An examination of the molecular mechanisms controlling the tissue accumulation of conjugated linoleic acid (CLA) in cattle

End of project reportLong chain n-3 polyunsaturated fatty acids (n-3 PUFA) and conjugated linoleic acid (CLA) have demonstrable and potential human health benefits in terms of preventing cancer, diabetes, chronic inflammation, obesity and coronary heart disease. Supplementation of cattle diets with a blend of oils rich in n-3 PUFA and linoleic acid have a synergistic effect on the accumulation of ruminal and tissue concentrations of trans vaccenic acid (TVA), the main substrate for ?-9 desaturase which is responsible for de novo tissue synthesis of the cis 9, trans 11 isomer of CLA. This dietary strategy translates into increases in milk concentrations of CLA in dairy cows; however, concentrations in the muscle of beef animals have not always been increased. There is an apparent paradox in that n-3 PUFA supplementation enhances ruminal synthesis of trans-vaccenic acid (TVA), but then inhibits its conversion to CLA possibly through altering the activity of ?-9 desaturase. Recently, the promoter regions of the bovine ?- 9 desaturase gene has been isolated and analysed and has been shown to contain a conserved PUFA response region

Fatty Acid Composition and Eating Quality of Muscle from Steers Offered Grazed Grass, Grass Silage or Concentrate-Based Diets

The effects of grazed grass, grass silage or concentrates on the eating quality and fatty acid composition of intra-muscular fat of steers fed to achieve similar carcass growth rates were investigated. Fifty steers were assigned to one of five dietary treatments. The experimental rations offered daily for 85 days pre-slaughter were (a) grass silage plus 4 kg concentrate, (b) 8 kg concentrate plus 1 kg hay, (c) 6 kg grazed grass dry matter (DM) plus 5 kg concentrate, (d) 12 kg grazed grass DM plus 2.5 kg concentrate or (e) 22 kg grazed grass DM. Decreasing the proportion of concentrate in the diet, which effectively increased grass intake, caused a linear decrease in the concentration of intra-muscular saturated fatty acids (SFA) (P \u3c .01) and in the n-6 to n-3 poly-unsaturated fatty acids (PUFA )ratio (P\u3c .001) and a linear increase in the PUFA to SFA ratio (P \u3c .01) and the conjugated linoleic acid concentration (P \u3c .001). There was an interaction (p\u3c 0.05) between ageing time and treatment with treatment d having higher (p\u3c 0.05) tenderness, texture and acceptability values after 2 days ageing, but not after 7 or 14 days ageing. The data indicate that intramuscular fatty acid composition of beef can be improved from a human health perspective by inclusion of grass in the diet without any negative effect on the eating quality

The Effects of Disturbance Architecture on Landscape-Level Population Dynamics

Phenomena such as disturbance play a major role in structuring ecological systems by producing a spatiotemporal mosaic of patches at different successional states. The distribution of species within the resulting mosaic depends upon an interaction between species\u27 life history traits and the spatial and temporal structure of the ecological processes controlling species\u27 distributions. We have used a spatially explicit simulation model (Jasper) of a serpentine grassland to examine the importance of some of these relationships, focusing primarily on the role of disturbance. The model Jasper is hierarchical in design and was developed to simulate the population dynamics of three interacting plant species: Bromus mollis, Calycadenia multiglandulosa, and Plantago erecta. Population dynamics were modeled as occurring within local sites, which were then arranged in a square array to form a landscape. Connections among sites within a landscape were made primarily through seed dispersal. Several components of disturbance architecture were varied systematically among model runs to determine their impact on population dynamics at the scale of the landscape. We considered three levels of organization in modeling disturbance: (1) overall rate of disturbance, (2) size of individual disturbances, and (3) temporal and spatial autocorrelation among individual disturbances. The results demonstrate that the impact of disturbance depends upon a complex interaction between the life history characteristics of the species making up the community and the spatial and temporal structure of the disturbance regime. For example, we found that the biggest impact on species abundance occurred in response to a shift in the temporal autocorrelation structure of the disturbance regime. Also, species diversity was found to increase at intermediate levels of disturbance (as has been shown in several other studies). However, what can be considered an intermediate level of disturbance depends as much upon the temporal autocorrelation structure of the disturbance regime as it does upon the absolute rate of disturbance. These results suggest that predicting the impact of disturbance on ecological communities will require an explicit understanding of at least some aspects of the spatial and temporal architecture of the disturbance regime

Analogue Gravity and ultrashort laser pulse filamentation

Ultrashort laser pulse filaments in dispersive nonlinear Kerr media induce a moving refractive index perturbation which modifies the space-time geometry as seen by co-propagating light rays. We study the analogue geometry induced by the filament and show that one of the most evident features of filamentation, namely conical emission, may be precisely reconstructed from the geodesics. We highlight the existence of favorable conditions for the study of analogue black hole kinematics and Hawking type radiation.Comment: 4 pages, revised versio

Progress towards marine ecosystem observing systems in South Africa

Marine ecosystem observing systems combine measurements, observations and models through a data management and interpretation process to provide information on the status of marine ecosystems. Both biotic and abiotic aspects of the marine environment need to be considered. Single variables typically can be used to represent aspects of the physical and chemical environment, but ecosystem indicators are required for the living components. There are no true marine ecosystem observing systems globally, because most observing systems focus on the physical environment. In South Africa, some fledgling systems are being developed, using the knowledge base provided by focused marine ecosystem research over the past 30 years. Further development should be based on international guidelines, which highlight three interrelated elements : (i) Measurements, obtained directly from ships, drifters or buoys, or remotely from satellites. In South Africa, sustained, long-term measurements are hampered by limited available ship's time, lack of suitable instruments, and insufficient qualified personnel. (ii) Models and other analytical tools to augment observations. South Africa is making progress in marine modelling, but not in marine data assimilation; qualified persons need to be attracted, trained and retained. (iii) Archived and disseminated data generated from measurements and models. The infrastructure and human and institutional capacity for data management and communication in South Africa needs to be enhanced. Existing programmes contribute towards the development of an effective marine ecosystem observing system, but its sustainability requires support at an institutional level

On the generation and the nonlinear dynamics of X-waves of the Schroedinger equation

The generation of finite energy packets of X-waves is analysed in normally dispersive cubic media by using an X-wave expansion. The 3D nonlinear Schroedinger model is reduced to a 1D equation with anomalous dispersion. Pulse splitting and beam replenishment as observed in experiments with water and Kerr media are explained in terms of a higher order breathing soliton. The results presented also hold in periodic media and Bose-condensed gases.Comment: 18 pages, 6 figures, corrected version to be published in Physical Review