Gmo Maloiy

Design of the mammalian respiratory system. V. Scaling morphometric pulmonary diffusing capacity to body mass: wild and domestic mammals.

This paper utilizes a comparative approach to establish the relationship between morphometric diffusing capacity for oxygen (DLo2) and maximal oxygen consumption (Vo2max). DLo2 and Vo2max were determined on the same 21 individuals in African mammals spanning a range in body mass from 0.4 to 240kg. We confirmed earlier findings that Dlo2 was proportional to Mb0.99 while Vo2max was proportional to Mb0.79. Thus, the ratio of Dlo2/Vo2 is approximately proportional to Mb0.20. We conclude that large animals require a larger pulmonary diffusing capacity to transfer oxygen at the same rate from air to blood.

Design of the mammalian respiratory system. IX. Functional and structural limits for oxygen flow.

This paper presents the synthesis and interpretation of a series of correlated studies of the mammalian respiratory system--measurements of maximal rate of O2 consumption, the lungs diffusing capacity, the mitochondrial volume, and the capillary number and length in skeletal muscle. It discusses the results with respect to the principle of symmorphosis, i.e. of morphogenesis adapted to functional needs. We find that the accumulated evidence supports this principle at all organizational levels considered, although the models used for structure-function correlation need further refinement.

Respiratory properties of blood in awake and estivating lungfish, Protopterus amphibius☆

Blood respiratory properties have been studied in awake and estivating African lungfish, Protopterus amphibius. Fish had been estivating 28-30 months when blood was sampled. Hematocrit, O2 capacity and blood hemoglobin concentration increased by about 50% during estivation. Red cell Hb concentration (MCHC) was unaltered. Total blood concentration of nucleoside triphosphates (NTP) was reduced 50% in estivation. Thin-layer chromatography showed that the change in NTP resulted from a GTP/Hb (guanosine triphosphate) reduction to 20% of the value in awake fish. ATP (adenosine triphosphate) concentration remained largely unaltered. GTP/Hb changes were accompanied by marked changes in O2 affinity. The P50 value in blood from awake fish was 33 mm Hg at pH 7.5 compared to 9 mm Hg for the estivating fish. The n-value changed insignificantly. An increased Bohr effect was present in estivating fish, but its importance will depend on circulating pH in the two states. Standard bicarbonate ranged from a low of 8.6 mMol-L-1 (P plasma) at pH 7.5 in an awake fish to 49.6 mMol-L-1 (P) in an estivating fish. CO2 dissociation curves showed a variable Haldane effect having its highest value in the in vivo range of PCO2. The striking increase in O2-Hb affinity during estivation is regarded as an adaptation to a reduced alveolar O2 availability associated with estivation. Altered mechanics of pulmonary ventilation and reduced ambient O2 availability caused by the subterranean habitat may have been selection pressures for the development of the high O2 availability caused by the subterranean habitat may have been selection pressures for the development of the high O2 affinity. The mechanism behind it rests with the recorded change in erythrocytic concentration of GTP.

Transpiratory water loss and metabolism of beetles from arid areas in East Africa

Abstract 1. 1. Carabid beetles have rates of transpiratory water loss and metabolic rates which are higher than those of tenebrionid beetles. Within each family, dry habitat beetles have lower rates of water loss than beetles from mesic or hygric habitats, but no habitat-related difference was observed with regard to metabolic rates. 2. 2. When rates of transpiratory water loss of beetles of the two families are plotted as a function of metabolic rates, it appears that for dry habitat beetles, the metabolic rate is the single determinant of transpiratory water loss. 3. 3. This is interpreted as indicating that respiratory water loss is the dominating component of water loss in both carabids and tenebrionids in dry habitats, and that the difference between the families with respect to rates of water loss reflects the difference in metabolic rates. 4. 4. Carabid beetles have considerably higher extracellular concentrations of sodium than the tenebrionids. Seen in the light of the high energetic cost claimed to be involved in sodium transport, this observation is interpreted as indicating that the high rates of water loss and metabolism of the carabids are due to active extrusion of sodium from the cells of the beetles. 5. 5. The ecophysiological significance of these differences is discussed.

Functional properties of hemoglobins in the teleostTilapia grahami

SummaryThe oxygen binding properties ofTilapia grahami hemoglobins have been investigated. The whole blood hemolysate possesses at 35°C a high oxygen affinity (P50∼ 4.0 mmHg). The O2Hb equilibrium is moderately affected by the ionic strenght chloride concentration) of the hemoglobin solution, while in contrast the temperature sensitivity of the O2Hb equilibrium was very high (ΔH=−20.0 kcal.mole−1). Tilapia hemoglobin separated into 7 main fractions having nearly similar Bohr factors (−0.42<ø<−0.59) in a pH range from 7.2 to 7.6. The Bohr factor andn-value of the composite hemoglobins fell within the range for the individual Hb fractions. Addition of the organic nucleoside triphosphates, ATP and GTP, both occurring inTilapia grahami red cells, caused a marked increase inP50 as well asn-values, with GTP having an effect nearly twice that of ATP on oxygen affinity. Tilapia grahami lives in conditions of high alkalinity (9.6<pH<10.5), high temperature (Tmax≅43°C) and variable O2 concentration. The results are discussed in relation to hemoglobin function in this habitat.

Ventilation and expired gas composition in the flamingo, Phoenicopterus ruber, during normal respiration and panting

Direct measurements of ventilatory parameters have been employed in a study of ventilatory adjustments and changes in expired gas composition during heat stress in the greater flamingo, Phoenicopterus ruber. At thermoneutrality Tb = 39.5 C) average resting values were breathing rate (f) 9.6·min⁻¹, tidal volume (VT) 40.4·ml·kg⁻¹, ventilation V̅I 382.6·ml·min⁻¹·kg⁻¹, oxygen uptake

A fish in extreme alkalinity.

\bar{V}_{O_{2}}

A comparative study of basal metabolism and thermoregulation in a folivorous (Colobus guereza) and an omnivorous (Cercopithecus mitis) primate species.

1.03·ml O₂STP. g⁻¹·h⁻¹. The f is lower and all other parameters higher than values predicted from allometric equations, and PETCO2 averaged 40.3 mm Hg and PETO2 108.3 mm Hg. During rapid shallow panting at 40 C < Tb < 42 C, f increased 23 times, V̅T was reduced to 15% of normal and closely matched the tracheal dead space, and VI increased 3–3.5 times. The rapid shallow breathing during panting was interrupted at regular intervals by brief sequences of deeper breaths (flush outs). The importance of the described panting pattern for thermal and respiratory homeostasis is discussed.