How Brain Fat Conquers Stress

A new paper by Bailey et al. reveals that lipid droplets, crucial organelles for energy storage, can also protect against oxidative stress. In Drosophila larvae, lipid droplets in glia allow neuronal stem cells to keep proliferating under hypoxic conditions. Protection likely involves sequestering vulnerable membrane lipids away from reactive oxygen species

Le manganèse dans l'eau - Elimination du manganèse dans l'eau par traitement biologique

Le manganèse est un élément minéral fréquemment rencontré dans différents types d'eau, surtout souterraines. Dans le cas des eaux de surface, le manganèse peut se trouver lors de pollutions accidentelles où lorsque la rivière reçoit des eaux d'un barrage réservoir en fin de vidange.Des essais de traitement d'une pollution par du manganèse par filtration lente ont été effectués sur un pilote.Les essais ont porté sur différentes concentrations de manganèse pendant des périodes de courte durée. La filtration lente semble très efficace pour l'élimination de ce composé, mais il faut noter que la nitrification biologique est altérée par la présence de fortes concentrations de manganèse.Manganese is a mineral element which is often found in differing types of water. The manganese content is rather consistent, especially in underground waters. In surface waters, manganese can only be found as a result of an occidental pollution or in rivers supplied with water from a dam whose tank has been sewed.This metal is not dangerous for humans but it can create problems in drinking water as it becomes progressively oxidized and thus precipitates in the water supply. This oxidation can produce direct effects like spots on linen or sanitary appliances, but also indirect effects, like important bacterial developments, as well as bacteria protection against biocides used as bactericidal or bacteriostatic agents.This study aims at :1) Underlining the possible effects of manganese in case of an accidental pollution.2) Underlining how much time the system takes to react to an increased manganese content, given that ferric salts which permanently incluse manganese (500 to 600 ppm in the 40 % commercial solution) are used in the coagulation phase.Amongst several methods to eliminate the manganese, the biological oxidation seems to be the most appropriate to this occasional pollution problem. Indeed, it filters are continually contaminated by manganese, the bacteria is likely to oxidize the divalent manganese, resulting in an immediate ceasing of the pollution, without human intervention. This is what the operation aims at.The existing data regarding the biological elimination of manganese in underground waters shows it to be consistent. There is no such data on manganese elimination by slow sand filtration, in surface waters, in case of a short accidental pollution. As far as slow sand filtration is concerned, the available results only represent waters with consistent manganese contents.This study has been carried out with a 50 m3/h pilote system, which was located in Paris surroundings. It was supplied with water from the Marne river and combined physicochemical and biological treatments. The physicochemical phase consisted of a coagulation-flocculation-decantation reaction in a pulsator, with ferric chloride including 500 to 600 ppm divalent manganese. Then, it was quickly filtered through sand, at a flow rate of 5 m/h. The water was subsequently poured into a storage tank in which it remained for around two hours. Then, it was filtered through slow sand filters, which biologically treated it. The filters contained 1 m high of sand and the filtration rate was 1 m/h, which allowed the development of a biological membrane on their surfaces.Simulated manganese pollution tests have been realised as follows :- water with two different manganese contents have been tested (0,5 and 1 mg/l),- ammonium Ions have been simultaneously added to show a possible inhibition of nitrification.Each test lasted around two weeks and time was spent as follows :- polluting agents were continuously added during 3 days (which is the maximum duration of an accidental pollution).These two tests gave the following results :1st test (0,5 manganese/l) :- 35 % of the manganese was eliminated during the coagulation-decantation-quick filtration phase.- 100 % of the manganese was held bock by the slow sand filtration.- An important amount of nitrites appeared in water at the end of the treatment, which suggested an inhibition of the nitrification, or a competition between manganese and ammoniacal oxidation.- After the manganese pollution was stopped, no release of manganese and no inhibition of the nitrification were noticed.2nd test (1 mg manganese/l) :- 25 % of the manganese was eliminated during the coagulation-decantation-quick filtration phase.- 97 % of the manganese was eliminated by slow sand filtration.- In this case, the ammonium and nitrites were eliminated by the biological filtration, which suggested a readaptation of the bacterial flora to this kind of pollution.The result showed chat the biological chain adapts itself very quickly to a rapid increase in water manganese content (no more than 2 hours). Indeed, the biological membrane, which was already contaminated by a permanent accumulation of manganese, reacted very quickly. The first test shows that nitrites appear and confirms the results that other searchers had already obtained before, in there is competition between nitrobacteria and the bacteria which oxidize manganese.A less efficient elimination of organic matter also shows competition during the biodegradation phase.In the second series of tests, a modification of the bacterial flora, due to the first manganese simulated pollution tests, is noticed.These encouraging results allowed us to propose an original system for water treatment, based on a physicochemical treatment and biological slow treatments and, afterwards, a refining phase with combined ozone and granular actiated carbon.In addition to its well-known properties, ozone allows to avoid the possible appearance of nitrites in water

A Comparison of Biomarker Based Incidence Estimators

BACKGROUND: Cross-sectional surveys utilizing biomarkers that test for recent infection provide a convenient and cost effective way to estimate HIV incidence. In particular, the BED assay has been developed for this purpose. Controversy surrounding the way in which false positive results from the biomarker should be handled has lead to a number of different estimators that account for imperfect specificity. We compare the estimators proposed by McDougal et al., Hargrove et al. and McWalter & Welte. METHODOLOGY/PRINCIPAL FINDINGS: The three estimators are analyzed and compared. An identity showing a relationship between the calibration parameters in the McDougal methodology is shown. When the three estimators are tested under a steady state epidemic, which includes individuals who fail to progress on the biomarker, only the McWalter/Welte method recovers an unbiased result. CONCLUSIONS/SIGNIFICANCE: Our analysis shows that the McDougal estimator can be reduced to a formula that only requires calibration of a mean window period and a long-term specificity. This allows simpler calibration techniques to be used and shows that all three estimators can be expressed using the same set of parameters. The McWalter/Welte method is applicable under the least restrictive assumptions and is the least prone to bias of the methods reviewed

Stochastic modeling of cargo transport by teams of molecular motors

Many different types of cellular cargos are transported bidirectionally along microtubules by teams of molecular motors. The motion of this cargo-motors system has been experimentally characterized in vivo as processive with rather persistent directionality. Different theoretical approaches have been suggested in order to explore the origin of this kind of motion. An effective theoretical approach, introduced by M\"uller et al., describes the cargo dynamics as a tug-of-war between different kinds of motors. An alternative approach has been suggested recently by Kunwar et al., who considered the coupling between motor and cargo in more detail. Based on this framework we introduce a model considering single motor positions which we propagate in continuous time. Furthermore, we analyze the possible influence of the discrete time update schemes used in previous publications on the system's dynamic.Comment: Cenference proceedings - Traffic and Granular Flow 1

The role of microtubule movement in bidirectional organelle transport

We study the role of microtubule movement in bidirectional organelle transport in Drosophila S2 cells and show that EGFP-tagged peroxisomes in cells serve as sensitive probes of motor induced, noisy cytoskeletal motions. Multiple peroxisomes move in unison over large time windows and show correlations with microtubule tip positions, indicating rapid microtubule fluctuations in the longitudinal direction. We report the first high-resolution measurement of longitudinal microtubule fluctuations performed by tracing such pairs of co-moving peroxisomes. The resulting picture shows that motor-dependent longitudinal microtubule oscillations contribute significantly to cargo movement along microtubules. Thus, contrary to the conventional view, organelle transport cannot be described solely in terms of cargo movement along stationary microtubule tracks, but instead includes a strong contribution from the movement of the tracks.Comment: 24 pages, 5 figure

PAT proteins, an ancient family of lipid droplet proteins that regulate cellular lipid stores.

The PAT family of lipid droplet proteins includes 5 members in mammals: perilipin, adipose differentiation-related protein (ADRP), tail-interacting protein of 47 kDa (TIP47), S3-12, and OXPAT. Members of this family are also present in evolutionarily distant organisms, including insects, slime molds and fungi. All PAT proteins share sequence similarity and the ability to bind intracellular lipid droplets, either constitutively or in response to metabolic stimuli, such as increased lipid flux into or out of lipid droplets. Positioned at the lipid droplet surface, PAT proteins manage access of other proteins (lipases) to the lipid esters within the lipid droplet core and can interact with cellular machinery important for lipid droplet biogenesis. Genetic variations in the gene for the best-characterized of the mammalian PAT proteins, perilipin, have been associated with metabolic phenotypes, including type 2 diabetes mellitus and obesity. In this review, we discuss how the PAT proteins regulate cellular lipid metabolism both in mammals and in model organisms

Tuberculosis in a South African prison – a transmission modelling analysis

Background. Prisons are recognised internationally as institutions with very high tuberculosis (TB) burdens where transmission is predominantly determined by contact between infectious and susceptible prisoners. A recent South African court case described the conditions under which prisoners awaiting trial were kept. With the use of these data, a   mathematical model was developed to explore the interactions between incarceration conditions and TB control measures.Methods. Cell dimensions, cell occupancy, lock-up time, TB incidence and treatment delays were derived from court evidence and judicial reports. Using the Wells-Riley equation and probability analyses of contact between prisoners, we estimated the current TB transmission probability within prison cells, and estimated transmission probabilities of improved levels of case finding in combination with implementation of national and  international minimum standards for incarceration.Results. Levels of overcrowding (230%) in communal cells and poor TB case finding result in annual TB transmission risks of 90% per annum. Implementing current national or international cell occupancy  recommendations would reduce TB transmission probabilities by 30% and 50%, respectively. Improved passive case finding, modest ventilation increase or decreased lock-up time would minimally impact on transmission if introduced individually. However, active case finding together with implementation of minimum national and international standards of incarceration could reduce transmission by 50% and 94%, respectively.Conclusions. Current  conditions of detention for awaiting trial prisoners are highly conducive for spread of drug-sensitive and drug-resistant TB. Combinations of simple well-established scientific control measures should be implemented urgently.S Afr Med J 2011;101:809-813

Tuberculosis in a South African prison - a transmission modelling analysis

Background. Prisons are recognised internationally as institutions with very high tuberculosis (TB) burdens where transmission is predominantly determined by contact between infectious and susceptible prisoners. A. recent South African court case described the conditions under which prisoners awaiting trial were kept. With the use of these data, a mathematical model was developed to explore the interactions between incarceration conditions and TB control measures. Methods. Cell dimensions, cell occupancy, lock-up time, TB incidence and treatment delays were derived from court evidence and judicial reports. Using the Wells-Riley equation and probability analyses of contact between prisoners, we estimated the current TB transmission probability within prison cells, and estimated transmission probabilities of improved levels of case finding in combination with implementation of national and international minimum standards for incarceration. Results. Levels of overcrowding (230%) in communal cells and Poor TB case finding result in annual TB transmission risks of 90% per annum. Implementing current national or international cell occupancy recommendations would reduce TB transmission probabilities by 30% and 50%, respectively. Improved passive case finding, modest ventilation increase or decreased lock-up time would minimally impact on transmission if introduced individually. However, active case finding together with implementation of minimum national and international standards of incarceration could reduce transmission by 50% and 94%, respectively. Conclusions. Current conditions of detention for awaiting-trial prisoners are highly conducive for spread of drug-sensitive and drug-resistant TB. Combinations of simple well-established scientific control measures should be implemented urgently