The effects of posture on blood pressure and heart rate in the three-toed sloth, Bradypus tridactylus

1. In unanesthetized, minimally restrained three-toed sloths, Bradypus tridactylus, the mean arterial pressure was 125/85 mmHg and the heart rate was 83.6 beats/min. There was no significant difference between these parameters whether the animal was erect or supine in the experimental chair. 2. Animals without any restraint had a mean blood pressure of 133/87 mmHg and a heart rate of 78.1 beats/min. There was no significant difference between these parameters whether the animal was seated or suspended from a horizontal bar and there was no significant difference between the minimally restrained and the unrestrained animals. 3. Tilting from the erect to the supine position produced large increases in blood pressure parameters, 37% in systolic and 21% in diastolic, reaching the maximum effect in a mean time of 38 sec. Tilting from the supine to the erect position caused even greater increases in pressure, 43% and 38% respectively, and reaching the maximum also in a mean time of 38 sec. 4. Tilting initially increased the heart rate, in going from erect to supine by 21% in 16 sec and from supine to erect by 23% in 20 sec. 5. In going from erect to supine there was a reflex bradycardia later, 15% below control level with a maximum at 40 sec, and to a lesser degree in going from supine to erect, 9% with maximum at 50 sec.     

Cormack–Jolly–Seber model with environmental covariates: A P‐spline approach

In capture–recapture models, survival and capture probabilities can be modelled as functions of time‐varying covariates, such as temperature or rainfall. The Cormack–Jolly–Seber (CJS) model allows for flexible modelling of these covariates; however, the functional relationship may not be linear. We extend the CJS model by semi‐parametrically modelling capture and survival probabilities using a frequentist approach via P‐splines techniques. We investigate the performance of the estimators by conducting simulation studies. We also apply and compare these models with known semi‐parametric Bayesian approaches on simulated and real data sets.     

The effects of posture changes on blood pressure and heart rate of anesthetized and reserpinized sloths

1. Tilting sloths anesthetized with chloralose from erect to supine or supine to erect produced little or no effect on heart rate. 2. Tilting anesthetized sloths from erect to supine increased both systolic and diastolic pressures significantly and by about the same amounts. The maximum effect was produced in 20 sec. 3. Pressures stabilized at a higher level than in the erect posture but below the maximum reached in tilting. 4. Tilting these sloths from the supine to the erect posture resulted in a rapid (20 sec) and dramatic fall in pressures to below the initial erect pressure levels. Return to initial erect levels took place slowly. 5. Tilting reserpinized sloths from erect to supine or supine to erect produced little or no effect on heart rate. 6. Tilting reserpinized sloths from erect to supine increased both systolic and diastolic pressures materially and by similar amounts. The maximum effect took 50 sec. 7. Pressures stabilized at higher levels than in the erect posture but less than maximum reached with tilting. 8. Tilting these sloths from supine to erect caused significant falls in pressure to slightly below the initial erect pressure, with maximum effect reached in 30 sec and eventual return to control level. 9. Pressure changes were almost entirely the result of altered venous return. 10. Neither chloralose nor reserpine completely blocked vascular control but reduced it materially.