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Biomedical subjects

T Minami

Publications and source records attributed to T Minami.

At least 343 records · Page 19Linked to original sources
PubMed1986

Ionic basis for the electroresponsiveness of guinea-pig ventromedial hypothalamic neurones in vitro.

The difference between the ionic bases for electroresponsiveness in the three types of neurone in the ventromedial hypothalamic nucleus (v.m.h.) were studied in in vitro brain slice preparations of the guinea-pig. The current-voltage relationships in all three types of neurone showed anomalous rectification. Application of tetrodotoxin (TTX) abolished the fast action potentials in all three types of cell. In type A cells, injections of outward current pulses did not evoke spikes when the cells were perfused with TTX alone, but the addition of tetraethylammonium chloride elicited broad spikes. In type B and C cells, broad spikes could be evoked with TTX alone. These results suggest the presence of a minimal high-threshold Ca2+ current in type A neurones, and a more prominent one in type B and C neurones. In type B neurones, Ca2+ conductance blockage with Mn2+ or Co2+, or replacement of Ca2+ by Mg2+, abolished the low-threshold response (l.t.r.). Substitution with Ba2+ did not increase the duration of the l.t.r. significantly, suggesting that under normal conditions the falling phase of the response was caused by inactivation of Ca2+ conductance. In type B and C neurones, the amplitude and duration of the after-hyperpolarization (a.h.p.) following direct activation by long outward current pulses were markedly reduced in Ca2+-free solution. These findings indicate that a large component of this response was generated by the Ca2+-dependent K+ conductance increase. In type A cells the a.h.p. amplitude was originally small and was not affected by the above treatment, suggesting that the participation of this conductance was minimal in this type. In type C neurones, the membrane potential following an inward current pulse showed a delayed return to the base line. This delay was produced by transient K+ conductance, since it was reduced by 4-aminopyridine. The frequency-current (f-I) relation of the first interval in type A and C cells was scarcely affected in Ca2+-free solution, while the slope of the initial firing f-I curves in type B neurones which had the l.t.r. became flatter. Furthermore, the f-I curves of the third interval in type C cells became steeper in Ca2+-free solution. The data indicate that the distinct membrane characteristics related to the heterogeneity among cells in the v.m.h. can be attributed to their specific ionic mechanisms, with the type A neurones showing a minimal high-threshold Ca2+ current, the type B having l.t.r. and the type C having a transient K+ (IA) current.

Action Potentials↗
PubMed1985

Direct action of mazindol on guinea-pig ventromedial hypothalamic neurons: intracellular studies in slice preparation.

Neuronal responses in the ventromedial hypothalamic nucleus (VMH) to mazindol (MZD) were examined by intracellular recordings in hypothalamic slices in vitro. Bath application of MZD caused depolarization of the membrane by 8.0 +/- 3.4 mV (mean +/- S.D.) associated with an increase in the input membrane resistance (23.0 +/- 5.8%) among 20% of the cells examined. Current-voltage plots, obtained simultaneously, showed the reversal potential between -80 and -90 mV. These results indicate that MZD depolarizes VMH neurons by reducing the K+ conductance, through a mechanism similar to that of glucose, and the anorectic action of MZD can be explained by its direct effects on the VMH.

Animals↗
PubMed1984

Behavioral significance of monkey hypothalamic glucose-sensitive neurons.

Feeding-related neuronal activity of lateral hypothalamic glucose-sensitive and glucose-insensitive neurons was investigated in behaving monkeys. The behavioral paradigm was a high fixed ratio of bar pressing for food reward signaled by light and tone cues. Twenty-seven percent of the neurons tested were glucose-sensitive. The population of neurons which changed in firing rate during the feeding task was higher among glucose-sensitive cells than among glucose-insensitive cells. The activity of many glucose-sensitive neurons decreased during the bar pressing and reward periods. A small population of glucose-sensitive neurons responded to cue stimuli. The results suggest that glucose-sensitive neurons are mainly involved in the drive and/or reward mechanism of feeding behavior, and that these cells may have specific roles in neural control of hunger-motivated food acquisition.

Animals↗
PubMed1984

Primary brainstem hemorrhage in a child: usefulness of auditory brainstem response (ABR).

We treated a child with primary brainstem hemorrhage who recovered fairly well. The Auditory Brainstem Response (ABR) correlated well with the clinical course and CAT findings. Primary brainstem hemorrhage leads to neurological abnormalities which may be fatal (Silverstein 1972). As there is apparently no documentation on the correlation between CAT scan and ABR findings in such patients, we report our experience with primary brainstem hemorrhage in a child who recovered.

Adolescent↗
PubMed1983

Characterisation of stocks of Theileria parva by monoclonal antibody profiles.

Sixteen monoclonal antibodies, raised against macroschizonts of Theileria parva, were tested against 10 different stocks of the parasite. The indirect fluorescent antibody test was used to demonstrate that these antibodies showed different binding affinities to macroschizonts of the various stocks. A profile of antibody binding could thus be prepared for each stock. For a given stock the profile was consistently the same irrespective of culture passage level, host cell background and method of antigen preparation. Monoclonal antibody profiles thus appear to provide a means of characterisation of stocks of T parva in vitro, and preliminary evidence suggests that profiles may be used to differentiate strains. The best source of antigen for testing theilerial stocks was macroschizont infected cells raised in culture, but suitable preparations could also be made from lymph node biopsies of cattle infected with East Coast fever. In a field outbreak of disease it might thus be possible rapidly to characterise the strains of T parva involved and plan immunisation and control measures accordingly.

Animals↗
PubMed1983

Immunisation against East Coast fever: correlation between monoclonal antibody profiles of Theileria parva stocks and cross immunity in vivo.

Stocks of Theileria parva, which had been characterised by monoclonal antibody profiles, were used to challenge cattle previously immunised against East Coast fever (ECF). When cattle were subjected to homologous challenge, or heterologous challenge with a stock of identical profile to that which had initiated immunity, they showed mild or inapparent reactions. However, when cattle were challenged with a stock of a different profile many underwent severe or fatal ECF reactions. Thus, there appears to be good correlation between cross resistance patterns in vivo and parasite differences detected in vitro by monoclonal antibodies. The results indicate that monoclonal antibody profiles can be used to characterise strains of T parva in vitro, and thus provide valuable data for planning field immunisation programmes. Now that monoclonal antibodies offer the potential of characterising theilerial parasites so precisely, the need arises for more disciplined use of terms describing parasite populations and collections. It is proposed that the rules of nomenclature devised for trypanosomes be adopted for Theileria species.

Animals↗