Meteorological factors and the time of onset of chest pain in acute myocardial infarction

Analysis of the time of onset of chest pain in 2254 patients with a myocardial infarction admitted to a coronary care unit in Leicester during a 10-year period shows an association with temperature and humidity. During both the most cold and humid times of the year, the relationship is a strong one. A generalized linear model with a log link was used to fit the data and the backward elimination selection procedure suggested a humid, cold day might help to trigger the occurrence of myocardial infarction. In addition, cold weather was found to have a stronger effect on the male population while those men aged between 50 and 70 years were more sensitive to the effect of high humidity.     

Distribution and breeding biology of offshore cichlids in Lake Malawi/ Niassa

Synopsis Lake Malawi/Niassa is the second largest rift valley lake in Africa, with an area of 28 800 km², and an average and maximum depth of 292 m and>700 m, respectively. The lake is well known for the great diversity of fish occurring in the inshore zone. However, the offshore fish community is poorly documented. To rectify this, regular sampling was undertaken over two years, using trawl and gillnets at six offshore locations. This paper reports on the species composition, spatial distribution and breeding biology of the dominant cichlids species from the offshore pelagic zone. Cichlids formed approximately 88% of the offshore fish biomass. Most abundant were two species of zooplanktivores in the genus Diplotaxodon that made up 71% of the offshore fish biomass. An undescribed species, given the cheironym D. bigeye, was mainly found at a depth of 220 m during the day, but moved into near surface waters at night when the moon was full. This species was absent from the shallow regions of the lake. The most abundant offshore species was D. limnothrissa, which was distributed evenly throughout the lake to depths of 220 m. A less common offshore zooplanktivore was Copadichromis quadrimaculatus that formed 5% of the biomass and was confined to the upper 100 m of the water column. The main piscivores were in the genus Rhamphochromis and formed approximately 10% of the offshore fish biomass. The two dominant taxa were R. longiceps and the large Rhamphochromis group, and both were more common in the southern half of the lake. The former occurred mainly in the upper 100 m of the water column and the latter mainly at depths of 100–150 m. The length at maturity and fecundity for the dominant offshore species were estimated and seasonal breeding cycles determined from gonad activity and gonado-somatic indices.     

Evolutionary ecology and the conservation of biodiversity

Studies on evolving interactions among species and the coevolutionary process have suggested that the conservation of biodiversity requires a broad geographic perspective, if the `interaction biodiversity' of the earth is to be conserved with its species diversity. Continued maintenance of the geographic mosaic of specialization, defense and population structure appears to be crucial to the coevolutionary process and the long-term persistence of some interspecific interactions.     

The analysis of the NSW wheat variety database. I. Modelling trial error variance

The retrospective analysis of a large database on wheat variety testing in New South Wales (NSW) is considered. This analysis involved three key steps. Initially error variance heterogeneity is modelled, indicating significant differences in error variance due to trial location, year of trialling, sowing date and trial mean yield. The implication of this modelling for the estimaion of variance components is discussed.     

The Probability Distribution of the Amount of an Individual''s Genome Surviving to the following Generation

The probability that at least p% of an individual's genome is passed on collectively to his children is calculated. With data availability the consideration of the chromosome as a whole rather than discrete loci becomes of increasing practical importance. Assuming the genomic continuum model, which allows for recombination, the crossover process in a chromosome pedigree is viewed as a continuous-time Markov random walk on the vertices of a hypercube with time parameter map distance along the chromosome. The desired probability corresponds to the probability of sojourn times of the process in a small set of vertices, which are well approximated via the Poisson clumping heuristic. Results are given for the human genome. It is very likely that an individual with at least four children passes on at least 90% of his genome. There exists no ``equivalent' number of independently segregating loci for this distribution.     

Fluoranthene as a model toxicant in sediment studies with Chironomus riparius

The bioavailability of fluoranthene (as a model toxicant) in freshwater sediment tests with Chironomus riparius was investigated in relation to the partitioning of the chemical between water and sediment. Effects on survival and successful development of newly hatched larvae through to adult emergence were measured over a range of sediment concentrations. Radiolabelled fluoranthene was employed to enable sediment, aqueous and tissue concentrations to be determined. A significant effect on emergence was obtained at a measured sediment concentration of 80 mg kg^-1 (dry weight). The measured concentration in the overlying water was 88 g l^-1. Although effects at 170 mg kg^-1 (dry weight) were more severe, the measured concentration in the overlying water was similar (89 g l^-1), probably reflecting the approach towards the solubility limit. Bioaccumulation of fluoranthene, determined by analysis of emerging adults, was approximately proportional to the sediment concentration. Although the aqueous phase concentration appeared to be the principal factor controlling bioavailability, the increasing toxicity, when water concentrations had reached a plateau, suggested that other mechanisms may also be involved. Different sediment spiking procedures resulted in broadly similar partitioning of the chemical between the sediment and the overlying water. There were only minor differences in toxicity between the procedures, two of which allowed the carrier solvent used for spiking to be eliminated before addition of the test organisms. It was concluded that, for most purposes, all four procedures were equally acceptable, and by retaining a flexible approach, even for standardised regulatory tests, spiking procedures may be tailored to the physico-chemical properties of the test material.     

Whisker-mediated plant transformation: An alternative technology

A number of different methods, involving direct DNA delivery are now available for plant transformation. Here we review the most recently developed technique which involves the mixing of silicon carbide whiskers with plant cells and plasmid DNA. Fertile transgenic plants have now been produced using whisker-mediated transformation, and this method can now be considered as a simple, inexpensive alternative for plant transformation. A brief review on transformation of animal cells andChlamydomonas using whiskers technology is also included.     

Scaffold attachment regions stimulate HSP70.1 expression in mouse preimplantation embryos but not in differentiated tissues.

Eukaryotic interphase chromatin is thought to be organized into topologically discrete, independent domains acting as units upon which differential patterns of gene expression are established. Sequences which attach chromatin to in vitro preparations of a nucleoprotein matrix (scaffold attachment regions [SARs]) may act as domain boundaries, but their role remains poorly defined compared with those of other elements such as locus control regions. We have produced mice homozygous for a transgene which is transcribed as early as the activation of the embryonic genome at the two-cell stage and which is expressed ubiquitously in a number of differentiated tissues. Transgenic lines were generated in the presence or absence of flanking SAR sequences, creating an original model which enabled us to examine the effects of these elements at different developmental stages. In the preimplantation mouse embryo, flanking SARs stimulated transgene expression in a copy-dependent manner. In contrast, in the differentiated tissues of newborn and adult mice, no significant SAR-dependent increase in transgene expression was found, correlation with copy number was lost, and position effects were observed. These results suggest a limited capacity of SARs to act as insulating elements but are consistent with a proposed model of SAR-mediated chromatin opening and closing.     

Flow cytometric evaluation of boar semen by the sperm chromatin structure assay as related to cryopreservation and fertility

Boar semen from a heterospermic mating trial and semen cryopreserved by various methods were evaluated by the flow cytometric sperm chromatin structure assay (SCSA), which measures the susceptibility of sperm nuclear DNA to acid-induced denaturation in situ. Spermatozoa were treated with a pH 1.4 buffer and then stained with the metachromatic dye acridine orange. Acridine orange intercalated into double-stranded DNA (native) fluoresces green while single-stranded DNA (denatured) fluoresces red when excited with 488 nm light. The ratio of red to total fluorescence provides an index of normality/abnormality. The SCSA data on neat boar semen or semen in either Kiev-Merck or Pursel-Johnson extender and frozen directly on dry ice blocks or plunged into LN(2) did not differ within individual boars. Therefore, chromatin structure, as measured by the SCSA, was not influenced differently by these 2 methods of semen cryopreservation. When semen from 6 boars was mixed in equal sperm numbers in six 3-way combinations and inseminated into at least 3 Duroc gilts per combination, 4 of the 6 combinations yielded 2 litters, while the remaining 2 combinations yielded 3 litters. The SCSA correctly predicted both the high and low fertility boars based on a ratio of offspring as deviated from the theoretical percentage. Thus, the SCSA was found to be a valuable adjunct method for evaluating boar cemen quality.