No description available.

No description available.

by Fung Chak-yan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1980. / Bibliography: leaves 181-224.

No description available.

The richness of nervous systems represented by extant fishes has not yet been determined; the brain morphology of many species, indeed, many groups, remain undescribed. For this reason we have examined esociform teleosts and focused on three goals: 1) to provide the first basic descriptions of the brains of two esociform teleosts, Esox masquinongy (muskellunge) and Esox lucius (northern pike); 2) to describe the development of E. masquinongy brains; and 3) to compare the neuronal features between E. masquinongy and E. lucius in light of the ontogenic pattern of E. masquinongy. We demonstrate that a suite of differences exists between the brains of these two congeners. Relative to the brains of E. lucius, the brains of E. masquinongy exhibit a number of paedomorphic features. This heterochronic shift parallels the differences in non-neuralmorphological features previously described between these two species. We identify three features that cannot be explained by this heterochronic shift: 1) the optic nerves of E. masquinongy and E. lucius cross oppositely, E. masquinongy have optic nerves that cross left nerve dorsal, E. lucius cross right nerve dorsal; 2) Esox lucius have a consistent cellular discontinuity in the telencephalon between Dm, and Dd that is not present in E. masquinongy; and 3) adult E. lucius retain a neural canal opening that closes in larval E. masquinongy, a peramorphic exception to the paedomorphic pattern. / Department of Physiology and Health Science

Thesis (Ph.D.)--University of Hawaii at Manoa, 1994. / Includes bibliographical references (leaves 112-114). / Microfiche. / xi, 117 leaves, bound ill. 29 cm

At a late stage of spermatogenesis a sperm-specific protein, protamine, is synthesized in the testis of salmonid fish and progressively replaces histones in combination with DNA. Protamine has a molecular weight near 5,000 and contains 2/3 of its total amino acid residues as arginine. Studies on the biosynthesis of protamine have been made on the rainbow trout (Salmo gairdnerii) testis. Successive column chromatography on Bio-Gel P-10 and CM- cellulose has been employed to isolate and characterize newly synthesized labelled protamine. Newly synthesized protamine is phosphorylated and is eluted earlier from the CM-cellulose column than mature protamine. However, the two forms of protamine chromatograph coin-cidentally when newly synthesized protamine is first treated with alkaline phosphatase. Protamine is separated into three components on CM-cellulose and the amino acid compositions of the components are very similar. The relative amounts of the components present in the testis nuclei are different at different stages of spermatogenesis and the synthesis of each component appears to be independently controlled. This suggests that the components, while chemically very similar, are the products of separate structural genes and may have different functions. By pulse labelling testis cell suspensions for different lengths of time and analyzing the amount of ¹⁴C- protamine found in the cytoplasm and in the nucleus, the site of protamine synthesis can be shown to be in the cytoplasm. Further, a cell-free, isolated post-mitochondrial cytoplasmic fraction can incorporate ¹⁴C-arginine into whole protamine molecules, while both an isolated nuclear fraction and high-speed supernatant were relatively inactive. This indicates that protamine synthesis occurs on cytoplasmic microsomes. Sedimentation analysis of pulse-labelled testis ribososes indicates that protamine is synthesized on a class of small polysomes, the disomes, sedimenting at 120S. While dimeric ribosomes investigated in various tissues have been shown to be inactive artefacts formed during isolation, the disomes in trout testis have been demonstrated to be a functional class of polysomes. They are not dissociable at 1 mM Mg⁺⁺ ion concentration, are not the breakdown product of larger polysomes, nor are they produced by interaction with free protamine. These disomes contain the major quantity of nascent protamine and increase in number in the testis cells during the active protamine synthesizing stage of development. The probable function of protamine is for the packaging of DNA into the sperm head. The phosphorylation of protamine and the protamine components may serve to regulate this packaging process. / Medicine, Faculty of / Biochemistry and Molecular Biology, Department of / Graduate

The blue gourami (Trichogaster trichopterus), does not appear to go through a ritualized prespawning behavior sequence. The female is apparently brought into a state of sexual activity as a result of the presence of a dark, nest building male. Spawning is initiated by the female and it consists of a stereotyped cycle of behavioral events. In the majority of cases, male castration results in the cessation of nest building, a reduction of colour change, a partial atrophy of the morphological secondary sexual characteristics (S.S.C.), and the absence of spawning. Treatment with methyl testosterone brings back all of these characteristics. In a few cases, castration resulted in only a partial reduction of nest-building, colour change and morphological secondary sexual characteristics and the retention of spawning. It is tentatively suggested that there may be an extragonadal source of androgen. It seems the physical act of spawning is necessary to trigger full parental behavior regardless of gonadal condition. Agonistic behavior is not apparently affected by castration. Methyl testosterone given to unoperated females resulted in male-like agonistic behavior, coloration, secondary sexual characteristics and some evidence of nest building. / Science, Faculty of / Zoology, Department of / Graduate

A theoretical analysis of the acoustic field around a sound source suggested that fish would be able to locate a sound source by detecting the associated near field displacements with their lateral line system. Blinded goldfish and Mexican blind cave characins were able to locate both stationary objects and sound sources. The lateral line system was implicated as the directionally sensitive organs involved. Blind cave fish were able to locate both stationary objects and a sound source against a background noise. The existence of a noise suppressing mechanism to the lateral line organs was suggested. An efferent nervous supply was shown to innervate anterior lateral line organs of goldfish, and the inhibitory nature of the efferent nerves was demonstrated. The efferent nerves were found to be insensitive to the stimulation of acoustically sensitive organs on the fish, but responded to changing states of muscular activity in the fish. Swimming goldfish changed hydrodynamically during respiration from bluff bodies, when their mouths were shut, to streamlined bodies, when their mouths were open. This change in configuration lead to the proposal that the anterior lateral line organs function both as velocity detectors and near field displacement detectors. A central location was suggested for a neuro-physiological noise attenuating system to the lateral line system, and the efferent nerves innervating the lateral line organs were suggested to form part of a mechanism reflexively controlling swimming velocity. / Science, Faculty of / Zoology, Department of / Graduate

No description available.