Toad

About: Toad is a research topic. Over the lifetime, 1624 publications have been published within this topic receiving 28732 citations.

Response of single motoneurons to direct stimulation in toad's spinal cord.

Abstract: THE ACTIVITIES of single nerve cells explored with intracellular electrodes have been reported by several authors (1, 3, 4, 14). In those reports researches whether were made in connection with orthodromic or antidromic. It the excitation via neural is desirable, however, to pathways, adopt the method of direct stimulation in order to get more detailed knowledge concerning the physiological properties of the soma membrane. Since the insertion out ordinarily without of microelectrodes into the visual control, there is no neurons must be carried possibility of having two separate microelectrodes lodging in the same neuron, the one for stimulation and the other for recording. The use of a twin-microelectrode was also found inappropriate for the present purpose, because of the electrical interference between each electrode due to their capacitative coupling. The only method available was therefore to use the same microelectrode with certain compensation circuits for both stimulation and recording. The results reported here were obtained with such a method on single spinal motoneurons of Japanese toads.

Active sodium transport by the isolated toad bladder.

Abstract: Studies were made of the active ion transport by the isolated urinary bladder of the European toad, Bufo bufo, and the large American toad, Bufo marinus. The urinary bladder of the toad is a thin membrane consisting of a single layer of mucosal cells supported on a small amount of connective tissue. The bladder exhibits a characteristic transmembrane potential with the serosal surface electrically positive to the mucosal surface. Active sodium transport was demonstrated by the isolated bladder under both aerobic and anaerobic conditions. Aerobically the mean net sodium flux across the bladder wall measured with radioactive isotopes, Na(24) and Na(22), just equalled the simultaneous short-circuit current in 42 periods each of 1 hour's duration. The electrical phenomenon exhibited by the isolated membrane was thus quantitatively accounted for solely by active transport of sodium. Anaerobically the mean net sodium flux was found to be slightly less than the short-circuit current in 21 periods of observation. The cause of this discrepancy is not known. The short-circuit current of the isolated toad bladder was regularly stimulated with pure oxytocin and vasopressin when applied to the serosal surface under aerobic and anaerobic conditions. Adrenaline failed to stimulate the short-circuit current of the toad bladder.

Effect of prostaglandin (pge-1) on the permeability response of toad bladder to vasopressin, theophylline and adenosine 3',5'-monophosphate.

Abstract: THE prostaglandins (PGE), a group of naturally occurring fatty acids, have been isolated from a number of sources including sheep vesicular glands and human vesicular plasma1,2. The chemical nature and separation of this series of related analogues have been reported in detail2–4. They have profound effects on blood pressure and on smooth muscle contractility, and are also known to interfere with the action of a variety of hormones on adipose tissue5–7. Because of the possibility that the prostaglandins may have other physiological effects of a more general nature, and perhaps serve as regulators of hormone action in certain tissues, the effect of one of them, PGEI, on the response of the toad bladder to vasopressin, theophylline and adenosine 3′,5′-monophosphate (cyclic-AMP) was examined. All three of the latter compounds, when added to the serosal surface of the isolated bladder of Bufo marinus, increase the osmotic flow of water across this membrane. It has been suggested that vasopressin exerts its permeability effects here and in the kidney by increasing the concentration of adenosine 3′,5′-monophosphate within the tissue8. The cyclic-AMP is presumed to be the intracellular mediator of the vasopressin effect. Theophylline mimics vasopressin in toad bladder, since it inhibits the degradation of cyclic-AMP to inactive 5′-adenosine monophosphate9.