Recent shoreline changes in the Volta River delta,West Africa: the roles of natural processes and human impacts§

The Volta River delta developed as an asymmetric lobe in a tectonic offset on the coast of Ghana. The delta comprises a large curvilinear spit that widens in its central portion due to the adjunction of successive sandy beach ridges. The appearance of a distinct spit, in lieu of a continuous barrier from the present mouth of the Volta River to the Bight of Benin coast, may be an outgrowth of a natural change in the location of the mouth of the Volta. The spit marks a segmentation of the unique sand drift cell that hitherto prevailed on this bight coast. Spit growth has been accompanied by a wave of erosion over the last century of the immediate downdrift sector of the bight coast, endangering the town of Keta. Erosion since the 1960s may have been aggravated by the construction of the Akosombo hydropower dam. The tip of the spit has recently welded to the shoreline, thus assuring resumption of sand supply from the Volta towards the rest of this formerly sand-starved sector of the bight coast. Blocking of sediment by the Akosombo Dam is, in due course, likely to become the overarching factor in delta shoreline stability.     

GPSM2 mutations cause the brain malformations and hearing loss in Chudley-McCullough syndrome

Autosomal-recessive inheritance, severe to profound sensorineural hearing loss, and partial agenesis of the corpus callosum are hallmarks of the clinically well-established Chudley-McCullough syndrome (CMS). Although not always reported in the literature, frontal polymicrogyria and gray matter heterotopia are uniformly present, whereas cerebellar dysplasia, ventriculomegaly, and arachnoid cysts are nearly invariant. Despite these striking brain malformations, individuals with CMS generally do not present with significant neurodevelopmental abnormalities, except for hearing loss. Homozygosity mapping and whole-exome sequencing of DNA from affected individuals in eight families (including the family in the first report of CMS) revealed four molecular variations (two single-base deletions, a nonsense mutation, and a canonical splice-site mutation) in the G protein-signaling modulator 2 gene, GPSM2, that underlie CMS. Mutations in GPSM2 have been previously identified in people with profound congenital nonsyndromic hearing loss (NSHL). Subsequent brain imaging of these individuals revealed frontal polymicrogyria, abnormal corpus callosum, and gray matter heterotopia, consistent with a CMS diagnosis, but no ventriculomegaly. The gene product, GPSM2, is required for orienting the mitotic spindle during cell division in multiple tissues, suggesting that the sensorineural hearing loss and characteristic brain malformations of CMS are due to defects in asymmetric cell divisions during development.     

Aerobic degradation of tetrachloroethylene by toluene-o-xylene monooxygenase of Pseudomonas stutzeri OX1

Tetrachloroethylene (PCE) is thought to have no natural source, so it is one of the most difficult contaminants to degrade biologically. This common groundwater pollutant was thought completely nonbiodegradable in the presence of oxygen. Here we report that the wastewater bacterium Pseudomonas stutzeri OX1 degrades aerobically 0. 56 micromol of 2.0 micromol PCE in 21 h (Vmax approximately 2.5 nmol min(-1) mg(-1) protein and KM approximately 34 microM). These results were corroborated by the generation of 0.48 micromol of the degradation product, chloride ions. This degradation was confirmed to be a result of expression of toluene-o-xylene monooxygenase (ToMO) by P. stutzeri OX1, since cloning and expressing this enzyme in Escherichia coli led to the aerobic degradation of 0.19 micromol of 2.0 micromol PCE and the generation of stoichiometric amounts of chloride. In addition, PCE induces formation of ToMO, which leads to its own degradation in P. stutzeri OX1. Degradation intermediates reduce the growth rate of this strain by 27%.     

Synthesis and structure-activity relationships of novel dipeptides and reduced dipeptides as ligands for melanocortin subtype-4 receptor

A series of benzylic piperazines (e.g., 4 and 5) attached to an 'address element', the dipeptide H-D-Tic-D-p-Cl-Phe-OH, 3 has been identified as ligands for the melanocortin subtype-4 receptor (MC4R). We describe herein the structure-activity relationship (SAR) studies on the N-terminal residue of the 'address element'. Several novel dipeptides and reduced dipeptides with high MC4R binding affinities and selectivity emerged from this SAR study.     

NMR investigations of protein-carbohydrate interactions: refined three- dimensional structure of the complex between hevein and methyl beta- chitobioside

The specific interaction of hevein with GlcNAc-containing oligosaccharides has been analyzed by1H-NMR spectroscopy. The association constants for the binding of hevein to a variety of ligands have been estimated from1H-NMR titration experiments. The association constants increase in the order GlcNAc-alpha(1-->6)-Man < GlcNAc < benzyl-beta-GlcNAc < p-nitrophenyl-beta-GlcNAc < chitobiose < p- nitrophenyl-beta-chitobioside < methyl-beta-chitobioside < chitotriose. Entropy and enthalpy of binding for different complexes have been obtained from van't Hoff analysis. The driving force for the binding process is provided by a negative DeltaH0which is partially compensated by negative DeltaS0. These negative signs indicate that hydrogen bonding and van der Waals forces are the major interactions stabilizing the complex. NOESY NMR experiments in water solution provided 475 accurate protein proton-proton distance constraints after employing the MARDIGRAS program. In addition, 15 unambiguous protein/carbohydrate NOEs were detected. All the experimental constraints were used in a refinement protocol including restrained molecular dynamics in order to determine the highly refined solution conformation of this protein- carbohydrate complex. With regard to the NMR structure of the free protein, no important changes in the protein nOe's were observed, indicating that carbohydrate-induced conformational changes are small. The average backbone rmsd of the 20 refined structures was 0.055 nm, while the heavy atom rmsd was 0.116 nm. It can be deduced that both hydrogen bonds and van der Waals contacts confer stability to the complex. A comparison of the three-dimensional structure of hevein in solution to those reported for wheat germ agglutinin (WGA) and hevein itself in the solid state has also been performed. The polypeptide conformation has also been compared to the NMR-derived structure of a smaller antifungical peptide, Ac-AMP2.      

小麦条锈菌吸器母细胞入侵菌丝现象的进一步研究

应用电镜技术对小麦条锈菌吸器母细胞入侵自身菌丝的现象进行了研究,观察发现,在吸器母细胞与寄主细胞和菌丝细胞同时相接触的情况下,入侵栓可在与寄主细胞接触处形成,也可在与菌丝接触处形成;在菌落中心部位,吸器母细胞虽然未与寄主细胞接触,但同样可在与菌丝细胞接触处产生入侵栓;吸器母细胞在与菌丝接触处形成的人侵栓,其超微结构正常,并且可侵入到菌丝细胞壁内,但是未能穿透菌丝细胞壁。本文观察结果表明,小麦条锈菌吸器母细胞和人侵栓形成所需诱导因子可能是物理接触作用,而不涉及到化学作用,并且该病菌与寄主间的识别作用可能发生在入侵栓形成之后。     

Waist Circumference as a Screening Tool for Cardiovascular Risk Factors: Evaluation of Receiver Operating Characteristics (ROC)

To evaluate the receiver operating characteristics (ROC) to determine the cutoffs of waist circumference as a potential population directed screening tool for hypercholesterolaemia (≥6.5 mmol/L), low high density lipoprotein cholesterol (<0.9 mmol/L), and hypertension (treated and/or systolic ≥160 and/or diastolic blood pressure ≥95 mmHg), in 2183 men and 2698 women aged 20 to 59 years selected at random from Dutch civil registries. Main outcome measures: Height, weight, body mass index (BMI), waist circumference, total plasma cholesterol and high density lipoprotein cholesterol concentrations, and blood pressure. Results: ROC curves showed that sensitivity equalled specificity at waist circumferences between 93–95 cm in men and 81–84 cm in women for identifying individual risk factors, and 92 cm in men and 81 cm in women for identifying those with at least one risk factor. Sensitivity and specificity were equal at levels between 61% to 69% for identifying individual risk factors, with positive predictions (56.8% in men and 37.8% in women) within 2% of those using previously defined ‘Action Level 1’ of waist circumference 94 cm in men and 80 cm in women (58.8% in men and 37.4% in women). Risk prediction by anthropometric methods was relatively low: ROC areas for identifying each risk factor by waist varied from 55% to 60%, and reached about 65% for identifying at least one risk factor. Height accounted for less than 03% of variance in waist circumference. Using BMI at 25 kg/m² gave similar prediction to waist, but its combination with waist did not improve predictive values. Conclusions: Measurement of waist circumference ‘Action Level 1’ at 94 cm (37 inches) in men and 80 cm (32 inches) in women could be adopted as a simpler valid alternative to BMI for health promotion, to alert those at risk of cardiovascular disease, and as a guide to risk avoidance by self-weight management