Award Date

1-1-1996

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Science

Number of Pages

217

Abstract

The formation of the cardiovascular system and its role in gas exchange has long been speculated to occur concomitantly. Although this premise has been suggested and quoted for more than a century, there are few studies to date which have attempted to validate these claims. Furthermore, the few which do exist have been primarily concerned with two things: first, how environment may affect the functional morphology; and second, how these changes may affect hemodynamics directly. As a result, our understanding of how gas exchange is coupled with to cardiovascular function is seriously lacking; The goal of this dissertation was to understand how, or if, the cardiovascular and respiratory systems coordinate function during development. Populations of amphibians were reared in various environments which included carbon monoxide (CO). This allowed for direct assessment of the efficacy of Hb in bulk O{dollar}\sb2{dollar} transport. The results indicated that CO, and the subsequent elimination of Hb function, had few ill effects on either aerobic or anaerobic metabolism. Further, the data indicated that cardiovascular function was mildly elevated. A separate study, set out to determine what factors limit overall O{dollar}\sb2{dollar} transport in developing embryos by limiting the available quantities of gas and eliminating Hb function. The results indicated that aerobic metabolism was unaffected in all populations. Cardiovascular function was mildly elevated, but only in populations of animals exposed to CO. Finally, gas exchange was modeled in developing embryos to determine the role of diffusion and plasma transport in overall O{dollar}\sb2{dollar} uptake. Calculations of maximal O{dollar}\sb2{dollar} flux indicate that diffusion would allow for enough gas to be exchanged to support aerobic metabolism in early life. Moreover, the role of plasma transport was considered in addition to diffusion, it be came clear that their combined transport would be adequate to support metabolism for animals in late life; A separate study evaluated how body composition changes with progressive development. From this it was determined that amphibians are unlike their fish counterparts in composition. When the total energy pool available for growth and development was calculated and compared with aerobic metabolism, it was shown that energy was not a limiting resource during development; Collectively these data indicated that Hb was not essential of O{dollar}\sb2{dollar} uptake and that the cardiovascular system as a whole may play a reduced role in total O{dollar}\sb2{dollar} turnover. Furthermore, the data indicates that neither diffusion nor perfusion limits total gas exchange. In addition, the model indicate that diffusion may be a viable mean to obtain O{dollar}\sb2{dollar} early in development, and that late in development convection of plasma coupled with diffusion could support metabolism. Finally, the body composition work indicate that resource limitations were not set by available substrate.

Keywords

Body; Body Composition; Cardio; Cardiorespiratory; Composition; Exchange; Gas; Gas Exchange; Metabolism; Ontogeny; Respiratory; Support

Controlled Subject

Physiology

File Format

pdf

File Size

4106.24 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

Permissions

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Identifier

https://doi.org/10.25669/5eem-z4yi


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