The American journal of physiology
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At ambient temperature (Ta) 20 and 10 degrees C, metabolic heat production and hypothalamic temperature (Thypo) were measured to determine the fever response in six rabbits injected with polyriboinosinic-polyribocytidylic acid (poly I:C; 5 mg/kg iv). Similar measurements were made in afebrile and febrile animals subjected to 3 h of body cooling, in which heat was extracted with a chronically implanted intravascular heat exchanger in a ramplike manner. ⋯ The net effect at the end of the cooling period was that Thypo decreased by 0.4 and 0.6 degree C more than in the afebrile cooling experiments at Ta 20 and 10 degrees C, respectively. The results indicate normal shivering responses during phase I of poly I:C-induced fever and depressed shivering in phase I, possibly because of a reduced thermosensitivity.
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Comparative Study
Fallacy of indexing renal and systemic hemodynamic measurements for body surface area.
Renal plasma flow, glomerular filtration rate, and cardiac output are traditionally indexed for body surface area by expressing these traits as per-surface-area ratios. Indexing is intended to remove interindividual variation attributable to differences in body size. Regression is an alternative method commonly used to adjust other biological traits for the effects of a covariate, such as body surface area. ⋯ Moreover, indexing obscured differences in mean renal plasma flow between females and males and created differences in mean cardiac output between the genders. In contrast, the regression method consistently eliminated dependencies of each trait on body surface area and did not lead to inappropriate inferences about mean differences in these traits between females and males. We conclude that the indexing method of adjusting renal plasma flow, glomerular filtration rate, and cardiac output for interindividual differences in body surface area should be abandoned and replaced by use of the regression method.
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Comparative Study
Influence of normal aging on oral-pharyngeal and upper esophageal sphincter function during swallowing.
The influence of aging on oral-pharyngeal swallowing was assessed by simultaneous manometry and videoradiography in 14 nondysphagic elderly individuals (mean age 76 yr) and 11 healthy, young controls (mean age 21 yr). Sphincter opening was diminished significantly in the elderly (P = 0.0001), but trans-sphincteric bolus flow rates were preserved. The increased impedance to trans-sphincteric bolus flow from reduced sphincter opening in the aged was reflected in a significant increase in hypopharyngeal intrabolus pressure (P = 0.003). ⋯ Coordination of UES relaxation and opening with midpharyngeal contraction was not significantly affected by age. Deglutitive hyolaryngeal motion was not affected by age but was delayed by a duration equivalent to the prolongation in oral transit. We conclude that normal aging prolongs the oral-pharyngeal swallow that impairs UES opening but does not influence pharyngo-sphincteric coordination.
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Many infants who require cardiac surgery have cyanotic heart disease. We assessed the relative tolerances to ischemia of hearts from immature normoxemic rabbits versus hearts from immature rabbits subjected to hypoxemia since birth. Normoxemic animals were raised from birth in an environment where the inspired fractional concentration of oxygen (FIO2) was 0.21; for the hypoxemic studies FIO2 was reduced to 0.09. ⋯ For hearts protected with hypothermia alone, recovery of aortic flow was better in hearts hypoxemic from birth compared with normoxemic controls at 7-12 days (78 +/- 7 vs. 60 +/- 6%, P < 0.05) and 21-28 days old (81 +/- 12 vs. 26 +/- 28%, P < 0.05). Protection with hypothermia plus cardioplegia was also better in hearts hypoxemic from birth compared with normoxemic controls at 7-12 days (74 +/- 8 vs. 63 +/- 10%, P < 0.05) and 21-28 days old (84 +/- 3 vs. 71 +/- 5%, P < 0.05). Protection with hypothermia alone and hypothermia plus cardioplegia was no different within chronically hypoxemic age groups.(ABSTRACT TRUNCATED AT 250 WORDS)
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The plasma fluxes of ornithine (Orn), arginine (Arg), and citrulline (Cit) and rate of conversion of labeled ornithine-to-citrulline (QOrn-->Cit) were estimated in six healthy adult men receiving an arginine-rich or arginine-free L-amino acid-based diet, each for 6 days. On day 7 an 8-h (3-h fast, 5-h fed) primed continuous intravenous infusion of L-[guanido-15N,15N] arginine, L-[ureido-13C]citrulline, L-[5,5,2H2]ornithine, and L-[5,5,5-2H3]leucine was conducted. Mean citrulline fluxes (mumol.kg-1.h-1) were 10.4-13.6 for the various conditions and/or diets and remained unchanged (P > 0.05). ⋯ Rates of QOrn-->Cit declined by 30% (P < .05) during the fed arginine-free period. Short-term restriction in the dietary supply of arginine did not alter the rate of whole body nitric oxide synthesis. One subject showed a very high output of nitrate on arginine-free diet (6 times average for remaining subjects).