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Biomedical subjects

H Kojima

Publications and source records attributed to H Kojima.

At least 631 records · Page 35Linked to original sources
PubMed1985

Localization of hepatitis A virus in marmoset liver tissue during the acute phase of experimental infection.

Electron microscopic and virological studies of marmoset liver tissue with acute infection of hepatitis A virus (HAV), especially in the earlier stages of infection, were carried out to characterize the maturation process of HAV. Four marmosets were inoculated intravenously with HAV suspension and sacrificed 1 week, 2 weeks, 3 weeks and 4 weeks after inoculation respectively. Hepatitis A antigen (HAAg) in 10% liver homogenates of marmosets was examined by radioimmunoassay and a large amount of HAAg was detected in the liver homogenate of two marmosets sacrificed 2 weeks and 3 weeks after inoculation respectively. The histodiagnosis of the marmoset sacrificed 2 weeks after HAV inoculation was normal. However, many clusters of virus-like particles about 27 nm in diameter, in both "solid" and "empty" forms were found, mainly in vesicles of Kupffer cells by electron microscopy. In the animal that developed mild hepatitis 3 weeks after inoculation HAV-like particles were found in vesicles of hepatocytes by electron microscopy. By immune electron microscopy using peroxidase-conjugated anti-hepatitis A antibody, HAAg was detected on the particles present within the cytoplasmic vesicles of Kupffer cells or hepatocytes and on the surrounding membrane of the vesicles which contained HAV-like particles.

Alanine Transaminase↗
PubMed1985

An in vitro preparation and study of cells in cat visual cortex.

We have described full details of the preparation of slices from the visual cortex of cats. Then, we presented the results concerning the effects of the deprivation of glucose from the circulating medium on neuronal activities in the slices and the electrophysiological criteria for identifying glial cells in the sliced brain tissues. The results indicated that transsynaptic responses were reversibly blocked within 10-20 min, while nonsynaptic responses continued for more than 60 min in the glucose-free medium. We showed that glial cells could be identified according to the criteria proposed in in vivo experiments.

Action Potentials↗
PubMed1985

Studies on the sequence of 2,6-diisopropylnaphthalene metabolite formation using carp hepatocyte.

Metabolism of 2,6-diisopropylnaphthalene (2,6-DIPN) was studied in freshly isolated carp hepatocytes with special reference to cytochrome P-450-mediated oxidation. The viability of isolated hepatocytes obtained by use of Ca2+-free and collagenase-containing Hanks buffer was 93%, judging from both trypan blue penetration and lactic dehydrogenase (LDH) leakage. 2,6-DIPN was metabolized to form several oxidized products such as the tertiary hydroxy, the primary hydroxy, and two types of dihydroxy DIPN. From the results of the time course experiments, it was assumed that 2,6-DIPN was hydroxylated primarily on the tertiary and primary positions of the isopropyl group, respectively, and thereafter was converted to tertiary-tertiary and primary-tertiary hydroxylated products. These assumptions are supported by results obtained previously in in vivo and in vitro studies.

Animals↗
PubMed1985

A case of cerebral infarction showing periodic lateralized epileptiform discharges.

This is a report about the case of a 37-year-old female with left temporal damage due to a cerebral infarction and showing periodic lateralized epileptiform discharges (PLEDs). A hypsarhythmia-like pattern was observed a week after the onset. A repeat tracing of EEGs taken two weeks after the onset clarified the presence of PLEDs, consisting of a lateralized slow spike discharge in a rhythmic fashion at a frequency of every 1.6 seconds. PLEDs disappeared two months after the onset, and EEG activity normalized three months after the onset. But, her regressive behavior, crying before her doctor, which was considered to be due to a personality change, persisted for some years.

Adult↗
PubMed1985

Characterization of miniature inhibitory post-synaptic potentials in rat spinal motoneurones.

Intracellular recordings were made from motoneurones in the isolated spinal cord of neonatal rats. After action potentials had been abolished by tetrodotoxin (TTX, 10(-6) g/ml), small (approximately 0.4 mV) depolarizing potentials occurred spontaneously in motoneurones at low frequencies (approximately 1.5 Hz). These potentials were detectable only after the intracellular Cl- concentration of motoneurones was raised by using KCl electrodes and most of them were blocked by strychnine, suggesting that they are inhibitory post-synaptic potentials (i.p.s.p.s). These spontaneous i.p.s.p.s under TTX are designated as 'miniature i.p.s.p.s' in order to distinguish them from i.p.s.p.s arising from spontaneous impulse activities of interneurones or afferent fibres. The miniature i.p.s.p.s were still observed after Ca2+ in saline was substituted by Mg2+ or Mn2+. In low Ca2+ and high Mg2+ saline, the amplitude distribution of miniature i.p.s.p.s was essentially the same as in normal saline. The frequency of miniature i.p.s.p.s increased when external Ca2+ concentration was raised. The frequency decreased to about 60% of the control when external Ca2+ was substituted by Mg2+ (2-4 mM), whereas it increased to more than 20-fold when substituted by Mn2+ (3-5 mM). When the external K+ concentration was raised, the frequency of miniature i.p.s.p.s under TTX increased non-linearly with the K+ concentration. The maximum slope in the relation between the log frequency and log K+ concentration was about 3.6. When the osmotic pressure was increased by adding sucrose, miniature i.p.s.p.s increased in frequency. The effect of osmotic pressure was relatively mild compared with that reported for the miniature end-plate potentials (e.p.p.s) in the frog. When the temperature was raised, the frequency of miniature i.p.s.p.s increased. The relation between frequency and temperature fitted approximately to a straight line in Arrhenius plot with a Q10 of about 2.6. These characteristics of the miniature i.p.s.p.s closely resemble those of the miniature e.p.p.s. It is concluded that the miniature i.p.s.p.s recorded in motoneurones are equivalent in nature to the miniature e.p.p.s in neuromuscular junctions, thus reflecting the spontaneous release of quantal packages of the inhibitory transmitter.

Action Potentials↗
PubMed1985

Low-threshold, slow-inactivating Na+ potentials in the cockroach giant axon.

Electrophysiological properties of the ventral giant axon in the abdominal nerve cord of the cockroach were studied by recording intracellular potentials following partial or complete block of the K+ conductance. When the K+ conductance was completely blocked by tetraethylammonium (TEA) and 3,4-diaminopyridine, the intensity of depolarizing currents necessary for eliciting the action potential was markedly decreased, and the action potential was followed by a prolonged plateau potential. During the plateau potential following the spike, the input resistance was significantly reduced. The plateau potential was not affected by changing the external Ca2+ concentration but depended on the external Na+ concentration in a manner expected from the Nernst equation and was blocked by tetrodotoxin (TTX). During the plateau potential, the Na+ conductance responsible for the spike was inactivated, whereas immediately after the plateau potential a newly evoked spike was not followed by a plateau potential, suggesting different inactivation kinetics between the spike and plateau Na+ conductances. When the K+ conductance was partially blocked by TEA alone, slow depolarizing responses were evoked at voltage levels a few millivolts more positive than the resting potential. The "threshold" for the slow potential was much lower than that for the spike potential. The slow potential produced after partial block of the K+ conductance was not affected by alterations of the external Ca2+ concentration but was blocked by TTX or in a Na+-free solution. Even in normal medium, a small TTX-sensitive depolarizing response was discernible. This response was similar in its time course and threshold to the slow potential observed after partial block of the K+ conductance. It is concluded that the cockroach giant axon has two populations of Na+ channels, which can be distinguished by differences in time course and voltage levels for activation and that the slow, low-threshold Na+-dependent potential is largely masked by delayed increases in the K+ conductance under normal conditions. It remains uncertain whether the low-threshold slow potential and the plateau potential originate from the same or different populations of Na+ channels.

4-Aminopyridine↗
PubMed1985

Effect of timiperone, a new antipsychotic drug, on the sleep-wakefulness cycle in cats.

The effect of timiperone, a new antipsychotic drug, on the sleep-wakefulness cycle in cats was assessed by EEG, EMG and eye movement potential. Timiperone (0.03 to 0.3 mg/kg, i.p.) dose-dependently increased the slow wave sleep (SWS) time and decreased the paradoxical sleep (PS) time. Further, the onset of the first period of PS was delayed, and the number of PS phases tended to be decreased after the 0.3 mg/kg dose. These results suggest that the neurological control of the cerebral dopaminergic system might be at least in part attributable to the effect of timiperone on sleep mechanisms.

Animals↗
PubMed1985

[Ventricular activation sequence estimated by body surface isochrone map].

This study was performed to evaluate the usefulness of the body surface isochrone map (VAT map) for identifying the ventricular activation sequence, and it was correlated with the isopotential map. Subjects consisted of 42 normal healthy adults, 18 patients with artificial ventricular pacemakers, and 100 patients with ventricular premature beats (VPB). The sites of pacemaker implantations were the right ventricular endocardial apex (nine cases), right ventricular epicardial apex (five cases), right ventricular inflow tract (one case), left ventricular epicardial apex (one case), and posterior base of the left ventricle via the coronary sinus (two cases). An isopotential map was recorded by the mapper HPM-6500 (Chunichi-Denshi Co.) on the basis of an 87 unipolar lead ECG, and a VAT isochrone map was drawn by a minicomputer. The normal VAT map was classified by type according to alignment of isochrone lines, and their frequency was 57.1% for type A, 16.7% for type B, and 26.2% for type C. In the VAT map of ventricular pacing, the body surface area of initial isochrone lines represented well the sites of pacemaker stimuli. In the VAT map of VPB, the sites of origin of VPB agreed well with those as determined by the previous study using an isopotential map. The density of the isochrone lines suggested the mode of conduction via the specialized conduction system or ventricular muscle. The VAT map is a very useful diagnostic method to predict the ventricular activation sequence more directly in a single sheet of the map.

Bundle-Branch Block↗
PubMed1985

[An autopsy case of primary splenic hemangiosarcoma].

A 28-year-old woman was admitted six months before her death because of abdominal pain, anemia and hepatosplenomegaly. Clinical diagnosis by biopsy examination was primary hepatic angiosarcoma. The autopsy revealed about 700 ml of bloody ascites. The spleen weighed 510 g, and was completely replaced by dark grayish-red tumors. The enlarged liver was 6,560 g and revealed multiple tumor nodules. Microscopically, the tumor cells formed irregular vascular spaces. Factor VIII-related antigens were stained in the tumor cells. Zonula adherens was observed also by electron microscopic observation.

Adult↗