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H Oka

Publications and source records attributed to H Oka.

At least 559 records · Page 31Linked to original sources
PubMed1976

Effects of stimulation of the midbrain reticular formation upon thalamo-cortical neurones responsible for cortical recruiting responses.

1. In lightly nembutalized cats, effects of high frequency (60-100/sec) repetitive stimulation of the midbrain reticular formation (RF) were tested upon the thalamo-cortical (T-C) neurones which project from the anterior ventral (VA) nucleus of the thalamus and its vicinities to the parietal association cortex and convey impulses responsible for cortical recruiting and spindling-like responses. 2. Tonic maintained or rhythmic grouped firings of the T-C neurones recorded as extracellular units with microelectrode in the thalamus were in the majority suppressed by high frequency RF stimulation during and often for a short time after the stimulation, and they showed later tonic discharges for many seconds or minutes. Intracellular recording from the T-C neurones revealed hyperpolarizing potential changes corresponding to the suppression on high frequency RF stimulation. Field potential analysis in the VA nucleus indicated that the hyperpolarization is ascribed at least in part to IPSPs elicited in the T-C neurones. Responses in some other types of thalamic neurones to the RF stimulation were exemplified to be compared and related with those of the T-C neurones. 3. Desynchronization of the parietal electrocorticogram coincided with the suppression of the T-C neurones and lasted for the time of the later tonic discharges, which contrasted with the rhythmic grouped discharges of the T-C neurones in association with recruiting and spindling-like responses of the cortex. Relations between the thalamo-cortical recruiting system and the ascending reticular activating system were discussed.

Animals↗
PubMed1976

Electrophysiological studies on the cerebellocerebral projections in monkeys.

1. Responses evoked by stimulation of the cerebellar and thalamic nuclei were recorded by microelectrodes introduced at various depths in the cerebral cortex of monkeys (Macaca mulatta) under light Nembutal anaesthesia. 2. Stimulation of the medial (fastigial) cerebellar nucleus produced, at a latency of 4-5 msec, deep thalamo-cortical (T-C) responses (surface positive-deep negative potentials) mainly in the medial part of the precentral gyrus (area 4, "motor area for hindlimb") and in the superior parietal gyrus (area 5) on both contralateral and ipsilateral sides to the nucleus stimulated. 3. Stimulation of the lateral (dentate) cerebellar nucleus elicited, at a latency of about 3 msec, superficial T-C responses (surface negative-deep positive potentials) predominately in the lateral part of the precentral gyrus (area 4, "motor area for forelimb and face") and in the rostromedial part of the gyrus (area 6, premotor area) on the contralateral side. 4. Stimulation of the interpositus cerebellar nucleus set up superficial T-C responses chiefly in the motor area between those influenced by the medial and the lateral cerebellar nucleus stimulation and also in the premotor area on the contralateral side. 5. The respective areas responsive to the medial, interpositus and lateral nucleus stimulation overlapped considerably each other in the motor cortex. 6. Comparison of the responses in the cortex induced by stimulation of the cerebellar and thalamic nuclei indicated different relay portions in and around the VA-VL region of the thalamus for the superficial and the deep T-C responses respectively. 7. Functional implications of the results were discussed in referring to the cerebellocerebral projections in cats.

Animals↗
PubMed1976

Increased urinary excretion of L-xylulose in patients with liver cirrhosis.

The urinary excretions of L-xylulose, xylitol and D-glucarate after the oral administration of glucuronolactone (5 g) were measured in normal healthy persons, patients with diabetes mellitus, acute hepatitis in recovery stage, chronic hepatitis and liver cirrhosis. In normal subjects, the mean value of L-xylulose excretion was 14.6 +/- 1.4 mumol/2 h with a range from 6.5 to 21.8. Marked increase of L-xylulose excretion was observed in cirrhotic patients, the mean value was 97.1 +/- 19.8 with a range from 22.0 to 236.6. Though some cases of acute and chronic hepatitis showed higher values than the normal range, no case exceeded 50 mumol/2 h. The urinary excretion of xylitol in cirrhotic patients was also higher than normal no increase was observed in D-glucarate excretion. The values of L-xylulose excretion in cirrhosis were correlated with the values of serum total bilirubin, albumin, albumin/globulin ratio, lactate dehydrogenase and prothrombin time. These findings indicate that the measurement of L-xylulose in urine after the oral glucuronolactone loading provides a useful tool for evaluation of the severity of liver cirrhosis.

Acute Disease↗
PubMed1976

Impairment and restoration of response to TSH in dog thyroid slices after treatment with phospholipase A and lubrol PX.

Incubation of dog thyroid slices with phospholipase A (10-40 U/Ml) or Lubrol PX (0.08-0.4%) caused a diminution in the subsequent TSH effect on the tissue cyclic AMP level and glucose oxidation. The same treatment had no effect on the basal level of these parameters. When the phospholipase A or Lubrol PX-treated slices were rinsed intensively with a Krebs-Ringer bicarbonate buffer and then incubated at 37degreesC in the same buffer for a further 1 to 3 hours, responsiveness to TSH recovered progressively reaching almost completely that of the control slices. Again, these procedures were without any significant effect on the responsiveness of the control slices. The above results together with those reported previously suggest strongly that phospholipids are an essential component of the plasma membrane system by which TSH stimulates adenylate cyclase activity. In addition, these essential lipids in the membrane appear to be renewed rather efficiently in this tissue, thus securing the functional integrity of the thyroid in the face of various deleterious situations.

Animals↗
PubMed1976

Inhibition of insulin release by synthetic rat C-peptide II in isolated rat islets.

The effect of synthetic rat C-peptide on glucose-induced insulin release was studied in isolated islets of rat pancreas. Addition of rat C-peptide II to the medium inhibited glucose-induced insulin release from islets by 30 to 40 percent. Rat C-peptide I, human connecting peptide and bovine, porcine and canine C-peptides had no significant effects on insulin release from islets of rat pancreas.

Animals↗
PubMed1976

Effects of mannoheptulose and DL-glyceraldehyde on glucose induced insulin release and adenosine 3',5'-monophosphate levels in isoalted islets of rat pancreas.

The effects of mannoheptulose and DL-glyceraldehyde on glucose-induced insulin release and cycli AMP levels in islets isolated from rat pancreas were investigated. Mannoheptulose inhibition on glucose-induced insulin release was observed after only 5-min incubation period, indicating an inhibitory effect on the early phase of insulin release. This inhibition on insulin release was accompanied with the simultaneous depression of cyclic AMP levels in islets. By the addition of DL-glyceraldehyde to the medium in which glucose and mannoheptulose were present, the depressed cyclic AMP levels in islets were recovered to the control level completely but the restoration of insulin release in the early phase was not complete. In the absence of glucose, DL-glyceraldehyde did not demonstrate a significant increase of insulin release during 5 min incubation, though a marked stimulation was observed after 30-min incubation. Cyclic AMP levels in islets were not affected by DL-glyceraldehyde. When DL-glyceraldehyde was added to the medium with glucose, significant inhibition of glucos-induced insulin release in its early phase was observed without the reduction of cyclic AMP levels in islets. From these findings, the following possibilities are suggested and discussed. 1. Maintenance of the cyclic AMP levels in islets is a necessary but insufficient condition for glucose-induced insulin release particularly for its early phase. 2. Glucose-induced insulin release seems to depend on both the binding of glucose with glucoreceptor and the supply of some metabolites. Mannoheptulose inhibits both mechanisms. DL-glyceraldehyde may supply metabolites but competitively inhibit the binding of glucose to the glucoreceptor.

Animals↗
PubMed1976

Effects of concanavalin A and neuraminidase on cyclic AMP levels and 14C-1-glucose oxidation in dog thyroid slices.

Treatment with concanavalin A at 100 micron/ml or higher concentrations significantly increased 14C-1-glucose oxidation in dog thyroid slices as reported in other tissues. This treatment exerted no effect on tissue cyclic AMP levels. Neuraminidase at the same concentrations also had similar effects on these parameters. Neither concanavalin A nor neuraminidase at the concentrations up to 100 microng/ml had the TSH effect on both tissue cyclic AMP and 14C-1-glucose oxidation. These results indicate that modification of carbohydrate moieties of glycoproteins on the cell surface may cause an increase in glucose metabolism without any critical effect on cyclic AMP system and in the process of TSH response.

Animals↗