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Biomedical subjects

P C Specht

Publications and source records attributed to P C Specht.

5 recordsLinked to original sources
PubMed1988

Computer graphics interface to a complex simulation.

The program "Cardio VascularCat" is a simulation of a laboratory experiment on the cardiovascular system of the cat, for students of physiology or pharmacology. There are two important innovations in this version, utilizing the "Macintosh environment": 1) The functioning of the program is highly interactive with the student. Any manipulation almost immediately produces some result in the (simulated) experimental animal. 2) The input from the student, and the output to the student, are handled in simple and intuitive ways. The mouse and menu system are utilized to simplify the control of the program. The keyboard is eliminated. The Macintosh graphics capabilities provide for an output display that is easily and quickly interpreted by the student. The program has been tested with a small sample of medical students. As measured by an objective test, the results are equivalent to learning from a textbook. An attitude survey revealed that the Macintosh program is clearly superior for reenforcement and review.

Animals↗
PubMed1983

Correlation of agonist structure with acetylcholine receptor kinetics: studies on the frog end-plate and on chick embryo muscle.

The apparent lifetimes of frog end-plate channels activated by several nicotinic agonists have been determined with voltage-jump and fluctuation analysis techniques. The agonists were monoquaternary, N-substituted derivatives of trimethylammonium (TMA). Methyl TMA activated channels which had apparent lifetimes about 3-4 times shorter than acetylcholine (ACh)-activated channels. This result was confirmed with single-channel recordings from embryonic chick skeletal muscle. Channel conductance and voltage dependence of channel lifetime were similar for methyl TMA- and ACh-activated channels. Methyl TMA showed no signs of blocking open end-plate channels. Ethyl TMA, acetylthiocholine, cholinethiol and carbamylcholine all activated channels similar to methyl TMA-activated channels with regard to lifetime. None of these agonists appeared to block end-plate channels in the employed concentrations. 4-ketopentyl TMA, which contains a methylene group in place of the ether oxygen of ACh, sometimes opened end-plate channels with similar apparent lifetimes as those opened by ACh. Single-channel recordings showed that bursts of current from channels activated by 4-ketopentyl TMA have similar durations as do those activated by ACh. Pentyl TMA and benzyl TMA block open end-plate channels even when delivered at doses which elicit very small currents. It is concluded that the ester moiety of ACh serves to stabilize the open conformation of the channel.

Acetylcholine↗
PubMed1976

Phase-plane analysis of action potentials in uterine smooth muscle.

Action potentials were recorded by microelectrode from narrow strips of pregnant rat uterus in vitro. The phase-plane display (V vs dV/dt) of selected action potentials was analysed by the method of Jenerick (1964) to yield the ionic current. From this membrane current data, various parameters of the action potential were calculated. In comparison to skeletal muscle action potentials, the ionic currents were 30-100 times smaller in the uterus action potential. Epinephrine hyperpolarized the resting potentials and suppressed spontaneous activity, but did not cause any significant changes in the stimulated action potential. The after-potential may have been affected by epinephrine, preventing repetitive firing, but the data were inconclusive. The phase-plane analysis results were similar to the results of the double sucrose gap voltage clamp method on the same tissue (Kao and McCullough, 1975).

Action Potentials↗
PubMed1976

Propagation of stimulated slow waves in cat intestinal muscle.

This study was designed to examine the propagation and propagation failure of the slow wave. Spontaneous slow waves and action potentials were recorded from the longitudinal muscle layer of small strips of cat jejunum. Slow waves could be stimulated electrically at intervals shorter than the spontaneous interval, and the velocity of propagation of these slow waves was slower than the spontaneous slow waves. The velocity of propagation was approximately proportional to the time between slow waves. At intervals about one-half the normal spontaneous interval the propagation became slow and unstable, which would result in the periodic failure of a single slow wave. This type of failure may underlie the formation of the slow-wave frequency gradient observed in the intact intestine. The wave shape of the external recording of the slow wave, together with the measurement of electrotonic current spread in strips of isolated muscle, suggest that the slow wave propagates by local circuit currents in an electrically excitable cablelike tissue.

Animals↗