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This study was designed to monitor lipid profile in the portal and hepatic blood of cows with fasting-induced hepatic lipidosis, and to compare the results with those in the jugular blood. The work was also carried out to investigate bile acid (BA) in these vessels, and further to investigate BA extraction rate in the liver. Five cows were equipped with catheters in the portal, hepatic and jugular veins (day 0), fasted for 4 days (day 1-day 4) and then refed (day 5-day 11). Before morning feeding, blood was sampled before, during and after fasting from the catheterized vessels. In the portal blood, the concentration of non-esterified fatty acids (NEFA) showed a progressive increase and at day 5 there was an approximate twofold rise. Increased NEFA concentrations were also found similarly in the other two veins. At day 5, beta-hydroxybutyrate (BHBA) in the portal, hepatic and jugular blood rose to 197, 190 and 186% of the pre-fasting value, respectively. However, the concentrations of NEFA and BHBA in the three veins gradually returned to pre-fasting concentration during the refeeding period. Compared with the pre-fasting value at day 0, the content of liver triglyceride (TG) increased significantly at day 5 (P < 0.01). In the liver, the hepatic extraction rate of BA dropped from 3.1 times pre-fasting to 2.2 times during fasting. There were no significant differences in the concentrations of glucose, TG, total cholesterol, cholesterol esters, free cholesterol and phospholipids. The results of the current study show that metabolic alterations occur in the portal, hepatic and jugular veins during induction of hepatic lipidosis in cows, and mostly metabolites, with exception of BA concentration, run parallel. The decreased BA extraction rate in the liver of fasted cows was considered to reflect hepatic cell impairment caused by TG accumulation. Hopefully, the findings, at least in part, contribute to the explanation of the pathophysiology of hepatic lipidosis in dairy cows.

The purposes of this study are to assess the responses of increased supplemental dietary fat in the cow, without upsetting rumen fermentation, on the bile acid (BA) extraction rate in the liver and to determine whether this diet would affect the postprandial lipid profiles in the portal and hepatic venous blood. Six Holstein cows were equipped with catheters fitted in the portal and hepatic veins. Two cows each were assigned randomly to a sequence of three dietary treatments of 21-day period. The methodology of this study was based on the supplementation of the basal concentrate diet with 0 (control), 5, or 10% calcium salts of fatty acids (CSFA). The total bile acids were significantly increased in the portal and hepatic veins with the 5% CSFA diet, whereas no increase occurred with the 10% CSFA diet. Data obtained in this study showed that 10% CSFA diet failed to stimulate BA secretion to exceed the values obtained with 5% CSFA-diet. Moreover, there was no change in the hepatic extraction rate of BA in animals fed either the 0 or 5% CSFA diets which ranged from 2.4 to 6.5-fold and 3.1 to 7.3-fold, respectively. However, the extraction rate increased sharply with the 10% CSFA diet (27-fold). The median portal and hepatic concentrations of total lipids, triglycerides, total cholesterol, phospholipids and non-esterified fatty acids did not show any significant increase during feeding of the control diet. Moreover, feeding either the 5 or 10% CSFA diet did not significantly increase these values in either vein.

We determined aerial and aquatic oxygen uptake rates (M · o2) of Periophthalmodon schlosseri at rest and after exhaustive exercise at 30°C. Resting M · o2 in air (3.16 ± 0.10 (SE) μmol/ g/hr) was significantly higher than that in air saturated water (2.41 ± 0.06 μmol/g/hr). When the fish was placed in air after 2 min exhaustive exercise, M · o2 immediately increased about 2.5 times, thereby repaying oxygen debt of 5.0 μmol/g. In contrast, M · o2 failed to show any significant eleva- tion from the resting level as long as the fish was confined in water after exercise. However, when the fish was subsequently emerged, M · o2 did increase above the resting level, amounting to an excess oxygen uptake of 5.5 μmol/g. These results demonstrated that the gas transport system of P. schlosseri is better adapted to air breathing and the mode of adaptation limited the capability for water breathing. J. Exp. Zool. 284:265-270, 1999. © 1999 Wiley-Liss, Inc. Mudskippers are amphibious euryhaline fishes inhabiting intertidal mudflats of the Indo-west Pacific and tropical west Africa (Murdy, '89). Al- though these fishes differ in microhabitat, behav- ior, and feeding habits, all of them are more or less adapted to life out of water, and this remark- able ability of leading terrestrial life has been the subject of many studies (for review, see Clayton, '93; Graham, '97). Mudskippers have no specific air-breathing organ, relying instead on the skin, the gills and the buccopharyngeal mucosae. Their gills show different degrees of adaptation for aerial respiration. Periophthalmodon schlosseri is one of the larg- est mudskippers in the world, native to the South- east Asian countries. The fish is highly terrestrial, which has been attested both anatomically and physiologically. The gills of P. schlosseri have branched gill filaments, thick gill rods, and fused secondary lamellae, all indicating that the fish is poorly adapted for aquatic respiration (Low et al., '88, '90). Moreover, Kok et al. ('98) recently re- ported that resting oxygen uptake rates of P. schlosseri increased significantly upon terrestrial exposure. It has been considered that an indication of a species' capability for air breathing can be gained from comparison of the resting oxygen uptake rates in air and in water (Graham, '76). However, capabilities for air and water breathing may be better evaluated by comparing maximum M · o2 which a gas transport system of a species can at

Ontogenetic changes in the relationship between resting rate of oxygen consumption and wet body mass were examined at 20° C with the sea bream Pagrus major ranging from 0.00020 g (weight just after hatching) to 270 g (weight at 530 days old). There was a triphasic relationship between oxygen consumption of an individual fish M (μl min−1) and body mass W(g). During a very early stage (weight 0.00020–0.00025 g), corresponding to the pre-larval stage and with the transitional period to the post-larval stage, there was no substantial change in body mass. The mass–specific metabolic rate M/W (μl g−1 min 1) showed no clear relationship to body mass as expressed by the equation M/ W=4.86 + 1.47 D, where D is age in days. During the post-larval stage (weight 0.00031–0.005 g), M/W remained almost constant independent of body mass following the expression M= 12.5 W0.949. During the juvenile and later stages (weight 0.005–270 g), M/ W decreased with increasing body mass following the expression M= 6.3 W0.821 which is significantly different from the expression for the post-larval stage (P < 0.001). Ontogenetic changes in the metabolism-body mass relationship are discussed from the viewpoint of relative growth of organs with different metabolic activities.