Biomedical subjects

J Stinner

Publications and source records attributed to J Stinner.

3 recordsLinked to original sources

PubMed1998

A protein titration hypothesis for the temperature-dependence of tissue CO2 content in reptiles and amphibians.

Whole-body CO2 stores are known to increase with cooling in reptiles and amphibians (-[CO2]/T ). The aim of this study was to determine the mechanism(s) producing this inverse relationship. The [CO2]/T coefficients were determined for eight reptilian and one amphibian species and were found to differ by a factor of approximately 10, from -0.21 mmol kg-1 °C-1 in the Mediterranean spur-thighed tortoise Testudo graeca to -0.02 mmol kg-1 °C-1 in the bullfrog Rana catesbeiana. The [CO2]/T coefficients were correlated with values in the literature for in vivo plasma pH/T coefficients ([CO2]/T=-0.188.24pH/T; r2=0.87). Plasma electrolyte concentrations (Na+, K+, Ca2+, Mg2+, Cl-, inorganic phosphate, SO42- and lactate), [protein], [CO2], PCO2 and pH were measured in chronically cannulated resting black racer snakes Coluber constrictor. When the temperature was reduced from 30 to 10 °C, pH increased slightly (by -0.0028 pH units °C-1), PCO2 decreased by 7 mmHg, [CO2] increased by 3.2 mmol l-1 and [HPO42-+H2PO4-] increased by 0.7 mmol l-1. Concentrations of protein and of the remaining electrolytes were not significantly different (P>0.05) at 30 and 10 °C. Net plasma protein charge, calculated from the principle of electroneutrality (the sum of the cations in mequiv = the sum of anions in mequiv), was -0.48 mequiv g-1 protein at 30 °C and -0.38 mequiv g-1 protein at 10 °C. This 21 % decrease was attributed to the increases in [CO2] (i.e. carbonic acid) and inorganic phosphate concentration. Between 30 and 10 °C, skeletal muscle pH and [CO2] in C. constrictor increased (by -0.009 units °C-1 and -0.125 mmol kg-1 °C-1, respectively), [Na+] and [Cl-] each decreased by approximately 12 mequiv l-1, and [K+] and the percentage of water did not change significantly. It is concluded that the increase in whole-body CO2 stores with cooling in reptiles and amphibians results from the passive effects of temperature changes upon the ionization constants of proteins and the active adjustment of PCO2 (ventilatory regulation), so that -pK is greater than -pH. Active transmembrane ion-exchange processes do not appear to be involved.

Journal Article↗

PubMed1996

Ventilatory and blood acid-base adjustments to a decrease in body temperature from 30 to 10YC in black racer snakes Coluber constrictor

There is increasing evidence that many amphibian and reptilian species use relatively slow ion-exchange mechanisms in addition to ventilation to adjust pH as body temperature changes. Large changes in blood bicarbonate concentration with changes in temperature have previously been reported for the snake Coluber constrictor. The purpose of the present study was to determine the ventilatory and pH adjustments associated with the increase in CO2 stores when the snakes are cooled. Body temperature was lowered from 30 to 10 °C within 4 h, at which time measurements of inspired minute ventilation (V.air), O2 consumption (VO2) and CO2 production (V.CO2) were started and continued for 56 h. The decrease in temperature produced a transient fall in the respiratory exchange ratio (V.CO2/VO2) to 0.2-0.3 and a steady-state value of 0.65±0.14 (mean ± s.d., N=7) was not achieved until about 35 h. There were concomitant transient reductions in V.air and V.air/V.O2. However, V.air/V.CO2 initially increased, with a corresponding reduction in arterial PCO2 (PaCO2) and increase in arterial pH. By 35 h, V.air/V.CO2 had decreased and PaCO2 had increased to steady-state levels, but pH decreased very little because of a gradual increase in bicarbonate concentration. We conclude that the drop in temperature imposed a metabolic acidosis for approximately 35 h because of the time required to increase bicarbonate concentration, and that the acidosis was compensated for by an elevated V.air/V.CO2. Steady-state breathing and acid-base status were not achieved until the relatively slow increase in CO2 stores had been completed.

Journal Article↗

PubMed1995

Sympathetic nervous system influences salt appetite in four strains of rats.

Sodium appetite and preference were examined in four rat strains using a social stressor and drugs to block sympathetic nervous system (SNS) activity. We have studied these strains for over 14 yr in our laboratory and the SHR strain has increased blood pressure and increased sympathetic nerve activity. The F1 crosses produce male offspring with the Y chromosome from a hypertensive or normotensive father, to examine its influence on sodium appetite. The pharmacological manipulation produces blockage of the SNS which may be partially responsible for stress induced sodium appetite. The objectives were to determine: (i) if the SNS was necessary for stress induced increased salt appetite; and (ii) if the Y chromosome from a hypertensive father increased salt intake or preference. Four strains (n = 6-8/group) of male rats were studied from 3-6 mo of age: normotensive Wistar-Kyoto (WKY) rats, spontaneously hypertensive rats (SHR) and hybrid crosses between a WKY mother and SHR father (WS) and the reciprocal cross (SW). Each group consumed Purina rat chow (0.3% Na) and was given a four-bottle choice of salt water ad lib (0.0%, 0.5%, 1.0%, and 1.5% NaCl). Social stress produced by intruder males significantly increased salt intake in all groups. SHR had higher salt intake than WKY both before and after exposure to intruder stress. In general, the SHR group preferred twice the concentration of saline (1.0%) as did the WKY (0.5%). Clonidine and reserpine both reduce SNS activity and consequently reduced salt intake after stress, from 20-44% depending on the genetic background of the rat strain.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗