Elasmobranch fishes use electroreception to detect electric fields in the environment, particularly minute bioelectric fields produced by potential prey. A single elasmobranch family (Potamotrygonidae) is composed of obligate freshwater stingrays endemic to the Amazon River. A freshwater existence has imposed morphological adaptions on their electrosensory system due to life in a high impedance medium. Because their electrosensory morphology differs from their marine relatives, freshwater stingrays may demonstrate corresponding differences in behavioral sensitivity. The objective of this study was to quantify behavioral sensitivity of the obligate freshwater stingray Potamotrygon motoro to prey-simulating voltage. The voltage produced by common teleost prey of P. motoro were measured and replicated for behavioral trials. The best response was 10.62 cm, and the smallest voltage gradient detected was 0.005 mVcm-1. This sensitivity is reduced compared to marine species. The conductivity of the medium, more so than ampullary morphology, may dictate sensitivity of the elasmobranch electrosensory system. / by Lindsay L. Harris. / Thesis (M.S.)--Florida Atlantic University, 2013. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

by Simon Chan Siu Hoi. / Spine title varies. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (leaves 130-148). / Acknowledgments --- p.i / Table of Contents --- p.ii / List of Abbreviations --- p.ix / List of Figures --- p.xiii / List of Tables --- p.xvi / Page / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Growth Hormone --- p.1 / Chapter 1.2 --- Growth Hormone Receptor --- p.3 / Chapter 1.2.1 --- Cytokine/Hematopoietin Receptor Superfamily --- p.3 / Chapter 1.2.2 --- Tissue Distribution of GHR --- p.6 / Chapter 1.2.3 --- Biosynthesis and Degradation of GHR --- p.7 / Chapter 1.2.4 --- Regulation of GHR Level --- p.8 / Chapter 1.2.5 --- The GHR Protein --- p.10 / Chapter 1.2.6 --- The GHR Gene --- p.15 / Chapter 1.2.7 --- GHR Dimerization --- p.16 / Chapter 1.2.8 --- Mechanism of Signaling by GHR --- p.19 / Chapter 1.2.9 --- GH Binding Protein --- p.21 / Chapter 1.2.10 --- GHR Related Dwarfism --- p.23 / Chapter 1.3 --- Objectives of the Present Investigation --- p.25 / Chapter Chapter 2 --- Materials and Methods --- p.27 / Chapter 2.1 --- Fish Growth Hormone Radioactive Labeling --- p.27 / Chapter 2.1.1 --- Preparation of Iodogen-Coated Tubes --- p.27 / Chapter 2.1.2 --- Packing of the Sephadex G-75 Column --- p.28 / Chapter 2.1.3 --- Iodination of brGH and Purification of the Iodinated brGH --- p.28 / Chapter 2.1.4 --- Determination of the Specific Radioactivity and Percentage of 125I Incorporation --- p.29 / Chapter 2.1.5 --- Reagents and Buffers Used --- p.30 / Chapter 2.2 --- Integrity of 125I-brGH --- p.30 / Chapter 2.2.1 --- HPLC of brGH --- p.31 / Chapter 2.2.2 --- HPLC of 125I-brGH after Iodination --- p.31 / Chapter 2.2.3 --- HPLC of 125I-brGH after Receptor Binding --- p.31 / Chapter 2.3 --- Preparation of Membranes from Fish Tissues --- p.32 / Chapter 2.3.1 --- Preparation of Snakehead Fish Liver Membranes --- p.32 / Chapter 2.3.2 --- Reagents and Buffers Used --- p.33 / Chapter 2.4 --- Protein Determination of Membrane Preparations --- p.34 / Chapter 2.4.1 --- The BCA Protein Reaction Scheme --- p.34 / Chapter 2.4.2 --- BCA Protein Determination Protocol --- p.34 / Chapter 2.5 --- Receptor Binding Studies --- p.35 / Chapter 2.5.1 --- Association and Dissociation Studies --- p.36 / Chapter 2.5.2 --- pH Dependence Study --- p.36 / Chapter 2.5.3 --- Membrane Protein Dependence Study --- p.37 / Chapter 2.5.4 --- Ca2+ Dependence Study --- p.37 / Chapter 2.5.5 --- Tissue Distribution Study --- p.37 / Chapter 2.5.6 --- Displacement and Specificity Studies --- p.38 / Chapter 2.5.7 --- Dithiothreitol (DTT) Dependence Study --- p.39 / Chapter 2.5.8 --- p-Chloromercuribenzene Sulfonate (PCMBS) Pretreatment: Dose Dependence Study --- p.39 / Chapter 2.5.9 --- Scatchard Analysis of the PCMBS Pretreated and Control Snakehead Fish Liver Membranes --- p.40 / Chapter 2.5.10 --- Reversibility of the PCMBS Effect --- p.40 / Chapter 2.5.11 --- Reagents and Buffers Used --- p.41 / Chapter 2.6 --- Crosslinking Studies --- p.41 / Chapter 2.6.1 --- Crosslinking Performed on Snakehead Fish Liver Membranes --- p.41 / Chapter 2.6.2 --- Crosslinking Performed on Solubilized Snakehead Fish Liver Membranes --- p.42 / Chapter 2.6.3 --- Gel Filtration Chromatography of the Crosslinked Comp)lexes --- p.43 / Chapter 2.6.4 --- Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis (SDS-PAGE) of the Crosslinked Complexes --- p.43 / Chapter 2.6.5 --- Reagents and Buffers Used --- p.45 / Chapter 2.7 --- Western Blot Analysis of Snakehead Fish Liver GHR --- p.46 / Chapter 2.7.1 --- SDS-PAGE of Snakehead Fish Liver Membranes --- p.46 / Chapter 2.7.2 --- Transfer of Proteins onto Polyvinylidene Fluoride (PVDF) Membrane --- p.46 / Chapter 2.7.3 --- Antibody Development of PVDF Membrane --- p.47 / Chapter 2.7.4 --- Reagents and Buffers Used --- p.48 / Chapter 2.8 --- Solubilization of Snakehead Fish Liver Membranes and Solubilized Receptor Binding Studies --- p.48 / Chapter 2.8.1 --- Solubilization of Snakehead Fish Liver Membranes --- p.49 / Chapter 2.8.2 --- Solubilized Receptor Binding Assay --- p.49 / Chapter 2.8.3 --- "Solubilization of Snakehead Fish Liver Membranes: Detergent Concentration, pH, Temperature and Time Dependence" --- p.50 / Chapter 2.8.4 --- Solubilized Receptor Binding Study: Interference of Detergent --- p.50 / Chapter 2.8.5 --- Reagents and Buffers Used --- p.51 / Chapter 2.9 --- Purification of Snakehead Fish Liver GHR by Affinity Chromatography --- p.51 / Chapter 2.9.1 --- Affinity Column Preparation --- p.52 / Chapter 2.9.2 --- Snakehead Fish Liver GHR Purification --- p.52 / Chapter 2.9.3 --- Reagents and Buffers Used --- p.53 / Chapter Chapter 3 --- Results: fGH Labeling and Integrity Determination --- p.54 / Chapter 3.1 --- Introduction --- p.54 / Chapter 3.2 --- Experimental Results --- p.55 / Chapter 3.2.1 --- Iodination of fGH --- p.55 / Chapter 3.2.2 --- Integrity of 125I-fGH --- p.55 / Chapter 3.3 --- Discussion --- p.61 / Chapter Chapter 4 --- Results: Membrane Receptor Binding Studies --- p.62 / Chapter 4.1 --- Introduction --- p.62 / Chapter 4.2 --- Experimental Results --- p.63 / Chapter 4.2.1 --- Optimal Conditions for Snakehead Fish Liver Membrane GHR Binding --- p.64 / Chapter 4.2.1.1 --- Association and Dissociation Studies --- p.64 / Chapter 4.2.1.2 --- pH Dependence Study --- p.67 / Chapter 4.2.1.3 --- Membrane Protein Dependence Study --- p.70 / Chapter 4.2.1.4 --- Ca2+ Dependence Study --- p.73 / Chapter 4.2.2 --- Localization and Specificity of Snakehead Fish GHR --- p.76 / Chapter 4.2.2.1 --- Tissue Distribution Study --- p.76 / Chapter 4.2.2.2 --- Displacement and Specificity Studies --- p.78 / Chapter 4.2.3 --- Effects of Sulfhydryl Group Reducing and Oxidizing Agents on GHR Binding --- p.81 / Chapter 4.2.3.1 --- Effect of DTT: Concentration Dependence Study --- p.81 / Chapter 4.2.3.2 --- Effect of PCMBS: Concentration Dependence Study --- p.84 / Chapter 4.2.3.3 --- Scatchard Analysis of Control and PCMBS- pretreated Membranes --- p.86 / Chapter 4.2.3.4 --- Reversibility of the PCMBS Effect --- p.88 / Chapter 4.3 --- Discussion --- p.90 / Chapter 4.3.1 --- Optimal Conditions for Snakehead Fish Liver Membrane GHR Binding --- p.90 / Chapter 4.3.2 --- Localization and Specificity of Snakehead Fish GHR --- p.93 / Chapter 4.3.3 --- Effects of Sulfhydryl Group Reducing and Oxidizing Agents on GHR Binding --- p.96 / Chapter Chapter 5 --- Results: Crosslinking and Western Blot Analysis --- p.101 / Chapter 5.1 --- Introduction --- p.101 / Chapter 5.1.1 --- Crosslinking Studies --- p.101 / Chapter 5.1.2 --- Western Blot Analysis --- p.103 / Chapter 5.2 --- Experimental Results --- p.104 / Chapter 5.2.1 --- Crosslinking Studies --- p.104 / Chapter 5.2.2 --- Western Blot Analysis --- p.105 / Chapter 5.3 --- Discussion --- p.112 / Chapter Chapter 6 --- Results: Affinity Purification of Snakehead Fish Liver GHR --- p.115 / Chapter 6.1 --- Introduction --- p.115 / Chapter 6.1.1 --- Membrane Solubilization and Solubilized GHR Binding Studies --- p.115 / Chapter 6.1.2 --- Affinity Purification of Solubilized Snakehead Fish Liver GHR --- p.116 / Chapter 6.2 --- Exp erimental Results --- p.117 / Chapter 6.2.1 --- Solubilization of Snakehead Fish Liver Membranes --- p.117 / Chapter 6.2.2 --- Interference of Detergents in the Solubilized Receptor Binding Assay --- p.118 / Chapter 6.2.3 --- Affinity Purification of Solubilized Snakehead Fish Liver GHR --- p.120 / Chapter 6.3 --- Discussion --- p.122 / Chapter Chapter 7 --- General Discussion --- p.125 / References --- p.130

Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2009. / Committee Co-Chair: Rogers, Peter; Committee Co-Chair: Yoda, Minami; Committee Member: Giddens, Don; Committee Member: Sotiropoulos, Fotis; Committee Member: Trivett, David; Committee Member: Yen, Jeanette. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Made available in DSpace on 2016-01-13T13:28:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-07-14. Added 1 bitstream(s) on 2016-01-13T13:33:48Z : No. of bitstreams: 1 000855099.pdf: 2014211 bytes, checksum: a9a888733e55b0a07c793c08d14149ba (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / A aquicultura brasileira apresenta-se como atividade comercial em franca ascensão e, dentre as espécies nativas, o pacu, Piaractus mesopotamicus, destaca-se como uma das mais cultivadas nas regiões Sul, Sudeste e Centro Oeste do Brasil. Contudo, à semelhança do que ocorre com as demais espécies de interesse comercial, a produção do pacu enfrenta problemas ao longo do processo produtivo, tais como a alta densidade populacional utilizada, fornecimento incorreto de rações e estresse, que resultam em redução da produtividade e aumento na taxa de mortalidade. Uma das estratégias estudadas para melhorar o manejo alimentar em peixes consiste na utilização da privação alimentar por tempo determinado com a finalidade de promover compensação do crescimento, durante o período de realimentação. Entretanto, informações relacionadas às respostas fisiológicas, de modulação celular e de possíveis alterações na microbiota intestinal provocada por este tipo de manejo ainda são discordantes. A compreensão destas informações é necessária para o desenvolvimento de estratégias que minimizem o estresse ocasionado pela privação alimentar. Diante do exposto, a proposta deste trabalho foi avaliar o impacto do jejum prolongado, seguido de curto período de realimentação, sobre os parâmetros fisiológicos, expressão de genes relacionados ao processo de crescimento e estresse, prevalência de determinados grupos bacterianos na mucosa e conteúdo intestinal, além da clonagem, identificação e validação de genes de referência para normalização de dados de expressão gênica em estudos com pacus. Os resultados obtidos demonstraram que o pacu apresenta grande capacidade de mobilização das reservas endógenas, porém a recuperação das mesmas é mais rápida em peixes de menor tamanho. O presente estudo apresenta as primeiras comparações experimentais para validação de genes de referência para o pacu. Os genes clonados... / The Brazilian aquaculture is as a commercial activity on the rise. Among the native species, pacu, Piaractus mesopotamicus, stands out as one of the most reared in the southern, central and northeastern Brazil. However, similar to what occurs with other commercial species, the production of pacu experience problems during the production process, such as high population density used, incorrect food supply and stress, resulting in reduced productivity and increased mortality. One of the strategies investigated to improve the management of fish feeding is the use of dietary restrictions for a certain time to promote growth compensation during the refeeding period. However, information related to physiological responses and cell modulations caused by this type of management are still unknown. Understanding this information is necessary for the development of strategies to minimize the stress caused by food restriction. The purpose of this study was to evaluate the impact of prolonged fasting, followed by short refeeding on the physiological parameters, gene expression related to growth and stress, the prevalence of certain bacterial groups in the mucosa and intestinal content and cloning, identification and validation of reference genes for normalization of gene expression data in studies with pacu. The results showed that the pacu has great capacity for mobilization of endogenous reserves, but their recovery is faster in smaller fish. This study presents the first experimental comparisons for validation of reference genes for pacu. Cloned, sequenced and validated genes will be used in future studies of gene expression with this species. In addition, this study provides the first information about the changes in intestinal microbiota in pacu. The use of qPCR for the detection and quantification of specific bacterial groups proved to be an important tool for assessing changes in bacterial communities in the mucosa and intestinal contents of fish / CNPq: 153589/2011-6

Orientador: Luiz Edivaldo Pezzato / Coorientador: Luiz Roberto Furlan / Banca: Elisabeth Criscuolo Urbinati / Banca: Jesus Aparecido Ferro / Banca: Maria Célia Portella / Banca: Eduardo Gianini Abimorad / Resumo: A aquicultura brasileira apresenta-se como atividade comercial em franca ascensão e, dentre as espécies nativas, o pacu, Piaractus mesopotamicus, destaca-se como uma das mais cultivadas nas regiões Sul, Sudeste e Centro Oeste do Brasil. Contudo, à semelhança do que ocorre com as demais espécies de interesse comercial, a produção do pacu enfrenta problemas ao longo do processo produtivo, tais como a alta densidade populacional utilizada, fornecimento incorreto de rações e estresse, que resultam em redução da produtividade e aumento na taxa de mortalidade. Uma das estratégias estudadas para melhorar o manejo alimentar em peixes consiste na utilização da privação alimentar por tempo determinado com a finalidade de promover compensação do crescimento, durante o período de realimentação. Entretanto, informações relacionadas às respostas fisiológicas, de modulação celular e de possíveis alterações na microbiota intestinal provocada por este tipo de manejo ainda são discordantes. A compreensão destas informações é necessária para o desenvolvimento de estratégias que minimizem o estresse ocasionado pela privação alimentar. Diante do exposto, a proposta deste trabalho foi avaliar o impacto do jejum prolongado, seguido de curto período de realimentação, sobre os parâmetros fisiológicos, expressão de genes relacionados ao processo de crescimento e estresse, prevalência de determinados grupos bacterianos na mucosa e conteúdo intestinal, além da clonagem, identificação e validação de genes de referência para normalização de dados de expressão gênica em estudos com pacus. Os resultados obtidos demonstraram que o pacu apresenta grande capacidade de mobilização das reservas endógenas, porém a recuperação das mesmas é mais rápida em peixes de menor tamanho. O presente estudo apresenta as primeiras comparações experimentais para validação de genes de referência para o pacu. Os genes clonados... / Abstract: The Brazilian aquaculture is as a commercial activity on the rise. Among the native species, pacu, Piaractus mesopotamicus, stands out as one of the most reared in the southern, central and northeastern Brazil. However, similar to what occurs with other commercial species, the production of pacu experience problems during the production process, such as high population density used, incorrect food supply and stress, resulting in reduced productivity and increased mortality. One of the strategies investigated to improve the management of fish feeding is the use of dietary restrictions for a certain time to promote growth compensation during the refeeding period. However, information related to physiological responses and cell modulations caused by this type of management are still unknown. Understanding this information is necessary for the development of strategies to minimize the stress caused by food restriction. The purpose of this study was to evaluate the impact of prolonged fasting, followed by short refeeding on the physiological parameters, gene expression related to growth and stress, the prevalence of certain bacterial groups in the mucosa and intestinal content and cloning, identification and validation of reference genes for normalization of gene expression data in studies with pacu. The results showed that the pacu has great capacity for mobilization of endogenous reserves, but their recovery is faster in smaller fish. This study presents the first experimental comparisons for validation of reference genes for pacu. Cloned, sequenced and validated genes will be used in future studies of gene expression with this species. In addition, this study provides the first information about the changes in intestinal microbiota in pacu. The use of qPCR for the detection and quantification of specific bacterial groups proved to be an important tool for assessing changes in bacterial communities in the mucosa and intestinal contents of fish / Doutor

Ph.D. (Zoology) / Please refer to full text to view abstract

The characteristics of the ion exchange mechanisms which regulate volume and pH in fish and amphibian erythrocytes were investigated and compared. Experiments were carried out under steady state conditions and also following adrenergic stimulation both in vivo and in vitro. Under steady state conditions, a decrease in extracellular pH caused an increase in the volume of rainbow trout erythrocytes, and a decrease in the intracellular pH. These pH-induced volume changes were mainly associated with movements of chloride across the chloride/bicarbonate exchange pathway. The sodium/proton exchange mechanism is quiescent at all pH's studied under steady state conditions. Beta adrenergic stimulation of rainbow trout erythrocytes promoted cell swelling and proton extrusion from the erythrocytes. Amiloride inhibited both the volume and pH changes associated with adrenergic stimulation indicating that this response is associated with an increase in the activity of the sodium/proton exchange mechanism on the erythrocyte membrane. The adrenergic swelling and pH responses are enhanced by a decrease in extracellular pH. An increase in bicarbonate concentration reduces the adrenergic pH response, but it is still significant even at 10 mM bicarbonate. DIDS markedly enhanced the beta adrenergic effect on the erythrocyte pH, but abolished the increase in erythrocyte volume. The adrenergic response was independent of temperature between 10 and 18°C. These results support a loosely coupled sodium/proton and chloride/bicarbonate exchange model for the adrenergic response in rainbow trout erythrocytes. The increases in erythrocyte pH and volume following adrenergic stimulation are associated with increases in the haemoglobin:oxygen affinity. The oxygen carrying capacity of the blood is, therefore, increased following adrenergic stimulation in rainbow trout. Carbon dioxide excretion, however, was not significantly affected by adrenergic stimulation. The functional significance of the adrenergic response of fish erythrocytes may be to offset the effects of the Root shift on the oxygen carrying capacity of the blood during acute changes in extracellular pH. In contrast to fish erythrocytes, the sodium/proton exchange mechanism in amphibian erythrocytes is active under steady state conditions. In the presence of bicarbonate movements, this exchange significantly affects the erythrocyte volume, but not the erythrocyte pH. Similar to fish erythrocytes, protons are passively distributed in amphibian erythrocytes under steady state conditions and in Donnan equilibrium with chloride ions. The erythrocyte volume also increases with decreases in extracellular pH as in fish erythrocytes, due to changes in the chloride distribution across the erythrocyte membrane. Adrenergic stimulation does not affect the volume or pH of amphibian erythrocytes either in vivo or in vitro. These animals, therefore, do not appear to regulate erythrocyte pH adrenergically. Amphibians are able to efficiently utilize oxygen stores via both central and peripheral shunting. In addition, the blood of these animals does not have a Root shift. Adrenergic regulation of erythrocyte pH in order to enhance oxygen transport during fluctuations in ambient and internal gas tensions, therefore, is probably less important than it would be in fish. / Science, Faculty of / Zoology, Department of / Graduate

The distribution and transfer of ammonia between intracellular and extracellular compartments of fish and the external water environment was investigated. In vivo and in vitro experiments were performed on the freshwater rainbow trout (Salmo gairdneri) and the intact, seawater lemon sole (Parophrys vetulus). The distribution of ammonia and H⁺ ions were compared between red cells and plasma (in vivo and in vitro) taken from rainbow trout at rest and during hypercapnia. At rest (in vivo and in vitro) measured intracellular ammonia levels were equal to those predicted by the plasma to red cell pH gradient. The same was not true during hypercapnia, where measured red cell ammonia levels were greater than predicted levels. The addition of the Na⁺/K⁺ ATPase inhibitor, ouabain, had no effect on ammonia accumulation during hypercapnia. It was concluded that ammonia is passively distributed according to plasma-to-red cell H⁺ ion distribution in blood at resting pH values, but under hypercapnic conditions, ammonia accumulation must be due to some other active uptake mechanism. The distribution of ammonia and ¹⁴C-DMO were compared in white muscle, heart, brain, red cells, and plasma of lemon sole (in vivo) at rest, during hypercapnia, and following exercise. The red cell ammonia distribution at rest and during an extracellular acidosis (hypercapnia and exercise) was similar to that found in rainbow trout. Red cells are unusual in that H⁺ ions are passively distributed according to membrane potential (Em), whereas in other tissues, this is not the case. In white muscle, heart, and brain under all experimental conditions, intracellular ammonia levels far exceeded those predicted by transmembrane pH gradients. Calculated ENH₄₊ values in these tissues were very close to published resting values of Em. It was concluded that NH₄₊ is permeable across cell membranes and that intracellular ammonia stores are not determined by transmembrane pH gradients in lemon sole. The pH of interlamellar water was investigated in rainbow trout by following changes in the downstream pH of expired water using a stopped-flow method. As water flowed over the gills of control fish, there was a significant decrease in water pH. Acetazolamide (carbonic anhydrase (CA) inhibitor) added to the water increased the CO₂ disequilibrium, while CA eliminated the CO₂ disequilibrium relative to control water. Mucus excreted by the fish was found to contain CA activity by the pH-stat technique. It was concluded that water acidification is due to the conversion of excreted CO₂ to HCO₃₋ and H+ at the gill surface. A possible function of CA at the external gill surface is to facilitate carbon dioxide and ammonia excretion. Acetazolamide or CA added to the water did not alter carbon dioxide (MCO₂) or ammonia (MAmm) excretion in intact rainbow trout. Methazolamide (CA inhibitor) or methazolamide + amiloride (Na⁺ uptake inhibitor) added to the water had no effect on plasma NH₃ tensions (PNH₃), but increased MAmm slightly compared to control fish. In general, methazolamide resulted in an increase in the diffusing capacity of ammonia. The interpretation of these results was complicated by the fact that rapid serial blood sampling resulted in a universal blood alkalosis. The intact resting fish is unsuitable for studying the interaction between water boundary layer chemistry and excretion across the gill. With the blood-perfused trout head preparation it was demonstrated that MC0₂ and MAmm are linked through chemical reactions in the external water boundary layer adjacent to the gill. Pre-incubation of blood with acetazolamide reduced MC0₂ and MAMM in the blood-perfused head. Increasing the buffering capacity of inspired water, significantly reduced MAMM, but MC0₂ was unaffected. Each of these experimental treatments significantly reduced the acidification of ventilatory water flowing over the gills. It is proposed that the catalysed conversion of excreted C0₂ to form HCO₃₋ and H⁺ ions in the gill boundary layer provides a continual supply of H⁺ ions needed for the removal of NH₃ to NH₄₊, which reduces water NH₃ levels and facilitates ammonia excretion. Gas transfer variables in the blood-perfused head preparation were compared to intact cannulated fish with and without oral masks. Oxygen uptake (MO₂) and MCO₂ were lower, and MAMM, higher in the blood-perfused head compared to in, vivo values. these discrepancies were due to differences in venous O₂, CO₂, and ammonia levels, which determine mean gradients across the gills. It was concluded that the blood-perfused head is a suitable preparation for studying the interaction between MCO₂ and MAMM because the overall efficiency of transfer of NH₃ CO₂ was very similar between in. vitro and in vivo preparations, / Science, Faculty of / Zoology, Department of / Graduate

The mucus coat on the skin and gill of fishes serves a variety of protective functions including lubrication of the body surface, prevention of infection, and deterrence of parasites. Since mucus secretion in some teleosts appears to be controlled by the osmoregulatory hormones, prolactin and Cortisol, it was thought that the mucus coat may participate in teleost hydromineral balance. The primary objective of this study was to -examine the possible role of mucus in-osmoregulation of Leptocottus arma- tus Girard 1854 (Teleostei, Cottidae) and to relate these findings to the -endocrine control of mucus secretion. Whereas Leptocottus skin includes three types of secretory cells (eosinophilic granular, goblet, and cuticle-secreting cells) , the gill epithelium -has only goblet cells. Of ten cottid species examined histochemically, only seawater sculpins produce neutral mucins, while fresh water, seawater, and euryhaline species produce acidic mucins. Leptocottus primarily secretes a sialoglycoprotein, though sulphated mucins are present in gill goblet cells and the cuticle-secreting cells. The granular cells produce a tryptophan-rich basic protein. - Hypophysectomy or seawater adaptation reduce the number of gill goblet cells, compared to respective sham-operated or 5% seawater-acclimated controls. Ovine prolactin treatment of hypophysectomized fish prevented this decrease. In seawater-acclimated Leptocottus prolactin injections increase the number of gill mucus cells, while Cortisol injections of 5% "seawater-adapted fish had the opposite effect. The cuticle-secreting cells were most active in 5% seawater-adapted fish and this state was maintained by prolactin. A moderately active state was typical of seawater-adapted fish and this condition could be maintained by Cortisol or ovine growth hormone. The lowest activity of the cuticle-secreting cells occurred in hypophysectomized fish. Though prolactin and Cortisol appear to control the gill goblet cells and the cuticle-secreting cells, neither hy-pophysectomy nor treatment with prolactin or Cortisol significantly affected the skin goblet cells. The mucus coat appears incapable of reducing integumental permeability through steric interference of diffusion or through Donnan exclusion of ions from the mucus coat. Further, it is argued that enhancement of unstirred layers by mucus could not significantly affect hydromineral balance. Instead, alterations of the mucus coat with environmental salinity may be associated with the lubricating properties of mucus. Leptocottus mucus is a viscous non-newtonian fluid when concentrated but is an efficient lubricant when dilute. Seawater-adapted Leptocottus produce a more efficient lubricating mucus than do 5% seawater-acclimated fish; this effect appears to involve the cuticle-secreting cells. In an associated study I showed that the skin of the goby Gillichthys mirabilis participates actively in osmoregulation through extra-renal ion excretion. Thus the effects of prolactin and Cortisol may be primarily to control active transport in the skin. / Science, Faculty of / Zoology, Department of / Graduate

Electrophoretic patterns on polyacrylamide gels of blood serum proteins from 74 mountain whitefish (Prosopium williamsoni Girard) were examined for differences as they pertained to two geographically isolated populations, age, and sex. Serum samples were acquired from two supposedly isolated populations, the lower Provo River and the lower Weber River. Comparisons among gels were made on the basis of protein distribution as indicated by number of fractions and their density. Serum proteins showed marked intraspecific differences between the males as well as the females of each population. No variations were found which could be attributed to degree of maturity. Definite pattern differences were observed between the sexes of each population. Individual pattern variations within each group studied were observed.