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At least 1,099 records · Page 61Linked to original sources
PubMed1969

Extraoptic phase shifting of circadian locomotor rhythm in salamanders.

Timing of locomotor rhythm in the slimy ralamander, Plethodon glutinosus, can be shifted in phase by the environmental light cycle, whether the animals have eyes or not. Rhythmicity persists at least for the first day when animals are transferred to constant conditions, with a period of about 24 hours, and is therefore circadian in nature. An extraoptic photoreceptor site in the brain is suggested.

Animals↗
PubMed1986

Two magnetoreception pathways in a migratory salamander.

Male eastern red-spotted newts (Notophthalmus viridescens) under controlled laboratory conditions exhibit unimodal magnetic compass orientation either in a trained compass direction or in the direction of their home pond. If the vertical component of the magnetic field is inverted, newts exhibiting the simple-compass response undergo a 180 degree reversal in orientation, whereas newts orienting in the home direction are unaffected by this treatment. These results indicate that newts use an axial compass mechanism for simple-compass orientation similar to that found in migrating birds. However, a distinct magnetoreception pathway with polar response properties is involved in homing and is possibly linked in some way to the navigational map.

Adaptation, Physiological↗
PubMed1978

Regeneration of symmetrical hindlimbs in larval salamanders.

The complete circle rule of the polar coordinate model of pattern regulation was tested for regenerating hindlimbs of Ambystoma larvae. The hindlimbs were made symmetrical in the circumference of either the thigh or the shank, and their ability to regenerate from both levels was observed. Thighs composed of two anterior halves failed to regenerate, whereas thighs composed of two posterior halves often regenerated distally complete, correspondingly symmetrical limbs; shanks composed of either two anterior or two posterior halves regenerated distally complete, correspondingly symmetrical limbs. These results are in contrast to what is predicted by the complete circle rule and suggest a modification of this rule.

Ambystoma↗
PubMed1986

Reproduction and the origin of polyploids in hybrid salamanders of the genus Ambystoma.

Eggs and larvae produced by diploid, triploid, and tetraploid females collected from breeding ponds on Pelee Island in Lake Erie were studied to examine the reproductive mechanism. No instance of parthenogenesis was found as all examined females required sperm to produce viable progeny. Diploid females produced diploid and triploid larvae, triploid females produced triploid and tetraploid larvae, and tetraploid females produced triploid and tetraploid larvae. The majority of the eggs produced by hybrid females do not develop or do not complete embryogenesis. Electrophoretic examination of females and their offspring demonstrate that the male genome is being incorporated in reduced as well as unreduced eggs produced by all three ploidy classes of females. The elevation of ploidy among Pelee Island Ambystoma is attributed to sperm incorporation in unreduced eggs. Triploid as well as tetraploid individuals are constantly being produced. A critical examination of the literature on parthenogenetic or gynogenetic modes of reproduction in North America Ambystoma hybrids shows no conclusive evidence supporting these modes and it is suggested that the reproductive mechanism found among Pelee Island female hybrids may be more generally applied to other hybrid Ambystoma populations.

Ambystoma↗
PubMed1989

Conductive pathways for HCO3- in basolateral membrane of salamander intestinal cells.

To understand the route of HCO3- exit across the basolateral membrane of Amphiuma small intestinal cells during active H+ secretion the influence of bath HCO3- on serosal membrane potential (Vs) was measured using conventional microelectrodes. The villus sheet preparation was used, which allowed direct access to the basal membrane for microelectrode impalement. When tissues were incubated in Cl(-)-free (SO2-4 based) medium, Vs averaged -85.8 mV. Elevation of serosal bath [HCO3-] at constant CO2 increased Vs; reduction of the [HCO3-] reduced Vs and increased the fractional resistance of the serosal membrane. When serosal bath HCO3- and CO2 were completely replaced, Vs was -44.8 mV. The serosal membrane was also depolarized on complete replacement of medium HCO3- and CO2 when bath pH was buffered with phosphate. 4,4'-Dinitro-2,2'-stilbene disulfonate (DNDS) and acetazolamide blocked the decline in Vs produced by lowering serosal medium [HCO3-]. Replacement of serosal Na+ reduced Vs 32.7 mV. DNDS blocked this response. It is concluded that a Na+-dependent, stilbene-sensitive HCO3- exit pathway resides in the basolateral membrane of the intestinal cells. Possibly there is also a parallel, conductive pathway for HCO3-.

Acetazolamide↗