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Biomedical subjects

M E Goddard

Publications and source records attributed to M E Goddard.

27 records · Page 2Linked to original sources
PubMed1987

A model of acute infectious neonatal diarrhoea.

Oral inoculation of neonatal MFI mice with enterotoxigenic strains of Escherichia coli that possessed the K99 or F41 antigen or both resulted in severe diarrhoea with high mortality. The diarrhoea was associated with increased fluid in the gut, greatly increased numbers of E. coli in gut homogenates and reduced weight gain compared to control animals. Further studies with strain B44 demonstrated greatly increased numbers of E. coli on the surface of the intestinal mucosa and haemo-concentration. The infection was transmissible between litter-mates. There was no evidence of invasion of the intestinal tissue of infected animals. Gnotobiotic Balb C mice and endotoxin-resistant mice were susceptible to oral inoculation with bovine enterotoxigenic E. coli strains, but neonatal rats were not susceptible to infection with enterotoxigenic E. coli strains B44 or 431. Porcine strains of E. coli that possessed K88 or 987P antigen did not infect neonatal MFI mice but an "atypical" porcine strain (431) which possessed both K99 and F41 antigens caused diarrhoea and a high mortality. The disease in neonatal mice resembled acute diarrhoea caused by these bacteria in other species, particularly the calf, and the model should be of value in assessing the efficacy of therapeutic agents.

Animals↗
PubMed1986

Assessment of heat stress in dairy cattle in Papua New Guinea.

The effects of breed (Friesian, AIS, Sindi-Sahiwal and Jersey), time of day (am v pm) and season of the year (hot or cool) on rectal temperature, pulse rate and respiratory rate were examined in the Highlands and Lowlands of Papua New Guinea. Two types of variation were investigated. Between-cow variation was the basis for the comparison of sites, seasons and breeds. Between-day variation was used to assess the effect of environmental temperatures on the animal parameters. Respiration rate and rectal temperature appeared more sensitive as indicators of heat stress than pulse rate and using these criteria the highlands climate was suitable for dairy cattle. Jerseys and Sahiwals showed lower respiratory rates compared with Friesians and AIS and their increase in rectal temperature during the day was less than the other two breeds but was not significantly so. The relationships between respiration rate and rectal temperature are discussed.

Animals↗
PubMed1979

Immunofluorescent studies of the local immune response in the mammary glands of rats.

Two irritants, phosphate-buffered saline and alcohol, and antigens including killed Brucella abortus, live B. abortus, Staphylococcus aureus, and rat parvovirus were separately infused into rat mammary glands during pregnancy, and by using immunofluorescent techniques, the numbers of immunoglobulin-containing cells in glands during lactation and involution were determined. The study provided basic information on the local immune response of the mammary gland to antigens of various types. In all experiments, the number of immunoglobulin M (IgM) cells present was small and no trends were apparent. IgA cells were always more prevalent than IgG cells. Fewer IgA cells were in the glands of rats infused with phosphate-buffered saline and alcohol than in normal rats. IgA cell prevalence was greatest in response to infusion of live B. abortus. Responses to live S. aureus and parvovirus were less pronounced, and infusion of killed B. abortus did not induce an elevation in IgA cell prevalence. IgG cell prevalence was greatest in response to infusion of live B. abortus or S. aureus and was decreasingly less pronounced in response to killed B. abortus and rat parvovirus. With the exception of parvovirus infusion, in regard to IgA cells, all glands locally infused with antigen had elevated IgA and IgG cell numbers when compared with noninfused glands in the same animal.

Animals↗
PubMedDate not supplied

The distribution of the effects of genes affecting quantitative traits in livestock.

Meta-analysis of information from quantitative trait loci (QTL) mapping experiments was used to derive distributions of the effects of genes affecting quantitative traits. The two limitations of such information, that QTL effects as reported include experimental error, and that mapping experiments can only detect QTL above a certain size, were accounted for. Data from pig and dairy mapping experiments were used. Gamma distributions of QTL effects were fitted with maximum likelihood. The derived distributions were moderately leptokurtic, consistent with many genes of small effect and few of large effect. Seventeen percent and 35% of the leading QTL explained 90% of the genetic variance for the dairy and pig distributions respectively. The number of segregating genes affecting a quantitative trait in dairy populations was predicted assuming genes affecting a quantitative trait were neutral with respect to fitness. Between 50 and 100 genes were predicted, depending on the effective population size assumed. As data for the analysis included no QTL of small effect, the ability to estimate the number of QTL of small effect must inevitably be weak. It may be that there are more QTL of small effect than predicted by our gamma distributions. Nevertheless, the distributions have important implications for QTL mapping experiments and Marker Assisted Selection (MAS). Powerful mapping experiments, able to detect QTL of 0.1sigma(p), will be required to detect enough QTL to explain 90% the genetic variance for a quantitative trait.

Animals↗
PubMedDate not supplied

Prediction of identity by descent probabilities from marker-haplotypes.

The prediction of identity by descent (IBD) probabilities is essential for all methods that map quantitative trait loci (QTL). The IBD probabilities may be predicted from marker genotypes and/or pedigree information. Here, a method is presented that predicts IBD probabilities at a given chromosomal location given data on a haplotype of markers spanning that position. The method is based on a simplification of the coalescence process, and assumes that the number of generations since the base population and effective population size is known, although effective size may be estimated from the data. The probability that two gametes are IBD at a particular locus increases as the number of markers surrounding the locus with identical alleles increases. This effect is more pronounced when effective population size is high. Hence as effective population size increases, the IBD probabilities become more sensitive to the marker data which should favour finer scale mapping of the QTL. The IBD probability prediction method was developed for the situation where the pedigree of the animals was unknown (i.e. all information came from the marker genotypes), and the situation where, say T, generations of unknown pedigree are followed by some generations where pedigree and marker genotypes are known.

Algorithms↗