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At least 793 records · Page 44Linked to original sources
PubMed1984

The distribution of substance P in the habenulo-interpeduncular system of the frog shown by an immunohistochemical method.

The distribution of substance P(SP)-like immunoreactivity was studied in the habenulo-interpeduncular (HAB-ITP) complex of the frog Rana esculenta by means of the immunohistochemical peroxidase-antiperoxidase (PAP) method. The HAB of the frog were subdivided into dorsal and ventral nuclei, corresponding to the medial and lateral HAB of mammals respectively. In addition, the dorsal HAB of the frog were morphologically asymmetric, since only the left has a lateral and a medial subnucleus. SP-like immunoreactive cells were found in the right dorsal HAB, in the lateral subnucleus of the left dorsal HAB and in a nucleus of scattered cells located rostrodorsally to the ITP. However, the medial subnucleus of the left dorsal HAB and a portion of the right dorsal HAB facing the 3rd ventricle, did not show SP immunoreactivity. Immunoreactive fibers were found in the medial subnucleus of the left dorsal HAB, in the two fasciculi retroflexes and in the ITP. Moreover, immunoreactive terminals were observed in the ventral HAB of both sides, in the ITP and on the blood vessels which cross the ITP. It is assumed that a portion of fibers connecting the various structures of the HAB-ITP complex belongs to the SP peptidergic system as suggested for mammals. However, in contrast to the mammals, the results on the frog are in favour of an histochemical asymmetry of the SP-like immunoreactivity, since a different distribution of this peptide was found between the right and left side of the brain. Such histochemical asymmetry was less pronounced than the morphological asymmetry and its functional meaning is unknown.

Animals↗
PubMed1983

Differential distribution of opsin in the plasma membrane of frog photoreceptors: an immunocytochemical study.

Opsin molecules on the surface of frog photoreceptors were visualized by immunocytochemistry at the ultrastructural level. Isolated retinas were immersed in biotinyl-antibody to bovine opsin followed by avidin-ferritin conjugates. Anti-opsin bound to the plasma membrane and to the surface of the most basal discs of red rod outer segments. Inner segment plasma membranes of red rod photoreceptors were devoid of anti-opsin label except for the apical plasma membrane in the region of the recently described periciliary ridge complex. The connecting cilium surface from its base at the periciliary region to the site of new disc evagination was almost free of anti-opsin binding, an observation in consonance with prior studies of thin sectioned retinas embedded in glutaraldehyde cross-linked bovine serum albumin. These results indicate that the continuous plasma membrane of photoreceptors is highly polarized. Opsin, which is free to diffuse throughout the outer segment plasma membrane and along the discs, does not back-diffuse onto the inner segment plasma membrane. The periciliary ridge complex and the base of the connecting cilium are possible sites of restriction of opsin mobility. This study also has provided new insight into the molecular structure of frog visual pigments. Frog green rod and cone outer and inner segment plasma membranes were not labeled by this sheep antiserum to bovine opsin. In contrast, discs of green ROS and the lamellae of some cones were labeled when these antibodies were applied to albumin embedded thin sections of frog retinas. Apparently, only internal or intramembraneous domains of green ROS and cone visual pigments were recognized by this antibody while both internal and extracellular domain(s) of red ROS opsin were reactive.

Animals↗
PubMed1983

K+ depolarization and phospholipid metabolism in frog sartorius muscle.

K+ depolarization evokes phosphatidylinositol response, i.e. the increased 32P orthophosphate labelling of phosphatidylinositol in frog sartorii muscles. The phosphatidylinositol response seems to be closely related to K+ depolarization and not to the transient Ca2+ release at the beginning of depolarization. It ceases as soon as the muscles depolarized by 90 mmol/l KCl for a short period of time are repolarized, while it continues when the depolarization is maintained. When the muscles are depolarized with 20 mmol/l KCl, the phosphatidylinositol response is also observed. This response is not suppressed by drugs that block Ca2+ mobilization. Other agents like caffeine, azide or EGTA which induce some effects similar to that of K+ depolarization, do not evoke phosphatidylinositol response. Rather, they simply cause a decrease in the labelling of phospholipids, phosphatidylinositol being the least affected. In muscles derived from frogs maintained under healthy conditions Ca2+ release in the early phase of K+ depolarization does not cause significant changes in phospholipid labelling. However, in muscles from frogs starving for many months, a large decrease in the labelling of phospholipids is observed in the early phase of K+ depolarization. It is postulated that the changes in the physicochemical state of the membrane and not Ca2+ gating mechanism or free cell Ca2+ level are crucial in the phosphatidylinositol response in the frog sartorii muscles depolarized by high K+.

Animals↗
PubMed1983

[Cytophotometric study of the DNA content in the cells of the preoptic area of the hypothalamus in hibernating common frogs].

The DNA content in the squashed Feulgen stained cells of the hypothalamic preoptic region in wintering adult and juvenile frogs was measured cytophotometrically. The vast majority of hypothalamic cells studied showed diploid DNA contents. Only 0.9% of tetraploid cells (4c and 2c X 2 cells) was found in this region, both in adult and juvenile frogs. The incidence of tetraploid hypothalamic cells varied among the individuals studied. In some adult frogs as well as in some juveniles no tetraploid cells were detected. The data obtained do not confirm the age related increase in the mean DNA content in frog's hypothalamic cells population.

Animals↗
PubMed1984

External application of antibiotic to improve survival of adult laboratory frogs (Rana pipiens).

Survival data for over 500 adult frogs (393 Rana pipiens, 35 Rana clamitans , and 97 Rana temporaria) obtained from commercial suppliers were accumulated. Frogs which developed signs of red-leg disease while being kept in 0.15% saline were cured by addition of appropriate antibiotics to the saline. The appropriate antibiotic was determined by sensitivity testing of bacteria isolated from the sick frogs. When many frogs in a shipment were sick, prophylactic treatment of the entire shipment improved the overall survival in the shipment.

Animals↗
PubMedDate not supplied

[Effect of lithium on water-salt metabolism in the frog Rana temporaria].

Frogs kept in distilled water with 1 mM LiCl loose Na more readily than control animals in pure distilled water. After 10 days of staying in a medium with LiCl, a decrease of total content of Na and K in the body and skeletal muscles was observed together with a decrease in sodium content of the blood serum and intracellular concentration of potassium in muscles. There was no difference in the volume of extracellular fluid between the two groups of frogs. Concentration of Li in the blood serum was 5 times higher than that in the external medium, indicating active transport of Li across the skin. In skeletal muscle fibers, Li concentration was twice lower than in the blood serum. In frogs kept in LiCl solution, the increase in diuresis, as well as the increase in urinary excretion of Na and K were observed. It is suggested that Li ions inhibit sodium transport or prevent hormonal effects on the kidney, urinary bladder and skin of the frogs.

Animals↗
PubMed1981

Aeromonas hydrophila in wild-caught frogs and tadpoles (Rana pipiens) in Minnesota.

Frogs and tadpoles were captured at 14 sites in and near Minnesota during 1978-79 and nearly all appeared healthy. Aeromonas hydrophila was isolated from 94 of 294 (32%) juvenile and adult frogs and from 66 of 104 (63%) tadpoles. Of the isolates from frogs and tadpoles respectively, 68% and 47% were from the intestine only, 12% and 32% were from the intestine and the other sites, and 20% and 21% were from extraintestinal sites only. Isolations were more frequent from frogs collected in March-June than in August-November. Evidence was not found that disease due to Aeromonas hydrophila was a primary cause of declining Rana pipiens populations in Minnesota.

Aeromonas↗
PubMed1994

[Receptor-mediated endocytosis in the cells of cold-blooded animals. II. The fate of internalized 125I-insulin in the isolated hepatocytes of the lamprey and the frog].

The 125I-insulin outflow from isolated hepatocytes of the frog and lamprey "loaded" with the labeled hormone has been studied. It is shown that the ligand outflow from the frog cells increased with the increase in the incubation temperature from 0 up to 20 degrees C. The curves of the rest cell radioactivity were reciprocal to those of the radioactivity accumulated in the medium at the corresponding temperatures. At 0.5 and 20 degrees C the degraded 125I-insulin made 5.7 and 17% of the whole hormone accumulated in the medium. In the lamprey hepatocytes, neither accumulation in the incubation medium nor outflow of the radioactivity from cell was seen at all temperatures studied. The intracellular degradation of 125I-insulin in the frog hepatocytes was no more than 7% of the internalized ligand, compared to about 25% in the lamprey cells. The specific binding of 125I-insulin was twice increased in the presence of lysosomal inhibitor chloroquin; contrary to this, no increase was found in the lamprey hepatocytes. The results of experiments on the frog hepatocytes lead us to a conclusion that the processing pathway of internalized insulin in cold-blooded vertebrate cells is similar mainly to that in cells of warm-blooded species, but takes place at lower temperatures and with slower rates. The peculiarities of processing in the lamprey hepatocytes (extralysosomal ligand degradation, the inability to release the internalized ligand and its degradation products) are dependent on a deep transformation of hepatocytes during prespawning migration period.

Animals↗
PubMed1994

Influence of salmon melanin concentrating hormone on vasopressin analogue (dDAVP) activity and sodium transport in frog skin.

Salmon melanin-concentrating hormone (sMCH) is a peptide known to regulate skin pigmentation both in fish and tetrapod (frog and lizard). To evaluate the influence of sMCH on ionic transport in frog skin, standard voltage-clamp technique for the measurement of transepithelial short-circuit current (ISC) reflecting net sodium transport was used. It was found that sMCH alone applied at concentrations of 0.5; 5 or 10 mumol/l failed to influence ISC. The application of 5 mumol/l of sMCH, however, inhibited ISC across the skin stimulated by a synthetic analogue of vasopressin (dDAVP), whereas no influence on natriferic effect of 1 mumol/l forskolin by the studied peptide was observed. The results indicate that cAMP was presumably not involved in the mediation of sMCH action in frog skin. We assume that the interaction of sMCH with the basolateral membrane could lead either (1) to changes of membrane structure including organization of its lipid surrounding or (2) to modification of AVP/dDAVP receptor activity and binding capacity. The nature of these interactions and change(s) in cell membrane and signal(s) which trigger processes responsible for the inhibitory effect of sMCH on dDAVP-stimulated frog skin sodium transport remains to be elucidated.

Animals↗
PubMed1994

The effect of highly diluted agitated thyroxine on the climbing activity of frogs.

We studied the influence of specially prepared highly diluted thyroxine on the spontaneous tendency of juvenile frogs, which were at the end of thyroxine-controlled metamorphosis, to leave the water and climb onto land. The test dilution with a thyroxine concentration beyond Avogadro's value (dilution thyroxine D30) and the reference (dilution water D30) were prepared according to directions from the literature on homeopathy. A few drops of these solutions were added to tap water of basins containing the frogs. The frogs' climbing activities were monitored immediately after adding the solutions. The hypothesis derived from a preliminary study was that there is less climbing activity in frogs treated with dilution thyroxine D30 than in a reference group. This hypothesis was proven. Climbing activity diminished under the influence of dilution thyroxine D30, with statistical significance both in comparison to the effect of the analogously prepared solvent (dilution water D30) as well as in comparison to control observations before the start of treatment. When in a later step of observation the dilution water D30-control group was treated with dilution thyroxine D30, the diminishing effect on activity also occurred.

Animals↗
PubMed1994

Effects of honey containing grayanotoxin I on frog gastrocnemius muscle.

The presence of grayanotoxins (GTX-I, GTX-II and GTX-III) in honey samples from the Mediterranean Sea and Black Sea regions of Turkey and the effect of honey containing GTX-I on the threshold stimulus voltage of frog gastrocnemius muscle were studied. We used 2 groups of gastrocnemius muscles isolated from curarized or noncurarized frogs. The threshold voltage was measured by external perfusion with a polygraphic system. Isolated muscle preparations were perfused separately with Clark-frog-Ringer's solution containing honey solutions from the Mediterranean Sea region (normal) or with honey solutions from the Black Sea region (GTX-I-containing, poisonous). There was no significant difference between the normal and poisonous honey groups data with the curarized preparations. But in the noncurarized preparations, the honey containing GTX-I significantly decreased the threshold voltage in comparison with normal honey. These findings suggest the effect of GTX-I on frog neuromuscular junctions is due to an increase in membrane permeability to sodium ions.

Animals↗
PubMed1993

Voltage dependent ionic currents in frog cultured skeletal myocytes.

The voltage dependent ionic currents in cultured embryonic skeletal myocytes at stages of development ranging from 1 to 6 day were studied using the whole-cell patch clamp technique. Sodium (INa) and calcium (ICa) inward and potassium (IK) outward currents were observed at all stages. INa did not differ from that described in adult frog striated muscle fibres. Slow ICa was mediated by current through dihydropyridine sensitive Ca channels and it did not differ in its kinetics from corresponding slow ICa in frog adult twitch muscle fibres. In about 10% of cells examined for ICa, this current was significantly slower and similar to ICa described in frog tonic muscle fibres. In some cases two slow calcium currents with distinguishable kinetics were recorded in the same myocytes. Fast dihydropyridine-insensitive noninactivating ICa could also be observed. At least 6 types of IK were registered, with approximate time-to-peak (at test pulse of -10 mV) 5, 12, 20, 30, 50 ms (fast IK) and more than 7 s (slow IK). Three of them (5, 20 and 30 ms) predominated in 3-day cultures and disappeared in 6-day-old cultures. IK in myocytes did not correspond fully in the kinetics to IK reported in adult frog skeletal muscles. Channels associated with transient fast and noninactivating slow IK were shown to be highly sensitive to low temperature (+5 degrees C).

Animals↗
PubMed1993

pH-sensitive calcium release in triads from frog skeletal muscle. Rapid filtration studies.

Triad vesicles from frog skeletal muscle exhibited calcium-induced calcium release highly sensitive to extravesicular pH; calcium induced release at pH > 7.4 but not at pH 6.8. In contrast, triads isolated from rabbit skeletal muscle exhibited significant calcium-induced calcium release at pH 6.8. At pH 7.4, there was no stimulation of calcium release in triads from frog at pCa 7, maximum stimulation at pCa 5, and complete inhibition at pCa 3. Addition of ATP at pCa 5, pH 6.8, induced calcium release with the same high rate constants in both preparations. In triads from frog, ATP-induced calcium release at pCa 5 had the same kinetics at pH 6.8 and 7.4, whereas ATP-induced calcium release at pCa > 8, pH 6.8, was partial, with a decrease in the amounts released but not in rate constants. In contrast, triads from rabbit displayed the opposite behavior, with a decrease in rate constants but not in the amounts of calcium released at pCa > 8, pH 6.8. In triads from frog ATP-induced calcium release decreased at pCa < 4, to reach total inhibition at pCa 2; addition of magnesium (free > 0.5 mM) completely abolished ATP-induced calcium release at pH 6.8, pCa 7 or 5. The potential physiological relevance of these results is discussed.

Adenosine Triphosphate↗
PubMedDate not supplied

[Volume regulation in Rana ridibunda frogs and rats].

In experiments on the frog Rana ridibunda and albino rats, studies have been made on water and electrolyte excretion after intravenous injection of isotonic solution of NaCl, water and saline (0.35% solution of NaCl for frogs and 0.45% solution for rats) loadings which amounted to 3% of the body weight. All types of this stimulation increase renal excretion of sodium and potassium in rats. In frogs, intravenous injections of isotonic solution of NaCl increased sodium and potassium excretion to a lower extent, as compared to that in rats; in experiments with water and saline loadings, the excretion of sodium increased to a higher extent, whereas potassium excretion remained practically unchanged. The increase of water and electrolyte excretion on frogs is due to the appearance in the blood of a humoral natriuretic factor, which in these animals does not practically affect potassium excretion.

Animals↗
PubMedDate not supplied

[Relationship between the amplitude of myocardial contractions in frogs and the frequency of electrical stimulation. Role of external and intracellular calcium in the coupling of excitation and contraction].

Ionic currents were studied on the frog atrial trabeculae (Rana ridibunda) at 20 degrees C using a double sucrose gap voltage clamp arrangement. The net inward current peaks did not change in the course of repetitive stimulation (0,5/s) in contrast to the increase of the contraction amplitude (isometric tension) in the similar conditions (Bowdich staircase). The slow component of the net inward current revealed under the action of TTX (2-10(-8) g/ml) was increased upon the increase of external Ca concentration but was blocked when D-600 was introduced into the solution. The inhibitory action of D-600 on the contraction amplitude was frequency independent (in the ranges: 0,1--0,7/s). The decrease of external Na+ (isoosmotic replacement of 70% NaCl by sucrose) or the increase (5-fold) of the external Ca2+ significantly enhanced the myocardial contraction depressed with D-600. However these contractions fall in the course of rhythmical stimulation, and the effect being strongly dependent on the rate of stimulation. The results confirm the assumption (see: Biophysics, 6, 1024, 1976), that intracellular Ca stores (sarcoplasmic reticulum, internal surface of the cellular membrane) are involved in the control of the contractility in the amphibian myocardial cells. Many peculiarities of the excitation-contraction coupling in the frog myocardial cells can be explaned if one assumes that: 1) there is no space separation of primary uptake and release of Ca ion sites in the frog myocardium; 2) the system of "resting Ca chanels" in the frog myocardial cells is not so well developed as in the mammalian myocardial cells.

Animals↗
PubMed1997

The involvement of topoisomerase I in the induction of DNA-protein crosslinks and DNA single-strand breaks in cells of ultraviolet-irradiated human and frog cell lines.

Exposure of GM 4390 human skin fibroblasts and ICR 2A frog cells to 10 kJ m(-2) of ultraviolet B (UVB) radiation resulted in the formation of DNA-protein crosslinks (DPCs) and DNA single-strand breaks (SSBs). However, upon incubation, there were rapid increases in the yields of both DPCs and SSBs. An enhancement in these DNA alterations was detected within 12 min after irradiation and their levels continued to rise by 5-8-fold within 15 h after exposure to UV radiation. Using an antibody-based assay that measures covalent complex formation between topoisomerase (topo) I and genomic DNA, it was found that topo I is one of the proteins involved in these DPCs induced by UV radiation. The levels and rate of increase of topo I-DNA covalent complexes were similar to the UV-radiation-dependent formation of DPCs and SSBs. A UV-radiation-sensitive mutant frog cell line, DRP 153, was also examined and was found to be deficient in this induction of DPCs and SSBs by UV radiation. When these cells were transfected with the human SUVCC3 gene, the resulting transformant displayed kinetics for the induction of DPCs and SSBs similar to the human and parental frog cells. However, human topo I was not defected in the transformed frog cells, indicating that SUVCC3 does not encode topo I. It is likely that SUVCC3 encodes an associated enzymatic activity which permits normal stimulation of topo I-DNA covalent complexes in UV-irradiated cells.

Animals↗
PubMed1997

Volume regulation in red blood cells of the frog Rana temporaria after osmotic shrinkage and swelling.

To investigate the volume regulatory ability of frog erythrocytes, we studied water and ion contents in the cells incubated in isosmotic (210 mOsm) and anisosmotic media. The cell volume decreased to 63% of the control in a hypertonic medium (+200 mM sucrose) and then gradually recovered to approximately 81% within 2 h. The regulatory volume increase (RVI) was associated with the accumulation of intracellular Na+, whereas the intracellular K+ content remained the same. Na+ (22Na) influx into the red cells increased from 1.1 +/- 0.2 in an isotonic medium to 12.4 +/- 0.4 mmol/(1 cells.h) in a hypertonic medium. The changes in both intracellular water and Na+ contents and the Na+ influx were blocked by 1 mM amiloride. Thus, it is likely that RVI observed in frog erythrocytes under hyperosmolar conditions is due to the activation of Na+/H+ exchanger. The exposure of the red cells to hypotonic media (approximately 160 mOsm) resulted in an increase of cell volume to 138% of the control value. The swollen cells gradually recovered their volume (on average by 69% in 2 h) due to losses in intracellular K+ and water. K+ (86Rb) influx in erythrocytes in the hypotonic medium (3.4 +/- 0.3 mmol/l.h) was significantly greater than that in the isotonic medium (1.4 +/- 0.03 mmol/l.h). K+ loss from frog erythrocytes incubated in a K(+)-free medium was significantly stimulated by hypotonic swelling, despite a decrease in the intracellular in K+ concentration. The regulatory volume decrease (RVD) and the changes in K+ transport across the red cell membrane in a hypotonic medium were completely abolished after C1- replacement by NO3-. The Cl(-)-dependent K+ loss in a hypotonic medium was partially (approximately 50%) inhibited by 0.05 mM DIOA ([(dihydroindenyl)oxy]alkanoic acid) and 0.5 mM quinine, but it was unaffected by 0.05 mM bumetanide. These results indicate that the swelling-activated K+, Cl- cotransport is involved in the RVD in frog erythrocytes.

Animals↗
PubMed1999

Immunohistochemistry and spinal projections of the reticular formation in the northern leopard frog, Rana pipiens.

Over 30 nuclei have been identified in the reticular formation of rats, but only a small number of distinct reticular nuclei have been recognized in frogs. We used immunohistochemistry, retrograde tracing, and cell morphology to identify nuclei within the brainstem of Rana pipiens. FluoroGold was injected into the spinal cord, and, in the same frogs, antibodies to enkephalin, substance P, somatostatin, and serotonin were localized in adjacent sections. We identified many previously unrecognized reticular nuclei. The rhombencephalic reticular formation contained reticularis (r.) dorsalis; r. ventralis, pars alpha and pars beta; r. magnocellularis; r. parvocellularis; r. gigantocellularis; r. paragigantocellularis lateralis and dorsalis; r. pontis caudalis, pars alpha and pars beta; nucleus visceralis secundarius; r. pontis oralis, pars medialis and pars lateralis; raphe obscurus; raphe pallidus; raphe magnus; and raphe pontis. The mesencephalic reticular formation contained locus coeruleus-subcoeruleus, r. cuneiformis, r. subcuneiformis, raphe dorsalis-raphe centralis superior, and raphe linearis. Thus, the reticular formation of frog, which is an anamniote, is organized complexly and is similar to the reticular formation in amniotes. Because many of these nuclei may be homologous to reticular nuclei in mammals, we used mammalian terminology for frog reticular nuclei.

Animals↗