Although in Saccharomyces cerevisiae the initiation of meiotic recombination, as indicated by double-strand break formation, appears to be functionally linked to the initiation of synapsis, meiotic chromosome synapsis in Drosophila females occurs in the absence of meiotic exchange. Electron microscopy of oocytes from females homozygous for either of two meiotic mutants (mei-W68 and mei-P22), which eliminate both meiotic crossing over and gene conversion, revealed normal synaptonemal complex formation. Thus, synapsis in Drosophila is independent of meiotic recombination, consistent with a model in which synapsis is required for the initiation of meiotic recombination. Furthermore, the basic processes of early meiosis may have different functional or temporal relations, or both, in yeast and Drosophila.In the classical view of meiosis, homologous chromosome synapsis, as indicated by the formation of an elaborate ribbonlike structure called the synaptonemal complex (SC), was thought to be the first and primary event of meiotic prophase, essential for the initiation of meiotic recombination (1). Studies in Saccharomyces cerevisiae, however, have created a different view of the meiotic process in which the initiation of recombination, as evidenced by a doublestrand break (DSB), precedes the initiation of synapsis (2, 3). Three lines of evidence support this view of early meiotic prophase in yeast. First, the initiating event of meiotic recombination, the formation of a DSB, appears before SC formation (4). Second, meiotic mutants that either fail to create DSBs or to process DSBs to make single-stranded tails prevent the formation of a mature SC (2). Third, some mutants allow high levels of meiotic recombination but prevent the production of a mature SC (5). These data are consistent with a model in which single-stranded DNA generated by a DSB carries out a homology search required for synapsis and SC formation. In contrast, synapsis is not an absolute prerequisite for either the initiation (6) or completion of meiotic recombination (7).To assess the relation between synapsis and the initiation of recombination in Drosophila oocytes, we examined both recombination and SC formation in oocytes homozygous for either of two null-recombination mutations. The mei-W68 and mei-P22 (8) mutants prevent the initiation of meiotic recombination as defined by four independent assays: (i) reduction or elimination of meiotic gene conversion; (ii) elimination of meiotic crossing over, as assayed by measuring either intragenic crossing over or the frequency of meiotic crossing over along entire chromosome arms; (iii) lack of doublestrand DNA breaks that persist into metaphase or anaphase I; and (iv) failure to produce either early or late recombination nodules (RNs).To assay the effects of the mei-W68 and mei-P22 mutations on meiotic crossing over, we examined intragenic recombination at the rosy locus (9). No gene conversion events or intragenic crossovers were observed among the progeny of mei-W68 or mei-P22 females (Table 1 and Fig...

The addition of group lifestyle modification to the pharmacologic management of obesity significantly improved weight loss and patients' satisfaction with treatment outcome.

The last finding helps allay concerns that obese patients are routinely treated disrespectfully by physicians when discussing weight. The challenge, however, for primary care physicians appears to be providing patients better assistance with weight management.

Genetic variation within and among key species can have significant ecological consequences at the population, community, and ecosystem levels. In order to understand ecological properties of systems based on habitat-forming clonal plants, it is crucial to clarify which traits vary among plant genotypes and how they influence ecological processes, and to assess their relative contribution to ecosystem functioning in comparison to other factors. Here we used a mesocosm experiment to examine the relative influence of genotypic identity and extreme levels of nitrogen loading on traits that affect ecological processes (at the population, community, and ecosystem levels) for Zostera marina, a widespread marine angiosperm that forms monospecific meadows throughout coastal areas in the Northern Hemisphere. We found effects of both genotype and nitrogen addition on many plant characteristics (e.g., aboveground and belowground biomass), and these were generally strong and similar in magnitude, whereas interactive effects were rare. Genotypes also strongly differed in susceptibility to herbivorous isopods, with isopod preference among genotypes generally matching their performance in terms of growth and survival. Chemical rather than structural differences among genotypes drove these differences in seagrass palatability. Nitrogen addition uniformly decreased plant palatability but did not greatly alter the relative preferences of herbivores among genotypes, indicating that genotype effects are strong. Our results highlight that differences in key traits among genotypes of habitat-forming species can have important consequences for the communities and ecosystems that depend on them and that such effects are not overwhelmed by known environmental stressors.

. Effects of sibutramine plus orlistat in obese women following 1 year of treatment by sibutramine alone: a placebo-controlled trial. Obes Res. 2000;8:431-437. Objective: This study assessed whether adding orlistat to sibutramine would induce further weight loss in patients who previously had lost weight while taking sibutramine alone. Research Methods and Procedures: Patients were 34 women with a mean age of 44.1 Ϯ 10.4 years, weight of 89.4 Ϯ 13.8 kg, and body mass index (BMI) of 33.9 Ϯ 4.9 kg/m 2 who had lost an average of 11.6 Ϯ 9.2% of initial weight during the prior 1 year of treatment by sibutramine combined with lifestyle modification. Patients were randomly assigned, in double-blind fashion, to sibutramine plus orlistat or sibutramine plus placebo. In addition to medication, participants were provided five brief lifestyle modification visits during the 16-week continuation trial. Results: Mean body weight did not change significantly in either treatment condition during the 16 weeks. The addition of orlistat to sibutramine did not induce further weight loss as compared with treatment by sibutramine alone (mean changes ϭ ϩ0.1 Ϯ 4.1 kg vs. ϩ0.5 Ϯ 2.1 kg, respectively). Discussion: These results must be interpreted with caution because of the study's small sample size. The findings, however, suggest that the combination of sibutramine and orlistat is unlikely to have additive effects that will yield mean losses Ն15% of initial weight, as desired by many obese individuals.