Hypothalamo-neurohypophyseal system in two amphibian species “Rana cyanophlyotis and Bufo melanostieus is described. Cytomorphology of the neurosecretory cells in nucleus preopticus is similar to that described for other amphibian species. A majority of neurosecretory cells are unipolar. A few cells are however, bipolar. The cells of nucleus preopticus are disposed off in dorsal and ventral groups. No axonal flow of aldehyde fuehsin positive neurosecretory material could be traced into the third ventricle under normal conditions. Cyclical changes in the content of aldehyde fuchsin positive material in R. cyanophlyctis reveal highest fuchsinophilia in the months of May and July. The cyclical changes seem to correspond with the reproductive phases of the animal. Whereas it is possible to find two morphological types of aldehyde fuhsin positive granules in B. melanosticus, only one type oxists in R. cyanophlyctis. Two morphological types of granules have however, been found in cyanophlyctis under certain experimental conditions Effects of dehydration, salination, inanition and injections of oxytocin, vasopressin and adrenaline have been studied in each species in an identical experimental design. Dehydration, salination, inanition and adrenaline depletes the neureseeretory material in the nucleus preopticus The extent of funchsinophilia is increased with oxytocin. This affects both the dorsal and ventral groups of neurons. There is aittle change if any in vasopressin injected animals. Bioassayable oxytocic and vasopressor activities as recorded in the normal animals are of the order of 24.2+1.15 mu/mg and 31.4+1.75mu/mg and 69.0 _2.7mu/mg respectively in B.melanosticus. Under experimental conditions similar to those employed for cytomorphological investigations, oxytocic activity in salinated and vasopressin treated animals increases, but is reduced to 6.4+1.05 mu/mg in dhydrated animals. There is tittle change in the oxytocic activity in oxytocin treated animals as compared to the normal. The vasopressor activity increases in salinated animals, remains unchanges in vasopressin in injected and dehydrated animals and is deplated in oxytocin treated animals. It has been suggested that assayable activity in the neurointermediate lobe is coincident partly with the increase or decrease of funchsinophilia in the nucleus preopticus. Residual oxytocic activity in dehyindicate the presence of arginine vasopressin, arginine vasotocin and mesotocin. The bioassay data for B. melanosticus under identical experimental conditions has been similarly interpreted and the presence of arginine vasopressin and arginine vasotocin has been suggested. A slow quantal release from neurointermediate lobe, depending upon the circulating levels of these peptides seems to be operative at the level of the neurointermediate lobe Hypothalamic peptides isolated by papert chromatography have been characterized chemically and pharmacologically. Arginine vasopressin and arginine vasotocin are present in both the species. Mesotocin is present only in R. cyanophylctis. Certain peptides with pressor/oxytocic activity or without any activity have been located. That arginine vasotocin exists in at least three polymorphic forms in the two species is indicated from the data obtained. The microheteergenity described is on the chemical rather than pharmacological level. A possible evolution of these hormonal principles is discussed
| Item Type: | Thesis (PhD |
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