TURBIDITY AND OTHER PHYSICAL FACTORS IN NATAL ESTUARINE SYSTEMS PART 1: SELECTED ESTUARIES

SUMMARY

Data on turbidity and the factors influencing it, such as wind and substratum, were collected from eight representative estuaries along the Natal Coast. The results showed that Natal Estuaries can be divided into one of four groups, according to the turbidity regime present in the system, as either Clear (<10 Nephelometric Turbidity Units = NTU), Semi Turbid (10–50 NTU), Predominantly Turbid (51–80 NTU) and Very Turbid (>80 NTU). The influence of the tidal cycle on turbidity, salinity and temperature was also investigated. It was found that tidal action often creates gradients within a system. Turbidity gradients were more frequent in occurrence than either salinity or temperature gradients.     

Effect of prebiotic mannan oligosaccharide on hematological and blood serum biochemical parameters of cultured juvenile great sturgeon (Huso huso Linnaeus, 1754)

The nutritional effects of prebiotic mannan oligosaccharide were evaluated using hematological and blood serum biochemical parameters in cultured juvenile great sturgeon (Huso huso). Fish were offered formulated diets containing two levels of prebiotic mannan oligosaccharide (2 and 4 g kg^?1); a basal diet with no prebiotics was used as control. The experiment lasted for 46 days. Blood samples were collected from the caudal veins of 18 apparently healthy fish (average weight 217.77 ± 29.8 g) at the end of the trial. No significant differences were found in the serum enzyme activity levels between treatments (P > 0.05). However, adding mannan oligosaccharide as a supplement to the basal diet resulted in significant differences in lymphocytes and eosinophils between the control and the 2 g kg^?1 treatment (P < 0.05) as well as a significant difference in the creatinine factor in the 2 g kg^?1 mannan oligosaccharide treatment (P < 0.05). The results show that it would be advantageous to add 2 g kg^?1 mannan oligosaccharide to the diets of juvenile great beluga sturgeon (Huso huso).     

Inhibitory effects of oxali-Platin as a chemotherapeutic drug on the function and structure of bovine liver catalase

Abstract

Communicated by Ramaswamy H. Sarma     

Functional and structural alterations induced by copper in xanthine oxidase

Xanthine oxidase （XO）, a key enzyme in purine metabolism, produces reactive oxygen species causing vascular injuries and chronic heart failure. Here, copper＇s ability to alter XO activity and structure was investigated in vitro after pre-incubation of the enzyme with increasing Cue＋ concentrations for various periods of time. The enzymatic activity was measured by following XO-catalyzed xanthine oxidation to uric acid under steady-state kinetics conditions. Structural alterations were assessed by electronic absorption, fluorescence, and circular dichroism spectroscopy. Results showed that Cu^2＋ either stimulated or inhibited XO activity, depending on metal concentration and preincubation length, the latter also determining the inhibition type. Cu^2＋-xo complex formation was characterized by modifications in XO electronic absorption bands, intrinsic fluorescence, and α-helical and β-sheet content. Apparent dissociation constant values implied high- and low-affinity Cu^2＋ binding sites in the vicinity of the enzyme＇s reactive centers. Data indicated that Cu^2＋ binding to high-affinity sites caused alterations around XO molybdenum and flavin adenine dinucleotide centers, changes in secondary structure, and moderate activity inhibition; binding to low affinity sites caused alterations around all XO reactive centers including FeS, changes in tertiary structure as reflected by alterations in spectral properties, and drastic activity inhibition. Stimulation was attributed to transient stabilization of XO optimal conformation. Results also emphasized the potential role of copper in the regulation of XO activity stemming from its binding properties.     

Glycoalkaloid and nitrate content of potatoes as affected by method of selenium application

A comparison of two methods of selenium application, banding and foliar spray, of sodium selenite (Na₂SeO₃) on total glycoalkaloid (TGA) and nitrate nitrogen (NO₃-N) was studied during each of two consecutive years. The levels of application used were 0.0, 1.6 (0.75), 3.36 (1.5), and 5.6 (2.5) kg/ha (ppm soil). Both TGA and NO₃-N were significantly reduced by application of 1.5 and 2.5 ppm of sodium selenite. Tuber selenium levels were significantly increased at all levels of application, using either banding or foliar spray, but were well below the toxic range for human consumption. Banding resulted in greater uptake of Se, and greater decreases in TGA and NO₃-N as compared to foliar spray.     

A REVIEW OF THE AQUATIC AVIFAUNA OF THE MHLATHUZE ESTUARY

Summary

This paper is the first published review of the aquatic avifauna of the Mhlathuze Estuary. It also uses a regional approach in order to determine the potential for certain hitherto unrecorded species to occur there. The study shows that there appear to have been significant changes in the aquatic avifauna over the past 15 years and that these have, by and large, been negative. However, information on the current status of the avifauna is lacking and it is considered important to determine this as soon as possible.