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Biomedical subjects

T Gotow

Publications and source records attributed to T Gotow.

62 records · Page 4Linked to original sources
PubMed1980

Excitatory and inhibitory effects of histamine on molluscan neurons.

Histamine elicited depolarization (excitation) in some neurons and hyperpolarization (inhibition) in other neurons of the central nervous system of the marine mollusc, Onchidium verruculatum. The histamine sensitive region was along the axon at some distance from the soma. H1-receptor blockers (SA-97 and mepyramine) suppressed the excitatory (H1) response without affecting the inhibitory (H2) response, while H2-receptor blockers (burimamide and metiamide) suppressed the H2-response without affecting the H1-response. The H1-response was associated with a marked increase in membrane conductance and was blocked by removal of the external Na. The H2-response consisted of a hyperpolarization without much change in conductance, compared with the hyperpolarization of same amplitude produced by glutamate in the same neuron. Passive polarization of the membrane and reduction of Cl concentrations to 1/5-1/25 caused no significant change in H2-response. The H2-response was slightly suppressed in K-free saline. Thus, it seems difficult to account for the hyperpolarization only by an increase in K or Cl conductance. Complete removal of Na and addition of ouabain blocked the H2-response, suggesting a contribution of an electrogenic Na-pump to the hyperpolarization. However, in 20 mM Na saline with or without K, histamine still caused clear hyperpolarization. In this solution, the histamine response was not affected by ouabain. Although it is difficult to exclude the possibility that an increase in K conductance may be responsible for the hyperpolarization, it is tentatively proposed as a hypothesis that the H2-response involved some active transport mechanism, different from a ouabain-sensitive electrogenic Na-pump.

Animals↗
PubMed1980

An analysis of histamine-induced inhibitory response in molluscan neurons.

Mechanisms of the histamine-induced inhibitory response (the H2-response) in neurons of the marine mollusc Onchidium, were further investigated following the preceding paper. The H2-response in normal saline was blocked by ouabain, but the response recovered after a short exposure to Na-free solution containing ouabain. The recovery was only transient in the continuous presence of ouabain. When external Na was reduced to about 1/8 normal concentration (60 mM), the H2-response became sensitive to removal of external Ca, but insensitive to ouabain. The suppressing effect of Ca removal and the recovery by Ca readmission appeared very slowly. However, in about 1/3 normal Na concentration (150 mM) the H2-response was suppressed by removal of the Ca, only in the presence of ouabain. The Na-gradient may be regulated by the ouabain-insensitive transportk, such as a Na-Ca exchange in addition to the ouabain-sensitive Na-pump. The Na-Ca exchange probably dominates over the ouabain-sensitive Na-pump only when passive Na-influx is reduced in a low external Na concentration. The H2-response was markedly inhibited by DNP (5 X 10(-4)M) and cyanide (2 X 10(-3)M), while the hyperpolarization produced by glutamate, which was accompanied by a large reduction of membrane resistance, was not affected by these metabolic inhibitors. Over a wide range of external Na concentrations, the membrane potential was lower in presence than in the absence of external Ca. This may be explained by the hypothesis that there is an electrogenic Na-Ca exchange in which Ca-influx is coupled with Na-efflux. According to a similar hypothesis, the H2-response is produced by the transport system in which Ca-efflux is coupled with Na-influx and the system is controlled by the transmembrane Na gradient.

Animals↗
PubMed1980

Fine structure of ependymal cysts in and around the area postrema of the rat.

Peculiar cells forming cysts were observed in the area postrema and sometimes also in the choroid plexus and the tela chorioidea near the area postrema, and were studied in detail by electron microscopy. The cytological features of the cyst cell and its junctional relationship to neighboring cells imply that cyst cells are derived from ependymal and choroid epithelial cells. The cyst cells usually contact directly the perivascular spaces of postremal, choroidal or pial capillaries, where the cytoplasm is often considerably attenuated. The cystic lumen is commonly filled with a flocculent material. The limiting membrane of the cystic lumen, which frequently bears cilia and microvilli, has the same thickness as the surface cell membrane. In many cases the cyst is surrounded by the cytoplasm of a single cell. In some cases, however, two cells participating in the formation of the cyst, although one is only a slender process and joined by a zonula occludens with the main cyst cell. Horseradish peroxidase (HRP) injected into the cerebrospinal fluid (CSF) space failed to enter the cystic lumen. A possible significance of the cyst in relation to the CSF and blood circulation was considered.

Animals↗
PubMed1979

Fine structure of the ependyma and intercellular junctions in the area postrema of the rat.

Ependymal cells and their junctional complexes in the area postrema of the rat were studied in detail by tracer experiments using horseradish peroxidase (HRP) and colloidal lanthanum and by freeze-etch techniques, in addition to routine electron microscopy. The ependyma of the area postrema is characterized as flattened cells possessing very few cilia, a moderate amount of microvilli, a well-developed Golgi apparatus and rough endoplasmic reticulum. Numerous vesicles or tubular formations with internal dense content were found to accumulate in the basal processes of ependymal cells; the basal process makes contact with the perivascular basal lamina. It is suggested that the dense material in the tubulovesicular formations is synthesized within the ependymal cell and discharged into the perivascular space. The apical junctions between adjacent ependymal cells display very close apposition, with a gap of 2--3 nm, but no fusion of adjacent plasma membranes; they thus represent a transitional form between the zonulae adhaerentes present in the ordinary mural ependyma and the zonulae occludentes in the choroidal epithelium. A direct intercommunication between the ventricular cerebrospinal fluid (CSF) and the blood vascular system indicates that a region exists lacking a blood-ventricular CSF barrier.

Animals↗