Intrinsic vs. extrinsic influences on life history expression: metabolism and parentally induced temperature influences on embryo development rate

Intrinsic processes are assumed to underlie life history expression and trade‐offs, but extrinsic inputs are theorised to shift trait expression and mask trade‐offs within species. Here, we explore application of this theory across species. We do this based on parentally induced embryo temperature as an extrinsic input, and mass‐specific embryo metabolism as an intrinsic process, underlying embryonic development rate. We found that embryonic metabolism followed intrinsic allometry rules among 49 songbird species from temperate and tropical sites. Extrinsic inputs via parentally induced temperatures explained the majority of variation in development rates and masked a relationship with metabolism; metabolism explained a minor proportion of the variation in development rates among species, and only after accounting for temperature effects. We discuss evidence that temperature further obscures the expected interspecific trade‐off between development rate and offspring quality. These results demonstrate the importance of considering extrinsic inputs to trait expression and trade‐offs across species.     

A Survey Investigating the Infection of Fusarium langsethiae and Production of HT‐2 and T‐2 Mycotoxins in UK Oat Fields

Fusarium langsethiae is a toxigenic fungal species that has been reported in European small‐grain cereal crops such as oats, wheat and barley. Although its relative contribution to fusarium head blight (FHB) symptoms is not well understood, it is reported to contaminate these cereals with high levels of HT‐2 and T‐2 trichothecenes mycotoxins that are currently under consideration for legislation by the European Commission. Ten commercial oat fields in Shropshire and Staffordshire (two adjacent counties in the Midlands) in the UK were surveyed in the 2006/2007 growing season. Samples were taken from predetermined field locations at Zadoks growth stages 32/33, 69, 77‐85 and 90‐92 for F. langsethiae biomass and HT‐2 and T‐2 toxins quantification. The results from this study showed that oats can be heavily infected with F. langsethiae and have high concentrations of HT‐2 and T‐2 toxins with no apparent FHB symptoms. The regression of HT‐2 + T‐2 toxins on F. langsethiae DNA concentration was highly significant (P < 0.001, r² = 0.55). The results indicated that although F. langsethiae had no direct effect on crop yield, it may result in indirect economic losses where the grain can be rejected or downgraded as a result of intolerable levels of HT‐2 and T‐2 toxins, which are of human food and animal feed safety concern. The influence of cultural field practices on the infection and HT‐2 and T‐2 toxins accumulation in oats was not clear and warrants further studies to identify the sources of F. langsethiae inoculum and conditions favourable for infection and mycotoxin production.     

Trace element transfer from alginate dressings to wounds

ABSTRACT

A method has been developed for impregnating alginate-based wound dressings with trace elements required for wound healing and for quantifying the transfer from these dressing to wound fluid (for which a substitute—blood serum—was used in these experiments). Under ideal conditions, up to 85% can be carried across from the tow to the wound fluid.     

On Testing Equality of Means of Correlated Variates with Incomplete Data

A statistic is proposed for testing the hypothesis of equality of the means of a bivariate normal distribution with unknown common variance and correlation coefficient when observations are missing on one of the variates. Expressions for the second and fourth central moments of the statistic are obtained. These moments are used to approximate the distribution of the statistic by a Student's t distribution under the null hypothesis. The powers of the test are computed and compared with those of the conventional paired t and the other known statistics.     

On Comparing Correlated Means in the Presence of Incomplete Data

Two statistics are proposed for testing the hypothesis of equality of the means of a bivariate normal distribution with unknown common variance and correlation coefficient when observations are missing on both variates. One of the statistics reduces to the one proposed by Bhoj (1978, 1984) when the unpaired observations on the variates are equal. The distributions of the statistics are approximated by well known distributions under the null hypothesis. The empirical powers of the tests are computed and compared with those of some known statistics. The comparison supports the use of one of the statistics proposed in this paper.     

Construction of Partially Balanced Incomplete Block Designs with Nested Rows and Columns

A number of methods of construction of partially balanced incomplete block designs with nested rows and columns are developed and new balanced incomplete block designs with nested rows and columns are obtained as a by-product.     

Subunit composition of a high molecular weight oligomer: Limulus polyphemus hemocyanin

The hemocyanin of Limulus polyphemus is a 48-subunit aggregate. This 3.3 × 10⁶-dalton oligomer is composed of structurally and functionally heterogeneous subunits. Using polyacrylamide electrophoresis J. Markl, A. Markl, W. Schartau, and B. Linzen (J. Comp. Physiol. Ser. B130,283–292, 1979) observed 12 bands; while using immunoelectrophoresis, M. Hoylaerts, G. Preaux, R. Witters, and R. Lontie (Arch. Int. Physiol. Biochem.87, 417–418, 1979) and J. Lamy, J. Lamy, J. Weill, J. Bonaventura, C. Bonaventura, and M. Brenowitz. (Arch. Biochem. Biophys.196, 324–339, 1979) observed 8 subunits. To proceed with an analysis of subunit roles in assembly it is first necessary to determine the number of distinct subunits. Refinement of the chromatographic separation procedures has led to the isolation of 8 immunologically distinct subunits as well as additional charge isomers which cannot be distinguished immunologically. Alkaline electrophoresis revealed 15 bands and isoelectric focusing up to 17. On the basis of extensive control experiments, including composit acrylamide-agarose immunoelectrophoresis and checks for conformational isomers, aggregation, proteolysis, and other types of degradation, we conclude that the electrophoretic heterogeneity of immunologically identical subunits is not artifactual. We have extended the nomenclature used by Lamy et al. (1979) to include the electrophoretic heterogeneity by using primes (′) to denote electrophoretically distinguishable subunits which are immunologically identical. A number of patterns have become apparent by correlating the results obtained by the different techniques. For example, immunologically pure subunit II, which shows 3 bands on alkaline electrophoresis, is in fact a mixture of electrophoretically distinct subunits II, II′, II″. Except for subunits II, II′, and II″ immunoelectrophoretically identical subunits are typically homogeneous on sodium dodecyl sulfate-gels. However, slight differences in the apparent molecular weight are observed on high-resolution gels between immunologically unrelated subunits. The immunological identity and electrophoretic differences suggest that the charge isomers which are immunologically identical have similar antigenic surfaces. If a charge substitution is not in a critical location, we would expect the electrophoretically distinct but immunologically identical subunits to have identical assembly roles. Comparison of the results for Limulus hemocyanin with the hemocyanin of related species Eurypelma californicum and Androctanus australis, which have 7 and 8 immunologically distinct subunits, respectively, suggests that the calcium-mediated aggregation from 24 to 48 subunits of Limulus does not require more extensive subunit complexity.     

Electrophysiological evidence for the autoregulation of β-cell secretion by insulin

Electrophysiological studies of cultured rat pancreatic β-cells using intracellular microelectrodes show that exogenous insulin over the range of 0.1–10.0 μg/ml inhibits the electrical activity due to 27.8 mM glucose in a dose-related manner. This inhibitory effect is manifested by a mean increase of the membrane potential from about ?20 to ?30 mV and inhibition of the manner of cells impaled showing spike activity from 60 to less than 10%. The inhibitory influence of insulin is rapid occuring within 5 min for the highest level used. The results provide evidence for a negative feedback role of insulin in regulating its own release.