Toad

About: Toad is a research topic. Over the lifetime, 1624 publications have been published within this topic receiving 28732 citations.

A sexual dimorphism of the harderian gland of the toad, Bufo viridis.

Abstract: The Harderian gland of the toad, Bufo viridis, is an acinar gland located at the medial corner of the orbit. The columnar glandular cells show considerable variation in height depending upon their functional state. During July they are taller than in November and May, and filled with secretory seromucous granules. The glandular cells of the female toad, only, contain at their base numerous lipid droplets dispersed in a smooth endoplasmic reticulum. This is the first observation of sexual dimorphism in the Harderian gland of a nonmammalian vertebrate. The secretion of the gland is mainly merocrine. Although the secretion of the Harderian gland is mainly concerned with lubrication of the eyeball, the presence of lipid secretion only in the female glandular cells suggests a pheromonale function, which may influence the sexual behaviour of the male.

The importance of glucose for the freezing tolerance/intolerance of the anuran amphibians Rana catesbeiana and Bufo paracnemis.

Abstract: Several species of terrestrially hibernating frogs, turtles and insects have developed mechanisms, such as increased plasma glucose, anti-freeze proteins and antioxidant enzymes that resist to freezing, for survival at subzero temperatures. In the present study, we assessed the importance of glucose to cryoresistance of two anuran amphibians: the frog Rana catesbeiana and the toad Bufo paracnemis. Both animals were exposed to -2 degrees C for measurements of plasma glucose levels, liver and muscle glycogen content, haematocrit and red blood cell volume. Frogs survived cold exposure but toads did not. Blood glucose concentration increased from 40.35 +/- 7.25 to 131.87 +/- 20.72 mg/dl (P < 0.01) when the frogs were transferred from 20 to -2 degrees C. Glucose accumulation in response to cold exposition in the frogs was accompanied by a decrease (P < 0.05) in liver glycogen content from 3.94 +/- 0.42 to 1.33 +/- 0.36 mg/100 mg tissue, indicating that liver carbohydrate reserves were probably the primary carbon source of glucose synthesis whereas muscle carbohydrate seems unimportant. In the toads, the cold-induced hyperglycaemia was less (P < 0.05) pronounced (from 27.25 +/- 1.14 to 73.72 +/- 13.50 mg/dl) and no significant change could be measured in liver or muscle glycogen. Cold exposition had no effect on the haematocrit of the frogs but significantly reduced (P < 0.01) the haematocrit of toads from 20.0 +/- 2.1% to 5.8 +/- 1.7% due to a decreased red blood cell volume (from 1532 +/- 63 to 728 +/- 87 mm3). When toads were injected with glucose, blood glucose increased to levels similar to those of frogs and haematocrit did not change, but this failed to make them cryoresistent. In conclusion, the lack of cold-induced glucose catabolism may not be the only mechanism responsible for the freeze intolerance of Bufo paracnemis, a freeze-intolerant species.

Stimulation by Aldosterone of Active Sodium Transport by the Isolated Colon of the Toad, Bufo marinus

Abstract: DESPITE the large volume and sodium concentration of digestive secretions, the losses of sodium incurred with faeces are negligible in normal circumstances1,2. Return to the organism of sodium present in the intestinal lumen depends in all likelihood on active transport process(es); in the case of the toad colon, this had been established by Ussing and Andersen3, who showed that sodium moves from the mucosal to the serosal surface in the absence of electrochemical potential gradient; furthermore, this movement was expressed quantitatively by the current required to annihilate the electrical potential difference which can be recorded across the membrane.

Regulation of pelvic patch water flow in Bufo marinus : role of bladder volume and ANG II

Abstract: This report examines the importance of bladder volume in regulating cutaneous water uptake (Jv, cm3.cm-2.s-1 x 10(-7)) across the ventral pelvic patch and examines the role of angiotensin II (ANG II) and circulation as the regulatory mechanism. Jv in empty-bladder Bufo marinus (bladder volume 3.89 +/- 1.49%, n = 7) was 1,671 +/- 68 (n = 7). Injection of Ringer solution into the bladder (12.8 +/- 2.2%, n = 7) decreased Jv to 1,025 +/- 202 (n = 7). ANG II injected into toads with filled bladders increased Jv in a dose-dependent manner. At 5 micrograms/100 g toad Jv increased by 136 +/- 63 (n = 6), at 50 micrograms/100 g toad by 432 +/- 82 (n = 7), and at 200 micrograms/100 g toad by 620 +/- 142 (n = 5). Saralasin (200 micrograms/100 g toad) completely inhibited the response to ANG II (50 micrograms/100 g toad) and at 1 mg/100 g toad decreased Jv in empty-bladder toads. These experiments indicate that 1) bladder volume participates in the regulation of Jv in the ventral pelvic patch; 2) ANG II increases the Jv in toads with full bladders; 3) saralasin inhibits the high Jv in empty bladder toads; 4) the high Jv, associated with an empty bladder, requires an intact circulation to be maintained; 5) without an intact circulation, the high water flow associated with an empty bladder causes the Na+ content of the tissue in the ventral patch to be reduced; and 6) ANG II causes only a minimal increases in water permeability in the isolated pelvic patch skin.