Terrestrische refractie

Civil Engineering and Geoscience

An enzyme-histochemical study concerning the localization of steroid glucuronide production in the reproductive organs of African catfish, Clarias gariepinus

In ovaries of the African catfish, Clarias gariepinus, uridine diphosphoglucose dehydrogenase (UDPGD) and 3β-hydroxysteroid dehydrogenase (3β-HSD) appear in the granulosa of post-ovulatory follicles. In testes, both enzymes are present in interstitial cells. The combined presence of UDPGD and 3β-HSD points to the formation of steroid glucuronides at these sites. Interstitial cells between the tubules of the seminal vesicle also show 3β-HSD activity, both in captive fish and fish from nature. However, in these interstitial cells UDPGD activity was restricted to a few cells in the seminal vesicle of fish from nature. The latter enzyme was furthermore demonstrated in the epithelium of the seminal vesicle tubules, its activity being weaker in captive fish. Thus, in the seminal vesicle, glucuronidation of steroids may take place in interstitial cells, and it cannot be excluded that this process can also take place in the epithelium of the tubules

Exploring biophysical potential and sustainability of wheat cultivation in Uruguay at the national level

A methodology is presented that explores soil survey information at the national level (1:1 M), generating sustainability indicators for wheat cultivation in Uruguay. Potential yields were calculated for simplified crop production situations under several constraints, such as limitation of water availability calculated from soil physical properties and climatic conditions, and limitation of nutrient availability calculated from soil fertility and climatic conditions. Land quality sufficiency was examined by comparing these yields with the constraint-free yield conditioned only by solar radiation, temperature and the crop's photosynthetic properties. Crop growth was simulated only for areas suitable for the defined agricultural use. Model runs were repeated with inclusion of a topsoil loss scenario over 20 years as defined from an erosion risk analysis. Comparison between crop growth simulations for the two situations, gives an indication of the changes in land quality status, which supplies an indicator for agroecological sustainability. On the basis of crop growth simulation it is concluded that wheat production constraints in Uruguay appear to be mainly related to water availability limitations, while nutrient availability is near optimal for the suitable soils. The simulated loss of topsoil impacts most on soil physical properties, expressed in reduced water-limited yields. Soil fertility status, evaluated by change in nutrient-limited yields, was little affected by the scenari

Determination of the optimum standardised ileal digestible sulphur amino acids to lysine ratio in weaned pigs challenged with enterotoxigenic Escherichia coli

This experiment tested the hypothesis that pigs challenged with an enterotoxigenic strain of E. coli (ETEC) would require a higher sulphur amino acids (SAA) to Lys ratio (SAA:Lys). Pigs (n = 120) weighing 7.4 ± 0.52 kg (mean ± SD) and weaned at 27 d (Pietrain genotype, mixed sex) were stratified into 1 of 6 treatments based on weaning weight, sex and genotype for the F4 fimbria receptor (n = 20). Five diets were formulated with increasing ratios of standardised ileal digestible (SID) sulphurSAA:Lys. Pigs were housed in pens of 4 during an adaptation period of 6 d after which time pigs were housed individually. Pigs fed different SID SAA:Lys levels were infected with ETEC (5 mL, 1.13 × 108 CFU/mL, serotype O149:K91:K88) on d 8, 9, and 10 after weaning. The sixth diet, which contained 0.55 SID SAA:Lys and corresponded to current NRC recommendations, was allocated to 2 groups of pigs either with or without ETEC infection, and was considered as the infected or non-infected control group respectively. Pigs were fed Phase 1 diets (10.2 MJ NE, 1.2% SID Lys) ad libitum until d 15 after weaning. Phase 2 diets (10.2 MJ NE, 1.1% SID Lys) were fed ad libitum for the following three weeks. Diets did not contain any antimicrobial compounds. Corrected SID SAA:Lys determined based on analyzed amino acid content and the respective standardised ileal digestibility of ingredients were found to be 0.47, 0.55, 0.61, 0.69 and 0.77 for Phase 1 diets, and 0.47, 0.55, 0.63, 0.71 and 0.78 for Phase 2 diets. Following infection, oedema disease was diagnosed in all groups including the non-infection control group, therefore data from non-infected pigs were combined with pigs infected and fed 0.55 SAA:Lys for analysis of production and plasma data. There were no dietary effects of SID SAA:Lys on days with diarrhoea or faecal shedding of F4 ETEC (P > 0.05). Overall, average daily gain (ADG), feed intake and G:F were optimised at 0.71 (SE = 0.073), 0.73 (SE = 0.065) and 0.68 (SE = 0.090) SID SAA:Lys, respectively. For pigs infected with ETEC and not provided with antimicrobial compounds, and under conditions of the current study, it is suggested that the SID SAA:Lys lies above the current NRC recommendation of 0.55 for pigs after weaning

Seasonal changes in steroid metabolism in the male reproductive organ-system of the African catfish, Clarias gariepinus

Steroid and steroid glucuronide synthesis in feral male African catfish was investigated in vitro by incubating testes with [3H]-pregnenolone and seminal vesicles with [3H]-androstenedione. In testes, the capacity to form progestins, androgens, especially 11-oxygenated ones, and steroid glucuronides increased enormously in the periods of full spermatogenesis and breeding, with 5β-pregnane-3α,17α,20α-triol and 5β-pregnane-3α,17α-diol-20-one glucuronide as the main polar products. In the same periods, seminal vesicles are able to form 11-oxygenated androgens from [3H]-androstenedione and show an increased capacity to form testosterone. Their ability to produce testosterone glucuronide is strongly enhanced in the period of full spermatogenesis and further increases in the breeding period. In this latter period, the capacity to form 5β-androstane-3α,17α-diol glucuronide is also stimulated. The function of the main steroids and steroid glucuronides is discussed, with special reference to the water-soluble compounds that may serve as sex pheromones