The position of the epistatic S locus in the halothane linkage group in pigs

The linkage of the Phi, Pgd, Po2, S, H and halothane sensitivity loci was followed in a Belgian Landrace family, heterozygous for these systems over 6 generations. Recombination next to the S locus occurred mainly in pigs belonging to this particular family. From this investigation the position of the S locus is proved to be outwith the Phi-Pgd region, next to Phi . Therefore the gene sequence S - Phi - Hal -H- Po2 -Pgd is proposed. Higher recombination rates were observed in the female parental line of the multiheterozygous family when compared to the male parental line. Additional data from animals, unrelated to this strain, confirm the evidence of close linkage of the S system to the nearest marker loci.     

Multi-species response to rapid environmental change in a large estuary system: A biochronological approach

The sensitivity of species to environmental change is dependent on their ecological requirements (i.e. specialist v. generalist), and hence likely to be species-specific. Identifying species level variation in environmental sensitivity informs assessments of community vulnerability and assists in developing adaptive management strategies. We investigated species-specific sensitivity in fish to understand the vulnerability of differing life histories and ecological requirements to rapid environmental alteration (i.e. drought). Biochronologies of fish growth, based on increment widths in otoliths, were analysed using a mixed modelling approach. We assessed multi-decadal responses in fish growth to environmental variation in the terminal system of Australia’s largest river, for three long-lived fish species with differing life histories and ecological requirements: a freshwater specialist and two estuarine generalists. Biochronologies were between 20 and 38 years long, spanned a decade of severe drought and showed considerable inter-annual variation in growth. Precipitation influenced the growth of the obligate freshwater specialist, Macquaria ambigua ambigua. Temperature and salinity influenced the growth of the two estuarine generalists: Argyrosomus japonicus (estuarine opportunist) and Acanthopagrus butcheri (estuarine dependent), respectively. These results suggest that generalisations about how species respond to environmental change may mask species-specific responses to dependent on the constraints of their ecological requirements (i.e. specialist v. generalist). These findings also highlight the importance of considering the diversity of life history strategies that inhabit an ecosystem when developing conservation and management strategies.     

Historical shrub–grass transitions in the northern Chihuahuan Desert: modeling the effects of shifting rainfall seasonality and event size over a landscape gradient

We use a spatially explicit landscape model to investigate the potential role of rainfall on shrub–grass transitions in the Jornada Basin of southern New Mexico during the past century. In long‐term simulations (1915–1998) along a 2700 m transect running from a dry lake bed to the foothills of a small mountain, we test two hypotheses: (i) that wetter winters and drier summers may have facilitated shrub encroachment in grasslands, and (ii) that increases in large precipitation events may have increased soil water recharge at deeper layers, thus favoring shrub establishment and growth. Our model simulations generally support the hypothesis that wetter winters and drier summers may have played a key role, but we are unable to reproduce the major shifts from grass‐ to shrub‐domination that occurred in this landscape during the early part of the 1900s; furthermore, the positive shrub response to wetter winters and drier summers was only realized subsequent to the drought of 1951–1956, which was a relatively short ‘window of opportunity’ for increased shrub establishment and growth. Our simulations also generally support the hypothesis that an increase in the number of large precipitation events may also have favored shrub establishment and growth, although these results are equivocal, depending upon what constitutes a ‘large’ event and the timing of such events. We found complex interactions among (i) the amount/seasonality of rainfall, (ii) its redistribution in the landscape via run‐on and runoff, (iii) the depth of the soil water recharge, and (iv) subsequent water availability for the growth and reproduction of shrubs vs. herbaceous plants at various landscape positions. Our results suggest that only a mechanistic understanding of these interactions, plus the role of domestic cattle grazing, will enable us to elucidate fully the relative importance of biotic vs. abiotic factors in vegetation dynamics in this semiarid landscape.     

Population and pharmacogenetic studies on serum cholinesterase (E): estimates of theE 1 andE 2 allele frequencies for the population of Central Italy,and of the correlation between E activity and sensitivity to succinylcholine (SCC)

392 random patients treated with SCC prior to surgery were assayed for pseudocholinesterase activity and electrophoretic pattern. The estimate of the percent frequencies of theE ₁ ^a allele were 1.16±0.38 and of the C₅ (+) phenotype 9.7±1.5, both typical of Caucasian populations. By combining the presentE ₁ ^a gene frequency estimate with that from another sample of the same population (Cermele et al., 1987) a better estimate with smaller confidence limits was obtained, that is: 1,14±0,27. One subject interpreted asE ₁ ^a E ₁ ^a on phenotypic grounds was also found (expected 0,05) in this random sample. A correlation coefficient of −0.521 was found between E activity and myorelaxation time in the whole sample. High correlation values (r=−0.55 and r=−0.46) were found forE ₁ ^u E ₁ ^u ; C₅ (−) andE ₁ ^u E ₁ ^u ; C₅ (+) individuals, respectively, showing a strong dependence of the latter variable on the former one even within apparently homogeneous classes. The use of the product of these two variables as a classification criterion allowed the identification of a subject with very long myorelaxation time but normal activity.     

Glutathione status and sensitivity to GSH-reacting compounds of Escherichia coli strains deficient in glutathione metabolism and/or catalase activity

The intracellular concentrations of total glutathione, GSSG and protein · S-SG, the total excreted glutathione concentration, and the susceptibility towards GSH-reacting compounds were assayed in strains of Escherichia coli deficient in biosynthesis and/or reduction of glutathione. A deficiency in glutathione reductase displaced the glutathione status towards the oxidized forms. This displacement was more clearly appreciated in strains additionally deficient in glutathione biosynthesis. A deficiency in catalase activity also produced an increase in the oxidation of glutathione. The most severe changes were observed in the concentrations of protein-glutathione mixed disulfides and in the amount of glutathione excreted to the medium. Increased sensitivities towards compounds known to interact with cellular GSH were observed in glutathione reductase deficient strains, although these effects were enhanced in strains additionally deficient in GSH biosynthesis     

Genetic characterization of the mei-41 locus in Drosophila melanogaster

Summary The mutagen-sensitive mutant mus(1)104 ^D1 of Drosophila melanogaster maps to a position on the X chromosome very close to the meiotic mutant mei-41 ^D5 . Both mutants have been characterized as mutagen-sensitive and defective in post-replication repair. In the present report we show by complementation studies that mus(1)104 and mus(1)103 are allelic with mei-41. In addition, two reported alleles of mus(1)104 lie between the mei-41 alleles A10 and D5. The size of the mei-41 locus is estimated to be about 0.1 centimorgans (cM). Because several alleles of mei-41 have been shown to reduce recombination and increase meiotic chromosome loss and nondisjunction, mus(1)104 ^D1 females were examined for defects in meiosis. Although there was no evidence for reduced recombination on the second chromosome in homozygous mus(1)104 ^D1 females, heterozygous mus(1)104 ^D1 /mei-41 ^>D5 and mus(1)104 ^D1 /deficiency females showed reduced levels of recombination. However, there was no evidence of an increase in nondijunction in these females.We dedicate this article to the memory of Larry Sandler, who passed away suddenly on February 7, 1987     

Digitalis receptor sugar binding site characteristics: A model based upon studies of Na+, K+-ATPase preparations with differing digitalis sensitivities

The structure-activity relationships of the genin moieties of digitalis glycosides are commonly elucidated by determining the inhibitory potency of a variety of genins toward the plasma membrane Na⁺, K⁺-ATPase; qualitatively these relationships appear to be fairly independent of the specific Na⁺, K⁺-ATPase preparation utilized for the analysis. To determine whether this is the case with regard to the sugar moieties of glycosides, the inhibitory effects of 12 monoglycosides of digitoxigenin toward four Na⁺, K⁺-ATPase preparations of different origin were measured. It was found that while recognition of the major structural determinants of sugar activity appeared to be independent of enzyme source, recognition of the minor structural determinants of activity showed some source dependence. It was also observed that the intrinsic sensitivity to sugar potentiation may be source dependent and unrelated to intrinsic sensitivity to inhibition by digitoxigenin. These observations are compatible with a model of the Na⁺, K⁺-ATPase sugar binding site(s) in which intrinsic sensitivity to sugar attachment as well as recognition characteristics (for sugar structural features) both determine the extent to which a sugar moiety may contribute to the activity of monoglycosides. Further, in these studies one of the Na⁺, K⁺-ATPase preparations employed was obtained from rat brain, a tissue known to contain a mixture of ouabain sensitive and insensitive isoforms. We have observed that the rigorous purification techniques employed appear to have selectively removed from or denatured the less ouabain sensitive al isoform found in this enzyme preparation.     

Inhibited enzyme electrodes. Part 3: A sensor for low levels of H2S and HCN

It is shown that an inhibited enzyme electrode, using cytochrome oxidase, will respond to H₂S, HCN and azide ion. For all three inhibitors the kinetics of the inhibition and recovery processes have been analysed using the theoretical model presented previously (Albery et al., 1990a). Rearrangement of the differential equation describing inhibition and the development of the necessary software has enabled us to obtain values of the concentration of inhibitor in a matter of seconds after exposure of the sensor. The sensor will measure concentrations of H₂S down to 1 ppm in the gas phase and concentrations of HCN and azide ion down to 0·4 μmol dm⁻³ in the solution