Osmotic stress tolerance in semi-terrestrial tardigrades

Heidemann, Nanna W. T., Smith, Daniel K., Hygum, Thomas L., Stapane, Lilian, Clausen, Lykke K. B., Jørgensen, Aslak, Helix-Nielsen, Claus, Møbjerg, Nadja (2016): Osmotic stress tolerance in semi-terrestrial tardigrades. Zoological Journal of the Linnean Society 178 (4): 912-918, DOI: 10.1111/zoj.12502, URL: http://dx.doi.org/10.1111/zoj.1250

The Cobalamin-Binding Protein in Zebrafish Is an Intermediate between the Three Cobalamin-Binding Proteins in Human

In humans, three soluble extracellular cobalamin-binding proteins; transcobalamin (TC), intrinsic factor (IF), and haptocorrin (HC), are involved in the uptake and transport of cobalamin. In this study, we investigate a cobalamin-binding protein from zebrafish (Danio rerio) and summarize current knowledge concerning the phylogenetic evolution of kindred proteins. We identified a cobalamin binding capacity in zebrafish protein extracts (8.2 pmol/fish) and ambient water (13.5 pmol/fish) associated with a single protein. The protein showed resistance toward degradation by trypsin and chymotrypsin (like human IF, but unlike human HC and TC). The cobalamin analogue, cobinamide, bound weaker to the zebrafish cobalamin binder than to human HC, but stronger than to human TC and IF. Affinity for another analogue, adenosyl-pseudo-cobalamin was low compared with human HC and TC, but high compared with human IF. The absorbance spectrum of the purified protein in complex with hydroxo-cobalamin resembled those of human HC and IF, but not TC. We searched available databases to further explore the phylogenies of the three cobalamin-binding proteins in higher vertebrates. Apparently, TC-like proteins are the oldest evolutionary derivatives followed by IF and HC (the latter being present only in reptiles and most but not all mammals). Our findings suggest that the only cobalamin-binding protein in zebrafish is an intermediate between the three human cobalamin binders. These findings support the hypothesis about a common ancestral gene for all cobalamin-binding proteins in higher vertebrates

Egg and faecal pellet production of Calanus finmarchicusfemales from controlled mesocosms and in situ populations:influence of age and feeding history

International audienc

Measurement of bacterial size via image analysis of epifluorescence preparations: description of an inexpensive system and solutions to some of the most common problems

11 páginas, 9 figuras, 3 tables[EN] Computerized image-analysis of epifluorescence preparations is the most accurate and simple method for the estimation of bacterial size. We present a simple and inexpensive image-analysis system used to measure and count planktonic bacteria and presently in operation in our laboratory. We show that there is a wide range of image exposures (brightness) over which the system performs correctly. Even though the procedure involves some steps that depend upon operator intervention, the results obtained are highly reproducible and we have estimated the among-operator variability at 5%. We then discuss the advantages and disadvantages of different algorithms used for the estimation of volume from two-dimensional images and we identify those that perform better for curved and unusual cells. We finally estimate that 4 to 6 images and 200 - 250 cells are the optimal number of images to be processed and cells to be measured to obtain accurate estimates of population values with the minimum effort. These calibrations should be useful to all those laboratories that are implementing image-analysis systems[ES] El análisis de imágenes obtenidas a partir de preparaciones de epifluorescencia es el método más sencillo y preciso para medir el tamaño bacteriano. En este trabajo se presenta un sistema de análisis de imágenes sencillo y asequible, actualmente en funcionamiento en nuestro laboratorio, desarrollado para medir y contar bacterias planctónicas. Se demuestra que el sistema funciona correctamente dentro de un rango amplio de brillo de imagen. Aunque algunos pasos del proceso dependen del operador, los resultados obtenidos fueron altamente reproducibles, y se estimó una variabilidad entre operadores del 5%. Se discuten las ventajas de los diferentes algoritmos usados para calcular el biovolumen a partir de imágenes de dos dimensiones, e identificamos el algoritmo que funciona mejor en células curvados o de formas inusuales. Finalmente, se estimó que para obtener medidas precisas del tamaño medio de la población con el mínimo esfuerzo se debían procesar entre 4 y 6 imágenes y contar entre 200 y 250 células. La información presentada en este trabajo puede ser útil para aquellos laboratorios que deseen desarrollar sistemas de análisis de imágenes parecidosThis paper was developed while working for the EU MAS2-CT93-0077, EU MAS3-CT95-0016 (MEDEA) projects and partially financed by project DGICYT PB91-075Peer reviewe

Data E sigismundi radiation tolerance_Jönsson et al

Doses of gamma ray are given in the unit "Gray"

Data from: Tolerance to gamma radiation in the marine heterotardigrade, Echiniscoides sigismundi

Tardigrades belong to the most radiation tolerant animals on Earth, as documented by a number of studies using both low-LET and high-LET ionizing radiation. Previous studies have focused on semi-terrestrial species, which are also very tolerant to desiccation. The predominant view on the reason for the high radiation tolerance among these semi-terrestrial species, is that it relies on molecular mechanisms that evolved as adaptations for surviving dehydration. In this study we report the first study on radiation tolerance in a marine tardigrade, Echiniscoides sigismundi. Adult specimens in the hydrated active state were exposed to doses of gamma radiation from 100 to 5000 Gy. The results showed little effect of radiation at 100 and 500 Gy but a clear decline in activity at 1000 Gy and higher. The highest dose survived was 4000 Gy, at which ca. 8% of the tardigrades were active 7 days after irradiation. LD50 in the first 7 days after irradiation was in the range of 1100-1600 Gy. Compared to previous studies on radiation tolerance in semi-terrestrial and limnic tardigrades, Echiniscoides sigismundi seems to have a lower tolerance. However, the species still fits into the category of tardigrades that have high tolerance to both desiccation and radiation, supporting the hypothesis that radiation tolerance is a by-product of adaptative mechanisms to survive desiccation. More studies on radiation tolerance in tardigrade species adapted to permanently wet conditions, both marine and freshwater, are needed to obtain a more comprehensive picture of the patterns of radiation tolerance