Vegetation fluctuation in mediterranean dune ponds in relation to rainfall variation and water extraction

Abstract. The structure of dune ponds hygrophytic vegetation has a spatial organisation in belts around the pond basin, closely related to water level and flooding regime. Doñana National Park has an important representation of temporal dune ponds, which are subjected to rainfall fluctuations and may be suffering the impact of water extraction from the neighbouring tourist resort. Permanent transects in a vegetation complex of five dune ponds have been monitored during a eight year period (1990-1997). This period was characterised by a number of dry years (annual rainfall around 300 mm), located between two wet cycles (800-900 mm). Transects were analysed in 1990 (wet period), 1994 (dry) and 1997 (wet) by hierarchical agglomera-tive clustering. During the dry period hygrophytic species showed regression, with a high mortality of some species like Ulex minor, while the xerophytic species advanced to lower areas. Seedlings of some xerophytic species colonised the dry surface of the pond basin. The lowering of the water table varied in the different ponds, ranging from 312 to 190 cm depending on topography and the distance to the pumping area. The new period of flooding during 1995-96 and 1996-97 cycles provided the opportunity for hygrophytic spe cies to re-establish themselves in their original places. This study suggest that changes in vegetation are caused by the interaction between weather conditions and human disturbance (water extractions). In our example man-made disturbance is more marked during the dry periods while wet periods tend to obscure the effects of water extractions. From a management perspective, long-term monitoring of water table and vegetation structure is revealed as a key procedure to the management of land-water ecotones on pressured areas and threatened habitats.     

Expression of a lipocalin in prokaryote and eukaryote cells: quantification and structural characterization of recombinant bovine beta-lactoglobulin.

In this paper we quantify and characterize the expression of recombinant beta-lactoglobulin (rBLG) in prokaryote and eukaryote cells. In Escherichia coli we used the pET26 vector, which permits the secretion of rBLG in periplasm. We studied the expression of rBLG in COS-7 cells and in vivo in mouse tibialis muscle. The expression of rBLG was measured by two immunoassays specific, respectively, for BLG in its native and denatured conformation. We observed that rBLG was essentially expressed in a denatured form in E. coli even in the periplasm, whereas rBLG in eukaryote cells was found in its native conformation.     

A new internal perfusion method for transport studies in squid giant axons

A new internal perfusion method has been developed which allows control of the internal solute composition in squid axons. The superiority of this technique compared to the old perfusion methods is shown by the experiments performed which have reproduced, both qualitatively and quantitatively, the Na+ and Ca2+ fluxes observed in intact and dialyzed axons. Compared with the internal dialysis, the perfusion method has the advantage that the permeability barrier give by the porous capillary has been eliminated. This allows the introduction into the axon of solutes with very high molecular weight, at the same time that a fast and reliable internal control can be achieved.     

What Do We Know About Metal Recycling Rates?

The recycling of metals is widely viewed as a fruitful sustainability strategy, but little information is available on the degree to which recycling is actually taking place. This article provides an overview on the current knowledge of recycling rates for 60 metals. We propose various recycling metrics, discuss relevant aspects of recycling processes, and present current estimates on global end‐of‐life recycling rates (EOL‐RR; i.e., the percentage of a metal in discards that is actually recycled), recycled content (RC), and old scrap ratios (OSRs; i.e., the share of old scrap in the total scrap flow). Because of increases in metal use over time and long metal in‐use lifetimes, many RC values are low and will remain so for the foreseeable future. Because of relatively low efficiencies in the collection and processing of most discarded products, inherent limitations in recycling processes, and the fact that primary material is often relatively abundant and low‐cost (which thereby keeps down the price of scrap), many EOL‐RRs are very low: Only for 18 metals (silver, aluminum, gold, cobalt, chromium, copper, iron, manganese, niobium, nickel, lead, palladium, platinum, rhenium, rhodium, tin, titanium, and zinc) is the EOL‐RR above 50% at present. Only for niobium, lead, and ruthenium is the RC above 50%, although 16 metals are in the 25% to 50% range. Thirteen metals have an OSR greater than 50%. These estimates may be used in considerations of whether recycling efficiencies can be improved; which metric could best encourage improved effectiveness in recycling; and an improved understanding of the dependence of recycling on economics, technology, and other factors.     

Avons-nous percé le mystère de la globozoospermie ?

Globozoocephaly was first described in 1971, and 35 years were necessary to identify the first genetic origin (SPATA16 mutation), despite the development of many mice models and the certainty of a genetic origin for this syndrome taking into account observations in many siblings. Despite the recent identification of the new genes PICK1 and DPY19L2, globozoocephaly is still a mystery. This syndrome is probably polymorphic, as suggested by electronic microscopic details, and it is associated with a poor success rate in assisted reproductive tehnology (ART). Further studies are needed to understand the mechanism leading to the globozoocephalia and to define new therapeutic approaches to turn around major spermatic defects associated with this syndrome.     

Genetic control of insect pests: growth industry or lead balloon?

Genetic control is a form of biological control of pest species which exploits the insect's mate-seeking expertise to introduce genetic abnormalities (typically, but not necessarily, dominant lethal mutations) into the eggs of the wild population. The effectiveness of radiation-sterilized males depends on the mating competitiveness of released males being adequate in relation to the recovery potential of and rate of immigration into the target population. This technique is now being applied on a very large scale against agricultural pests especially in Mexico, Egypt and Japan. Variants on this technique, which may have advantages, include novel means of generating genetic loads in populations of Lepidioptera and sheep blowflies and the introduction into mosquito populations of genes making them unable to transmit malaria.     

Changes in fiber composition of soleus muscle during rat hindlimb suspension

Chronic reduction of gravitational load in the rear limbs of rats to simulate the influence of near-zero gravity in skeletal muscles has been shown previously to elicit atrophy in the soleus muscle. Use of this model by the present investigation indicates that soleus atrophy was characterized by a decline in the number of fibers in groups that contained the slow isoenzyme of myosin and which were classified as type I from intensity of staining to myofibrillar actomyosin adenosinetriphosphatase (ATPase) and to NADH tetrazolium reductase. Furthermore total fiber number was not changed, whereas fibers containing the intermediate isoenzyme and those classified as type IIa increased. There results could be explained by either a change in the composition within existing fibers or a simultaneous loss of slow fibers and de novo synthesis of intermediate and fast fibers. Evidence for transformation included an absence of embryonic or neonatal myosin in muscles from suspended rats and the constant fiber number that was unchanged by 4 wk of suspension. Furthermore although fiber areas of both groups of type I and IIa fibers declined during suspension, variability of the fiber areas within each group did not increase.     

Escherichia coli RecBC pseudorevertants lacking chi recombinational hotspot activity

Pseudorevertants of an Escherichia coli exonuclease V (RecBC enzyme)-negative mutant have been isolated after ethyl methane sulfonate mutagenesis of a recC73 (presumed missense) mutant. The remedial mutations in each of the four pseudorevertants studied in detail map and complement as recC mutations. By several criteria, such as recombination proficiency, support of phage growth, RecBC nuclease activity, and cell viability, the pseudorevertants appear to have regained partially or completely various aspects of RecBC activity. However, chi recombinational hotspots, which stimulate exclusively the RecBC pathway of recombination, have no detectable activity in lambda vegetative crosses in the pseudorevertants. The properties of these mutants, in which the RecBC pathway of recombination is active yet in which chi is not active, are consistent with the hypothesis that wild-type RecBC enzyme directly interacts with chi sites; alternatively, the mutants may block or bypass the productive interaction of another recombinational enzyme with chi.