal bile acids (experiment 1) and from bile diverted rats (experiment 2). After 32 h fasting, rats were refed for 16 h either of a standard diet (25% casein diets), the same diet containing cholestyramine, or the fat-free diet in experiment 1. In the intestinal washing, the content of total bile acids was markedly decreased with feeding cholestyramine and activities of trypsin and chymotrypsin were also lowered with cholestyramine. Cholestyramine feeding decreased the specific activity of aminopeptidase in the homogenate of intestinal mucosa but increased the specific activities of sucrase and alkaline phosphatase. All these parameters were not modified by the fat-free diet. In experiment 2, bile diverted and sham operated rats were refed the standard diet for 16 h with prior 32 h fasting. Bile diversion, like cholestyramine feeding, lowered the content of total bile acids, the activities of pancreatic hydrolases in the intestinal washings, and the specific activity of aminopeptidase in the intestinal mucosa. The specific activity of sucrase in the intestinal mucosa was higher in bile diverted rats but the activity of alkaline phosphatase was not changed. These data indicate that the decreased abundance of intraluminal bile acid affects the activity of intestinal aminopeptidase not through the decreased absorption of dietary lipid.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗
PubMed1990

[Nephrotoxicity of cefpirome sulfate in rabbits--single and multiple intravenous administration].

Nephrotoxic potential of cefpirome sulfate (CPR) was examined by single and multiple intravenous administrations to Japanese white male rabbits. In single administration studies, no nephrotoxic symptoms were observed at the dose level of 320 mg/kg of CPR or less. At the dose level of 500 mg/kg or more, nephrotoxic findings were noted in both CPR and cefazolin sodium(CEZ) groups, such as proteinuria, glucosuria, increase in serum level of urea nitrogen, creatinine and uric acid, and necrosis and calcification in the proximal tubular epithelium of kidney. Renal phenolsulfonphthalein(PSP) excretion was suppressed at the dose level of 500 mg/kg of CPR or more, and 2000 mg/kg of CEZ. In 14 and 21 days repeated administration studies, no nephrotoxic symptoms were observed at the dose level of 100 mg/kg of CPR and CEZ or less. At the dose level of 200 mg/kg of CPR or more, urinary and serum biochemical findings mentioned above were observed, and histopathological changes in the kidney described above were added in 400 mg/kg group. The similar nephrotoxic symptoms including histopathological changes of the kidney were observed in the groups of 100 mg/kg of cefaloridine(CER) and 200 mg/kg of CEZ. In addition, renal PSP excretion was suppressed in the group of 200 mg/kg of CEZ. The results would suggest that CPR is less nephrotoxic than CER and that the nephrotoxic potential of CPR is comparable to CEZ because CPR caused more severe renal failures in single administration study and less severe renal failures in multiple administration study than CEZ.

Animals↗
PubMed1988

Micellar structure of beta-casein observed by small-angle X-ray scattering.

The small-angle X-ray scattering was observed from beta-casein micelles in 0.2 M phosphate buffer (pH 6.7) with varying temperatures. An oblate ellipsoid of a rigid core with a thin soft layer was proposed as a probable model of the beta-casein micellar structure, according to the results of the model optimization with simple triaxial bodies. Here the axial ratio was found to decrease and the micelle to become spherical when the polymerization proceeds with temperature. The consistency of the present model was examined with the results of hydrodynamic measurements published previously.

Algorithms↗