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At least 19 recordsLinked to original sources
PubMed1977

Neurophysiological and behavioral evidence for selective reinnervation in skin-grafted Rana pipiens.

Rana pipiens with skin dorosoventrally reversed can respond to stimulation of the back with forelimb wipes to the belly and to stimulation of the belly with hindlimb wipes to the back. These "misdirected wiping responses" have been explained in terms of two alternative hypotheses of nerve regeneration: nerve respecification or selective reinnervation. Experimental behavioral and neurophysiological experiments reported here support the selective reinnervation hypothesis. Severing ventral nerves, which normally innervate the belly, greatly reduced the percentage of misdirected responses on stimulation of belly skin grafted to the back, while severing dorsal nerves, which normally innervate the back, increased the percentage of misdirected responses elicited under the same circumstances. Moreover, neurophysiological recordings of grafted animals showed three effects of skin grafting on nerve distributions: (i) termination of dorsal and ventral nerve receptive field at graft edges; (ii) overlap of nonadjacent ventral nerve receptive fields; and (iii) dorsal coursing of ventral nerves to reinnervate target belly skin displaced to the back. These neurophysiological observations, and particularly the third effect, also support selective reinnervation as the mechanism of nerve regeneration in skin-grafted Rana pipiens.

Action Potentials↗
PubMed1977

Cell turnover in the beak of Rana pipiens.

Rana pipiens tadpoles were injected with 3H-thymidine at different stages to label basal cells of the horny beaks, the keratinized oral specializations of many anuran tadpoles. Cells in the column and sheath of the beak are derived from the basal layer. Movement of the labeled cells in beak columns can be traced, permitting calculation of the rate of cell addition into the columns. With the counts of the total number of column cells and cell addition rate, the rate of apical cell loss from a column throughout the larval stages can also be calculated. The rate of cell addition decreases steadily from stage III through stage XX, in all portions of both beaks. The rate of change of these column cell addition rates is similar among middle and lateral portions of both upper and lower beaks. There is a relatively constant rate of cell loss until stage XII or XIII. It then increases sharply, and the beaks are completely lost at stages XIX or XX. The longer, lower beak columns have a much faster cell loss rate than do the upper beak columns at late larval stages. Life spans for cells that move to the sheath may be about one-half those for cells that enter the beak columns, It is suggested that thyroid hormone accelerates the rate of column cell loss.

Age Factors↗
PubMed1984

Calcium channel inactivation in frog (Rana pipiens and Rana moctezuma) skeletal muscle fibres.

The decay of the Ca2+ current (ICa) during a maintained depolarization was studied in intact twitch skeletal muscle fibres of Rana pipiens and Rana moctezuma with the three-micro-electrode voltage-clamp technique. ICa was recorded at 23 degrees C, after blocking K+ currents, in TEA methanesulphonate saline with 10 mM-Ca2+ made hypertonic by adding 350 mM-sucrose. In two-pulse experiments, ICa during the test pulse was reduced to about 80% (R. pipiens) or 50% (R. moctezuma) of the control value, without any detectable inward ICa during 7 s conditioning pre-pulses. The experimental points of the steady-state inactivation curve (h infinity) were fitted to h infinity = (1 + exp [Em - Vh)/kh]-1, where Em is the membrane potential and with Vh = -33 +/- 3 mV and kh = 6 +/- 1 mV for R. pipiens, and Vh = -44 +/- 3 mV and kh = 9.5 +/- 1.0 mV for R. moctezuma. The rate constant of decay for inactivated currents (range -8 to -47 mA cm-3) and for control currents (range -23 to -62 mA cm-3), was independent of ICa amplitude. The average rate constant of decay at 0 mV was 1.18 +/- 0.02 s-1 (66). These results indicate that in intact fibres under hypertonic solution ICa decay can be explained by a voltage-dependent inactivation process and not by depletion of tubular Ca2+. The absence of depletion could be due to a large fractional tubular volume or to the presence of a Ca2+ pump in the tubular system.

Animals↗
PubMed1986

In vitro ovarian responses to pulsatile and continuous gonadotrophin administration on steroid secretion and oocyte maturation in the frogs, Rana pipiens and Rana catesbeiana.

An in vitro superfusion system was used to study the relative effects of pulsatile and continuous gonadotrophin administration on steroid secretion and oocyte maturation in Rana pipiens ovaries. Pulsatile (10 min pulse/hr) delivery of pituitary extract (PE) resulted in a slightly (insignificantly) lower level of testosterone (T) secretion over a 12-hr period. Administration of a fivefold lower, subliminal amount of PE instead of hormone-free media between pulses did not change the pattern of T secretion. When the interpulse frequency was increased to 2 or 3 hr, there were notable oscillations in T secretion which corresponded to the peaks in luteinizing hormone associated with the PE. In four experiments ovarian fragments underwent oocyte maturation, but this occurred only in fragments that received continuous PE stimulation. Progesterone (P) secretion was measurable only when oocyte maturation was observed in the ovarian fragment. Rana catesbeiana ovarian fragments exposed to continuous superfusion with homologous PE produced more T than those receiving hourly pulses of PE over a 6-hr period. Oocyte maturation accompanied by P secretion was observed in one experiment under continuous, but not pulsatile administration of PE. These results suggest that the frog ovary may be more resistant than the mammalian ovary to "down-regulation" under continuous gonadotrophic stimulation. The implications of these results on the frog pituitary--gonadal axis are discussed.

Animals↗
PubMed2006

Exposures to estradiol, ethinylestradiol and octylphenol affect survival and growth of Rana pipiens and Rana sylvatica tadpoles.

Endocrine disrupting compounds (EDCs) are often detected in the aquatic environment and can negatively affect the health of wildlife populations. However, little is known about the sensitivity of native amphibians to EDCs. Wood frogs (Rana sylvatica) and Northern leopard frogs (Rana pipiens) were exposed to three estrogenic EDCs: estradiol (E2), ethinylestradiol (EE2), and 4-tert-octylphenol (OP). In addition, R. pipiens were exposed during two developmental stages (Gosner stages 26 and 36) to examine life-stage differences in sensitivity. Tadpoles were exposed for 2 wk to 8 nominal concentrations (0.25 microM-10 microM) of each compound. Individual mortality was recorded during the exposure period, while body weight was measured at the end of 2 wk. LC50 values were calculated, and differences in body weight between vehicle control and exposed groups were assessed. Rank order toxicity of the compounds for both R. pipiens stages and both species was OP > EE2 > E2. Gosner stage 26 tadpoles were more sensitive (LC50: E2 [5.57 microM], EE2 [3.01 microM], OP [1.36 microM]) to all three compounds when compared to stage 36 tadpoles (LC50: E2 [>10 microM], EE2 [4.17 microM], OP [2.80 microM]). Interspecies comparisons revealed R. sylvatica tadpoles (LC50: E2 [2.50 microM], EE2 [1.89 microM], OP [0.74 microM]) as being more sensitive to the three compounds than R. pipiens (LC50: E2 [4.56 microM], EE2 [2.75 microM], OP [1.42 microM]). Xenoestrogen exposure also affected tadpole body weight which may have long-term adverse effects on the rate of metamorphosis. These results provide toxicological data needed for assessing sublethal effects of estrogenic compounds on amphibian development and suggest that environmental levels of OP may pose a serious risk to the health of amphibian populations.

Animals↗
PubMed1985

In vitro study of the direct ovarian effects of gonadotropin-releasing hormone (GnRH) in the frogs, Rana pipiens and Rana catesbeiana.

Ovaries from the leopard frog, Rana pipiens, and bullfrog, R. catesbeiana, were used to study potential direct extrapituitary effects of gonadotropin-releasing hormone (GnRH). GnRH alone did not alter steroid secretion from ovaries in either species. Ovarian fragments containing mature follicles from R. pipiens were incubated in several submaximal doses of homologous pituitary homogenate or purified bullfrog luteinizing hormone (LH) together with 1000 ng/ml GnRH. The addition of GnRH failed to alter testosterone (T) or progesterone secretion or germinal vesicle breakdown over a wide dose range of gonadotropin. The effects of supramaximal doses of pituitary homogenate on R. pipiens and the effects of homologous LH on T secretion by fragments of R. catesbeiana ovaries were also unaffected by the presence of GnRH. The lack of a GnRH effect on the dynamics of T secretion in the bullfrog was further confirmed in a superfusion system with homologous pituitary homogenate. This study fails to demonstrate an action of GnRH at the level of the ovary in two ranid species.

Animals↗
PubMed1976

Localization of LHRH in neurons in frog brain (Rana pipiens and Rana catesbeiana).

Hypothalamic extracts from frogs (Rana pipiens) were found to contain a significant quantity of immunoreactive LHRH (3.27 +/- 0.63 ng/hypothalamus) (mean +/- SE) measured by radioimmunoassay. In additional radioimmunoassay studies of gross brain LHRH distribution in R. pipiens and R. catesbeiana, 16% of the total frog brain LHRH was located within the telencephalon-septum-optic chiasm regions while the remainder was distributed within the infundibular hypothalamic-pituitary complex. Immunohistochemical studies using the peroxidase-anti-peroxidase (PAP) unlabeled antibody enzyme technique demonstrated the presence of LHRH selectively within some neuronal perikarya located primarily in the median septal nucleus. Fibers containing immunoreactive LHRH were seen in the vicinity of these neuronal cell bodies and in the medial and lateral septal nuclei. In addition, LHRH-containing fibers extended to the median eminence and posterior pituitary, transversing a course beneath the preoptic recess or through the medial forebrain bundle, and then through the lateral infundibular hypothalamus to enter the median eminence bilaterally. LHRH within the median eminence was located in both the inner subependymal and outer glandular zones. On the basis of earlier physiological studies, it is proposed that this LHRH-peptidergic septo-infundibular pathway is involved in control of cyclic gonadotropin activity in the frog.

Animals↗
PubMed1990

Cell adhesion to extracellular matrix in normal Rana pipiens gastrulae and in arrested hybrid gastrulae Rana pipiens female X Rana esculenta male.

Rana pipiens eggs fertilized by Rana esculenta sperm (ESC) hybrid embryos develop until gastrulation in control Rana pipiens embryos (PIP) and then show morphogenetic arrest. After arrest, ESC do not gastrulate but live for 5 days as blastula-like embryos. We studied the distribution of fibronectin (FN)-containing fibrils and integrin (INT) in PIP and ESC. There are many FN-fibrils in PIP organized in anastomosing networks radiating away from the center of individual cells and across intercellular boundaries. ESC have fewer fibrils compared to PIP. These fibrils are first located between cells in disorganized arrays. After arrest in ESC, when PIP are Stage 14 neurulae, many more FN-fibrils appear. INT-staining occurs in both embryos in similar patterns. In xenoplastic transplantations, we found that the extracellular matrix on the inner surface of the ESC blastocoel roof serves as a substratum for PIP cell migration. In an in vitro assay, we found more cell adhesion to FN-substrata in PIP than in ESC. Cell locomotion rates on FN-substrata were 1.70 +/- 0.85 microns/min for PIP but only 0.46 +/- 0.56 microns/min for ESC. We also found that the inner surface of the blastocoel roof from ESC can not promote cell adhesion and locomotion when Stage 11 fragments are used for conditioning but that Stage 14 fragments can deposit a FN-fibril-rich extracellular matrix which supports PIP mesodermal cell migration at a rate of 1.26 +/- 0.38 microns/min.

Animals↗