The American journal of physiology
-
This study examined the relative roles of the right vs. left vagi in mediating the inhibitory influence of vagal sensory input on sympathetic outflow to the cardiovascular system. This objective was pursued through examination of responses to 1) interruption of tonic vagal input and 2) intracoronary administration of veratridine (Bezold-Jarisch effect). Bilateral vagal cold block (BVB) (n = 16) increased arterial pressure 25 +/- 3 mmHg and heart rate 66 +/- 7 beat/min, whereas right vagal cold block (RVB) and left vagal cold block (LVB) increased arterial pressure 13 +/- 2 and 4 +/- 2 mmHg, respectively. ⋯ During RVB the depressor effect of veratridine was reduced to -18 +/- 5 mmHg, and changes in heart rate or LV (dP/dt)max were abolished. Veratridine administration during LVB decreased arterial pressure (-39 +/- 6 mmHg), heart rate (-22 +/- 6 beat/min), and LV (dP/dt)max (-250 +/- 60 mmHg). We conclude that in the conscious dog the tonic inhibitory influence of vagal afferent nerves on vasomotor outflow is predominantly associated with the right vagus as in Bezold-Jarisch effect.
-
In vivo microperfusion studies of the proximal convoluted tubule of the rat were performed to determine the effect of metabolic acidosis on total CO2 (tCO2) absorption. In series I, tubular perfusion was performed in control and acidotic rats in a manner by which similar mean total CO2 concentrations in the proximal tubule were maintained. Comparable ranges of perfusion rate were studied in both groups. ⋯ Again, JtCO2 was higher in the acidotic rats, 352 +/- 19 vs. 198 +/- 13. The results indicate that at comparable luminal tCO2 concentration and tubular fluid flow rates, tCO2 absorption is significantly increased in the acidotic state. Although other mechanisms cannot be excluded, the finding of an increase in proximal tCO2 absorption in the acidotic rats is in agreement with the presence of an accelerated Na+/H+ exchange rate in brush border membrane vesicles obtained from the renal cortex of animals with metabolic acidosis.
-
Multiple linear regression, in which several predictor variables are related to a response variable, is a powerful statistical tool for gaining quantitative insight into complex in vivo physiological systems. For these insights to be correct, all predictor variables must be uncorrelated. However, in many physiological experiments the predictor variables cannot be precisely controlled and thus change in parallel (i.e., they are highly correlated). ⋯ Although multicollinearity can be avoided with good experimental design, not all interesting physiological questions can be studied without encountering multicollinearity. In these cases various ad hoc procedures have been proposed to mitigate multicollinearity. Although many of these procedures are controversial, they can be helpful in applying multiple linear regression to some physiological problems.
-
We tested the hypothesis that monocrotaline would activate arachidonic acid metabolism in rats. If activation occurred before the pulmonary hypertension developed, arachidonate metabolites could play a role in the hypertensive monocrotaline injury. We found that 1 wk after monocrotaline administration 6-ketoprostaglandin F1 alpha and leukotriene C4 were increased in lung lavages. ⋯ Indomethacin administration inhibited the formation of cyclooxygenase metabolites but did not prevent pulmonary hypertension. Diethylcarbamazine administration reduced the numbers and activity of inflammatory cells, increased pulmonary hypertension, prevented right ventricular hypertrophy, and inhibited the formation of slow-reacting substances. We concluded that arachidonate metabolism was activated before pulmonary hypertension developed, that the inflammatory cells in the alveolus accompanied the hypertensive process, and that diethylcarbamazine attenuated both the monocrotaline-induced inflammatory response and the pulmonary hypertension.
-
The metabolism and performance of a perfused rat hindquarter preparation was examined during heavy exercise in three conditions: control (C), metabolic acidosis (MA, decreased bicarbonate concentration), and respiratory acidosis (RA, increased CO2 tension). A one-pass system was used to perfuse the hindquarters for 30 min at rest and 20 min during tetanic stimulation via the sciatic nerve. The isometric tension generated by the gastrocnemius-plantaris-soleus muscle group was recorded, and biopsies were taken pre- and postperfusion. ⋯ Muscle creatine phosphate utilization and ATP levels were unaffected by acidosis. Acidosis decreased the muscle's ability to generate isometric tension and depressed both aerobic and anaerobic metabolism. During stimulation in this model lactate left the muscle mainly as a function of the production rate, although a low plasma bicarbonate concentration at pH 7.15 depressed muscle lactate release.