Distribution of genetic diversity in relation to chromosomal inversions in the malaria mosquito Anopheles gambiae

The epidemiology of malaria in Africa is complicated by the fact that its principal vector, the mosquito Anopheles gambiae, constitutes a complex of six sibling species. Each species is characterized by a unique array of paracentric inversions, as deduced by karyotypic analysis. In addition, most of the species carry a number of polymorphic inversions. In order to develop an understanding of the evolutionary histories of different parts of the genome, we compared the genetic variation of areas inside and outside inversions in two distinct inversion karyotypes of A. gambiae. Thirty-five cDNA clones were mapped on the five arms of the A. gambiae chromosomes with divisional probes. Sixteen of these clones, localized both inside and outside inversions of chromosome 2, were used as probes in order to determine the nucleotide diversity of different parts of the genome in the two inversion karyotypes. We observed that the sequence diversity inside the inversion is more than three-fold lower than in areas outside the inversion and that the degree of divergence increases gradually at loci at increasing distance from the inversion. To interpret the data we present a selectionist and a stochastic model, both of which point to a relatively recent origin of the studied inversion and may suggest differences between the evolutionary history of inversions in Anopheles and Drosophila species.     

Infraorbital nerve transection alters serotonin transporter expression in sensory pathways in early postnatal rat development

OBJECTIVE: To determine the relationship between sperm motility and sperm morphology parameters and IVF and pregnancy rates. DESIGN: Pre- and postpreparation analysis of semen samples from infertile couples undergoing IVF-ET. SETTING: Andrology Laboratory, Royal Maternity Hospital, Belfast, Northern Ireland. PATIENT(S): One hundred fifty couples undergoing IVF-ET treatment at the Regional Fertility Centre. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): The ability of human sperm to achieve IVF and pregnancy was investigated in relation to motility parameters (assessed with computer-aided sperm analysis [Integrated Visual Optical System] and percent normal morphology (determined with the strict criteria). RESULT(S): Significant differences were observed in motility parameters and percent normal morphology in samples that achieved > or =50% fertilization compared with < or =50% fertilization and between samples that achieved a pregnancy compared with those that did not. Significant positive correlations were observed between percent progressive motility, the velocity of sperm movement, and morphology parameters and both IVF and pregnancy. CONCLUSION(S): Both sperm motility parameters and percent normal morphology are significant factors in predicting fertilization and pregnancy rates in IVF.     

Atopic allergy and immunoglobulins in children with adenoids and recurrent otitis media

From 274 adenoidectomized children 1-16 years of age two groups were selected: children with a history of recurrent otitis media and/or otosalpingitis (middle ear effusion) and those in which nasal obstruction was the main symptom. In all, 154 children were subjected to an allergy investigation including history, skin tests, eye tests, determination of IgE and RAST, blood eosinophils and immunoglobulins G, A and M. No increased incidence of immunoglobulin deficiency was found in either group in comparison with unselected children. A family history of atopic disease and/or otitis media was highly overrepresented, especially in the children with recurrent otitis media as the reason for the adenoidectomy. Atopic diseases had occurred in 24.4% of the children. Furthermore, in both groups there was a high incidence of positive skin and eye tests. An increased incidence of eosinophila, positive RAST tests and elevated IgE levels were also found. In all, 39.6% of the children had two or more laboratory findings characteristic of the atopic state but no significant difference was found between the two groups. Possible connections between atopic allergy and recurrent otitis media are discussed.     

Comments on electrochemical measurements of the rate of corrosion of steel in concrete

The electrochemical processes involved in the corrosion of steel are briefly described in terms of their thermodynamics and kinetics. The purpose is to explain and discuss the currently used laboratory techniques of corrosion rate measurements of reinforcement steel in concrete.