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At least 1,171 records · Page 65Linked to original sources
PubMed1992

Metabolic responses to forced dives in Pekin duck measured by indirect calorimetry and 31P-MRS.

We tested the hypothesis that forced-dived ducks experience a reduction in metabolic rate during prolonged submergence. Unidirectionally ventilated conscious ducks were subjected to forced dives by temporarily stopping the airflow in the ventilation system and simultaneously filling a face mask with cold water. A typical cardiovascular response to submergence was observed: bradycardia and maintained arterial blood pressure. Phosphorylated metabolite concentrations in the pectoral muscle were measured noninvasively by phosphorus magnetic resonance spectroscopy (31P-MRS). ATP content was constant, and phosphocreatine was depleted via the creatine kinase reaction at a rate similar to the resting rate of ATP turnover, which was estimated to be 0.9 mumol.min-1 x g-1 in resting perfused pectoral muscle of pentobarbital-anesthetized ducks. Oxygen from myoglobin supplied at most 12% of the ATP required by the resting muscle during dives. Whole animal postdive excess oxygen consumption and blood lactic acid accumulation suggested that the shortfall in aerobic metabolism during forced dives was compensated by an increase in anaerobic metabolism.

Adenosine Triphosphate↗
PubMed1976

Analytical refinements in animal calorimetry.

An analysis is presented of a system for indirect calorimetric measurement. Emphasis has been placed upon problems associated with the use of large climate-controlled chambers. The dynamics of gas exchange and the influence of ambient conditions on various parameters have been subjected to physical analysis which has led to the following conclusions: 1) Fast-response measurement of heat production can be achieved even if the size and hence washout time of the chamber is large. 2) Accurate continuous measurement of heat production over long periods, without correction for changes in barometric pressure, is possible if suitable instrumentation is chosen. 3) A method for calibration of a paramagnetic oxygen analyzer achieved high accuracy at low cost. 4) The entire system has been checked by simulation of gas exchange in the chamber, by injection of nitrogen at a known rate.

Animals↗
PubMed1983

Calorimetry with heat flux transducers: comparison with a suit calorimeter.

Regional and total body heat loss rates of human subjects at rest were measured simultaneously by means of an array of heat flux transducers and with a tube suit calorimeter. Conditions ranged from thermal comfort to strong cooling. A high degree of correlation was found between heat loss rates determined by the two independent techniques. For the head and arms, the transducer array system measured less heat loss than the suit. For the torso and legs, measurements by the two methods were equivalent. For the whole body, the transducer system yielded a heat loss rate 87% of the suit calorimeter value.

Adult↗
PubMed1984

Calibration methods in respiratory calorimetry.

Methods for calibration of respiratory gas exchange measurement systems are evaluated. A new method is described in which O2 is removed from the subject chamber or gas stream and measured gravimetrically in a small combustion chamber containing steel wool. The "Fe-burner" method was tested by comparison with the N2-injection method and found to be of similar accuracy. The new method is easy to perform, quick, and readily applicable to both open- and closed-circuit respiratory systems. It has a rate of O2 uptake that can be adjusted to be similar to the rate by an experimental subject (10-600 kg). Complete calibration of open- and closed-circuit indirect calorimetric systems can be achieved when the Fe-burner method, involving measurement of O2 uptake, is combined with the gravimetric injection of specific gases (CO2, methane) produced by the subject.

Calibration↗