Pharmacologic and chromatographic methods were employed to identify the neurohypophysial peptides present in, two species of cyslostomes, the western brook lamprey, Lampetra richardsoni, and the Pacific hagfish, Polistotrema stoutii. The evidence obtained indicated the presence of low amounts of 8-arginine -oxytocin or arginine vasotocin in both animals. No evidence was provided to suggest the existence of a second biologically active posterior pituitary principle in either species, and with the lamprey, it appeared unlikely that more than one percent of the total activity extracted from the neurohypophysial tissues could have been due to a second peptide without being detected. The results of the study thus supported previous claims that cyclo-stomes were unique amoung vertebrates in the possession of a single active neurohypophysial principle. The evolutionary significance of this feature of lamprey and hagfish is discussed, as well as the possibility of the existence, in the pituitary of lower vertebrates, of "intermediate" neurohypophysial peptides with low biological activity. Pharmacologic and chromatographic investigations of midbrain and hind-brain "control" material from the western brook lamprey suggested that small amounts of arginine vasotocin may have been present in these tissues. The possible explanations for this extra-hypothalamic location of a neurohypophysial peptide are discussed, in light of similar findings in other vertebrates. Subsequent to the demonstration of the presence of arginine vasotocin in Lampetra richardsoni, the levels of the peptide were studied in animals of various ages and in larvae kept under various photoperiods. Determinations of the amounts of AVT present in the lamprey during its life history were made in an attempt to corroborate published histological observations which suggested that in Lampetra planeri a marked depletion of the principle occurred at metamorphosis. Although the interpretation of results was complicated by the presence of substantial amounts of contaminating substances in the pituitary extracts, it appeared unlikely that the levels of AVT were drastically reduced at transformation in L. richardsoni. Rather, the data indicated that the amounts of the peptide, as well as the quantities of other active substances in both pituitary and hindbrain tissues, were augmented when larvae transformed into adults. This increase in rat uterus activity extracted from the tissues was correlated with an increase in dry weight of the brain, and it appeared likely that the two occurrences were causally linked. No significant deviations were noted in the rat uterus activity extracted from groups of larval lamprey kept under different photoperiods. The variations that occurred amoung the neurohypophysial tissues were paralleled by differences amoung the control tissues; this suggested that photoperiod had effects on other biologically active subatances in the central nervous system besides AVT. / Science, Faculty of / Zoology, Department of / Graduate

No description available.

Marine mussels accumulate amino acids and glucose from seawater against considerable concentration gradients. The principal site for this uptake is the gill. Previous studies using intact, isolated gills from marine mussels have suggested that the transport mechanism involves coupling to Na⁺, similar to the mechanism of secondary active transport of amino acids and glucose in vertebrate epithelia, but until this dissertation there had been no rigorous test of this hypothesis. Brush border membrane vesicles (BBMV) were prepared from the gills of the marine mussel, Mytilus edulis, by differential and sucrose density centrifugation. The preparation procedure isolated a population of membranes enriched in brush border membrane markers. The transport of amino acids by two pathways, the alanine-lysine pathway (AK) and the alanine-proline pathway (AP), and the uptake of glucose was studied in the BBMV. The mechanism of transport through the three transport pathways is BBMV involved coupling to Na⁺. Concentrative uptake through the AK pathway, which transported alanine and lysine, also occurred in the presence of Li⁺ and K⁺ gradients. This pathway was the major route for alanine transport in BBMV. The AP pathway transported alanine and proline, and was strictly dependent on Na⁺. Glucose transport in gill BBMV resembled quite closely the Na⁺-coupled transport of glucose in vertebrate epithelia in such characteristics as Na⁺ and substrate specifically, and electrogenicity. Transport through the two amino acid uptake pathways (AK and AP) and through the glucose uptake pathway could be described by Michaelis-Menten kinetics, with high substrate affinities (K(t)'s below 10 μM). Furthermore, it is likely that multiple Na⁺ ions are involved in the transport of these amino acids and glucose in mussel gill BBMV. It appears that these transporters are adapted for function at low substrate concentrations and against large concentration gradients.

No description available.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 5 uppsatser.

Thesis (Ph.D.) -- University of Adelaide, Dept. of Animal Physiology, 1971. / Includes bibliographical references (leaves 281-328).

Thesis (Ph.D.)--University of Adelaide, School of Molecular and Biomedical Sciences, Discipline of Physiology, 2004. / Bibliography: leaves 161-189.

Thesis (doctoral)--Rijksuniversiteit te Utrecht.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1969. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.