Assessing the impact of episodic pollution

The increased tightening of controls on industrial and municipal wastewater discharges has resulted in steady improvements in the quality of many important rivers over recent years. However, episodic pollution, particularly from farm wastes and combined sewer overflows continues to pose a major problem, and is one of the main causes of poor quality rivers today. Despite our acknowledgement of this continuing problem, very little is known of the mechanistic basis of responses and recovery of aquatic organisms and communities exposed to intermittent pulses of common pollutants. The majority of ecotoxicological studies to date have been concerned with the effects of continuous exposure. Although such studies may provide a means of predicting the impact of episodic pollution events, a more appropriate test design would be to assess toxicity under pulsed and fluctuating exposure. Studies should also include a post-exposure observation period and should consider recovery of individuals and communities. This paper reviews the results of reported studies relevant to the investigation of episodic pollution and pays particular attention to the effects of magnitude, duration and frequency of exposure. Results of field investigations using an in situ bioassay technique are also presented to emphasize the importance of field validation of proposed water quality criteria for intermittent pollution events.     

IgA deficiency during treatment of infantile hypothyroidism with thyroxine.

Serum IgA concentrations in five children with infantile hypothyroidism fell soon after the start of treatment with thyroxine. In one child the IgA concentration fell appreciably (to less than 0.01 g/1) and remained reduced; in the four others it returned to normal. IgM and IgG concentrations were roughly normal throughout. The deficiency in IgA concentrations may have been due to stimulation by thyroxine treatment of a T cell suppressor system that, in the original hypothyroid state, was less than normally active.     

Oestrous and ovarian activity in a female jaguar (Panthera onca).

The mean +/- s.e.m. duration of oestrus was 12.0 +/- 1.0 days (n = 7) and the oestrous cycle length was 47.2 +/- 5.4 days (n = 6) for a captive jaguar. Ovulation did not occur spontaneously, but was induced by treatment with hCG or LH-RH.     

Chromosome Interactions in DROSOPHILA MELANOGASTER. II. Total Fitness

In a large experiment, using nearly 200 population cages, we have measured the fitness of Drosophila melanogaster homozygous (1) for the second chromosome, (2) for the third chromosome, and (3) for both chromosomes. Twentyfour second chromosomes and 24 third chromosomes sampled from a natural population were tested. The mean fitness of the homozygous flies is 0.081 ± 0.014 for the second chromosome, 0.080 ± 0.017 for the third chromosome, and 0.079 ± 0.024 for both chromosomes simultaneously. Assuming that fitnesses are multiplicative (the additive fitness model makes no sense in the present case because of the large selection coefficients involved), the expected mean fitness of the homozygotes for both chromosomes is 0.0066; their observed fitness is more than ten times greater. Thus, it appears that synergistic interactions between loci are considerable; and that, consequently, the fitness function substantially departs from linearity. Two models are tentatively suggested for the fitness function: a "threshold" model and a "synergistic" model.—The experiments reported here confirm previous results showing that the concealed genetic load present in natural populations of Drosophila is sufficient to account for the selective maintenance of numerous polymorphisms (of the order of 1000).     

Sensitivity to weighting in life cycle impact assessment (LCIA)

The International Journal of Life Cycle Assessment - Weighting in life cycle assessment (LCA) incorporates stakeholder preferences in the decision-making process of comparative LCAs. Research...     

Parallel synthesis of N-biaryl quinolone carboxylic acids as selective M1 positive allosteric modulators

An iterative analog library synthesis approach was employed in the exploration of a quinolone carboxylic acid series of selective M₁ positive allosteric modulators, and strategies for improving potency and plasma free fraction were identified.     

Fused heterocyclic M1 positive allosteric modulators

Fused aromatics such as naphthalene were identified as highly potent and CNS penetrant M₁ positive allosteric modulators during an SAR study to replace the phenyl B-ring linkage.     

Pregnancy in the domestic cat after artificial insemination with previously frozen spermatozoa

Methods for collection, freeze preservation and artificial insemination of domestic cat semen were developed. Total sperm count and pre-freeze and post-thaw percent motility were significantly greater (P is less than 0.05) for samples collected by an artificial vagina method than for those collected by electroejaculation. Although conception rate was low (10.6%), 6 pregnancies were achieved, 2 after hormonal induction of oestrus.