ALBERT

Notes: Summary 1. Blood circulation to the leg of an antarctic bird, the giant fulmar,Macronectes giganteus, has been studied in response to changing the temperature of the ambient environment including immersion of the feet in ice water. 2. Measurements done include blood flow to the leg by an electromagnetic flow meter, blood pressure in the carotid artery and locally in a leg artery and vein, intravenous and arterial blood temperatures in the leg in addition to foot subcutaneous temperature and core temperature (deep pectoral temperature). 3. Blood flow to the lower leg varied between 10 ml/min and 40 ml/min during resting thermoneutral conditions. 4. Raising the core temperature by heating the central body increased foot blood flow to maximum values around 40 ml/min or 160 ml/min/100 g tissue. 5. Quick warming of the cold feet by immersion in hot water caused only slight increase in leg blood flow, whereas slow rewarming in air gave increasing leg blood flow when the local temperature of the foot increased from near zero to 35.6° C. 6. Sudden immersion of the foot in ice water (T = −2.0° C) elicited an immediate flow increase and a transient increase in foot arterial blood temperature. Venous pressure in the foot increased with blood flow while foot arterial pressure was unaltered. 7. The vasodilatation on ice immersion, termed the “cold flush” was followed by a gradual increase in vasoconstriction and reduced blood flow. After about 3 minutes fluctuations “huntings” appeared in leg blood flow and local temperatures in the foot. 8. The described circulatory changes are discussed in relation to thermal homeostasis of the bird and protection of the naked feet from cold shock and impairment of function on sudden cold exposure. Special reference is given to the phenomenon of cold vasodilatation earlier described on cold exposure of extremeties in mammals.

Notes: Summary The objectives of this study included directin vivo measurements of circulating blood gases, pH, heart rate, and blood pressure during voluntary dives of unrestrained Nile monitor lizards. A Radiometer flow-through cuvette was employed for continuous recording of arterial PO2, PCO2 and pH. Hematological properties revealed no particular adaptations for diving. Mean values were: hematocrit = 24%; hemoglobin concentration = 7.1 g %; oxygen capacity = 9.3 vol %; red cell dimensions = 22×12 μ; red cell count = 0.67 million/μl. The respiratory properties of the blood, studiedin vitro andin vivo, show distinct adaptations to habitual diving. Oxygen affinity of blood is low (P50 = 42.4 mm Hg at pH 7.45, 25 °) and the dissociation curve is markedly sigmoid (n = 3.1). These features, coupled with a Bohr factor (Δ logP 50/ΔpH) of −0.48, ensure increased utilization of oxygen while maintaining relatively high tissue PO2. Arterial pH decreases during diving from about 7.5 to 7.1 due to combined respiratory and metabolic acidosis. High plasma bicarbonate (30 mM/l at PCO2 = 25 mm Hg) and a buffering capacity of ΔH C3 −O/Δ pH = 18.9 mM/l increase the tolerance to this acidosis and prolong diving time. Thein vivo oxygen dissociation curve shows a 90 % depletion of arterial oxygen content during typical dives. Diving elicited a rapidly developing bradycardia with maximum of 85 % reduction in heart rate. The temperature sensitivity of HbO2 binding was very low (ΔH = −3kcal). This would minimize the HbO2 affinity increase accompanying the decrease in body temperature likely to occur in lizards going from sun basking to submergence in water.

Notes: Summary Cutaneous aquatic gas exchange and pulmonary gas exchange have been compared in an aquatic snakeAchrochordus javanicus and the terrestrial snakeConstrictor constrictor. Gas exchange was measured by closed respirometry with the snakes in air and in water with access to air. Frequency of air breathing, tidal volumes and total lung volumes were also compared in the two species. All measurements were done at 20–22 ° C. The aquaticAchrochordus showed long periods of apnea in submerged condition interrupted by short periods of breathing activity at the surface. Average frequency of air breathing activity was 2.6 times per hour. Breathing in constrictor was more frequent but irregular with an average frequency of 143 breaths per hour. Total lung volume was 66±31 ml/kg body weight and 72.5±59 ml/kg body weight inAchrochordus andConstrictor, respectively. Tidal volumes were 41.5±4.4 ml/kg body weight and 29.5±14.8 ml/kg body weight, largest inAchrochordus. Constrictor had the highest total O2 uptake ( $$\dot VO_2 $$ ) correlating with a higher activity. Total gas exchange ratio (R E ) was 0.69 forConstrictor and 0.77 forAchrochordus. InConstrictor air breathing accounted for 97% of the total $$\dot VO_2 $$ whereas 21% of the CO2 exchange was aquatic. Corresponding figures forAchrochordus were 92% of total $$\dot VO_2 $$ by air breathing with as much as 33% of the CO2 elimination as aquatic gas exchange. The results demonstrate that the trend among early air breathing vertebrates (fishes and amphibians) of a conservative evolution of CO2 elimination by air breathing also extends to snakes. Significantly the cutaneous exchange component was highest in the more aquatic species. The results are discussed in relation to recent reports of a higher than alleged role of the skin of reptiles in evaporative water loss.

Notes: The mechanisms by which peripheral circulation and respiration serve in maintaining thermal homeostasis in birds living in cold climates are reviewed. Three types of arteriovenous heat exchanger (an elaborate, a simple rete, and a venae comitantes system) are found in the legs of birds. The anatomical differences between the different types of A-V associations are described, and the regulation of peripheral blood flow, in respect to maximal heat conservation and prevention of tissue damage, is discussed. A nasal temporal counter current heat exchanger, lowering the temperature of the expired air to values considerably below the body temperature, is the most important mechanism for minimizing the respiratory heat and water loss. In addition, a decreased ventilatory requirement, caused by a changed respiratory pattern and an increased parabronchial oxygen extraction, lowers the amount of air ventilated relative to the amount of oxygen uptake. Thus, the relative loss of heat and water is reduced.

Notes: [Auszug] One accepted method for a quantitative evaluation of the mixing problem would be careful analysis of the blood oxygen content in the incoming vessels to the heart compared with the proper conduits leaving the heart. No such analysis has ever been reported for any species of Amphibia in spite of the ...

Notes: [Auszug] Arteries were excised from freshly killed specimens of sea lions (Eumetopias jubatus), fur seals (Callorhinus ursinus], walrus (Odobenus rosmarus), harbour seals (Phoca vitulina) and ribbon seals (Histriophoca fasciata). Peripheral arteries were taken from the flippers. Central arteries of ...

Notes: Summary 1. Cardiovascular dynamics and the functional status of a double circulation have been studied in representatives of the three genera of lungfishes; Neoceratodus, Lepidosiren, and Protopterus. 2. The experimental approach consisted in continuous recording of heart rate, blood pressures and blood velocity from appropriate blood vessels in intact, unanesthetized fish, free to swim in large aquaria. Blood gas analyses were done in all species on repetitive samples from central blood vessels including pulmonary arteries and veins, coeliac artery, vena cava and afferent branchial arteries. 3. Branchial vascular resistance in Neoceratodus compares with teleost and elasmobranch fishes and correlates with a dominance of aquatic gill breathing in the bimodal gas exchange (Kg. 2). In Protopterus aerial breathing dominates and branchial vascular resistance is low in accordance with a general reduction in aquatic gas exchange and branchial vascularization. The small branchial vascular resistance varied with external conditions in apparent relation to the usefulness of the remaining branchial exchange circulation (Figs. 7 A and B). 4. Branchial vascular resistance increased in response to intravenous injections of acetylcholine, while adrenalin had a vasodilatory effect on branchial vessels in Neoceratodus and Protopterus; the two species studied to this effect (Figs. 19A and 20). 5. Venous return in all species depended on suctional attraction by the heart in addition to the driving force from the arterial side. Suctional attraction tended to be more important in the systemic than in the pulmonary veins (Figs. 12A and B). 6. In all species arterial systolic pressures and pulse pressures were higher in systemic than pulmonary arteries. Arterio-venous pressure difference and vascular resistance were consistently lower in the pulmonary than the systemic circuit (Figs. 5A and B, 8A and B). While resting in aerated water Neoceratodus had higher arterial pressures than Protopterus and Lepidosiren. 7. Blood velocity measurements were done in Protopterus. Blood velocity in the distal bulbus cordis segment was commonly discontinuous, but the ejection phase was prolonged by elastic recoil and contraction of the bulbus cordis, resulting in positive outflow throughout most of the cardiac cycle (Fig. 10). Pulmonary arterial blood velocity was continuous, commonly with a high diastolic velocity component (Fig. 11). Blood velocity in the vena cava and pulmonary vein was variable (Figs. 12A and B). 8. Spontaneous and artificial lung inflation elicited increased cardiac output and an increased heart rate and arterial blood pressure. The response appeared to be of reflex character (Figs. 16, 17). Voluntary airbreaths were regularly associated with marked shifts in regional blood flow increasing the proportion of pulmonary flow to total cardiac outflow. Swimming movements similarly elicited marked adjustments in regional blood flow (Fig. 18). 9. Blood gas analysis were done on all species and documented a clear tendency for preferential circulation of oxygenated and deoxygenated blood in Protopterus and Lepidosiren (Table). The extent of preferential circulation depended upon the intensity of airbreathing and the phase of the interval between airbreaths (Fig. 22)

Notes: Summary 1. Hcy containing blood of the crab, Cancer magister, has a P50 value of 19.6 mm Hg at normal arterial pH (7.7). The Bohr shift (-log P50/pH) was −0.27. Temperature had a marked effect on Oxy-Hcy affinity. Average oxygen capacity was 3.44 vol %. 2. Oxygen uptake was independent of ambient O2 tension down to about 50 mm Hg and showed an average value of 0.518 ml/kg/mm at 10° C in normoxic water. Oxygen extraction from the respiratory water current averaged 16 %. 3. Ventilation was measured directly using an electromagnetic flow meter technique. Ventilation values were high compared to other water breathers and averaged 625 ml/kg/min. 4. Arterial and venous blood were sampled from indwelling catheters in free moving, unrestrained animals. P aO2 averaged 91 mm Hg corresponding to nearly complete O2 saturation while P vO2 averaged 21 mm Hg giving a saturation of about 50 %. During activity both arterial and venous O2 tensions dropped but utilization of circulating O2 increased. The role of Hcy in O2 transport is discussed in the context of earlier studies on crustaceans which differ fundamentally from the results of the present study. 5. The average cardiac output value calculated from the Fick principle was 29.5 ml/kg/min. The ventilation perfusion ratio was about 22 and somewhat higher than reported for other water breathing animals. The average PO2 gradient from water to blood was 60.5 mm Hg which closely matches values from fishes and the cephalopod Octopus dofleini. 6. The results are analyzed and compared with similar information on gas exchange in other water breathers. It is concluded that effectiveness in gas exchange and gas transport is remarkably similar in widely diversified respiratory organs of aquatic animals.

Notes: Summary 1. The oxygen uptake of the cushion star Pteraster tesselatus was independent of ambient tension down to about 70 mm Hg and showed an average value of 10.5 ml/kg/hr in normoxic water in the range 10–12° C. The average uptake decreased approximately 2.65 times when the temperature was lowered from 10–12 to 5° C. 2. Oxygen extraction from the respiratory water current averaged 18 % at normoxic conditions. Effectiveness of oxygen removal was slightly higher than 50%; this is a very high value when compared with those of the crab Cancer magister and the cephalopod Octopus dofleini. 3. The exceptional ability of Pteraster to regulate its O2 uptake is based on the active irrigation of the dermal branchiae in the nidamental cavity. About 90 % of the total O2 uptake is derived from the active ventilation, the remaining 10 % being ascribed to passive diffusion through the body surface and tube feet. Ventilation values, measured with a termal velocity probe directly over the osculum, averaged 70 ml/min. 4. The transfer factor for Pteraster at 10–12° C was 0.0048 ml O2/kg/min/mm Hg, as compared with 0.0062 for Octopus dofleini and 0.0043 for Cancer magister. 5. Normal CO2 tensions in the coelomic fluid ranged between 1.00–1.40 mm Hg; coelomic fluid pH values ranged between 7.33–7.46 when the animals were in well aerated water at 11–12° C. 6. An effective barrier exists between the large fluid compartment of the stomach and the coelomic fluid, as indicated by measurements in both compartments. 7. The ability of Pteraster to regulate O2 uptake and the values for coelomic fluid tensions under different conditions, indicate that the principal determinant of the O2 uptake rate is the O2 tension prevailing at the tissues level.