Functions of the segment polarity genes midline and H15 in Drosophila melanogaster neurogenesis

The Drosophila melanogaster ventral nerve cord derives from neural progenitor cells called neuroblasts. Individual neuroblasts have unique gene expression profiles and give rise to distinct clones of neurons and glia. The specification of neuroblast identity provides a cell intrinsic mechanism which ultimately results in the generation of progeny which are different from each other. Segment polarity genes have a dual function in early neurogenesis: within distinct regions of the neuroectoderm, they are required both for neuroblast formation and for the specification of neuroblast identity. Previous studies of segment polarity gene function largely focused on neuroblasts that arise within the posterior part of the segment. Here we show that the segment polarity gene midline is required for neuroblast formation in the anterior-most part of the segment. Moreover, midline contributes to the specification of anterior neuroblast identity by negatively regulating the expression of Wingless and positively regulating the expression of Mirror. In the posterior-most part of the segment, midline and its paralog, H15, have partially redundant functions in the regulation of the NB marker Eagle. Hence, the segment polarity genes midline and H15 play an important role in the development of the ventral nerve cord in the anterior- and posterior-most part of the segment.     

Collapse of an avifauna: climate change appears to exacerbate habitat loss and degradation

Aim  We characterized changes in reporting rates and abundances of bird species over a period of severe rainfall deficiency and increasing average temperatures. We also measured flowering in eucalypts, which support large numbers of nectarivores characteristic of the region.
Location  A 30,000-km² region of northern Victoria, Australia, consisting of limited amounts of remnant native woodlands embedded in largely agricultural landscapes.
Methods  There were three sets of monitoring studies, pitched at regional (survey programmes in 1995–97, 2004–05 and 2006–08), landscape (2002–03 and 2006–07) and site (1997–2008 continuously) scales. Bird survey techniques used a standard 2-ha, 20-min count method. We used Bayesian analyses of reporting rates to document statistically changes in the avifauna through time at each spatial scale.
Results  Bird populations in the largest remnants of native vegetation (up to 40,000 ha), some of which have been declared as national parks in the past decade, experienced similar declines to those in heavily cleared landscapes. All categories of birds (guilds based on foraging substrate, diet, nest site; relative mobility; geographical distributions) were affected similarly. We detected virtually no bird breeding in the latest survey periods. Eucalypt flowering has declined significantly over the past 12 years of drought.
Main conclusions  Declines in the largest woodland remnants commensurate with those in cleared landscapes suggest that reserve systems may not be relied upon to sustain species under climate change. We attribute population declines to low breeding success due to reduced food. Resilience of bird populations in this woodland system might be increased by active management to enhance habitat quality in existing vegetation and restoration of woodland in the more fertile parts of landscapes.     

Total syntheses of iso-, neuro- and phytoprostanes: new insight in lipid chemistry

Isoprostanes (IsoPs) are a complex family of compounds produced, in vivo, from peroxidation of polyunsaturated fatty acids (AA, DHA, EPA, alpha-linolenic) via a free-radical-catalyzed mechanism. Carbocyclic annulations are extremely important reactions and the stereocontrolled intramolecular free-radical cyclization has emerged as a powerful tool for carbon-carbon bond formation in synthetic chemistry. The hex-5-enyl radical cyclization is the most well-known for the synthesis of cyclopentane rings. After a short review of the literature, concerning the total synthesis of isoprostanes and intermediates, we will present our own contributions on the preparation of chiral cyclopentane rings from glucose leading to new isoprostanes. This study allowed us to control the cyclization outcome to yield the all-syn and/or syn-anti-syn precursors which permit us to the total synthesis of a large set of iso-, neuro-, and phytoprostanes.     

Structural investigation of the capsular polysaccharide of Klebsiella serotype k23

Klebsiella K23 capsular polysaccharide has been investigated by the techniques of hydrolysis, methylation, Smith degradation-periodate oxidation, and base-catalysed degradation, either on the original or the carboxyl-reduced polysaccharide. The structure was found to consist of a tetrasaccharide repeating-unit, as shown below. The anomeric configurations of the sugar residues were determined by ₁H-and ¹³C-n.m.r. spectroscopy on the original and degraded polysaccharides.

     

Influence of the blood concentration of prolactin on the length of the sensitive period for establishing maternal behavior in sheep at parturition

The fading of postpartum maternal interest for the neonate (sensitive period) in ewes separated from their young at lambing is delayed when parturition is induced with 20 mg of estradiol benzoate (EB). An experiment was carried out to investigate the role of prolactin in this phenomenon. The sensitive period was studied in three groups of parturient ewes. In all groups lambs were removed at birth and reintroduced to their mothers 24 hr later. Maternal acceptance was tested at this time. In group 1 (dexamethasone D), ewes were induced to lamb with dexamethasone (15 mg im). In group 2 (EB), ewes were treated with 20 mg of estradiol benzoate (im). In group 3 (EB + CB 154) ewes received 20 mg of EB as in group 2 and 1 mg of CB 154 (sc) every 12 hr to prevent the enhanced secretion of prolactin which normally occurs after EB injection. The concentration of prolactin was highest in group 2 (EB), lowest in group 3 (EB + CB), and intermediate in group 1 (D) (p ? 0.001 between groups). By contrast, the proportion of ewes showing maternal behavior was similar in groups 2 and 3 ($\text{15}\text{23}$ and $\text{17}\text{22}$), both of which differed from group 1 ($\text{3}\text{22}\text{; p ? 0.005}$). It is concluded that the lengthening of the sensitive period for establishing maternal behavior in sheep following EB induced parturition is not related with high levels of prolactin in the peripheral circulation.     

Alterations in carbohydrate metabolism and its regulation in PPARalpha null mouse hearts

Although a shift from fatty acids (FAs) to carbohydrates (CHOs) is considered beneficial for the diseased heart, it is unclear why subjects with FA beta-oxidation defects are prone to cardiac decompensation under stress conditions. The present study investigated potential alterations in the myocardial utilization of CHOs for energy production and anaplerosis in 12-wk-old peroxisome proliferator-activating receptor-alpha (PPARalpha) null mice (a model of FA beta-oxidation defects). Carbon-13 methodology was used to assess substrate flux through energy-yielding pathways in hearts perfused ex vivo at two workloads with a physiological substrate mixture mimicking the fed state, and real-time RT-quantitative polymerase chain reaction was used to document the expression of selected metabolic genes. When compared with that from control C57BL/6 mice, isolated working hearts from PPARalpha null mice displayed an impaired capacity to withstand a rise in preload (mimicking an increased venous return as it occurs during exercise) as reflected by a 20% decline in the aortic flow rate. At the metabolic level, beyond the expected shift from FA (5-fold down) to CHO (1.5-fold up; P < 0.001) at both preloads, PPARalpha null hearts also displayed 1) a significantly greater contribution of exogenous lactate and glucose and/or glycogen (2-fold up) to endogenous pyruvate formation, whereas that of exogenous pyruvate remained unchanged and 2) marginal alterations in citric acid cycle-related parameters. The lactate production rate was the only measured parameter that was affected differently by preloads in control and PPARalpha null mouse hearts, suggesting a restricted reserve for the latter hearts to enhance glycolysis when the energy demand is increased. Alterations in the expression of some glycolysis-related genes suggest potential mechanisms involved in this defective CHO metabolism. Collectively, our data highlight the importance of metabolic alterations in CHO metabolism associated with FA oxidation defects as a factor that may predispose the heart to decompensation under stress conditions even in the fed state.     

Spatial and Temporal Variability of Zooplankton in a Great Plains Reservoir

Seasonal and daily patterns of zooplankton populations are often predictable in natural lakes. Distinct zonation and geomorphic differences in reservoirs, however, make ecological extrapolations from lakes to reservoirs uncertain. We describe the spatial and temporal distribution of zooplankton, algae, and water clarity across reservoir zones and along a depth gradient in Glen Elder Reservoir, Kansas. Daphnia species were most abundant in the lacustrine zone, with D. pulicaria numerically dominant in early spring and D. mendotae dominant later in 1999 and 2000. Rotifers (Keratella quadrata, Asplanchnaspp.) were dominant in the riverine zone in 1999, 2000, and 2001. Algal biomass was not significantly different between zones through most of the sampling periods, except late April in 1999 and mid-April in 2000. Chlorophyll a exceeded 81 μg l^?1 in the lacustrine zone in mid- to late-April in 1999 and 2000, and exceeded 90μg l^?1in the riverine zone in mid-April. Water clarity was significantly lower in the riverine zone in 1999 and 2000. Most zooplankton taxa had similar depth distributions at night and day, indicating a lack of diel vertical migration behavior on a large scale. However, in small scale (30 cm vertical enclosures) laboratory experiments, both D. pulicaria and D. mendotae occupied significantly deeper depths (>25 cm) under lighted conditions in the presence of fish chemical cues compared to shallow water (7–17 cm) under dark conditions and in the absence of fish cues. These contrasting results suggest that, as in other studies, Daphnia sense cues from predators and alter their depth in the water column on small scales without natural constraints on movement and choices. However, other factors in the reservoir such as wind-generated water movements and cues from other predators may prevent depth choices similar to those seen under controlled conditions. These results illustrate biotic and abiotic differences between riverine and lacustrine zones in a large reservoir, and contrast with Daphnia depth segregation and migration patterns in natural lakes.     

Identification of a Major Susceptibility Locus for Restless Legs Syndrome on Chromosome 12q

Restless legs syndrome (RLS) is a neurological disorder characterized by leg paresthesia associated with an irresistible urge to move that often interferes with nocturnal sleep, leading to chronic sleep deprivation. To map genes that may play a role in the vulnerability to RLS, a genomewide scan was conducted in a large French-Canadian family. Significant linkage was established on chromosome 12q, for a series of adjacent microsatellite markers with a maximum two-point LOD score of 3.42 (recombination fraction.05; P=6x10(-4); autosomal recessive mode of inheritance), whereas multipoint linkage calculations yielded a LOD score of 3.59. Haplotype analysis refined the genetic interval, positioning the RLS-predisposing gene in a 14.71-cM region between D12S1044 and D12S78. These findings represent the first mapping of a locus conferring susceptibility to RLS.     

Relative rates of synonymous substitutions in the mitochondrial, chloroplast and nuclear genomes of seed plants

Previous studies have estimated that, in angiosperms, the synonymous substitution rate of chloroplast genes is three times higher than that of mitochondrial genes and that of nuclear genes is twelve times higher than that of mitochondrial genes. Here we used 12 genes in 27 seed plant species to investigate whether these relative rates of substitutions are common to diverse seed plant groups. We find that the overall relative rate of synonymous substitutions of mitochondrial, chloroplast and nuclear genes of all seed plants is 1:3:10, that these ratios are 1:2:4 in gymnosperms but 1:3:16 in angiosperms and that they go up to 1:3:20 in basal angiosperms. Our results show that the mitochondrial, chloroplast and nuclear genomes of seed plant groups have different synonymous substitutions rates, that these rates are different in different seed plant groups and that gymnosperms have smaller ratios than angiosperms.