Differential regulation of melatonin synthesis genes and phototransduction genes in embryonic chicken retina and cultured retinal precursor cells.

International audiencePhotoreceptor differentiation involves the activation of two specific sets of genes; those encoding the proteins of the phototransduction cascade and those encoding the enzymes of the melatonin synthesis pathway, arylalkylamine N-acetyltransferase (AANAT) and hydroxyindole O-methyltransferase (HIOMT). The purpose of the present study was to examine the conditions of AANAT and HIOMT gene activation, relative to that of selected phototransduction markers (alpha-transducin and opsins), in both in vivo and in vitro differentiating photoreceptors of the chicken retina

An Optimized Most Probable Number (MPN) Method to Assess the Number of Thermophilic Free-Living Amoebae (FLA) in Water Samples

International audienceDetection and quantification of pathogenic free-living amoebae (FLA) in water samples is critical for assessing water quality and for disease management issues. The most probable number (MPN) is commonly used to account for FLA in water. Nevertheless, this requires a high number of water replicates and working volumes, and a consequent number of non-nutrient agar (NNA)-plates seeded with Escherichia coli. Herein, we aimed at optimizing this difficult method, taking also into account key factors such as (i) the counting method, (ii) the delay between sample collection and sample processing, and (iii) the temperature during water sample transportation. To simplify the MPN method, we filtrated 1 × 1000 and 1 × 100 mL water samples, and cellulose acetate filters were cut in 10 parts and inverted on NNA-plates overlaid with E. coli. The comparison between the classical and our optimized MPN method showed that the final counts were similar, therefore validating the use of the optimized method. Our results also showed that for thermophilic FLA (such as Naegleria fowleri), water samples can be kept at around +30 • C and processed within 24 h. This improved MPN method is now routinely used in our laboratory to control Naegleria sp. in the water samples in Guadeloupe

Morphometric characterisation of an arboreal lizard ( Anolis marmoratus marmoratus)

International audienceHydroxyindole-O-methyltransferase (HIOMT) catalyzes the final step of melatonin biosynthesis and appears to be specifically expressed in the pineal gland and in the retina. This review deals with the regulation of HIOMT by environmental light and with the developmental aspects of HIOMT expression in chicken and rat. Early studies based on HIOMT activity measurements and more recent studies involving cDNA hybridization to HIOMT mRNA are taken into consideration. Together, the data reveal that long term regulation of HIOMT by light would rely on a day/night rhythm of HIOMT gene transcription, coupled to a slow turnover of the protein. Rapid changes in HIOMT mRNA levels and early expression during embryonic development suggest that further studies on this gene may shed light on the molecular mechanisms involved in the differentiation of the melatoninergic function and in its regulation by light, both in the pineal gland and in the retina

Soil is the origin for the presence of Naegleria fowleri in the thermal recreational waters

International audienceNaegleria fowleri is found in most geothermal baths of Guadeloupe and has been responsible for the death of a 9-year-old boy who swam in one of these baths in 2008. We wanted to determine the origin for the presence of this amoeba in the water.Water samples were taken at the origin of the geothermal sources and at the arrival in the baths. After filtration, cultures were made and the number of Naegleria present was determined using the most probable number method. Soil samples collected in the proximity of the baths were also tested for the presence of thermophilic amoebae. The species identification was obtained by PCR. During three consecutivemonths, no Naegleria could be found at the origin of any geothermal source tested. In contrast, N. fowleri was isolated at least once in all baths at the arrival of the water, except one. Thermophilic amoebae could be found in each soil sample, especially near the baths located at a lower altitude, but N. fowleri was only isolated near two baths, which were also the baths most often contaminated with this species. So it appears that the contamination of the water with N. fowleri occurs after emerging from the geothermal source when the water runs over the soil. Therefore, it should be possible to reduce the concentration of N. fowleri in thegeothermal baths of Guadeloupe to for example less than 1 N. fowleri/10 L by installing a pipeline between the geothermal sources and the baths and by preventing flooding water from entering the baths after rainfall. By taking these measures, we were able to eliminate N. fowleri from a poollocated inside a reeducation clinic

Survey of Naegleria fowleri in Geothermal Recreational Waters of Guadeloupe (French West Indies)

In 2008 a fatal case of primary amoebic meningoencephalitis, due to the amoeboflagellate Naegleria fowleri, occurred in Guadeloupe, French West Indies, after a child swam in a bath fed with geothermal water. In order to improve the knowledge on free-living amoebae in this tropical part of France, we investigated on a monthly basis, the presence of Naegleria spp. in the recreational baths, and stream waters which feed them. A total of 73 water samples, 48 sediments and 54 swabs samples were collected from 6 sampling points between June 2011 and July 2012. The water samples were filtered and the filters transferred to non-nutrient agar plates seeded with a heat-killed suspension of Escherichia coli while sediment and swab samples were placed directly on these plates. The plates were incubated at 44uC for the selective isolation of thermophilic Naegleria. To identify the Naegleria isolates the internal transcribed spacers, including the 5.8S rDNA, were amplified by polymerase chain reaction and the sequence of the PCR products was determined. Thermophilic amoebae were present at nearly all collection sites. The pathogenic N. fowleri was the most frequently encountered thermophilic species followed by N. lovaniensis. The concentration of N. fowleri was rather low in most water samples, ranging from 0 to 22 per liter. Sequencing revealed that all N. fowleri isolates belonged to a common Euro-American genotype, the same as detected in the human case in Guadeloupe. These investigations need to be continued in order to counsel the health authorities about prevention measures, because these recreational thermal baths are used daily by loca

Melatonin synthesis pathway: circadian regulation of the genes encoding the key enzymes in the chicken pineal gland and retina

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Distribution of sequenced isolates from the different geothermal baths of Guadeloupe.

<p>Distribution of sequenced isolates from the different geothermal baths of Guadeloupe.</p

Number of <i>Naegleria fowleri</i> isolated from the most frequented baths of Guadeloupe according to temperature and pH (2011–12).

<p>ND : non determined.</p

Survey of free-living amoeba isolated from geothermal recreational waters of Guadeloupe on a montly basis (2011).

<p><b>Sp. :</b> thermophilic amoebae non-Naegleria sp., <b>N.l</b> : Naegleria lovaniensis., <b>N.f</b> : Naegleria fowleri,</p><p>(n) number of amoebae per liter of water; (+ ou -) presence or absence in sediment or swab; (blank) not investigated.</p

ITS1 sequences of the three isolates identified in the different geothermal waters of Guadeloupe.

<p>ITS1 sequences of the three isolates identified in the different geothermal waters of Guadeloupe.</p