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  • 1
    Electronic Resource
    Electronic Resource
    Respiratory adaptations of a fossorial mammal, the pocket gopher (Thomomys bottae) (1972)
    Springer
    Journal of comparative physiology 78 (1972), S. 121-137 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Fossorial rodent burrows exhibit relatively stable environmental conditions with regard to light, y. However, vastly different concentrations of CO2 and O2 are encountered in these burrows. Field observations of shallow pocket gopher burrows (Thomomys bottae) reveal CO2 concentrations to 3.8%, and O2 concentrations from 15.5% to 20.5% (Darden, 1970). Values similar to these have been reported for another genus of gopher,Geomys, by Kennerly (1964) and McNab (1966). 2. The sensitivity of the respiratory control mechanisms of the pocket gopher (T. bottae) O2 was tested and expressed as percent increase in minute volume as a function of the level of inspired CO2 (2% to 8%). The CO3 response curve is markedves for other terrestrial and diving mammals (Figs. 1 and 3). 3. Except for a reduction in slope, the respiratory response to CO2 of gophers can be described as similar to that recorded for humans. Carbon dioxide stimulates both increased ventilatory frequency and tidal volume in a near linear fashion. Individual difference in CO2 sensitivity among gophers was demonstrated (Table 2). 4. The level of alveolar CO2 (P A,CO2) in anesthetized pocket gophers is not significantly altered from values normally observed in man at sea level (Table 4). The reduced ventilatory response is due to a reduction in the slope of the response curve. The possible causes for the decreased sensitivity are discussed. 5. Comparisons of predicted and observed values of tidal volume (V T), rate of ventilation (f), minute volume ( $$\dot V_{\min } $$ ) and respiratory dead space (V D) were made (Table 3). Of these,V D and f and consequently $$\dot V_{\min } $$ were smaller than expected. The reduced value ofV D offsets the low $$\dot V_{\min } $$ and thus alveolar ventilation ( $$\dot V_A $$ ) is only slightly lower than expected. The possible biological significance of the alterations in f andV D are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00693609
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  • 2
    Electronic Resource
    Electronic Resource
    The sites of encephalic photoreception in photoperiodic induction of the growth of the testes in the White-crowned Sparrow, Zonotrichia leucophrys gambelii (1978)
    Springer
    Cell & tissue research 189 (1978), S. 441-467 
    Details
    ISSN: 1432-0878
    Keywords: Encephalic photoreceptors ; Hypothalamus ; Photoperiodism ; Birds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In bilaterally enucleated White-crowned Sparrows, Zonotrichia leucophrys gambelii, testicular growth and development at rates similar to those of intact birds subjected to long days, can be induced by illumination of sites within and near the ventromedial hypothalamus from the tips of single, chronically implanted, light-conducting fibers. Essentially identical results are obtained with the same mode of encephalic illumination of birds with intact eyes held on short days that are otherwise nonstimulatory. Examination of the distribution of the sites of the fibers from which weak illumination induced testicular growth, increase in plasma level of luteinizing hormone or increase in plasma level of testosterone suggests that most of the photoreceptors must lie either within the ventromedial hypothalamus or in sites ventral thereto, such as the tuberal complex. For the time being, at least, we find it necessary to assume that some photosensitive elements of the system occur outside of the ventral hypothalamus. We are most grateful to several colleagues at the University of Washington for their generous assistance. Dr. R.B. Pinter, Department of Electrical Engineering and Zoology; Dr. M.M. Harnois, Department of Physics, and Dr. R.J. Spiger, Geophysics Program, made suggestions and rendered invaluable assistance with various aspects of the optical measurements. Dr. John C. Wingfield and Mr. Philip W. Mattocks kindly assayed the plasma samples for luteinizing hormone and androgens. We wish to express our most sincere thanks to Dr. H.-G. Hartwig, Giessen, for his advice and to Miss I. Lyncker, Giessen, for her conscientious editorial aid and careful typing of the manuscript.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00209132
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    Paper (German National Licenses)
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