Transformation of QTL genotypic effects to allelic effects

The genotypic and allelic effect models are equivalent in terms of QTL detection in a simple additive model, but the QTL allelic model has the advantage of providing direct information for marker-assisted selection. However, the allelic matrix is four times as large as the genotypic IBD matrix, causing computational problems, especially in genome scans examining multiple positions. Transformation from genotypic to allelic effects, after estimating the genotypic effects with a smaller IBD matrix, can solve this problem. Although the validity of transformation from genotypic to allelic effects has been disputed, this work proves that transformation can successfully yield unique allelic effects when genotypic and allelic IBD matrixes exist.     

Random effects in population models with hereditary effects

This paper discusses the influence of environmental noise on the dynamics of single species population models with hereditary effects. A detailed analysis is carried out for the logistic equation with discrete delay in the resource limitation term (Hutchinson's equation). When the system undergoes Hopf bifurcation, we find the stationary probability density distribution for the amplitude of the periodic solution by means of an averaged Fokker-Planck equation. Finally, we estimate the persistence time of the species when the population density has a lower bound beyond which it goes extinct.     

Maternal effects, paternal effects and sexual selection

Maternal and paternal effects can lead to complicated evolutionary dynamics, including evolution in the opposite direction to selection. Recent studies demonstrate that parental effects on sexually selected traits, as well as preferences for those traits, might be large. Although these findings are likely to have consequences for both the evolutionary dynamics and equilibria of sexual selection, theory is lacking. Because parents are expected to maximize their own fitness, rather than that of a specific offspring, the magnitude (and even direction) of parental effects are context dependent. By extension, this dynamic nature of parental effects might help to explain the maintenance of variation in many sexually selected traits.     

Arrhenius curves of hydrogen transfers: tunnel effects, isotope effects and effects of pre-equilibria

In this paper, the Arrhenius curves of selected hydrogen-transfer reactions for which kinetic data are available in a large temperature range are reviewed. The curves are discussed in terms of the one-dimensional Bell-Limbach tunnelling model. The main parameters of this model are the barrier heights of the isotopic reactions, barrier width of the H-reaction, tunnelling masses, pre-exponential factor and minimum energy for tunnelling to occur. The model allows one to compare different reactions in a simple way and prepare the kinetic data for more-dimensional treatments. The first type of reactions is concerned with reactions where the geometries of the reacting molecules are well established and the kinetic data of the isotopic reactions are available in a large temperature range. Here, it is possible to study the relation between kinetic isotope effects (KIEs) and chemical structure. Examples are the tautomerism of porphyrin, the porphyrin anion and related compounds exhibiting intramolecular hydrogen bonds of medium strength. We observe pre-exponential factors of the order of kT/h congruent with 10(13) s-1 corresponding to vanishing activation entropies in terms of transition state theory. This result is important for the second type of reactions discussed in this paper, referring mostly to liquid solutions. Here, the reacting molecular configurations may be involved in equilibria with non- or less-reactive forms. Several cases are discussed, where the less-reactive forms dominate at low or at high temperature, leading to unusual Arrhenius curves. These cases include examples from small molecule solution chemistry like the base-catalysed intramolecular H-transfer in diaryltriazene, 2-(2'-hydroxyphenyl)-benzoxazole, 2-hydroxy-phenoxyl radicals, as well as in the case of an enzymatic system, thermophilic alcohol dehydrogenase. In the latter case, temperature-dependent KIEs are interpreted in terms of a transition between two regimes with different temperature-independent KIEs.     

X chromosome effects and their interactions with mitochondrial effects

We report a simple and rapid method for detecting additive genetic variance due to X-linked loci in the absence of marker data for this chromosome. We examined the interaction of this method with an established method for detecting mitochondrial linkage (another source of sex-asymmetric genetic covariance). When applied to data from the Collaborative Study on the Genetics of Alcoholism, this method found evidence of X-chromosomal linkage for one continuous trait (ntth1) and one discrete trait (SPENT). Evidence of mitochondrial contribution was found for one discrete trait (CRAVING) and three continuous traits (ln(CIGPKYR), ecb21, and tth1). Results for ntth1 suggest that methods that do not also allow for male-female heterogeneity in environmental variance may be overly conservative in detection of X-chromosomal effects.     

Gastric effects and side effects of synthetic secretin in man

The gastric effects of synthetic secretin given in a depot reparation as subcutaneous injection or in different doses as intravenous infusion were studied in 10 healthy volunteers. Peptone-stimulated gastric acid secretion and serum gastrin were significantly suppressed with a clear dose-response inhibition of acid output. There was a significant correlation between percentage inhibition of acid secretion and plasma secretin concentrations which were greatly above those seen physiologically. Serum lipase and trypsin increased significantly. Most subjects lost fluid from diuresis and diarrhoea, so that serum sodium and total protein concentrations also increased significantly. These side effects cast doubt on the clinical value of prolonged infusions of pharmacological doses of synthetic secretion in critically ill patients.     

Butterfly effects.

Concerns about the potential toxicity of pollen from genetically modified maize on neighbouring butterflies prompted urgent studies, reports Nigel Williams.     

Antineoplastic effects of carnosine and beta-alanine--physiological considerations of its antineoplastic effects

Antineoplastic effects of carnosine (CAR) and beta-alanine (ALA), were examined in vivo using ddY mice implanted with the solid tumor Sarcoma-180. The sarcoma was treated with trypsin, 10(5) cells were implanted subcutaneously in the back of the animals, and CAR and ALA were administered subcutaneously 2 cm from the implantation site starting on the next day. The animals treated with ALA alone showed prolongation of survival to a T/C value of 132%; the growth of the tumor was inhibited and mortality reduced in those treated with CAR alone. Regression of the tumor was observed in the animals treated with either drug. The effects of these agents were enhanced when administered in combination with the non-specific active immuno-enhancing agent OK-432. More than half the animals treated with CAR and OK-432 survived the observation period (T/C greater than 218%), and survival was prolonged in those treated with ALA and OK-432 to a T/C value of 132%. The agents also showed potent antineoplastic effects on Sarcoma-180 when the tumor had been attenuated in vivo with mitomycin C (MMC).     

Two types of magnetic biological effects: individual and batch effects

Frequency distributions of the magnetic effects values have been calculated based on the results of about 120 thousand single trials during psychophysical testing of 40 people under normal conditions and exposure to the hundredfold weakened geomagnetic field. Two types of such distributions were shown to be attributed to a) the individual reactions to the change of a magnetic field and b) the batch magnetic effect on the set of the individual reactions. The methodological consequences significant for detecting magnetic biological phenomena and studying their nature are discussed.