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Biomedical subjects

M Kano

Publications and source records attributed to M Kano.

At least 181 records · Page 10Linked to original sources
PubMed1990

Participation of transient-type Ca2+ channels in the sustained increase of Ca2+ level in GH3 cells.

Participation of two types of Ca2+ channels (T- and L-types) in the sustained increase of cytosolic-free Ca2+ concentration [( Ca2+]i) was studied in thyrotropin-releasing hormone (TRH)-stimulated clonal GH3 pituitary cells. The effects of Ca2+ channel blockers were analyzed by measuring Ca2+ channel current and [Ca2+]i, using whole-cell voltage-clamp and Fura-2 fluorometry, respectively. Phenytoin (100 microM) and Ni2+ (100 microM) selectively blocked T-type Ca2+ channels and suppressed the TRH-induced sustained [Ca2+]i increase in single cells. Synthetic omega-conotoxin (omega-CgTX, 2 microM) preferentially blocked L-type Ca2+ channels, but it did not suppress the TRH-induced sustained [Ca2+]i increase. The present results suggest that the sustained elevations of [Ca2+]i triggered by TRH may be mediated by T-type Ca2+ channels in GH3 cells.

Animals↗
PubMed1990

Nature of optokinetic response and zonal organization of climbing fiber afferents in the vestibulocerebellum of the pigmented rabbit. I. The flocculus.

In pigmented rabbits anesthetized with N2O (70%) and halothane (2-4%), Purkinje cells were extracellularly recorded in the flocculus. A large central visual field (60 degrees x 60 degrees) was used to optokinetically stimulate either the ipsi- or contralateral eye, and the direction and velocity selectivities of complex spike responses were examined. For optokinetic stimulation (OKS) delivered to the ipsilateral eye (n = 129), the preferred direction was forward (F, n = 57) or upward (U, n = 37), while the remaining cells (n = 35) showed no response (N). For OKS delivered to the contralateral eye (n = 107), the preferred direction was backward (B, n = 11), downward (D, n = 42) or upward (U, n = 2), and the rest (n = 52) showed N. Cells tested with both eyes (n = 89) fell into five categories based on the preferred direction to ipsi- and contralateral OKS: (1) ipsi-F and contra-B (F/B type, n = 9), (2) ipsi-F but contra-N (F/N type, n = 28), (3) ipsi-U and contra-D (U/D type, n = 13), (4) ipsi-U but contra-N (U/N type, n = 17), and (5) ipsi-N but contra-D (N/D type, n = 22). The optimum velocity was within 0.1-2.0 degrees/s for all cells. On the average, the best response was obtained at 0.2-0.5 degrees/s stimulation. All ipsi-F cells responded to electrical stimulation of the optic tract (OT), while most cells preferring ipsi-U, contra-B and contra-D directions did not respond. No characteristic feature was found in cells innervated with collateralized climbing fiber branches to the nodulus. In the flocculus, cells preferring horizontal orientation (H cells, preferring ipsi-F and/or contra-B directions) were localized in a narrow dorsoventral zone (less than 1.0 mm) along the caudal border of the rostral one third, while those preferring the vertical orientation (V cells, preferring ipsi-U and/or contra-D directions) were in two distinct narrow zones located rostral and caudal to the H cell zone. H and V cells were intermingled in the central portion of the ventral flocculus. These four zones are in good agreement with previously defined H, anterior V, posterior V and R zones, respectively. The results indicate that the subdivision of the flocculus which controls horizontal (vertical) eye movements receives information regarding movements of the visual surround in the horizontal (vertical) orientation through visual climbing fiber afferents, thus being organized in olivo-cortico-nuclear functional units for control of eye movements.

Action Potentials↗
PubMed1990

Nature of optokinetic response and zonal organization of climbing fiber afferents in the vestibulocerebellum of the pigmented rabbit. II. The nodulus.

In pigmented rabbits anesthetized with N2O (70%) and halothane (2-4%), Purkinje cells were extracellularly recorded in the nodulus. Large field (60 degrees x 60 degrees) optokinetic stimulation (OKS) with constant velocity was delivered to either the ipsi- or contralateral eye, and the direction and velocity selectivities of complex spike responses were examined. To ipsilateral OKS (n = 181), the preferred direction was forward (F, n = 72), upward (U, n = 38) or downward (D, n = 10), while the remaining cells (n = 61) showed no response (N). To contralateral OKS (n = 117), the preferred direction was backward (B, n = 22), upward (U, n = 7) or downward (D, n = 22), while the rest (n = 66) showed N. Cells tested with both eyes (n = 95) fell into 8 categories based on the preferred direction to ipsi- and contralateral OKS: (1) ipsi-F and contra-B (F/B type, n = 20), (2) ipsi-F but contra-N (F/N type, n = 12), (3) ipsi-U and contra-D (U/D type, n = 15), (4) ipsi-U but contra-N (U/N type, n = 13), (5) ipsi-N but contra-D (N/D type, n = 1), (6) ipsi-D but contra-N (D/N type, n = 5), (7) ipsi-N but contra-U (N/U type, n = 6), and (8) N to both eyes (N/N type, n = 23). The optimum velocity was in the range 0.1-2.0 degrees/s for all cells responsive to OKS. In the ventral lamella, four medio-laterally aligned zones were demonstrated. In the most medial zone (0-0.5 mm from the midline), the majority of cells showed ipsi-N or contra-N responses. In the second zone (0.5-1.5 mm), most cells preferred ipsi-F or contra-B directions. In the third zone (1.5-2.5 mm), most cells preferred ipsi-U or contra-D directions. In the most lateral zone (2.5-3.5 mm), most cells preferred ipsi-F or contra-B directions. In the dorsal lamella, a longitudinal zone characterized with cells preferring ipsi-U or contra-D directions was found about 1.5-2.5 mm from the midline. This zone seemed to be the continuation of the third zone in the ventral lamella. Cells preferring ipsi-D or contra-U directions were scattered in the medial half of both the dorsal and ventral lamellae.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1990

Receptive field organization of climbing fiber afferents responding to optokinetic stimulation in the cerebellar nodulus and flocculus of the pigmented rabbit.

Under anesthesia with N2O (70%) and halothane (2-4%), complex spikes of Purkinje cells were extracellularly recorded in the nodulus and flocculus of immobilized pigmented rabbits. Optokinetic stimulation (OKS) was delivered to each eye as repetitive movements of a random dot pattern. The visual field of each eye was divided into anterior, central and posterior fields at axes 45 degrees and 135 degrees along the horizon. With OKS of the ipsilateral eye, the preferred direction of complex spike responses was: (1) forward (F) in all visual fields (F response), (2) upward (U) in both the anterior and central visual fields but downward (D) in the posterior visual field (U response), or (3) no response (N) in any of the visual fields (N response). With OKS of the contralateral eye, the preferred direction was: (1) backward (B) in both the anterior and central visual fields but N in the posterior visual field (B response), (2) U in the anterior but D in both the central and posterior visual fields (D response), or (3) N in all visual fields. Purkinje cells were classified into five categories in terms of the complex spike responses to OKS to the central visual fields of the ipsi-/contralateral eyes: F/B, F/N, U/D, U/N and N/D types. In cells with ipsi-F and/or contra-B responses, OKS delivered above the horizon induced F and/or B responses, but OKS below the horizon induced no response. In cells with contra-D response, OKS both above and below the horizon induced D responses. Cells with ipsi-U responses showed unusually complex direction selectivity: in the anterior, central and posterior fields, the preferred direction was U, U and D, respectively, above the horizon, as opposed to N, D and D below the horizon. In the nodulus, F/B and F/N type cells were localized in the ventral lamella within two distinct longitudinal zones about 0.5-1.5 and 2.5-3.5 mm from the midline, while U/D, U/N and N/D type cells were found in both the ventral and dorsal lamellae within a longitudinal zone about 1.5-2.5 mm from the midline. In the flocculus, the locations of F/N (or F/B), U/N and N/D type cells roughly corresponded to H, anterior V and R zones, respectively, as previously reported on the basis of the direction of eye movements induced by microstimulation.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗
PubMed1990

N-nitrosamines in gastric juice of patients with gastric ulcer before and during treatment with histamine H2-receptor antagonists.

The clinical implications of N-nitrosamines (NAs) were studied by analyzing their concentration in the gastric juice of 72 healthy subjects and 279 patients with gastric ulcer before and during treatment with histamine H2-receptor antagonists. NAs were measured by combined gas chromatography and thermal energy analyzer. The detection ratios of N-nitrosodimethylamine (NDMA) and N-nitrosodiethylamine (NDEA) in the patients were 35.3% and 34.6%, respectively, which were significantly higher than the corresponding values in healthy subjects (19.4% and 16.7%, P less than 0.01). Analysis among the patients showed that this trend was mainly due to higher values in patients who were given histamine H2-receptor antagonists, as their detection ratios increased to 40.2% (NDMA) and 39.9% (NDEA). Patients without histamine H2-receptor antagonists showed moderate increases of detection ratios (NDMA; 24.2% NDEA; 22.6%) compared with healthy controls. The differences in these values between those receiving and not receiving histamine H2-receptor antagonists were statistically significant (P less than 0.01). The maximum concentrations of NDMA and NDEA were 7.9 and 9.8 ng/ml in patients, and 1.2 and 1.3 ng/ml in healthy subjects (the difference between the 2 groups P less than 0.02). These results indicated that patients with gastric ulcer had higher detection ratios and concentrations of NDMA and NDEA in gastric juice and that, while significant increases occurred during treatment with histamine H2-receptor antagonists, the extent of increase was below toxic or experimental carcinogenic levels.

Adult↗
PubMed1990

N-nitrosamines in the stomach with special reference to in vitro formation, and kinetics after intragastric or intravenous administration in rats.

To study the implications of nitrosation in the stomach, the formation of N-nitrosodimethylamine (NDMA) and N-nitrosodiethylamine (NDEA) from nitrite and secondary amines was examined in vitro under conditions simulating gastric juice. Kinetics of NDMA were investigated after intragastric or intravenous administration of 0.2 mg/kg of NDMA in rats. NDMA and NDEA were measured using combined gas chromatography and thermal energy analyzer. Nitrite levels in human gastric juice were less than 10 micrograms/ml. Optimal pH for nitrosation was between 2.0 to 3.5. Nitrosamine formation reached maximum concentration at 3 to 6 hours. The maximum ratios of nitrosation were 0.15 and 0.11% in NDMA/nitrite and NDEA/nitrite, respectively. In the kinetic study, the highest blood levels of NDMA were observed at 5 min, reaching 174 +/- 40 and 374 +/- 40 ng/ml after administration into the stomach and duodenum, respectively. Then they decreased exponentially and were not detectable after 4 hours. Tissue levels of NDMA in the liver, spleen, kidney, lung and brain showed 70% of the blood levels. Urinary excretion of intravenously administered NDMA during the first 4 hours was less than 0.2%. These results supported the hypothesis that nitrosation occurred in gastric juice under optimal conditions, and indicated that nitrite levels were the limiting factor for nitrosation. Quick disappearance from the gastrointestinal tract suggested that the pathologic implication of nitrosamines formed in the stomach could be important for other organs.

Animals↗
PubMed1990

Molecular cloning and sequence of the complementary DNA encoding human mitochondrial acetoacetyl-coenzyme A thiolase and study of the variant enzymes in cultured fibroblasts from patients with 3-ketothiolase deficiency.

Complementary DNAs encoding the precursor of human hepatic mitochondrial acetoacetyl-CoA thiolase (T2) (EC 2.3.1.9) were cloned and sequenced. The cDNA inserts in these clones were 1,518 bases in length when overlapped, and encoded the 427-amino acid precursor of this enzyme (45,199 mol wt). This amino acid sequence included a 33-residue leader peptide moiety and a 394-amino acid subunit of the mature enzyme (41,385 mol wt). The T2 gene expression in fibroblasts from four patients with 3-ketothiolase deficiency was analyzed by Northern blotting. The T2 mRNA in all four cell lines had the same 1.7 kb as that of the control. However, the amounts of T2 mRNA differed: the content was reduced in two cell lines (cases 1 and 3), whereas it was within a normal range in others (cases 2 and 4). Pulse labeling followed by subcellular fractionation revealed that the T2 proteins in the fibroblasts from these patients are present in the mitochondria. These results suggest that different mechanisms are involved in the enzyme defects in the four patients.

Acetyl-CoA C-Acetyltransferase↗
PubMed1990

[A case of embryonal carcinoma arising in the basal ganglia of the cerebrum].

The occurrence sites of intracranial primary germ cell tumors are most often the pineal and suprasellar regions. The histological type observed most frequently in these tumors is germinoma. Cases of embryonal carcinoma arising in the basal ganglia are rarely reported. To our knowledge, only 4 such cases have been previously reported in the literature. A case of an embryonal carcinoma arising in the basal ganglia is reported. A 17-year-old boy was admitted to our hospital on July 30, 1988 because of headache and vomiting, and a right hemiparesis. On admission, physical inspection showed no abnormalities and neurological examination revealed obtunded consciousness, a right central facial paresis and a right hemiparesis with Hoffman and Babinski reflexes. Noncontrast CT scan showed a large mass of low-to slightly high-density in the region of the left basal ganglia accompanied with midline shift and ventricular dilatation. Enhancement of the lesion was made by contrast CT scan. It was not homogeneous. Cerebral angiogram displayed a contralateral shift and an unrolling of the anterior cerebral artery, a lateral stretch of middle cerebral artery, a downward stretch of anterior choroidal artery and a tumor stain fed by the Heubner artery. On August 3, left frontotemporal craniotomy was performed. The tumor was totally removed in a piecemeal manner using microsurgical techniques. Histopathological diagnosis was mixed-type of germ cell tumor comprising embryonal carcinoma and teratoma. Postoperative CT scan showed complete disappearance of the tumor. A course of radiation of 4950 rads and two courses of a combination chemotherapy with cis-platinum, vinblastine and bleomycin were given within 3 months after the operation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Effects of 1 alpha-hydroxyvitamin D3 on N-methyl-N-nitrosourea-induced colonic tumorigenesis, and on fecal bile acid profiles with respect to soluble and precipitated phases in rats.

Vitamin D3 inhibited the promotion by exogenous promoters in experimental colonic tumorigenesis. To give more insight into this phenomenon, the effect of 1 alpha-hydroxyvitamin D3 (1 alpha(OH)D3) on N-methyl-N-nitrosourea (MNU)-induced colonic tumorigenesis was studied in rats without exogenous promoters. Fecal bile acids were analyzed to examine as to whether 1 alpha(OH)D3 increased the concentration of soluble bile acids. Eighty-seven female F344 rats received 2 mg of MNU intrarectally 5 times in 2 weeks, and were divided into 3 groups. One group (n = 29) was left without any treatment. Two groups (each, n = 29) were given 0.2 ml of medium chain triglyceride (MCT) or MCT containing 0.04 microgram of 1 alpha(OH)D3 through an intragastric route thrice weekly for 38 weeks. At autopsy, numbers of rats with colonic tumor were 9 (31%), 10 (34%) and 10 (34%) in the group receiving MNU alone, MNU + MCT and MNU + 1 alpha(OH)D3, respectively (chi 2 = 0.103, P less than 0.95). Fecal bile acid profiles showed no appreciable difference among these groups, nor was observed any increase of soluble bile acids in the MNU + 1 alpha(OH)D3 group. These results indicated that the administration of 1 alpha(OH)D3 did not affect colonic tumorigenesis under the condition where exogenous promoters were not applied, and that 1 alpha(OH)D3 did not seem to interfere the formation of bile acid calcium salts in animals on a regular diet.

Animals↗
PubMed1990

Growth factor expression after stroke.

Fibroblast growth factors are polypeptides with potent trophic effects on central nervous system cells. Both acidic and basic forms of fibroblast growth factor are found in the mammalian brain. We have examined the expression of these factors after focal brain injury or stroke. After infarction of the lateral cerebral cortex in the mature rat brain, we found a twofold to threefold increase during the first 3 weeks after stroke in levels of fibroblast growth factors in tissue surrounding infarcts. This increase persisted for at least 2 months and appeared mainly to be due to increased levels of basic, but not acidic, fibroblast growth factor. Because of its gliotrophic, angiogenic, and neuronotrophic properties, basic fibroblast growth factor may play an important role in the cascade of cellular reactions that contributes to wound healing and functional recovery after stroke.

Animals↗
PubMed1989

Two components of calcium channel current in embryonic chick skeletal muscle cells developing in culture.

The properties of the Ca channel currents in chick skeletal muscle cells (myoballs) in culture were studied using a suction pipette technique which allows internal perfusion and voltage clamp. The Ca channel currents as carried by Ba ions were recorded, after suppression of currents through ordinary Na, K and Cl channels by absence of Na, K and Cl ions, by external TEA, by internal EGTA and by observing the Ba currents instead of the Ca currents. Two components of Ba current could be distinguished. One was present only if the myoballs were held at relatively negative holding potentials below -50 mV. This component first became detectable at clamp potentials of about -50 mV and reached a maximum between -10 and -20 mV. During long clamp steps, it became inactivated completely. The inactivation process of this component at a clamp potential of -30 mV was well fitted to a single exponential with a time constant of about -20 ms. Half-maximal steady-state inactivation was observed at -63 mV. The other component persisted even at relatively positive holding potentials above -40 mV, was observed during clamp pulses to -20 mV and above, and reached a maximum between +10 and +20 mV. This component inactivated very little; a substantial fraction of this component remained at the end of clamp pulses lasting 1 s. The inactivation process of this component at a clamp potential of -10 mV apparently followed a single exponential with a time constant of about 1 s. Half-maximal steady-state inactivation was attained at -33 mV. Both components of Ba current were blocked by Co ions, but organic Ca channel blocker D600 preferentially blocked the high-threshold, slowly inactivating component. The relationship between the current amplitude and the concentration of the external Ba ions was different between the two components. Furthermore, the two components of Ba current also differed in their developmental profile. These findings demonstrate the existence of two distinct types of Ca channels in the early stages of chick muscle cell development.

Animals↗
PubMed1989

Anomalous increase of Ca2+ current by high concentration K+ stimulation in whole cell clamped GH3 cells.

We examined the effect of high concentration K+ (50 mM K+) stimulation to neurosecretory GH3 cells under voltage clamp control and unexpectedly found a considerable increase in the inward current evoked by depolarizing pulses. This augmented current was present in Na+-free solution containing Ca2+, tetraethylammonium+ and tetrodotoxin and showed similarity in its voltage dependence to the Ca+ channel current in the control (5 mM K+) solution. The augmented current was significantly reduced by Ca2+ channel blockers, Co2+ (5 mM) and nifedipine (2.5 microM), and was increased by the raise of external Ca2+ concentration. Correspondingly, Quin-2 experiments in GH3 cells showed that the rise in cytosolic free Ca2+ concentration in response to high K+ stimulation was suppressed by the same concentration of nifedipine. These data suggest that, in addition to its depolarizing effect, high K+ may modify voltage-sensitive Ca2+ channels such that they exhibit increased permeability although their voltage dependence of activation and pharmacological sensitivity remain largely unchanged.

Animals↗
PubMed1989

Campylobacter pylori in Japan: bacteriological feature and prevalence in healthy subjects and patients with gastroduodenal disorders.

The presence of Campylobacter pylori was investigated in biopsy specimens obtained during gastrofiberscopy from 103 consecutive patients prospectively. Patients included 25 with gastric ulcer, 4 with duodenal ulcer, 5 with coexisting gastroduodenal ulcer, 31 with gastroduodenal ulcer with gastritis, 27 with gastritis, 3 with gastric polyps and 8 with gastric cancer. Results were compared with 20 healthy control subjects who were endoscopically normal. Two specimens each were taken from 3 sites in the stomach. One part was used for a histological study to examine the presence of the organisms. The other part was cultured using Skirrow's agar microaerophilically. Conventional microflora and C. pylori were examined in gastric contents of some cases. Bacteriological features of isolated strains of C. pylori were identical to the NCTC strain. C. pylori was the most dominant organism in gastric contents at any pH level. Detection rates of C. pylori by bacteriological culture were 96% in gastric ulcer, 100% in duodenal ulcer, 80% in coexisting gastroduodenal ulcer, 84% in gastroduodenal ulcer with gastritis, 70% in gastritis, 100% in gastric polyps and 100% in gastric cancer, and the percentages recognized by histological studies were 81, 100, 100, 84, 71, 67, and 57%, respectively. The values in healthy controls were 55% by histological and bacteriological methods (P less than 0.001 compared with overall ulcer patients). These results supported the close association between C. pylori and gastroduodenal diseases.

Adult↗
PubMed1989

Effects of 5 beta-chol-3-en-24-oic acid, and lithocholic acid and its sulfates on prostaglandin E2 output in perfusion of the rat colon.

The effects of bile salts on the output of prostaglandin E2(PGE2) were studied in rats by colonic perfusion. Bile salts and their concentrations in infusates were as follows; chenodeoxycholic acid sodium salt (CDCNa), sulfolithocholic acid disodium salt (SLCNa) and sulfotaurolithocholic acid disodium salt (STLCNa) were at 1 mmol/l, lithocholic acid sodium salt (LCNa) was at 0.6 mmol/l, 5 beta-chol-3-en-24-oic acid sodium salt (delta 3Na) was at 0.006 mmol/l, and sulfoglycolithocholic acid disodium salt (SGLCNa) was at 0.8 mmol/l. Median values of PGE2 outputs were 40.9, 52.4, 65.5, trace, 7.6, 9.8 and 9.8 pg/10 min/cm in the CDCNa, LCNa, delta 3Na, SLCNa, STLCNa, SGLCNa and control groups, respectively (control vs CDCNa, LCNa, delta 3Na, SLCNa group, p less than 0.01 by median test). There was such a dissociation in PGE2 output and electrolyte concentration in the perfusates that high concentration of Na+ and Cl- ions was observed only in the SGLCNa group (p less than 0.01 by t-test compared with the control group), whereas in the remainder of the groups substantial net movement of electrolytes and water was not observed. Light microscopy showed no evidence of morphological damage in any group. These results indicated that CDCNa, LCNa and delta 3Na increased PGE2 outputs in the colon at low concentration without functional or morphological changes.

Animals↗
PubMed1989

Stimulation parameters influencing climbing fibre induced long-term depression of parallel fibre synapses.

It has been demonstrated that conjunctive stimulation of cerebellar climbing fibres and parallel fibres induces a long-term depression (LTD) of the transmission from the activated parallel fibres to Purkinje cells. The aim of the present investigation with extracellular recordings from single Purkinje cells was to study factors influencing the induction of LTD. Climbing fibres and parallel fibres were conjunctively stimulated with a constant time interval between the climbing fibre and parallel fibre stimuli. It was demonstrated that the maximal effective time interval between climbing fibre and parallel fibre activation for induction of LTD was between 125 and 250 ms. It was also demonstrated that the amplitude of the LTD depended on the stimulation frequency. The LTD induced by conjunctive stimulation at 1 and 2 Hz had a similar size whereas the LTD induced by 4 Hz was stronger.

Animals↗