Vitamin E nutrition and pancreas disease in farmed Atlantic salmon (Salmo salar L.)

Tissue vitamin E in farmed Atlantic salmon (Salmo salar L.) fed commercial diets, were measured by high-performance liquid chromatography. In healthy fish, fed diets containing about 20 mg lOO g*‘supplementary all-rac-a-tocopheryl acetate, vitamin E (a-tocopherol) accummulated in the liver and plasma. Over a 20 month period, beginning four months prior to seawater transfer, mean a-tocopherol concentrations ranged between 51 and 754 |tg g*' in liver and 7 and 68 pg nl*‘ in plasma. Sharp increases in the a-tocopherol content of these tissues were related to a rise in the proportion of lipid as polyunsaturated fatty acid in response to transfer to seawater. There was no marked difference between tissue vitamin E concentrations in farmed and wild salmon. In contrast, vitamin E depletion was found to be a consistent feature of pancreas disease (PD) in farmed salmon. The degree of depletion was found to vary from case to case. A serial study indicated that the onset of vitamin E depletion occurred early in the course of the outbreak. Soma information was collected with regard to the cause and possible pathological effects of vitamin E depletion in PD, but definitive studies are still required. Parental administration of all-rac-a-tocopherol in molten cocoa-butter reduced plasma pyruvate kinase activity in affected fish from one outbreak of PD, suggesting that muscle degeneration in PD may respond to treatment with vitamin E. However, no effects on the histological signs of PD were noted. In a second outbreak, supplementation of the diet with 100 mg all-rac-a-tocopherol 100 g'* produced no statistically significant elevation of plasma vitamin E or reduction in plasma pyruvate kinase activity. In a third case, dietary supplementation with a water-miscible preparation of all-rac-a-tocopheryl acetate produced no significant rise in plasma vitamin E concentrations and no histological evidence of any therapeutic effect was obtained. Relationships between husbandry practices and vitamin E status were examined experimentally. Acute handling and crowding had no observable effect on plasma a-tocopherol concentrations. Chronic crowding stress produced a slight, but statistically insignificant, reduction in plasma and liver a- tocopherol concentrations. Chronic crowding stress did not precipitate signs of vitamin E deficiency in salmon fed diets with no supplementary source of a- tocopherol. Starvation caused a significant depletion of a- tocopherol within 3 weeks in tbe plasma and liver of post-smolts in experimental tanks, but had no effect on tissue vitamin E concentrations in one sea-winter salmon held in sea-cages over a 4 week period. Differential feeding rates of l-3t body weight day* over a six week period had no measurable effect on plasma vitamin E concentrations. The dietary level of a-tocopheryl acetate had no effect on the magnitude of the cortisol response to acute handling stress and no beneficial effect of vitamin E supplementation was determined in fish under conditions of chronic crowding

Product Protection, the Key to Developing High Performance Methane Selective Oxidation Catalysts

Selective, direct conversion of methane to methanol might seem an impossible task since the C−H bond energy of methane is 105 kcal mol^(−1) compared to the C−H bond energy for methanol of 94. We show here that the Catalytica catalyst is successful because the methanol is protected as methyl bisulfate, which is substantially less reactive than methanol toward the catalyst. This analysis suggests a limiting performance for systems that operate by this type of protection that is well above the Catalytica system

Factors influencing academic success or failure of first-year and senior university students: do education students and lecturers perceive things differently?

South African universities are changing in several very important ways; their entry standards are changing, their programmes are focusing more specifically on the outcomes that learners are required to achieve, and their student populations are becoming more diverse. These changes are occurring in a climate of increased accountability. It is, therefore, important for universities to be concerned about the standards of their academic programmes and about the success rates of students. Together, these factors have produced a range of opinions about what needs to happen in universities if the diverse range of students is to be successful in outcomes-based programmes that maintain high standards. Some educators argue that entry standards are the most important determinants of success at university; others maintain that non-academic factors must also be considered. There is considerable evidence that the views and expectations about success held by lecturers and stud ents are not always consistent. This article presents the results of a recent empirical investigation at the University of Pretoria that attempted to identify the post-enrolment factors that lecturers and students perceived as having important influences on students' success in their university studies. The study investigated the different expectations of first-year students, senior students and lecturers and identified numerous important similarities and inconsistencies. Most notably, there was a high and significant correlation between the rankings the three groups (lecturers, first-year students and senior students) gave to 52 factors linked to successful university study. There was also a high and significant correlation between the rankings of lecturers and senior students on 55 factors suggestive of unsuccessful university study. However, the perceptions of first-year students were not strongly correlated with either lectures or senior students. This suggests that First-year students may have unrealistic expectations about the non-academic factors that could reduce their chances of successful study. The results of the research could be used in three ways. University administrators could provide more supportive learning environments to enhance the chances that students will be successful and lecturers could also use the information to enhance the influences of positive factors on student learning. The influence of negative factors could also be minimised accordingly. Finally students could also be assisted and supported to approach university studies in a way that will increase their chances of success. South African Journal of Education Vol.23(4) 2003: 254-26

Iridium complexes bearing a PNP ligand, favoring facile C(sp^3)–H bond cleavage

Hydrogen iodide is lost upon reaction of PNP with IrI_3, where PNP = 2,6-bis-(di-t-butylphosphinomethyl)pyridine to give crystallographically characterized Ir(PNP)*(I)_2, which reacts with H_2 to give Ir(PNP)(H)(I)_2. Ir(PNP)(Cl)_3 is relatively inert towards the intramolecular C–H activation of the tert-butyl's of the PNP ligand

Acceleration of Nucleophilic CH Activation by Strongly Basic Solvents

(IPI)Ru(II)(OH)_n(H_2O)_m, 2, where IPI is the NNN-pincer ligand, 2,6-diimidizoylpyridine, is shown to catalyze H/D exchange between hydrocarbons and strongly basic solvents at higher rates than in the case of the solvent alone. Significantly, catalysis by 2 is accelerated rather than inhibited by increasing solvent basicity. The evidence is consistent with the reaction proceeding by base modulated nucleophilic CH activation