Showing papers in "Comparative Biochemistry and Physiology B in 1982"

Lipid nutrition in fish

Abstract: Dietary lipids play important roles in the energy production processes of animal tissues and as the source of essential fatty acids (EFA). Besides these functions they do have other important dietary roles as carriers of certain non-fat nutrients, notably the fat-soluble vitamins A, D and K. Recent studies on EFA in fish have demonstrated that EFA requirements of fish differ considerably from species to species. On the other hand, the results of studies on the energy requirements of fish during recent years have indicated that in the carnivorous fish such as rainbow trout, eel, yellowtail and plaice which have limited ability to utilize carbohydrates of high mol. wt as an energy source, dietary lipids play an important role in this respect and have a sparing action on dietary protein.

Differences in plasma cholesteryl ester transfer activity in sixteen vertebrate species

Abstract: 1. Large variations have been observed in the cholesteryl ester transfer activity of lipoprotein-free plasma isolated from 16 vertebrate species. 2. The different species have been arbitrarily divided into low, intermediate and high transfer activity groups, with man in the intermediate group. 3. Cholesteryl ester transfer activity did not correlate with the molar rate of cholesterol esterification in the plasma, nor with the concentration of cholesteryl ester in low density lipoproteins or high density lipoproteins. 4. It correlated positively and significantly with the concentration in very low density lipoproteins (r = 0.34, P = 0.014).

Aspects of intermediary metabolism in salmonid fish

Abstract: The basic pathways of intermediary metabolism that have been investigated so far in salmonid fish are very similar to those occurring in mammals and other animals, though important differences do exist with regards to the presence/absence and physiological importance of some pathways. Salmonids like many other fish, have relatively high dietary requirements for both protein and essential amino acids which in some cases are more than twice those of rat, chicken and pig (see reviews by Mertz, 1972; Cowey, 1975, 1979; Ogino, 1980). Carbohydrates are relatively poorly utilised by fish and the evidence suggests that proteins together with lipids are the major sources of energy (Atherton & Aitken, 1970; Pieper & Pfeffer, 1978; Cr6ach & Serfaty, 1974; Mommsen et al., 1980). This contrasts to the situation in omnivorous mammals where, under normal nutritional conditions, protein catabolism is of little significance in supplying energy whereas carbohydrates and lipids are important energy sources. Phillips (1969) has suggested that 70% of dietary calories in trout feed is from protein, thus a greater percentage of dietary protein is metabolised for energy, rather than utilized for body protein synthesis. Since the end produce of N-metabolism in teleosts is ammonia rather than the more energy costly urea or uric acid (as in mammals, birds and reptiles), fish do not derive the same amounts of energy from dietary constituents as do mammals and hence food protein may have a higher metabolisable energy than carbohydrates. The energy requirements of fish (being poikilothermic) are lower than mammals which expend much energy to maintain their body temperature. Since fish body temperature varies with the water temperature, then reaction rates and occurrence of some pathways within the fish are affected by the environmental temperature. This article is a somewhat brief attempt to describe aspects of the intermediary metabolism of amino acids, carbohydrates and lipids that have been reported for salmonids (predominantly).

Application of thyroid and steroid hormones as anabolic agents in fish culture

Abstract: A basic premise in any intensive culture system is to maximize growth at minimum cost, with an end product that is of high nutritive value and aesthetically acceptable to the consumer. This review is directed towards evaluating the role for thyroid hormones and steroids in fish culture. Particular attention has been given to the following topics: growth, appetite, food conversion, carcass composition, salt water tolerance, species specificity, deleterious responses and economic implications.

The effects of temperature and ration size on the growth and energetics of salmonids in captivity

Abstract: The literature on fish energetics and growth has increased markedly during the last 10 yr and has been summarized in several recent reviews (e.g. Webb, 1978; Mann, 1978; Elliott, 1979; Brett, 1979; Brett & Groves, 1979; Ricker, 1979). As these reviews include a large amount of work on salmonids in both their natural environment and in captivity, the present review does not attempt to survey all the literature. Emphasis is placed on the basic principles of energetics and growth, and the complex inter-relationships are illustrated chefly by work on brown trout (Salmo trutta) feeding on freshwater invertebrates. Salmonids in their natural environment are carnivores but in captivity, and especially in culture, there may be a marked change in their diet as well as changes in other factors such as temperature, light intensity and water chemistry. The effects of changes in diet are not considered in the present contribution, but are examined in detail in a recent review of fish nutrition (Cowey & Sargent, 1979). Few workers have compared diets over a wide range of ration levels, but a notable exception that demonstrates the importance of diet is a study of growth in young sockeye salmon (Oncorhynchus nerka) feeding on six diets (Brett, 1971). As the diet changed from the most effective to the least effective for growth, the maximum food intake increased and there was a corresponding decrease in conversion efficiency. Although many factors can influence the growth of salmonids, it is generally agreed that fish size, water temperature and the level of energy intake (ration size) are the three most important independent variables. The present review examines the effects of these variables on the major components of the energy budget.

Glutathione peroxidase activities of animal tissues

Abstract: 1. Selenium-dependent, selenium-independent and total glutathione peroxidase activities were measured in liver, kidney, heart, lung, intestine and stomach of a variety of animals, mostly mammals. 2. Total glutathione peroxidase activity of liver was highest in the order: hamster greater than gerbil approximately equal to rabbit greater than mouse greater than rat. Total glutathione peroxidase activity was adequate in the livers of other mammals and in the kidney, heart, lung, intestine and stomach of all mammals. 3. The total glutathione peroxidase activities in the following tissues correlated significantly: liver and kidney; heart and lung; and intestine and stomach. Selenium-dependent glutathione peroxidase activities in rat tissues correlated with reported activities of copper-superoxide dismutase in the same tissues. 4. Considering the phylogenetic distribution of total glutathione peroxidase activities, the rodent limb of the phylogenetic tree has the highest activities.

The comparative isozymology of vertebrate hexokinases.

Abstract: 1. 1. Multiple hexokinase isozymes have been found in most vertebrates. Since each isozyme displays distinctive structural, kinetic and regulatory characteristics, the system qualifies as a useful probe for studies on molecular evolution. 2. 2. At least seven types of chromatographic patterns of liver hexokinases have been observed in mammals. In contrast, each Class of lower vertebrates present only two or three distinct profiles. 3. 3. Aves and higher Reptiles do not have the same hexokinase isozymes as other vertebrates. The nature of the differences is poorly understood. 4. 4. Ontogenetic changes of liver hexokinase profiles are quite different in rat, chick and frog. 5. 5. Structural comparisons of three vertebrate hexokinases having a molecular weight of ∼100,000 suggest that those isozymes originated from a pre-vertebrate ancestor through gene duplication followed by fusion and further duplication events. Another hexokinase (the so-called glucokinase), with half the molecular weight, may have arisen either as the result of subsequent even splitting of the fused gene or, less probably, by divergence from a duplicated gene before the fusion event.

Characteristics of two trypsin type isozymes isolated from the Arctic fish capelin (Mallotus villosus)

Abstract: 1. 1. Two trypsin-like enzymes, assayed by their amidase activity with N-α-benzoyl-dl-arginine-p-nitroanilide (dl-BAPNA) as the substrate, were isolated from the gut of the arctic fish capelin (Mallotus villosus). 2. 2. Purification involved affinity chromatography (Benzamidine-CH-Sepharose 4B) of the 30 to 70% (NH4)2SO4 precipitation fraction of a crude extract of the gut, followed by DEAE-Sephadex chromatography, yielding two enzymes, designated Enzyme I and II. 3. 3. Both enzymes had MW of about 28,000 as determined by SDS-electrophoresis. Their isoelectric points were 5.6–5.9 (Enzyme I) and 5.1–5.3 (Enzyme II) and they had similar amino acid composition. 4. 4. Both enzymes were inhibited by standard trypsin inhibitors including the serine protease inhibitor phenylmethyl sulphonyl fluoride (PMSF), but not by the chymotrypsin inhibitor l-1-tosylamide-2-phenylethyl chloromethyl ketone (TPCK). 5. 5. The enzymes had a pH optimum of 8–9 and their stability was not affected by CaCl2. Low pH (2.3) caused an initial rapid loss of enzyme activity, followed by relatively slow decomposition of the activity remaining after 1 hr at 4°C. 6. 6. The enzymes had an apparent temperature optimum of 42°C, resulting from rapid self digestion at higher temperatures.

Comparison of carotenoids in the ovaries of marine fish and shellfish.

Abstract: 1. The following carotenoids were isolated and identified: astaxanthin diester, tunaxanthin monoester, astaxanthin monoester, tunaxanthin, astaxanthin, doradexanthin, lutein, zeaxanthin, idoxanthin, triol and tetrol from nine species of fish; astaxanthin diester, astaxanthin monester, astaxanthin, doradexanthin, zeaxanthin, idoxanthin and tetrol from four species of crustacean, astaxanthin, pectenolone, pectenoxanthin, pectenol and tetrol from four species of scallop. 2. Tunaxanthin monoester and astaxanthin diester were major carotenoids in skipjack and Pacific cod, respectively. 3. The concentration of carotenoids ranged 0.065-1.95, 1.30-5.91 and 1.56-7.15 mg per 100 g ovary for fish, crustacean and scallop, respectively. 4. The species- and tissue-specificity of ovarian carotenoids and their possible role are discussed.

Comparative studies on superoxide dismutase, catalase and peroxidase levels in erythrocytes and livers of different freshwater and marine fish species

Abstract: 1. 1. The activities of superoxide dismutase, catalase and peroxidase in erythrocytes and liver of freshwater and marine fish species were investigated. 2. 2. These antioxidative defence enzymes showed marked interspecies differences and also seasonal variations. 3. 3. The very high values of peroxidase activities in fish erythrocytes suggest the predominant role of this enzyme in protection of polyunsaturated acids against uncontrolled oxidative processes.

Comparison of plasma concentrations of vitamin D and its metabolites in young and aged domestic animals.

Abstract: 1. Vitamin D and its metabolites were measured in the plasma of five species of rural domestic animals. 2. Concentration of 1,25-dihydroxyvitamin D was higher (P less than 0.01) in young animals (range 24-118 pg/ml, means +/- SD = 72.0 +/- 30.0) than in adult animals (range 14-67 pg/ml, means +/- SD = 40.2 +/- 22.6). 3. 25-Hydroxyvitamin D3-26,23 lactone was present only in the chick and the pig. 4. Unsheared sheep appeared to be inefficient utilizers of the photochemical conversion of 7-dehydrocholesterol to vitamin D3. 5. Conversion of 25-hydroxyvitamin D to 24,25-dihydroxyvitamin D was most efficient in species with high plasma phosphorus concentrations (pig, sheep).

Physico-chemical properties of the settlement factor proteins from the barnacle Balanus balanoides

Abstract: 1. 1. Settlement active extracts of Balanus balanoides have been prepared from crushed, whole barnacles and from the separated shell and mantle lining. 2. 2. The active component was non-dialysable, resistant to boiling and could be fractionated by precipitation with ammonium sulphate. Extracts of the shells contained coloured pigments which were tightly bound to the proteins. 3. 3. SDS-electrophoresis of unboiled extracts showed nine major protein bands with molecular weights between 18,000 and 180,000 daltons. Boiled extracts showed only one protein band of 23,500–25,000 daltons which appears to be the most stable sub-unit. 4. 4. Based on physico-chemical evidence (gel-filtration, isoelectric focusing and amino acid analysis) we have concluded that the settlement factor from B. balanoides consists of a polymorphic system of closely related proteins derived from sub-units of molecular weight 5–6000 and 18,000 daltons.

The chemical defense of four Mediterranean nudibranchs

Abstract: 1. 1. The chemical defense of the Mediterranean nudibranchs Phyllidia pulitzeri, Dendrodoris limbata, Glossodoris valenciennesi and Glossodoris tricolor has been investigated. 2. 2. By means of bioassays the distastefulness has been shown to be attributable to chemical factors located in the body wall. 3. 3. All the biologically active compounds isolated in the present investigation were known compounds, mainly deriving from the sponges on which the nudibranchs feed.

Similarities in vitellogenin and control of vitellogenin synthesis within the genera sarcophaga, calliphora, phormia and lucilia (diptera)

Abstract: 1. 1. The major yolk polypeptides from the different species are identified by SDS-gradient gel electrophoresis. 2. 2. Vitellogenins of the 4 species have similarities in both minimum number and size of their polypeptides. They also react with antibodies raised against vitellin of Sarcophaga. 3. 3. In males of all species ecdysterone but not the JH analog methoprene induces the yolk polypeptides. 4. 4. In non-protein fed females only ecdysterone is able to replace the triggering effect of the protein meal on vitellogenin synthesis. 5. 5. The inability to stimulate vitellogenin synthesis in vivo by a JH analog is discussed.

The density profile and cholesterol concentration of serum lipoproteins in domestic and laboratory animals

Abstract: 1. 1. By means of density gradient ultracentrifugation, the density profile of the serum lipoproteins was studied in 14 species of domestic and laboratory animals: the pig, chicken, rhesus monkey, rabbit, dog, horse, sheep, cat, mouse, goat, cow, guinea-pig, trout and rat. 2. 2. The concentration of cholesterol in whole serum and the lipoprotein fractions of these animal species was also determined. 3. 3. There were large differences in the density profile of the serum lipoproteins among the various animals studied and the results indicate that the density limits employed for human serum lipoproteins are not directly applicable to the lipoproteins of animals. 4. 4. In most of the animals studied, three major lipoprotein fractions could be observed as in man. 5. 5. However, such a clear pattern was not found in the cow, rat and guinea-pig. 6. 6. In the animals studied, with the exception of the pig and the guinea-pig, most of the cholesterol in the serum was carried in the high density lipoprotein fraction.

Physiology of muscle in hatchery raised fish

Abstract: 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

Isolation and characterization of a photoprotein, “phialidin”, and a spectrally unique green-fluorescent protein from the bioluminescent jellyfish Phialidium gregarium

Abstract: 1. 1. A calcium-activated photoprotein, “phialidin” and a green-fluorescent protein (P-GFP) have been isolated from the bioluminescent hydrozoan jellyfish, Phialidium gregarium and purified 170-fold and 500-fold, respectively. 2. 2. Phialidin has a mol wt of 23,000 ± 4% by gel filtration and a pH profile for calcium-stimulated bioluminescence between 6 and 9.5. It is less sensitive than aequorin, however, to low levels of calcium. 3. 3. With regard to mol wt (57,000 ± 4%) and thermal stability (TM = 69°C), Phialidium GFP more closely resembles Renilla GFP than Aequorea GFP. 4. 4. The corrected fluorescence emission spectrum of P-GFP resembles those of Renilla and Aequorea GFP in shape; but, having a peak emission at 497 nm, it is unique among all known GFP's.

Anaerobic metabolism in upogebia pugettensis and callianassa californiensis (crustacea, thalassinidea)*

Abstract: 1. 1. Glycogen is the only significant substrate in the anaerobic metabolism of Upogebia pugettensis and Callianassa californiensis. Small quantities of aspartate are utilized in addition. 2. 2. l-lactate is accumulated as the main end-product and l-alanine and succinate are minor end-products. 3. 3. Striking differences between both species were found in the amounts of glycogen stored, in the rate of lactate production and in the resistance of anoxia. 4. 4. Accumulation of lactate also occurs in the natural habitat, but the levels reached are rather low. 5. 5. The results suggest that in crustaceans lactate formation is the characteristics mode of anaerobic metabolism as opposed to other invertebrates.

Evolution of gluconeogenic enzyme activities during starvation in liver and kidney of the rainbow trout (Salmo gairdneri)

Abstract: 1. 1. There was a general increase in the activities of enzymes involved in gluconeogenesis in liver and kidney of rainbow trout, Salmo gairdneri , during the second month of starvation. 2. 2. The need of gluconeogenesis during the first month of the starvation period was probably minimal because of the utilization of liver glycogen as a source of blood glucose. 3. 3. The decline of fat was more pronounced than that of protein total content in absolute values, suggesting that lipid reserves were the main sources of energy during starvation.

Amylase in chicken intestine and pancreas

Abstract: 1. The level and distribution of amylase in the chicken intestine and pancreas in addition to some of their properties were examined. 2. The level of amylase was found to be high in chickens and was present in all parts of the intestine except caeca where only traces were detected. 3. Most of the amylase activity was found in the contents of the jejunal part of the small intestine. This was attributed to the secretion from the intestinal tissue and the pancreas. 4. The investigation of different properties, namely, pH optimum, chloride ions effect and the effect of substrate concentration, revealed that the intestinal tissue amylase is different from pancreatic amylase. 5. As amylase in the intestine was found mainly confined to the jejunal lumenal contents, it is assumed that the jejunum is the major site of starch digestion in chickens.

Partial purification and characterization of particulate acid phosphatase of Leishmania donovani promastigotes

Abstract: 1. More than 90% of the total acid phosphatase activity in a sonicate of L. donovani promastigotes is contained in a particulate fraction (200,000 X g 30 min). The enzyme can be quantitatively extracted and solubilized with the aid of Triton X-100 (0.2 g/100 ml) and purified over 200-fold with 54% yield by chromatography on DEAE-Sephadex, QAE-Sephadex, Sepharose 4B and concanavalin-A Sepharose. 2. The phosphatase is a true acid hydrolase (pH optimum, 5.0-5.5) and has a rather broad substrate specificity; it will catalyze the hydrolysis of 4-methylumbelliferylphosphate, thymolphthalein diphosphate, pyridoxal phosphate, fructose 1,6-diphosphate, glucose 6-phosphate, glucose 1-phosphate, ADP and AMP. 3. It is a large (170,000 daltons in the presence of Triton X-100), stable and acidic enzyme (pI = 4.1) that has the electrophoretic mobility of a type zero or type 1 isoenzyme in acid (pH 4.3) polyacrylamide gels. 4. The enzyme is inhibited by sodium fluoride, 2-mercaptoethanol and mumolar amounts of a number of polyanionic molybdenum and heavy metal complexes that include the following: [C(NH2)3]4[(C3H7O3PO3)2Mo5O15] X 3H2O, [C(NH2)3]2[(C6H5)2AsMo4O15H] X H2O, (NH4)4[SiMo12O40] X H2O and (NH4)6[P2Mo18O62] X 9H2O. 5. L. donovani promastigotes contain very low levels of 10 other acid pH optimum hydrolytic enzymes, with the exception of modest levels of alpha-fucosidase.

Subcellular distribution, and physical and immunological properties of hepathic alanine: Glyoxylate aminotransferase isoenzymes in different mammalian species

Abstract: 1. 1. Subcellular distribution, and physical and immunological properties of hepatic alanine: glyoxylate aminotransferase isoenzymes 1 and 2 were examined with ten different mammalian species. 2. 2. Intracellular organelles containing isoenzyme 1 varied from species to species; isoenzyme 1 was located in the peroxisomes, mitochondria or both organelles. In contrast, isoenzyme 2 was found only in the mitochondria but not in the peroxisomes. 3. 3. In any species, isoenzyme 1 had molecular weight of approx. 80,000 with two identical subunits, and isoenzyme 2 approx. 200,000 with four identical subunits. 4. 4. In any species, an immunological cross-reactivity was observed among isoenzymes 1 and among isoenzymes 2 but did not between isoenzymes 1 and isoenzymes 2.

Hepatic cytochrome P-450-dependent monooxygenase systems of the trout, frog and snake--III. Induction.

Abstract: 1. 3-Methylcholanthrene administration increased levels of cytochrome P-450, benzo[a]pyrene hydroxylase activity and p-nitrophenetole O-deethylase activity in hepatic microsomes from the brown trout (Salmo trutta), leopard frog (Rana pipiens) and the garter snake (Thamnophis). The level of aminopyrine N-demethylase activity was increased in trout microsomes, but not in those from the frog, snake or rat. 2. The shift in the Soret maximum of the reduced carbon monoxide difference spectrum of cytochrome P-450 from 450 to 448 nm, which is observed when 3-methylcholanthrene is administered to rats, was not seen in microsomes from the trout, frog or snake. 3. Benzo[a]pyrene hydroxylase activity induced by 3-methylcholanthrene in the trout, frog and snake was inhibited by relatively low concentrations of SKF 525-A, but that induced in the rat was not. alpha-Naphthoflavone inhibited 3-methylcholanthrene-induced benzo[a]pyrene hydroxylase activity in the trout, frog and rat, but not in the snake. 4. 3-Methylcholanthrene induced an increase in the 455/430 nm peak height ratio of the reduced ethylisocyanide spectrum of microsomes in the rat and trout, but not in the frog or snake. 5. These observations (items 1--4 of the abstract) show that different species of cytochrome P-450 are induced by 3-methylcholanthrene in the four vertebrates. 6. Phenobarbital did not alter the components or the activities of hepatic monooxygenase systems in the trout, frog or snake, even though it was shown to accumulate in the livers of these vertebrates as readily as it does in the liver of the rat.

The cleavage of carotenoid esters by cholesterol esterase

Abstract: 1. 1. Standard hydrolysis of carotenoid esters typically provides complicated mixtures of reaction products. A facile method was developed for the specific hydrolysis of carotenoid esters using a cholesterol esterase. This method gives high yields of the desired unesterified products. 2. 2. The utility of this method in the characterization of carotenoid esters was assessed by comparing catalytic activity of this enzyme with the following substrates: esters of astaxanthin, 2′-norastaxanthin, and 2,2′-bisnorastaxanthin, as well as fucoxanthin.

Characterization of the lysozyme of Mytilus edulis (L)

Abstract: 1. 1. Lysozyme isolated from the crystalline style of Mytilus edulis is a true N-acetylmuramylhydrolase (E.C. 3.2.1.17). 2. 2. The enzyme is optimally active at approx pH 7.1, I = 0.011, with a secondary optimum at pH 4.6, I = 0.054. 3. 3. Cell walls of Micrococcus luteus, Escherichia coli, and Bacillus subtilis were degraded by the lysozyme but chitin or cell walls of Staphylococcus aureus were resistant to its activity. 4. 4. Tetra-N-acetyl chitotetraose inhibited enzyme activity more than N-acetylglucosamine, di-N-acetyl chitobiose, tri-N-acetyl chitotriose or penta-N-acetyl chitopentaose.

Adaptative features of ectothermic enzymes--I. Temperature effects on the malate dehydrogenase from a temperate fish Leiostomus xanthurus.

Abstract: 1. 1. Following electrophoresis the s-MDH activity of Leiostomus xanthurus and many other species of fish and amphibian appears in three sharp, equally-spaced, anodal bands. Each band is a dimer (AA, AB and BB) and two loci are active. 2. 2. In Leiostomus tissue extracts A and B subunits are present at differing quantitative levels and their activities can be modified by changes in environmental temperature. 3. 3. Thermostability and thermal dependency tests show that, similar to what occurs during acclimatization, the AA isozyme is more stable to heat than is the BB isozyme. The BB isozyme is activated by low temperatures and is rapidly inactivated by high temperatures. 4. 4. Extracts from a variety of fishes, amphibians, reptiles and birds suggest that when only one or two s-MDH bands are present, they behave as does the AA homodimer in Leiostomus xanthurus, i.e., are stable at elevated temperatures.

The vitamins required for cultivated salmonids

Abstract: Vitamins are organic chemical compounds which are required in small amounts for normal growth, reproduction, health, and maintenance of fish metabolism. Eleven water-soluble vitamins and four fat-soluble vitamins are known to be required by salmonids. Compared with most mammals and birds, the gastrointestinal tract of fishes does not contain a rich pattern of established micro-organisms (Margolis, 1953); therefore, it cannot be assumed that the fish obtains appreciable quantities of vitamins from microbial synthesis in the intestine. Transformation of the amino acid, tryptophan, into the vitamin, niacin, is very inefficient in trout and salmon (Poston & DiLorenzo, 1973; Poston & Combs, 1979); therefore, niacin must be included in salmonid feeds. Intensive production of fish in water low in natural food chain organisms amPlifies the importance of providing the dietary requirements for the vitamins listed in Table 1. Vitamins are grouped into the eight water-soluble B vitamins, the macrovitamins L-ascorbic acid, choline and myo-inositol, and the fat-soluble vitamins A, D, E and K. A typical vitamin test diet for fish to control the water-soluble vitamins is listed in Table 2.