Microcalorimetric characterization of seasonal metabolic trends in marine microcosms

A microcalorimetric and oximetric circulation system has been used to describe the emergence of seasonal adaptative changes occurring in marine microcosms at the water-sediment interface. The microcosms were prepared from three stations: one estuarine and two lagoonal. They were submitted to the same acute eutrophication, using peptone, and the evolutions shown by power-time and oxygen-time curves were compared over a 2-yr period. The metabolic heat productions and their oxidative counterparts are well correlated with seasonal trends. In summer, the microcalorimetric curves are typically unimodal, with very low dispersion, and a low thermodynamic steady state is attained in a few hours (40–50 μW), indicating an efficient, integrated regulatory mechanism; oxygen conditions evolute towards anoxia within 6 to 8 h. In winter, the power-time curves are typically sigmoid, with low dispersion; the thermodynamic steady state attained indicates a high maintenance energy requirement (140–150 μW), probably due to microbial populations less adapted to eutrophication stress. In winter, oxygen depletion is only partial and a plateau is attained within limits of 80 to 40% of initial saturation, and lasts 1 wk at least. Spring and autumn responses are very heterogeneous, varying from summer to winter types and displaying evolutive bimodal patterns. The sea-water-sediment interfaces from different estuarine and lagoonal habitats with distinct physical and chemical characteristics, but subjected to similar environmental and seasonal perturbations, show similar energetic patterns according to the seasons. It is proposed, as a working hypothesis, that the seasonal variations of the microcalorimetric response to experimental eutrophication are the expression of a global homeostatic adaptative memory, determined by natural environmental perturbations. Spring and autumn can be considered as intermediate periods within which a seasonal “adaptative memory” is replaced gradually by another one. The heterogeneity of the microcalorimetric response in spring and autumn microcosms could be related to an asynchronous maturation for the different components of the benthic ecosystem.     

Experimental Assessment of the Water Quality Influence on the Phosphorus Uptake of an Invasive Aquatic Plant: Biological Responses throughout Its Phenological Stage

Understanding how an invasive plant can colonize a large range of environments is still a great challenge in freshwater ecology. For the first time, we assessed the relative importance of four factors on the phosphorus uptake and growth of an invasive macrophyte Elodea nuttallii (Planch.) St. John. This study provided data on its phenotypic plasticity, which is frequently suggested as an important mechanism but remains poorly investigated. The phosphorus uptake of two Elodea nuttallii subpopulations was experimentally studied under contrasting environmental conditions. Plants were sampled in the Rhine floodplain and in the Northern Vosges mountains, and then maintained in aquaria in hard (Rhine) or soft (Vosges) water. Under these conditions, we tested the influence of two trophic states (eutrophic state, 100 μg.l⁻¹ P-PO₄ ³⁻ and hypertrophic state, 300 μg.l⁻¹ P-PO₄ ³⁻) on the P metabolism of plant subpopulations collected at three seasons (winter, spring and summer). Elodea nuttallii was able to absorb high levels of phosphorus through its shoots and enhance its phosphorus uptake, continually, after an increase of the resource availability (hypertrophic > eutrophic). The lowest efficiency in nutrient use was observed in winter, whereas the highest was recorded in spring, what revealed thus a storage strategy which can be beneficial to new shoots. This experiment provided evidence that generally, the water trophic state is the main factor governing P uptake, and the mineral status (softwater > hardwater) of the stream water is the second main factor. The phenological stage appeared to be a confounding factor to P level in water. Nonetheless, phenology played a role in P turnover in the plant. Finally, phenotypic plasticity allows both subpopulations to adapt to a changing environment.     

Physiological Knockout of the Envelope Gene of the Single-Copy ERV-3 Human Endogenous Retrovirus in a Fraction of the Caucasian Population

ERV-3 is an evolutionarily conserved single-copy human endogenous retrovirus with a coding envelope gene potentially involved in important placental functions. We have investigated the sequence variability of this gene among 150 unrelated Caucasian individuals and found eight polymorphic sites. One of them corresponds to the introduction of a stop codon resulting in the production of a severely truncated ERV-3 envelope protein lacking both the fusion peptide and the immunosuppressive domain of the protein. The stop codon is observed in a homozygous state in approximately 1% of Caucasian individuals without evidence for counterselection, thus precluding the involvement of any essential function of the gene in placental implantation and development. This natural knockout provides a mean to investigate other potential roles for this otherwise highly conserved gene.     

Validation procedures of sedimentation field-flow fractionation techniques for biological applications

Sedimentation field-flow fractionation (SdFFF) offers great potential for the separation of submicrometer and micrometer-sized species. The availability of commercial instrumentation and the versatility of this method originated its success. At this stage of development, SdFFF techniques are mature enough for use in analytical research, development and even routine work. However, prior to their use, these techniques like any other methodologies, have to be validated. As the application of SdFFF techniques to cell separation is being constantly developed, we have investigated separation performance according to validation rules classically defined for separation methods (chromatography) in the case of cellular materials.     

Genetic parameters and genetic trends in the Chinese × European Tiameslan composite pig line. II. Genetic trends

The Tiameslan line was created between 1983 and 1985 by mating Meishan × Jiaxing crossbred Chinese boars with sows from the Laconie composite male line. The Tiameslan line has been selected since then on an index combining average backfat thickness (ABT) and days from 20 to 100 kg (DT). Direct and correlated responses to 11 years of selection were estimated using BLUP methodology applied to a multiple trait animal model. A total of 11 traits were considered, i.e.: ABT, DT, body weight at 4 (W4w), 8 (W8w) and 22 (W22w) weeks of age, teat number (TEAT), number of good teats (GTEAT), total number of piglets born (TNB), born alive (NBA) and weaned (NW) per litter, and birth to weaning survival rate (SURV). Performance data from a total of 4 881 males and 4 799 females from 1 341 litters were analysed. The models included both direct and maternal effects for ABT, W4w and W8w. Male and female performances were considered as different traits for W22w, DT and ABT. Genetic parameters estimated in another paper (Zhang et al., Genet. Sel. Evol. 32 (2000) 41-56) were used to perform the analyses. Favourable phenotypic (ΔP) and direct genetic trends (ΔG_d) were obtained for post-weaning growth traits and ABT. Trends for maternal effects were limited. Phenotypic and genetic trends were larger in females than in males for ABT (e.g. ΔG_d = -0.48 vs. -0.38 mm/year), were larger in males for W22w (ΔG_d = 0.90 vs. 0.58 kg/year) and were similar in both sexes for DT (ΔG_d = -0.54 vs. -0.55 day/year). Phenotypic and genetic trends were slightly favourable for W4w, W8w, TEAT and GTEAT and close to zero for reproductive traits.     

Kleptoplastidic benthic foraminifera from aphotic habitats: insights into assimilation of inorganic C,N and S studied with sub-cellular resolution

The assimilation of inorganic compounds in foraminiferal metabolism compared to predation or organic matter assimilation is unknown. Here, we investigate possible inorganic-compound assimilation in Nonionellina labradorica, a common kleptoplastidic benthic foraminifer from Arctic and North Atlantic sublittoral regions. The objectives were to identify the source of the foraminiferal kleptoplasts, assess their photosynthetic functionality in light and darkness and investigate inorganic nitrogen and sulfate assimilation. We used DNA barcoding of a ~ 830 bp fragment from the SSU rDNA to identify the kleptoplasts and correlated transmission electron microscopy and nanometre-scale secondary ion mass spectrometry (TEM-NanoSIMS) isotopic imaging to study ¹³C-bicarbonate, ¹⁵N-ammonium and ³⁴S-sulfate uptake. In addition, respiration rate measurements were determined to assess the response of N. labradorica to light. The DNA sequences established that over 80% of the kleptoplasts belonged to Thalassiosira (with 96%–99% identity), a cosmopolitan planktonic diatom. TEM-NanoSIMS imaging revealed degraded cytoplasm and an absence of ¹³C assimilation in foraminifera exposed to light. Oxygen measurements showed higher respiration rates under light than dark conditions, and no O₂ production was detected. These results indicate that the photosynthetic pathways in N. labradorica are not functional. Furthermore, N. labradorica assimilated both ¹⁵N-ammonium and ³⁴S-sulfate into its cytoplasm, which suggests that foraminifera might have several ammonium or sulfate assimilation pathways, involving either the kleptoplasts or bona fide foraminiferal pathway(s) not yet identified.     

Gas chromatographic determination of meprobamate in human plasma

A simplified and rapid gas chromatographic method has been developed for the determination of meprobamate in human plasma. The procedure includes a single-step extraction of alkalinized sample with chloroform, and chromatography on a non-polar fused-silica capillary column with flame ionization detection. The method is accurate (97.7 ± 5.7% at 20 mg/l) and precise (maximum coefficient of variation of 9.5%). It provides an alternative to existing methods and is particularly suitable for toxicological studies.     

Effect of sodium diethyl dithiocarbamate on mitogen induced lymphoproliferation "in vitro"

Sodium diethyl dithiocarbamate (DTC) is a low molecular weight sulphur compound which has been shown to be an adjuvant of immunity in vivo. In this report, DTC was shown to inhibit in vitro DNA-synthesis of human peripheral blood lymphocytes stimulated by phytohemagglutinin or concanavalin A. DTC could act directly at the cellular level and indirectly by interfering with culture medium or lectins.