Showing papers on "Protopterus published in 1968"

Respiration in the African lungfish Protopterus aethiopicus. I. Respiratory properties of blood and normal patterns of breathing and gas exchange.

Abstract: 1. Respiratory properties of blood and pattern of aerial and aquatic breathing and gas exchange have been studied in the African lungfish, Protopterus aethiopicus . 2. The mean value for haematocrit was 25%. Haemoglobin concentration was 6.2 g% and O2 capacity 6.8 vol. %. 3. The affinity of haemoglobin for O2 was high. P 50 was 10 mm. Hg at P COCO2, 6 mm. Hg and 25 °C. The Bohr effect was smaller than for the Australian lungfish, Neoceratodus , but exceeded that for the South American lungfish, Lepidosiren . The O2 affinity showed a larger temperature shift in Protopterus than Neoceratodus . 4. The CO2 combining power and the over-all buffering capacity of the blood exceeded values for the other lungfishes. 5. Both aerial and aquatic breathing showed a labile frequency. Air exposure elicited a marked increase in the rate of air breathing. 6. When resting in aerated water, air breathing accounted for about 90% of the O2 absorption. Aquatic gas exchange with gills and skin was 2.5 times more effective than pulmonary gas exchange in removing CO2. The low gas-exchange ratio for the lung diminished further in the interval between breaths. 7. Protopterus showed respiratory independence and a maintained O2 uptake until the ambient O2 and CO2 tensions were 85 and 35 mm. Hg respectively. A further reduction in O2 tension caused an abrupt fall in the oxygen uptake. 8. Gas analysis of blood samples drawn from unanaesthetized, free-swimming fishes attested to the important role of the lung in gas exchange and the high degree of functional separation in the circulation of oxygenated and deoxygenated blood. This work was supported by grant GB 4038 from the National Science Foundation and grant HE-08405 from the National Institute of Health. Established Investigator, American Heart Association. Work supported by Northeastern Chapter, Washington State Heart Association.

The Skull Morphology and Estivation Burrows of the Permian Lungfish, Gnathorhiza Serrata

Abstract: The Permian lungfish, Gnathorhiza, has been of particular interest to paleontologists because of its possible relationship to the modern lepidosirenid lungfish and because of its burrowing habits. New localities in the Wellington Formation of north-central Oklahoma have yielded numerous estivation burrows containing the articulated skull bones of these lungfish. The skull of Gnathorhiza serrata is described and a phylogeny is proposed for the post-Permian lungfish. The phylogeny, based primarily on skull roof bone patterns, proposes Gnathorhiza as an ancestral type leading to the modern Protopterus and Lepidosiren, with a second line, separate since the start of the Mesozoic, leading to Neoceratodus. The sectioned Permian estivation burrows show a number of features similar to the burrows of modern lepidosirenids. The burrow form and lithology suggest that Gnathorhiza used its mouth in burrowing and that it stood on its tail in the burrow during estivation. Different modal sizes of the burrows at differen...

Cardiovascular dynamics in the lungfishes

Abstract: 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)

Anti-metabolic extract from the brain of Protopterus aethiopicus.

Abstract: IT has been suggested that the brain of the aestivating lung-fish might contain an anti-metabolic agent1, perhaps not unlike the mono-amines secreted in the pons and medulla of cats as active agents in the control of sleep2.

Influence of Acetylcholine and Biogenic Amines on Branchial, Pulmonary and Systemic Vascular Resistance in the African Lungfish, Protopterus Aethiopicus

Abstract: The effects of acetylcholine and biogenic amines on the main vascular beds in lungfish were studied in intact animals and in isolated preparations perfused with physiological solution. Acetylcholine, histamine and serotonin increased the branchial as well as the pulmonary and the systemic vascular resistance. The sensitivity to acetylcholine was highest in the branchial blood vessels. Adrenaline and noradrenaline caused increased resistance in pulmonary and systemic blood vessels, whereas the branchial vascular bed usually responded by dilatation. The results are discussed in relation to the vascular responses obtained with the same pharmacological agents in other species of fish.