Dynamics of bubbles created by plasma in heptane for micro-gap conditions.

The determination of the initial pressure at the bubble wall created by a discharge in heptane for micro-gap conditions cannot be determined straightforwardly by modeling the time-oscillations of the bubble. The resolution of the Gilmore equation gives the same solutions beyond 1 µs typically for various sets of initial parameters, making impossible the determination of the initial pressure at the bubble wall. Furthermore, the very first instant of the bubble formation is not easily accessible at very short time scales because of the plasma emission. Since the pressure waves propagate in the liquid, it is much easier to gain information on the first instants of the bubble formation by studying the pressure field far from the emission source. Then, it is possible to deduce by modeling what happened at the beginning of the emission of the pressure waves. The proposed solution consists in looking at the oscillations affecting another bubble located at least twice farther from the interelectrode gap than the maximum radius reached by the discharge bubble. The initial plasma pressure can be determined by this method.

Effects of Ar-H2-N2 microwave plasma on chitosan and its nanoliposomes blend thin films designed for tissue engineering applications.

This work addresses the functionalization of chitosan thin films and its nanoliposomes blend films by a microwave-excited Ar/N2/H2 surface-wave plasma treatment which was found an effective tool to modify surface properties. Changes in the film properties (wettability, chemical composition, morphology) induced by the plasma treatment are studied using water contact angle measurements, X-ray photoelectron spectroscopy and scanning probe microscopy. The results suggest that hydrophilicity of the films is improved by plasma treatment in a plasma condition dependency manner. Water contact angle of chitosan films before and after plasma treatment are, respectively, 101° and 27°. Besides chemical changes on the surface, the nanoliposomes incorporation and plasma treatment also induce morphological modifications. Moreover, a correlation is found between the nanoliposomes composition and size, and the effects of plasma treatment. It is shown that the plasma treatment significantly improves the chitosan film functionalization. The effect of N2 content (88% and 100%) in the plasma gas mixture on the film etching is also pointed out.

Preliminary analysis of the pandemic H1N1 influenza on Reunion Island (Indian Ocean): surveillance trends (July to mid-September 2009).

First infections with the 2009 pandemic H1N1 influenza virus were identified on Reunion Island in July 2009. By the end of July, sustained community transmission of the virus was established. Pandemic H1N1 influenza activity peaked during week 35 (24 to 30 August), five weeks after the beginning of the epidemic and has been declining since week 36. We report preliminary epidemiological characteristics of the pandemic on Reunion Island in 2009 until week 37 ending September 13.

Cortex, a Drosophila gene required to complete oocyte meiosis, is a member of the Cdc20/fizzy protein family.

Mutations in cortex and grauzone cause abnormal arrest in Drosophila female meiosis. cortex was mapped to a 14 kb interval in 26F-27A by the male recombination mapping method. While these experiments mapped the gene accurately, they also illustrated some complexities of this method. Rescue results showed that a 2.8 kb genomic fragment from this interval was able to fully rescue the cortex phenotype. The 2.8 kb rescuing fragment contains a single open reading frame. The predicted amino acid sequence indicates that cortex encodes a WD-repeat protein and is a distant member of the Cdc20 protein family. Results from a developmental Northern analysis showed that the cortex transcript is expressed at high levels during oogenesis and early embryogenesis. Interestingly, the meiotic metaphase-anaphase II arrest defect in embryos laid by cortex homozygous females resembles the mitotic metaphase-anaphase defects observed in yeast cdc20 mutants. The predicted nature of the Cortex protein, together with the observed meiotic phenotype in cortex mutants, suggest that a similar pathway to the cdc20 dependent APC-mediated proteolysis pathway, which governs the metaphase-anaphase transition in mitosis, is also important in regulating oocyte meiosis.

Onset of zygotic transcription and maternal transcript legacy in the rabbit embryo.

Onset of zygotic transcription is progressive from the one-cell stage onward in the rabbit embryo. Maternal transcripts remain fairly stable until the 8-16 cell stage when major transcriptional activation of the zygotic genome takes place. To understand the mechanisms of the maternal-to-zygotic transition in the genetic information governing development, we asked whether a progressive synthesis of zygotic transcripts takes over the maternal molecules, or whether the synthesis of zygotic transcripts is very abrupt and independent of the persistence of the maternal counterparts. To answer this question, we set up mRNA differential display experiments comparing the mRNA content of rabbit embryos at different stages during the preimplantation period. We isolated eight zygotic transcripts whose synthesis is abruptly turned on at the 8-16 cell stage. These transcripts are involved in general cellular metabolism and their maternal counterparts are still present up to the four-cell and even the 8-16 cell stage. This identification of early zygotic transcripts suggests that global long range modifications of chromatin structure result in a rapid increase in transcription rates during the major transcriptional activation of the zygotic genome.

The only function of Grauzone required for Drosophila oocyte meiosis is transcriptional activation of the cortex gene.

The grauzone and cortex genes are required for the completion of meiosis in Drosophila oocytes. The grauzone gene encodes a C2H2-type zinc-finger transcription factor that binds to the cortex promoter and is necessary for high-level activation of cortex transcription. Here we define the region of the cortex promoter to which Grauzone binds and show that the binding occurs through the C-terminal, zinc-finger-rich region of the protein. Mutations in two out of the five grauzone alleles result in single amino acid changes within different zinc-finger motifs. Both of these mutations result in the inability of Grauzone to bind DNA effectively. To determine the mechanism by which Grauzone regulates meiosis, transgenic flies were produced with an extra copy of the cortex gene in homozygous grauzone females. This transgene rescued the meiosis arrest of embryos from these mutants and allowed their complete development, indicating that activation of cortex transcription is the primary role of Grauzone during Drosophila oogenesis. These experiments further define a new transcriptional pathway that controls the meiotic cell cycle in Drosophila oocytes.

Differential regulation of the translation and the stability of two maternal transcripts in preimplantation rabbit embryos.

In most species, transcription is essentially silent during the first mitotic cell cycles that follow fertilization. This means that the regulation of gene expression in early embryos heavily relies on the translational activation or inactivation of maternal mRNAs. In mammals, the mechanisms that control the translation of maternal mRNAs have been mainly studied in the mouse when maternal to zygotic transition occurs after the first mitotic division. In other mammalian species, however, this transition occurs later after several cell cycles, and little is known concerning the regulation of maternal information during this period. To address this question, we have used rabbit pre-implantation embryos to analyze the translational activation and stability of two maternal mRNAs, mm 41 and mm61. During the cleavage period, these mRNAs exhibit distinct kinetics for both their translational activation and degradation. In addition, these mRNAs both undergo cytoplasmic polyadenylation but with different efficiencies. This polyadenylation was functionally correlated with the translational activation of these mRNAs; inhibiting polyadenylation prevented translational activation. The differential efficiency of cytoplasmic polyadenylation, driven by cis-elements in the 3' untranslated region of these mRNAs, was also observed in Xenopus laevis embryos, which emphasizes the high conservation of this mechanism between species.

Completion of meiosis in Drosophila oocytes requires transcriptional control by grauzone, a new zinc finger protein.

Mutations in grauzone or cortex cause abnormal arrest in Drosophila female meiosis. We cloned grauzone and identified it as a C2H2-type zinc finger transcription factor. The grauzone transcript is present in ovaries and at later developmental stages. A Grauzone-GFP fusion protein is functional and localizes to nuclei of both nurse cells and follicle cells during oogenesis. Three lines of evidence indicate that grauzone and cortex interact: reducing cortex function enhanced the grauzone mutant phenotype; cortex transcript abundance is reduced in the absence of grauzone function and Grauzone protein binds to the cortex promoter. These results demonstrate that activation of cortex transcription by grauzone is necessary for the completion of meiosis in Drosophila oocytes, and establish a new pathway that specifically regulates the female meiotic cell cycle.

Road accident statistics: discrepancies between police and hospital data in a French island.

In most developed countries, information on road crashes are routinely collected by the police. However, comparison of police records and hospital data underlines a deficit of the number of road accidents in the routine statistics. In La Réunion, a French overseas dependency, an epidemiological study of injuries leading to hospitalisation or deaths has been performed from June 1993 to June 1994. The comparison between hospital data and police records showed that only 37.3% of non-fatally traffic-injured in-patients were recorded by the police. Length of stay in hospital, physician in charge of the first aid, urban place of the crash, type of vehicle involved, day and time of the crash and blood alcohol concentration were significantly associated with the presence in the police file. Police overestimated the severity of the injuries. Police notified 100 deaths on the 115 counted by the study. In France, non-fatally traffic-injured should be followed 30 days to improve quality of police death records. A capture-recapture method was used to estimate the total number of injured people. The capture-recapture method consists in merging information from several sources of notification to determine the real number of cases in the population and the exhaustivity of each source. We estimated that 346 subjects were injured in one month whereas police data recorded only 87 and hospital data 137. This method seems interesting to use in routine after validation when unique personal identifiers are available.

Injuries in a problematic socioeconomic context: a population-based study in Réunion, Indian Ocean, 1993-1994. GEAR. Groupement d'Etude sur les Accidents à la Réunion.

BACKGROUND: This study was designed to estimate the incidence and describe the characteristics of injuries during a one-year period in the French island of Réunion, Indian Ocean, a defined geographic population with socioeconomic problems. METHODS: Cases were injuries from accidents (unintentional injuries), self-inflicted injuries (suicides and attempted suicides), or injuries purposely inflicted by other people, that resulted in hospital admission or death. Patients and injury characteristics were recorded prospectively, alternately every other week, in all emergency rooms on the island; all death certificates were studied. RESULTS: The overall annual incidence of injuries was 1578 per 100,000 residents. The three main causes of injury were (i) falls on the same level (23.6%), (ii) poisoning (23.0%) and (iii) traffic accidents (21.5%). Of the traffic accident cases, 44% were motorcyclists (mostly mopeds) and more than half of the cases were 15-25 years old. Suicides and attempted suicides accounted for 80.9% of poisonings, 35.5% of immediately fatal injuries, and 19.6% of non-fatal injuries. Homicides and assaults accounted for 8.3% of all injuries. The employment rate was lower for injured patients than in the total Réunion population (standardized ratio for males: 74; P < 0.001). Half of the injured hospitalized patients had an Injury Severity Score < 5 and 8 days after hospitalization, 83.5% of patients had returned home. CONCLUSION: Injury epidemiology may be affected by different demographic, socioeconomic, cultural and geographical factors. Targeted studies are therefore necessary to guide injury prevention measures.

Identification of maternal transcripts that progressively disappear during the cleavage period of rabbit embryos.

In order to characterize the changes that occur in the population of maternally inherited transcripts before the transition from maternal to zygotic control of embryonic development (MZT) in mammals, we used rabbit embryos where zygotic transcription becomes necessary only after the fourth cleavage division, during the second day that follows fertilization. In the present work we have associated mRNA differential display and an RT-PCR based-method that allows amplification of the whole population of messengers to identify and characterize maternal transcripts which are degraded throughout this early period of development. While there is no major degradation of the polyA RNA population before MZT we identify 4 transcripts which progressively disappear up until the 8-16 cell stage. We also show that the degradation of one of these maternal messengers is controlled by zygotic transcription, which is not the case for the three others. This messenger shows homology with the human FGF9 gene and is potentially a good candidate to address the question of the molecular control of maternal to zygotic transition in early mammalian embryogenesis.

[Simultaneous determination of the toxicologically relevant elements: lead, cadmium, and nickel with graphite furnace atomic absorption spectrometry]. / Simultanbestimmungsmethode für die toxikologisch relevanten Elemente Blei, Cadmium und Nickel mittels Graphitrohr-Atomabsorptionsspektrometrie (GF-AAS).

A new generation of graphite furnace atomic absorption spectrometer enables the simultaneous determination of several trace elements. Using an optimized temperature-time-program for ashing and atomization, the Smith-Hieftje background correction and a matrix modifier, the determination of Pb, Cd and Ni in one run is possible. The detection limits of the new method of 0,039 mg Pb, 0,006 mg Cd and 0,022 mg Ni per kg sample, permit the determination of these elements in soils, foodstuffs and human food. These detection limits comply with the guidelines of the "Zentrale Erfassungs- und Bewertungsstelle für Umweltchemikalien" (central registration- and assessment office for environmental chemicals) of the "Bundesgesundheitsamt" (german public health department). The new multielement method reduces measurement time and costs, i.e. graphite tubes, gas, matrix modifier, reference material and sample solution, in comparison to conventional single-element GF-AAS.