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Biomedical subjects

H Tokuno

Publications and source records attributed to H Tokuno.

At least 55 records · Page 3Linked to original sources
PubMed1994

Effects of intracellular pH on calcium currents and intracellular calcium ions in the smooth muscle of rabbit portal vein.

In smooth muscle cells freshly dispersed from the rabbit portal vein, effects of intracellular pH (pHi) on Ca2+ channel currents were studied with the whole-cell clamp method using nystatin in the pipette. pHi was modified with ammonium chloride (NH4Cl) and propionate. Changes in intracellular Ca2+ concentration ([Ca2+]i) and pHi were also measured with the fluorescent indicator fura-2 and a pH-sensitive dye, respectively, together with the mechanical response in intact tissues. Intracellular alkalinization caused by an application of NH4Cl (20 mM) markedly potentiated and acidification caused by propionate (20 mM) inhibited inward Ca2+ channel currents, without much change in the kinetics. Tension development induced by 60 mM K- was inhibited by NH4Cl (20 mM) and potentiated by propionate (20 mM), whereas the peak [Ca2+]i level reached during K+ contracture was reduced in the presence of NH4Cl and increased in the presence of propionate. It was concluded that the modification of Ca2+ channel currents caused by pHi is not directly related to the effects of pHi on the mechanical response to excess K+. The direct effects of pHi on [Ca2+]i and on contractile machinery are considered to be mainly responsible for the mechanical effect of pHi.

Ammonium Chloride↗
PubMed1993

Developmentally transient expression of acetylcholinesterase within cortical pyramidal neurons of the rat brain.

Using a histochemical method for the visualization of cholinesterase activity in neurons, we have observed developmentally transient expression of acetylcholinesterase (AChE) in cortical pyramidal neurons of the rat brain. Depending on the extent of the deposition of AChE reaction product, several types of cortical neurons could be visualized. We designated neurons with moderate-to-high staining intensity as AChEH and neurons with relatively lower staining intensity as AChEL. At birth (P0), very little AChE activity was found within cortical neurons. Between P1-P4, there was a gradual emergence of AChE-stained cortical neurons. At this stage, the majority of these neurons were of the AChEL type. At P5-P7 we observed an abrupt increase in AChE-stained cortical neurons. The number and the staining intensity of these neurons was at a peak at P8-P10. At this age range, the majority of these neurons were of the AChEH variety and displayed morphological characteristics of cortical pyramidal neurons. At P11-P15, there was an abrupt decrease in the number of AChEH neurons. After P15, the density and staining intensity of cortical AChE-positive (cholinergic) axons gradually increased. Nevertheless, AChEL pyramidal neurons were detected through these fibers up to P21. At P21, a dense plexus of AChE-positive axons was observed in all cortical areas while very little AChE reaction product was visible in pyramidal neurons, and this pattern continued into adult life. When the adult cortex was denervated from its AChE-positive axons by lesions of the nucleus basalis magnocellularis, many AChEL pyramidal neurons were uncovered.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholinesterase↗
PubMed1993

Input organization of distal and proximal forelimb areas in the monkey primary motor cortex: a retrograde double labeling study.

The present double-labeling study was designed to demonstrate the morphological framework for motor control in coordinated distal and proximal forelimb movements, which may partly, at least, depend on corticocortical and thalamocortical inputs to the forelimb area in the primary motor cortex. After intracortical microstimulation mapping of the forelimb area in the primary motor cortex of four macaque monkeys, a retrograde tracing study with fluorescent dyes was attempted to label simultaneously neurons in cortical and subcortical sites projecting to the distal forelimb representation area and those projecting to the proximal representation area of the primary motor cortex. Neurons projecting to distal and proximal forelimb parts of the primary motor cortex were largely separate in the following areas: the premotor area, primary somatosensory area, secondary somatosensory area, area 5, and thalamus. In contrast, there was no precise topographic organization of labeled projection neurons in the following areas: the supplementary motor area, cingulate motor area, primary motor cortex adjacent to the injection sites, claustrum, and basal nucleus of Meynert. The present study revealed that the forelimb area of the primary motor cortex receives both segregated and intermixed inputs from cortical and subcortical sources. In particular, the fact that the forelimb area of the primary motor cortex receives topographically organized inputs from the premotor area and nontopographically organized inputs from the supplementary motor area and cingulate motor area indicates possible different functional roles of frontal premotor areas in control of coordinated distal and proximal forelimb movements.

Animals↗
PubMed1993

Inhibitory effects of propiverine on rat and guinea-pig urinary bladder muscle.

In muscle strips isolated from guinea-pig and rat urinary bladder, propiverine (3-10 microM) inhibited carbachol-induced contractions in the presence of verapamil and Ca(2+)-induced contractions in excess K+ medium containing atropine, suggesting it has both anticholinergic and Ca2+ channel blocking actions. The Ca2+ channel blocking action was also demonstrated by recording inward Ca2+ currents in single cells dispersed from both species. The inhibition of inward currents by propiverine was three times stronger in the rat than the guinea-pig, ID50 being 7 microM for rat and 21 microM for guinea-pig. The recovery of the current after washout was faster than that of mechanical inhibition. It is concluded that propiverine blocks not only muscarinic receptors, but also Ca2+ channels at similar concentrations.

Animals↗
PubMed1993

Laminar organization of the substantia nigra pars reticulata in the macaque monkey, with special reference to the caudato-nigro-tectal link.

A laminar organization of the substantia nigra pars reticulata (SNr) was revealed in the macaque monkey by using an semihorizontal section plane parallel to the long axis of the SNr in the frontal plane. After injecting horseradish peroxidase conjugated to wheat germ agglutinin into the caudate nucleus (Cd) or putamen, anterogradely labelled fibres and axon terminals in the SNr were observed to form parallel bands in the anteromedial-posterolateral direction. After injecting Fast Blue into the superior colliculus, a cluster of retrogradely labelled neuronal cell bodies also formed a single band arranged in the similar anteromedial-posterolateral direction. The cluster was observed along the anterolateral margin of the SNr. This SNr region containing nigrotectal neurons appeared to overlap with one of the bands containing terminals of striatonigral fibres arising from the body of the Cd. The caudato-nigro-tectal link via the anterolateral marginal area might be involved in the control of saccadic eye movements.

Animals↗
PubMed1993

Effects of magnesium on isolated canine coronary arterial tension.

The effects of magnesium on the tension of isolated canine coronary arterial strips were studied. In the solution containing K+ of 20 mEq.l(-1), Ca2+ of 4 mEq.l(-1), and Na+ of 127 mEq.l(-1), the tension was 811 +/- 111 mg with Mg2+ of 1 mEq.l(-1), 494 +/- 135 mg with Mg2+ of 10 mEq.l(-1), 272 +/- 126 mg with Mg2+ of 20 mEq.l(-1), -52 +/- 63 mg with Mg2+ of 30 mEq.l(-1), -69 +/- 80 mg with Mg2+ of 40 mEq.l(-1). In the solution containing K+ of 20 mEq.l(-1), Na+ of 12 mEq.l(-1) and Ca2+ of 0 mEq.l(-1), the tension was 102 +/- 22 mg with Mg2+ of 1 mEq.l(-1), 3 +/- 35 mg with Mg2+ of 10 mEq.l(-1), -49 +/- 33 mg with Mg2+ of 20 mEq.l(-1), -59 +/- 49 mg with Mg2+ of 30 mEq.l(-1), -65 +/- 54 mg with Mg2+ of 40 mEq.l(-1). The data demonstrated that Mg2+ above 30 mEq.l(-1) inhibited the increase in tension caused by Ca2+ and Mg2+ above 20 mEq.l(-1) inhibited the increase in tension caused by low Na+ concentration.

Journal Article↗
PubMed1993

Serotoninergic projections from the dorsal raphe nucleus to the nucleus submedius in the rat and cat.

The nucleus submedius in the medial thalamus has been known to receive spinothalamic and trigeminothalamic fibers, and to contain neurons which can be activated by noxious stimuli. These previous findings suggest that the nucleus submedius may be involved in the processing and relay of pain-related information. In the present study, we immunohistochemically observed in the rat and cat that the nucleus submedius was distributed with a considerable amount of serotoninergic fibers. After iontophoretic injection of cholera toxin B subunit into the nucleus submedius, the sequential double-antigen immunofluorescence histochemistry for retrogradely transported cholera toxin B subunit and serotonin revealed that the serotoninergic fibers to the nucleus submedius arose mainly from the dorsal raphe nucleus, and additionally from the ventrolateral and medial parts of the midbrain periaqueductal gray. The direct projections from the dorsal raphe nucleus to the nucleus submedius were confirmed by anterograde axonal tracing after iontophoretic injection of Phaseolus vulgaris-leucoagglutinin into the dorsal raphe nucleus. The disappearance of almost all serotoninergic fibers in the nucleus submedius was also observed after destruction of the dorsal raphe nucleus. The fluorescent retrograde double-labeling with Diamidino Yellow and Fast Blue further revealed that some neurons in the dorsal raphe nucleus projecting directly to the nucleus submedius sent their axon collaterals to the ventrolateral orbital region of the cerebral cortex, nucleus accumbens, amygdala, nucleus raphe magnus, caudal spinal trigeminal nucleus, or spinal cord. The possible roles of the serotoninergic projections from the dorsal raphe nucleus to the nucleus submedius in pain control and/or the olfactolimbic functions are discussed.

Animals↗
PubMed1993

[A case of metastatic spinal tumor from renal cancer reduced by interferon-alpha].

A case of metastatic spinal tumor from renal cancer reduced by interferon-alpha is reported. A 54-year-old man was admitted to Tane General Hospital on April 12, 1990, with the complaint of difficulty in walking. Abdominal CT scan revealed right renal carcinoma, and MRI demonstrated metastatic spinal tumor at Th6, which was mainly occupying the entire lamina, spinous process and right pedicle of Th6. Nephrectomy was performed and, instead of operating on the spinal lesion, the patient was given follow-up treatment with administration of interferon-alpha (5 million units twice a week) and steroid. 1 year and 6 months later the patient's walking ability began to deteriorate and paraparesis progressed, although the size of the metastatic spinal tumor had gradually reduced. This was thought to be because of atrophy of the legs due to prolonged bed rest and steroid administration. Laminectomy with total removal of the tumor was performed on January 16, 1992. In the 12 months postoperatively, there has been neither recurrence nor remote metastasis seemingly due to the administration of interferon-alpha. This appears to be the first report of metastatic spinal tumor from renal cancer reduced by interferon-alpha.

Carcinoma, Renal Cell↗
PubMed1992

Pallidal inputs to thalamocortical neurons projecting to the supplementary motor area: an anterograde and retrograde double labeling study in the macaque monkey.

The relationship between thalamocortical neurons projecting to the supplementary motor area (SMA) and pallidothalamic projection fibers was examined with an anterograde and retrograde double labeling technique in macaque monkeys (Macaca fuscata). In each monkey, Fast Blue (FB) was injected into the hand-arm area of the SMA after mapping the somatotopy using intracortical microstimulation, and horseradish peroxidase conjugated with wheat germ agglutinin (WGA-HRP) was injected into the ipsilateral internal segment of the globus pallidus (GPi). As a result, numerous projection neurons labeled with FB were distributed in pallidal terminal areas labeled with WGA-HRP in the ventral nuclear group of the thalamus. The present findings indicate that the SMA receives strong indirect projections from the GPi via the thalamus.

Afferent Pathways↗
PubMed1992

Effects of ammonium chloride on membrane currents of acinar cells dispersed from the rat parotid gland.

In acinar cells freshly dispersed from rat parotid glands, the effects of ammonium chloride (NH4Cl) on membrane currents were studied using the whole-cell clamp method. When membrane currents were recorded with command pulses to 0 mV, applied at 2-s intervals from a holding potential of -70 mV, NH4Cl (5-20 mM) transiently decreased outward currents and then slowly increased both outward and inward currents. After reaching a peak in about 40-50 s, both outward and inward currents gradually decreased in the presence of NH4Cl and, on its wash-out, the currents returned to the control level. Butyrate (5-20 mM) had little effect on the resting membrane currents, but markedly inhibited the response to NH4Cl. Tetraethylammonium (5 mM) strongly reduced both the resting and NH4Cl-induced outward currents, whereas it slightly potentiated the NH4Cl-induced inward current without affecting the membrane current at the holding potential. Without ATP in the patch pipettes, carbachol-induced membrane currents were relatively resistant to Ca2+ removal from the external medium, but NH4Cl-induced currents were quickly abolished in the absence of Ca2+. We conclude that intracellular alkalinization with NH4Cl increases Ca2+ influx and activates Ca(2+)-dependent outward K+ and inward Cl- currents.

Ammonium Chloride↗
PubMed1992

Effects of intracellular ATP on calcium current in freshly dispersed single cells of guinea-pig portal vein.

In smooth muscle cells freshly dispersed from the guinea-pig portal vein, inward currents were recorded with the whole-cell clamp method in the presence of 2.4 mM Ca2+ under the condition in which outward K+ currents were suppressed and the effects of ATP in patch pipettes were studied. There was a large variation of the rate of current decay, the half-decay time ranging from 20 to 80 ms, but it was difficult to demonstrate clearly the presence of fast (T-type) and slow (L-type) Ca2+ channels based on threshold, the effects of changing holding potential, and of nicardipine, a dihydropyridine Ca2+ channel blocker. Intrapipette ATP had a weak potentiating effect on inward current, but did not seem to influence the correlation between peak current amplitude and current configuration. Cyanide (0.5 mM) reduced inward currents, particularly when ATP concentration was low and only limited recovery was observed. It was concluded that the amplitude and the rate of current decay of inward currents are not only determined by intracellular ATP, but also significantly influenced by some other factor, such as that involved in 'run-down' of Ca2+ currents.

Action Potentials↗
PubMed1991

Effects of Ca2+ removal and of tetraethylammonium on membrane currents induced by carbachol in isolated cells from the rat parotid gland.

In freshly dispersed rat parotid acinar cells, 10 microM carbachol increased outward currents at 0 mV and also inward currents at -70 mV recorded with the wholecell clamp method using patch pipettes containing 1 mM EGTA. When EGTA in the pipette was increased to 2.4 mM, carbachol increased only outward currents and a further increase of EGTA to 4 mM blocked the carbachol response. Effects of changes in external K+ and Cl- concentrations suggested that outward currents were carried by K+ and inward by Cl-. Effects of Ca2+ removal from the medium differed between experiments with 0 and 5 mM ATP in the patch pipettes. When pipettes contained no ATP, responses evoked by repeated applications of 10 microM carbachol (0.5-1 min) at 1.5-4 min intervals decreased only slowly after Ca2+ removal, outward currents being reduced to 90 +/- 6% and inward currents to 47 +/- 11% (n = 6) in 10 min. On the other hand, when 5 mM ATP was included in the electrodes, Ca2+ removal abolished the carbachol responses in about 5 min (n = 4). It was also found that tetraethylammonium (5 mM) strongly reduced both currents, by blocking muscarinic receptors, while Ba2+ (2.4 mM) inhibited only the outward K+ current.

Adenosine Triphosphate↗
PubMed1991

Effects of sodium and temperature on tension in isolated canine coronary artery.

The effects of sodium and temperature on tension of isolated canine coronary arterial strips were studied. In 20 mEq. l(-1) K solution, the strength of tension was inversely related to the Na concentration. At 37 degrees C, the tension was significantly increased at 70 mEq. l(-1) Na and below. The tension was gradually suppressed by lowering of the temperature from 37 degrees C to 10 degrees C. At 10 degrees C, tension did not developed significantly at Na concentrations between 127 mEq. l(-1) and 12 mEq. l(-1). It was concluded that the decrease in Na concentrations increased the tension of the canine coronary artery and the lowering of temperature supressed the tension inducted by the decrease in Na concentrations.

Journal Article↗
PubMed1991

Effects of calcium and temperature on tension in isolated canine coronary artery.

The effects of calcium and temperature on the tension of isolated canine coronary arterial strips were studied. In 20 mEq. l(-1) K solution, the tension was significantly increased from 0 mg with 0 mEq. l(-1) Ca to 33 +/- 18 mg with 0.2 mEq. l(-1) Ca at 37 degrees C, from -40 +/- 18 mg with 0 mEq. l(-1) Ca to -17 +/- 11 mg with 0.2 mEq. l(-1) Ca at 30 degrees C, from -77 +/- 19 mg with 0 mEq. l(-1) Ca to -52 +/- 17 mEq. l(-1) with 1 mEq. l(-1) Ca at 25 degrees C, from -88 +/- 13 mg with 0 mEq. l(-1) Ca to -41 +/- 18 mg with 2 mEq. l(-1) Ca at 20 degrees C, from -125 +/- 16 mg with 0 mEq. l(-1) Ca to -116 +/- 13 mg with 2 mEq. l(-1) Ca at 15 degrees C. Ca higher than 0.2 mEq. l(-1) produced a dose-dependent increase in tension between 37 degrees C and 15 degrees C. In spite of the presence of 4 mEq. l(-1) Ca, the development of tension was strongly supressed by lowering the temperature below 20 degrees C, and completely inhibited at 10 degrees C. The rate of a decrease in tension caused by cooling was about 5.5 mg. degrees C(-1). This study demonstrated that Ca(2+) produced a dose-dependent increase in tension in high-K solution, which was suppressed as the temperature was lowered.

Journal Article↗
PubMed1990

Auditory brainstem in the mole (Mogera): nuclear configurations and the projections to the inferior colliculus.

Anatomical organization of the central auditory system in the mole was studied at the lower brainstem levels. The cyto-, myelo-, and chemoarchitectures were examined in Nissl, myelin, and acetylcholinesterase stained materials, and then the origins of the ascending afferents to the inferior colliculus (IC) were identified by injecting wheatgerm agglutinin conjugated to horseradish peroxidase (WGA-HRP) into the unilateral IC and processing the tissue according to the standard retrograde tracing techniques. The results indicate that the auditory nuclei and pathways in the lower brainstem of the mole conform to the basic plan common to many other mammals. Nevertheless, several characteristic features are evidenced in the present study: (1) in the cochlear nucleus (CochN), granule cell fields are very large in both the ventral (VCN) and dorsal (DCN) nuclei; among several populations of neurons, fusiform cells in the DCN, multipolar cells in the VCN and DCN, and small spherical cells in the VCN project to the IC directly, (2) in the superior olivary complex (SOC), the medial nucleus (MSO) is well developed in comparison with that in the hedgehog, the opossum, the mouse, and the rat, although the general configuration of the SOC is similar to that in those mammals, most strikingly, the MSO projects to the IC bilaterally in the mole, and (3) the nuclei of the lateral lemniscus (NLL) show a great development and consist of three well-differentiated parts of the dorsal, intermediate, and ventral nuclei. The projections from these subnuclei to the IC conform to the basic mammalian plan.

Animals↗
PubMed1990

Monosynaptic projection from the pedunculopontine tegmental nuclear region to the reticulospinal neurons of the medulla oblongata. An electron microscope study in the cat.

The magnocellular reticular nucleus (MRN) of the cat was observed electron microscopically following the combined application of kainic acid into the pedunculopontine tegmental nuclear region (PPN region) and horseradish peroxidase conjugated to wheat germ agglutinin (WGA-HRP) into the spinal cord. Some degenerating axon terminals arising from the PPN region were found to make synaptic contacts with retrogradely HRP-labeled reticulospinal neurons in the MRN.

Animals↗
PubMed1990

Human striatal cholinergic neurons in development, aging and Alzheimer's disease.

The cross-sectional area of cholinergic neurons stained immunohistochemically for choline acetyltransferase were measured in the striatum of infants, young adults, aged individuals and patients with Alzheimer's disease. Cholinergic neurons were distributed throughout the caudate nucleus and the putamen and displayed no significant variations in size across the two structures. The cross-sectional area of striatal cholinergic neurons was smaller in infants as compared with all other groups examined. No significant changes were observed in the size of these neurons as a consequence of aging or Alzheimer's disease.

Adult↗