TPase Activity Research Articles

Physiology of muscle in hatchery raised fish

Salmon and trout are widely cultivated in temperate countries both for food and as sport fish. Muscle tissues contribute both directly and indirectly to the commercial and recreational value of fish as a resource. Accounts of the gross structure, histology and chemical composition of salmon muscle had all appeared by the beginning of this century (Stirling, 1885; Paton, 1898; Greene, 1912, 1913). The present review gives a general account of the physiology of salmonid muscle and considers those factors in the captive environment (flow rate, temperature, oxygen) which influence muscle growth rate and performance. Australian salmon (Arripis trutta) are surrounded by an average of 4.2 capillaries, each supplying 145 Jlm2 of surface area (Mosse, 1979). Similar values of 3.4 capillaries/fibre and 139 Jlm2 surface area per capillary, have been obtained for the slow fibres of the brook trout (Satvetinusfontinutis, mitchil) (Johnston & Moon, 1980a). Both red and white fast fibres have been shown to occur in some fish species. Aerobic fast fibres have a reduced myoglobin and mitochondrial content, and increased glycolytic enzyme activities compared to slow fibres (Johnston et al., 1977a; Johnston & Maitland, 1980). Because of their intermediate position and colouring to red and white fibres, they are often referred to as 'intermediate' or 'pink' fibres. Histochemically they can be differentiated from other fibre types by their staining for myofibrillar A TPase activity following alkaline preincubation (Johnston et at., 1974; Mosse & Hudson, 1977). In rainbow and brown trout, pink fibres are restricted to a few scattered cells situated between the red and white muscle layers (Johnston & Lucking, 1978; Proctor et at.. 1980). However, in some species such as carp (Cyprinus carpio L.) aerobic fast fibres form a more extensive muscle layer comparable in area to that of slow fibres (Johnston et at., 1974). Biochemical studies have shown that carp pink fibres have an intermediate myofibrillar A TPase activity to red and white fibres, and a myosin light chain composition characteristic of fast muscles (Johnston et at., 1977a). White muscle consists of fibres with a wide range of different sizes (Fig. 2). Some quantitative ultrastructural studies of fish fast fibres are summarized in Table 2. The mean mitochondrial content (Table 2) and vascularization of fast fibres is considerably less than for slow fibres (Mosse, 1979). For example, the average capillary to fibre ratio in white fibres of the Australian salmon is 0.27. Thus the mean cross-sectional area supplied by each capillary of 9893 Jlm2 is almost 50 times greater than that for slow fibres (Mosse, 1979). Early histological (Greene. 1912) and histochemical studies (Boddeke et at., 1959) provided evidence for a heterogeneity in the aerobic capacities of white fibres. The finding that smaller fibres had higher lipid contents and SDHase staining intensities than large fibres, led some authors to coin the term 'mosaic muscle' to describe the white muscle of trout and salmon (Boddeke et at.. 1959; Webb, 1970). Recent quantitative analyses of the mitochondrial contents of teleost fast muscles illustrates both the heterogeneity of aerobic capacities within this fibre Muscle fibre types

Effect of hydroxychlorodiphenyl ethers (chlorinated pre-and isopredioxins) on erythrocyte membrane adenosinetriphosphatase activity.

The effect of hydroxychlorodiphenyl ethers (HO-ClX-DPEs; chlorinated pre- and isopredibenzodioxins), contaminants of technical chlorophenol preparations, on human erythrocyte membrane-bound adenosinetriphosphatases (ATPases) has been investigated. Both 2- and 3-HO-Cl9-DPE inhibited the Na+ + K+-activated, Mg2+-dependent ATPase (Na+, K+, Mg2+-ATPase). The Mg2+-dependent ATPase (Mg2+-ATPase) was stimulated at lower concentration of these compounds, but at higher concentrations there was a gradual decrease in the extent of stimulation, 2-Hydroxy-21, 41, 41-trichlorodiphenyl ether (2-HO-Cl3-DPE; Irgasan DP-300; Triclosan) was not as effective as the nonachloro compounds at inhibiting Na+, K+, Mg2+-ATPase and was inactive at stimulating Mg2+-ATPase. Pure pentachlorophenol (PCP) caused both inhibition of Na+, K+, Mg2+-ATPase and stimulation of Mg2+-ATPase, although each effect required a higher concentration of PCP than was needed for the HO-CL9-DPEs. The possible relationship of the effects of HO-CL x-DPEs on human erythrocyte membrane ATPase activities to the potent hemolytic activity of these compounds is discussed.

Molecular mechanisms of temperature adaptation in fish myofibrillar adenosine triphosphatases

Summary. Studies have been carried out on the Mg2+Ca2+-myofibrillar A TPase from the muscles of fish adapted to different environmental temperatures. The thermal stability of the A TPase is strongly correlated with mean habitat temperature. Activities of Antarctic fish A TPases are significantly higher at low temperatures than those of temperate and tropical water species. The effects of ionic strength on A TPase activity have also been studied. The Gibbs free energy of activation (JG*) was found to increase and enzyme activity decrease with increasing ionic strength within the physiological temperature range of each species. Significantly lower values of JG*, of around 1 Kcal/mole, are obtained for the A TPase of cold-adapted compared to tropical fish. Enthalpic and en tropic activation energies were also reduced in the cold adapted A TPases. It is postulated that the reduction of the enthalpic activation term in the cold adapted enzyme confers the advantage of reducing the temperature sensitivity of the rate limiting step thus partly compensating for the low heat content of the ce.1lular environment. Possible molecular mechanisms of temperature compensation in fish myofihrillar A TPases are discussed.

Tryptophan Metabolism of Rats Fed on an Amino Acid Diet

In an attempt to study on metabolic changes in rats fed on an amino acid diet devoid of one branched chain amino acid and of niacin, rats were force-fed a leucine-free, isoleucine-free, valine-free or complete amino acid diet for 3 or 4 days and killed 3 hr after the feeding on day 4 or 5 to observe the body weight changes, the urinary nitrogen and N1-methylnicotinamide (MNA), and liver tryptophanpyrrolase (TPase) and tyrosine-α-keto-glutarate transaminase (TKase) activities. The excretion of the urinary nitrogen and MNA, TPase and TKase activities, and fat content of livers of rats force-fed these amino acid deficient diets were higher than those fed the complete amino acid diet. It was further confirmed in the present study that changes in TPase activity of rats given diets devoid of one essential amino acid were in the same direction with changes in urinary MNA which was observed in the previous studies on rats given threonine-free, tryptophan-free, methionine-free, lysine-free and complete amino acid diets. However, such metabolic changes in rats fed the leucine-free diet were not so remarkable, compared with those of rats fed the other amino acid deficient diets.

Tryptophan Metabolism of Rats Fed a Threonine-free Amino Acid Diet

This study was conducted to clarify metabolic changes in rats given an amino acid diet devoid of one essential amino acid from the complete amino acid diet. At the beginning of the study, rats were force-fed the threonine- or tryptophan-free diet and the complete amino acid diet to observe the body weight changes, the urinary nitrogen and N1-methylnicotinamide (MNA), and changes in the liver enzyme activities, tryptophan pyrrolase (TPase) and tyrosine-α-ketoglutarate transaminase (TKase), and the like. It was observed that the excretion of the urinary MNA of rats force-fed a threonine-free diet was higher than that of animals fed the complete amino acid diet, and that increase of the liver TPase activity three hours after feeding was larger in the latter. It was presumed from the result that tryptophan in the diet, which is normally used for protein synthesis, was converted to nicotinic acid when protein formation was limited by the omission of threonine, and excreted in urine as MNA. There was also a remarkable increase of TKase activity 3 hours after feeding either the threonine-free diet or the complete amino acid diet, but a greater increase was observed with the deficient than with the complete diet. The mechanism of the induction of TPase and TKase activities after force-feeding of the different patterns of amino acid diets is discussed.