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Biomedical subjects

A Fukuda

Publications and source records attributed to A Fukuda.

At least 145 records · Page 8Linked to original sources
PubMed1992

Influences of in vitro oocyte aging on microfertilization in the mouse with reference to zona hardening.

PURPOSE: Our purpose was to investigate the influence of in vitro oocyte aging on fertilization and subsequent embryonic development following subzonal sperm injection with reference to spontaneous zona hardening in the mouse. RESULTS: First cleavage rate was significantly higher in long vs short (69 vs 41%, P < 0.001). However, significantly higher blastocyst formation and hatching were observed in short than long (50 vs 7%, P < 0.001, and 86 vs 50%, P < 0.001, respectively). No significant differences were found for two pronuclei formation between short and long (30 vs 27%). Sham injection revealed a significantly higher parthenogenetic activation in long than short (19 vs 2%, P < 0.001). Zona digestion required a significantly longer time for long compared to short (trypsin--37 vs 29 min, P < 0.01; pronase--17 vs 14 min, P < 0.001). CONCLUSIONS: Prolonged culture of mature mouse oocytes in vitro alters the zona pellucida, increases the rate of parthenogenetic activation by subzonal sperm injection, and impairs subsequent embryonic development. Zona hardening appears to be an indicator of oocyte aging.

Animals↗
PubMed1992

ras mutations in endocrine tumors: mutation detection by polymerase chain reaction-single strand conformation polymorphism.

To elucidate the molecular basis for endocrine tumorigenesis, ras mutations in human endocrine tumors were analyzed using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis. Mutations of the H-, K-, N-ras genes were examined in genomic DNAs from 169 successfully amplified primary endocrine tumors out of 189 samples. Four out of 24 thyroid follicular adenomas analyzed contained mutated N-ras codon 61, and one contained the mutated H-ras codon 61. One of the 19 pheochromocytomas revealed mutation of the H-ras codon 13. No mutations of the ras gene were detected in pituitary adenomas, parathyroid tumors, thyroid cancers, endocrine pancreatic tumors, and adrenocortical tumors. Based on these findings we conclude that activation of the ras gene may play a role in the tumorigenesis of a limited number of thyroid follicular adenomas and pheochromocytomas, and that mutation of the ras gene is not frequent in other human endocrine tumors.

Adult↗
PubMed1992

Excessive intracellular Ca2+ inhibits glutamate-induced Na(+)-K+ pump activation in rat hippocampal neurons.

1. The effects of increased intracellular Ca2+ concentration ([Ca2+]i) on Na(+)-K+ pump activity in CA1 pyramidal neurons of rat hippocampal slices were investigated. The postglutamate hyperpolarization (PGH), which follows glutamate (GLU)-induced depolarization (GD), was used as an index of Na(+)-K+ pump activity, as was a ratio of PGH area to the preceding GD area (PGH ratio). 2. Perfusion of slices with saline containing Ca2+ ionophore (A23187, 10 microM) inhibited the PGH without producing apparent signs of cell deterioration. A 60-100% (85 +/- 15%, mean +/- SD) reduction in the PGH ratio occurred after 20-50 min of A23187 superfusion in 12 of 18 neurons tested. Complete abolition of the PGH occurred in 8 of these 12 cells exposed to A23187 for 30-120 min. 3. Application of A23187 in Ca(2+)-free/high-Mg2+ solution did not abolish the PGH, although small (less than 50%; 37 +/- 10%) reductions in the PGH ratio were observed after perfusion of 50 min or longer in five neurons tested. 4. Intracellular injection of the Ca2+ chelator bis-(o-amino-phenoxy)-N,N,N',N'-tetraacetic acid (BAPTA, 300-400 mM) blocked inhibition of the PGH by A23187. After 50 min of perfusion with Ca2+ ionophore, no reduction of the PGH ratio was observed in five neurons tested. 5. Rundown of the PGH without apparent change in membrane properties was observed in three neurons that were stable for greater than 2-3 h, allowing repetitive GLU applications. 6. Block of the PGH produced by a Na(+)-K(+)-adenosinetriphosphatase (ATPase) inhibitor (strophanthidin) prolonged the duration of GDs because of a delay in repolarization.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

[Color sensation of pseudophakic eye from a viewpoint of electrophysiological study].

Monochromatic ERG b-waves were recorded in normal eyes, cataractous eyes and pseudophakic eyes implanted with non-UV or UV IOLs. ERG b-waves were elicited by fourteen monochromatic stimulus lights ranging from 400 to 660 nm under white light adaptation, and spectral response curves were obtained from b-wave amplitudes. Compared with normal eyes or cataractous eyes, the relative b-wave amplitude of pseudophakic eyes was significantly larger in the short wavelength range from blue to green. Except for 400 nm, the spectral response curve of the eyes implanted with UV IOLs was similar to that of eyes implanted with non-UV IOLs. These results suggested that dyschromatopsia might not only occur in eyes implanted with non-UV IOLs but in eyes with UV IOLs.

Aged↗
PubMed1991

Orientation of mineral in bovine bone and the anisotropic mechanical properties of plexiform bone.

Angular dependent Young's modulus E phi presented by Bonfield and Grynpas [Nature 270, 453-454 (1977)] was simulated by using the distribution function of the orientation of mineral in plexiform bone introduced on the basis of an X-ray pole figure analysis (XPFA) and a small angle X-ray scattering (SAXS) results. Calculations were performed with the aid of a simple model which expresses well the geometrical characteristic of plexiform bone. Estimated angular dependent Young's modulus in terms of the distribution of mineral orientation reproduced the experimental results. The suitable aspect ratio of bone mineral for the reproduction of the empirical data was a reasonable value compared with the morphological study of bone mineral. It is concluded that the angular dependence of mechanical properties of plexiform bone is explained by the distribution of bone mineral orientation and its morphology.

Animals↗
PubMed1991

Determination of leukocyte elastase concentration in plasma and serum by a simple method using a specific synthetic substrate.

The concentration of leukocyte elastase (ELP) in plasma and serum was determined by an amidolysis method using a specific synthetic substrate for ELP, Suc-Ala-Tyr-Leu-Val-pNA. Results were compared with those using ELISA. ELP levels in plasma from healthy donors were similar to those determined by ELISA; however, the levels in serum were lower than those determined by ELISA. Correlation coefficients of ELP levels in plasma and serum as measured by the two methods were 0.75 (amidolysis) and 0.90 (ELISA). On the other hand, the correlation coefficient between serum ELP by the two methods was 0.83. Half of the ELP levels in plasma from 150 patients and serum from 400 patients were significantly elevated when compared with those from healthy donors, and the ELP elevation determined by amidolytic assay correlated with some variables in blood, namely fibrin(ogen)-degraded products, fibrinogen, GOT, GPT, gamma-GTP, LDH and leucine aminopeptidase. Despite the fact that the amidolysis method detects the alpha 2-macroglobulin-ELP complex while ELISA detects the alpha 1-antitrypsin-ELP complex, a comparative study showed amidolysis to provide sufficiently sensitive measurement of both plasma and serum ELP.

Adult↗
PubMed1990

17 beta-estradiol depolarization of hypothalamic neurons is mediated by cyclic AMP.

The process by which 17 beta-estradiol rapidly modulates the excitability of neurons in the ventromedial hypothalamus, a facilitation center of female sexual behavior and satiety center of feeding behavior, through mediation by cyclic nucleotides, was investigated by intracellular recording from the guinea pig brain slice preparations. Two types of short-term responses were produced by depolarization with decreased K+ conductance and hyperpolarization with increased K+ conductance. These two responses were enhanced by the phosphodiesterase inhibitor, isobutylmethylxanthine. However, the specific adenylate cyclase activator, forskolin, enhanced only the depolarization. The analogue of cyclic adenosine 3',5'-monophosphate (cAMP), 8-bromo-cAMP, induced only depolarization, the ionic mechanism of which was similar to that of 17 beta-estradiol. In addition, the possibility of non-specific effects of cyclic nucleotides was precluded by an experiment using an analogue of cyclic guanosine 3',5'-monophosphate (cGMP), 8-bromo-cGMP, which hyperpolarized neurons. Thus, the present study strongly suggests that the production of depolarizing responses of neurons in the hypothalamus produced by estradiol is specifically mediated through cAMP.

1-Methyl-3-isobutylxanthine↗
PubMed1990

Glycine-insensitive desensitization of N-methyl-D-aspartate receptors in acutely isolated mammalian central neurons.

Acutely isolated rat central neurons were recorded by whole-cell voltage-clamp and responses to a class of excitatory amino acid N-methyl-D-aspartate (NMDA) were examined. Rapid application of NMDA evoked inward current consisted of a fast initial peak followed by a sustained component. Glycine potentiated both initial and desensitized states of the NMDA response with identical concentration-dependence. The initial response, but not the sustained component, was abolished when low concentration of NMDA was pre-applied, and glycine could not reverse the desensitization. This evidence suggests that the NMDA receptor desensitization is sensitive to NMDA but not to glycine, and support the hypothesis that glycine initiates the activation of NMDA receptors rather than that glycine prevents desensitization at NMDA receptors in these cells.

Animals↗
PubMed1990

Improvement in potency assay of measles-mumps-rubella trivalent vaccine: interference between components and measures for its elimination.

In the potency assay of trivalent measles-mumps-rubella (MMR) vaccine by the immunocytochemical focus assay reported previously (Fukuda et al., 1987), development of rubella foci in RK13 cells was inhibited in the presence of a large excess of mumps component, resulting in an underestimation of the titre of the rubella component. When RK13 cells are infected with the mixture of mumps and rubella viruses, mumps virus interfered with the growth of rubella virus. Interference was mediated most likely by interferon induced by mumps virus. The interference was eliminated by a partial neutralization of mumps component by the addition of anti-mumps serum to the inoculum to RK13 cells. Improved method of potency assay of MMR vaccine incorporating the above measures and other modifications are described.

Animals↗
PubMed1990

Excitatory amino acid response in isolated nucleus tractus solitarii neurons of the rat.

The excitatory amino-acid-induced currents in nucleus tractus solitarii neurons freshly isolated from rats were investigated in a whole-cell recording mode using a conventional patch-clamp technique. At a holding potential of -70 mV, L-glutamate (Glu), N-methyl-D-aspartate (NMDA) with 10(-9) M glycine, kainate (KA), quisqualate (QA) and L-aspartate (Asp) evoked inward currents. The currents increased in a sigmoidal fashion with increasing agonists concentration. The half-maximum concentration (EC50) values were 5 x 10(-5) M for Glu, 10(-6) M for QA, 10(-4) M for KA, 6 x 10(-5) M for NMDA and 5 x 10(-5) M for Asp. The Hill coefficients of the Glu-, QA-, KA-, NMDA- and Asp-induced responses were 1.0, 1.3, 1.1, 1.3 and 1.1, respectively. The Glu-, QA-, NMDA- and Asp-induced currents consisted of a transient initial peak and a successive steady-state component showing no desensitization. These currents had the same reversal potential near +5 mV. In the current-voltage (I-V) relationships for the Glu-, NMDA- and Asp-induced currents, slight outward rectifications were observed in Mg2(+)-free external solution at membrane potentials negative to 0 mV. In the presence of extracellular Mg2+, the currents induced by Glu, NMDA and Asp were suppressed at negative membrane potentials, but the suppression was less for the Glu response. The I-V relationships for QA- and KA-induced responses were almost linear at a membrane potential between -90 and +50 mV with or without the presence of Mg2+.

Amino Acids↗
PubMed1990

Hyperpolarizing action of enkephalin on neurons in the dorsal motor nucleus of the vagus, in vitro.

Intracellular recordings were made from neurons of the dorsomotor vagal nucleus (DMV) in slices of rat medulla oblongata. [D-Ala2, D-Leu5]-enkephalin (DADLE), applied by perfusion (0.01-3 microM) or droplets, dose-dependently hyperpolarized 85% of the DMV neurons tested. The hyperpolarization, associated with a decrease in membrane resistance, persisted after elimination of synaptic activity by perfusion with Ca2(+)-free/high-Mg2+ solution or with 1 microM TTX solution. The opioid antagonist, naloxone, reversibly inhibited DADLE-induced hyperpolarization. The hyperpolarization depended on extracellular K+ concentration and reversed at about -90 mV. DADLE also decreased Ca2(+)-dependent spike duration and after-hyperpolarization (AHP). DAGO (a selective mu-receptor agonist), but not DPLPE (a selective delta-receptor agonist), mimicked DADLE's effects on membrane potential, Ca2(+)-dependent spike duration, and AHP. It is concluded that DADLE, through postsynaptic mu-type opioid receptors, hyperpolarized DMV neurons by increasing K+ conductance, which may have an inhibitory effect on DMV output. DADLE-induced decrease of spike duration and AHP was also mediated by mu-receptors and could have additional effects on functions of the DMV neuron by virtue of reduction in Ca2+ entry.

Action Potentials↗
PubMed1990

Flow waveform analysis and long-term results of autogenous saphenous vein and polytetrafluoroethylene grafts in 140 arterial reconstructions of the lower limbs.

In previous work we have found that the outcome of grafts in the lower limbs correlated with the flow waveform pattern of the artery. We have retrospectively reviewed 140 femoro-popliteal bypass operations involving the use of 75 saphenous vein grafts and 65 polytetrafluoroethylene (PTFE) grafts. For grafts with type 0 or I flow waveform pattern the patency at 4 years (56%) was superior to grafts with the type II, III or IV flow waveform (35%) patterns (P less than 0.05). For saphenous vein grafts with type 0 or I flow, the patency rate was 78% at 3 years and 69% at 5 and 8 years. In contrast with type II, III or IV flow the patency rate was 52% at 3 years, 48% at 5 years and 34% at 8 years, with a statistical significance at 4 years (P less than 0.05). PTFE grafts with type 0 or I flow showed a tendency toward an increased patency which was not significant in comparison with the grafts with type II, III or IV flow (P = 0.12). Saphenous vein grafts with type II flow patterns had an increased occlusive rate in the first year whereas PTFE grafts had the same tendency within 2 years. In both types of graft, early occlusions within a month of operation were encountered in grafts with a type III or IV flow waveform pattern. These results indicate that the fate of the reconstructed arteries of the lower limb could be predicted by flow waveform analysis, and a careful and serial postoperative evaluation of the graft should be made, particularly those with type II, III or IV flow waveform patterns.

Blood Vessel Prosthesis↗
PubMed1990

Expression of class II major histocompatibility complex antigen on mouse sperm and its roles in fertilization.

The expression of class II major histocompatibility complex (MHC) antigen on the membrane of mouse sperm head was clearly demonstrated by indirect immunofluorescence (IIF) test, enzyme immunoassay (EIA), and mixed lymphocyte sperm reaction (MLSR) as well as the examination of its expression at transcriptional levels by northern dot blotting. Furthermore, the roles of class II MHC antigen of sperm in fertilization were investigated with an in vitro fertilization (IVF) system. The successful ratio of IVF was significantly decreased by treatment of sperm with anticross-reactive region of class II MHC antigen monoclonal antibody (MAb) but not with antiprivate region MAb. These results were not due to disturbances of sperm mobility by these MAbs. It was strongly suggested that the monomorphic or its related region of class II MHC antigen on sperm played an important role in the recognition between sperm and egg in fertilization.

Animals↗
PubMed1989

Acetylcholine causes nicotinic depolarization in rat dorsal motor nucleus of the vagus, in vitro.

Action of acetylcholine (ACh) on the electrophysiologically identified preganglionic neurons in the dorsal motor nucleus of the vagus (DMV) were investigated in slice preparations of rat medulla oblongata by using conventional intracellular recording technique. Applications of ACh to the DMV neurons resulted in a marked depolarization, which was not abolished in Ca-free superfusing solution, indicating the direct action of ACh on the cells. This depolarization was associated with an increase in membrane conductance and markedly reduced in the Na-free superfusate. The extrapolated reversal potential of ACh response was about -35 mV, indicating that both sodium and potassium conductances are likely responsible for the ACh depolarization. Application of nicotine caused similar depolarization to that of ACh, while muscarinic agonists (muscarine and oxotremorine) did not have any effect. Additions of the nicotinic antagonists hexamethonium and D-tubocurarine to the bathing solution reversibly attenuated the ACh-induced depolarization, while the muscarinic antagonist atropine did not have any effect. The nicotinic properties of ACh action in the DMV neurons presented here form a striking contrast to previous autoradiographic findings. Though endogenous cholinergic inputs to the DMV have not been identified, ACh may have a strong influence on vagal control by depolarization through nicotinic receptors of the DMV preganglionic neurons.

Acetylcholine↗