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Enzymatic and non-enzymatic antioxidants serve as an important biological defense against environmental oxidative stress. Information on antioxidant defense in fish is meager despite that fish are constantly exposed to a myriad of environmental stress including the oxidants. This study, therefore, assesses the activities of antioxidant enzymes viz., glutathione peroxidase, catalase and glutathione S-transferase and the non-enzymatic antioxidants viz., glutathione and metallothionein in various tissues of freshwater fish Channa punctatus (Bloch), in response to short-term and long-term exposures to paper mill effluent. The fish were exposed to the effluent at a concentration of 1.0% (v/v) for 15, 30, 60 and 90 days. The exposure caused a time-dependent increase in glutathione level (P < 0.001), activities of glutathione peroxidase (P < 0.05 to P < 0.001), glutathione S-transferase (P < 0.001) and a marginal initial decrease in catalase activity in the liver (P < 0.01 to P < 0.001). Metallothionein was induced in liver after 60 days of exposure. Two isoforms of metallothionein were detected. Catalase activity also increased 60 days afterwards. Antioxidant pattern was different in gill and kidney showing that liver was more resistant to oxidative damage as compared to gills and kidney. Our results demonstrate a pollutant-induced adaptive response in fish. In addition, levels of enzymatic and non-enzymatic tissue antioxidants may serve as surrogate markers of exposure to oxidant pollutants in fish.

The previous claims by others of a novel choline transfer reaction involving CDP-choline and leading to the conversion of [U-14C]glycero-3-phosphate to glycero-3-phosphocholine in liver sub-cellular fractions could not be confirmed. Apparent labelling of glycero-3-phosphocholine, isolated by paper chromatography, was, in fact, explained by contamination by other radioactive metabolites, especially D-glucose. A synergistic effect on gluconeogenesis from [U-14C]glycero-3-phosphate was obtained by incubating well-washed mitochondria with washed microsomes.

The fate of alpha and epsilon lysine amino groups has been explored in rat liver homogenate by means of L-lysine labelled selectively in the two positions. alpha-15NH2 and epsilon-15NH2 are rapidly incorporated into the amino group of glutamic acid and it seems at first that both transaminations occur simultaneously. But the reversible transfer of the amino group between alpha-aminoadipic acid and glutamic acid, determined by means of labelled alpha-aminoadipic acid, proceeds swiftly, and the incorporation of alpha-15NH2 from the corresponding labelled lysine in glutamic acid may be easily explained by epsilon-transamination and saccharopine formation. The direct transamination of the alpha-amino group of L-lysine is most improbable and might be limited to some microorganisms and to epsilon-N-substituted lysine derivatives.

Purified proteochondroitin sulfate was incubated at pH 4.0 with a rabbit liver lysosomal enzyme fraction. The formed degradation products were isolated by gel filtration followed by reduction with NaB3H4. After acid hydrolysis of the reduced digest, the hydrolysate was passed through Dowex 50W-X8 and 1-X2 columns. The separated neutral sugars were then subjected to paper chromatography, which demonstrated that galactose and xylose had been at the reducing termini of chondroitin sulfate after incubation with the liver lysosomal preparation. These results suggest the presence in the liver lysosomal preparation of an endo-beta-galactosidase and an endo-beta-xylosidase which act at the linkage region of proteochondroitin sulfate.

The glycosaminoglycan of rat liver can be separated into five distinct fractions; a hyaluronic acid fraction, a heparan sulfate fraction with a molar ratio of sulfate to hexosamine (S/HexN) around 0.7, a heparan sulfate fraction with a S/HexN ratio around 1.4, a dermatan sulfate fraction with a S/HexN ratio near unity, and a dermatan sulfate fraction with a S/HexN ratio around 1.3. Enzymatic analysis of the two dermatan sulfate fractions indicates that they differ significantly in that the high sulfated fraction contains relatively more N-acetylgalactosamine 4,6-bissulfate units (about 26% of the total hexosamine). In experimental injury produced by carbon tetrachloride, the low sulfated fraction increases as much as 9-fold on a dry weight basis, bearing no linear relationship to the amount of the high sulfated fraction which increases only 2-fold. A significant shift is also observed in the levels of the two heparan sulfate fractions. In this case, however, the high sulfated fraction shows a much more pronounced increase than does the low sulfated fraction. On the basis of these observations, it is suggested that for each of the dermatan sulfate and heparan sulfate classes there are at least two pools, distinguished by sulfation degree and perhaps by turnover rate and physiological function.

A rapid and sensitive isotopic method is presented for the assay of S-adenosylhomocysteine hydrolase (EC 3.3.1.1) activity, based on the formation of radioactive S-adenosylhomocysteine labelled in the adenosine portion. The radioactive product is separated either by low-voltage paper electrophoresis or by using phosphocellulose ion-exchange paper. Some kinetic properties of the enzyme from rat liver have shown to be clearly different from those reported earlier for this enzyme. The use of erythro-9-(2-hydroxy-3-nonyl)adenine, a potent inhibitor of adenosine deaminase, makes it possible to measure the S-adenosylhomocysteine hydrolase activity in tissues with a high adenosine deaminase activity, e.g. in intestinal mucosa.