Biomedical subjects

N Isobe

Publications and source records attributed to N Isobe.

At least 37 records · Page 2Linked to original sources

PubMed2001

Effect of the factor inhibiting germinal vesicle breakdown on the disruption of gap junctions and cumulus expansion of pig cumulus-oocyte complexes cultured in vitro.

The present study was undertaken to explore the regulatory mechanisms for meiotic resumption of pig cumulus-oocyte complexes (COCs) by assessing the nuclear status of oocytes, the degree of gap junction cell-to-cell communication and cumulus expansion after culture of various numbers of COCs in 10 microl droplets of medium for 24 h. Gap junction communication was examined by confocal laser scanning microscopy after injection of a fluorescent dye, lucifer yellow, into the oocytes. When one, three or six COCs were cultured in a 10 microl droplet, germinal vesicle breakdown was observed in > 70% of oocytes; increasing the number of COCs in a droplet further actually decreased the proportion of oocytes undergoing germinal vesicle breakdown (10 COCs: 49%; 20 COCs: 21%; 40 COCs: 13%). When six COCs were cultured in a 10 microl droplet of conditioned medium (prepared previously by culturing 20 intact and oocytectomized COCs for 24 h), the proportion of oocytes undergoing germinal vesicle breakdown was significantly reduced compared with the proportion in fresh medium. An increase in the proportion of category 1 COCs (all gap junctions within cumulus cells and between cumulus cells and oocyte are functionally maintained) was achieved by increasing the number of COCs cultured in a 10 microl droplet. The addition of conditioned medium to the fresh medium at a concentration of 50% significantly inhibited cumulus expansion. From these results, it is concluded that the factors secreted by cumulus cells regulate the disruption of gap junctions and cumulus expansion, and concurrently control the incidence of germinal vesicle breakdown in pig COCs.

Animals↗

PubMed2001

An in situ hybridization study of the effects of artificial insemination on the localization of cells expressing MHC class II mRNA in the chicken oviduct.

The aim of this study was to determine the effects of artificial insemination on the localization of antigen-presenting cells expressing MHC class II mRNA in chicken oviducts. Laying hens (35 weeks old) were inseminated with fresh semen or sham-inseminated with saline daily for 3 days. In situ hybridization was performed to detect chicken MHC class II (B-LB21 major gene) mRNA on frozen sections of oviductal infundibulum, uterovaginal junction and vagina by using digoxigenin-labelled PCR probes. Cells expressing MHC class II were observed mainly in the oviductal mucosal stroma and occasionally in the mucosal epithelium. After 24 h, the population of cells expressing MHC class II in the infundibulum was significantly higher in laying hens inseminated with fresh semen than in the control hens sham-inseminated with saline (P < 0.05). However, there was no significant difference in the population of cells expressing MHC class II in the uterovaginal junction and vagina between the artificially inseminated and control hens. These results indicate that anti-sperm immune responses, including the influx of cells expressing MHC class II and enhanced MHC class II mRNA expression, probably occur in the infundibulum after artificial insemination.

Animals↗

PubMed2000

Immunocytochemical study of cell proliferation in the cystic ovarian follicles in cows.

We examined the frequency of proliferating cells in cystic, atretic and healthy antral follicles to determine whether a disorder of cell proliferation was responsible for the occurrence of bovine cystic follicles. Paraffin sections of healthy follicles and various stages of atretic and cystic follicles were immunostained with mouse monoclonal antibody to proliferating cell nuclear antigen (PCNA). The PCNA-positive cells were counted in 4 different regions of a follicle from the apical to the basal side. In the granulosa layer, a significantly higher frequency of PCNA-positive cells was observed in the healthy follicle in the basal region as compared with the apical region. A similar pattern of PCNA-positive cells population was observed in the granulosa layer of atretic follicles, although the frequency in the basal region was significantly lower in the atretic than the healthy follicle. The rate of cell proliferation in the granulosa layer of cystic follicles was markedly lower at the basal region than that of atretic follicles. In the theca interna, the frequency of PCNA-positive cells in atretic follicles at the early stages was higher than that in cystic follicles at the early stages. These results suggest that in the healthy follicle the proliferative activity of granulosa cells is higher in the basal than the apical region, and that the cell proliferation activity in the granulosa and theca interna may decrease in association with the induction of a follicular cyst.

Animals↗

PubMed2000

Spleen-derived dendritic cells engineered to enhance interleukin-12 production elicit therapeutic antitumor immune responses.

The major goal in cancer immunotherapy is the induction of tumor-specific T lymphocytes capable of killing tumor cells. As both dendritic cells (DCs) and interleukin-12 (IL-12) can play immunostimulatory roles in vivo, the use of a combination of these has become a promising approach. In the present study, we used a murine tumor model to examine whether spleen-derived DCs transduced with the IL-12 gene could elicit tumor-specific immune responses. BALB/c mice injected peritumorally with adenovirus-mediated IL-12 gene-transduced antigen-unpulsed DCs inhibited the growth of day 5-established subcutaneous CT26 tumors. Splenocytes from treated mice responded specifically to parental tumor cells and showed increased production of interferon gamma (IFN-gamma) and antitumor cytotoxic T-lymphocyte (CTL) activity. Increased numbers of both CD4(+) and CD8(+) T cells were detected in the treated tumors. The inhibition of tumor growth was significantly greater in mice injected with IL-12 gene-transduced DCs than in those injected with IL-12 gene-transduced fibroblasts or the IL-12 gene-encoding adenovirus itself. Taken together, these results indicate that DCs transduced with the IL-12 gene by a recombinant adenovirus are effective in inducing tumor-specific Th1 and CTL responses that inhibit the growth of established subcutaneous tumors.

Adenocarcinoma↗

PubMed2000

Localization of apoptotic cells in the cystic ovarian follicles of cows: a DNA-end labeling histochemical study.

We examined the frequency of apoptosis in cystic follicular cells to investigate the cause of the delay in regression of cystic follicles. Paraffin sections of healthy antral follicles, early and late atretic ones, and early and late cystic ones were stained using the terminal deoxynucleotidyl transferase (Tdt)-mediated biotinylated deoxyuridine triphosphates (dUTP) nick end-labeling (TUNEL) method to detect apoptotic cells. In the granulosa layer of early cystic and atretic follicles, TUNEL-positive cells were evident. In the theca interna of both early and late atresia, high frequencies of TUNEL-positive cells were observed. In the theca interna, a high frequency of TUNEL-positive cells was noted in the early cystic follicles, whereas their frequency decreased in late cystic follicles. These results suggest that apoptosis occurs in the granulosa and theca interna cells of cystic as well as atretic follicles, but the frequency of apoptosis in theca interna cells decreases in late cystic follicles, which may be responsible for the delay of follicular regression.

Animals↗

PubMed2000

Does repeated balloon inflation during coronary angioplasty induce ischemic tolerance? Analysis based on regional work.

It has been reported that repeated brief balloon inflation during coronary angioplasty (PTCA) alleviates myocardial dysfunction. However, it has also been reported that PTCA does not induce ischemic tolerance. Six patients with stable angina pectoris were recruited for this study. They were scheduled for PTCA to a significant stenosis of the proximal left anterior descending artery (LAD). All patients had single-vessel coronary artery disease without angiographic evidence of collateral circulation and with normal wall motion. After the stenosis of LAD was dilated by a 30-s inflation, 60 s of balloon inflation was performed five times at 60-s intervals. Left ventricular regional work was determined in the first and fifth inflations, and the data were compared. Regional work of the interventricular septum decreased immediately after the balloon inflation (the first inflation: 5.3 +/- 1.0 --> 0.6 +/- 0.2 mJ/cm3; fifth inflation; 5.3 +/- 1.0 --> 0.6 +/- 0.3 mJ/cm3) and no statistically significant differences were found between the first and fifth inflations. After balloon deflation, the time required for the recovery of regional work was 30s in the fifth inflation, compared with 40 s in the first inflation (at 30 s after deflation, first inflation: 3.6 +/- 1.3 mJ/cm3; fifth inflation: 5.2 +/- 1.2 mJ/cm3). Although repeated balloon inflation did not change the amount of reduction in regional work, it improved the postischemic recovery of regional work. These results suggest ischemic tolerance.

Aged↗

PubMed2000

Metabolism of furametpyr. 1. Identification of metabolites and in vitro biotransformation in rats and humans.

Urinary and fecal metabolites in male rats treated with a (14)C-labeled fungicide, furametpyr [N-(1,3-dihydro-1,1, 3-trimethylisobenzofuran-4-yl)-5-chloro-1, 3-dimethylpyrazole-4-carboxamide, Limber], were purified by a combination of chromatographic techniques, and chemical structures of 14 metabolites were identified by spectroanalyses (NMR and MS). The major biotransformation reactions of furametpyr in rats were found to be (1) N-demethylation, (2) oxidation of the methyl group at C3 of the pyrazole ring, (3) oxidation of the methyl group at C1 of the 1,3-dihydroisobenzofuran ring, (4) hydroxylation at C3 of the 1,3-dihydroisobenzofuran ring, and (5) hydroxylation at C7 of the 1, 3-dihydroisobenzofuran ring. In vitro metabolism by recombinant human cytochrome P450 revealed that a major biotransformation in humans is N-demethylation, catalyzed by CYP1A1, 1A2, 2C19, and 3A4.

Animals↗

PubMed2000

Metabolism of furametpyr. 2. (14)C excretion, (14)C concentrations in tissues, and amounts of metabolites in rats.

14C-Labeled furametpyr [N-(1,3-dihydro-1,1, 3-trimethylisobenzofuran-4-yl)-5-chloro-1, 3-dimethylpyrazole-4-carboxamide, Limber] was dosed to male and female rats at 1 (low dose) and 200 or 300 mg/kg (high dose). Elimination of furametpyr was rapid, and the dosed (14)C was substantially excreted within 7 days (45.5-53.3% in feces, 44.1-53. 8% in urine, and 0.01% in expired air). However, (14)C excretion rate showed sex- and dose-related differences, more rapid in males at low dose. (14)C concentrations in tissues decreased rapidly to generally low levels at 7 days (<0.004 ppm with the low dose and <1. 1 ppm with the high dose). Forty metabolites were detected, and 13 metabolites and 4 glucuronides were identified. A small amount of unchanged furametpyr was detected in feces (0.1-0.5% of the dose). The major metabolites in tissues were N-demethylated metabolites. In a bile study, 52.5-54.2% of the dosed (14)C was rapidly excreted into bile within 2 days. The absorption ratio was estimated to be >93.7% for the low dose (1 mg/kg). Major metabolites in bile were glucuronic acid conjugates of furametpyr hydroxides. On the basis of the results, furametpyr is substantially absorbed from the gastrointestinal tract after oral administration, rapidly distributed to tissues, extensively metabolized, and excreted into urine and bile or feces.

Animals↗

PubMed2000

Metabolism of Cyanox in rat. II. Sex-related differences in oxidative dearylation and desulphuration.

1. To examine the metabolites of Cyanox (O-4-cyanophenyl O,O-dimethyl phosphorothioate, cyanophos, CYAP) in brain, liver, blood cells and plasma during the early toxic period, the male and female rat was administered a single oral dose of [phenyl-14C]Cyanox at dose levels of 50 mg/kg and killed 5, 10 and 20 min thereafter. 2. Sex-related differences in the concentrations of metabolites were observed. Cyanoxon, produced by oxidative desulphuration, was observed in the brains of both sexes at all time points, but the concentrations were 2-6 times higher in the male. The same metabolite was detected in the liver, blood cells and plasma of the male but not the female. The total concentrations of oxidative dearylation metabolites (4-cyanophenol + 4-cyanophenylsulphate + glucuronide of 4-cyanophenol) in plasma, blood cell, brain and liver were larger in the male at all time points than those in the female, whereas the reverse was the case for demethylated metabolites (desmethylcyanox + desmethylcyanoxon) in all tissues except for the brain. 3. Studies of the in vitro metabolism of Cyanox revealed no sex-related difference for hepatic cytosolic fractions in terms of the major in vitro metabolic reaction, demethylation. On the other hand, the major reactions in microsomal fractions, oxidative desulphuration and oxidative dearylation, were significantly (2-3 times) greater in the male than in the female. 4. Oxidative desulphuration and oxidative dearylation, involving cytochrome P450 enzymes, were inhibited by male-specific rat CYP2C11 antiserum. The degree of inhibition was more pronounced in the male case. Thus, the results strongly suggest that the 2C family of cytochrome P450 (male, CYP2C11 and CYP2C13; female, CYP2C12) contributes to oxidative desulphuration and dearylation of cyanox in the rat and that the activity of male-specific CYP2C11 (and CYP2C13) is greater than that of female-specific CYP2C12. The consequent greater formation of cyanoxon in the male is consistent with the higher toxicity in this sex.

Administration, Oral↗

PubMed2000

Lack of significant estrogenic or antiestrogenic activity of pyrethroid insecticides in three in vitro assays based on classic estrogen receptor alpha-mediated mechanisms.

Estrogenic and antiestrogenic activity of pyrethroid insecticides (d-trans-allethrin, cypermethrin, empenthrin, fenvalerate, imiprothrin, permethrin, d-phenothrin and prallethrin) was evaluated using a suite of three in vitro assays based on classic human estrogen receptor alpha (hER alpha)-mediated mechanisms. A mammalian cell-based luciferase reporter gene assay was developed for examining effects on hER alpha-mediated gene activation. hER alpha-independent effects on the gene activation were examined using control cells with constitutive luciferase activation by a herpes simplex virus thymidine kinase (HSV-TK) promoter for determining appropriate dose levels of test chemicals. Moreover, the test chemical-dependent interaction between hER alpha and a coactivator (transcriptional intermediary factor 2: TIF2) was analyzed by a yeast two-hybrid method, competitive binding to hER alpha being assayed by a fluorescence polarization method. Significant (p < 0.05) positive effects of estrogenic substances (E2/estradiol, diethylstilbestrol, and p-nonylphenol) were detected in all assays. An antiestrogen, 4-hydroxytamoxifen, significantly inhibited E2-mediated transactivation and interaction between hER alpha and TIF2 through hER alpha binding (p < 0.05). However, none of the pyrethroids tested showed significant (p < 0.05) estrogenic or antiestrogenic effects (100 nM-10 microM), indicating that they do not impact on the classic hER alpha-mediated activation pathway in vitro.

Binding, Competitive↗

PubMed2000

Detecting viable hibernating myocardium in chronic coronary artery disease--a comparison of resting 201Tl single photon emission computed tomography (SPECT), 99mTc-methoxy-isobutyl isonitrile SPECT after nitrate administration, and 201Tl SPECT after 201Tl-glucose-insulin infusion.

To identify and quantify the amount of viable hibernating myocardium in patients with chronic coronary artery disease, resting 201Tl single photon emission computed tomography (SPECT) was compared with 99mTc-methoxy-isobutyl isonitrile (MIBI) SPECT after nitrate infusion (nitrate-99mTc-MIBI) and 201Tl SPECT after 201Tl with glucose-insulin-potassium infusion (201Tl-GIK) in 25 patients. Twenty-one patients also underwent completely left ventriculography beforehand and 5+/-4 months afterwards. SPECT images were divided into 9 segments and scored visually from 0 (normal uptake) to 3 (absent). The defect score was calculated as the summation of the total scores (TDS) in each patient. The TDS of nitrate-99mTc-MIBI images (6.3+/-4.3) and 201Tl-GIK images (5.8+/-4.2) were significantly lower than the 7.4+/-4.3 of resting 201Tl images (p<0.01). Based on the improvement of wall motion after coronary revascularization, the sensitivity of 201Tl-GIK imaging (85%) was significantly higher (p<0.05), and that of nitrate-99mTc-MIBI imaging (79%) also tended to be higher (p=0.08), than that of 201Tl imaging (62%) in detecting viable myocardium. The specificity of the 3 methods was almost the same. The nitrate-99mTc-MIBI and 201Tl-GIK methods were more useful than the resting 201Tl method for evaluating viable hibernating myocardium. Furthermore, the 201Tl-GIK method may provide a more accurate estimate of the amount of viable myocardium than the nitrate-99mTc-MIBI method.

Aged↗

PubMed2000

[Significance of exercise-induced ST segment depression in patients with myocardial infarction involving the left circumflex artery: evaluation by exercise thallium-201 myocardial single photon emission computed tomography].

The significance of exercise-induced ST segment depression in patients with left circumflex artery involvement was investigated by comparing exercise electrocardiography with exercise thallium-201 single photon emission computed tomography(Tl-SPECT) and the wall motion estimated by left ventriculography. Tl-SPECT and exercise electrocardiography were simultaneously performed in 51 patients with left circumflex artery involvement(angina pectoris 30, myocardial infarction 21). In patients with myocardial infarction, exercise-induced ST depression was frequently found in the V2, V3 and V4 leads. In patients with angina pectoris, ST depression was frequently found in the II, III, aVF, V5 and V6 leads. There was no obvious difference in the leads of ST depression in patients with myocardial infarction with ischemia and without ischemia on Tl-SPECT images. In patients with myocardial infarction, the lateral wall motion of the infarcted area evaluated by left ventriculography was more significantly impaired in the patients with ST depression than without ST depression(p < 0.01). Exercise-induced ST depression in the precordial leads possibly reflects wall motion abnormality rather than ischemia in the lateral infarcted myocardium.

Aged↗

PubMed2000

[Anatomical variations of Koch's triangle in patients with atrioventricular nodal reentrant tachycardia: usefulness of the left anterior oblique view].

OBJECTIVES: Several anatomical distances of Koch's triangle including the ablation site were measured and correlated with clinical features and slow pathway potentials in patients with atrioventricular nodal reentrant tachycardia to improve the avoidance of complete atrioventricular block. METHODS: Sixty consecutive patients (24 males and 36 females, mean age 47 +/- 12 years) with successfully eliminated atrioventricular nodal reentrat tachycardia were studied. The distances between the His-bundle area and the base of the coronary sinus ostium (Dis HBE-CS) and the distances between the successful ablation site and the base of the CS ostium (Dis SP-CS) were measured in both right anterior oblique and left anterior oblique views, and used to define the dimensions of Koch's triangle. The relationship between the slow pathway potentials at the successful ablation site and anatomical distances was estimated. RESULTS: The Dis HBE-CS in the right anterior oblique view was negatively correlated with patient age (r = -0.759, p < 0.001) and body mass index. In contrast, the Dis HBE-CS in the left anterior oblique view had only weak correlations with patient age and body mass index. The mechanism of the short Dis HBE-CS in the right anterior oblique view in elderly obese patients tended to change the shape of the tricuspid annulus from a circle to an ellipse, compressed by the ascending aorta and diaphragma. The Dis SP-CS in the right anterior oblique view associated with the low frequency potential (Haissaguerre's slow pathway potential) was longer than that associated with the high frequency potential (Jackman's slow pathway potential). CONCLUSIONS: Elderly obese patients had shorter distances between the proximal His-bundle area and the base of the coronary sinus ostium in the right anterior oblique view. In contrast, the Dis HBE-CS in the left anterior oblique view was not so narrow. Therefore, slow pathway ablation can be performed safely without complicated complete atrioventricular block, using both the slow pathway potential guided approach and the anatomical guided approach, especially in the left anterior oblique view.

Adolescent↗

PubMed1999

Metabolism of 7-fluoro-6-(3,4,5,6-tetrahydrophthalimido)-4- (2-propynyl)-2H-1,4-benzoxazin-3(4H)-one (S-53482) in rat. 1. Identification of a sulfonic acid type conjugate.

To examine the metabolic fate of 7-fluoro-6-(3,4,5, 6-tetrahydrophthalimido)-4-(2-propynyl)-2H-1,4-benzoxazin-3( 4H)-one (S-53482), rats were given a single oral dose of [phenyl-(14)C]-S-53482 at 1 (low) or 100 (high) mg/kg. The radiocarbon was almost completely eliminated within 7 days after administration in both groups. (14)C recoveries (expressed as percentages relative to the dosed (14)C) in feces and urine were 56-72 and 31-43%, respectively, for the low dose and 78-85 and 13-23%, respectively, for the high dose. S-53482 and seven metabolites were identified in urine and feces. Six of them were purified by several chromatographic techniques and identified by spectroanalyses (NMR and MS). Alcohol derivatives and an acetoanilide derivative were isolated from urine. Three sulfonic acid conjugates having a sulfonic acid group incorporated into the double bond of the 3,4,5,6-tetrahydrophthalimide moiety were isolated from feces. On the basis of the metabolites identified in this study, the metabolic pathways of S-53482 in rats are proposed.

Animals↗

PubMed1999

A quantitative comparison of induction and challenge concentrations inducing a 50% positive response in three skin sensitization tests; the guinea pig maximization test, adjuvant and patch test and Buehler test.

The sensitivities of three skin sensitization tests such as the Guinea pig maximization test (GPMT), Adjuvant and patch test (APT) and Buehler test (BT), were quantitatively compared with reference to induction and challenge concentrations. Four chemical which had different physico-chemical properties (octanol-water partition coefficient (logP) and reactivity with NH2-group) were used in order to clarify the effect of the physico-chemical properties of chemicals on the sensitivity of the different methods. The induction concentrations inducing a 50% positive response (IC50) demonstrated extreme variation with the three methods. For example, the BT/GPMT ratio of IC50 values for 2,4-dinitrochlorobenzene was 33, whereas that for maleic anhydride was 300,000. The results were thought to be caused by difference properties such as the logP and reactivity of chemicals. This correlation was confirmed by using 2-dodecen-1-yl succinic anhydride, which had the same reactivity but higher logP than that of maleic anhydride. On the other hand, the challenge concentrations inducing 50% positive responses (CC50) were less affected by the methods and the BT/GPMT ratios for CC50 values were all within a 10-fold range. These results suggest that the sensitivity might be strongly different with reference to induction concentration, but not challenge concentration among the three methods.

Adjuvants, Immunologic↗

PubMed1999

[The characteristics of myocardial fatty acid metabolism in patients with left ventricular hypertrophy].

We evaluated the characteristics of myocardial fatty acid metabolism in patients with left ventricular hypertrophy (LVH). Myocardial imaging with 123I-beta-methyl iodophenyl pentadecanoic acid (BMIPP) was performed in 28 patients with hypertrophic cardiomyopathy (HCM), 15 patients with hypertensive heart disease (HHD), 13 patients with aortic stenosis (AS) and 8 normal controls (NC). The patients with HCM consisted of 13 patients of asymmetric septal hypertrophy (ASH), 7 patients of diffuse hypertrophy (Diffuse-HCM) and 8 patients of apical hypertrophy (APH). Planar and SPECT images of BMIPP were acquired 15 minutes and 4 hours after tracer injection. Resting 201Tl SPECT images and echocardiography were also performed on other days. We calculated heart/mediastinum count ratio and washout rate of BMIPP by using planar image. In patients with LVH, the incidence of reduced BMIPP uptake was more frequent than that of reduced 201Tl uptake. In delayed images, more than 60% of patients with LVH reduced BMIPP uptake, especially remarkable for patients with ASH and APH. The washout rate of all cardiac hypertrophic disorders was tended to be higher than that of normal subjects. Reduced BMIPP uptake was frequently found in septal portion of anterior and inferior wall in patients with ASH, in inferior wall in patients with Diffuse-HCM and HHD, in apex in patients with APH and AS. These results suggest that BMIPP scintigraphy can differentiate three types of cardiac hypertrophy.

Aged↗

PubMed1999

[Effect of exercise therapy on oxygen consumption in patients with chronic heart failure].

The effect of exercise training on delta Vo2/delta WR was studied in 12 patients(11 men, one woman, mean age 62 +/- 9 yr)with chronic heart failure(old myocardial infarction, dilated cardiomyopathy, patients after coronary arterial bypass graft surgery and patients after aortic valve replacement). Cardiopulmonary exercise testing was performed to decide the exercise tolerance and assess the delta Vo2/delta WR. Patients underwent physical training at the anaerobic threshold for 3 months. Cardiopulmonary exercise testing was performed after the second week and after the third month. The anaerobic threshold increased at the third month compared with before exercise testing and the second week(p < 0.05, respectively) (before exercise testing: 13.6 +/- 2.0 ml/min/kg, the second week: 14.7 +/- 2.5 ml/min/kg, the third month: 16.2 +/- 2.1 ml/min/kg). The delta Vo2/delta WR increased at the second week compared with before exercise testing(before exercise testing: 8.9 +/- 1.9 ml/min/W, the second week: 10.6 +/- 1.9 ml/min/W, p < 0.05), but significantly decreased at the third month compared with the second week(the third month: 9.4 +/- 1.7 ml/min/W, p < 0.05). Serial increase of the anaerobic threshold and the peak Vo2/heart rate suggests that the exercise tolerance and cardiac function of the patients improved significantly. The increase of the delta Vo2/delta WR after the first 2 weeks seemed to depend on the luxury blood supply to both working and non-working muscles. The decrease of delta Vo2/delta WR at the third month may be due to the redistribution of the blood flow to the working muscles.

Chronic Disease↗

PubMed1998

Involvement of meiotic resumption in the disruption of gap junctions between cumulus cells attached to pig oocytes.

The present study was undertaken to examine the mechanisms by which cumulus cells regulate meiotic resumption in pig oocytes using microinjections of lucifer yellow into cumulus-oocyte complexes combined with a fluorescent assay. Some cumulus-oocyte complexes cultured for 0, 8, 16, 24, 32, 40 and 48 h were denuded to assess the nuclear status of oocytes; the remaining complexes were injected with lucifer yellow and monitored for the transfer from the oocyte to the surrounding cumulus cells using confocal laser scanning microscopy. The proportion of oocytes undergoing germinal vesicle breakdown at 16, 24 and 32 h of cultivation was much higher than that of cumulus-oocyte complexes in which all gap junctions within cumulus cells and between cumulus cells and oocyte were disrupted (16 h: 22.7% versus 8.8%, 24 h: 66.7% versus 40.3%, 32 h: 84.0% versus 69.4%), showing that the disruption does not trigger meiotic resumption in the pig oocyte. A significant positive correlation (r = 0.99, P < 0.01) was established between the proportion of germinal vesicle breakdown oocytes and that of cumulus-oocyte complexes exhibiting loss of gap junctions within all cumulus cell layers excluding the innermost layer. From these results, it is concluded that meiotic resumption in pig oocytes is induced by the disruption of gap junctions within cumulus cells, rather than that between the oocyte and cumulus cells, which blocks the conduction of meiosis inhibitory signals from the outer cumulus cells to the oocyte.

Animals↗