Cell cycle and sporulation in Bacillus subtilis

Recent work on cell division and chromosome orientation and partitioning in Bacillus subtilis has provided insights into cell cycle regulation during growth and development. The cell cycle is an integral part of development and entrance into sporulation is modulated by signals that transmit the status of DNA integrity, chromosome replication and segregation. In addition, B. subtilis modifies cell division and DNA segregation to establish cell-type-specific gene expression during sporulation.     

Circulating Insulin Concentrations,Smoking, and Alcohol Intake Are Important Independent Predictors of Leptin in Young Healthy Men

Objective : Leptin, an adipocyte-secreted hormone, has been shown to signal the status of energy stores to the brain, regulate energy homeostasis, and mediate the neuroendocrine response to food deprivation. Obesity is associated with increased leptin levels, and several hormones, including insulin and glucocorticoids, have been associated with leptin levels and expression in rodents. Although obesity has been strongly associated with increased leptin in humans, a significant percentage of leptin's variability remains unexplained. The role of endogenous hormones, demographic factors, or certain life-style factors in explaining the residual variability of leptin levels has not yet been clarified. We performed this cross-sectional study to document the relative importance of obesity, lifestyle factor, and endogenous hormones in determining serum leptin levels. Research Methods and Procedures : We measured serum concentrations of insulin, Cortisol, testosterone, growth hormone, and dehydroepiandrosterone sulfate; ascertained anthropometric, demographic, and lifestyle characteristics; and studied these variables in relationship to serum leptin concentrations in a sample of young healthy men. Results : Obesity and alcohol intake were independently and positively associated with circulating leptin concentrations. Additionally, cigarette smoking was negatively and independently associated with leptin concentrations. Finally, serum insulin concentration was an independent hormonal determinant of circulating leptin concentrations, whereas serum testosterone was negatively associated with leptin only by bivariate analysis. Discussion : We conclude that, in addition to obesity, cigarette smoking, alcohol intake, and serum insulin levels are associated with leptin levels in a population of healthy young men.     

Phenotypic analysis and molecular cloning of discolored-1 (dsc1), a maize gene required for early kernel development

Recessive mutations in the maize dsc1 locus prevent normal kernel development. Solidification of the endosperm in homozygous dsc1– mutant kernels was undetectable 12 days after pollination, at which time the tissue was apparently completely solidified in wild-type kernels. At later times endosperm did solidify in homozygous dsc1– mutant kernels, but there was a marked reduction in the volume of the tissue. Embryo growth in homozygous dsc1– kernels was delayed compared to wild-type kernels, but proceeded to an apparently normal stage 1 in which the scutellum, coleoptile, and shoot apex were clearly defined. Embryo growth then ceased and the embryonic tissues degraded. Late in kernel development no tissue distinctions were obvious in dsc1– mutant embryos. Immature mutant embryos germinated when transplanted from kernels to tissue culture medium prior to embryonic degeneration, but only coleoptile proliferation was observed. The dsc1 gene was isolated by transposon tagging. Analysis of the two different dsc1– mutations confirmed that transposon insertion into the cloned genomic locus was responsible for the observed phenotype. Dsc1 mRNA was detected specifically in kernels 5–7 days after pollination. These data indicate Dsc1 function is required for progression of embryo development beyond a specific stage, and also is required for endosperm development.     

Use of Landmarks in Three Species of Food-storing Corvids

The use of landmarks by Clark's nutcrackers (Nucifraga columbiana), pinyon jays (Gymnorbinus cyanocepbalus), and Western scrub jays (Apbelocoma coerulescens) was investigated in three experiments. In the first experiment, birds were trained to find a hidden food reward beneath wood chips near a plastic landmark located 20 cm from one edge of a stationary tray. During unrewarded test trials, all species displaced their searching in response to movement of the landmark in both parallel and perpendicular directions; however, searching was displaced significantly more in the parallel direction. In a second experiment, the landmark was removed with the tray stationary or shifted. When the tray was shifted, all species responded by searching relative to the shifted tray. This indicates that the global (room) cues were not being used as salient landmarks. In the third experiment, the tray was placed in different positions for each trial, making global cues unreliable. As in experiment 1, all species displaced their searching in response to parallel and perpendicular movement of the landmark, with movement being similar in both directions. These results indicate no species differences on this landmark-use task.     

Biodiversity quality: A paradigm for biodiversity

This paper addresses the need for an internationally accepted definition of biodiversity the lack of which creates difficulty in measuring biodiversity difference and change. The authors suggest that well-sampled data can be used to generate a range of numerical indices reflecting species group characteristics/functionality that can be viewed in combination to create a picture of Biodiversity Quality. Examples of this approach demonstrate how to expand the currently accepted Convention on Biological Diversity definition, based on the “variability” of genes, species and ecosystems, since the numerical expression of the indices allows the probability of difference between biodiversity quality trends and values over time, and between sites or taxonomic groups, to be assessed for statistical inference of difference or similarity.     

What effect does classroom separation have on twins' behavior, progress at school, and reading abilities?

We investigated the effects of classroom separation on twins' behavior, progress at school, and reading abilities. This investigation was part of a longitudinal study of a nationally-representative sample of twins (the E-risk Study) who were assessed at the start of school (age 5) and followed up (age 7). We examined three groups of twins: pairs who were in the same class at both ages; pairs who were in separate classes at both ages; and pairs who were in the same class at age 5, but separated by age 7. When compared to those not separated, those separated early had significantly more teacher-rated internalizing problems and those separated later showed more internalizing problems and lower reading scores. Monozygotic (MZ) twins showed more problems as a result of separation than dizygotic (DZ) twins. No group differences emerged for externalizing problems, ADHD or prosocial behaviors. The implications of the findings for parents and teachers of twins, and for school practices about separating twins, are discussed.     

OPA1 (dys)functions

Mitochondrial morphology varies according to cell type and cellular context from an interconnected filamentous network to isolated dots. This morphological plasticity depends on mitochondrial dynamics, a balance between antagonistic forces of fission and fusion. DRP1 and FIS1 control mitochondrial outer membrane fission and Mitofusins its fusion. This review focuses on OPA1, one of the few known actors of inner membrane dynamics, whose mutations provoke an optic neuropathy. Since its first identification in 2000 the characterization of the functions of OPA1 has made rapid progress thus providing numerous clues to unravel the pathogenetic mechanisms of ADOA-1.     

1999 Issol Meeting

Origins of Life and Evolution of Biospheres -