Stephen C. Wood

A comparative study of the oxygen equilibria of blood from 40 genera of Amazonian fishes

Abstract 1. We have examined the oxygen-affinity of the fresh, whole blood from representatives of 40 genera of Amazonian fishes. 2. When all the air-breathing fishes and all the water-breathing fishes were considered, no differentiation in oxygen affinity could be distinguished, although in two cases of closely related species, i.e. Osteoglossum , a water breather, vs Arapaima , an air breather, and Hoplias , a water breather, vs Hoplerythrinus , an air breather; the air breathers have bloods with lower oxygen affinity than do the water breathers. 3. Significant differences in the oxygen affinity were found when fishes were considered by habitat: the oxygen affinities were in general correlated with available environmental oxygen and relative oxygen demand of the fishes.

Acclimation to hypoxic water in facultative air-breathing fish: Blood oxygen affinity and allosteric effectors

Abstract 1. Blood oxygen affinities, erythrocytic nucleoside triphosphate concentrations (NTP) and other hematological parameters were measured in facultative air-breathing fish from the Amazon after acclimation to well-aerated (“normoxic”) and hypoxic water ( P O 2 = 125–135 and 20–25 mm, respectively). 2. In the armored catfish Hypostomus sp. and Pterygoplichthys sp., hypoxia induces intermittent surfacing to gulp air and results in lower NTP levels, chiefly through significant decreases in guanosine triphosphate (GTP). The subsequent increases in blood O 2 affinity appear adaptive to lowered time average internal O 2 tensions. No similar changes were seen in the ell Synbranchus which breathes air almost continuously when kept in hypoxic water. 3. The results are discussed in terms of their adaptive significance, and compared with data on temperate fish.

Cardiopulmonary Function in High Altitude Residents of Ladakh

We studied residents of high altitude in Ladakh, India, to determine the effects of altitude, age, gender, and ethnicity on gas exchange and pulmonary function. Physical examinations, including pulse oximetry, hemoglobin concentration, end-tidal PCO2, and pulmonary function, were conducted on resting Ladakhi and Tibetan subjects at altitudes of 3300, 4200, and 4500 m. A total of 574 men and women, ranging in age from 17 to 82, were studied. At 3300 m, Ladakhis had higher heart rates than Tibetans in both genders and higher PETCO2 in women. Above 4000 m, 21 of the 141 men studied (15%) had Hb concentrations higher than 20 g/dL, with one confirmed case of Monges disease. There was no gender difference in SaO2 at any altitude except for pregnant women. At 4600 m, Tibetans had significantly higher peak flows and lower PETCO2 than Ladakhis. Ladakhi men had higher diastolic BP than women (91 vs. 81), with no difference in systolic BP. There was no gender difference in BP for Tibetans. An important spirometry finding for both groups was high air flows, with mid-maximal expiratory flow (MMEF) at 130% to 150% of predicted values, compared with 85% for sojourner controls, and FEV1/FVC at 115%, compared with sojourner controls at 98%. Improved lung mechanics may be an important adaptation to the lifelong sustained increase in resting ventilation as well as to indoor biomass smoke and outdoor dust exposure of these populations at high altitude.

Respiration and acid-base balance in the salamander,Ambystoma tigrinum: Influence of temperature acclimation and metamorphosis

SummaryEffects of temperature acclimation (5 or 25 °C for 2–4 weeks) and metamorphosis on oxygen uptake, acid-base balance and blood-O2 affinity have been investigated inAmbystoma tigrinum. The results differ from previous studies in three ways. (1) The transition from gilled to gill-less adults had no effect on the O2 affinity of blood. (2) Cold acclimation increased blood O2 affinity in neotenes and had no effect in adults. (3) O2 uptake increased, rather than decreased, after acclimation to a higher temperature. The results resemble previous studies also in three ways. (1) O2 uptake increased with the transition from gilled-neotenes to gill-less adults as did the dependence on air-breathing. (2) Metamorphosis resulted in CO2 retention and a fall in arterial pH. (3) The temperature coefficient of blood pH was about −0.014dpH/dT in vivo and in vitro. The physiological significance of the results is discussed with respect to the natural history, modes of breathing, and dependance on aerial respiration ofAmbystoma tigrinum.

Effects of erythrocytic nucleoside triphosphates on oxygen equilibria of composite and fractionated hemoglobins from the facultative air-breathing amazonian catfish,Hypostomus andPterygoplichthys

Abstract 1. Oxygen equilibria of Hypostomus and Pterygoplichthys hemoglobins and their sensitivities to the erythrocytic nucleotide triphosphates (NTP), ATP and guanosine triphosphate (GTP) are studied to investigate the mechanisms by which blood adapts to air- and water-breathing (cf. Weber et al. , 1979). 2. Hemoglobins of both species are heterogeneous. All hemoglobin fractions isolated by iso-electric focusing reveal a high sensitivity to NTP, but GTP depresses O 2 affinity about twice as effectively as ATP. A cathodal hemoglobin component with a reversed Bohr effect was found in Pterygoplichthys but not in Hypostomus . 3. The data are discussed in relation to the in vivo cofactor modulation of blood O 2 affinity and the adaptive significance of functional heterogeneity of fish hemoglobins.

Effects of endurance training and long distance running on blood viscosity

The effect of endurance training on blood viscosity was studied by comparing blood rheological properties in control subjects (untrained) and endurance trained subjects. The effect of running on blood viscosity was studied in the 33 endurance trained subjects before and after a 48-km mountain race (Sandia Wilderness Crossing Research Run). Runners started at an altitude of 1700 m, ran 26 km to 3300 m, then descended 22 km to finish at 1900 m. Venous blood viscosity (eta b) and plasma viscosity (eta p) were measured at 37 degrees C at shear rates of 11.25, 22.5, 45, 90, and 225.s-1, using a cone-plate viscometer. Endurance trained subjects had significantly higher pre-race blood viscosity at 11.25 and 22.5.s-1 than control subjects but similar plasma viscosity and hematocrits. Following the race, there was no significant change in mean hematocrit, but eta b increased significantly at all shear rates except 225.s-1. Plasma viscosity at 225.s-1 increased significantly from 1.44 to 1.53 cP following the run. Since eta b did not increase, an increase in red cell deformability is inferred. The mechanism of the increase in eta b at lower shear rates in runners is due in part to the higher plasma viscosity. An additional mechanism at lower shear rates is in an increase in red cell aggregation. Increased plasma fibrinogen was measured in six of six resting subjects taken from 1600 m to 3300 m and is speculated to be the mechanism of enhanced aggregation and deformability in the runners.

Chemical control of breathing in the lizard, Varanus exanthematicus

1. 1. In Varanus exanthematicus, alterations of inspired and end-tidal gas pressures resulted in rapid ventilatory responses. This, as well as other physiological characteristics, contributes to a homeostatic ability unusual for a reptile. 2. 2. In contrast to the lizard Lacerta, the varanid showed a positive ventilatory response to hypoxia. 3. 3. Whereas CO2 breathing depressed breathing frequency in other lizards, both tidal volume and frequency increased in Varanus. 4. 4. End-tidal Pco2 increased significantly after feeding, presumably compensating for an alkaline “tide” of digestion. The increased end-tidal Pco2 not due to a decrease in ventilation.

Oxygen transport in the green sea turtle

SummaryGreen sea turtles (Chelonia mydas) are well known as endurance swimmers and divers. Physiological correlates of these traits were studied in 9 adult sea turtles (mean body mass=87 kg) at a body temperature of 25°C. The respiratory properties of the blood were similar to those of other turtles except for a higher oxygen affinity (P50=18.2 Torr, pH 7.6), which may be an allometric function. Resting, systemic blood flow, calculated from the Fick principle was 21.5 ml·kg−1. min−1, similar to values reported for other turtles. Pulmonary blood flow, measured by mass spectrometry of acetylene uptake in the lungs was 24.0 ml·kg−1·min−1, not significantly different from the calculated systemic flow. Other evidence of a small (net) intracardiac shunt is the high arterial saturation (ca. 90%) of arterial blood. This distinctive feature of O2 transport inC. mydas provides an

Respiratory properties of blood and hemoglobin solutions from the piranha

[Ca_{O_2 } - C\bar \upsilon _{O_2 } ]