Artificial placenta: two days of total extrauterine support of the isolated premature lamb fetus

A premature lamb fetus was totally sustained by extracorporeal perfusion with the use of a silicone-membrane blood oxygenator and parenteral nutritional support. The fetus remained in a metabolically stable state lasting several days.     

The chemical genomic portrait of yeast: uncovering a phenotype for all genes

Genetics aims to understand the relation between genotype and phenotype. However, because complete deletion of most yeast genes ( approximately 80%) has no obvious phenotypic consequence in rich medium, it is difficult to study their functions. To uncover phenotypes for this nonessential fraction of the genome, we performed 1144 chemical genomic assays on the yeast whole-genome heterozygous and homozygous deletion collections and quantified the growth fitness of each deletion strain in the presence of chemical or environmental stress conditions. We found that 97% of gene deletions exhibited a measurable growth phenotype, suggesting that nearly all genes are essential for optimal growth in at least one condition.     

Comparison of gene expression profiles of the jejunum of broilers supplemented with a yeast cell wall-derived mannan oligosaccharide versus bacitractin methylene disalicylate

1. The addition of yeast cell wall (YCW) mannan fractions or low concentrations of antibiotics to the diet of broilers positively affects gut health by improving intestinal cell morphology and improves feed efficiency and performance; however the exact mechanisms are unclear. Based on these production responses, the objective of this study was to compare the effects of supplementing YCW and bacitracin methylene disalicylate (BMD) in the diet on mRNA levels in the jejunum of 6-week-old broilers.

2. Dietary treatments were a maize-soya control diet and the control diet with the addition of YCW or BMD. Birds (n = 7) from each dietary treatment were randomly selected and killed at d 42. Whole jejunum (with serosa) samples were collected for RNA isolation. Gene expression analysis was performed using the AffymetrixGeneChip Chicken Genome Array (Santa Clara, CA, USA).

3. Supplementation with YCW resulted in 928 genes that were significantly changed (456 down-regulated, 472 up-regulated) and supplementation with BMD resulted in 857 genes that significantly changed (408 down-regulated, 449 up-regulated). In addition, 316 genes were significantly changed by both YCW and BMD (146 down-regulated, 170 up-regulated).

4. BMD increased the expression of genes involved in lipid and carbohydrate metabolism and decreased expression of genes associated with T-helper cell pathways. Gene expression profiles from birds fed on diets containing YCW showed changes on a genomic level that correspond to slower gut cell turnover and therefore increased energy preservation for growth.

5. In conclusion, supplementation with BMD or YCW had similar influences on the number of differentially expressed genes in the jejunum. Biological functions common to both YCW and BMD with positive activation scores included antiviral response and antimicrobial response. Genes that were affected by BMD or YCW classified into both different and common biological functions and pathways related to improved metabolism and health in the jejunum.     

The effect of stocking rate and calving date on grass production,utilization and nutritive value of the sward during the grazing season

A 2‐year whole‐farm system study compared the accumulation, utilization and nutritive value of grass in spring‐calving grass‐based systems differing in stocking rate (SR) and calving date (CD). Six treatments (systems) were compared over two complete grazing seasons. Stocking rates used in the study were low (2·5 cows ha^?1), medium (2·9 cows ha^?1) and high (3·3 cows ha^?1), respectively, and mean CDs were 12 February (early) and 25 February (late). Each system had its own farmlet of eighteen paddocks and one herd that remained on the same farmlet area for the duration of the study. Stocking rate had a small effect on total herbage accumulation (11 860 kg DM ha^?1 year^?1), but had no effect on total herbage utilization (11 700 kg DM ha^?1 year^?1). Milk and milk solids (MS; fat + protein) production per ha increased by 2580 and 196 kg ha^?1 as SR increased from 2·5 to 3·3 cows ha^?1. Milk production per ha and net herbage accumulation and utilization were unaffected by CD. Winter feed production was reduced as SR increased. Increased SR, associated with increased grazing severity, resulted in swards of increased leaf content and nutritive value. The results indicate that, although associated with increased milk production per ha, grazed grass utilization and improved sward nutritive value, the potential benefits of increased SR on Irish dairy farms can only be realized if the average level of herbage production and utilization is increased.     

Effects of in vitro brevetoxin exposure on apoptosis and cellular metabolism in a leukemic T cell line (Jurkat)

Harmful algal blooms (HABs) of the toxic dinoflagellate, Karenia brevis, produce red tide toxins, or brevetoxins. Significant health effects associated with red tide toxin exposure have been reported in sea life and in humans, with brevetoxins documented within immune cells from many species. The objective of this research was to investigate potential immunotoxic effects of brevetoxins using a leukemic T cell line (Jurkat) as an in vitro model system. Viability, cell proliferation, and apoptosis assays were conducted using brevetoxin congeners PbTx-2, PbTx-3, and PbTx-6. The effects of in vitro brevetoxin exposure on cell viability and cellular metabolism or proliferation were determined using trypan blue and MTT (1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan), respectively. Using MTT, cellular metabolic activity was decreased in Jurkat cells exposed to 5 – 10 μg/ml PbTx-2 or PbTx-6. After 3 h, no significant effects on cell viability were observed with any toxin congener in concentrations up to 10 μg/ml. Viability decreased dramatically after 24 h in cells treated with PbTx-2 or -6. Apoptosis, as measured by caspase-3 activity, was significantly increased in cells exposed to PbTx-2 or PbTx-6. In summary, brevetoxin congeners varied in effects on Jurkat cells, with PbTx-2 and PbTx-6 eliciting greater cellular effects compared to PbTx-3.     

Predation by seals on salmonids in two Scottish estuaries

Detailed observations of the behaviour of harbour seals, Phoca vitulina L., at sites within the estuaries of the Rivers Dee and Don, in north-eastern Scotland, were made over two full years between 1993 and 1996. Small numbers of grey seals, Halichoerus grypus Fab., were also present. The presence of seals within the estuaries was strongly related to season, with maximum numbers observed in winter and early spring; seals were virtually absent in June and July. The River Don was used largely as a haul-out site, while the River Dee was used predominantly as a foraging site, although it was not possible to determine whether the same seals were using the two estuaries. More seals were hauled-out on the River Don during twilight and dark than in daylight. The seals were observed to eat mostly salmonids, Salmo salar L. and S. trutta L., unidentified roundfish and flounder, Pleuronectes flesus L. The otoliths identified in scats collected at the mouth of the River Don belonged to marine species indicating that the seals were also feeding outside the estuaries. A minimum estimate is given of the numbers of large salmonids eaten in each river during the course of the year. Although no information was available on the numbers of salmonids using the rivers or the reproductive status of the fish eaten by the seals, as a cause of mortality, seal predation on large salmonids in estuaries is apparently an order of magnitude less important than mortality caused by angling within the river.     

Macronutrient (N, P, K) and Redoximorphic Metal (Fe, Mn) Allocation in Leersia oryzoides (Rice Cutgrass) Grown Under Different Flood Regimes

Vegetated drainages are an effective method for removal of pollutants associated with agricultural runoff. Leersia oryzoides, a plant common to agricultural ditches, may be particularly effective in remediation; however, research characterizing responses of L. oryzoides to flooding are limited. Soil reduction resulting from flooding can change availability of nutrients to plants via changes in chemical species (e.g., increasing solubility of Fe). Additionally, plant metabolic stresses resulting from reduced soils can decrease nutrient uptake and translocation. The objective of this study was to characterize belowground and aboveground nutrient allocation of L. oryzoides subjected to various soil moisture regimes. Treatments included: a well-watered and well-drained control; a continuously saturated treatment; a 48-h pulse-flood treatment; and a partially flooded treatment in which water level was maintained at 15 cm below the soil surface and flooded to the soil surface for 48 h once a week. Soil redox potential (Eh, mV) was measured periodically over the course of the 8-week experiment. At experiment termination, concentrations of Kjeldahl nitrogen, phosphorus (P), potassium (K), iron (Fe), and manganese (Mn) were measured in plant tissues. All flooded treatments demonstrated moderately reduced soil conditions (Eh < 350 mV). Plant Kjeldahl nitrogen concentrations demonstrated no treatment effect, whereas P and K concentrations decreased in aboveground portions of the plant. Belowground concentrations of P, Mn, and Fe were significantly higher in flooded plants, likely due to the increased solubility of these nutrients resulting from the reductive decomposition of metal–phosphate complexes in the soil and subsequent precipitation in the rhizosphere. These results indicate that wetland plants may indirectly affect P, Mn, and Fe concentrations in surface waters by altering local trends in soil oxidation–reduction chemistry.     

Roles of bootstrap resampling,measure of central tendency,and method for calculating thermal units when developing phenology models for pest management

The successful development of phenology models from field studies depends on many factors, some of which are entirely under the control of pest managers. For example, one such factor is the choice of method for calculating thermal units. In this study, we have demonstrated that four methods for calculating thermal units provided for acceptable predictions of one phenological event of one insect species, while another method for calculating thermal units did not. The measure of central tendency (mean or median) that is used to estimate lower developmental temperatures and required thermal summations is another factor that pest managers can control when developing phenology models from field studies. Here, we show that predictions that were made when using phenology models based on median lower developmental temperatures and median required thermal summations were superior to predictions that were made when using phenology models based on mean lower developmental temperatures and mean required thermal summations. The use of bootstrap vs. non-bootstrap estimates of lower developmental temperatures and required thermal summations is yet another factor that pest managers can control when developing phenology models from field studies. In this study, we found that calculating and using bootstrap estimates of lower developmental temperatures and required thermal summations in phenology models did not improve the predictions of one phenological event for one insect species. The implications of these and other findings are discussed.