Fetal intestinal microvilli in human amniotic fluid

The intestinal microvilli of fetal origin in human amniotic fluid were purified by Ca²⁺ precipitation of contaminating organelles followed by differential centrifugation of microvillar membranes. In the purified preparation, the specific activity of the microvillar marker-enzymes maltase and sucrase increased about 77-fold over that in cell-free amniotic fluid. Significant contamination of the purified preparation by endoplasmic reticulum (microsomes) and lysosomes was ruled out on the basis of a low content of the marker enzymes glucose-6-phosphatase (microsomes) and acid phosphatase (lysosomes). Amniotic fluid microvilli contain typical enzymes of the fetal intestine including maltase, sucrase, trehalase, alkaline phosphatase and γ-glutamyltransferase, and their morphology by electron microscopy resembles that of vesiculated intestinal microvilli. Prenatal detection of genetic diseases due to a deficiency of a protein expressed in these membranes or associated to abnormal microvilli seems feasible.     

Analysing countries’ contribution to climate change: scientific and policy-related choices

This paper evaluates the influence of different policy-related and scientific choices on the calculated regional contributions to global climate change (the “Brazilian Proposal”). Policy-related choices include the time period of emissions, the mix of greenhouse gases and different indicators of climate change impacts. The scientific choices include historical emissions and model representations of the climate system. We generated and compared results of several simple climate models. We find that the relative contributions of different nations to global climate change—from emissions of greenhouse gases alone—are quite robust, despite the varying model complexity and differences in calculated absolute changes. For the default calculations, the average calculated contributions to the global mean surface temperature increase in 2000 are about 40% from OECD, 14% from Eastern Europe and Former Soviet Union, 24% from Asia and 22% from Africa and Latin America. Policy-related choices, such as time period of emissions, climate change indicator and gas mix generally have larger influence on the results than scientific choices. More specifically, choosing a later attribution start date (1990 instead of 1890) for historical emissions, decreases the contributions of regions that started emitting early, such as the OECD countries by 6 percentage points, whereas it increases the contribution of late emitters such as Asia by 8 percentage points. However, only including the fossil CO₂ emissions instead of the emissions of all Kyoto gases (fossil and land use change), increases the OECD contributions by 21 percentage points and decreases the contribution of Asia by 14 percentage points.     

Semiochemicals mediating host-finding behaviour in the phoretic association between Macrocheles saceri (Acari: Mesostigmata) and Scarabaeus species (Coleoptera: Scarabaeidae)

Summary. Phoresy is an interspecific association where mobile organisms ensure small and/or wingless organisms to colonize patchy distributed environment. Macrocheles saceri (Acari: Mesostigmata) is a phoretic mite which specialized on Scarabaeus dung beetles (Coleoptera: Scarabaeidae). Variation for phoretic load and sites for mite fixation on beetle body has been tested according to Scarabaeus species. The number of setae on beetle body cannot explain the observed patterns in mite fixation. Evidence was provided that the semiochemicals of the host cuticle play a kairomonal role in the host finding behaviour of phoretic mites. In addition semiochemicals ensure host discrimination.     

Beyond conservation ideology and the wilderness

There are close to 8500 major protected areas, covering some 5% of the world's land area. Many countries have more than 10% of their area set aside for conservation purposes. But this increase in designated conservation has been accompanied by a strong ideology that people are bad for natural resources. Policies and practice have, therefore, both encouraged exclusion and discouraged local participation. As a result, social conflicts have grown in and around protected areas, and conservation goals themselves have been threatened. Conservation science itself needs rethinking. It has been dominated by the positivist and rationalist paradigm, in which professionals assume they know best and so can analyse and influence natural resources in the ways they desire. But if natural resources are to be conserved, then the skills, knowledge and needs of local people will have to be built upon. This will require radical reversals in current professional thinking and practice .     

Environmental impact of two successive chemical treatments in a small shallow eutrophied lake: Part II. Case of copper sulfate

The appearance of cyanobacteria ( > 10 colony per ml) was not prevented after alum treatment. In order to prevent cyanobacteria efflorescences in a small shallow polymictic lake (Courtille, France), copper sulfate was applied. Treatment level was 63 microg 1(-1) as Cu2+ from CUSO4, 5 H2O. Cyanobacteria were kept under control during the summer. Microcystis sp. completely disappeared, which allowed swimming in the lake throughout the tourist season. Microcystis only reappeared 2 months after the treatment. Copper content in the water column only returned to its background level 2 months after copper addition. This high residence time of copper in the water might have been caused by complexation and adsorption of copper on natural organic matter, whose level was high in the ecosystem studied. A mechanism of transfer of 'truly' dissolved copper towards particulate copper has been underlined and explains the disappearance of this fraction of copper in the water column.     

Effect of cropping and tillage on the dissipation of PAH contamination in soil

This study examined the effect of regular tillage and cropping on the dissipation rate of PAHs in contaminated soil. Lysimeters were placed under natural climatic conditions for 2 years and designed to measure the concentration of PAHs in soil and leachates and their toxicity. The soil initially contained 2077 microg PAHs g(-1). The largest decrease in PAHs concentration occurred during the first 6 months. No further significant decrease was observed after this time. The surface soil layer always contained significantly less PAHs than the deeper layer, regardless of the treatments. Less than 8.4 x 10(-8)% of the PAH initially present in the soil (e.g. less or equal to 33 microg PAHs per lysimeter) were leached from the soils during the experiment and the leachates presented no toxicity (as measured by the Microtox test). The toxicity of the soils decreased with time and was significantly lower on the cropped soil compared to the other treatments, despite the residual concentration of PAHs being the highest in this soil. This study demonstrated that the dissipation rates of PAHs were slow after using natural attenuation even when tillage and cropping were performed at the soil surface.     

Localization and biochemical characterization of pharyngeal protease in the polychaetous annelid Glycera convoluta

In Glycera convoluta Keferstein, pharyngeal protease is secreted by the glandular epithelial cells, as clearly demonstrated by microscopic observation of the digestion of a prestained gelatin film by fresh tissue sections of the organ. The enzyme, extracted by affinity chromatography on Sepharose-?-aminocaproïc-D-tryptophan, acts on substrates hydrolyzable by α-chymotrypsin such as N-benzoyl-L-tyrosine ethyl ester and carboxyl-propionyl-phenylalanine-p-nitroanilide, and can be considered as a chymotrypsin-like enzyme.     

Division of labour and worker size polymorphism in ant colonies: the impact of social and genetic factors

Division of labour among workers is central to the organisation and ecological success of insect societies. If there is a genetic component to worker size, morphology or task preference, an increase in colony genetic diversity arising from the presence of multiple breeders per colony might improve division of labour. We studied the genetic basis of worker size and task preference in Formica selysi, an ant species that shows natural variation in the number of mates per queen and the number of queens per colony. Worker size had a heritable component in colonies headed by a doubly mated queen (h ²=0.26) and differed significantly among matrilines in multiple-queen colonies. However, higher levels of genetic diversity did not result in more polymorphic workers across single- or multiple-queen colonies. In addition, workers from multiple-queen colonies were consistently smaller and less polymorphic than workers from single-queen colonies. The relationship between task, body size and genetic lineage appeared to be complex. Foragers were significantly larger than brood-tenders, which may provide energetic or ergonomic advantages to the colony. Task specialisation was also often associated with genetic lineage. However, genetic lineage and body size were often correlated with task independently of each other, suggesting that the allocation of workers to tasks is modulated by multiple factors. Overall, these results indicate that an increase in colony genetic diversity does not increase worker size polymorphism but might improve colony homeostasis.