Biomedical subjects

N Minami

Publications and source records attributed to N Minami.

At least 55 records · Page 3Linked to original sources

PubMed1998

Potentiation of transmitter release by protein kinase C in goldfish retinal bipolar cells.

1. We examined whether transmitter release could be modified by the activation of protein kinase C (PKC) of retinal bipolar cells. A bipolar cell with a large axon terminal was isolated from the goldfish retina. The presynaptic Ca2+ current was measured under whole-cell voltage clamp, and the released transmitter (probably glutamate) was detected electrophysiologically by using the response of NMDA receptors of catfish horizontal cells as a reporter. 2. Transmitter release was potentiated by a PKC activator, phorbol 12-myristate 13-acetate (PMA), but not by an ineffective phorbol ester, 4alpha-phorbol 12,13-didecanoate. A PKC inhibitor, bisindolylmaleimide I, did not affect the transmitter release by itself but blocked the PMA-induced potentiation of transmitter release. These results suggest that the actions of PMA were mediated via the activation of PKC. 3. Introduction of 5 mM EGTA into the presynaptic terminals of bipolar cells revealed two separate components of transmitter release. A rapid component was triggered immediately after depolarization while a slow component appeared with a delay. Application of PMA selectively potentiated the slow component without affecting the Ca2+ dependence of exocytosis. 4. We suggest that the activation of PKC may modify the recruitment process of synaptic vesicles in retinal bipolar cells.

Animals↗

PubMed1998

Granulocyte colony-stimulating factor and its receptor in acute promyelocytic leukemia.

Expression of granulocyte colony-stimulating factor (G-CSF) receptor (G-CSFR) and in vitro proliferative response to G-CSF were investigated by quantitative immunofluorescence and [3H] thymidine uptake, respectively, in a series of acute myeloid leukemias (AML). The results indicated that G-CSFR was detected at high levels in acute promyelocytic leukemia (APL) cells, in comparison with other types of AML. Moreover, APL cells were also seen to predominantly proliferate in response to G-CSF. Based on these observations, we administered recombinant human G-CSF to a patient with APL in the third relapse that was resistant to both cytotoxic agents and all trans retinoic acid, in an attempt to sensitize the leukemic cells to cell-cycle-dependent agents. Complete remission was achieved. The finding that APL cells are exquisitely responsive to G-CSF supports the view that G-CSF is useful for augmentation of their vulnerability to cell-cycle specific agents.

Adult↗

PubMed1998

Effects of cumulus cell density during in vitro maturation of the developmental competence of bovine oocytes.

To determine the role of cumulus cells in oocyte maturation, we carried out an investigation on the effects of addition of cumulus cells to the maturation medium on the developmental competence of corona-enclosed oocytes and oocytes denuded from their somatic cells. The addition of cumulus cell (1.6 x 10(6) cells/mL) improved the development of bovine corona-enclosed oocytes, however, addition of a similar number of cumulus cells as cumulus-oocyte-complexes (COCs, cumulus cell density: 4.2 x 10(6) cells/mL) had no effect on the development of oocytes denuded from their somatic cells. To determine if corona-enclosed oocytes can obtain developmental competence without the addition of extra cumulus cells, the effects of cell density during in vitro maturation on the developmental competence were studied. A density of 1.6 to 3.2 x 10(6) cumulus cells/mL was the most effective for in vitro maturation of oocytes with intact gap junctions. The effects of the medium conditioned by COCs on the developmental competence of oocytes was also examined. It was demonstrated that COC-conditioned medium improved the development of bovine oocytes to the blastocyst stage. These data suggest that the developmental competence of bovine oocytes surrounded with corona cells is supported in a cell density-dependent manner in the maturation medium. In addition, the data indicate that cumulus cells benefit bovine oocyte development either by secreting soluble factors which induce developmental competence or by removing an embryo development-suppressive component from the medium.

Animals↗

PubMed1998

Effects of antioxidants on the development of bovine IVM/IVF embryos in various concentrations of glucose.

This study was undertaken to determine the effects of glucose, antioxidants and different oxygen tensions on the development of bovine embryos cultured in modified synthetic oviduct fluid (m-SOF) medium. In vitro matured (IVM) and fertilized (IVF) oocytes were incubated for 48 h. Embryos reaching at least the 4-cell stage were selected for further culture under various conditions for 6 d. Supplementing the m-SOF media with 4.5 mM glucose resulted in a significantly lower (P < 0.01) embryo developmental rate (21%; Day 8) than was obtained with 1.5 mM glucose (58%; Day 8) or no glucose (53%; Day 8). Antioxidants such as SOD, catalase and mannitol had no positive effect on embryo development in m-SOF medium supplemented with 1.5 mM glucose. However, in m-SOF medium supplemented with 4.5 mM glucose, SOD and mannitol significantly (P < 0.05) improved embryo development: SOD increased the developmental rate from 19 to 35% (Day 8), while mannitol increased it from 13 to 30% (Day 8). Low oxygen concentration improved embryo development significantly (P < 0.05) in m-SOF medium supplemented with 4.5 mM glucose (low O2: 31% vs high O2: 14%; Day 8) but not 0 mM glucose (low O2: 58% vs high O2: 55%; Day 8). Our data suggest that low concentration of glucose during culture of bovine embryos is beneficial, and that generation of free oxygen radicals is partly caused by a high concentration of glucose in the medium.

Animals↗

PubMed1998

Dystrophin gene analysis on 130 patients with Duchenne muscular dystrophy with a special reference to muscle mRNA analysis.

On dystrophin gene analysis by multiplex polymerase chain reaction (PCR), 76 of 130 (58.5%) Japanese patients with Duchenne muscular dystrophy had a deletion or duplication in genomic DNA. Of the remaining 54 patients who had no identifiable gene mutations, muscle biopsy tissue was available in 16 for RNA extraction. The full length of the coding regions of dystrophin cDNA was amplified in 10 fragments by reverse transcription nested PCR (RT-PCR). Five of 16 patients (31%) had dystrophin cDNA of abnormal size. One patient had a deletion, and two duplications that were not covered by multiplex PCR, one an exon-skipping of exon 51 caused by a 5' consensus splice site mutation of intron 51, and one 172 bp or 202 bp insertion in the cDNA between exon 25 and 26. Nested RT-PCR from the total RNA extracted from muscle biopsy was useful for screening patients who had no identifiable gene abnormality by multiplex PCR.

Adolescent↗

PubMed1998

MTM1 gene mutations in Japanese patients with the severe infantile form of myotubular myopathy.

The severe infantile form of myotubular myopathy is a fatal muscle disease that predominantly affects male infants and is characterized by severe weakness and hypotonia from birth. X-linked myotubular myopathy was found to be associated with mutations in the MTM1 gene in Xq28 encoding the putative tyrosine phosphatase, myotubularin. We screened the MTM1 gene for mutations in seven Japanese patients (six males and one female) who had the diagnosis of severe infantile form of myotubular myopathy. We found five mutations, including three novel mutations based on sequence analysis of RT-PCR fragments covering the entire open reading frame. Two patients (one male and one female), who had similar clinicopathologic features, did not have any mutation in the MTM1 gene open reading frame, suggesting that they may have had an autosomal recessive disease.

Child, Preschool↗

PubMed1998

Studies on agents with vasodilator and beta-blocking activities. V. Synthesis and pharmacological activity of the optical isomers of TZC-5665.

Synthesis of the four optical isomers of TZC-5665 (1), a candidate for the treatment of congestive heart failure, was achieved by the reaction of chiral diaminopyridazinone (2) with chiral glycidyl ether. (3). The hypotensive and beta-blocking activities of 1 and its optical isomers were examined when given intravenously into anesthetized rats. Furthermore these compounds were evaluated for inhibitory activity on cAMP phosphodiesterase III. Among the four optical isomers, Ra,Sb-one (1c) possessed the essential activities of TZC-5665 (1).

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1998

Successful treatment of aplastic anemia with G-CSF and high dose erythropoietin.

We report the successful treatment of pancytopenia with G-CSF and high dose erythropoietin (Epo) in an elderly patient diagnosed with aplastic anemia (AA). Furthermore this effect is dose dependent for Epo in vivo. Detection of apoptosis by gel electrophoresis shows that high dose Epo protects bone marrow mononuclear cells from spontaneous apoptosis in vitro. These findings may explain some of the mechanisms of aplastic anemia.

Aged↗

PubMed1997

Evaluation of acrosomal status of bovine spermatozoa using concanavalin a lectin.

We report here that fluorescein isothiocyanate-conjugated concanavalin A (FITC-ConA) specifically labels the acrosomal region of acrosome-reacted bovine spermatozoa. This labeling is found to be useful in evaluating the acrosome status of bovine spermatozoa. When fresh bovine spermatozoa that had been fixed with 4% formaldehyde, smeared on glass slides and then air-dried were stained by FITC-ConA, weak fluorescence was observed on the acrosomal region, although almost all the spermatozoa appeared to be acrosome-intact. However, when fresh sperm suspensions were incubated with FITC-ConA and then mounted on glass slides, no fluorescence was observed on the acrosomal region. Therefore, in the ensuing experiments, both the fixation and the FITC-ConA staining of spermatozoa were done in suspension. When ethanol-treated spermatozoa, whose outer membrane may be permeabilized, were stained with FITC-ConA, the fluorescence was extensively observed on the inner acrosomal region. This fluorescence was inhibited in the presence of 0.2 M D-mannose, a competitive sugar, suggesting that FITC-ConA binds specifically to glycocomponents on the inner acrosomal membrane. We next tried to stain fresh or frozen-thawed spermatozoa from 3 different bulls that had been treated with the calcium ionophore A23187, which is known to induce acrosome reaction of bovine spermatozoa, with FITC-ConA. A significant correlation between the percentage of ConA-labeled spermatozoa and that of rose bengal stained negative ones at various time points during A23187 incubation was achieved. Furthermore, suitability of dual staining to distinguish between physiological acrosome reaction (acrosome-lost and live) and degenerative acrosomal loss (acrosome-lost and dead) using FITC-ConA and Hoechst bis-benzimide 33258 (H258) supravital stain was also confirmed. From these results, it was concluded that the FITC-ConA labeling procedure is a feasible and reliable method for the assessment of physiological acrosome reaction of bovine spermatozoa.

Journal Article↗

PubMed1997

Inhibition of shear stress-induced platelet aggregation by cilostazol, a specific inhibitor of cGMP-inhibited phosphodiesterase, in vitro and ex vivo.

Cilostazol(6-[4-(1-cyclohexyl-1H-tetrazol-5-yl)-butoxy]-3,4- dihydro-2(1H)-quinolinone) selectively inhibits cGMP-inhibited phosphodiesterase (PDE3) and is a potent inhibitor of platelet aggregation induced by various agonists. Effect of cilostazol on shear stress-induced human platelet aggregation (SIPA) was examined in vitro and ex vivo. Cilostazol inhibited SIPA dose-dependently in vitro. The IC50 value of cilostazol for inhibition of SIPA was 15 +/- 2.6 microM (m +/- SE, n=5), which was very similar to that (12.5 +/- 2.1 microM) for inhibition of ADP-induced platelet aggregation. Cilostazol potentiates the inhibition of SIPA by PGE1 and enhances its ability to increase cAMP concentrations. A single oral adminstration of 100 mg cilostazol to healthy volunteers produced a significant inhibition of SIPA. This study demonstrates that cilostazol is an effective inhibitor of SIPA, which may be important for the prevention and the treatment of arterial occlusive diseases.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1997

Two components of transmitter release in retinal bipolar cells: exocytosis and mobilization of synaptic vesicles.

Ca2+-transmitter release coupling was examined using bipolar cells with large presynaptic terminals dissociated from the goldfish retina. Presynaptic Ca2+ current (I(Ca)) was recorded under the whole-cell voltage clamp. Release of excitatory amino acid transmitter was simultaneously monitored as the current through N-methyl-D-asperate (NMDA) receptors of reporter cells or as the membrane capacitance (C(m)) change associated with exocytosis. When I(Ca) was activated by a long depolarizing pulse, a double-peaked transmitter-induced current (I(tr)) was elicited in reporter cells. The rapid component of I(tr) was evoked immediately after the onset of depolarization, and was affected only slightly by intracellularly applied Ca2+ chelators. The delayed slow component of I(tr) was elicited during depolarization once a fixed amount of Ca2+ was accumulated in presynaptic terminals, and its appearance was suppressed or retarded by Ca2+ chelators. Two components of transmitter release were also recognized by monitoring C(m) changes elicited by the activation of I(Ca). These results suggest that bipolar cells have at least two pools of synaptic vesicles; a small, immediately releasable pool and a large releasable pool. The rapid and the delayed slow components of transmitter release may reflect exocytosis and mobilization of synaptic vesicles, respectively.

Animals↗

PubMed1997

Reproducibility of home blood pressure measurements over a 1-year period.

We compared the reproducibility over time of blood pressure measured at the health examinations (screening blood pressure) and blood pressure measured at home (home blood pressure). Both screening and home blood pressure were measured in subjects of a rural community. Subjects measured their own blood pressure at home once in the morning using a semiautomatic oscillometric blood pressure measuring device at least three times (on at least 3 days) in each of two 4-week periods separated by one year. Similarly, two screening blood pressure measurements were obtained from the subjects at each of two health examinations also taken 1 year apart. A total of 136 untreated subjects without cardiovascular complications (40 men and 96 women, 56 +/- 11.7 years, mean +/- SD) were analyzed in the study. The correlations between the first and second blood pressure measurements of the subjects were significantly higher for the home blood pressure measurements (systolic: r = 0.844 and diastolic: r = 0.830) than for the screening blood pressure measurements (systolic: r = 0.692 and diastolic: r = 0.570). The mean differences between the first and second home blood pressure (0.8 +/- 7.7 mm Hg for systolic BP and 0.9 +/- 5.5 mm Hg for diastolic BP) were significantly smaller than those for the screening blood pressure (-3.9 +/- 13.8 for systolic BP and -3.1 +/- 10.2 for diastolic BP) (P < .001 for both comparisons), suggesting that the reproducibility of home blood pressure over time is superior to that of screening blood pressure. Such reliable blood pressure measurements obtained at home have a clinical significance for the diagnosis and treatment of hypertension and as a tool for evaluating the efficacy of antihypertensive drugs. Home blood pressure measurements also may be more useful than screening blood pressure measurements in predicting future cardiovascular events.

Adult↗

PubMed1997

Relation between nocturnal decline in blood pressure and mortality. The Ohasama Study.

To investigate the relation between nocturnal decline in blood pressure and mortality, we obtained ambulatory blood pressures in 1542 residents aged 40 years or over of a rural Japanese community. Subjects were followed-up for a mean of 5.1 years and were then subdivided into four groups according to the percent decline in nocturnal blood pressure: 1) extreme dippers: percent decline in nocturnal blood pressure > or = 20% of the daytime blood pressure; 2) dippers: decline of > or = 10% but < 20%; 3) nondippers: decline of > or = 0% but < 10%; and 4) inverted dippers: no decline. The relationship between the decline in nocturnal blood pressure and mortality was examined by the Cox proportional hazards regression model adjusted for age, sex, smoking status, previous history of cardiovascular disease, and the use of antihypertensive medication. The mortality risk was highest in inverted dippers, followed by nondippers. There was no difference in mortality between extreme dippers and dippers. This relationship was observed for both treated and untreated subjects, was more pronounced for cardiovascular than for noncardiovascular mortality, and did not change after the data were adjusted for 24-h, daytime, and nighttime blood pressure levels.

Aged↗

PubMed1997

Factors that affect blood pressure variability. A community-based study in Ohasama, Japan.

Factors that affect blood pressure (BP) variability, ie, standard deviation (SD) and variation coefficient (VC: SD/average ambulatory BP) of ambulatory BP, were examined in a community-based sample in northeastern Japan. Screening and ambulatory BPs were measured in 823 subjects > or = 20 years of age, and the effects of age and BP on the SD and the VC were examined. In bivariate regression analysis, the SD of ambulatory BP was positively correlated with age and the ambulatory BP. The VC was also correlated with age. Both the SD and the VC were strongly correlated with the magnitude of the nocturnal decline in BP. Ambulatory BP was positively correlated with age and negatively correlated with heart rate and the SD of heart rate. Multivariate analysis demonstrated that the nocturnal decline in BP showed the strongest association with the SD and the VC of 24-h BP. However, age and BP were still independently and positively associated with the SD and the VC of ambulatory BP. Furthermore, pulse pressure and BMI were independently and positively associated with the SD and the VC of ambulatory BP. Since the SD and the VC of 24-h ambulatory BP were determined mainly by the nocturnal decline in BP, this variable appears to be an index of the circadian variation in BP and not an index of short-term BP variability. Pulse pressure, an index of arterial stiffness, was a relatively strong predictor of the SD and the VC of BP. In addition, the SD of heart rate, an index of baroreflex function, decreased with increasing age. Findings suggest that the increase in BP variability in hypertensive and elderly subjects may be explained, in part, by a disturbance of baroreflex function associated with an increase in arterial stiffness due to aging and hypertension.

Adult↗

PubMed1997

Follicular cells affect the fertilizability and developmental competency of bovine oocytes in vitro.

The present study examined the time-dependent effects of follicular cells on the fertilizability of oocytes and their subsequent development to blastocysts. The percentages of oocytes reaching the metaphase-II stage of maturation rose from 51.3% after 16 h of culture to 86.2% at 28 h (cumulus-intact oocytes; CIO) and, for the same time points, from 65.4% to 83.3% (corona-enclosed oocytes; CO) and 54.3% to 88.9% (denuded oocytes; DO), respectively. When DO were cultured for more than 24 h before insemination, fertilization rates were significantly lower compared with CIO and CO. The maximum rates of development to blastocysts were observed when the oocytes were cultured for 24 h in the CIO group (22.1%), 20 h in the CO group (19.7%) and 18 h in the DO group (9.2%), respectively. These results suggest that (i) the presence of cumulus cells or corona cells during maturation is not necessary for nuclear maturation of oocytes; (ii) the attachment of corona cells to the oocytes during maturation is important for the further development to the blastocyst stage, and (iii) the presence of attached cumulus and/or corona cells during maturation in vitro extends the maturation period required for further development to the blastocyst stage.

Animals↗

PubMed1997

Prediction of mortality by ambulatory blood pressure monitoring versus screening blood pressure measurements: a pilot study in Ohasama.

OBJECTIVE: To compare the prediction of mortality by ambulatory blood pressure monitoring and screening blood pressure measurements in a general population. DESIGN: A prospective cohort study. PATIENTS AND METHODS: We obtained blood pressure data for 1542 subjects (565 men and 977 women) aged > or = 40 years who were followed up for up to 8.1 years (mean 5.1 years). Subjects were subdivided into five groups according to their ambulatory and screening blood pressure levels. The prognostic significance of blood pressure for mortality was examined by the Cox proportional hazards regression model. RESULTS: The association between blood pressure level and mortality was more distinctive for the ambulatory blood pressure than it was for the screening blood pressure. The risk of cardiovascular mortality increased significantly for the highest quintiles of 24 h ambulatory blood pressure, whereas there was no significant association between the screening blood pressure and the cardiovascular mortality. When both 24 h and screening blood pressure values were included in the Cox model, only the systolic ambulatory blood pressure was related significantly to the increased risk of cardiovascular mortality. CONCLUSIONS: The ambulatory blood pressure had a stronger predictive power for mortality than did the screening blood pressure. This appears to have been the first study of the prognostic significance of ambulatory blood pressure monitoring versus screening blood pressure measurements in a general population.

Adult↗

PubMed1997

Role of nitric oxide in the development of vascular alpha 1-adrenoreceptor desensitization and pressure diuresis in conscious rats.

We evaluated whether a minor impairment of the L-arginine-nitric oxide pathway would affect the desensitization of vascular alpha-adrenoreceptor and pressure diuresis induced by prolonged intravenous infusion of phenylephrine (an alpha-adrenoreceptor agonist) in conscious Wistar-Kyoto rats. We examined dose-pressor-response curves to phenylephrine after an intravenous infusion of phenylephrine (2.5 micrograms.kg-1.min-1) or saline for 9 hours with and without concomitant infusion of N omega-L-arginine methyl ester (L-NAME) given to partially inhibit the L-arginine-nitric oxide pathway. In addition, to evaluate the effect of plasma volume loss on the pressor response to phenylephrine, we evaluated the dose-pressor-response curves to phenylephrine after intravenous injection of furosemide (5 mg/kg) or infusion of phenylephrine (5 micrograms.kg-1.min-1) for 9 hours. The renin-angiotensin, vasopressin and autonomic nervous systems were blocked before the examination of dose-pressor responses. Prolonged infusion of phenylephrine (2.5 micrograms.kg-1.min-1) shifted the dose pressor-response curve to this agent rightward, with significantly increased log ED50 (the dose needed to reach 50% of the maximal response) to a similar extent in both L-NAME-treated (0.51 +/- 0.05 versus 0.93 +/- 0.07 microgram/kg) and -untreated (0.79 +/- 0.06 versus 1.08 +/- 0.03 micrograms/kg) rats. The log ED50 value after phenylephrine infusion (5 micrograms.kg-1.min-1) was significantly higher than that after furosemide injection (1.28 +/- 0.06 versus 1.02 +/- 0.01 micrograms/kg, respectively, P < .01), although the two treatments induced a similar loss of plasma volume. The slope in the linear relationship between the average change in mean arterial pressure during the 9-hour infusion period and the rate of urine excretion was significantly depressed in L-NAME-treated versus control rats (L-NAME: 0.057 mL.kg-1.h-1.mm Hg-1, control: 0.146 mL.kg-1.h-1.mm Hg-1, P < .05). In conclusion, a minor impairment of the L-arginine-nitric oxide pathway does not appear to interfere with the desensitization of vascular alpha-adrenoreceptor but does inhibit the pressure-diuresis response in conscious normotensive rats.

Analysis of Variance↗

PubMed1997

Expression of epidermal growth factor receptor in fetal mouse submandibular gland detected by a biotinyltyramide-based catalyzed signal amplification method.

Branching morphogenesis of the fetal mouse submandibular gland (SMG) can be modulated in vitro by stimulation or inhibition of the epidermal growth factor receptor (EGFR). Because the mRNAs for EGF and EGFR are detectable in RNA of SMG rudiments isolated directly from fetuses, the EGF system probably operates physiologically as a regulator of SMG morphogenesis. However, neither EGFR protein nor its precise cellular localization has been characterized in the fetal SMG. Here we show EGFR protein in fetal mouse SMG by immunoprecipitation, affinity labeling, ligand-induced autophosphorylation, and immunohistochemistry. SMGs from E16 fetuses (day of vaginal plug = E0) were labeled with [35S]-cysteine/methionine and homogenized. After addition of specific antibody to EGFR, the immunoprecipitate was isolated, resolved by polyacrylamide gel electrophoresis, and detected by autoradiography. A single band of 170 kD was detected, corresponding to the EGFR protein. Affinity labeling with [125I]-EGF of the membrane fraction of E18 SMG also revealed a prominent band at 170 kD, showing that this EGFR protein can bind specifically to its ligand. Incubation of SMG membranes from E18 fetuses with EGF in the presence of [gamma-32P]-ATP, followed by immunoprecipitation with anti-phosphotyrosine antibody also showed a single band at 170 kD, demonstrating autophosphorylation of the EGFR in response to binding of its ligand. Immunohistochemical localization of the cellular sites of EGFR in the fetal SMG required use of a catalyzed signal amplification procedure, with biotinyltyramide as the amplifying agent. EGFR was localized predominantly, if not exclusively, in cell membranes of epithelial cells of the rudiment, whereas staining of mesenchymal cells was equivocal. Staining was strongest on duct cells, and weak on cells of the end-pieces. These findings clearly show that a functional EGFR protein is expressed in fetal SMG chiefly, if not exclusively, on epithelial cells.

Affinity Labels↗