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Biomedical subjects

M Kuno

Publications and source records attributed to M Kuno.

At least 37 records · Page 2Linked to original sources
PubMed1997

Epidermal growth factor binding sites in the mouse exocrine and endocrine pancreas shown by in vivo quantitative microautoradiography and confocal laser scanning microscopy.

Microautoradiography at 3, 6 and 15 min after intravenous injection of 125I-EGF was used to investigate the distribution of epidermal growth factor (EGF) binding sites in the pancreas of normal male mice. The autoradiographs were observed by confocal laser microscopy, which allows the quantification of silver grains. The results demonstrated that both endocrine and exocrine pancreatic cells exhibited substantial specific binding of 125I-EGF. The highest level of EGF binding was found in the duct cells of the exocrine pancreas followed by the acinar cells. The cells of the islets of Langerhans also showed substantial specific binding of 125I-EGF though the binding level was lower than that of the exocrine pancreas. In the control experiments, mice were injected with 125I-EGF and various amounts of unlabeled EGF.

Animals↗
PubMed1997

Dual mode of N-methyl-D-aspartate-induced neuronal death in hippocampal slice cultures in relation to N-methyl-D-aspartate receptor properties.

Hippocampal slices prepared from neonatal rats were cultured for several weeks, and excitotoxicity induced in CA1 pyramidal neurons by N-methyl-D-aspartate was evaluated at different culture stages. CA1 neurons cultured for one week exhibited cell death predominantly within 1-3 h after a 15-min N-methyl-D-aspartate insult (early death), whereas those cultured for three weeks showed cell death mainly a few hours to 24 h after the insult (delayed death). CA1 neurons cultured for two weeks were in a transitional state, expressing only weak early and delayed forms of cell death in response to N-methyl-D-aspartate. The N-methyl-D-aspartate-induced early cell death observed in the one-week group depended on external Cl- but did not require external Ca2+; rather, early cell death was enhanced in Ca2+-free solution. This early cell death was accompanied by cell swelling, but cell swelling alone produced by osmotic changes failed to induce cell death. There was no evidence that CA1 neurons in the one-week group were more responsive to N-methyl-D-aspartate than those in the two other groups. Delayed cell death examined in the three-week group depended on external Ca2+ but was independent of Cl-. The density of N-methyl-D-aspartate-induced whole-cell currents recorded from CA1 neurons in Mg2+-free solution remained unchanged during three weeks of culture. However, the N-methyl-D-aspartate receptor channel in the three-week group was more resistant to Mg2+ block than that in the one- or two-week group. The incidence of N-methyl-D-aspartate-induced delayed cell death was higher in the three-week group than in the two-week group in normal solution but not in Mg2+-free solution. Thus, Mg2+ block-resistant properties of the N-methyl-D-aspartate receptor channel acquired during prolonged culture may account for the high incidence of N-methyl-D-aspartate-induced delayed cell death in the three-week group. However, the N-methyl-D-aspartate receptor subunits expressed in the CA1 subfield did not show any feature specific to the three-week group. These results show that two mechanistically distinct modes of N-methyl-D-aspartate-induced neuronal death are manifested differentially at different culture stages, depending on the intrinsic neuron properties (i.e. early cell death) and on the properties or the responsiveness of the N-methyl-D-aspartate receptor (i.e. delayed cell death).

Animals↗
PubMed1997

The optimum dose of gamma radiation-heavy doses to low wear polyethylene in total hip prostheses.

Wear volume, surface area and coefficient of friction of UHMWPE cup crosslinked with gamma radiation of 0, 50, 75, 100, 125, 150 and 200 Mrad sliding against an alumina ball were measured using a sphere-on-flat reciprocating type tribology testing machine. The effects of gamma radiation were scarcely observed in coefficient of friction. The coefficient of friction under lubricated (distilled water) and non-lubricated testing conditions was 0.08 to 0.12 and 0.20 to 0.25, respectively. The wear volume of UHMWPE with radiation of 50 Mrad, 75 to 150 Mrad, and 200 Mrad was 70 to 80%, 18 to 25%, and 12 to 15%, respectively, in comparison to non-irradiated specimens. Elongation and tensile strength of UHMWPE with radiation of 100 Mrad decreased to 6%, and 50% of that without radiation, respectively. The hardness increased with increase of the radiation dose. From several kinds of tribological findings, mechanical strength tests, and studies of long-term clinical findings, it is concluded that approximately 200 Mrad is the optimum dose of gamma radiation for clinical use in total hip prostheses.

Journal Article↗
PubMed1997

A highly temperature-sensitive proton current in mouse bone marrow-derived mast cells.

Proton (H+) conductive pathways are suggested to play roles in the regulation of intracellular pH. We characterized temperature-sensitive whole cell currents in mouse bone marrow-derived mast cells (BMMC), immature proliferating mast cells generated by in vitro culture. Heating from 24 to 36 degrees C reversibly and repeatedly activated a voltage-dependent outward conductance with Q10 of 9.9 +/- 3.1 (mean +/- SD) (n = 6). Either a decrease in intracellular pH or an increase in extracellular pH enhanced the amplitude and shifted the activation voltage to more negative potentials. With acidic intracellular solutions (pH 5.5), the outward current was detected in some cells at 24 degrees C and Q10 was 6.0 +/- 2.6 (n = 9). The reversal potential was unaffected by changes in concentrations of major ionic constituents (K+, Cl-, and Na+), but depended on the pH gradient, suggesting that H+ (equivalents) is a major ion species carrying the current. The H+ current was featured by slow activation kinetics upon membrane depolarization, and the activation time course was accelerated by increases in depolarization, elevating temperature and extracellular alkalization. The current was recorded even when ATP was removed from the intracellular solution, but the mean amplitude was smaller than that in the presence of ATP. The H+ current was reversibly inhibited by Zn2+ but not by bafilomycin A1, an inhibitor for a vacuolar type H(+)-ATPase. Macroscopic measurements of pH using a fluorescent dye (BCECF) revealed that a rapid recovery of intracellular pH from acid-load was attenuated by lowering temperature, addition of Zn2+, and depletion of extracellular K+, but not by bafilomycin A1. These results suggest that the H+ conductive pathway contributes to intracellular pH homeostasis of BMMC and that the high activation energy may be involved in enhancement of the H+ conductance.

Animals↗
PubMed1996

Anthropometric variables and muscle properties of Japanese female ballet dancers.

Physiological characteristics of japanese female classical ballet dancers were investigated in comparison with sedentary women of similar age (non-dancers). Subjects were 20 professional female ballet dancers with a mean age of 26.5 +/- 4.4 years (mean +/- SD) and 66 sedentary women with a mean age of 23.7 +/- 3.6 years. Dancers had been trained in ballet classes for 20.4 +/- 2.4 years and had no experience of regular exercises except dance training. Body mass and % body fat measured by under-water weighing method were significantly smaller in the dancers than in the non-dancers. For all extremities, percentage of the muscle in total cross-sectional area calculated by ultra sound apparatus was significantly larger and percentage of the adipose tissue in total cross-sectional area was significantly smaller in the dancers. The maximal isometric and isokinetic force of knee flexors and the maximal isometric force of dorsi flexors (MVC force) were significantly larger in the dancers when the values were divided by body mass of each subject. During 50 repetitions of maximal plantar flexion, the isometric force of the dancers was significantly larger in all repetitions except first and second reps, though no significant difference was observed in MVC force during plantar flexion. It was suggested that the significant differences between the dancers and the non-dancers in some physiological variables might be attributed to the characteristics of dance movements/training.

Adult↗
PubMed1996

Histiocytic cytophagic panniculitis which developed during interferon-alpha therapy.

A 59-year-old woman developed edema of the face and eyelids during interferon (IFN)-alpha-2b therapy for chronic hepatitis C with a cumulative dose of 6 million x 47 units. Despite cessation of the therapy, the edema progressed and was followed by exophthalmos, pyrexia, liver dysfunction, pancytopenia, and disseminated intravascular coagulation. Two months after initial presentation, she died of hemorrhagic shock and was diagnosed with histiocytic cytophagic panniculitis at autopsy. This may be a hitherto unrecognized adverse effect of therapeutic IFN alpha.

Antiviral Agents↗
PubMed1995

Assessment of autonomic function in myotonic dystrophy by spectral analysis of heart-rate variability.

We analyzed by means of autoregressive spectral analysis the spontaneous beat-to-beat heart-rate variability (HRV) of 10 myotonic dystrophy (MD) patients (4 men and 6 women, aged 37-53 years) and 10 age- and sex-matched healthy, sedentary humans (control) at rest in the supine position. All MD patients had no cardiac conduction disturbances (i.e., atrioventricular or intraventricular conduction defects) on 12-lead electrocardiogram and were able to walk and perform daily activities. In the MD group, the total power, the power of the low-frequency component (a marker of sympathetic and vagal modulation of heart rate) and that of the high-frequency component (a marker of vagal modulation of heart rate) were smaller than those in the control group (P < 0.01, P < 0.05 and P < 0.05, respectively). The results of this study suggest that the cardiovascular autonomic nervous system contributing to the HRV may be disturbed even in the MD patients who can walk and perform daily activities. Therefore, one must give careful consideration to the cardiovascular autonomic dysfunction, as well as the cardiac conduction disturbance in the MD patients.

Adult↗
PubMed1995

Assessment of autonomic function in traumatic quadriplegic and paraplegic patients by spectral analysis of heart rate variability.

We analyzed by means of autoregressive spectral analysis the spontaneous beat-to-beat heart rate variability (HRV) of quadriplegic and paraplegic male subjects at rest in the supine position. In agreement with our previous study, in nine of 15 quadriplegic patients only the high-frequency (HF: center frequency = respiratory frequency) component (a marker of vagal modulation of heart rate) was observed. In contrast, in six of the quadriplegic patients both the HF component and the low-frequency (LF: center frequency at approx. 0.1 Hz, 0.03-0.15 Hz in this study) component (a marker of sympathetic and vagal modulation of heart rate) were observed. However, in six quadriplegic patients who presented the LF component, (i) the center frequency of the LF component was lower than that in 10 healthy, sedentary, age-matched males (control I) (P < 0.01), (ii) the power of the HF component was smaller than that in the control-I group (P < 0.01) and (iii) the LF/HF power ratio (an index of sympathovagal balance) was larger than that in the control-I group (P < 0.05). On the other hand, in nine paraplegic patients with an intact 1st-4th thoracic spinal cord, from which the cardiac sympathetic nerves originate, the total power, the power of the LF component and that of the HF component were smaller than those in nine healthy, sedentary, age-matched males (control II) (P < 0.05, P < 0.01 and P < 0.01, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Potentiation of excitatory postsynaptic potentials by a metabotropic glutamate receptor agonist (1S,3R-ACPD) in frog spinal motoneurons.

We conducted intracellular recordings of lumbar motoneurons in the arterially-perfused frog spinal cord and investigated the effects of a metabotropic glutamate receptor agonist, (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD), on excitatory postsynaptic potentials evoked by stimulation of the descending lateral column fibers (LC-EPSPs). In the absence of Mg2+, ACPD reversibly potentiated the amplitude of monosynaptic LC-EPSPs by more than 15% in 15 of 19 cells with 5 microM ACPD and in 7 of 12 cells with 0.5 microM ACPD. The EPSP amplitudes with 5 and 0.5 microM ACPD were 142 +/- 10% (mean +/- S.E.M., n = 19) and 130 +/- 13% (n = 12) of the controls. The potentiation was seen without a decrease in the input conductance. Glutamate-induced depolarizations in the absence and the presence of 0.5 microM ACPD were not significantly different in cells perfused with the low Ca(2+)-high Mg2+ solution which eliminated chemical transmission. Paired pulse facilitation of LC-EPSPs was reversibly decreased in association with the potentiation. ACPD-induced potentiation of monosynaptic LC-EPSPs was seen in 5 of 6 cells in the presence of D-(-)-2-amino-5-phosphonopentanoic acid (D-AP5), an NMDA receptor antagonist. ACPD occasionally activated polysynaptic components of LC-EPSPs which were mediated mainly via NMDA receptors. On the other hand, ACPD-induced potentiation of EPSPs was inhibited by extracellular Mg2+.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

A heterogeneous electrophysiological profile of bone marrow-derived mast cells.

Electrophysiological properties of mouse bone marrow-derived mast cells (BMMC) were studied under the whole-cell clamp configuration. About one third of the cells were quiescent, but others expressed either inward or outward currents. Inwardly rectifying (IR) currents were predominant in 14% of the cells, and outwardly rectifying (OR) currents in 24%. The rest (22%) of the cells exhibited both inward and outward currents. The IR currents were eliminated by 1 mM Ba2+, and were partially inhibited by 100 microM quinidine. The reversal potential was dependent on extracellular K+, thereby indicating that K+ mediated the IR currents. The negative conductance region was seen at potentials positive to EK. The OR currents did not apparently depend on the extracellular K+ concentration, but were reduced by lowering the extracellular Cl- concentration. The OR currents were partially blocked by 1 mM Ba2+, and were further blocked by a Cl- channel blocker, 4,4'-diisothiocyano-2,2'-stilbenedisulfonate (DIDS). In addition, the reversal potential of the OR currents was positively shifted by decreasing the ratio of external and internal Cl- concentrations, suggesting that Cl- was a major ion carrier. In cells exhibiting IR currents, the membrane potential varied among cells and tended to depolarize by elevating the external K+ concentration. In cells with OR currents, the resting potential was hyperpolarized in association with an increase in conductance.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

IP3-activated calcium-permeable channels in the inside-out patches of cultured cerebellar Purkinje cells.

Inositol-1,4,5-trisphosphate (IP3)-activated calcium-permeable channels were recorded from inside-out patches of cultured cerebellar Purkinje cells. When 2-5 microM of IP3 was applied to the internal surface of the inside-out patches, inward Ba2+ currents were activated within 10 sec following the application in 11 out of 24 patches. In the presence of heparin (100 micrograms/ml), activation of Ba2+ currents by IP3 was inhibited. Unitary currents with different amplitudes and kinetics were observed; small and large unitary currents, and rapid fluctuations with various amplitudes. The small unitary currents (single channel conductance; 5.6 pS) were most frequent. Addition of inositol 1,3,4-trisphosphate (2-5 microM) slightly activated Ba2+ currents in 2 out of 10 patches, but the amount of the increment was much smaller than that produced by IP3. These results suggest a possibility that IP3 directly activates Ca(2+)-permeable channels in the plasma membrane of cerebellar Purkinje cells.

Animals↗
PubMed1993

Messenger RNAs from chick muscle encode a motoneuronal survival-promoting factor.

The survival of motoneurons requires a trophic factor derived from the target muscles, but the nature of this trophic factor is not known. We examined whether skeletal muscle expresses mRNAs encoding survival-promoting factors for motoneurons. Messenger RNAs were purified from hindlimbs of chick embryos and injected into Xenopus oocytes for translation. The media conditioned by incubation of the injected oocytes were applied to chick embryos during the natural cell death period of lumbar motoneurons. This procedure significantly reduced the magnitude of natural motoneuronal death. The conditioned media also promoted the survival of motoneurons cultured from chick embryos.

Animals↗
PubMed1993

Enhancement of monosynaptic excitatory postsynaptic potentials by glutamate in frog spinal motoneurons.

We analyzed glutamate-induced enhancement of the amplitude of monosynaptic excitatory postsynaptic potentials evoked by stimulation of the lateral column fibers (LC-EPSPs) on lumbar motoneurons in the frog spinal cord. Low concentrations (0.1-0.3 mM) of glutamate, which produced small depolarization, often enhanced EPSP associated with inhibition of a paired pulse facilitation and increased occurrence of spontaneous EPSPs. With 1 mM glutamate, transient enhancement of EPSP was seen in some cells during the early phase or prior to large depolarization, even when input conductance was increased. Transient or sustained enhancement of EPSP was occasionally seen with N-methyl-D-aspartate, kainate and quisqualate, but not with L-2-amino-4-phosphonobutyrate. The results suggest that glutamate enhanced release of excitatory transmitters at low concentrations that apparently did not affect the postsynaptic membrane.

Animals↗
PubMed1993

Electrophysiological properties of axotomized facial motoneurones that are destined to die in neonatal rats.

1. Rat facial motoneurones axotomized on the day after birth were examined morphologically, and their electrical properties were characterized using the whole-cell recording technique in thin slices of the brainstem. 2. About 40% of facial motoneurones were lost within 4 days of axotomy, and only about 20% of the neurones survived 9 days after axotomy. 3. The surviving facial motoneurones examined 4 or 6 days after axotomy were reduced in size, and this was associated with a decrease in their input capacitance. 4. Both the resting potential and the amplitude of action potentials remained unchanged in axotomized facial motoneurones. 5. Facial motoneurones examined 4 or 6 days after axotomy showed an increase in the spike duration. When the preparation was superfused with a Ca(2+)-free solution, the spike duration of axotomized facial motoneurones was shortened, whereas the spike duration of control facial motoneurones was prolonged. 6. The voltage-gated transient K+ current (IA) density was significantly reduced in axotomized motoneurones, whereas the Ca(2+)-dependent transient K+ current (IK, Ca) density was not affected. 7. Voltage-gated Ca2+ currents in facial motoneurones showed inactivation, displaying an initial transient phase followed by a sustained phase. The rate of inactivation of Ca2+ currents was significantly faster in axotomized neurones than in control neurones. 8. A small subpopulation of facial motoneurones examined 4 or 6 days after axotomy had a disproportionately high input resistance and a significantly longer after-hyperpolarization. The probability of this occurring was correlated with the time course of cell death induced by axotomy. 9. It is concluded that facial motoneurones axotomized in neonatal rats comprise two subpopulations. The subpopulation characterized by a markedly high input resistance is suggested to represent the neurones which are at the 'prelethal' stage or in the process of cell death.

Action Potentials↗
PubMed1993

Inhibitors of the arachidonic acid cascade dissociate 48/80-induced Ca2+ influx and Ca2+ release in mast cells.

Effects of inhibitors of the arachidonic acid cascade on Ca2+ release from intracellular stores and Ca2+ influx through the plasma membrane during stimulus-secretion coupling were examined using rat peritoneal mast cells loaded with fura-2. Compound 48/80 (48/80) was used as a secretagogue. A phospholipase inhibitor, p-bromophenacyl bromide (PBPB), or a lipoxygenase inhibitor, nordihydroguaiaretic acid (NDGA), inhibited the 48/80 (1 microgram/ml)-induced release of histamine, Ca2+, and Mn2+ influxes, but the cyclooxygenase inhibitor, indomethacin (approximately 50 microM), inhibited neither Ca2+ nor Mn2+ influxes. The Ca2+ release induced by 1 microgram/ml of 48/80 was little inhibited by PBPB, NDGA, or indomethacin. The Ca2+ release was activated and saturated with lower concentrations of 48/80 than was the Ca2+ influx. The percent inhibition of the Ca2+ release by 25 microM PBPB was increased by lowering the concentration of 48/80, but NDGA (10 microM) did not inhibit the Ca2+ release induced by low concentrations of 48/80 (0.03-0.1 microgram/ml). These results suggest that activation of the Ca2+ release and the Ca2+ influx were differently regulated and that full activation of Ca2+ influx needs the arachidonic acid cascade produced by higher concentrations of 48/80 than does the Ca2+ release. Lipoxygenase metabolites of arachidonic acid are potential modulators of the Ca2+ influx.

Acetophenones↗