The development of the tetrasporangium of Antithamnion subulatum (Harvey) J.G. Agardh was studied using light and electron microscopy in order to elucidate the origin of proplastids, and the continuity of chloro-plasts during the production of the tetraspore. The results show that proplastids arise through a "blebbing" process of the mature chloroplasts.This results in the production of proplastids which are identical to those found free in the cytoplasm of the tetra-sporangial mother cell, and are in most respects similar to proplastids observed by others in the apical regions of other red algae. The inclusion of a single DNA-containing genophore within the forming proplastids strongly suggests that each of the scattered genophores in the mature chloroplasts contains at least one complete genome. Division of mature chloroplasts was not seen within the tetra-sporangial mother cell or the tetrasporangial initial. However, within the young tetrasporangium the mature chloroplasts appear to undergo several simultaneous divisions resulting in numerous smaller discoid plastids. It is these plastids which, through a succession of growth and division phases, make the major contribution to the continuity of chloroplasts in the formation of the tetraspore, rather than the proplastids which have been produced in low numbers throughout its development. The colourless nature of the young tetrasporangium is not due to the presence of a high concentration of proplastids, but rather is related to the high frequency of chloroplast division, resulting in membrane production being much more rapid than phycobilisome formation. / Science, Faculty of / Botany, Department of / Zoology, Department of / Graduate

Methodologies that detect biologically active substances have important potential applications for medical diagnostics, drug discovery, and chemical and biological anti-terrorism efforts. The wide spectrum of potential analytes that induce a physiological response dictates that novel techniques be developed to more rapidly screen and characterize agents that are more economical and have greater sensitivity than current practices. The research presented in this dissertation describes the development of a biosensor methodology that utilizes optical changes in naturally pigmented chromatophore cells from fish to detect and measure an array of biochemicals and protein toxins. The chromatophores used in this biosensor were harvested from teleost fish sources and the observed patterns of pigment aggregation and dispersion in response to added chemical modulators were used as a reporter mechanism. Differential responses between chromatophore subtypes were utilized as simple cellular sensors for the detection of cholera toxin and in the study of the calcium signaling requirements in these cells. A multi-cellular biosensor was developed that couples pigmentation changes in erythrophores from the teleost Betta splendens with mammalian nerve cell secretory activity. An apparatus was developed that placed PC12 cells, a neuroendocrine cell line, and erythrophores in adjacent chambers connected by a fluid network that allowed erythrophores to be exposed to effluent from PC12 cells; neurotransmitters secreted from PC12 cells induced pigment aggregation in erythrophores. By analyzing the extent of this erythrophore response, this method was capable of detecting the occurrence of substances that altered neurotransmitter secretion levels. A demonstration of this biosensor is presented that detected the inhibition of neurosecretory activity caused by the pathogenic bacterial toxin botulinum, the causative agent of human botulism. / Graduation date: 2002

No description available.

Thesis (M.A.)--Boston University

No description available.

Deep continuous layers of iridophores were discovered in certain Asian Agkistrodon species. A survey of available snakes showed the banded iridophores to be present in North American Crotalus and Sistrurus also, indicating an unreported morphology to be a possible common phenomenon. Skin samples from 147 species and/or subspecies of snakes of the families Leptotyphlopidae, Boidae, Colubridae, Elapidae and Viperidae were examined and photographed by polarized light microscopy. Dermal iridophore patterns were visually identified and categorized as (1) isolated cells, (2) lightly layered, (3) moderately layered and (4) heavily layered. Selected specimens were examined and photographed by electron microscopy; isolated iridophore ultrastructure and layered iridophore ultrastructure patterns are illustrated and described. Reflectometry of four selected crotalids reveals positive correlation between iridophore quantities and albedo, but habitat adaptation and correlation of individual species/subspecies is difficult to show and only subjectively suggested. Published phylogenies of the species of the genera Agkistrodon, Calloselasma, Deinagkistrodon and Hypnale are revised to reflect taxonomic works and are correlated with iridophore pattern data. Phylogenetic relationships of Crotalus and Sistrurus are also revised with recent publications; they are neither supported nor contradicted because layered iridophores occur in all of their phylogenetic groups.

No description available.

No description available.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1966. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1968. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.