Ouabain, a specific inhibitor of active cation transport across cell membrane, was applied topically to brain surface of cats. The cerebral cortex to which 10(3) M ouabain was applied showed a spongy state, which was ultrastructurally revealed to be swelling of the neuronal cell processes, especially of dendrites. Astrocytes did not show swelling even in the most severely affected lesions. There was a marked increase in sodium with a slight increase of water in the cortex treated with 10(3) M ouabain. No evidence of increased vascular permeability was noted in the cortex, morphologically or biochemically. Electron microscopic cytochemistry to detect the sodium ion revealed that the increased sodium in the cortex accumulated in the swollen neuronal cell processes. It is speculated that neuronal rather than astocytic elements might be highly dependent upon active cation transport, and that intracellular oedema in the brain tissue responsible for impairment of active cation transport might be related primarily to neuronal elements.

Animals↗

PubMed1977

Failure of exogenous insulin to inhibit insulin secretion in man.

In order to explore whether or not the negative feedback mechanism of insulin per se on insulin secretion exists in man, changes in plasma C-peptide immunoreactivity (CPR), as an index of pancreatic B cells secretory function, were studied in 6 nonobese healthy volunteers in the presence of high circulating levels of exogenous insulin. 10% glucose was infused concurrently so as to maintain blood sugar at the basal level. The insulin-glucose infusion was maintained for 120 minutes, achieving mean plasma levels of 140-180 mu1/ml. After this period, the insulin infusion was continued at the same rate for an additional 10 minutes while the glucose was omitted. Despite the elevated level of circulating insulin, no significant change in plasma CPR concentration was observed so long as the blood sugar was maintained at the basal levels. Following cessation of the glucose infusion, the plasma CPR levels declined with a decrease in blood sugar level. Under the conditions of the present study, no inhibitory effect of exogenous insulin on the secretory function of the B cells was noticed.

Adult↗

PubMed1977

Synaptic vesicle fraction devoid of adenosine triphosphatase activity from bovine caudatolenticular nuclei and thalamus.

1. As a part of studies on the mechanism by which catecholamines are released from the nerve terminals, the synaptic vesicle fraction was isolated from bovine caudatolenticular nuclei and thalamus by differential centrifugation essentially according to the method of Kadota and Kadota (17). 2. Further centrifugation on a sucrose density gradient of the synaptic vesicle fraction by the method of Whittaker et al. (1) yielded white materials on the upper portion of 0.4 M sucrose, which consisted of vesicles averaging 600-800 A in diameter, and did not show Mg2+-dependent ATpase activity. On the other hand, the denser materials centering on 0.6 M sucrose, consisting of a mixture of microsomes and synaptic vesicles of 400-500 A diameter, showed an ATpase activity activated by either Mg2+ or Ca2+ but not inhibited by ouabain. 3. The white materials on 0.4 M sucrose were almost free of mitochondria, but they contained a large amount of non-heme iron, as reported elsewhere (2). Furthermore, the protein components analyzed on SDS-polyacrylamide gels were similar to those already reported for purified synaptic vesicles (3). 4. Based on these results, the white materials were assumed to be synaptic vesicles devoid of Mg2+-dependent ATPase activity.

Adenosine Triphosphatases↗

PubMed1977

Effects of volleys in cortico-spinal tract fibres on ventral spino-cerebellar tract cells in the cat.

Both excitation and inhibition has been found in cells of origin of the ventral spino-cerebellar tract (VSCT) to be evoked by volleys in cortico-spinal fibres. The earliest EPSPs and IPSPs had features of disynaptically evoked postsynaptic potentials; these were, however, found only in a small proportion of cells and polysynaptic EPSPs and IPSPs were dominating . Postsynaptic potentials evoked in VSCT cells from primary afferents were effectively facilitated by cortico-spinal volleys. The cortico-spinal effects on VSCT cells may thus well be mediated by the same interneurones which mediate their excitation or inhibition from the periphery and which could evoke similar postsynaptic potentials in motoneurones. Generally all the observation are in keeping with the hypothesis (Lundberg 1971) that VSCT cells monitor transmission through interneurones interposed in various reflex paths to motoneurones.

Animals↗

PubMed1977

Factors influencing absorption and excretion of drugs. VI. Effect of sodium cholate on in situ rat intestinal absorption of buformin.

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Animals↗

PubMed1977

Hemolysis and morphological changes in rat erythrocytes with mercurials.

Effects of mercurials on rat erythrocytes were studied morphologically using an electron microscope. In the scanning study, the normal biconcave shape of the erythrocytes was changed to rugged surface spherocytes when mercuric chloride was added to the erythrocyte suspension. Methylmercuric chloride produced an irregularity of cell shape with spicules including the final stage of spherocytes. p-Chloromercuribenzoic acid formed crenated cells with protrusion, then spherocytes. By a carbon replica technique, it was revealed that control erythrocytes had a granular surface structure; however the surface of mercuric chloride-treated and methyl-mercuric chloride-treated erythrocytes appeared less granulated. By a negative staining technique, severe damage was observed on the erythrocytes lysed by mercurials. As a decrease in content of reduced glutathione, inhibition of glucose-6-phosphate dehydrogenase activity and formation of methemoglobin in erythrocytes treated with mercurials to induce hemolysis were not observed, it was concluded that the hemolysis induced by mercurials was not due to a disturbance in erythrocyte metabolism but rather to the direct action of mercurials on the cell membrane.

Animals↗

PubMed1977

Insulin releasing activity of gastrointestinal glucagon-like immunoreactive materials in perfused rat pancreas.

Insulin-releasing activity of porcine gastrointestinal glucagon-like immunoreactive materials purified by affinity chromatography was examined in the perfused rat pancreas. When glucose concentration of the perfusate was raised from 60 to 100 mg/dl, augmented insulin release was observed. The mean incremental area of immunoreactive insulin (sigma delta IRI) during the first 10 min thus observed was 19.07 +/- 3.76 ng/10 min. Pancreatic glucagon and the extract from the gastric fundus showed the enhancement of insulin release in this system when they were added to the perfusate at the rate of 100 ng/min for 5 min; delta IRI were 41.92 +/- 8.47 and 71.70 +/- 18.09 ng/10 min, respectively, which were significantly higher than that of 100 mg/dl of glucose alone. However, no significant difference in the insulinogenic activity was noticed between the extracts from the small intestine and the control. These results suggest that the extract from the gastric fundus has insulinogenic activity similar to that of pancreatic glucagon.

Animals↗

PubMed1977