Table of Contents of Volume 51 - 2003

Table of Contents

Table of Contents of Volume 51 - 2003     

Biodiversity of Pacific Ocean fishes

Table of Contents

Biodiversity of Pacific Ocean fishes     

Contents

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Genetica

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Genetica

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To be published in the next issue of BioControl

Table of Contents

To be published in the next issue of BioControl     

The isolated, perfused head of the marine teleost fish,Myoxocephalus octodecimspinosus: Hemodynamic effects of epinephrine

Summary An isolated, perfused-head preparation utilizing the marine teleost (Myoxocephalus octodecimspinosus) was developed, and the hemodynamic effects of epinephrine on this preparation were studied.The isolated head of the sculpin was found to have a relatively long-term viability as measured by stable perfusion pressures (±4.03 Torr for the first hour of perfusion) and responsiveness to epinephrine for over three hours (Fig. 1). This catecholamine induced a net decrease in the resistance of the vasculature of the head along with an increase in the dorsal aortic blood flow, and a concomitant decrease in a venous flow from the peritoneal cavity and cut muscle mass (Fig. 2, Table 1). Blocking beta adrenergic receptors during epinephrine application produced an increase in the vascular resistance and the dorsal aortic to venous flow ratio (Table 2); beta receptor stimulation was followed by a decrease in the resistance and no change in efferent flow rates (Table 3).It is concluded that alpha adrenergic receptors induce the constriction of the branchial arterio-venous anastomoses and are responsible for the efferent flow rate changes. However, beta adrenergic receptors, presumably at the level of the lamellar arterioles, appear to be the dominant factor in the control of net branchial resistance.     

The physiology of exercise at and above maximal aerobic capacity in a theraphosid (tarantula) spider,Brachypelma smithi (F.O. Pickard-Cambridge)

Summary The physiology of activity in a large (ca. 30 g) mygalomorph (‘tarantula’) spiderBrachypelma smithi, was investigated for 10 min runs at speeds of 2.0, 2.5, and 5.0 cm/s. No differences in were observed at the different speeds suggesting that maximum steady-state aerobic metabolism was achieved. These, levels were eight times greater than those measured in resting spiders and in agreement with predictions based on estimates of the functional capacity of their book lungs (Table 3). Heart rates increased from 18 to 58 beats/min during activity (Fig. 4) while ventilation rates increased from 10/h to 114/h (Table 2). Changes in heart rates indicate, systemic hemolymph perfusion is maintained during activity in contradiction to reports suggesting circulation is compromised by fluid pressures generated during hydraulic leg extension in these animals. Hemolymphd-lactate concentrations increased ca. nine fold during running at 5 cm/s from a resting concentration of 1.7 mM. Peak values occurred from one to two h after the end of exercise (Fig. 5). Anaerobic contributions during exercise, via lactate production, accounted for no more than 30% of the total ∼P synthesized (Table 4). Lactate removal was slow: four h after activity, concentrations in the hemolymph remained ca. 8.5 mM (Fig. 5). Maximum in spiders are much lower than those in active insects, a difference that reflects the effectiveness of tracheal gas exchange of insects compared with respiratory gas transport book lungs and an open circulatory system found in spiders (Table 5). Direct measurements of body temperatures indicate theraphosids are not endothermic during activity.     

Buffering capacity of vertebrate muscle: Correlations with potentials for anaerobic function

Summary Buffering capacities (), measured in slykes (moles of base required to titrate the pH of one gram wet weight of muscle by one pH unit, over the pH range of pH 6 to pH 7) due to non-bicarbonate buffers were measured in locomotory muscles from a variety of terrestrial and marine mammals and teleost fishes (Tables 1 and 2). The highest buffering capacities were found in muscles capable of either intense, burst glycolytic function or prolonged, low-level anaerobic function. Marine mammals had higher muscle buffering capacity on the average than terrestrial mammals. Among the fishes studied, warm-bodied species had the greatest values of all animals examined (Table 2). Deep-sea fishes and shallow-living fishes with sluggish locomotory abilities had low values. Fish white muscle displayed higher buffering capacity than red muscle (Fig. 1; Table 2), in keeping with the more aerobic poise and higher capillary density of the latter type of muscle. Strong correlations were found between (1) and muscle myoglobin concentrations in the mammalian species (Table 1; Fig. 2), and (2) and muscle lactate dehydrogenase (LDH) activities in both the mammals and the fishes (Tables 1 and 2; Fig. 3). No correlation was found between and the activity of a citric acid cycle indicator enzyme, citrate synthase, in the mammalian species. While strongly correlated with buffering capacity, the amounts of myoglobin and LDH in a muscle are not the principal determinants of . The results indicate that muscle intracellular buffering capacity is especially critical in locomotory muscles which must function under conditions (burst locomotion and prolonged, low-level anaerobic function) where circulatory perfusion is inadequate to rapidly remove the acidic end-products such as lactic acid that are produced by anaerobic glycolysis. In this respect, the locomotory muscle of diving mammals and the white skeletal muscles of teleost fishes face a common acid-base regulatory problem and utilize a common biochemical strategy to resolve it.