Heteropaternal superfecundation frequently occurs in multiple-bearing mob-mated sheep

Heteropaternal superfecundation may be defined as the fertilisation of two or more ova during the same oestrus cycle as a result of more than one coital act from different males; this results in foetuses being born in the same litter of the same age but different paternity. Heteropaternal superfecundation is more likely to occur in poly-ovulatory species like sheep; moreover, female sheep are often mob-mated with several rams concurrently, thus providing an opportunity for a given female to be served by multiple males during the same oestrus cycle. The objective of the present study was to determine the frequency of heteropaternal superfecundation in six sheep flocks where most of the ewes, lambs and rams were genotyped. A total of 685 multiple-birth litters were available where the sire, dam and all lambs were genotyped. Of the 539 pairs of twins included in the analysis, 160 (i.e. 30%) were sired by two different rams. Of the 137 sets of triplets included in the analysis, 73 (i.e. 53%) were sired by more than one ram. Of the nine sets of quadruplets, eight were sired by two rams with the remaining litter being mono-paternal. The overall incidence of heteropaternal superfecundation among litters was therefore 35%. Given that the incidence of multiple births in these flocks was 65%, heteropaternal superfecundation is expected to be relatively common in sheep; this is especially true as all but two of the litter-mates were polyzygotic. Genotyping of progeny is one practical solution to identity such individuals.     

Science, politics, and public policy: a legislator's perspective.

Making judgments on priorities in funding is a politican's most difficult task. Scientific information is often necessary to make those judgments, so that good communication between scientist and politican is important. This is, however, difficult because the politician's usual training and working habits are different from those of the scientist. Messages to politicans must therefore be couched differently than in communications between scientists. These messages are more effective when they are concerned with the public need than when they plead for special interests. These messages are most effective when directed to those politicians serving on committees that must deal with the specified issue because Congress makes most political decisions through these committees. Committee members and committee staff members turn to scientists whom they know personally, so that getting to know the members of Congress and the key staff members of committees facilitates communication between science and public policy.     

Significance of Rh-sensitization during Pregnancy: Its Relation to a Preventive Programme

A study of the incidence of Rh-sensitization showed a 6.5% incidence of anti-D appearing for the first time during the last trimester of pregnancy. In 24 of the 29 subjects these antibodies were weak, and were found only when a sensitive technique using enzyme-treated Rh-deletion test cells was employed. The remaining five, however, had high-titre antibodies, which were associated with a positive Coombs test on cord blood.Rh-immune globulin administered at delivery resulted in disappearance of the anti-D in all but one of the subjects with weak antibody to whom it was given, suggesting that this treatment can reverse early sensitization. There was no effect when Rh-immune globulin was given to one subject with a high anti-D titre.Since sensitization has been found to occur frequently during the last trimester of pregnancy, an antenatal schedule of prophylaxis is advocated.     

Conditional Markov Chain Design for Accrual Clinical Trials

Randomization in a comparative experiment has, as one aim, the control of bias in the initial selection of experimental units. When the experiment is a clinical trial employing the accrual of patients, two additional aims are the control of admission bias and control of chronologic bias. This can be accomplished by using a method of randomization, such as the “biased coin design” of Efron, which sequentially forces balance. As an extension of Efron's design, this paper develops a class of conditional Markov chain designs. The detailed randomization employed utilizes the sequential imbalances in the treatment allocation as states in a Markov process. Through the use of appropriate transition probabilities, a range of possible designs can be attained. An additional objective of physical randomization is to provide a model for data analysis. Such a randomization theoretic analysis is presented for the current designs. In addition, Monte Carlo sampling results are given to support the proposed normal theory approximation to the exact randomization distribution.     

The diet of Eurasian Tree Sparrow Passer montanus nestlings in relation to agri-environment scheme habitats

It has been suggested by some authors that the UK agri-environment ‘wild bird seed’ option negatively impacts Tree Sparrow populations in the UK. Here we provide evidence for a change in nestling diet with increasing wild bird seed coverage and propose a possible mechanism for its negative impact on population trends.     

Minor Changes in Soil Bacterial and Fungal Community Composition Occur in Response to Monsoon Precipitation in a Semiarid Grassland

Arizona and New Mexico receive half of their annual precipitation during the summer monsoon season, making this large-scale rain event critical for ecosystem productivity. We used the monsoon rains to explore the responses of soil bacterial and fungal communities to natural moisture pulses in a semiarid grassland. Through 454 pyrosequencing of the 16S rRNA gene and ITS region, we phylogenetically characterized these communities at 22 time points during a summer season. Relative humidity increased before the rains arrived, creating conditions in soil that allowed for the growth of microorganisms. During the course of the study, the relative abundances of most bacterial phyla showed little variation, though some bacterial populations responded immediately to an increase in soil moisture once the monsoon rains arrived. The Firmicutes phylum experienced over a sixfold increase in relative abundance with increasing water availability. Conversely, Actinobacteria, the dominant taxa at our site, were negatively affected by the increase in water availability. No relationship was found between bacterial diversity and soil water potential. Bacterial community structure was unrelated to all environmental variables that we measured, with the exception of a significant relationship with atmospheric relative humidity. Relative abundances of fungal phyla fluctuated more throughout the season than bacterial abundances did. Variation in fungal community structure was unrelated to soil water potential and to most environmental variables. However, ordination analysis showed a distinct fungal community structure late in the season, probably due to plant senescence.