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1

Effect of hibernation on sodium and chloride ion transport in isolated frog skin

100%
Kosik-Bogacka D., Tyrakowski T.
|
2007
|
vol. 55
|
issue 1-2
47-51
EN
The aim of the study was to evaluate the effect of hibernation on electrophysiological parameters of isolated frog skin under control incubation (Ringer solution) and after inhibition of Na+ and Cl- transepithelial transport by application of amiloride and bumetanide. The transepithelial electrical potential difference (PD in mV) was measured before and after mechanical stimulation of isolated frog skin. The tissues were mounted in a modified Ussing chamber. The results revealed a reduced PD of frog skin during hibernation. In February, as compared with November, PD of frog skin incubated in Ringer solution decreased by about 50%. Hibernation also affected hyperpolarization (dPD) of frog skin after mechanical stimulation. In November and December, dPD was about 50% and 30% lower, respectively, compared with the subsequent two months of the experiment. The incubation of frog skin with amiloride, a sodium ion channel blocker, resulted in reduced values of all measured electrophysiological parameters irrespective of the phase of hibernation. After application of chloride ion transport inhibitor (bumetanide), the PD in November and December decreased compared with the control incubation by about 80% and 75%, while in January and February by about 40% and 25%, respectively. In January and February dPD increased by four times and three times as compared with November and December. Hibernation reduces net ion flow in isolated frog skin. During the initial period of hibernation the sensitivity of the skin to mechanical stimulation also decreases. Towards the end of hibernation, on the other hand, excitation of mechanosensitive ion channels takes place.
2

Electrophysiological effect of ruthenium red and pH on the skin of the frog, Rana esculenta L.

100%
Kosik-Bogacka D. I., Tyrakowski T.
Folia Biologica
|
2001
|
vol. 49
|
issue 3-4
273-277
EN
Amphibian skin is a sensitive interface between the organism and the environment. Metal ions from the external environment, some of them being trace elements, act on the amphibian skin. It had been shown that stimulation of tactile receptors affected Na+ transport in the frog skin and changed the potential difference, therefore the aim of this project was to study the effect of ruthenium complex, known as ruthenium red (RR), on the ion transport in this organ in vitro under control conditions, after mechanical stimulation and also in the presence of the Na+ transport inhibitor-amiloride. Three different concentrations of RR (0.12, 1.2, and 12.0 mM) in two different pH values (6.4 and 7.4) were studied in vitro in the Ussing apparatus. The measured electrophysiological parameters were the transepithelial electrical potential difference (PD) and the changes in PD after mechanical stimulation (dPD). The gentle mechanical stimulus was a jet of bath fluid from a peristaltic pump directed on the mucosal surface of isolated frog skin. After mechanical stimulation, transient hyperpolarization invariably occurred (dPD = 1.5_0.2 mV). In the presence of RR the hyperpolarization was smaller and this diminution was concentration dependent: 0.5_0.1 mV for 1.2 mM of RR and 0.1_0.1 mV for 1.2 mM of RR. At pH 6.4 the reactions of the skins on the mechanical and chemical stimuli were smaller, in the presence of amiloride disappearing completely, but after the washing away of amiloride from the experimental organ in pH 6.4 the action of RR was stimulatory. The natural defensive reactions of frog skin related to the ion transport and electrical potential difference are affected or disappear in the presence of ruthenium complex.
3

Transepithelial transport of sodium and chloride ions in isolated skin of the frog, Rana esculenta

100%
Kosik-Bogacka D. I., Tyrakowski T.
|
|
issue 3-4
107-114
EN
Isolated frog skin, mounted in a Ussing apparatus, was investigated electrophysiologically. Application of amiloride, an inhibitor of sodium ion transport, and bumetanide, known to block the transport of chloride ions, revealed the effect of these ions on PD, both under control conditions and following mechanical stimulation. Under control conditions, mechanical stimulation of the skin caused hyperpolarization, i.e. a transient increase in the electrical potential difference. Preincubation in the presence of amiloride, or amiloride plus bumetanide, brought about both a decrease in electrical potential and an inhibition of the reaction upon stimulation. On the other hand, incubation with bumetanide resulted in a decrease in electrical potential, but did not affect the skin reaction after mechanical stimulation. The above results indicate that hyperpolarization of the frog skin following mechanical stimulation is caused by enhanced transepithelial transport of sodium ions which, in turn, is induced by stimulation of sensory receptors.
4
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Sulfurtransferase activity and sulfur compound content in Rana temporaria brain following hibernation

88%
Wrobel M.
Acta Neurobiologiae Experimentalis
|
2001
|
vol. 61
|
issue 1
69-72
EN
The activity of rhodanese, 3-mercaptopyruvate sulfurtransferase and g-cystathionase and the content of glutathione and sulfane sulfur compounds were determined in Rana temporaria brain in April. The high sulfane sulfur level observed in the spring seems to be associated with protection against cellular oxidative stress after the period of hibernation with its minimal oxidative metabolism. Key words: sulfane sulfur, sulfurtransferases, glutathione, frog brain
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