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Haemolymph oxygen transport and acid-base status in Glyptonotus antarcticus Eights (1997)

Whiteley, N. M. ; Taylor, E. W. ; Clarke, A. ; [et al.]

Springer

Polar biology 18 (1997), S. 10-15

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ISSN: 1432-2056

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Haemolymph samples were withdrawn from routinely active male intermoult Glyptonotus held at 0 ± 0.5°C, and analysed for blood-gas and acid-base variables. In both the arterialised (a) and venous (v) haemolymph, over 50% of the oxygen was transported as dissolved oxygen at PaO2 and PvO2 levels of 12.0 ± 1.15 and 7.70 ± 1.89 kPa, respectively. The maximum oxygen-carrying capacity of the haemocyanin (CmaxHcO2) was relatively low at 0.19 ± 0.05 mmol l−1, accompanied by relatively low protein and [Cu2+] levels indicating low circulating haemocyanin concentrations. Arterialised haemolymph had a mean pH of 7.88 ± 0.02(6) at a PCO2 of 0.12 ± 0.01(6) kPa and a bicarbonate level of 12.95 ± 0.80(6) mequiv l−1 with small differences in PCO2 and pH between arterial and venous haemolymph. The non-bicarbonate buffering capacity of Glyptonotus haemolymph was low at −2.0 mequiv l−1 HCO3 − pH unit−1. Haemolymph [l-lactate] and [d-glucose] levels were similar at 〈 1 mmol l−1 in animals held in the laboratory and those sampled in Antarctica. The blood-gas and acid-base status of Glyptonotus haemolymph may be a reflection of the low and stable temperatures experienced by this Antarctic crustacean.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s003000050153

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The respiratory and cardiovascular changes associated with the emersion response ofCarcinus maenas (L.) during environmental hypoxia, at three different temperatures (1973)

Taylor, E. W. ; Butler, P. J. ; Sherlock, P. J.

Springer

Journal of comparative physiology 86 (1973), S. 95-115

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ISSN: 1432-1351

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Summary 1. When exposed to progressive hypoxia in shallow seawater,Carcinus maenas partially emerged into air and aerated its branchial chambers by reversing the direction of their irrigation. Emersion took place at a meanP I, O2 of 18 mm Hg at 6 °C, 21 mm Hg at 12 °C and 59 mm Hg at 17 °C. 2. At low oxygen tensions submerged crabs underwent a progressive bradycardia. Heart rate first became significantly lower than the rate in normoxia below aP I O2 of 30 mm Hg at 6 °C, 40 mm Hg at 12 °C and below 60 mm Hg at 17 °C. The proportion of total time spent irrigating the gills in a reversed direction increased in hypoxic seawater (P I, O2〈 50 mm Hg), but respiratory rate was unchanged. 3. Emersion into air always occurred during a reversal of irrigation and was accompanied by prolonged reversals, with consequent aeration of the branchial chambers, and by an immediate and maintained tachycardia back towards the rate in normoxic seawater. Crabs emerging into a hypoxic atmosphere ( $$P_{O_2 } $$ 〈 10mm Hg) showed neither a maintained reversal of irrigation nor a maintained tachycardia. 4. The oxygen tension of the postbranchial blood (P a,O2) was 94 mm Hg in crabs submerged in normoxic seawater (P I,O2 146 mm Hg) at 12 ° C. During progressive hypoxiaP a, O2 fell in direct proportion to the drop inP I,O2. Emersion caused no significant increase inP a, O2. 5. The mean oxygen content of postbranchial blood (C a, O2) was 0.96 vol. % at aP I,O2 of 145 mm Hg.C a, O2 fell to 0.19 vol.-% in submerged crabs at a meanP I,O2 of 25 mm Hg but rose to 0.45 vol.-% following 10 min emersion into air at a meanP I, O2 of 22 mm Hg. 6. The results provide evidence of a respiratory role for the emersion response and also of an adaptive role for the high affinity of the blood pigment inCarcinus.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00702531

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Observations of valve-like structures and evidence for rectification of flow within the gill lamellae of the crab Carcinus maenas (Crustacea, Decapoda) (1986)

Taylor, H. H. ; Taylor, E. W.

Springer

Zoomorphology 106 (1986), S. 1-11

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ISSN: 1432-234X

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary The isolated gills of Carcinus maenas, perfused at pressure drops of 1–10 cm of water, exhibited flow rectification, the resistance to perfusion via the afferent vessel being many times lower than that for efferent perfusion. The asymmetry was greater at the lower end of this pressure range. The overall afferent branchial resistance for Carcinus of weight 65 g, and with no ventilatory component in the transmural pressure difference, was estimated to be 0.05 cm of water. μl−1 · sec. The corresponding overall reverse (efferent) branchial resistance was 0.36 cm of water · μl−1 · sec. LM, TEM and SEM examination of the gills indicated that haemolymph leaves each gill lamella via several discrete parallel efferent channels which drain different regions of the lamella, and that each efferent channel is nearly closed, at its junction with the efferent branchial vessel, by a diaphragm of loosely interwoven and very elongated cells. It is concluded that these cells may constitute efferent valves and that narrow apertures between them may contribute a major component to the branchial resistance and be primarily responsible for the rectification of flow. Relatively wide apertures lead directly from the afferent vessel into the lamellae and are not asociated with valves of any kind. The valves may be important in enabling changes in transmural pressure associated with ventilatory reversals to pump haemolymph unidirectionally through the lamellae. Similarly valves may allow the oscillating venous pressures associated with locomotor activity to improve gill perfusion during exercise. The elongated tails of the cells of the efferent valve contain numerous microtubules. The wider cell bodies contain the nucleus and many mitochondria. Unusual organelles composed of many short (about 0.25 μm long) microtubules and often lying close to the nuclear membrane may be microtubule organising centres. It is speculated that, in addition to their simple mechanical function, the valve cells may play a more dynamic role in regulating flow of haemolymph through different lamellar routes, or that they may monitor composition, pressure or flow of the efferent lamellar circulation.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00311941

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Effects of diet on spontaneous locomotor activity and oxygen consumption in Adriatic sturgeon (Acipenser naccarii) (1995)

McKenzie, D. J. ; Piraccini, G. ; Steffensen, J. F. ; [et al.]

Springer

Fish physiology and biochemistry 14 (1995), S. 341-355

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ISSN: 1573-5168

Keywords: diet ; fish ; hypoxia ; O2 uptake ; spontaneous locomotor activity ; sturgeon ; ω3 fatty acids ; vitamin E

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Adriatic sturgeon (Acipenser naccarii) were maintained on a commercial diet enriched either in long chain polyunsaturated fatty acids of the ω3 series (ω3 LCPUFA) or in saturated fatty acids (SFA). The effects of dietary fatty acid composition on spontaneous locomotor activity in normoxia and hypoxia (O2 tension = 10.5 ± 0.8 kPa), and on oxygen consumption (MO 2) in normoxia, in hypoxia (O2 tension = 6.6 ± 0.8 kPa) and during recovery were then investigated. The effects of adding supplementary vitamin E to the fat-enriched diets were also studied. Dietary fatty acid composition had effects on spontaneous locomotor activity and MO 2 in normoxia. Activity levels were higher in all sturgeon fed extra dietary fats (without vitamin E), when compared with control animals, but fish fed ω3 LCPUFA had a significantly lower MO 2 than those fed SFA, with intermediate MO 2 in controls. In hypoxia, sturgeon ω3 LCPUFA did not alter activity or MO 2 whereas those fed SFA reduced both and controls reduced MO 2. During recovery, both animals fed SFA and controls had a higher MO 2 than sturgeon fed ω3 LCPUFA. The data indicate that fish fed ω3 LCPUFA are more tolerant of hypoxia than controls or those fed SFA, as they did not reduce either activity or MO 2, and consumed less O2 during recovery. Vitamin E supplements modified the effects elicited by dietary fats. All sturgeon fed vitamin E had low activity levels in normoxia and hypoxia. Sturgeon fed vitamin E with ω3 LCPUFA had a higher MO 2 in normoxia than those fed ω3 LCPUFA alone; reduced MO 2 in hypoxia, and during recovery increased MO 2 to a rate higher than that of animals fed ω3 LCPUFA alone. In normoxia, sturgeon fed vitamin E with SFA had a similar MO 2 to those fed SFA alone but did not change MO 2 in hypoxia or during recovery. Thus, the effects of vitamin E were dependent on fat composition of the diet. Vitamin E with ω3 LCPUFA removed the beneficial effects on MO 2 and responses to hypoxia obtained with ω3 LCPUFA alone, but vitamin E with SFA allowed sturgeon to maintain aerobic metabolism in hypoxia, a more effective response than that observed in fish fed SFA alone.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00003373

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5

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Evidence of a role for catecholamines in the control of breathing in fish (1991)

Randall, David J. ; Taylor, E. W.

Springer

Reviews in fish biology and fisheries 1 (1991), S. 139-157

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ISSN: 1573-5184

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Summary Our current knowledge of the control of ventilation in fish is incomplete at all levels. The respiratory rhythm originates in a medullary central pattern generator (CPG), which has yet to be clearly identified and characterized. Its activity is directly modulated by inputs from elsewhere in the CNS and from peripheral mechanoreceptors. The central location of respiratory motoneurones, innervating the various respiratory muscles, has been described in detail for some fish, particularly elasmobranchs. We are still unclear, however, about the link between the CPG and the sequential firing of the motoneurones, which result in coordinated contractions of the respiratory muscles, and about the mechanisms that result in recruitment of feeding muscles into forced ventilation. In teleosts, ventilation is matched to oxygen requirements by stimulation of gill chemoreceptors, which seem to respond to oxygen content or supply. There is little evidence of a role for these receptors in elasmobranchs. Chemoreceptor stimulation evokes a number of reflex changes in the respiratory and cardiovascular systems of fish that are rapid in onset and seem adaptive (e.g. increased ventilation and a bradycardia in response to hypoxia). Conditions that result in hypoxaemia and the consequent ventilatory changes also cause an elevation in circulating catecholamine levels. We have explored the possibility of a causal relationship between these levels and the ventilatory response. Strong evidence for this relationship arises from experiments on hypoxia and acid infusion, which trigger a ventilatory increase and a rise in circulating catecholamines. Both ventilatory responses are blocked by an injection of propranolol, indicating that β adrenoreceptors are involved in the response. The ventilatory response to hypoxia, in teleosts at least, occurs very rapidly, perhaps before any marked increase in circulating catecholamines and almost certainly before any blood-borne catecholamines could reach the respiratory neurones. This argues for an immediate neuronal reflex based on chemoreceptors in the gill region responding to hypoxia. Clearly, circulating catecholamines also affect ventilation through some action in the medulla and could act in concert with a direct neuronal chemoreceptive drive during hypoxia. The studies on acid infusion during hyperoxia, where there is an acidosis but no increase in ventilation or blood catecholamines, would argue against any hydrogen ion receptor, either peripheral or central, being involved in the reflex ventilatory response to acidotic conditions in fish. The release of catecholamines into the circulation, therefore, seems to be an absolute requirement for the ventilatory response to acidosis in fish. Present evidence supports a role for β-adrenergic receptors on respiratory neurones, stimulated by changes in the levels of circulating catecholamines, in the control of ventilatory responses to marked changes in oxygen availability in fish, such as those occurring in the post-exercise acidotic state.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00157582

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6

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A transposition of the reverse transcriptase gene reveals unexpected structural homology to E. coli DNA polymerase I (1991)

Taylor, E. W. ; Jaakkola, J.

Springer

Genetica 84 (1991), S. 77-86

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ISSN: 1573-6857

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The rational design of antiviral agents targeting the reverse transcriptase (RT) of the human immunodeficiency virus (HIV) would greatly benefit from a more intimate knowledge of the structure of RT. Until now, the degree of sequence similarity between RT and E. coli DNA polymerase I (Pol I) has been thought to be confined to several small regions, suggesting little basis for homology molecular modeling. However, we have found that a region in the C terminal of the RT polymerase domain is homologous to a central region of Pol I that lies between the universal polymerase motifs A and C (specifically, helices N-O-P of the Pol I crystal structure); a single transposition closely aligns the RT and Pol I genes, revealing a similar domain structure with 20% residue identity, as well as the possible structural correlates of several RNA-dependent polymerase motifs. The RT from Myxococcus xanthus (a bacterium believed to have diverged from other species 2 billion years ago), if similarly transposed, shows homology to both HIV-1 and E. coli, suggesting the possibility of a very ancient divergence between the RT and Pol I polymerase genes. A second even more significant match to this E. coli region was found in the retroviral ribonuclease H (RNase H) domain, and corresponds precisely to a region that has been aligned by previous investigators with the E. coli RNase H, suggesting that Pol I helices O and P are homologous to helices A and D of the RNase H crystal structure, respectively. These results are consistent with a modular theory of molecular evolution.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00116546

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7

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Kinetic studies of normal and modified heavy meromyosin and subfragment-1 (1981)

Sleep, J. A. ; Trybus, K. M. ; Johnson, K. A. ; [et al.]

Springer

Journal of muscle research and cell motility 2 (1981), S. 373-399

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ISSN: 1573-2657

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Summary The kinetic behaviour of heavy meromyosin (HMM) and subfragment-1 (S-1) has been compared for a range of pH and temperature for normal and SH-1 modified proteins. No significant differences were found between S-1 and HMM and the evidence is consistent with an identical independent site mechanism of the form first proposed by Bagshaw and Trentham: $$\begin{gathered} M + ATP\mathop { \leftharpoondown \rightharpoonup }\limits^{K_1 } M.ATP \mathop { \leftharpoondown \rightharpoonup }\limits^{k_2 } M.ATP^* \mathop { \leftharpoondown \rightharpoonup }\limits^{k_3 } M.Pr^{**} \mathop {\mathop { \leftharpoondown \rightharpoonup }\limits_{H^ + ,P_i } }\limits^{k_4 } \hfill \\ M.ADP^* \mathop { \leftharpoondown \rightharpoonup }\limits^{k_5 } M.ADP \mathop { \leftharpoondown \rightharpoonup }\limits^{K_6 } M + ADP \hfill \\ \end{gathered} $$ where asterisks refer to states of enhanced tryptophan fluorescence and a M.Pr is a state in which both products are bound.k 3 andk 5 had a large temperature dependence (Arrhenius activation energy approximately 100 kJ mol−1).k 3 andk 5 increased with increasing pH and the variation fitted a titration curve with pK of 7.4. The rate of step 4 was measured by decay of tryptophan fluorescence, proton release and phosphate release measured as an increase in conductance. The temperature dependence curves fork 4 andk 5 cross over at 11–13° C for Mn2+-ATPase, 3–5° C for SH-1 modified Mg2+-ATPase and below 0° C for normal Mg2+-ATPase. A change of the rate-determining step fromk 4 tok 5 accounts for the nonlinear Arrhenius plots of Mn2+-ATPase and SH-1 modified Mg2+-ATPase. Modification also reduced the rate of the hydrolytic stepk 3 measured by the maximum rate of the phosphate early burst. The two fluorescence transitions (steps 2 and 3) are easily resolved for the modified enzyme andk 3 measured by fluorescence was equal to the rate of hydrolysis obtained from phosphate measurements.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00711966

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Some responses of the shore crab,Carcinus maenas (L.) to progressive hypoxia at different acclimation temperatures and salinities (1977)

Taylor, E. W. ; Butler, P. J. ; Al-Wassia, A.

Springer

Journal of comparative physiology 122 (1977), S. 391-402

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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.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00692524

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The behaviour and respiratory physiology of the shore crab,Carcinus maenas (L.) at moderately high temperatures (1979)

Taylor, E. W. ; Wheatly, Michèle G.

Springer

Journal of comparative physiology 130 (1979), S. 309-316

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ISSN: 1432-136X

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Summary 1. When gradually warmed from either 15 °C or 25 °CCarcinus voluntarily migrated into air at a mean temperature of 28 °C. Once in air, each crab remained there for the duration of the experiment (3 h). This behaviour was termed “emigration”. 2. Emigration into cool air (17 °C) served to lower body temperature and heart rate was proportionally decreased, whilst emigration into warm air (26 °C) caused no marked reduction in body temperature and heart rate was unaffected (Fig. 2). 3. The $$\dot V_{O_2 } $$ of crabs in dry air (R.H. 40%) was significantly lower than that of crabs in damp air (R.H. 80%) at 30 °C, due to a significant mean difference in body temperature of 1.8 °C (Fig. 3). 4. Exposure to air (R.H. 55%) for 12 h caused a progressive reduction in mass accompanied by a proportional increase in haemolymph Na+ concentration (Table 1). 5. 3 h exposure to air at 25 °C caused a marked increase in CO2 tension ( $$Pa_{CO_2 } $$ ) and content ( $$Ca_{CO_2 } $$ ) in the haemolymph accompanied by a reduced pH, which caused a Bohr shift. The oxygen content of the postbranchial haemolymph ( $$Ca_{O_2 } $$ ) was maintained high in air (Table 2). 6. The advantage of emigration may be the potential cooling effect of aerial exposure, with a consequent reduction in oxygen demand, as well as the avoidance of the possibility of low availability of oxygen in small bodies of warmed seawater.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00689848

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The effect of long term, moderate hypoxia on acid-base balance, plasma catecholamines and possible anaerobic end products in the unrestrained dogfishScyliorhinus canicula (1979)

Butler, P. J. ; Taylor, E. W. ; Davison, W.

Springer

Journal of comparative physiology 132 (1979), S. 297-303

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ISSN: 1432-136X

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Summary 1. The first afferent branchial blood vessel of dogfish was cannulated and the animals were allowed 24 h to recover from the operation. Control animals were then left for 3 days in normoxic sea water, while experimental fish were exposed to hypoxic sea water ( $$P_{O_2 }$$ 55 mmHg) for 3 days. It was not possible to keep the fish for this period of time at an environmental $$P_{O_2 }$$ below 50 mmHg. 2. In the control animals, there was a significant (24%) reduction in haematocrit during the 3 day period of normoxia. There was a significant increase in the concentration of bicarbonate ions [HCO 3 − ] which, together with a slight increase in $$pH\bar v$$ , indicates a metabolic alkalosis following a decrease in the concentration of plasma lactate and the lactate/pyruvate ratio. There were no significant changes in any of the other measured variables. 3. In the experimental fish, there was no significant change in Hct during the 3 day period of hypoxia. There was, therefore, a potentialincrease in Hct during this period (cf. change in control fish). Heart rate declined initially, but then recovered to a value which was close to the normoxic rate. There was an increase in $$pH\bar v$$ , while [HCO 3 − ] and $$P\bar v_{CO_2 }$$ decreased. Plasma lactate and the lactate/pyruvate ratio increased and it was deduced that there was a combination of a respiratory alkalosis with a metabolic acidosis. The only catecholamine to increase significantly was noradrenaline. 4. The failure of dogfish to survive prolonged exposure to more severe hypoxia ( $$P_{O_2 }$$ 〈50 mmHg) is probably related to their inability to increase oxygen transport by large increases in ventilation volume or by reducing theP 50 of their hemoglobin. Anaerobiosis and severe acidosis then occur.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00799042

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