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  • 1
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Median volumes ofin vitro coelomocyte populations fromGlycera dibranchiata rapidly change in response to external differences of osmotic pressure (Fig. 3). Fifty per cent haemolysis occurred in just under 30% sea water, 285 mOSm·kg−1. Hydraulic conductivities (Lp=0.92 to 2.78×107 cm×s−1·atm−1) calculated from rates of osmotic swelling were similar to values for sea urchin eggs and squid axons. Coelomocytes show a slower partial return to their original volumes in hypotonic but not hypertonic media. This asymmetry is reflected in Ponder's R values of 0.787 and 0.987, respectively, determined after this regulatory phase is complete (Figs. 4 and 5). Evidence for an irreversible stress dependent leakage of osmotically active solutes when the coelomocytes are removed from the animal and diluted with sea water is presented.
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  • 2
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Freshwater eel gills are notorious for their limited ability to pump chloride. As a result there is a considerable discrepancy between the Na+ and Cl− plasma levels, and plasma HCO3 − and blood pH are relatively high in this species. When eels are kept in tanks aerated with pure oxygen, significant alterations in blood acid-base balance, an increase in plasma pCO2 and a decrease in blood pH, are observed. In fish studied after 3 weeks hyperoxia, the decrease in blood pH is compensated by an increase in plasma HCO3 −. Such fish exhibit a Cl− influx 5 times higher than that observed in normoxic fish. This Cl− influx is readily inhibited by addition of SCN− to the external medium. An anion-stimulated ATPase activated by HCO3 − and by Cl− and inhibited by SCN− was recently described in membrane fractions of the gills ofCarassius auratus, a fish noted for its high Cl− pumping rate. This enzyme is also found in the gills of the eel. While the maximal rates of enzyme activation by HCO3 − and by Cl− are similar inCarassius andAnguilla, the affinity of the enzyme for Cl− is 25 times higher inCarassius. In the microsomal fraction of the hyperoxic eel gills, the maximal anionstimulated ATPase activity remains unchanged but HCO3 − affinity decreases by 50%, while Cl− affinity increases 5 times. Thus some characteristics of this ATPase seem to be closely related to the Cl− pump activity exhibited by the gill in fresh water.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 117 (1977), S. 358-358 
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
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  • 4
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary With cells which have been grown at 20°C, the circadian rhythm of bioluminescence inGonyaulax polyedra disappears at a critical temperature, which is about 12°C. The transition from the rhythmic to the arrhythmic state is very sharp with temperature: the two states are separated by only 1–2°C. Following a return to a higher temperature (20°C) under otherwise constant conditions, the rhythm resumes with its new phase defined by the time of the cool to warm transition. Loss of rhythmicity also occurs in constant bright light, with a similar resumption and phase determination upon transfer to darkness. The experiments described here show that the effects of light and low temperature are additive: rhythmicity is lost under combined low temperature and light intensity treatments which are ineffective individually.
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  • 5
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Simultaneous measurements have been made of the efflux rates of tritiated water and radiosodium from the lung-fishProtopterus annectens under conditions in which the fish can either use its gills, its lungs or both for respiration. Tritiated water efflux rate was similar (43–44% h−1) when the fish was in oxygenated water with or without access to air but decreased slightly in deoxygenated water. An efflux rate constant of 44% h−1 obtained in oxygenated water is similar to those of other inactive fish in fresh water. The efflux rate constant for sodium was 0.84% h−1 and total sodium flux was comparable to that of fresh-water fish. The decrease in both tritiated water and sodium efflux rates in deoxygenated water are explained in terms of diversion of blood flow away from the functional gills to the lungs. Oxygen consumption was highest (38.7 ml kg−1 h−1) in deoxygenated water and lowest when the fish was out of water. Despite the reduced functional significance of the gill for respiration, it is still as permeable to water and electrolytes as that of fresh-water teleosts.
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  • 6
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. The rates of oxygen consumption ( $$\dot V_{{\text{O}}_2 } $$ ) of individual crabs varied with their live mass. Mean $$\dot V_{{\text{O}}_2 } $$ increased with acclimation temperature in 100% seawater (Q10 2.36) but not in 50% seawater. 2. Exposure to 50% seawater caused a significant increase in $$\dot V_{{\text{O}}_2 } $$ to twice the rate in 100% seawater at 10°C. There was no significant increase in $$\dot V_{{\text{O}}_2 } $$ on dilution at 18°C (Fig. 5). 3. Heart rate, ventilation volume ( $$\dot V$$ ) and a-VO 2 content difference were unaffected by dilution. The rise in $$\dot V_{{\text{O}}_2 } $$ , following dilution at 10°C may, as far as the cardiovascular system is concerned, arise from an increase in cardiac stroke volume. 4. Crabs were isosmotic with 100% seawater at 10°C, 14°C and 18°C. In 50% seawater all crabs showed a significant reduction in blood osmolarity, though they maintained the ΔF.p. and Na+ concentration significantly above that of the medium. Crabs acclimated to 10°C maintained a significantly higher blood ΔF.p. and Na+ concentration in 50% seawater than crabs at 18°C (Fig. 6). 5. Crabs acclimated to 10°C were significantly more active after exposure to 50% seawater. There was no significant change in activity, following dilution, in crabs at 18°C (Fig. 7). 6. The variations in $$\dot V_{{\text{O}}_2 } $$ with temperature and salinity seem to relate to the measured changes in patterns of osmoregulation and activity. At 10°CCarcinus osmoregulates more effectively than at 18°C and is hyperactive in low salinities, which may represent an avoidance reaction. At 18°C, the summer temperature, the crab tolerates internal dilution and is relatively quiescent.
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  • 7
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Previous workers have (a) compared pulmonate crop juice and digestive gland extracts and found a close similarity in the enzymic complements from these two sources, and (b) located specific enzymes within the various cell types of the digestive gland. The digestive gland seems to be the major source of extracellular enzymes but what is not clear is which of the enzymes associated with particular intracellular structures are actively secreted into the crop juice. The present study has used polyacrylamide disc gel electrophoresis to investigate the digestive gland and crop juice esterases ofCepaea nemoralis andC. hortensis. It appears that only some of the digestive gland esterases are specifically secreted. The variation shown in crop juice esterases suggests three independent sources in the digestive gland. Less detailed studies ofHelix aspersa andArianta arbustorum also indicate multiple sources of extracellular esterases.
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  • 8
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. TheP IO2 at which crabs emerged from shallow seawater during progressive hypoxia (Table 1), as well as theP c levels for $$\dot V_{O_2 }$$ (Fig. 2) and $$\dot V_g $$ (Fig. 4) of submerged crabs, increased with acclimation temperature and following exposure to 50% seawater at low temperatures (Fig. 6). This pattern of variation resembles the changes in relative oxygen demand with temperature and salinity. 2. TheP c levels for heart rate increased with acclimation temperature but were unaffected by dilution (Fig. 6). 3. Percentage extraction of oxygen from the respired water (Table 2) as well as the levels of motor activity (Fig. 5) were not affected by exposure to hypoxia. 4. Lactic acid concentration in the blood of submerged crabs increased markedly during hypoxia and there was an enhanced $$\dot V_{O_2 }$$ on recovery in normoxia (Fig. 2), which apparently served to completely repay an accumulated oxygen debt. 5. It was concluded that when exposed to environmental hypoxiaCarcinus can adopt the alternative strategies of either accumulating an oxygen debt when in deep water or emerging into air from shallow water to aerate the branchial chambers.
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  • 9
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary ThepO2 in the hemolymph of the decapod crustaceanAstacus leptodactylus was measured continuously with micro O2 electrodes. PostbranchialpO2, heart rate and ventilation rate were simultaneously recorded. PrebranchialpO2 was measured in a separate series of experiments. Crayfish acclimated for six weeks to warm (20 °C) and cold (10 °C) conditions were studied. 1. Postbranchial bloodpO2 was measured in the pericardium. Typical values for warm-acclimated animals fell in the range 23–35 Torr, with a mean of 28.3 Torr, and those for cold-acclimated animals were 17–30 Torr, with a mean of 24.4 Torr. PrebranchialpO2 was measured in the meropodites of the 8th thoracopod. VenouspO2 levels ranged from 7–13 Torr, mean 9.4 Torr (warm-acclimated), and 6–9 Torr, mean 6.8 Torr (cold-acclimated). 2. pO2 values of resting, restrained animals were variable and fluctuations occurred in both the pre- and the postbranchial levels. Fluctuations were either small (1–5 Torr) or large (10–70 Torr). 3. PostbranchialpO2 correlated with fluctuations in the ventilation and heart rates. ArterialpO2 rose when the ventilation rate was increased, with a delay of about 10 s in warm-acclimated and 20 s in cold-acclimated animals, respectively. Along with increasingp aO2 an increase of the heart rate was established. 4. In resting animals, there is no a-v pH-difference. Cell-free hemolymph, taken from the pericardium or the meropodites, had a pH of 7.48 or 7.47, respectively, in warm-acclimated animals and 7.94 or 7.97 in cold-acclimated animals. Under these conditions the hemocyanin was 99% saturated in the artial blood and 45% in venous (warm-acclimated). Corresponding values in cold-acclimated crayfish were 98% and 61%, respectively. 5. TheP 50 of the hemocyanin in undiluted hemolymph was 10 Torr at 20 °C and pH 7.42, and 6.2 Torr at 10 °C and pH 7.92. The hemocyanin showed a weak Bohr effect (ΔlogP 50/ΔpH=−0.19 in warm-acclimated, and −0.20 in cold-acclimated animals). The pH range of the Bohr effect fell into the in vivo pH range in each group and thus differed by 0.5 pH units between the two groups.
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  • 10
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fresh-water limpetAncylus fluviatilis, living in European brooks, was found to have relatively greater carbohydrate and lipid fractions in winter than in summer. During starvation in the winter stage, lipid reserves are diminished first, followed by the carbohydrate reserves. Protein is degraded at nearly equal rates throughout the experiments. Specimens suffering from starvation are not found in the field during winter. Lipid reserves are mainly deposited in the midgut gland, whereas the carbohydrate reserves are distributed more equally among different tissues.A. fluviatilis must feed continuously during the winter period. The results are discussed in relation to data from other Basommatophora.
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