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S F Perry

Publications and source records attributed to S F Perry.

At least 127 records · Page 7Linked to original sources
PubMed1988

Characterization of branchial transepithelial calcium fluxes in freshwater trout, Salmo gairdneri.

Experiments were performed to determine whether gill transepithelial calcium fluxes in the freshwater trout (Salmo gairdneri) are passive or require active transport and to characterize the mechanisms involved. A comparison of the in vivo unidirectional flux ratios with the flux ratios calculated according to the transepithelial electrochemical gradients revealed that calcium uptake from the water requires active transport of Ca2+. The inhibition of calcium uptake by external lanthanum, the specific deposition of lanthanum on the apical surface of chloride cells, and the favorable electrochemical gradient for calcium across the apical membrane suggest that the initial step in branchial calcium uptake is the passive entry of calcium into the cytosol of chloride cells through apical channels that are permeable to calcium. The study of gill basolateral plasma membrane vesicles demonstrated the existence of a high-affinity calmodulin-dependent calcium-transporting system [half-maximal Ca2+ concentration (K0.5) = 160 nM, Vmax = 1.86 nmol.min-1.mg protein-1]. This system actively transports calcium from the cytosol of chloride cells into the plasma against a sizeable electrochemical gradient, thereby completing the transepithelial uptake of calcium. Calcium efflux occurs passively through paracellular pathways between chloride cells and adjacent pavement cells or between neighboring pavement cells.

Animals↗
PubMed1988

Hypocalcin from Stannius corpuscles inhibits gill calcium uptake in trout.

Bidirectional whole body flux and branchial Ca2+ influx were measured in freshwater rainbow trout. Intra-arterial injections of homogenates of Stannius corpuscles (CS) as well as of a 54-kDa isolated product (hypocalcin) exerted an inhibitory effect on whole body Ca2+ influx, but did not effect Ca2+ efflux. Hypocalcin was more effective in reducing Ca2+ influx in trout acclimated to low-calcium freshwater than in fish from normal-calcium water. We conclude that the isolated product (hypocalcin) represents the hypocalcemic principle of the CS. Similar doses of hypocalcin caused quantitatively similar decreases in Ca2+ influx in vivo and in the isolated perfused head preparation. This indicates that the gills form the principle target for hypocalcin in trout. The branchial transepithelial potential did not change during hormone treatments. Possible mechanisms of hypocalcin action are suggested.

Animals↗
PubMed1988

Effects of acid-base variables on in vitro hepatic metabolism in rainbow trout.

The effects of hypercapnia (1% CO2), and the independent effects of changes in extracellular pH (pHe), PCO2 and [HCO3-] on intracellular pH (measured by the DMO method) and lactate metabolism (measured by utilization of 14C-labelled lactate), were examined in rainbow trout hepatocytes in vitro. Simulated uncompensated hypercapnia (high PCO2, low pHe, moderately increased [HCO3-] led to a substantial depression in the production of CO2 (44%) and glucose (51%) from lactate. In simulated compensated hypercapnia (high PCO2, normal pHe, high [HCO3-], metabolism was still significantly inhibited (18-33%). Subsequent multifactorial design experiments determined that variations in PCO2, pH and [HCO3-] independently affected metabolism; increased PCO2 and decreased pH inhibited metabolism, but increased [HCO3-] stimulated metabolism. These results are interpreted in terms of the effects of acid-base variables on enzymatic and transport pathways, and the possible causes of decreased hepatic glycogen stores during in vivo hypercapnia are discussed.

Acid-Base Equilibrium↗
PubMed1987

The effects of prolonged epinephrine infusion on the physiology of the rainbow trout, Salmo gairdneri. II. Branchial solute fluxes.

Rainbow trout were infused continuously for 24 h with epinephrine in order to elevate circulating levels to those measured during periods of acute extracellular acidosis (about 5 X 10(-8) mol l-1). Concomitant effects on branchial solute fluxes were evaluated. Epinephrine infusion caused complex and differential adjustments of Na+ and Cl- unidirectional fluxes (influx and efflux) resulting in a significant elevation of the arithmetic difference between Na+ and Cl- net fluxes (JnetNa+-JnetCl-). A significant correlation existed between JnetNa+-JnetCl- and net branchial acid excretion (JnetH+), thereby suggesting a role for epinephrine in piscine acid-base regulation. The stimulation of JnetH+ by epinephrine was due primarily to a reduction in the excretion of titratable acid (JTA) accompanied by non-significant changes in ammonia excretion (JAmm). The results are discussed with respect to a role for epinephrine in regulating acid-base disturbances by interacting with branchial ionic exchange mechanisms.

Acidosis↗
PubMed1987

The effects of prolonged epinephrine infusion on the physiology of the rainbow trout, Salmo gairdneri. III. Renal ionic fluxes.

Rainbow trout were infused continuously for 24 h with epinephrine in order to evaluate the effects of elevated circulating levels of epinephrine on selected renal variables. Pronounced effects of epinephrine included elevation of urine flow rate and concomitant increases in the excretion of all measured electrolytes (Na+, Cl-, K+, Ca2+, inorganic phosphate) with the exception of ammonium and bicarbonate ions. Significant reductions in the tubular reabsorption of Na+ and Cl- also contributed to enhanced excretion of these ions. Similarly, epinephrine affected the tubular handling of NH4+ and HCO3- with NH4+ secretion decreasing and HCO3- reabsorption increasing. We speculate that the stimulation of HCO3- reabsorption was a consequence of elevated tubular H+ secretion. Such a mechanism may be important to permit plasma HCO3- retention during periods of internal acidosis. The results are discussed with reference to the role of the fish kidney in regulating acid-base disturbances and the possible interactive effects of elevated epinephrine.

Animals↗
PubMed1985

Effects of temperature change on acid-base regulation in skipjack tuna (Katsuwonus pelamis) blood.

The effects of temperature change (in vitro) on acid-base balance of skipjack tuna blood were investigated. By examining the relationship between blood pH and temperature (in vitro) under conditions of constant CO2 tension (open system), it was observed that dpH/dT = -0.013 U/degrees C. This value falls well within the range of in vivo values reported for other ectothermic vertebrates, and is only slightly different than results obtained in vitro under conditions of constant CO2 content (closed system; dpH/dT = -0.0165 U/degrees C). It is concluded that changes in pH following temperature changes can be accounted for solely by the passive, in vitro behaviour of the chemical buffer system found in the blood, so that active regulatory mechanisms of pH adjustment need not be postulated for skipjack tuna.

Acclimatization↗
PubMed1985

Isolated perfused head of rainbow trout. I. Gas transfer, acid-base balance, and hemodynamics.

Branchial gas transfer, acid-base balance, and hemodynamics were critically evaluated and compared in Ringer-perfused and blood-perfused heads of rainbow trout. Blood perfusion stimulated O2 uptake and CO2 excretion across the gills to values more representative of intact fish. The stimulatory effect of blood on gas transfer was due to increased O2 carrying capacity (O2 uptake) and the presence of erythrocytic carbonic anhydrase (CO2 excretion). Adding carbonic anhydrase to Ringer enhanced CO2 excretion in a manner similar to blood. During Ringer perfusion, arteriovenous pH gradients were abnormal (arterial pH less than venous pH). Perfusion with blood or addition of carbonic anhydrase to Ringer reversed the pH gradients to typical in vivo levels. Branchial vascular resistance to flow was abnormally high in both Ringer- and blood-perfused preparations, primarily as a result of low dorsal aortic pressure. Input pressure increased during blood perfusion and was similar to ventral aortic pressure in vivo. Perfusion with Ringer may have caused irreversible deterioration of gill function as indicated by decreased arterial Po2 and O2 extraction effectiveness after a rapid switch from Ringer to blood perfusion. The results are discussed with reference to the suitability of perfused trout head preparations for studying gill gas transfer, acid-base balance, and hemodynamics. Comparisons are made between the perfused head preparation and intact fish as well as with other types of perfused gill preparations.

Acid-Base Equilibrium↗
PubMed1985

Isolated perfused head of rainbow trout. II. Ionic fluxes.

Branchial ionic transport processes were evaluated and compared in Ringer-perfused and blood-perfused heads of rainbow trout. Rates of Na+ and Cl- influx were similar to in vivo levels at the onset of perfusion. Na+ uptake deteriorated more rapidly over time during Ringer perfusion, whereas Cl- uptake was relatively stable regardless of the perfusate employed. Transepithelial potentials (TEP) were similar to values reported for intact freshwater teleosts and were unstable only during the initial period of blood perfusion. The TEP was extremely dependent on the external concentration of NaCl. Ammonia excretion (JNH4+net) was normal during both types of perfusion, although blood did have a stabilizing effect on JNH4+net over time of perfusion. JNH4+net was stimulated by the addition of carbonic anhydrase to Ringer, without a concomitant increase in Na+ uptake. Branchial net fluxes of Na+ and Cl- were stable but slightly negative and in this regard represented slightly stressed intact animals. Net acid flux (JH+net), however, was similar to in vivo rates. Na+ and Cl- uptake displayed Michaelis-Menten kinetics. The affinity constant (Km) for Na+ uptake was typical of intact fish during both Ringer and blood perfusion, whereas Km for Cl- uptake was abnormally high in both cases. The results are discussed with reference to the suitability of the perfused trout head preparation for studying gill ionic fluxes in vitro.

Animals↗
PubMed1980

Fish gill carbonic anhydrase: acid-base regulation or salt transport?

During the passage of blood through the fish gill, large oscillations in oxygen and carbon dioxide content occur. Although the increase in oxygen content is related to oxygen binding by red blood cells, the fall in carbon dioxide content is independent of red blood cells and their complement of carbonic anhydrase. This loss of venous carbon dioxide content is primarily the result of the movement of plasma bicarbonate into the gill epithelium, where it subsequently can be converted to molecular carbon dioxide by branchial carbonic anhydrase. The ultimate control of the bicarbonate flux and hence plasma hydrogen ion regulation is coupled to salt movements also occurring in the fish gill. This evidence in conjunction with carbonic anhydrase localization studies makes it possible to formulate a model capable of explaining acid-base regulation as well as salt transport in freshwater- or seawater-adapted fish. In light of this model the role of the "chloride cell" is discussed.

Acid-Base Equilibrium↗
PubMed1978

Quantitative anatomy of the lungs of the red-eared turtle, Pseudemys scripta elegans.

Morphometric and sterological methods were employed to evaluate the anatomical gas-exchange potential of the lungs of the fresh-water turtle, Pseudemys scripta elegans. The total lung volume and lung wet weight increase with the 1.4 power of body weight. Right and left lungs are similar in size and shape, containing a tissue-free central lumen, which occupies 55 per cent of the maximally inflated lung. The remainder is parenchyma, composed of 90 per cent air and 10 per cent tissue, with an effective surface-to-volume ratio of 18 cm-1. The anatomical diffusion factor (ADF), or the ratio of respiratory surface area to mean diffusion distance in lung tissue, is 1 order of magnitude lower than in the mammalian lung. Taking interspecific differences in O2 consumption into account, the degree to which the lungs are exploited, deltaPtO2, is similar in Pseudemys and in mammals at basal, resting and exercising states.

Animals↗
PubMed1978

Lung architecture volume and static mechanics in five species of lizards.

Compared with mammals, lizards have large, highly compliant lungs and a compliant body wall. High lung compliance is not necessarily associated with high body wall compliance but rather with the degree of development of the caudal and ventral dilatations of the lung. Comparison of the midinflation distance between inflation and deflation curves on standard volume--pressure diagrams indicates hysteresis may have an intrapulmonary component related to the degree of lung partitioning and an extrapulmonary component, attributable to forces hindering the free movement of the lung in the body cavity. Simultaneous consideration of lung structure, mechanical properties and certain nonrespiratory functions such as buoyancy and display indicate that the function of the lung in gas exchange may be only one of several factors important in determining lung structure in lizards.

Animals↗
PubMed1976

Morphometric study of trout gills: a light-microscopic method suitable for the evaluation of pollutant action.

1. Methods are described for the morphometric estimation of parameters of the gill system of trout which are relevant to its function in gas exchange. The methods have been used with 1 mum sections viewed under the light microscope. 2. In particular the diffusion distances between water and blood are measured, which together with determinations of gill area, provide figures for the morphometrically estimated diffusing capacity. 3. The methods have been used to compare the diffusing capacity of gills from control fish and those treated in polluted waters. The concept of relative diffusing capacity (Drel) is introduced which enables comparisons to be made without the need to determine the absolute diffusing capacity. 4. Quantitative estimation of changes in relative volumes and surface areas of components of the secondary lamellae were determined, and employed to explain the possible anatomical causes of changes in Drel. 5. It is suggested that these methods can be of value in the comparison of the gills of fish treated in different waters.

Animals↗