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Biomedical subjects

A Fukuda

Publications and source records attributed to A Fukuda.

At least 163 records · Page 9Linked to original sources
PubMed1989

Developmentally different onset of alpha 1- and alpha 2-adrenergic responses in the neonatal rat dorsal motor nucleus of the vagus in vitro.

Development of noradrenergic responses in the rat dorsal motor nucleus of the vagus (DMV) from postnatal days 0 to 22 was studied by a conventional microelectrode technique using brain slice preparations. Between postnatal days 0 and 6, noradrenaline (NA) caused only alpha 1-adrenoceptor-mediated depolarizations. By postnatal day 14, alpha 2-adrenoceptor-mediated hyperpolarization appeared. During the next postnatal week, the response pattern to NA became similar to that in adults, including both alpha 1- and alpha 2-adrenergic responses. These results suggest that alpha 2-adrenergic responses in DMV neurons are absent at birth but develop rapidly in the 3 weeks after birth. Furthermore, alpha 1-adrenoceptors have already been functioning in the fetal period.

Action Potentials↗
PubMed1989

Chemical changes of organic compounds in chlorinated water. XVI. Gas chromatographic-mass spectrometric studies of reactions of tricyclic aromatic hydrocarbons with hypochlorite in dilute aqueous solution.

The products of aqueous chlorination reactions of tricyclic aromatic hydrocarbons (fluorene, carbazole, dibenzofuran, anthracene, phenanthrene and some methyl derivatives) with hypochlorite have been determined by gas chromatography-mass spectrometry. They included chloro-substituted, oxygenated (quinones) and hydroxylated (phenols) compounds, and products of addition which were readily formed at ambient temperature. The extent of the reactions was shown to depend on the chlorine dose, the solution pH, the initial concentrations of both compounds and the structures. Monochlorinated compounds and quinones were shown to be present in chlorinated water under the conditions utilized for water treatment.

Chlorine↗
PubMed1989

Effects of prolactin during preincubation of mouse spermatozoa on fertilizing capacity in vitro.

In the present study, some beneficial effects of mouse prolactin (PRL) on spermatozoa were demonstrated in mice. The motility rate of spermatozoa is well maintained during incubation in modified Krebs-Ringer bicarbonate solution (mKRB) containing PRL (10 or 100 ng/ml) for up to 120 min. When spermatozoa that had been preincubated in the same PRL-containing mKRB were incubated with oocytes in mKRB, significantly more spermatozoa attached to the zona pellucida of each oocyte. When spermatozoa that had been preincubated in mKRB with PRL (50 and 100 ng/ml) for only 15 or 30 min were used for in vitro fertilization (IVF), significantly higher fertilization rates were yielded by those spermatozoa than by control spermatozoa preincubated without PRL for the same periods. The prolongation of the preincubation period did not result in increased fertilization rates. Thus, PRL demonstrated biological effects on spermatozoa by shortening the optimal preincubation period for spermatozoa to acquire capacitation and by maintaining their motility and ability of the attachment to the oocyte during IVF. The results are relevant to clinical application of PRL for infertile patients with oligozoospermia or asthenozoospermia.

Animals↗
PubMed1989

Effects of the supernatants of mixed lymphocyte cultures and decidual cell line cultures on mouse embryo development in vitro.

The effects of supernatants of human mixed lymphocyte cultures (MLC), with or without human decidual cell line culture extract (decidual factor; DCF), on F1-hybrid mouse embryo development in vitro from the two-cell stage were investigated. The development of mouse embryos from the two-cell stage through the expanded blastocyst stage was facilitated significantly by the addition of supernatants of not only MLC, but also MLC supplemented with DCF (MLCDCF) to the culture medium. Moreover, the supernatant of MLCDCF accelerated the attachment of the hatched blastocyst to the culture dish substratum and the outgrowth of trophoblasts in vitro. The findings indicate that the supernatant of MLCDCF facilitates the in vitro activity of mouse embryos for implantation and that the maternal immune response, along with the decidual tissue, contributes to the implantation processes.

Animals↗
PubMed1989

Orientation of bone mineral and its role in the anisotropic mechanical properties of bone--transverse anisotropy.

An orientation of hydroxyapatite (HAP) crystals in bovine femur mineral was investigated by means of X-ray pole figure analysis (XPFA). It was found that the c-axis of HAP generally orients parallel to the longitudinal axis of bone (bone axis) and a significant amount of c-axis was oriented in other directions, in particular, perpendicular to the bone axis. Comparing these results with those of the small angle X-ray scattering (SAXS) investigation by Matsushima et al. (Jap. J. appl. Phys. 21, 186-189, 1982) at least two types of morphology of bone mineral were found; rod like bone mineral having the c-axis of HAP crystal parallel to the longitudinal axis of the rod and that having the c-axis not parallel, in a particular case, perpendicular to its longitudinal axis. Transverse anisotropy in mechanical properties of bone was reproduced by the estimation of Young's moduli by using the structural results mainly from XPFA. It is concluded that the anisotropy in mechanical properties of bone is well explained by taking account of the non-longitudinal (off-bone) axial distribution of orientation of bone mineral.

Animals↗
PubMed1989

Mechanical properties of hydroxyapatite-reinforced gelatin as a model system of bone.

The elastic Young's modulus of hydroxyapatite-reinforced gelatin as a mechanical model system of bone was measured as a function of the volume fraction of hydroxyapatite, phi h. Initially, the Young's modulus gradually increased with an increase in phi h and then increased rapidly in the vicinity of phi h approximately 0.2. The phi h dependence of the Young's modulus was analysed by means of the theory of composite materials. It was found that with the increase in phi h the initial uniform stress deformation mode of the sample changed to the uniform strain deformation mode. The non-linear character in phi h dependence of the Young's modulus of this system was considered to reproduce well the novel behaviour of the mechanical properties of bone as a function of the mineral fraction. The situation was considered to be similar to a percolation problem. A preliminary analysis revealed that the critical exponent about the viscosity of the system accorded with the theoretically expected value. The result may present the evidence that the discontinuous point in mechanical properties of bone would be originated from an interaction such as a percolation of mineral particles on a matrix protein.

Biomechanical Phenomena↗
PubMed1989

[Isolation of rod- and cone-mediated c-waves in the chicken ERG using monochromatic stimuli].

Cone-mediated c-wave has recently been recorded from the cone dominant retina, while ERG c-wave had been considered to be mainly a rod-mediated response. However, only a few experiments have been conducted to isolate both rod- and cone-mediated c-waves from same experimental materials. In the present experiment, chicken eyes were used as the cone-dominant retina to isolate rod- and cone-mediated c-waves using monochromatic stimuli. Of monochromatic light at 20nm intervals between 460 and 620nm was adjusted to yield equal energy. In order to obtain criterion voltages of 50 and 100 microV of the c-wave amplitude in dark adaptation and 50 microV in light adaptation, stimulus intensities of the monochromatic lights were attenuated by neutral density filters from a maximal intensity of 7.7 microW/cm2 at the corneal surface. The duration of the stimulus light was 0.15, 5 or 10 seconds, and the stimulus interval was 90 seconds. In dark adaptation, the spectral characteristic of the c-wave at 50 microV criterion voltage was similar to the absorption curve of rhodopsin in rod cells and at 100 microV criterion voltage to a photopic CIE curve. In light adaptation, the spectral characteristic of the c-wave at 50 microV criterion voltage closely resemble that of the photopic CIE curve; these findings indicated that a Purkinje shift was observed in the attitude of the c-wave in the light and dark adaptation. The peak latency of the c-wave in dark adaptation was prolonged together with an increase of the c-wave amplitude, but tended to become shorter by stimuli longer than 580nm. On the other hand, in the light adaptation, the peak latency of the c-wave was evidently shorter than that in the dark adaptation and was constant throughout all the monochromatic stimuli. Based upon the above results, it was concluded that both rod- and cone-mediated c-waves could be isolated from the chicken retina by using the monochromatic stimuli.

Animals↗
PubMed1988

Direct effects of 3,4-dihydroxybutanoic acid gamma-lactone and 2,4,5-trihydroxypentanoic acid gamma-lactone on lateral and ventromedial hypothalamic neurons.

The mechanism of central actions of endogenous sugar acids, 3,4-dihydroxybutanoic acid gamma-lactone (3,4-DB) and 2,4,5-trihydroxypentanoic acid gamma-lactone (2,4,5-TP) which have been newly identified as satiety and hunger substances respectively, was investigated. Intracellular recordings were made from neurons in the lateral hypothalamic area (LHA) of rats and ventromedial hypothalamic nucleus (VMH) of guinea pigs, brain areas referred to as feeding and satiety centers, respectively. The LHA neurons hyperpolarized by 3,4-DB show no change in membrane input resistance while the depolarized VMH neurons are associated with an increase in membrane resistance. The mechanisms related to the action of 3,4-DB on these hypothalamic neurons are similar to those in case of glucose on the glucose-sensitive neuron in the LHA and the glucoreceptor neuron in the VMH. 2,4,5-TP depolarized LHA neurons but hyperpolarized VMH neurons with a decrease in the membrane resistance. Our findings indicate that 3,4-DB and 2,4,5-TP have reciprocal effects on each LHA and VMH neurons, with regard to neuronal excitability.

Action Potentials↗
PubMed1988

Influences of prolactin upon spermatogenesis and spermatozoa during in vitro fertilization in mice.

Hyperprolactinemia, induced by pituitary isografts for 20 weeks in male mice and confirmed by radioimmunoassay using anti-mouse prolactin serum, did not impair spermatogenesis in the testis and maturing processes of spermatozoa in the epididymis. Incubation of freshly obtained epididymal spermatozoa for 90 min in culture media containing various levels of mouse prolactin did not yield any adverse effects on percentage motility rates of epididymal spermatozoa. When the level of mouse prolactin in the preincubation medium for epididymal spermatozoa was 100 ng/ml, the rate of fertilization by these preincubated spermatozoa in the subsequent in vitro fertilization experiment was significantly lowered compared with that observed in controls. However, when the level of prolactin in preincubation media was 10 ng/ml, no significant reduction in the rate of fertilization occurred. The present experiments seem to indicate the existence of some differences in the effects of prolactin on male germ cells until they reach the tail of the epididymis and on the processes of capacitation and/or fertilization by epididymal spermatozoa after they leave the epididymis.

Animals↗
PubMed1988

Blocking effect of sperm immobilizing antibodies on sperm penetration of human zonae pellucidae.

To investigate the mechanism of the blocking effect of sperm immobilizing antibodies on human fertilization, an in vitro zona penetration test was carried out using media containing the IgG fraction extracted from sperm immobilizing antibody-negative or -positive serum. The sperm penetration rate of the test was 100% (6/6) when spermatozoa were treated with the IgG fraction derived from sperm immobilizing antibody-negative serum, whereas it was only 17% (1/6) when spermatozoa were treated with the IgG fraction derived from sperm immobilizing antibody-positive serum. Electron microscopic observation of the sperm immobilizing antibody-negative and -positive serum-treated spermatozoa showed that the number of acrosome-reacted spermatozoa was significantly greater in the sperm immobilizing antibody-negative serum than in the antibody-positive serum. Therefore, it appears that one of the blocking mechanisms of the spermatozoal penetration of the zona pellucida by sperm immobilizing antibodies may be due to inhibition of the acrosome reaction in the spermatozoa.

Acrosome↗
PubMed1988

Effects of prolactin on gametes and zygotes during in vitro fertilization in mice.

Hyperprolactinemia is one of the major causative factors of infertility. However, the effect of prolactin on gametes during in vitro fertilization has not been elucidated. In the present study, the effects of mouse prolactin on the motility of spermatozoa, in vitro fertilization, and in vitro development of the zygote were investigated in mice using media containing three different concentrations (10, 50, and 100 ng/ml) of mouse prolactin. The development of unfertilized and fertilized oocytes (zygotes) was not affected in vitro by prolactin regardless of the amount of prolactin added to culture media. However, the fertilizing capacity of the spermatozoa was suppressed when they were preincubated for 90 min in culture media containing prolactin at concentrations of 50 and 100 ng/ml. The motility of spermatozoa was not affected by prolactin regardless of the concentration of prolactin used for preincubation. The present study indicates that prolactin may have some effects on the capacitation process of spermatozoa in vitro. This result should be taken into consideration in in vitro fertilization and embryo transfer procedures in humans.

Animals↗
PubMed1988

Effects of sulphated cholecystokinin octapeptide (CCK-8) on the dorsal motor nucleus of the vagus.

Sulphated cholecystokinin octapeptide (CCK-8) was applied by superfusion (2.1 x 10(-7) to 4.2 x 10(-6) M) to neurons of the dorsal motor nucleus of the vagus (DMV) in slice preparations of the rat medulla oblongata. Intracellular recordings show 23 of 54 (43%) neurons to be depolarized and the depolarization to be associated with an increase in membrane input resistance; 6 of 54 (11%) neurons were hyperpolarized and the hyperpolarization was associated with a decrease in membrane input resistance. Both effects were dose-dependent, reversible and persisted after blockade of synaptic transmission by Ca2+ free/high Mg2+ solution. On the other hand, nonsulphated CCK-8, a nonactive analogue of CCK-8, had no effect. These data show that vagal neurons in the DMV have receptors for CCK-8 and that CCK-8 may modulate vagal output mainly by increasing neuronal excitability.

Action Potentials↗
PubMed1988

Internal and external information processing by lateral hypothalamic glucose-sensitive and insensitive neurons during bar press feeding in the monkey.

Single neuron activities in the lateral hypothalamic area (LHA) were recorded during bar press feeding task in the monkey. First registered neurons were sorted into 2 groups, glucose-sensitive (GS) and glucose-insensitive (GIS) neurons, depending on their glucose sensitivity. The firing variations to feeding, electrophoretically applied catecholamines and opiate, and to odor and taste stimuli were investigated. GS neurons responded to dopamine, noradrenaline and morphine more often than GIS neurons. In feeding task GS neurons responded during bar press (BP) and reward (RW) periods with long-lasting inhibition of firing and at cue tone (CT) with transient inhibition, while GIS neurons responded during BP and RW periods mainly with excitation and at cue light (CL) with excitation. A majority of GS neurons responded to both odor and taste stimuli more often than GIS neurons. Data suggest that these two kinds of neurons in the LHA may be involved in different functional aspects of feeding: GS neurons, mainly in internal information processing and reward mechanism, and GIS neurons, in external information processing and motor aspects.

Action Potentials↗
PubMed1988

A novel endogenous sugar acid depolarizes ventromedial hypothalamic neurons in vitro.

2-Buten-4-olide (2-B-4-O) has been identified in the serum of fasted rats and proved to act as a feeding suppressant. The effect of 2-B-4-O on neurons in the ventromedial hypothalamic (VMH) nucleus was investigated with intracellular recordings in brain slice preparations of rats. 2-B-4-O, applied by perfusion (0.1-10 mM) or drops (50-100 mM), dose dependently depolarized 30% of the VMH neurons tested. The depolarization by 2-B-4-O application persisted after complete elimination of synaptic inputs during perfusion with Ca2+-free/high-Mg2+ solution. The depolarization, accompanied by a decrease in membrane conductance, reversed polarity around -95 mV and was dependent on extracellular K+ concentration. The VMH neurons depolarized by 2-B-4-O had some specific electrophysiological properties corresponding with those of glucoreceptor neurons. The results suggest that 2-B-4-O directly excites VMH neurons, presumed to be glucoreceptor neurons, by decreasing K+ conductance, and this effect may participate in the feeding suppressive action of 2-B-4-O.

4-Butyrolactone↗