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Biomedical subjects

J Piiper

Publications and source records attributed to J Piiper.

At least 127 records · Page 7Linked to original sources
PubMed1979

Anaerobic energy metabolism during severe hypoxia in the lungless salamander Desmognathus fuscus (Plethodontidae).

In the lungless salamander Desmognathus fuscus, mean body weight 4.5 g, the changes in total body concentration of adenosine triphosphate (ATP), creatine phosphate (CP) and lactate (LA) were measured during exposure to a severely hypoxic atmosphere (PO2 = 25 Torr) for 48 h at 13 degrees C. ATP and CP decreased, reaching a minimum at 3 h of exposure, and LA increased, attaining maximum values after 12 to 24 h of hypoxia. Thereafter recovery was observed and control values of ATP, CP and LA were reached after 48 h of sustained hypoxia. This behavior is attributed to a biochemical adjustment to hypoxia of the metabolic machinery which leads to normalization of chemical energy stores in spite of O2 uptake being persistently reduced to 30% of its normoxic level. The anaerobic energy yield derived from splitting of ATP and CP and from LA formation corresponded to about 2/3 of the oxidative energy deficit during the first 3 h of hypoxia. Thereafter anaerobic mechanisms were responsible for insignificant contributions to the energy balance.

Adenosine Triphosphate↗
PubMed1979

Arterial-expired PCO2 differences in the dog during acute hypercapnia.

A recent report (J. Appl. Physiol. 38: 382-388, 1975) suggests that negative blood-gas CO2 partial pressure (PCO2) differences exist in the dog during hypercapnia, as mean expired PCO2 exceeded arterial PCO2 by more than 10 Torr when the CO2 fraction in inspired gas (FICO2) was 0.1. We have reinvestigated this problem in anesthetized dogs breathing spontaneously room air or hypercapnic mixtures (FICO2 = 0.05 or 0.10). During steady state, arterial blood samples were analyzed with electrodes, care being taken to keep the electrode temperature within +/- 0.2 degrees C at the actual aortic temperature of the animal. Respired gas was measured at the tracheostomy by a sensitive low-noise respiratory mass spectrometer. During room air breathing, the arterial-end-expired PCO2 difference, P(a-E')CO2, averaged +5 Torr and decreased to +0.9 Torr and to +0.1 Torr with FICO2 = 0.05 and 0.1, respectively. Hypoxia (FIO2 = 0.10) had no apparent effect on the P(a-E')CO2 difference. We ascribe the decrease in P(a-E')CO2 with hypercapnia to the diminishing effects of alveolar dead space, whereby end expired PCO2 approached arterial PCO2. We then conclude that in blood-gas equilibration lungs, PCO2 in end-capillary blood comes close to alveolar PCO2, and that the negative blood-gas PCO2 differences reported earlier are probably caused by deficiencies in the techniques used.

Animals↗
PubMed1979

Series ventilation, diffusion in airways, and stratified inhomogeneity.

Functional inhomogeneity in lungs, meaning local variance of PCO2 and PO2 in alveolar space, may be of parallel and/or series nature. The effects of both kinds of inhomogeneity are qualitatively similar (decrease of the efficiency of alveolar gas exchange) and difficult to differentiate by experimental analysis. As far as diffusive mixing is concerned, methods specifically suited for detection and quantification of stratified inhomogeneities are based on separation of multiple test gases of differing diffusivity. The results of studies by such methods indicate that for alveolar O2 exchange the resistance attributable to stratification is in most cases less than the reciprocal pulmonary diffusing capacity for O2. In the conventional analysis of alveolar gas exchange, effects of stratification would contribute to alveolar dead space ventilation or would be incorporated in the pulmonary diffusing capacity.

Animals↗
PubMed1978

Energetics of anaerobic glycolysis in dog gastrocnemius.

Thermally isolated gastrocnemii were stimulated to exhaustion, by rhythmic isotonic (70 N) tetanic contractions, during complete occlusion of blood flow. Enthalpy change (h = work + heat) and work output (w) (kJ/kg) were obtained from records of deep muscle temperature and shortening. The lactate produced (LA, mol/kg) was measured in the outflow after reestablishement of blood flow. The following relationships were obtained: h = 76LA + 1.2, and w = 19.8LA + 0.30. As the energy liberated at exhaustion by alactic energy sources (approximately P and O2 stores) is constant, deltah/deltaLA = 76 (+/- 10.5; S.E.) kJ/mol is the enthalpy change for lactate formation (delta HLA). The neutralization heat was estimated on muscle homogenates at 12kJ/mol, leaving approximately 64 kJ/MOL for deltaH of LA formation proper. The mechanical efficiencies of work related to LA formation (ELA) and of that not related to LA formation (EnonLA) were practically identical (0.25). From these values and from deltaHLA, the enthalpy change of approximately P splitting was estimated in the range of 52--62kJ/mol, depending on the value of the ratio delta approximately P/deltaLA assumed in the calculation.

Adenosine Triphosphate↗
PubMed1978

Determination of binary diffusion coefficients of various gas species used in respiratory physiology.

In order to provide data required for quantitative analysis of gas diffusion in lung airways, diffusion of He, CO, O2, CO2 and SF6 in various gases used in respiratory physiology was studied in vitro at 37 degrees C and 25 degrees C. The gases were allowed to mix by diffusion in a closed cylindrical tube (length 2 m, internal diameter 1 cm), one half of which was initially filled with 1% test gas in a second gas and the other half of which was filled with the second gas only. Kinetics of diffusional equilibration was determined by withdrawal of spot samples analyzed by gas chromatography. The binary (mutual) diffusion coefficients (D) computed there from were in most cases in good agreement with values calculated on the basis of the Chapman-Enskog theory.

Diffusion↗
PubMed1977

Respiration and circulation during swimming activity in the dogfish Scyliorhinus stellaris.

A number of respiratory and circulatory parameters was measured in the Larger Spotted Dogfish Scyliorhinus stellaris before, during and after periods of spontaneous swimming. During swimming the gill ventilation was increased, mainly due to increased ventilatory stroke volume, the respiratory frequency showing a small rise only, and the cardiac output was increased at only slightly elevated cardiac frequency. Coordination between cardiac, ventilatory or locomotor (tail-beat) rhythms was not observed. The decrease in utilization of inspired water O2 during swimming was attributable to diffusion limitation in branchial O2 transfer. A considerable fraction of the total net amount of O2 required for swimming was taken up during the recovery phase. From the observations that (1) the decrease in gill ventilatory flow after cessation of swimming revealed a very rapid component (followed by a slow component), and that (2) changes in swimming speed were reflected by immediate changes in momentary ventilatory flow, it is concluded that the increased ventilation during swimming was in part mechanical-passive and/or due to nervous coupling between respiratory and locomotor centers.

Animals↗
PubMed1977

Penetration of inhaled He and SF6 into alveolar space at low tidal volumes.

To study mixing of inspired gas with lung gas, penetration of simultaneously inspired helium (He) and sulfur hexafluoride (SF6) into alveolar space was determined in normal subjects at low tidal volumes (from 50 to 500 ml) and at varied lung volumes and speeds of inspiration/expiration. The volume of inspired gas reaching the alveolar space, termed alveolar-tidal volume, VTA, was calculated from preinspiratory lung volume, inspired volume, and inspired and expired alveolar test gas concentrations. The difference between the VTA values calculated for He and SF6, VTA(He) - VTA(SF6), was influenced by tidal volume, lung volume, and the speed of inspiration/expiration, but it was always positive. The results are qualitatively explainable on the basis of easier diffusive mixing of He in lung airways compared with SF6. Since Taylor dispersion would produce deeper penetration, and therefore higher VTA, for a less diffusible gas the results provide no evidence for its implication in pulmonary gas exchange.

Adult↗
PubMed1976

Problems in determination of oxygen dissociation of avian blood.

No appreciable errors are expected in determination of blood gas values and pH using classical techniques provided time of anaerobic storage is kept small and is, if unavoidable performed on ice. In particular, dissociation curves may safely be analyzed with the Van Slyke technique which is in disagreement with the conclusions of Lutz et al. (1973). For measurement of PO2 and PCO2, delay time is mainly dictated by response time of the electrodes; measurements may have to be corrected for metabolism, particularly in high PO2 range.

Animals↗
PubMed1976

Measurement of diffusivity and metabolic rate of O2 and CO2 in respiring tissue.

The method described is apt to measure, at the same time, Krogh's diffusion constant and specific metabolic rates for O2 and CO2 in intact, respiring tissues. Due to metabolism tissue thickness for this method is limited to about 500 mum unless hyperbaric conditions are used. The results suggest that both KO2 and KCO2 are similar in alive and in dead tissue. Due to tissue inhomogeneity and to possible facilitation of O2 or CO2 transport our values of K have to be considered as effective mean values for the physiological range of PO2 and PCO2 in muscle at rest and at exercise.

Animals↗
PubMed1976

Pulmonary gas exchange in dogs ventilated with mixtures of oxygen with various inert gases.

To study the influence of physical properties of the respired gas on alveolar gas exchange, alveolar-arterial partial pressure differences for O2 and CO2 were measured in anesthetized dogs that were artificially ventilated with gas mixtures of O2 in N2, He, Ar or SF6. In both hyposia and normoxia alveolar-arterial PO2 differences had the tendency to increase slightly in the sequence of the respired inert gases SF6 less than Ar less than N2 less than He, while arterial-alveolar PCO2 differences remained practically unchanged. Pulmonary diffusing capacity for CO(DCO), determined by the single breath technique, revealed no significant differences between the four gas mixtures used. The possible mechanisms underlying these results are discussed in connection with the physical properties of the respired gas mixtures.

Animals↗