Monogamy in black vultures: genetic evidence from DNA fingerprinting

Recent research has indicated that avian mating systems maycommonly deviate from monogamy due to extrapair fertilizations(EPFs). Because the majority of avian species have long beenconsidered monogamous, accurate measurement of the frequencyof EPFs in a variety of species is important to enhance understandingof the evolution of avian mating systems. We used DNA fingerprintingto investigate the apparently monogamous mating system of blackvultures (Coragyps airaius) by assaying parentage within severalnuclear families. Monogamy is suggested in black vultures becausemated pairs exhibit long-term pair bonding and year-round association,and share incubation and nestling feeding duties equally. Thirtytwobreeders and 36 nestlings representing 16 complete nuclear familieswere tagged for individual identification and sampled for DNAanalysis using 2 restriction enzymes and 3 probes for hypervariableregions. Putative parents were assigned parentage in all cases.We empirically examined the probability of detecting EPFs bycomparing nestlings' fingerprints to those of a putative parentand another randomly chosen adult. All putative parents couldbe assigned with 95%confidence and all outside adults couldbe similarly excluded. There is therefore no evidence for successfulEPFs in this population, indicating a mating system that doesnot deviate from strict monogamy. The complex social behaviorof black vultures may eliminate the opportunity for EPFs dueto the prohibition of copulations in the presence of relatives.     

Bioactivity and molecular modelling of diphenylsulfides and diphenylselenides

Bis(2-bromo-4,5-dimethoxyphenyl)sulfide (5) and bis(2-bromo-4,5-dimethoxyphenyl) selenide (7) have been shown to block cells in the G2/M phase of the cell cycle, whereas the debromo (4, 6) equivalents do not. The dibromoselenide (7) is cytotoxic to tumour cells in vitro and has been shown to increase the mitotic index of treated cells. These biological effects are consistent with disruption of the mitotic apparatus. This agent does not inhibit microtubule assembly in vitro, but does bind to tubulin. Molecular modelling of these structures indicates that their spatial and electronic structures may make an important contribution to the biological activity.     

Use of an ordered cosmid library to deduce the genomic organization of Mycobacterium leprae

In an attempt to unify the genetic and biological research on Mycobacterium leprae, the aetiological agent of leprosy, a cosmid library was constructed and then ordered by a combination of fingerprinting and hybridization techniques. The genome of M. leprae is represented by four contigs of overlapping clones which, together, account for nearly 2.B Mb of DNA. Several arguments suggest that the gaps between the contigs are small in size and that virtually complete coverage of the chromosome has been obtained. All of the cloned M. leprae genes have been positioned on the contig maps together with the 29 copies of the dispersed repetitive element, RLEP. These have been classified into four groups on the basis of differences in their organization. Several key housekeeping genes were identified and mapped by hybridization with heterologous probes, and the current genome map of this uncultivable pathogen comprises 72 loci.     

Construction and analysis of a recombination-deficient (radA) mutant of Haloferax volcanii

By deleting the radA open reading frame of an extreme halophile, Haloferax volcanii , we created and characterized a recombination-deficient archaeon. This strain, Hf. volcanii DS52, has no detectable DNA recombination, is more sensitive to DNA damage by UV light and ethylmethane sulfonate, and has a slower growth rate than the wild type. These characteristics are similar to those observed in recombination mutants of Eukarya and Bacteria, and show that the radA gene belongs in the recA / RAD51 family by function as well as sequence homology. In addition, strain DS52 was not transformable by plasmids pWL102 or pUBP2 (which contain pHV2 and pHH1 replicons, respectively), although it was readily transformed by plasmids containing a pHK2 replicon, indicating a role for radA in the maintenance or replication of some halobacterial plasmids. Despite its slower growth rate, Hf. volcanii DS52 was still easy to culture and transform, and should be suitable for use in studies where a recombination-deficient background is desired.     

General practitioners' perceptions of the tolerability of antidepressant drugs: a comparison of selective serotonin reuptake inhibitors and tricyclic antidepressants.

OBJECTIVE: To examine inceptions and discontinuations of antidepressants in general practice. DESIGN: An observational study analysing data from an ongoing cross sectional postal survey. Every three months a representative sample of 250 doctors recorded prescribing activity for four weeks. This provided 4000 general practitioner weeks of recording per year. SETTING: A representative panel of general practitioners in England, Wales, and Scotland. SUBJECTS: Patients who began a new course of an antidepressant or had their treatment stopped or changed by the general practitioner between 1 July 1990 and 30 June 1995. MAIN OUTCOME MEASURES: Numbers of patients prescribed a new course of antidepressant; numbers discontinuing treatment; the ratio of antidepressant discontinuations to antidepressant inceptions; reasons for discontinuation; proportion of switches to another antidepressant. RESULTS: There were 13,619 inceptions and 3934 discontinuations of selective serotonin reuptake inhibitors and tricyclic antidepressants during the study. The number of newly prescribed courses of antidepressants increased by 116%, mostly due to an increase in prescribing of serotonin reuptake inhibitors. The ratio of total discontinuations to inceptions was significantly lower for serotonin reuptake inhibitors (22%) than for tricyclic antidepressants (33%). Differences persisted when controlled for age and sex of patients and severity of depression. However, there was more switching away from selective serotonin reuptake inhibitors when they failed (72%) than from tricyclic antidepressants (58%). CONCLUSIONS: Selective serotonin reuptake inhibitors are less likely than tricyclic antidepressants to be discontinued. A prospective study is needed in general practice to assess the implications of differences in discontinuation rates and switches on clinical and economic outcomes.     

The relationship between sporulation and solvent production in clostridium acetobutylicum P262

Summary Single and multiple Clostridium acetobutylicum P262 sporulation, clostridial stage, granulose, capsule and solvent producing mutants were isolated. Although common regulatory components were involved in the regulation of these events, each individual pathway was able to function independently of each other. Inhibitors of DNA replication inhibited spore formation but did not affect solvent, clostridial stage, granulose and capsule production.