Sex determination and temperature-induced sex differentiation in three natural populations of Nile tilapia (Oreochromis niloticus) adapted to extreme temperature conditions

As a species of major interest for aquaculture, the sex determination system (SDS) of Nile tilapia, Oreochromis niloticus, has been widely investigated. In this species, sex determination is considered to be governed by the interactions between a complex system of genetic sex determination factors (GSD) and the influence of temperature (TSD) during a critical period. Previous studies were exclusively carried out on domestic stocks with the genetic and maintenance limitations associated. Given the wide distribution and adaptation potential of the Nile tilapia, we investigated under controlled conditions the sex determination system of natural populations adapted to three extreme thermal regimes: stable extreme environments in Ethiopia, either cold temperatures in a highland lake (Lake Koka), or warm temperatures in hydrothermal springs (Lake Metahara), and an environment with large seasonal variations in Ghana (Kpandu, Lake Volta). The sex ratio analysis was conducted on progenies reared under constant basal (27 degrees C) or high (36 degrees C) temperatures during the 30 days following yolk-sac resorption. Sex ratios of the progenies reared at standard temperature suggest that the three populations share a similar complex GSD system based on a predominant male heterogametic factor with additional influences of polymorphism at this locus and/or action of minor factors. The three populations presented a clear thermosensitivity of sex differentiation, with large variations in the intensity of response depending on the parents. This confirms the presence of genotype-environment interactions in TSD of Nile tilapia. Furthermore the existence of naturally sex-reversed individuals is strongly suggested in two populations (Kpandu and Koka). However, it was not possible here to infer if the sex-inversion resulted from minor genetic factors and/or environmental influences. The present study demonstrated for the first time the conservation of a complex SDS combining polymorphic GSD and TSD components in natural populations of Nile tilapia. We discuss the evolutionary implications of our findings and highlight the importance of field investigations of sex determination. (c) 2007 Elsevier B.V. All rights reserved.

Is perioperative point-of-care prothrombin time testing accurate compared to the standard laboratory test?

There is no accepted way of measuring prothrombin time without time loss for patients undergoing major surgery who are at risk of intraoperative dilution and consumption coagulopathy due to bleeding and volume replacement with crystalloids or colloids. Decisions to transfuse fresh frozen plasma and procoagulatory drugs have to rely on clinical judgment in these situations. Point-of-care devices are considerably faster than the standard laboratory methods. In this study we assessed the accuracy of a Point-of-care (PoC) device measuring prothrombin time compared to the standard laboratory method. Patients undergoing major surgery and intensive care unit patients were included. PoC prothrombin time was measured by CoaguChek XS Plus (Roche Diagnostics, Switzerland). PoC and reference tests were performed independently and interpreted under blinded conditions. Using a cut-off prothrombin time of 50%, we calculated diagnostic accuracy measures, plotted a receiver operating characteristic (ROC) curve and tested for equivalence between the two methods. PoC sensitivity and specificity were 95% (95% CI 77%, 100%) and 95% (95% CI 91%, 98%) respectively. The negative likelihood ratio was 0.05 (95% CI 0.01, 0.32). The positive likelihood ratio was 19.57 (95% CI 10.62, 36.06). The area under the ROC curve was 0.988. Equivalence between the two methods was confirmed. CoaguChek XS Plus is a rapid and highly accurate test compared with the reference test. These findings suggest that PoC testing will be useful for monitoring intraoperative prothrombin time when coagulopathy is suspected. It could lead to a more rational use of expensive and limited blood bank resources.

Effects of Pasture Conditions in Spring on Seasonal Forage Productivity

Fifteen beef cow-calf producers in southern Iowa were selected based on locality, management level, historical date of grazing initiation and desire to participate in the project. In 1997 and 1998, all producers kept records of production and economic data using the Integrated Resource Management-Standardized Performance Analysis (IRM-SPA) records program. At the initiation of grazing on each farm in 1997 and 1998, Julian date, degree-days, cumulative precipitation, and soil moisture, phosphorus, and potassium concentrations were determined. Also determined were pH, temperature, and load-bearing capacity; and forage mass, sward height, morphology and dry matter concentration. Over the grazing season, forage production, measured both by cumulative mass and sward height, forage in vitro digestible dry matter concentration, and crude protein concentration were determined monthly. In the fall of 1996 the primary species in pastures on farms used in this project were cool-season grasses, which composed 76% of the live forage whereas legumes and weeds composed 8.3 and 15.3%, respectively. The average number of paddocks was 4.1, reflecting a low intensity rotational stocking system on most farms. The average dates of grazing initiation were May 5 and April 29 in 1997 and 1998, respectively, with standard deviations of 14.8 and 14.1 days. Because the average soil moisture of 23% was dry and did not differ between years, it seems that most producers delayed the initiation of grazing to avoid muddy conditions by initiating grazing at a nearly equal soil moisture. However, Julian date, degree-days, soil temperature and morphology index at grazing initiation were negatively related to seasonal forage production, measured as mass or sward height, in 1998. And forage mass and height at grazing initiation were negatively related to seasonal forage production, measured as sward height, in 1997. Moreover, the concentrations of digestible dry matter at the initiation of and during the grazing season and the concentrations of crude protein during the grazing season were lower than desired for optimal animal performance. Because the mean seasonal digestible dry matter concentration was negatively related to initial forage mass in 1997 and mean seasonal crude proteins concentrations were negatively related to the Julian date, degree-days, and morphology indeces in both years, it seems that delaying the initiation of grazing until pasture soils are not muddy, is limiting the quality as well as the quantity of pasture forage. In 1997, forage production and digestibility were positively related to the soil phosphorus concentration. Soil potassium concentration was positively related to forage digestibility in 1997 and forage production and crude protein concentration in 1998. Increasing the number of paddocks increased forage production, measured as sward height, in 1997, and forage digestible dry matter concentration in 1998. Increasing yields or the concentrations of digestible dry matter or crude protein of pasture forage reduced the costs of purchased feed per cow.

Classes of multichannel EEG microstates in light and deep hypnotic conditions

The study assessed the brain electric mechanisms of light and deep hypnotic conditions in the framework of EEG temporal microstates. Multichannel EEG of healthy volunteers during initial resting, light hypnosis, deep hypnosis, and eventual recovery was analyzed into temporal EEG microstates of four classes. Microstates are defined by the spatial configuration of their potential distribution maps ([Symbol: see text]potential landscapes') on the head surface. Because different potential landscapes must have been generated by different active neural assemblies, it is reasonable to assume that they also incorporate different brain functions. The observed four microstate classes were very similar to the four standard microstate classes A, B, C, D [Koenig, T. et al. Neuroimage, 2002;16: 41-8] and were labeled correspondingly. We expected a progression of microstate characteristics from initial resting to light to deep hypnosis. But, all three microstate parameters (duration, occurrence/second and %time coverage) yielded values for initial resting and final recovery that were between those of the two hypnotic conditions of light and deep hypnosis. Microstates of the classes B and D showed decreased duration, occurrence/second and %time coverage in deep hypnosis compared to light hypnosis; this was contrary to microstates of classes A and C which showed increased values of all three parameters. Reviewing the available information about microstates in other conditions, the changes from resting to light hypnosis in certain respects are reminiscent of changes to meditation states, and changes to deep hypnosis of those in schizophrenic states.

Impact of Different Illumination Conditions on Visual Caries Detection with ICDAS

The aim of this study was to test the influence of different degrees of additional illumination on visual caries detection using the International Caries Detection and Assessment System (ICDAS). Two calibrated examiners assessed 139 occlusal surfaces of extracted permanent molars using a standard operation lamp with or without an additional headlamp providing three default brightness intensities. Histology served as the gold standard. Pooled data showed no differences in sensitivities. Specificities were not influenced by additional light. The area under the curve for the Marthaler classification D3 threshold was significantly lower when an additional strong headlamp was used (0.59 compared to 0.69-0.72 when reduced illumination intensities were used). One of the two examiners also had a significantly lower sensitivity for the D1 threshold when an additional headlamp was used. The use of additional white light led to a reduced detection of dentine lesions.

Seawater carbonate chemistry, chlorophyll a and photosynthetic carbon fixation rate under different light and pCO2 conditions during experiments, 2010

We carried out short term pCO2/pH perturbation experiments in the coastal waters of the South China Sea to evaluate the combined effects of seawater acidification (low pH/high pCO2) and solar UV radiation (UVR, 280-400 nm) on photosynthetic carbon fixation of phytoplankton assemblages. Under photosynthetically active radiation (PAR) alone treatments, reduced pCO2 (190 ppmv) with increased pH resulted in a significant decrease in the photosynthetic carbon fixation rate (about 23%), while enriched pCO2 (700 ppmv) with lowered pH had no significant effect on the photosynthetic performance compared to the ambient level. The apparent photosynthetic efficiency decreased under the reduced pCO2 level, probably due to C-limitation as well as energy being diverged for up-regulation of carbon concentrating mechanisms (CCMs). In the presence of UVR, both UV-A and UV-B caused photosynthetic inhibition, though UV-A appeared to enhance the photosynthetic efficiency under lower PAR levels. UV-B caused less inhibition of photosynthesis under the reduced pCO2 level, probably because of its contribution to the inorganic carbon (Ci)-acquisition processes. Under the seawater acidification conditions (enriched pCO2), both UV-A and UV-B reduced the photosynthetic carbon fixation to higher extents compared to the ambient pCO2 conditions. We conclude that solar UV and seawater acidification could synergistically inhibit photosynthesis.

Biotic and abiotic parameters and cynobacteria abundance during an experimental set-up with varying pCO2 conditions

Heterocystous cyanobacteria of the genus Nodularia form extensive blooms in the Baltic Sea and contribute substantially to the total annual primary production. Moreover, they dispense a large fraction of new nitrogen to the ecosystem when inorganic nitrogen concentration in summer is low. Thus, it is of ecological importance to know how Nodularia will react to future environmental changes, in particular to increasing carbon dioxide (CO2) concentrations and what consequences there might arise for cycling of organic matter in the Baltic Sea. Here, we determined carbon (C) and dinitrogen (N2) fixation rates, growth, elemental stoichiometry of particulate organic matter and nitrogen turnover in batch cultures of the heterocystous cyanobacterium Nodularia spumigena under low (median 315 µatm), mid (median 353 µatm), and high (median 548 µatm) CO2 concentrations. Our results demonstrate an overall stimulating effect of rising pCO2 on C and N2 fixation, as well as on cell growth. An increase in pCO2 during incubation days 0 to 9 resulted in an elevation in growth rate by 84 ± 38% (low vs. high pCO2) and 40 ± 25% (mid vs. high pCO2), as well as in N2 fixation by 93 ± 35% and 38 ± 1%, respectively. C uptake rates showed high standard deviations within treatments and in between sampling days. Nevertheless, C fixation in the high pCO2 treatment was elevated compared to the other two treatments by 97% (high vs. low) and 44% (high vs. mid) at day 0 and day 3, but this effect diminished afterwards. Additionally, elevation in carbon to nitrogen and nitrogen to phosphorus ratios of the particulate biomass formed (POC : POP and PON : POP) was observed at high pCO2. Our findings suggest that rising pCO2 stimulates the growth of heterocystous diazotrophic cyanobacteria, in a similar way as reported for the non-heterocystous diazotroph Trichodesmium. Implications for biogeochemical cycling and food web dynamics, as well as ecological and socio-economical aspects in the Baltic Sea are discussed.