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PubMed1995

Phagocyte activity in the frog Rana temporaria: whole blood chemiluminescence method and the effects of temperature and thermal acclimation.

The respiratory burst activity of phagocytes was measured as zymosan induced, luminol-enhanced chemiluminescence (CL) emission in the whole blood of the frog Rana temporaria. The effect of thermal acclimation on phagocyte activity was studied by acclimating adult frogs for 14-18 days to 5 and 24 degrees C. The phagocyte CL was measured at seven temperatures ranging from 5 to 37 degrees C. Clear signs of resistance acclimation were seen both in CL reaction kinetics at 5 degrees C (P < 0.0001) and in intensities at 37 degrees C (P < 0.003). Thermal adaptation was also seen as a 1-5 degrees C shift in the temperature response curve of CL intensity towards the acclimation temperature (P < 0.03). The highest CL intensities were seen at 30 degrees C and they were of the same magnitude in both acclimation groups. The phagocyte activation enhanced progressively at temperatures ranging from 5 to 30 degrees C, showing that migration to a warmer environment would increase the phagocyte activity of frogs. The possible relation to behavioral fever is discussed.

Animals↗
PubMed1986

Differences in thermal stability of frog and rabbit alpha alpha- and alpha beta-tropomyosins determined by optical rotatory dispersion.

Frog and rabbit alpha alpha- and alpha beta-tropomyosins were purified, and their thermal stabilities determined by use of optical rotatory dispersion. The tropomyosins were found to be virtually completely helical at 5 degrees C. Regions of different thermal stabilities were seen for all tropomyosins. Rabbit and frog alpha alpha-tropomyosin show very similar thermal properties, with main transitions near 47-49 degrees C. The main transition for frog alpha beta-tropomyosin is at 32 degrees C. The results show that the alpha beta-tropomyosins are less stable than the alpha alpha-forms. Only thermal transitions of the alpha beta-forms appear to be correlated with the body temperatures of the animals.

Animals↗
PubMed1991

Thresholds for premature ventricular contractions in frog hearts exposed to lithotripter fields.

Piezoelectrically generated lithotripter shocks were shown to produce premature ventricular contractions of the frog heart. Anesthetized grass frogs, Rana pipiens, were studied following implantation of an aortic catheter and EKG leads. The most sensitive phase of the heart cycle for the generation of premature ventricular contractions with lithotripter shocks at 30 MPa peak pressure was found to be the T-P segment. During this phase of the heart cycle, the minimum peak-positive pressure shock wave necessary to produce a premature ventricular contraction in a frog heart was between 5 MPa and 10 MPa.

Animals↗
PubMed1984

Stimulatory effect of a GnRH agonist (buserelin) in in vitro and in vivo testosterone production by the frog (Rana esculenta) testis.

The summary testicular effects of an agonistic analogue of gonadotropin-releasing hormone (buserelin, GnRHa) have been studied in vitro and in vivo in the frog, Rana esculenta. During 3 h incubation GnRHa (8 X 10(-7) M) potentiated pituitary factors in stimulating testosterone production by minced testes in vitro. After 6 h of incubation 8 X 10(-7) M GnRHa stimulated maximal testosterone output. Testes of 10-day hypophysectomized animals did not show any GnRHa effect in vitro. In vivo, a direct effect of GnRHa on testicular testosterone production was demonstrated in hypophysectomized animals, although this effect was temperature-dependent, requiring the frog to be maintained at a high temperature (24 degrees C). No effect of GnRHa was detectable in frogs kept at a low temperature (4 degrees C).

Animals↗
PubMed1981

Abandoned synaptic sites in muscles of normal adult frog.

In previous investigations light microscopic cholinesterase (ChE) deposits without any nerve were found adjacent to normally occupied parts of a frog neuromuscular synapse [4, 9]. After identifying one such site at the light microscopic level ultrathin sections were cut and viewed with an electron microscope. ChE reaction product-filled secondary, clefts were observed in the region studied but a nerve was invariably missing. From this it is concluded that these loci are former synaptic sites from which nerve and Schwann cell have retracted, When incubating muscles with fluorescence-labelled alpha-bungarotoxin, all 23 abandoned sites found in 6 muscles remained bare of visible amounts of label. This indicate that receptor molecules eventually disappear from the synaptic membrane after retraction of the nerve and Schwann cell. No information as to the underlying time schedule of nerve retraction, turnover of ChE and alpha-bungarotoxin binding sites was obtained. Taken together with the evidence for synapse new formation in untreated frog muscles obtained previously [9, 11] the present observations indicate some ongoing remodeling of frog neuromuscular junction.

Animals↗
PubMed1981

Suggested evolution of tonotopic organization in the frog amphibian papilla.

As one progresses from the most primitive to the most derived frogs, one observes remarkable changes in that peculiarly amphibian auditory organ, the amphibian papilla. In all but the most primitive frog, the papilla comprises two patches with separate innervation and apparently corresponding to a spatial separation of frequency sensitivity (i.e. tonotopic organization). The caudal patch is quite variable and in the more derived frogs exhibits an elongation that apparently corresponds to extension of auditory sensitivity to higher frequencies.

Animals↗
PubMed1982

Ubiquitous presence of the tailed, asymmetric forms of acetylcholinesterase in the peripheral and central nervous systems of the frog (Rana temporaria).

Five molecular forms of acetylcholinesterase can be solubilized from the peripheral and central nervous systems of the frog: they will be referred to as the 3.6, 6, 10.5, 14 and 18 S forms. They seem to be analogous to the forms present in endplate-rich and endplate-free regions of frog skeletal muscle. In particular the 18 and 14 S forms represent the collagen-tailed forms of frog acetylcholinesterase. These heavy forms are found in all peripheral and central tissues examined, including whole brain or regions of brain: cerebellum, telencephalon, optic tectum, spinal cord, spinal ventral and dorsal roots and sciatic nerve, as well as in glial or Schwann cellrich tissues devoid of neuronal elements, such as the filum terminale or the severed stump of the nerve, several weeks after section. The 18 S form may represent up to 30% of total acetylcholinesterase activity. It thus seems that the 14 S and 18 S forms are very widely distributed throughout most neuronal and non-neuronal tissues in amphibians.

Acetylcholinesterase↗
PubMed1984

Two different receptor sites for Ca2+ and Na+ in frog taste responses.

Distilled water, 1 mM CaCl2 and 500 mM NaCl (pH 4.5) are effective stimuli which excite chemoreceptors of the frog tongue. To learn whether or not these taste stimuli react with different taste receptor sites, a proteolytic enzyme was topically applied to the tongue dorsum. Responses were recorded from the frog glossopharyngeal nerve during taste stimulation. After application of 0.1% pronase E to the dorsal tongue surface, the magnitude of the NaCl response remained unchanged, but the magnitude of the water and CaCl2 responses was markedly decreased. The selective suppression by the pronase E treatment indicates that there are two different receptor sites for Ca2+ and Na+ in the frog taste receptor cell and the receptor sites responsible for the generation of the water and the Ca2+ response may be composed of a protein.

Adaptation, Physiological↗
PubMed1985

Diphenylhydantoin reduces veratridine-induced sodium permeability in frog skeletal muscle.

The effect of the anti-epileptic drug 5,5'-diphenylhydantoin (Dilantin) on Na permeability (PNa) in frog skeletal muscle was studied. Because there is no detectable tetrodotoxin-sensitive Na permeability in resting frog muscle, PNa was induced using the alkaloid 'neurotoxin' veratridine. Veratridine has been previously characterized as a useful 'tool' for producing a population of open Na channels in frog muscle. The amount of sodium permeability produced by veratridine was quantified in two ways: by measuring (a) membrane potential (Vm) and (b) 22Na influx. Dilantin was shown to reverse veratridine-induced depolarization by approximately one-third and to inhibit veratridine-induced Na influx in a dose-dependent manner, with an apparent Km of 78 +/- 8 microM.

Animals↗
PubMed1988

The cervico-ocular reflex in intact and chronically labyrinthectomized frogs.

Eye movements in response to horizontal oscillation of the body against the stationary head (cervico-ocular reflex) were measured with search coils in the frequency range between 0.02 and 1.0 Hz in intact and chronica bilaterally labyrinthectomized frogs. The evoked eye movements were compensatory in direction but only about 1-2% of the amplitude of the stimulus (+/- 5-20 degrees). In chronic bilaterally labyrinthectomized frogs (n = 5) very similar response characteristics were measured. The very small amplitudes of these responses in controls and in frogs with removed labyrinthine organs render this reflex functionally irrelevant for both gaze stabilization and recovery from dynamic vestibular deficits after a loss of labyrinthine function.

Animals↗
PubMed1989

Lithium decreases retinal melatonin levels in the frog.

The effect of the acute i.p. administration of lithium chloride (1 mg/kg) and of haloperidol (1 mg/kg) on retinal melatonin levels was studied in light-adapted and dark-adapted frogs of the species Rana esculenta. Two hours following drug administration, animals were killed by decapitation and a single retina from each frog was collected and homogenized in 1 ml of chilled 0.1 N HCl. After centrifugation, the pH of the supernatant was adjusted to 7.0. Melatonin was extracted by diethylether and assayed by double antibody radioimmunoassay (RIA). Lithium induced a significant decrease of retinal melatonin levels both in light-adapted (P less than 0.006) and in dark-adapted (P less than 0.01) animals, whereas no change was observed after haloperidol treatment. These results suggest that the scleral aggregation of pigment granules induced by lithium in the frog retina is not mediated by a stimulation of melatonin synthesis.

Animals↗
PubMed1990

Distribution and co-existence of Met-enkephalin-like and mesotocin-like immunoreactivity in the neural lobe of the pituitary of the frog.

Content and distribution of Met-enkephalin (Met-ENK)-like immunoreactivity in the hypothalamo-hypophysial system of bovine, rat and frog were examined using specific radioimmunoassay and immunohistochemistry. Ultrastructural localization and co-existence of Met-ENK-, mesotocin (MT)- and vasotocin (VT)-like immunoreactivity in the neural lobe of the frog pituitary was examined by a method combining pre-embedding peroxidase-antiperoxidase immunostaining for Met-ENK with post-embedding immunocolloidal gold staining for MT or VT. The highest concentrations of immunoassayable Met-ENK were present in the neural lobe of the pituitary of the frog. In addition to nerve fibers showing only MT-like or Met-ENK-like immunoreactivity, nerve fibers containing neurosecretory granules showing both MT- and Met-ENK-like immunoreactivities were very rich. But VT-like and Met-ENK-like immunoreactivity was confirmed separately in different axon terminals.

Animals↗
PubMed1993

6-Phosphofructo-2-kinase and control of cryoprotectant synthesis in freeze tolerant frogs.

A critical part of natural freeze tolerance is the production of low molecular weight cryoprotectants; in freeze tolerant frogs this involves a freezing-induced activation of liver glycogenolysis that leads to the accumulation of glucose as the cryoprotectant, in amounts up to 300 mM, in all organs. The present study shows that the synthesis and maintenance of high organ glucose pools is facilitated by changes in the levels of fructose-2,6-bisphosphate (F2,6P2) and an inhibition of liver 6-phosphofructo-2-kinase (PFK-2) activity that blocks the catabolism of glucose by glycolysis. Freezing exposure (24 h at -2.5 degrees C) resulted in a sharp drop in F2,6P2 levels in four organs, to 23-75% of control values, but F2,6P2 rebounded when frogs were thawed. Freezing also stimulated changes in the properties of liver PFK-2 including a decrease in maximal velocity, a basic shift in pH optimum, a 10-fold increase in Km for fructose-6-phosphate, and increased I50 values for enzyme inhibitors. I50 values for glycerol-3-phosphate and phosphoenolpyruvate were 60- and 2.4-fold higher, respectively, for liver PFK-2 from frozen frogs compared with controls. Changes in liver PFK-2 properties are consistent with a freezing-induced phosphorylation of the enzyme to produce a less active enzyme form, resulting in reduced organ F2,6P2 levels and a decrease in 6-phosphofructo-1-kinase activity.

Adaptation, Physiological↗
PubMed1982

Tyrosine aminotransferase activity of frog (Rana esculenta) liver--II. Comparative aspects of intracellular distribution.

1. A subcellular fractionation procedure for frog liver is reported and validated by the distribution pattern of several marker enzymes, also in comparison with rat liver. 2. The subcellular distribution of tyrosine aminotransferase was investigated in frog liver as compared to rat liver: a different distribution of the enzyme was observed, being the activity mostly recovered in mitochondrial and cytosolic compartments. 3. Results indicate that mitochondrial tyrosine aminotransferase of both frog and rat liver is a matrix enzyme, even if differences are observed concerning its release from the organelles upon detergent treatment.

Animals↗
PubMed1982

Tyrosine aminotransferase activity of frog (Rana esculenta) liver.

1. The presence of tyrosine aminotransferase is reported both in particulate and soluble fractions of frog liver. 2. The activity of the soluble enzyme of frog liver was investigated with regard to its dose and time dependence, its substrate specificity and concentration dependence, its thermal sensitivity as well as pH and temperature dependence. 3. It appears that the properties of the soluble tyrosine aminotransferase of frog liver are in close agreement with those reported for the mammalian liver enzyme.

Animals↗
PubMed1983

Glucocorticoid receptor of frog (Rana esculenta) liver.

The presence of a glucocorticoid soluble receptor is demonstrated in frog liver cytosol. The kinetic characterization of frog liver cytosolic receptor for glucocorticoids is reported and its steroid specificity assessed. Results indicate a gross similarity between frog liver and mammalian glucocorticoid receptor, being a major difference the reduced binding capacity.

Animals↗
PubMed1988

Frog liver dolichols: separation and quantitative determination related to seasonality.

1. The liver of female frogs shows a significantly higher dolichol content in May (134 micrograms/g) than in November (90 micrograms/g). The male frog liver (134 micrograms/g May; 119 micrograms/g November) does not show any significant change. 2. The rat liver does not show any significant change in dolichol content from May to November (30 micrograms/g). 3. The dolichyl-phosphate level was the same in male and female frog livers and in the rat liver. 4. Data is given of the distribution of dolichols according to the number of their isoprene residues.

Animals↗
PubMed1990

The effect of ADH and insulin on active sodium transport across frog skin in the presence of alternariol mycotoxin.

1. The effect of vasopressin and insulin on active sodium transport across frog skin in the presence of internal alternariol mycotoxin was studied, using the short-circuit technique. 2. Vasopressin stimulates sodium transport across frog skin by decreasing the resistance to sodium entry into the epithelial cells, thus partially removing the inhibition on the short-circuit current due to the action of Alternariol mycotoxin. 3. Even insulin which is known to increase the short-circuit current by a different mechanism, determines a rapid reversal effect on the inhibition due to Alternariol. 4. These data confirm the different action of the two hormones on active sodium transport across frog skin, and furthermore are indicative of an inhibition of transepithelial sodium transport by Alternariol mycotoxin probably via the sodium pump.

Animals↗