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Biomedical subjects

K Ohtsuka

Publications and source records attributed to K Ohtsuka.

At least 199 records · Page 11Linked to original sources
PubMed1990

Direction-selective saccadic-burst neurons in the fastigial oculomotor region of the macaque.

Discharges of 68 neurons, recorded from the oculomotor region of the fastigial nucleus (FN) of the macaque, were characterized by a burst which started approximately 20 msec prior to the onset of a saccade in a direction contralateral to the recording site. These fastigial neurons also paused before saccades in their nonpreferred direction and then discharged with a subsequent burst. All units were spontaneously active but the tonic level of activity did not reflect eye position. They aggregated within the oculomotor region and the firing of 57 units (83.8%) was suppressed by stimulation of vermal lobule VII. Tonic discharges of six other units were closely related to eye position and located rostral to the burst units. Discharges of 16 units increased during the ipsilateral phase of sinusoidal head rotation and those of 50 units increased during contralateral head rotation. These neurons did not show saccade-related activity. They were widely scattered in the rostral and central portions of the FN. None of these units was inhibited by stimulation of vermal lobule VII.

Animals↗
PubMed1990

Establishment of functional epithelial cell lines from a rat thymoma and a rat thymus.

Seven clonal epithelial cell lines from a thymoma of an (ACI/NMs x BUF/Mna)F1 rat and seven clonal epithelial cell lines from an ACI/NMs rat thymus were established in a medium containing 1 microM dexamethasone (DM) and were characterized cytologically. Long-term treatment of DM stabilized the epithelial nature of these epithelial cells irreversibly. The established cell lines showed a polygonal shape, were positively stained with antikeratin antiserum and had tonofilaments and desmosomes. Species of their keratin peptides were the same as those of normal thymic epithelial cells in primary cultures. The cell lines were positively stained with Th-4 monoclonal antibody which preferentially stains the medullary epithelial cells of the thymus, but not with Th-3 which preferentially stains the subcapsular and cortical epithelial cells of the thymus. The cells from the rat thymoma were much larger than those from the normal thymus, as reflected in their primary cultures. No transformed phenotypes, such as high growth rate, high saturation density, anchorage independency, low serum dependency and so on, were found in the cell lines from the thymoma as in the cell lines from the normal thymus by in vitro assays. DNA synthesis of the thymic lymphocytes was stimulated by culturing with a line of rat thymoma with no lectins. Thymic lymphocytes strongly bound on the cell lines from the thymoma and changed the shape of the cells. These cell lines may be useful to investigate the mechanism of thymomagenesis and the interactions between epithelial cells and thymocytes in the rat thymoma.

Animals↗
PubMed1990

Availability of 4'galactosyllactose (O-beta-D-galactopyranosyl-(1----4)-O-beta-D-galactopyranosyl-(1----4)- D-glucopyranose) in rat.

O-beta-D-Galactopyranosyl-(1----4)-O-beta-D-galactopyranosyl-(1----4)-D- glucopyranose (designated as 4'GL) is produced from lactose by Cryptococcus laurentii. The influence of chronic ingestion of 4'GL on body weight gain, organ weight, serum lipids, and liver lipids was investigated in rats. The body weight gains of the 5% and 10% 4'GL-diet groups were higher than that of the control group. Food intake and fecal dry weight were significantly increased (p less than 0.05) by 4'GL feeding. The 4'GL diet produced a significant increase (p less than 0.01) in the wet weight and contents of both the cecum and the colon. However, no significant increase was observed in the weight of the stomach, small intestine, liver, or other organs. The effects of 4'GL on serum and liver lipid levels were not observed in this experiment. The digestion of 4'GL was measured in vitro using the artificial gastric juice, alpha-amylase of human saliva, alpha-amylase of hog pancreas, and mucosa of rat intestine. 4'GL was not hydrolyzed by these enzymes. Long-term ingestion of 4'GL did not cause any induction of 4'GL hydrolyzing enzyme activity in the rat small intestine.

Animals↗
PubMed1989

Neurofibromatosis with spinal paralysis due to arteriovenous fistula.

A case of neurofibromatosis with spinal paralysis due to arteriovenous fistula is reported. Preoperatively, the appropriate diagnosis was missed because angiography had not been performed. Postoperative angiography disclosed that an arteriovenous fistula formed a tumor-like mass, and that a part of the mass had invaded the spinal canal, compressing the spinal cord. It is concluded that the possibility of an arteriovenous fistula should be kept in mind in neurofibromatosis patients with spinal cord symptoms.

Adult↗
PubMed1989

Loading of fura-2/AM with an aid of DFP on single smooth muscle cells prepared from guinea pig taenia coli.

Procedures for loading fura 2 acetoxymethyl ester (fura 2/AM) into smooth muscle cells isolated from guinea pig taenia coli have been investigated. It was difficult to load these cells with fura 2 in the absence of diisopropylfluorophosphate (DFP). The presence of DFP, a potent cholinesterase (ChE) inhibitor during the loading, significantly enhanced the incorporation of the fura 2 into the cells. More than 80% of the single cells treated with DFP and fura 2/AM were viable. DFP did not affect the ability of the cell to shorten in response to either Ca2+ or carbachol (CCh). The single cells contracted transiently with caffeine and the intracellular Ca2+ concentration increased simultaneously. The results indicate that the amount of fura 2/AM incorporated into the single smooth muscle cells depends on the activity of ChE or various serine proteases located outside the cells and suppression of these enzymes induces more efficient incorporation, which permits shorter incorporation periods. Since the presence of DFP may shorten the incubation time significantly, the viability of these cells is improved. The procedure might be applicable for measuring simultaneously the contraction of cells and the behavior of intracellular Ca2+ in the same cells.

Animals↗
PubMed1989

Accuracy of memory-guided saccades.

Accuracy of saccades toward a remembered target positions in the dark (memory-guided saccades) was studied in 11 normal subjects. The subjects were instructed to execute saccades with amplitudes of 20, 40, 60, and 80 degrees, centering on the primary position. Saccades were initially performed for 30 s with visual fixation targets. The targets were then switched off. The subjects continued saccades in the dark with the given amplitude. Most memory-guided saccades overshot the target. Saccades with an amplitude error of 12.7 +/- 7.3 degrees (mean +/- SD) were followed by corrective saccades, while no corrective saccades occurred following saccades with an error of 4.3 +/- 4.0 degrees. The accuracy of initial memory-guided saccades decreased with time. However, the amplitude of the memory-guided saccades was corrected when the error was beyond about 5 degrees. These results suggest that memory-guided saccades are not repetitions of visually guided saccades, but nonvisual error signals relate to the control of eye movements in the dark.

Adult↗
PubMed1989

[Cellular thermosensitivity].

(1) modes of expression of thermosensitivity and theoretical interpretation of thermal dose, (2) differential thermosensitivities between strains of cells and the possible correlation to heat shock proteins and their syntheses, (3) cell phase responses to hyperthermia, (4) low hyperthermia and the induction of thermotolerance, (5) comparative thermosensitivities at the temperatures between below and above 42.5 degrees C -43 degrees C, (6) Arrhenius plot and mean cellular lethal heating periods, (7) step-up heating and the thermotolerance induction, (8) step-down heating and the thermoenhancement, (9) fractionated high hyperthermia and the thermotolerance induction and (10) modification of thermosensitivity by chemical substance including anticancer drugs; are compactly reviewed mainly on cell level.

Cell Cycle↗
PubMed1989

Effects of N-(2,6-dimethylphenyl)-8-pyrrolizidineacetamide hydrochloride hemihydrate on the ventriculo-atrial conductivity of accessory pathways.

The purpose of this study was to examine the effects of N-(2,6-dimethylphenyl)-8-pyrrolizidineacetamide hydrochloride hemihydrate (SUN 1165), a newly developed antiarrhythmic agent belonging to class Ic, on the ventriculoatrial (VA) conductivity of accessory pathways and paroxysmal supra-ventricular tachycardia (PSVT). Twelve patients with accessory pathways were examined by standard electrophysiologic technique before and after a single oral dose of SUN 1165 (100 mg). 1 h after administration, SUN 1165 blocked VA conduction of the accessory pathway in six of twelve patients and prevented the induction of PSVT in six of seven cases. In the cases in which VA block did not occur, the VA interval prolonged (from 178 +/- 7 to 190 +/- 11 ms, p less than 0.05), and the effective refractory period of VA conduction was also increased (from 273 +/- 10 to 318 +/- 15 ms. p less than 0.05). SUN 1165 also prolonged the conduction time in normal conduction systems (AH and HV intervals and QRS duration), but the degree of the prolongation was moderate and not dangerous. There was no adverse effect. These results indicate that SUN 1165 is a potent and safe antiarrhythmic agent, and useful for preventing or stopping PSVT by blocking or depressing VA conduction through accessory pathways.

Administration, Oral↗
PubMed1988

Accommodation and convergence insufficiency with left middle cerebral artery occlusion.

We studied accommodation and vergence eye movements in a patient with a left middle cerebral artery embolism. Accommodation was monitored by an infrared optometer with the accommodative target being controlled by a microcomputer. Computed tomography showed low-density areas in the left cortex, with intact brainstem. The patient had convergence palsy and accommodation abnormalities. The amplitude of the accommodative responses was reduced and the accommodation velocity was markedly lowered. Our results further substantiate the neurologic relationship between the cerebral cortex and accommodation and convergence.

Accommodation, Ocular↗
PubMed1988

Inhibitory action of Purkinje cells in the posterior vermis on fastigio-prepositus circuit of the cat.

Neuronal connections between the posterior vermis including the fastigial nucleus and the prepositus nucleus were studied with electrophysiological and neuropharmacological methods in the cat. Spontaneous discharges of neurons in the prepositus nucleus were depressed by microstimulation of the contralateral vermis, lobule VI. This depressive effect was blocked by the injection of bicuculline into the caudal part of the fastigial nucleus. These prepositus neurons also showed long-lasting poststimulus facilitation following microstimulation of the contralateral fastigial nucleus. These prepositus neurons were reciprocally connected with neurons in the contralateral fastigial nucleus. These findings suggest that Purkinje cells in lobule VI of the vermis depress propositus neuronal activity through the fastigial nucleus and that the reciprocal connectivity between the prepositus and fastigial nuclei generates a significant background facilitation in the two nuclei.

Animals↗
PubMed1988

Respiratory fluctuations of the human pupil.

We simultaneously recorded respiration and pupil size in six normal subjects with an age range of 23-40 years (mean = 30.1), to study the relationship between the respiratory rhythm and changes in pupil size. In all subjects, respiratory fluctuations of the pupil (inspiratory mydriasis and expiratory miosis) were observed during normal spontaneous respirations. The amplitude of these pupillary changes was closely proportional to the tidal volume.

Adult↗
PubMed1988

Rapid phosphorylation of MAP-2-related cytoplasmic and nuclear Mr 300,000 protein by serine kinases after growth stimulation in quiescent cells.

Antibody against brain microtubule-associated protein 2 (MAP-2) immunoprecipitated Mr 300,000 and 80,000 proteins of cultured fibroblasts and kidney cells. These proteins were not appreciably phosphorylated in quiescent cells, but were rapidly phosphorylated after growth stimulation by insulin, epidermal and fibroblast growth factors, transferrin, phorbol ester and diacylglycerol in the presence of Ca2+, in a manner similar to that of MAP-1-related Mr 350,000 protein (J. Cell Biol. 100, 748-753). A Ca2+ ionophore, which is known to make the quiescent cell competent but not to enter into the growth cycle, did not induce the phosphorylation. In a chase experiment, decay half lives of labeled phosphoproteins were 5 h for Mr 350,000 and 300,000 proteins, and 1.5 h for Mr 80,000 protein. On subcellular fractionation, phosphorylated Mr 350,000 and 300,000 proteins were detected first mainly in the cytoplasm and then in the nucleus, while Mr 80,000 phosphoprotein was consistently detected in the cytoplasm. The phosphorylation of these proteins occurred on serine residues after stimulation with various factors. Thus, the phosphorylation of cytoskeleton-associated Mr 350,000 and 300,000 proteins by serine kinases seems to be a common second process after growth stimulation and to link cytoplasmic and intranuclear events.

Animals↗
PubMed1988

Instability of eye position in the dark in cerebellar degeneration.

Fourteen cases of spinocerebellar degeneration were examined. While the patients attempted to keep their eyes in the primary position, horizontal eye movements were recorded for 1 min in total darkness by infrared reflection oculography. Instability of eye position in the dark was observed in 10 patients. The range of the eye position error was 3-6 degrees in 6 patients, 6-10 degrees in 3 patients and over 10 degrees in 1 patient. These results indicate that the cerebellum plays an important role in extraretinal (nonvisual) eye position control.

Adult↗
PubMed1988

Nonvisual eye position control in a patient with ocular lateropulsion.

For elucidating the nonvisual eye position control system, we studied the accuracy of saccades toward the remembered position (memory-guided saccades) in a patient with ocular lateropulsion having tonic bias of the eye position. Although the saccadic dysmetria caused by ocular lateropulsion was recorded during memory-guided saccades in the same manner as visually guided saccades, the eyes reached precisely the intended position by corrective saccades. The mean latency of corrective saccades was significantly longer than that of corrective saccades observed for visually guided saccades. This long latency of corrective saccades supports the assumption that feedback information of the eye position is a signal generated by orbital afferents rather than a copy of the motor command.

Eye Movements↗
PubMed1988

[Influence of total pancreatectomy on the secretion of human growth hormone and the endocrine pancreas].

To evaluate the effect of total pancreatectomy on the secretion of human growth hormone, twenty-six patients undergoing total pancreatectomy and twelve healthy subjects (controls) were investigated. Blood glucose (BG), plasma insulin (IRI), C-peptide (CPR), immunoreactive glucagon (IRG) and human growth hormone (HGH) levels were determined. In the glucose tolerance test, the mean basal blood glucose level in the patients before operation was significantly higher than the level in the controls. The basal blood glucose level in the patients after operation was still higher than the level before operation. The responses of IRI, CPR, and IRG secretion after arginine infusion in the patients before operation were less than those in the controls. After operation, arginine infusion did not alter the levels of IRI, CPR and IRG. The mean basal HGH levels were not significantly different between the controls and the patients before and after operation. However, a statistically significant correlation was shown between the basal values of plasma HGH and those of plasma IRI in the patients after operation. Thus, it suggested that the basal secretion of HGH is closely related to the exogenous plasma insulin levels in the pancreatectomized patients. After arginine infusion, the HGH levels in the patients before operation were lower than the those in the controls, but insignificant. After operation, mean HGH levels were significantly lower than those before operation. These findings suggested the absence of pancreatic endocrine function caused by total pancreatectomy resulted in decreased responses of HGH secretion after arginine infusion.

Adult↗
PubMed1987

Effect of DFP on loading of fura 2/AM and quin 2/AM into single smooth muscle cells prepared from guinea pig taenia coli.

The effect of diisopropyl fluorophosphate (DFP), a potent cholinesterase (ChE) inhibitor, on loading quin 2 acetoxymethyl ester (quin 2/AM) and fura 2/AM into smooth muscle cells isolated from guinea pig taenia coli was investigated spectrofluorometrically. The presence of DFP during the loading permitted the incorporation of quin 2 into the cells, so that it became possible to measure intracellular Ca2+ concentrations using the ester of this dye. Also, DFP significantly enhanced the incorporation of fura 2 into the cells. These results indicate that loading of quin 2/AM and fura 2/AM into the smooth muscle cells may depend on the suppression of ChE or various serine protease activities outside cells.

Aminoquinolines↗