Mitochondrial DNA variants in Drosophila melanogaster are expressed at the level of the organismal phenotype.

A plethora of experimental studies use mtDNA as a marker of demographic processes without questioning the possibility that selection may bias their interpretations. We studied four lines of Drosophila melanogaster that have a standardized nuclear DNA but variable mtDNA. We completed the sequencing of the mitochondrial genomes (excluding the A+T rich region) and compiled the differences. We then assayed male influence on oviposition, starvation resistance, lipid proportion and physical activity. We discuss these results in terms of the known differences between the lines and conclude that naturally occurring mtDNA variants in D. melanogaster are expressed at the level of the organismal phenotype.

Extension of life-span by loss of CHICO, a Drosophila insulin receptor substrate protein.

The Drosophila melanogaster gene chico encodes an insulin receptor substrate that functions in an insulin/insulin-like growth factor (IGF) signaling pathway. In the nematode Caenorhabditis elegans, insulin/IGF signaling regulates adult longevity. We found that mutation of chico extends fruit fly median life-span by up to 48% in homozygotes and 36% in heterozygotes. Extension of life-span was not a result of impaired oogenesis in chico females, nor was it consistently correlated with increased stress resistance. The dwarf phenotype of chico homozygotes was also unnecessary for extension of life-span. The role of insulin/IGF signaling in regulating animal aging is therefore evolutionarily conserved.

Behavior of Wolbachia endosymbionts from Drosophila simulans in Drosophila serrata, a novel host.

Many species harbor the incompatibility-inducing microbe Wolbachia, a maternally inherited endoparasite that causes reduced egg hatch in crosses between infected males and uninfected females. Infected females are immune to this effect, which gives them a relative fitness advantage that results in the spread of the infection. The strength of incompatibility, fitness deficits associated with the infection, and transmission rate from mother to offspring largely determine the rate and extent of spread of Wolbachia in a population. We transferred Wolbachia from Drosophila simulans to Drosophila serrata, a novel host, and compared parameter estimates with those from three naturally occurring Drosophila-Wolbachia associations believed to be of different ages. Transfected D. serrata showed strong incompatibility, low transmission efficiency, and an associated fitness deficit, and they would probably be unable to spread in nature. The comparisons generally supported the predicted evolution of a host-Wolbachia association. The parameters peculiar to any given host-Wolbachia association may determine whether the microbial strain can spread in that host.

Cytoplasmic incompatibility in Australian populations of Drosophila melanogaster.

In Drosophila melanogaster, weak incompatibility in crosses between infected and uninfected strains is associated with a Wolbachia microorganism. Crosses between infected males and uninfected females show a reduction (15-30%) in egg hatch. Progeny tests indicated that the infection is widespread in Australian D. melanogaster populations and that populations are polymorphic for the presence of the infection. The infection status of 266 lines from 12 populations along the eastern coast of Australia was determined by 4',6-diamidino-2-phenylindole (DAPI) staining of embryos. All populations contained both infected and uninfected flies. Infection frequencies varied between populations but there was no discernible geographical pattern. Laboratory experiments indicated that the infection was not associated with a reduction in fecundity as in Drosophila simulans. Incompatibility levels could not be increased by laboratory selection on isofemale lines. Factors contributing to the persistence of the infection in D. melanogaster populations are discussed.

Schizophrenia in migrants living in the western region of Melbourne.

Comparison is made between migrant (n = 332) and Australian-born (n = 242) schizophrenic outpatients attending a regional psychiatric hospital. Age-corrected rates show that migrants are over-represented. The migrant patient-group was older, developed the illness later, and had a higher proportion of females. More female migrant patients had developed the illness before arrival and in the first five years after migration compared to males whose peak incidence was between 11 and 15 years after arrival. Migrant patients showed greater family cohesion. On broad socio-economic indices, illness characteristics and treatment received, no significant differences emerged. In many respects patients born in U.K. and Ireland resembled the Australian-born.

Patterns of outpatient consultation: a survey of outpatients attending a metropolitan psychiatric hospital.

A survey of all outpatients (n = 1135) attending a regional psychiatric hospital during a 3-month period. Psychoses constituted 72% and non-psychotic disorders 25%. Psychoses had a greater proportion of long-term attenders while non-psychotic disorders, though frequent (43%) among recent attenders, showed a high attrition rate. Demographic characteristics, patterns of attendance, selected clinical features, level of functioning and difficulties of management of the different diagnostic groups are presented and discussed. Reasons are adduced to explain why patients who were deemed suitable for transfer to other care had not been discharged from hospital. Steps taken to reduce the patient load and increase the efficiency of the services are described.

Determination of orthoesters by hydrolysis and Karl Fischer titrimetry.

The acid hydrolysis of orthoesters has been made the basis of a titrimetric method. The method involves reaction of an orthoester with a known excess of water in a trichloroacetic acid-methyl alcohol system, followed by determination of unreacted water by Karl Fischer titration.