Successful embryo transfer in Tianzhu white yak using standard protocol

The present study was carried out to investigate the efficiency of superovulation, oestrus synchroni-zation, and embryo recovery in Tianzhu white yaks and also to confirm the pregnancy rate of black yaks, to which embryos collected from white yaks were transplanted. Forty-seven yaks were selected from different experiment groups, including 10 Tianzhu white female yaks (donor, group A) and 37 black female yaks (recipient, groups B and C). Superovulation of the donor was induced by the application procedure of CIDR-B FSH PG. Oestrus synchronization of recipients was induced using two meth-ods: group B was given the same treatment as group A, except that the follicle-stimulating hormone (FSH) injection was not administered, whereas group C was injected with cloprostenol only once when corpus luteum (corpora lutea) was (were) palpated. The results showed that the oestrous rates in group A were higher (80%) than those in group B (60%) and group C (44.5%). As for the efficiency of su-perovulation, it was indicated that the mean numbers (±SD) of total corpora lutea, follicles, viable (transferable), and degenerated embryos were 4.75 ± 2.19, 1.13 ± 0.83, 2.50 ± 1.31, and 1.38 ± 0.92, re-spectively. The mean embryo recovery rates were 55.6%. All together, 18 viable embryos of Tianzhu white yak were obtained and 12 of them were transplanted to 10 recipients. The pregnancy rate was 50% and the delivery rate was 40%.     

The responses to illusory contours of neurons in cortex areas 17 and 18 of the cats

Responses to illusory contours (ICs) were sampled from neurons in cortical areas 17 and 18 of the anesthetized cats. For ICs sensitive cells, the differences of receptive field properties were compared when ICs and real contour stimuli were applied. Two hundred orientation or direction selective cells were studied. We find that about 42 percent of these cells were the ICs sensitive cells. Although their orientation or direction tuning curves to ICs bar and real bars were similar, the response modes (especially latency and time course) were different. The cells' responses to ICs were independent of the spatial phases of sinusoidal gratings, which composed the ICs. The cells' optimal spatial frequency to composing gratings the ICs was much higher than the one to moving gratings. Therefore, these cells really responded to the ICs rather than the line ends of composing gratings. For some kinds of velocity-tuning cells, the optimal velocity to moving ICs bar was much lower than the optimal velocity to moving     

Sublethal effects of imidacloprid and pymetrozine on population growth parameters of cabbage aphid, Brevicoryne brassicae on rapeseed, Brassica napus L.

Efficiency of imidacloprid and pymetrozine on population growth parameters of cabbage aphid, Brevicoryne brassicae L. （Homoptera： Aphididae） was determined using demographic toxicology by leaf dip method. At first, bioassay tests were performed. The LC50 value and confidence limit for imidacloprid and pymetrozine were 1.61 × 10^-5 mol/L （0.74 × 10^-5-2.66 × 10^-5） and 2.14 × 10^-4 mol/L （1.24 × 10^-4-3.40 × 10^-4）, respectively. To evaluate the sublethal effect of two insecticides on population growth parameters of cabbage aphid, LC30 concentrations of imidacloprid and pymetrozine were used at 5 mol/L and 30 mol/L. The experiments were carried out in a incubator at 20±1℃, 60% ± 5% RH and 16：8 （L：D） photoperiod on canola seedlings, Brassica napus L. var. ＇PF＇. Net fecundity rate decreased in both insecticide-treated populations. Intrinsic rates of increase （rm） were lower in imidacloprid and pymetrozine treatments than in controls. Intrinsic birth rates also decreased in treated populations. There was a relative increase in intrinsic death rates of treated populations. The mean generation times and doubling time were also lower in populations treated with insecticides than in controls. There was a considerable reduction in the average numbers of nymphs reproduced per female as compared with the control. The average longevity of female adults in the control was significantly different from those treated with imidacloprid and pymetrozine. However, there was no significant differences in aphid life-table parameters between the two insecticide-treated populations （P 〉 0.01）.     

A new model of phycobilisome in Spirulina platensis

Phycobilisomes (PBS) were isolated from blue-green alga Spirulina platensis. Scanning tunneling microscope was used to investigate the three-dimensional structure of PBS deposited on freshly cleaved highly oriented py-rolytic graphite (HOPG) in ambient condition at room temperature. The results showed that the rods of PBS radiated from the core to different directions in the space other than arrayed in one plane, which was different from the typical hemi-discoidal model structure. The diameter of PBS was up to 70 nm, and the rod was approximately 50 nm in length. Similar results were observed in Langmuir-Blodgett (LB) film of PBS. The dissociated PBS could reaggregate into rod-like structures and easily form two-dimensional membrane while being absorbed on HOPG, however, no intact PBS was observed. The filling-space model structure of PBS in Spirulina platensis with STM from three-dimensional real space at nanometer scale was found, which showed that this new structural model of PBS surely exists in blue     

Quality-control method for the determination of biological activity of engineered calcineurin subunit B

The aim of this study was to establish a quality-control method for calcineurin subunit B(CNB) biological activity determinations. CNB enhances the p-nitrophenylphosphate(p NPP) dephosphorylating activity of calcineurin subunit A Δ316 mutant(CNAΔ316). A series of CNB concentrations were fitted to a four-parameter equation to calculate the corresponding p NPP maximum dephosphorylation rates. Values were calculated based on biological activity references using a parallel line method. The method was then validated for accuracy, precision, linearity, linear range, sensitivity, specificity, and robustness. The recovery results were greater than 98%. Intra-plate precision was 6.7%, with inter-plate precision of 10.8%. The coefficient of determination was greater than 0.98. The linear range was 0.05–50 μg m L?1, with sensitivity of 50 μg m L?1. Tested cytokines did not induce CNAΔ316 dephosphorylation of p NPP. The chosen CNAΔ316 concentration range did not affect activity determinations.     

Diversity and ecological distribution of endophytic fungi associated with medicinal plants

A total of 973 isolates of endophytic fungi were recovered from 1144 tissue fragments of the six me-dicinal plant species belonging to 4 families collected in the Beijing Botanical Garden. Of these isolates 778 sporulated and were identified into 21 taxa by morphological characteristics. Among the taxa 11 belonged to Coelomycetes, 6 to Ascomycetes, and 4 to Hyphomycetes. Various numbers of endophytic fungi (5―8 taxa) were obtained from each plant. Alternaria alternata was the dominant species in the 6 plants, and Microsphaeropsis conielloides was also dominant in Eucommia ulmoides. There were high colonization rates (47.9%―63.1%) and isolation rates (0.7―0.93) of endophytic fungi, and they were conspicuously higher in twigs than those in leaves in the 6 plants examined. The colonization and isolation rates of endophytic fungi increased with the twig age. The results based on the analyses of cluster and Sorenson's similarity coefficients indicated that some endophytic fungi showed a certain degree of host and tissue preference.     

Phosphate Availability Alters Lateral Root Anatomy and Root Architecture of Fraxinus mandshurica Rupr. Seedlings

Plants have evolved some mechanisms to maximize the efficiency of phosphorus acquisition. Changes in root architecture are one such mechanism. When Fraxinus mandshurica Rupr. seedlings were grown under conditions of low phosphorus availability, the length of cells in the meristem zone of the lateral roots was longer, but the length of cells in the elongation and mature zones of the lateral roots was shorter,compared with seedlings grown under conditions of high phosphorus availability. The elongation rates of primary roots increased as phosphorus availability increased, but the elongation rates of the branched zones of the primary roots decreased. The number of lateral root primordia and the length of the lateral roots decreased as phosphorus availability increased. The topological index (altitude slope) decreased as phosphorus availability increased, suggesting that root architecture tended to be herringbone-like when seedlings were grown under conditions of low phosphate availability. Herringbone-like root systems exploit nutrients more efficiently, but they have higher construction costs than root systems with a branching pattem.     

Soil Organic Matter Dynamics Along a Vertical Vegetation Gradient in the Gongga Mountain on the Tibetan Plateau

Our knowledge about soil organic matter (SOM) dynamics is limited although this is an important issue in the study of responses of ecosystems to global climate changes. Twelve sampling plots were set up every 200 m from 1 700 to 3 900 m along the vertical vegetation gradient along the east slope of Gongga Mountain. Samples were taken from all 12 plots for SOM content measurement, although only 5 of the 12 plots were subjected to radiocarbon measurements. A radiocarbon isotope method and a time-dependent model were used to quantify the SOM dynamics and SOM turnover rates along the vertical vegetation gradient. The results showed that the SOM turnover rate decreased and turnover time increased with soil depth for all vegetation types. The litter layer turnover rates presented a clear trend along the gradient. The litter layer turnover rates decreased with an increase in elevation, except that the litter layer turnover rate of mixed forest was higher than that of evergreen forest. Climatic factors, such as temperature and precipitation, were the main factors influencing the surface soil carbon dynamics. The turnover rates of the subsoil (including the A, B, and C horizons in the soil profiles) along the vertical gradient had no clear trends. The SOM of subalpine shrub and meadow turned over more slowly than that of the forest types in almost all soil horizons. The characteristic of short roots distributing in the upper part of the soil profile leads to different SOM dynamics of shrub and meadow compared with the forest types. Coniferous and mixed forests were susceptible to carbon loss from the young carbon pool, but their long and big roots resulted in high △^14C values of the deep soil profiles and increased the input of young carbon to the deep soil. In evergreen forest, the carbon cumulative ability from the B horizon to the C horizon was weak. The different vegetation types, together with their different modes of nutrient and carbon intake, may be the mechanism conditioning the subsoil organic matter dynamics.     

Experimental study of rat beta islet cells cultured under simulated microgravity conditions

To observe the effects of simulated microgravity on beta islet cell culture, we have compared the survival rates and the insulin levels of the isolated rat islet cells cultured at micro- and normal gravity conditions. The survival rates of the cells cultured were determined by acridine orange-propidium iodide double-staining on day 3, 7 and 14. The morphology of the cells was observed by electron microscopy. Insulin levels were measured by radio immuno assays. Our results show that the cell number cultured under the microgravity condition is significantly higher than that under the routine condition (P<0.01). Some tubular structure shown by transmission electron microscopy, possibly for the transport of nutrients, were formed intercellularly in the microgravity cultured group on day 7. There were also abundant secretion particles and mitochondria in the cytoplasm of the cells. Scanning electron microscopy showed that there were holes formed between each islet, possibly connecting with the nutrient trans     

Effects of irradiance and phosphate on growth of nanophytoplankton and picophytoplankton

In situ incubation experiments were conducted to investigate the phosphate uptake and the growth variations of nano- and picophytoplankton under controlled phosphorus concentrations and irradiances in Changjiang estuary and its adjacent sea in China. The results showed that the rates of phosphate uptake were accelerated at high levels (0.60 μmol/L) under the condition of 100% natural irradiance, and the cell densities of nanophytoplankton and Synechococcus spp. obviously increased, whereas picoeukaryote was adapted to low phosphate levels (0.25 μmol/L). Under low irradiance (50% of natural irradiance), uptake of phosphate was restrained at high levels, and the growth of both nanophytoplankton and Synechococcus spp. was also limited. Morerover, nanophytoplankton and Synechococcus spp. grew well at intermediate phosphate levels (0.41 μmol/L), whereas picoeukaryote grew well at low phosphate levels. In addition, the growth period of phytoplankton at intermediate phosphate levels was obviously prolonged, suggesting that the limitation of phytoplankton growth mainly reflected the changes during its growth period. In the absence of irradiance, the addition of phosphate did not affect the release rates of phosphate with a linear increase in the phytoplankton, whereas the growth rates of the phytoplankton showed an exponential decrease, which showed that phosphate regeneration was faster during day than during night; therefore, the irradiance was a significant factor that affected phosphorous biogeochemical cycle in the Changjiang estuary in China.     

Sex ratio,survival, and recapture rate in a Cuban population of the damselfly <Emphasis Type="BoldItalic">Hypolestes trinitatis</Emphasis> (Odonata: Megapodagrionidae)

Male-biased sex ratios in adult odonate populations have been the subject of vigorous discussion between the students of this order of insects. The debate has centered on whether the observed male bias in many populations is real, perhaps due to unequal survival rates, or whether it is an artifact caused by differences in recapture probabilities. A mark–recapture study to assess the relative contribution of survivorship and recapture rates on male-biased sex ratio was performed in a Cuban population of the damselfly Hypolestes trinitatis. Maximum likelihood theory and Akaike information criterion were used for parameter estimation and model selection, respectively. Females in the sample were outnumbered two to one by males. Estimated recapture and survival rates were 0.188 (females) and 0.638 (males), and 0.933 (females) and 0.944 (males), respectively. Recapture rates only partially explained the bias since the population sex ratio estimated after correcting for differences in this parameter was male biased (1.5). The observed higher survival probabilities in males could have generated the male-biased population sex ratio. Therefore, we concluded that the observed male-biased population sex ratio in H. trinitatis is real.     

Computer simulation of energy migration in the C-phycocyanin of the blue-green algae Agmenellum Quadruplicatum

Two methods for simulation of energy migration in the C-phycocyanin fragments of PBS were developed. Both methods are based on the statistical analysis of an excitation behavior in modeling complexes with a limited number (up to hundreds) of chromophores using the Monte-Carlo approach and calculation of migration rates for the system of linear balance equations. Energy migration rates were calculated in the case of C-phycocyanin of the blue-green algae Agmenellum quadruplicatum. The main channels of energy migration were determined in a monomer, trimer, hexamer, and in the rods consisting of 2-4 hexamers. The influence of the “screw” angle between two adjoining trimers of hexamer on the rates of energy migration and on its efficiencies in 1-4 hexamers was also estimated. The analysis was made for the average (random) and real orientation of chromophores in the C-phycocyanin. For both cases the optimal angle values were determined and the one for real C-phycocyanin structure was found to be very close (Δø ≤ 5°) to the optimal angle calculated.     

Reconstructing shifts in vital rates driven by long‐term environmental change: a new demographic method based on readily available data

Frequently, vital rates are driven by directional, long‐term environmental changes. Many of these are of great importance, such as land degradation, climate change, and succession. Traditional demographic methods assume a constant or stationary environment, and thus are inappropriate to analyze populations subject to these changes. They also require repeat surveys of the individuals as change unfolds. Methods for reconstructing such lengthy processes are needed. We present a model that, based on a time series of population size structures and densities, reconstructs the impact of directional environmental changes on vital rates. The model uses integral projection models and maximum likelihood to identify the rates that best reconstructs the time series. The procedure was validated with artificial and real data. The former involved simulated species with widely different demographic behaviors. The latter used a chronosequence of populations of an endangered cactus subject to increasing anthropogenic disturbance. In our simulations, the vital rates and their change were always reconstructed accurately. Nevertheless, the model frequently produced alternative results. The use of coarse knowledge of the species' biology (whether vital rates increase or decrease with size or their plausible values) allowed the correct rates to be identified with a 90% success rate. With real data, the model correctly reconstructed the effects of disturbance on vital rates. These effects were previously known from two populations for which demographic data were available. Our procedure seems robust, as the data violated several of the model's assumptions. Thus, time series of size structures and densities contain the necessary information to reconstruct changing vital rates. However, additional biological knowledge may be required to provide reliable results. Because time series of size structures and densities are available for many species or can be rapidly generated, our model can contribute to understand populations that face highly pressing environmental problems.     

A new model of carbon and phosphorus transfers in arbuscular mycorrhizas

Existing models of nutrient transfer in arbuscular mycorrhizal (AM) symbioses are inadequate as they do not explain the range of real responses seen experimentally. A computer simulation model was used to evaluate the novel hypotheses that mycorrhizal nutrient transfers were based solely on symbionts' internal needs, and that carbon and phosphorus transfers were quantitatively unlinked. To be plausible, simulated mycorrhizal plants would show a +/-50% variation in weight vs nonmycorrhizal controls, with a normal response distribution (mimicking a real data set). One plant and one arbuscular mycorrhizal fungus (AMF) growing in a soil volume were simulated, using C, P and nitrogen nutrient cycling and stoichiometry. C- and P-exchange rates were independent and could be varied at will. The model was tested at realistic nutrient concentrations and a full range of nutrient exchange rates. The model showed -20% to +55% range in mycorrhizal plant weight distributed close to normal, suggesting that the hypotheses were plausible. The model suggests that theoretical assumptions about mycorrhizas should be reassessed. The model worked only because the symbionts possessed incomplete information on their partner and environmental conditions. Conventional cost-benefit models do not work under these circumstances, but both mutualistic and parasitic interactions were successfully simulated.     

Sodium dodecyl sulphate dependent NADPH oxidation: an alternative method for assaying NADPH-oxidase in a cell-free system

In assaying NADPH-oxidase activities using macrophage-derived cell-free systems, sodium dodecyl sulphate dependent NADPH oxidation rates were found to correlate strongly with superoxide-dismutase inhibitable cytochrome-c reduction rates. Optimum sodium dodecyl sulphate concentration was in the range 95-110 microM. A theoretical function for the activation and deactivation of NADPH-oxidase by sodium dodecyl sulphate is suggested. This function may serve to estimate the real Vmax of the enzyme and the number of detergent molecules required for the full activation of the enzymatic complex.     

Associations between the rates of maturation and growth in the short bones of the hand

Serial radiographs of the hand-wrist were used to analyze the associations within bones between the rates of change in skeletal maturity, diaphyseal and epiphyseal lengths and diaphyseal width. In previous studies of these children, it has been shown that these rates are linear in relation to chronological age. The associations between the rates of change in these parameters were analyzed using the slopes (b values) for regression lines flitted to the data in each child. In individual bones, most of the correlation coefficients were moderate to low; some were negative. For most associations in each sex they were relatively high for metacarpal II. The rates of skeletal maturation and diaphyseal elongation were correlated more highly in the girls than in the boys but the rates of skeletal maturation and epiphyseal elongation were correlated more highly in the boys. When bones were considered in groups, relatively high correlations were noted for the metacarpals and ray II, lower correlations were common for the middle and distal phalanges. There was no evidence of real neighborhood effects but marginal effects were present.     

Odour emissions from anaerobic piggery ponds. 2: improving estimates of emission rate through recognition of spatial variability

Odour emission rates were measured for seven different anaerobic ponds treating piggery wastes at six to nine discrete locations across the surface of each pond on each sampling occasion over a thirteen month period. Significant variability in emission rates were observed for each pond. Measurement of a number of water quality variables in pond liquor samples collected at the same time and from the same locations as the odour samples indicated that the composition of the pond liquor was also variable. The results indicated that spatial variability was a real phenomenon and could have a significant impact on odour assessment practices. Considerably more odour samples would be required to characterise pond emissions than currently recommended by most practitioners, or regulatory agencies.     

Effect of camera monitoring on survival rates of High-Arctic shorebird nests

ABSTRACT.   Monitoring bird nests with cameras provides an opportunity to identify the cause of nest failure and record the behavior of individuals. However, leaving an object continuously within sight of a nest could have potential negative effects on nesting success. We compared daily survival rates of nests monitored using cameras and human visitation to nests tracked via human visitation only to test for potential additional effects of camera monitoring on predation rates. From 2006 to 2008, experiments were conducted on Bylot Island (Nunavut) using 80 artificial nests and 53 real nests of Baird's Sandpipers ( Calidris bairdii ) and White-rumped Sandpipers ( Calidris fuscicollis ). Rates of predation on real and artificial nests varied considerably among years. However, survival rates of camera-monitored nests did not differ from those of nests monitored without cameras. Predators of artificial nests included Arctic foxes ( Vulpes lagopus ), Glaucous Gulls ( Larus hyperboreus ), and Long-tailed Jaegers ( Stercorarius longicaudus ), whereas Arctic foxes were responsible for all camera-recorded predation events at real nests. Camera monitoring should be promoted as a viable method for monitoring nests of Arctic shorebirds because our results indicate that placing cameras at nests does not bias estimates of nest survival obtained via nest visits.     

The evaluation of initial rates in the presence of background noise.

A three-parameter model was used to test a curvilinear regression for its gamma-intercept. It was applied in the kinetic analysis of a model reaction and of real experiments. The model reaction consisted of a dialysis experiment with increasing amounts of background added at t0. In the presence of this background, initial rates of solute exchange were determined precisely enough to be in agreement with Fick's law of diffusion. The biological experiments were concerned with the saturation kinetics of the acid-soluble radioactivity of cells exposed to 3H-labelled amino acids. Two models of regression were applied, facilitated and physical diffusion, both consistent with the assumption of a substantial amount of background. This background was assumed to be caused by adsorption of 3H-labelled amino acids to cell-surface proteins. Without further consideration it caused a systematic overestimation of the initial rates.