Comparative Biochemistry and Physiology Part A: Physiology最新文献

Among piscine taxa, the Antarctic icefishes (family Channichthyidae) prosper in the absence of erythrocytes and hemoglobin, a unique condition among adult vertebrates. The genomes of three icefish species and four red-blooded notothenioid species were probed using α- and β-globin cDNA from the red-blooded Antarctic fish Notothenia coriiceps. High-stringency hybridization signals with the α-globin probe, but none with the β-globin probe, on genomic DNAs of both hemoglobinless and red-blooded fishes suggest that icefishes retain remnants of α-globin genes in their genomes but have lost the gene that encodes for β-globin, either through deletion or through rapid mutation. Northern blot analysis of major hematopoietic and non-hematopoietic tissues shows that the α-globin-related sequences of icefishes are nonexpressed derivatives of the α-globin genes of their red-blooded relatives. Mechanisms leading to the hemoglobinless phenotype are discussed in relation with the expression of myoglobin in the Channichthyidae family.

Although freshwater turtles as a group are highly anoxia tolerant, dramatic interspecific differences in the degree of anoxia tolerance have been demonstrated in vivo. Painted turtles (Chrysemys picta bellii) appear to be the most hypoxia-tolerant species thus far studied, while softshelled turtles (Trionyx spinifer) are the most hypoxia-sensitive. We have assumed that this dichotomy persists in vitro but have not, until now, directly tested this assumption. We, therefore, directly compared the responses of isolated, perfused, working hearts from these two species to either 240 min of anoxia, 90 min of global ischemia, or 240 min of global ischemia followed by reoxygenation/reperfusion. Isolated hearts were perfused at 20°C and monitored continuously for phosphocreatine (PCr), adenosine triphosphate (ATP), inorganic phosphate (P₁), and intracellular pH (pH₁) by ³¹P-nuclear magnetic resonance spectroscopy as well as for ventricular developed pressure and heart rate. Contrary to our expectations, we observed few significant differences in any of these parameters between painted and softshelled turtle hearts. Hearts from both species tolerated 240 min of anoxia equally well and both restored PCr, pH₁, and P₁ contents to control levels during reoxygenation. We did observe some significant interspecific differences in the 90 min (pH₁ and P₁) and 240 min (PCr) ischemia protocols although these seemed to suggest that Trionyx hearts might be more tolerant to these stresses than Chrysemys hearts. We conclude that: (a) the observed in vivo differences in anoxia tolerance between painted and softshelled turtles must either be due to differences in organ metabolism in organs other than the heart (e.g., brain) or to some integrative physiologic differences between the species; and (b) isolated hearts from a species known to be relatively anoxia sensitive in vivo can exhibit an apparent high degree of anoxia and ischemia tolerance in vitro.

The focus of the presentation will review the distribution of nitric oxide (NO)-producing sites in the digestive system in mammals and nonmammalian vertebrates and will center on the roles that NO plays in modulating physiological and pathophysiological functions in digestive system.

The presence of vasoactive peptides known to control cardiovascular functions in mammals and sub-mammalian vertebrates was investigated in the sub-Antarctic icefish Champsocephalus gunnari. Western immuno blotting was used to demonstrate immunoreactive atrial natriuretic peptide (ANP), angiotensin II (Ang II), bradykinin (BK) and endothelin-1 (ET-1) in heart homogenates. Immunohistochemistry was used to investigate the distribution of ANP, Ang II, BK and ET-1 in the cardiocytes of the three chambers of the heart (atrium, ventricle and the very short conus arteriosus).

The degree of ovarian maturation and the specific activities in hepatopancreas and stomach of amylase, trypsin, chymotrypsin, carboxypeptidase A and B and leucine aminopeptidase were determined at different stages of the moulting cycle of wild female pink shrimp Penaeus notialis. Ovarian maturation appeared from intermoult stage C₁–C₂ to early premoult stage D₁. The highest values for amylase in stomach and hepatopancreas ocurred at stages D₁ and B₂ to C₃–C₄, respectively. Total proteolytic activity in the hepatopancreas was highest in stages B₂ to C₃–C₄, and in the stomach the highest value was observed in D₁. For the endopeptidases, the highest value was for trypsin TAME in stomach during stage D₁ and in the hepatopancreas at stage C₁–C₂. The exopeptidases showed peaks in hepatopancreas in stages C₁–C₂ and C₃–C₄. Leucine aminopeptidase showed the lowest proteolytic values and peaks in stomach were observed at stages C₃–C₄ and D₂.

Experiments were conducted to determine if adiposity affected feed intake in juvenile chinook salmon (Oncorhynchus tshawytscha) with different nutritional histories. Fry were fed high-fat (23%) or low-fat (3%) diets at high (satiation) and low (one-half satiation) ration levels for 7 months before the start of the intake experiment. This pre-treatment produced fish averaging 22 g with 11.3% (high-fat diet) and 5.4% (low-fat diet) body fat when fed to satiation or 11 g with 7.0% (high-fat diet) and 3.3% (low-fat diet) body fat when fed at one-half satiation. Experiment 1 had a 2 × 2 factorial design where duplicate groups of 20 fish from the high-ration groups (22 g) were fed high- (16%) or low- (4%) fat diets twice daily to satiation 6 days/wk for 3 weeks. Daily feed intake was recorded. The same protocol was used in experiment 2 on fish (40 fish per tank) from the smaller low-ration groups (11 g). Feed intakes on day 1, cumulative feed intakes after 21 days and plasma levels of insulin and insulin-like growth factor 1 (IGF-1) were compared using two-way ANOVA with initial whole body fat and dietary fat as the independent variables. In both experiments, high body fat led to significantly lower feed intake on day 1 and after 21 days of feeding. High dietary fat levels caused greater intake on day 1, but by the end of the experiments, this effect was not significant, suggesting some adaptation to the diets. Insulin in plasma showed greater response to dietary fat (high-fat diets causing higher insulin levels), whereas IGF-1 responded more to body fat level (high body fat led to higher IGF-1 levels). Our results show that in both-fast- and slow-growing juvenile chinook salmon, adiposity plays a role in regulation of feed intake and that adiposity appears to interact with IGF-1. Dietary fat levels had transient effects on intake, but plasma insulin levels consistently reflected the dietary fat levels. An important implication of our findings is that food intake, and possibly growth, could be retarded if a feeding regime results in high body fat levels.