Pinder, Alan
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Item Open Access The respiratory development of Atlantic salmon .1. Morphometry of gills, yolk sac and body surface(1996-12) Wells, PR; Pinder, Alan W.During development from larva to juvenile in Atlantic salmon, Salmo salar, there is a change in the anatomical potential for gas exchange among gills, body skin and yolk sac as the larvae resorb yolk, grow and develop gills. Newly hatched Atlantic salmon have poorly developed gills but do have a high skin area to mass ratio and a large well-vascularized yolk sac. Cutaneous surfaces accounted for over 95 % of the total area available for respiration in newly hatched Atlantic salmon (body mass 0.032-0.060 g). The branchial contribution to total area increased rapidly, however, so that by the end of yolk absorption (body mass 0.19-0.23 g) it constituted 22 % of the total area and overtook cutaneous surface area between 5 and 6g wet body mass. Harmonic mean diffusion distance across the skin increased through development from 20 mu m at hatch (14 mu m across the yolk sac) to 70 mu m in an 11g fish. Diffusion distances across both the filaments and lamellae of the gills decreased through development, from 3.7 to 2.4 mu m for lamellae and from 14.5 to 10.8 mu m for filaments. The total anatomical diffusion factor (ADF, mass-specific surface area per unit diffusion distance) remained constant over early development and appeared to be higher than in adult fish. The distribution of ADF changed over early development from 50% yolk sac, 42 % body surface and 8 % branchial in newly hatched fish to 68 % branchial and 32 % cutaneous at the end of yolk resorption. Generally, early post-hatch development of gills, ADF and some cutaneous surfaces showed high mass exponents, After yolk resorption (body mass 0.2g), however, these coefficients were lower and closer to unity. The change in scaling at the end of yolk resorption in this study may reflect the completion of larva to juvenile metamorphosis in Atlantic salmon. Comparison between our data and values in the literature suggests that the timing of gill development is related more to developmental stage than to body size.Item Open Access The respiratory development of Atlantic salmon: II. Partitioning of oxygen uptake among gills, yolk sac and body surfaces(1996) Wells, Patrick R.; Pinder, Alan W.During post-hatch development of Atlantic salmon (Salmo salar L.), O-2 uptake partitioning changes from primarily cutaneous to primarily branchial. Over 80% of post-hatch O-2 uptake was cutaneous, with the yolk sac responsible for 33% of total O-2 uptake. The well-vascularized yolk sac was a less effective gas exchanger than the unperfused skin of the body, suggesting that oxygen delivery is by direct diffusion to the tissues. Branchial O-2 uptake increased quickly as gill lamellae developed, contributing 60% of total O-2 uptake before the completion of yolk resorption (body mass 0.2 g) and increasing to 69-81% in fish weighing over 0.3 g. The area-specific O-2 uptake of the skin decreased through development as skin thickness increased, while that of the gills increased from 0.10 mu-g h-1 mm-2 to 0.23 mu-g h-1 mm-2. Partitioning of O-2 uptake of the skin and gills changed in concert with changes in the partitioning of the anatomical diffusion factor (ADF, mass-specific surface area per unit diffusion distance) between skin and gills, which changed from more than 95% to less than 10% cutaneous; thus, ADF is a useful rough indicator of oxygen uptake potential. Caution should be used in predicting oxygen uptake potential from ADF, however, because O-2 uptake per unit diffusion barrier of the yolk sac was less than half that of the general body surface, and O-2 uptake per unit diffusion barrier of the gills changed dramatically over development.Item Open Access Oxygen transport in egg masses of the amphibians Rana sylvatica and Ambystoma maculatum: Convection, diffusion and oxygen production by algae(1994) Pinder, Alan W.; Friet, Stephen C.Many amphibians lay their eggs in gelatinous masses up to 10-20 cm in diameter, posing problems for diffusive oxygen delivery. Oxygen may also be provided by water convection between eggs or by oxygen production by endogenous algae. We studied egg masses of two local amphibians, Rana sylvatica and Ambystoma maculatum, to estimate the importance of each of these processes. We injected dye to check for water channels, measured oxygen partial pressures within egg masses to determine the influence of external water convection and lighting, measured oxygen consumption and production in darkness and light and calculated expected gradients through egg masses with a cylindrical, homogeneous egg mass model. Rana sylvatica had relatively loose egg masses with water channels between the eggs; water convection was important for oxygen delivery. Ambystoma maculatum had firm egg masses with no spaces in the jelly between eggs; thus, there was no opportunity for convective oxygen delivery. The egg masses were cohabited by Oophila ambystomatis, a green alga found specifically in association with amphibian egg masses. Oxygen delivery in A. maculatum was by diffusion and by local production by the algal symbiont. Analysis of a cylindrical egg mass model and measurement of oxygen gradients through egg masses indicated that diffusion alone was not adequate to deliver sufficient O-2 to the innermost embryos at late developmental stages. In the light, however, egg masses had a net oxygen production and became hyperoxic. Over the course of a day with a 14 h: 10 h light:dark cycle, the innermost embryos were alternately exposed to hyperoxia and near anoxia.Item Open Access Heart-Rate and Hemolymph Pressure Responses to Hemolymph Volume Changes in the Land Crab Cardisoma-Guanhumi - Evidence for Baroreflex Regulation(1990-01) BURGGREN, W.; Pinder, Alan W.; MCMAHON, B.; DOYLE, M.; WHEATLY, M.No abstract available.Item Open Access Larval cardiorespiratory ontogeny and allometry in Xenopus laevis(1995) Orlando, Kent; Pinder, Alan W.Very little is known about the early development of cardiorespiratory regulatory mechanisms in newly hatched amphibian larvae. We tested whether early cardiovascular responses to hypoxia reflect local flow regulation in tissues and whether regulation of ventilation would improve during larval development Cardiac output was calculated from heart rate and stroke volume, and buccal pumping rate was measured at 19 degree -21 degree C for Xenopus laevis larvae between Nieuwkoop and Faber stages 44 (just after hatching) and 57 (4-1,102 mg) denied access to air at a range of ambient aquatic PO-2 from normoxia (150-155 mmHg) to severe hypoxia (27-45 mmHg). Cardiac output decreased in severe hypoxia in stage 44-49.5 larvae, but not in stage 51-54 larvae, because heart rate decreased significantly in the early larvae, probably a direct effect of O-2 limitation on cardiac metabolism. Stroke volume did not change significantly in hypoxia in either early- or late-stage larvae. Thus there was no evidence of a tissue-mediated increase in cardiac output in hypoxia. Buccal pumping increased by about 50% over normoxic rates in moderate hypoxia in all larvae but sharply decreased in severe hypoxia, decreasing more in younger larvae than older. Younger larvae show significantly more variability in buccal pumping than older larvae, which suggests that regulatory mechanisms are not yet fully developed in early larvae. Cardiac output scales to body mass with a allometric coefficient of 1.15 +- 0.15 (95% confidence limits), significantly higher than literature values for O-2 uptake (0.83), implying that cardiovascular gas transport may be less important (compared to direct diffusion) in very small early-stage larvae than in larger, late-stage larvae.Item Open Access Effect of Coronary Ablation and Adrenergic-Stimulation on In-Vivo Cardiac-Performance in Trout (Oncorhynchus-Mykiss)(1994-01) GAMPERL, AK; Pinder, Alan W.; BOUTILIER, RGIn fish, catecholamine-induced changes in cardiac performance in vivo are the result of complex interactions between the direct adrenergic effects on the heart and peripheral circulation and the reflex responses to increased blood pressure. In addition, coronary artery transport of catecholamines and oxygen to the compact myocardium may be essential for maximal in vivo cardiac performance during adrenergic stimulation. Cardiac output (Q), heart rate (fH), stroke volume (Vs) and dorsal aortic pressure (PDA) were measured in trout with intact or ablated coronary arteries at rest and following intraarterial administration of 0.2, 0.5, 1.0 and 2.0 mu g kg(-1) adrenaline. Resting Q, fH, Vs and PDA were the same in fish with intact and ablated coronaries at 48h post-surgery, averaging approximately 18 ml min(-1) kg(-1), 42 beats min(-1), 0.42 ml kg(-1) and 2.2 kPa, respectively. All cardiovascular variables showed a strong relationship between response magnitude and adrenaline dose. However, our results indicate that adrenaline doses above 0.5 mu g kg(-1) may have a limited ability to increase Q (ED(50) 0.22 mu g kg(-1)). Coronary artery ablation had little effect on post-injection Q, Vs, PDA or fH at any dose of adrenaline. In both intact and ablated groups, two types of responses in Q were observed following adrenaline injection. In the 'type 1' response, Q increased shortly (15-30s) after adrenaline administration, as increases in Vs more than compensated for a pressor-stimulated reflex bradycardia. In the 'type 2' response, alterations in Q were biphasic. In the initial minutes post-injection, Q fell and reached a minimum level at 1-2 min, the result of an immediate drop in fH and a delayed post-injection increase in Vs. Thereafter, Q gradually increased as a result of concordant increases in fH and Vs. Although time to maximum Q was 5-6 min longer for fish exhibiting type 2 responses, there was no difference in maximum Q increase or in the time courses for changes in fH and PDA between response types. Our results suggest (1) that during normoxic conditions, cardiac performance does not depend highly on coronary blood flow; (2) that the capacity of adrenaline to increase Q may be limited by elevations in output pressure and/or by the low dose (concentration) of adrenaline required to achieve near maximal adrenergic stimulation of the heart; and (3) that fish exhibiting type 2 responses have an increased barostatic gain (% Delta fH per unit PDA) compared with those with type 1 responses.Item Open Access The burrow microhabitat of the land crab Cardisoma guanhumi: Respiratory/ionic conditions and physiological responses of crabs to hypercapnia(1993) Pinder, Alan W.; Smits, Allan W.Cardisoma guanhumi in Puerto Rico spend much of the dry season in burrows that descend to groundwater. Burrows are sometimes 3-4 m deep and may be capped with dried mud for over 3 mo. Samples of gas and water from burrows at three locations in Puerto Rico were analyzed for O-2, CO-2, and ions. Osmolality and ion composition varied widely with location, from about 10% to 130% of seawater. Both gas and water PO-2's were generally 90-120 mmHg, although some water samples were extremely hypoxic (PO-2 lt 20 mmHg). Most burrows were extremely hypercapnic, with gas and water PCO-2's up to 60 and 90 mmHg, respectively. Whether the burrow was plugged or even occupied by a crab made little difference to ion or gas concentrations. Radiotelemetry of the vertical position of crabs in their burrows indicated that they did not avoid hypercapnia and hypoxia by staying close to the entrance, Cardisoma guanhumi are thus exposed to extreme changes in PCO-2 when they descend deep in their burrows after foraging at dawn and dusk. Impedance measurements of branchial ventilation and heart rate in resting crabs exposed to environmental hypercapnia in artificial burrows revealed two distinct types of ventilatory responses based on the degree and duration of hypercapnia: hyperventilation in response to gradual, chronic exposure to elevated burrow CO-2 and apnea in response to rapid elevations of burrow CO-2 above 4%. These physiological responses suggest the presence of both "external" and "internal" receptors of hypercapnia that may allow Cardisoma to buffer large acid-base disturbances when moving between extremes in gaseous microenvironments.Item Open Access Influence of Hypoxia and Adrenaline Administration on Coronary Blood-Flow and Cardiac-Performance in Seawater Rainbow-Trout (Oncorhynchus-Mykiss)(1994-08) GAMPERL, AK; Pinder, Alan W.; GRANT, RRTo investigate the relationship between cardiac performance and coronary perfusion, cardiovascular variables (Q, Vs, fH, PDA) and coronary blood flow (q(cor)) were measured in rainbow trout (Oncorhynchus mykiss) (1.2-1.6 kg) before and after adrenergic stimulation (1.0 mu g kg(-1) adrenaline) under conditions of (1) normoxia, (2) hypoxia (approximate Pwo(2) 12 kPa) and (3) 2.5 h after returning to normoxia. q(cor) for resting fish under normoxic conditions was 0.14+/-0.02 ml min(-1) kg(-1) (approximately 0.85 % of Q). When exposed to hypoxia, although bath resting Q and q(cor) increased, q(cor) increased to a greater degree (Q by 17 % and q(cor) by 36 %). During hypoxia, maximum adrenaline-stimulated h was comparable to that observed for normoxic fish. However, because Q was elevated in resting hypoxic fish, the capacity of hypoxic fish to increase Q above resting levels was 50 % lower than that measured in normoxic fish. Although maximum qcor in adrenaline-injected hypoxic trout was greater than that measured in normoxic trout, post-injection increases in q(cor) (above resting levels) were not different between the two groups. Two and a half hours after hypoxic exposure, resting Q was still elevated (11%) above normoxic levels, and the ability to increase and when adrenergically stimulated was not fully restored. These results suggest (1) that resting q(cor) in salmonids is approximately 1 % of Q, (2) that increases in q(cor) may be important in maintaining cardiovascular performance during hypoxic conditions, (3) that interactions between alpha-adrenergic constriction and metabolically related vasodilation of the coronary vasculature are important in determining q(cor) in fish, (4) that exposure of fish to moderate environmental hypoxia reduces the scope for adrenergically mediated increases in h, and (5) that periods of recovery in excess of several hours are required before cardiovascular performance returns to pre-hypoxic levels.Item Open Access Effect of Boundary Layers on Cutaneous Gas Exchange(1990) Pinder, Alan W.; Feder, M. E.Boundary layers may offer significant resistance to cutaneous oxygen uptake by amphibians in water. This hypothesis was tested by measuring resistance to oxygen uptake as a function of water velocity in bullfrogs submerged at 5.degree. C and by direct measurments of the boundary layer with oxygen microelectrodes. The oxygen diffusion boundary layer was easily measurable with oxygen microelectrodes. The proportion of the total resistance to oxygen uptake represented by the boundary layer increased from 35% in a water velocity of 5 cm s-1 to over 90% at 0.1 cm s-1. At water velocities below 1 cm s-1 oxygen uptake was limited by the resistance of the boundary layer. At 0.1 cm s-1, the partial pressure of oxygen immediately adjacent to the skin was only 2 kPa (15 mmHg); placing an immobilized frog is still water was tantamount to placing it in anoxic water. Body movements disrupted boundary layers efficiently; even occasional small movements by the animal (1 min-1) were sufficient to maintain oxygen uptake in still water.