bluuebunny/crossref_metadata_2025 huggingface dataset:
Io: Charting thermal emission variability with the Galileo NIMS Io Thermal Emission Database (NITED): Loki Patera
Authors: Davies A. G. , Veeder G. J. , Matson D. L. , Johnson T. V.
Published: December 2011

We have calculated the ≈5‐μm radiant flux for every volcanic hot spot in every one of the 190 GalileoNear‐Infrared Mapping Spectrometer (NIMS) tube observations of Io obtained between 28 June 1996 and 16 October 2001 in order to determine the variability of thermal emission from Io's volcanoes at local, regional and global scales, and to identify individual eruption episodes where thermal emission waxes and wanes. The resulting NIMS Io Thermal Emission Database (NITED) allows the comparison of activity at individual volcanoes and different regions of Io. The database contains over 1000 measurements of radiant flux at approximately 5μm, corrected for emission angle, range to target and incident sunlight (where necessary). We examine the data for Loki Patera, Io's most powerful volcano. For data acquired in local darkness we use two‐temperature fits to nighttime spectra and prior knowledge of emitting area to determine total radiated thermal emission. For other data we use the constancy of the integrated thermal emission spectrum to determine total thermal emission from measurements of radiant flux at 5μm. As seen by NIMS, total thermal emission from Loki Patera varies between 7600 GW and 17000 GW. We revise upwards previous estimates of thermal emission from NIMS data. NIMS 3.5‐μm radiant fluxes (both measured and estimated) are consistent with measurements from ground‐based telescopes. This work highlights the value of NITED as a research tool.
Using short‐term postseismic displacements to infer the ambient deformation conditions of the upper mantle
Authors: Freed Andrew M. , Hirth Greg , Behn Mark D.
Published: December 2011

To interpret short‐term postseismic surface displacements in the context of key ambient conditions (e.g., temperature, pressure, background strain rate, water content, creep mechanism), we combined steady state and transient flow into a single constitutive relation that can explain the response of a viscoelastic material to a change in stress. The flow law is then used to investigate mantle deformation beneath the Eastern California Shear Zone following the 1999 M7.1 Hector Mine earthquake. The flow law parameters are determined using finite element models of relaxation processes, constrained by surface displacement time series recorded by 55 continuous GPS stations for 7 years following the earthquake. Results suggest that postseismic flow following the Hector Mine earthquake occurs below a depth of ∼50 km and is controlled by dislocation creep of wet olivine. Diffusion creep models can also explain the data, but require a grain size (3.5 mm) that is smaller than the inferred grain size (10–20 mm) based on the mantle conditions at these depths. In addition, laboratory flow laws predict dislocation creep would dominate at the stress/grain size conditions that provide the best fit to diffusion creep models. Model results suggest a transient creep phase that lasts ∼1 year and has a viscosity ∼10 times lower than subsequent steady state flow, in general agreement with laboratory observations. The postseismic response is best explained as occurring within a relatively hot upper mantle (e.g., 1200–1300°C at 50 km depth) with a long‐term background mantle strain rate of 0.1–0.2μstrain/yr, consistent with the observed surface strain rate. Long‐term background shear stresses at the top of the mantle are ∼4 MPa, then decrease with depth to a minimum of 0.1–0.2 MPa at 70 km depth before increasing slowly with depth due to the pressure dependence of viscosity. These conditions correspond to a background viscosity of 1021 Pa s within a thin mantle lid that decreases to ∼5 × 1019 Pa s within the underlying asthenosphere. This study shows the utility of using short‐term postseismic observations to infer long‐term mantle conditions that are not readily observable by other means.
Modeling the anisotropic brine microstructure in first‐year Arctic sea ice
Authors: Jones K. A. , Ingham M. , Eicken H.
Published: December 2011

Cross‐borehole DC resistivity tomography has recently been used to monitor the temporal variation of the anisotropic bulk electrical resistivity of first‐year Arctic sea ice during the period of spring warming. These measurements cannot be explained by standard models of sea ice microstructure which treat the brine phase as isolated ellipsoidal pores. A simple structural model which does satisfy the observed electrical data shows that the brine phase must be connected both vertically and horizontally. Calculation of the temporal and thermal evolution of the microstructure suggests that although vertical connectivity is through pore tubes and sheets with widths of ∼100 μm, horizontal connectivity is through much thinner connections which are interpreted as inter‐ and intragranular brine layers. As the temperature increases the width of vertical channels increases smoothly. In contrast, at temperatures above about −2°C there is a rapid increase in the thickness of horizontal connections which we interpret as a change from conduction through intergranular brine layers to the development of horizontal pores. The electrical data also broadly exhibit a percolation transition predicted by mathematical models. However, the critical brine volume fraction for vertical electrical connection is very small, while that for horizontal electrical connection is derived to be about 0.5%. The difference between these and the critical threshold of 5% for fluid permeability is presumed to arise because of the strong dependence of the latter on brine channel width.
Two approaches to modeling the initiation and development of rills in a man‐made catchment
Authors: Hofer Markus , Lehmann Peter , Stähli Manfred , Seifert Stefan , Krafczyk Manfred
Published: December 2011

Surface erosion rills are dominant structures in young developing ecosystems, and as such they fundamentally affect water flows, for example by channeling surface runoff or by locally changing the infiltration capacity of the soil. To successfully model the systems hydrology it is indispensable to take the development of erosion rills into account. The goal of this study was to model the emergence of an erosion rill network with total length of 6 km formed during the last few years in the 6 ha large artificial catchment Chicken Creek near Cottbus (Germany). The length and connectivity of the evolving network were quantified from aerial images. This analysis showed that the major rill network established already during the first year of ecosystem development. We adapted two model approaches to simulate the emergence of erosion rills. First, we used a self‐organized critical network approach with soil erosion and sediment deposition governed by a local critical shear stress. The second approach, based on Manning's equation, was developed to compare the results of the self‐organized critical network approach with results from a simple but more physically based approach. Erosion was triggered in the case of high local shear stress and deposition was calculated from settling velocity of the suspended particles. Both models were able to reproduce the observed rill network. Geometric characteristics such as network length and rill depth were simulated in the right order of magnitude. The models also managed to describe the position and temporal evolution of the main erosion rills in the catchment.
Effects of acutely inhibiting PI3K isoforms and mTOR on regulation of glucose metabolism in vivo
Authors: Smith Greg C. , Ong Wee Kiat , Rewcastle Gordon W. , Kendall Jackie D. , Han Weiping , Shepherd Peter R.
Published: December 2011

In in vitro studies class-I PI3Ks (phosphoinositide 3-kinases), class-II PI3Ks and mTOR (mammalian target of rapamycin) have all been described as having roles in the regulation of glucose metabolism. The relative role each plays in the normal signalling processes regulating glucose metabolism in vivo is less clear. Knockout and knockin mouse models have provided some evidence that the class-I PI3K isoforms p110α, p110β, and to a lesser extent p110γ, are necessary for processes regulating glucose metabolism and appetite. However, in these models the PI3K activity is chronically reduced. Therefore we analysed the effects of acutely inhibiting PI3K isoforms alone, or PI3K and mTOR, on glucose metabolism and food intake. In the present study impairments in glucose tolerance, insulin tolerance and increased hepatic glucose output were observed in mice treated with the pan-PI3K/mTOR inhibitors PI-103 and NVP-BEZ235. The finding that ZSTK474 has similar effects indicates that these effects are due to inhibition of PI3K rather than mTOR. The p110α-selective inhibitors PIK75 and A66 also induced these phenotypes, but inhibitors of p110β, p110δ or p110γ induced only minor effects. These drugs caused no significant effects on BMR (basal metabolic rate), O2 consumption or water intake, but BEZ235, PI-103 and PIK75 did cause a small reduction in food consumption. Surprisingly, pan-PI3K inhibitors or p110α inhibitors caused reductions in animal movement, although the cause of this is not clear. Taken together these studies provide pharmacological evidence to support a pre-eminent role for the p110α isoform of PI3K in pathways acutely regulating glucose metabolism.
Structure, electrical and magnetic property investigations on dense Fe-doped hexagonal BaTiO3
Authors: Wei X. K. , Su Y. T. , Sui Y. , Zhang Q. H. , Yao Y. , Jin C. Q. , Yu R. C.
Published: December 2011

Hexagonal Ba(Ti1−xFex)O3−δ (x = 1/6, 1/3) ceramics treated with post annealing are specifically synthesized to explore the origin mechanism of the unusual ferromagnetism in the doped system. X-ray diffraction refinements and transmission electron microscope experiments reveal that their structures are incommensurately modulated owing to simultaneous oxygen vacancies at both O1 and O2 sites. Consequently, coexisting weak ferrielectricity and weak ferromagnetism are presented at room temperature. Analysis on their leakage current plot reveals that their conduction follows trap-filled limit model. In combination with the magnetism studies on 5 mol% Fe-doped crystals [Phys. Rev. B 83, 144407 (2011)], the reduction of ferromagnetism with an increase of conductivity suggests that dynamic exchanges of trapped electrons among the bound magnetic polarons attribute to the intrinsic ferromagnetism.
Hole spectra and conductance for quantum wire systems under Rashba spin-orbit interaction
Authors: Cuan R. , Diago-Cisneros L.
Published: December 2011

Focusing a problem with Rashba spin-orbit interaction (SOI-R), we propose an approach derived from standard multiband Hamiltonians that incorporate several hole band mixing effects. The influence of the SOI-R is shown on both the band structure and the zero-temperature conductance of a quasi-one-dimensional hole system patterned in a two-dimensional hole gas by a repulsive bias. The SOI-R leads the hole spectrum to split, as expected. However, we found appealing additional sub-band extremes only for heavy holes’ unfolded sub-bands. The heavy-hole energy splitting exhibits a strong dependency on the wave vector component kz along the wire as well as on the effective Rashba parameter that clearly departs from the two-dimensional (2D) case. Nevertheless, for some low interval of kz, the standard 2D feature is preserved and the splitting naturally follows a cubic proportionality. The two-probe Landauer ladder-steps quantization conductance shifts down to lower Fermi energies for nonzero SOI-R. The existence of heavy hole subband multiple minima lead to additional propagating modes and, thus, anomalous peaks for the ballistic conductance arise at variance with the opposite for light holes. The robustness of the anomalous features in the ballistic conductance can be tuned by manipulating the effective Rashba parameter and the hole-nanowire width, leading to destroy them as well.
Analytical model of the thin-film silicon-on-insulator tunneling field effect transistor
Authors: Dobrovolsky V. , Sizov F.
Published: December 2011

An analytical model of the thin-film silicon-on-insulator tunneling field effect transistor (TFET) is developed. It takes into account the quantum-dimensional effects in Si-film and a tunneling probability change along the transistor p-n +  junction. The gate controls the tunneling current, therefore changing the tunneling probability and energy window, where electron tunneling takes place. If the device base is non-degenerated, the window size strongly depends on the gate voltage. This causes appearance of the gate voltage area with the drain current abrupt change, extreme low swing, and high transconductance. The model represented can be applied for single-gate and double-gate TFETs.
Interlayer molecular diffusion and thermodynamic equilibrium in organic heterostructures on a metal electrode
Authors: Amsalem P. , Wilke A. , Frisch J. , Niederhausen J. , Vollmer A. , Rieger R. , Müllen K. , Rabe J. P. , Koch N.
Published: December 2011

In this paper, we investigate by photoemission the electronic properties of an organic/organic interface consisting in a strong electron acceptor hexaazatriphenylene-hexacarbonitrile (HATCN) deposited on a physisorbed N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (α-NPD) monolayer on Ag(111). At the first HATCN deposition steps (∼1 monolayer), the sample work function increases by 1.05 eV and the hole injection barrier (HIB) in the pre-adsorbed α-NPD monolayer is lowered by 0.65 eV. This results from HATCN diffusion to the silver surface through the α-NPD monolayer. Furthermore, this HATCN monolayer is proposed to form a compact chemisorbed monolayer, with a different structural arrangement than that observed on pristine Ag(111). In a second step, the additional deposited HATCN start growing on top of the α-NPD layer, and Fermi-level pinning, associated with the formation of HATCN negative polarons, is identified at the HATCN/α-NPD interface. Finally, HATCN is deposited on a α-NPD multilayer film. In this case, HATCN is also found to diffuse to the silver surface giving a similar HIB value in the α-NPD multilayer. This work demonstrates the importance of studying in detail the formation of organic heterostructures to understand the interplay between growth mode and electronic properties.
AC conductance measurement and analysis of the conduction processes in HfOx based resistive switching memory
Authors: Yu Shimeng , Jeyasingh Rakesh , Wu Yi , Philip Wong H.-S.
Published: December 2011

Impedance spectroscopy and AC conductance measurement were performed on HfOx based resistive switching memory. The fβ-like AC conductance is observable above a corner frequency for high resistance state (HRS). The index β is about 2 and is independent of DC bias or resistance value of different HRSs, suggesting that electron hopping between the nearest neighbor traps within the conductive filaments (CFs) is responsible for the measured AC conductance. The corner frequency shows up in a lower frequency regime for a higher HRS, indicating that a larger tunneling gap is formed between the electrode and the residual CFs.
Specific quantum mechanical/molecular mechanical capping-potentials for biomolecular functional groups
Authors: Ihrig Arvid Conrad , Schiffmann Christoph , Sebastiani Daniel
Published: December 2011

We present a series of capping-potentials designed as link atoms to saturate dangling bonds at the quantum/classical interface within density functional theory-based hybrid QM/MM calculations. We aim at imitating the properties of different carbon-carbon bonds by means of monovalent analytic pseudopotentials. These effective potentials are optimized such that the perturbations of the quantum electronic density are minimized. This optimization is based on a stochastic scheme, which helps to avoid local minima trapping. For a series of common biomolecular groups, we find capping-potentials that outperform the more common hydrogen-capping in view of structural and spectroscopic properties. To demonstrate the transferability to complex systems, we also benchmark our potentials with a hydrogen-bonded dimer, yielding systematic improvements in structural and spectroscopic parameters.
Suppression of vacancy defects in epitaxial La-doped SrTiO3 films
Authors: Keeble D. J. , Jalan B. , Ravelli L. , Egger W. , Kanda G. , Stemmer S.
Published: December 2011

Variable energy positron annihilation lifetime spectroscopy of high-mobility La-doped SrTiO3 grown by molecular beam epitaxy found that the films contained sufficiently low concentrations of Sr vacancies and vacancy cluster defects to allow the observation of positron annihilation events from the perfect lattice. This enabled the concentrations of charged cation vacancies to be estimated, and these were found to be at least an order of magnitude below the La-dopant concentrations.
Bis-EH-PFDTBT:PCBM solar cells: A compositional, thickness, and light-dependent study
Authors: Calabrese Anna , Schimperna Giuliana , Po Riccardo , Yohannes Teketel , Debebe Siraye E. , Tinti Francesca , Camaioni Nadia
Published: December 2011

Poly{[2,7-(9,9-bis-(2-ethylhexyl)-fluorene)]-alt-[5,5-(4,7-di-2′-thienyl-2,1,3-benzothiadiazole)]}:PCBM bulk heterojunction solar cells were fabricated and characterized under different incident light power intensities. Charge-trapping effects take place at low fullerene content in the photoactive blend; an efficient polymer fullerene intermixing with formation of continuous phases is reached at a donor:acceptor ratio of 1:4. For an optimized active layer thickness of 100 nm, a power-conversion efficiency of 2.57% was obtained. Photocurrent measurements under reverse-bias conditions show that a high percentage of the photogenerated excitons does not lead to the formation of free carriers, thus representing the major limiting factor for the device’s efficiency.
A transfer technique for high mobility graphene devices on commercially available hexagonal boron nitride
Authors: Zomer P. J. , Dash S. P. , Tombros N. , van Wees B. J.
Published: December 2011

We present electronic transport measurements of single and bilayer graphene on commercially available hexagonal boron nitride. We extract mobilities as high as 125 000 cm2 V−1 s−1 at room temperature and 275 000 cm2 V−1 s−1 at 4.2 K. The excellent quality is supported by the early development of the ν = 1 quantum Hall plateau at a magnetic field of 5 T and temperature of 4.2 K. We also present a fast, simple, and accurate transfer technique of graphene to hexagonal boron nitride crystals. This technique yields atomically flat graphene on boron nitride which is almost completely free of bubbles or wrinkles. The potential of commercially available boron nitride combined with our transfer technique makes high mobility graphene devices more accessible.
Modification of spermatozoa quality in mature small ruminants
Authors: Martin G. B. , de St Jorre T. Jorre , Al Mohsen F. A. , Malecki I. A.
Published: December 2011

This review is based largely, but not entirely, on the assumption that gamete quality is directly linked to sperm output and thus testicular mass, an approach made necessary by the absence of a large body of data on factors that affect gamete quality in ruminants. On the other hand, there is a change in the efficiency of sperm production per gram of testicular tissue when the testis is growing or shrinking, a clear indicator of changes in the rates of cell loss during the process of spermatogenesis, probably through apoptosis. We therefore postulate that the spermatozoa that do survive when the testis is shrinking are of a lower quality than those that are produced when the testis is growing and the rate of sperm survival is increasing. In adult small ruminants in particular, testicular mass and sperm production are highly labile and can be manipulated by management of photoperiod (melatonin), nutrition, genetics and behaviour (‘mating pressure’). Importantly, these factors do not act independently of each other – rather, the outcomes in terms of sperm production are dictated by interactions. It therefore seems likely that spermatozoa quality will be affected by these same factors, but definitive answers await detailed studies.
Adaptive responses of the embryo to maternal diet and consequences for post-implantation development
Authors: Fleming Tom P. , Lucas Emma S. , Watkins Adam J. , Eckert Judith J.
Published: December 2011

Maternal periconceptional (PC) nutrition, coupled with maternal physiological condition, can impact on reproductive performance and potential across mammalian species. Oocyte quality and embryo development are affected adversely by either nutrient restriction or excess. Moreover, the quality of maternal PC nutrition can have lasting effects through fetal development and postnatally into adulthood. Chronic disease, notably cardiovascular and metabolic disease, and abnormal behaviour have been identified in adult offspring in small and large animal models of PC nutrient restriction. These long-term effects associate with compensatory responses that begin from the time of early embryo development. This review assesses the field of PC nutrition in vivo on short- and long-term developmental consequences in rodent and ruminant models and considers the implications for human health.
Periconceptional influences on offspring sex ratio and placental responses
Authors: Rosenfeld Cheryl S.
Published: December 2011

Maternal diet and secondary factors can strikingly influence fetal outcomes, including biasing offspring sex ratio and altering the molecular biological responses of the conceptus, namely within the placenta. Alterations in the in utero environment might also lead to profound developmental origin of health and disease (DOHaD) outcomes into adulthood, including increased risk for cardiovascular disease, obesity and cancer, with males in general being at greater risk for these diseases. Female mice maintained on a very high fat (VHF) diet birth more sons than those on a chow-based and low fat (LF), high carbohydrate diet, with the latter group producing more daughters. However, neither the underlying mechanisms that contribute to this shift in offspring sex ratio nor when they occur during pregnancy have been resolved. In this review, we consider the evidence that maternal diet and other factors influence secondary sex ratio in a variety of species, including humans, and discuss when this skewing might occur. Additionally, we examine how fetal sex and maternal diet influences gene expression patterns in the mouse placenta, which serves as the primary nutrient acquisition and communication organ between the mother and her developing pups. These adaptations to diet observed as changes in gene expression are likely to provide insight into how the placenta buffers the fetus proper from environmental shifts in nutrient availability during pregnancy and whether male and female conceptuses respond differently to such challenges.
Novel aspects of endometrial function: a biological sensor of embryo quality and driver of pregnancy success
Authors: Sandra Olivier , Mansouri-Attia Nadéra , Lea Richard G.
Published: December 2011

Successful pregnancy depends on complex biological processes that are regulated temporally and spatially throughout gestation. The molecular basis of these processes have been examined in relation to gamete quality, early blastocyst development and placental function, and data have been generated showing perturbations of these developmental stages by environmental insults or embryo biotechnologies. The developmental period falling between the entry of the blastocyst into the uterine cavity to implantation has also been examined in terms of the biological function of the endometrium. Indeed several mechanisms underlying uterine receptivity, controlled by maternal factors, and the maternal recognition of pregnancy, requiring conceptus-produced signals, have been clarified. Nevertheless, recent data based on experimental perturbations have unveiled unexpected biological properties of the endometrium (sensor/driver) that make this tissue a dynamic and reactive entity. Persistent or transient modifications in organisation and functionality of the endometrium can dramatically affect pre-implantation embryo trajectory through epigenetic alterations with lasting consequences on later stages of pregnancy, including placentation, fetal development, pregnancy outcome and post-natal health. Developing diagnostic and prognostic tools based on endometrial factors may enable the assessment of maternal reproductive capacity and/or the developmental potential of the embryo, particularly when assisted reproductive technologies are applied.
Evidence for similar changes in offspring phenotype following either maternal undernutrition or overnutrition: potential impact on fetal epigenetic mechanisms
Authors: Ford S. P. , Long N. M.
Published: December 2011

The goal of this review is to shed light on the role of maternal malnutrition in inducing epigenetic changes in gene expression, leading to alterations in fetal growth and development, and to altered postnatal phenotype and the development of metabolic disease. We present evidence supporting the concept that both maternal undernutrition and overnutrition can induce the same cadre of fetal organ and tissue abnormalities and lead to the same postnatal metabolic changes in the resulting offspring. Furthermore, we present evidence that in both overnourished and undernourished ovine pregnancies, fetuses experience a period of nutrient restriction as a result of alterations in placental delivery of maternal nutrients into the fetal compartment. We argue that this bout of reduced fetal nutrition in undernourished and overnourished pregnancies leads to the development of a thrifty phenotype in which the fetus attempts to alter the function of its tissues and organs to maximise its chances of survival in a postnatal environment that is deficient in nutrients. Importantly, we present evidence to support the concept that these phenotypic changes in offspring quality resulting from maternal malnutrition are transmitted to subsequent generations, independent of their maternal nutritional inputs.
The use of endocrine treatments to improve pregnancy rates in cattle
Authors: Bisinotto R. S. , Santos J. E. P.
Published: December 2011

Reproduction is critical for the success of both dairy and beef cattle production. Inadequate reproduction impairs profitability by compromising production, delaying genetic progress and increasing expenses. A major impediment to the use of artificial insemination (AI) is the ability to detect oestrus for optimum timing of breeding. However, increased understanding of the bovine oestrous cycle has led to the development of reproductive programmes that allow precise synchrony of follicle development, luteal regression and ovulation. The advent of timed-AI protocols revolutionised reproductive management in dairy and beef herds. It allows for AI at a more desired time post partum despite oestrous cyclicity. It also allows for pre-determined re-insemination of cows diagnosed as not pregnant. In subfertile cows, such as the post partum, anoestrous beef cow and the high-producing dairy cow, strategic hormone supplementation has been used to overcome hormone deficiencies and improve pregnancy rates. Several physiological windows have been identified to optimise fertility in synchronisation programmes and they include, but are not limited to, follicle turnover, synchrony of follicular development, length of dominance, progesterone concentrations during development of the ovulatory follicle, luteal regression, peri-ovulatory steroid concentrations, length of pro-oestrus, synchrony of ovulation and AI, and progesterone rise after ovulation.
Impact of circulating concentrations of progesterone and antral age of the ovulatory follicle on fertility of high-producing lactating dairy cows
Authors: Pursley J. Richard , Martins Joäo Paulo N.
Published: December 2011

Dairy cow infertility negatively affects profit of dairy production enterprises around the world, and enhancing conception rates of dairy cows is a critical management issue to resolve. It appears that conception rates of dairy cows are attenuated due to reduced progesterone concentrations in circulation during growth of the ovulatory follicle. It is not clear how reduced progesterone influences fertility, but data presented in this brief review suggest that it can be somewhat reversed through increasing concentrations of progesterone during the growth of the ovulatory follicle before luteolysis. Ovsynch protocols may be utilised to enhance progesterone concentrations through the induction of an accessory corpus luteum (CL) following the initial gonadotropin-releasing hormone (GnRH) treatment. Cows at Day 13 of the oestrous cycle with a 7-day-old accessory CL had ~50% more progesterone at the time of prostaglandin injection of Ovsynch compared with cows with only a Day 13 CL. Ovsynch can consistently induce an accessory CL following the initial GnRH treatment if cows are on Days 6 or 7 of the oestrous cycle at the time of treatment. Pre-synchrony strategies are critical to enhance the probability that cows will be on Days 6 or 7 at first GnRH treatement of Ovsynch.
Treatments for the synchronisation of bovine recipients for fixed-time embryo transfer and improvement of pregnancy rates
Authors: Bó Gabriel A. , Peres Lucas Coelho , Cutaia Lucas E. , Pincinato Danilo , Baruselli Pietro S. , Mapletoft R. J.
Published: December 2011

Although embryo transfer technology has been used commercially in cattle for many years, the inefficiency of oestrus detection, especially in recipients, has limited the widespread application of this technology. The most useful alternative to increase the number of recipients utilised in an embryo transfer program is the use of protocols that allow for embryo transfer without the need for oestrus detection, usually called fixed-time embryo transfer (FTET). Most current FTET protocols are based on progestin-releasing devices combined with oestradiol or GnRH, which control and synchronise follicular wave dynamics and ovulation. Conception rates to a single FTET have been reported to be similar to those after detection of oestrus, but pregnancy rates are higher because these treatments have increased the proportion of recipients that receive an embryo. Recent changes to treatments for FTET, such as the administration of eCG, have resulted in increased pregnancy rates and provide opportunities to make these treatments easier to perform on farm.
117 CRYOPRESERVATION OF SNAKE SEMEN: ARE WE FROZEN IN TIME?
Authors: Zacariotti R. , Guimarães M. , Jensen T. , Durrant B.
Published: December 2011

The increasing number of endangered snake species, isolation of small fragmented populations with associated inbreeding and mating or conception problems in captivity underscore the need to develop assisted reproductive techniques such as semen cryopreservation and artificial insemination to enhance conservation efforts. However, no efficient protocols for semen evaluation, cooling, or freezing are described in the 4 known publications on snake semen cryopreservation. In this initial study, semen was collected noninvasively from 4 live adult red diamond rattlesnakes (Crotalus ruber) by ventral massage. An aliquot of each ejaculate was diluted in Ham's F10 and evaluated for motility and speed of progression (SOP, scale of 1–5, 5 being fastest) before and after freezing. Because ejaculate volumes were very small, each one was subjected to 2 to 4 treatments only. Samples were diluted in Lake's extender with 2 or 4% dimethyl sulfoxide or Test-Yolk extender with 4%, 8%, or 10% glycerol before cooling to 4°C. Semen extended with Lake's (a common avian semen extender) was then frozen by one of two protocols (FP): FP1, pelleted in liquid nitrogen vapor; FP2, placed in cryovials in an alcohol bath for 4 h in a –80°C freezer (cooling rate of 1°C min–1). Semen extended with Test-Yolk (a widely used mammalian semen extender) was frozen by one of two protocols: FP3, placed in cryovials in a controlled-rate freezer and cooled at 1°C min–1 to –20°C, then 50°C min–1 to –80°C; FP4, placed in cryovials in a controlled-rate freezer and cooled at 1°C min–1 to –8°C, then 3°C min–1 to –16°C, then 5°C min–1 to –80°C. Interestingly, semen frozen in Lake's extender exhibited no post-thaw motility, regardless of dimethyl sulfoxide concentration or FP (Table 1). In contrast, all semen frozen in Test-Yolk exhibited motility post-thaw. Semen from male 42 frozen by FP3 with 8% glycerol resulted in the greatest post-thaw motility of all treatments for both males. However, the same treatment for male 122 was not as successful, suggesting a possible male effect on semen cryosurvival (Table 1). The single sample frozen with 4% glycerol exhibited the lowest post-thaw motility, indicating that higher concentrations of the cryoprotectant may be beneficial to snake sperm. The exciting results of this preliminary study may guide future research in the long-neglected field of snake semen cryopreservation.

Table 1.Motility/speed of progression for fresh and cryopreserved semen of red diamond rattlesnakes frozen with Test-Yolk extender and glycerol
124 RELATIONSHIPS BETWEEN PREOVULATORY FOLLICLE AND CORPUS LUTEUM BLOOD FLOW IN MARES
Authors: Wischral A. , Haag K. T. , Fonseca G. R. , Gastal M. O. , King S. S. , Gastal E. L.
Published: December 2011

Colour- and power-Doppler ultrasonography have recently been used as potential new technologies to assess the degree of vascular perfusion of the ovary and follicles for research and clinical studies of ovarian and follicle hemodynamics and to predict fertility in horses, cattle and humans. In the present study, the following hypotheses were tested: (1) preovulatory follicle (POF) diameter (≥30 mm), but not blood flow, is repeatable between cycles within the same mare; (2) POF diameter and blood flow are good indicators of follicle status; (3) double POF have similar blood flow; and (4) highly vascularized POF produce corpora lutea (CL) with greater blood flow. Non-lactating mares (n = 13; 5 to 21 years old) of mixed breeds were used from March to May in the Northern Hemisphere. Follicle diameter and vascularity of the follicle wall before the first and second ovulations of the season and vascularity of the first CL were measured daily using transrectal colour-Doppler ultrasonography. The vascularity of the follicle wall and CL was based on the display of the blood-flow signals visualised in a slow, continuous-motion evaluation. Statistical analyses were performed by the SAS MIXED procedure, ANOVA and Student's t-tests and Spearman's correlation. A total of 26 periovulatory periods were evaluated. Unexpectedly, there were 84.6% (11/13) and 61.5% (8/13) double dominant POF and 30.8% (4/13) and 46.2% (6/13) double ovulations in the first and second periovulatory periods, respectively. The POF diameters were highly correlated (r = 0.68; P < 0.0001) between the first and second periovulatory periods. The diameter of the POF 5 days before the first ovulation was larger (P < 0.004) than before the second ovulation of the year. However, the POF vascularity did not differ between those periods. For 4 days before ovulation (Day 0), the diameter and blood flow of the POF were greater (P < 0.05) than for those follicles that underwent atresia in single- and double-ovulatory mares. The POF diameter and blood flow were positively correlated in ovulatory (r = 0.51; P < 0.0001) and in atretic (r = 0.32; P < 0.02) follicles. In double-ovulatory mares, POF diameter and blood flow increased (P < 0.0006) for 5 days before ovulation, with no difference between the 2 follicles in the same cycle for each parameter. The POF blood flow was positively correlated (r = 0.32; P < 0.0009) with CL vascularity during the first periovulatory period (Day –7 to +6) of the season. Furthermore, a positive correlation (r = 0.58; P < 0.01) was observed between the maximum vascularity of the POF and its subsequent CL. In conclusion, although preliminary, our results demonstrated that (a) POF vascularity is not repeatable within individuals; (b) potential atretic POF have low blood flow; (c) double POF have similar vascularity; and (d) greater blood flow to the POF is associated with higher CL vascularity.
128 BOVINE SEMINAL PLASMA INDUCES OVULATION IN LLAMAS
Authors: Tribulo P. , Bogle O. A. , Adams G. P.
Published: December 2011

Ovulation-inducing factor (OIF) is a protein present in the seminal plasma of several species, including llamas, alpacas, pigs, cattle, sheep, horses and rabbits. In an initial study (Ratto et al. 2006 Theriogenology 66, 1102–1106), bovine seminal plasma induced ovulations in 26% (5/19) of llamas compared with 0% (0/19) in the placebo group, but induced proportionately less than in llamas treated with alpaca or llama seminal plasma (100%). It is important to highlight that treatments were based on volume of seminal plasma; the actual dose of OIF was unknown. In a later study (Tanco et al. 2011 Biol. Reprod. doi:10.1095/biolreprod.111.091876), OIF from llama seminal plasma had a dose-dependent effect on ovulation rate, corpus luteum (CL) diameter and progesterone production in llamas. The present study was designed to test the hypothesis that bovine seminal plasma induces ovulation and CL development in llamas comparable with that of llama seminal plasma, based on total dose of OIF. Within species, seminal plasma was pooled from 1 to 4 ejaculates per male (n = 145 bulls, n = 4 llamas). The concentration of OIF in the pooled seminal plasma was measured by radioimmunoassay and the volume of seminal plasma used for treatment was adjusted to reach a total dose of 250 μg of OIF. Mature female llamas were assigned randomly to 4 groups and given a single intramuscular dose of 10 mL of PBS (negative control, n = 5), 50 μg of gonadotropin-releasing hormone (GnRH; positive control, n = 5), 6 mL of llama seminal plasma (n = 6), or 12 mL of bull seminal plasma (n = 6). Ovulation and CL development were monitored by transrectal ultrasonography. The incidence of ovulation was compared among groups by Fisher's exact test. Nonserial data (i.e. follicle size at treatment, maximum CL diameter, day of maximum CL diameter and first day of CL detection) were compared among groups by ANOVA. The diameter of the preovulatory follicle at treatment did not differ among groups (P = 0.10). The incidence of ovulation was 0/5, 4/5, 3/6 and 4/6 in the groups treated with PBS, GnRH, llama seminal plasma and bovine seminal plasma, respectively (P < 0.05). The incidence of ovulation did not differ among llamas treated with GnRH, llama seminal plasma, or bovine seminal plasma. Among the treatments that elicited ovulation, neither the maximum CL diameter nor the day of maximum CL diameter differed (P = 0.30 and P = 0.24, respectively). In addition, no difference was detected in the day of first detection of the CL (P = 0.25). Results document the bioactivity of OIF in the bovine seminal plasma of Bos taurus. These findings further support the notion that OIF is highly conserved among mammals and that seminal plasma exerts its effect in an OIF dose-related manner.
This research was supported by the Natural Sciences and Engineering Research Council of Canada.
167 INFLUENCE OF THE SPERM SELECTION METHOD AND FERTILIZATION DOSES ON CHROMOSOMAL ABNORMALITY RATES OF 4-DAY-OLD BOVINE EMBRYOS
Authors: Demyda Peyrás S. , De Luca L. J. , Moreno Millán M.
Published: December 2011

This cytogenetic study was conducted to quantify the incidence and type of chromosomal abnormalities on in vitro-produced bovine embryos. Eight groups of 150 in vitro-matured oocytes were IVF for 18 h. Final sperm concentrations of 1 × 104, 1 × 105, 1 × 106 and 1 × 107 cells mL–1 selected by the washing method or the swim-up method were utilised. Presumptive zygotes were cultured for 96 h, collected and fixed individually for analysis. Chromosomal complements of 447 embryos were determined by Giemsa staining and direct observation. Rates of haploidy, diploidy, aneuploidy and polyploidy were determined individually. The incidence of chromosomal abnormalities in embryos derived by IVF with 1 × 104, 1 × 105 and 1 × 106 cells mL–1 did not differ regardless of the sperm preparation method. Polyploidy incidence was strongly increased (P < 0.01) at a concentration of 1 × 107 cells mL–1 in both sperm treatment groups. The fertilization rate obtained with a 1 × 104 cells mL–1 sperm dose in both selection methods and with a 1 × 105 cells mL–1 sperm dose with the washing selection method were significantly lower (P < 0.05) than those obtained with the other sperm concentrations. The lowest fertilization rates (P < 0.05) were achieved with the lowest dose and the washing sperm selection technique. Acceptable fertilization rates with low chromosomal abnormalities can be achieved with a final sperm concentration of 1 × 105 cells mL–1 or higher regardless of the sperm selection method used. In conclusion, the sperm selection method did not result in differences in the chromosomal abnormality rates on in vitro-produced bovine embryos. The use of high sperm concentration doses produced unacceptable rates of such abnormalities regardless of the sperm selection method. The use of very low sperm doses produced unacceptable fertilization rates, especially when the washing sperm selection method was performed.
Sebastián Demyda Peyrás is an MAEC–AECID grantee.
185 PARTHENOGENETIC ACTIVATION OF SIKA DEER (CERVUS NIPPON TEMMINCK) OOCYTES WITH CHEMICALS
Authors: Yin Y. P. , Tang L. N. , Fan A. R. , Zhang S. , Ma X. , Tang B. , Li Z. Y.
Published: December 2011

Parthenogenetic activation of the oocyte represents an important step in the somatic cell nuclear transfer. The aim of the present study was to establish optimizing conditions for parthenogenetic activation of Sika deer oocytes necessary for cloning Sika deer. Sika deer ovaries were collected from a slaughter house during oestrus season (October and November), placed into saline (25°C) supplemented with 1% (v/v) penicillin and streptomycin and transported into the laboratory within 4 h. The small vesicular follicles (diameter, 2–5 mm) on the ovarian surface were incised with a scalpel in a Petri dish containing PBS to release the cumulus–oocyte complexes (COC). Only COC with uniform cytoplasm and at least 3 layers of compact cumulus cells were cultured in vitro for 24 h. The media of in vitro maturation (IVM) was TCM-199 supplemented with 10% fetal bovine serum, 10 μg mL–1 FSH, 1 μg mL–1 LH, 0.2 mM cysteamine and 50 ng mL–1 epidermal growth factor. After IVM, the cumulus cells were denuded with 0.2% hyaluronidase in TCM-199 at 38.5°C by pipetting. The cumulus-free Sika deer oocytes were stimulated by 1 of the following treatments: 1) ethanol + 6-DMAP, treated with 7% ethanol for 7 min and 2 mM 6-dimethylaminopurine (6-DMAP) in DSOF for 4 h; or 2) ionomycin + 6-DMAP, treated with 5 μM ionomycin for 5 min and 2 mM 6-DMAP in DSOF for 4 h. Then, oocytes were transferred into culture media for 7 days [Day 0 (D0) = activation]. On D3, embryos were transferred into fresh DSOF drops supplemented with 10% (v/v) fetal bovine serum. All cultures were overlaid with mineral oil and kept in a humidified modular incubation chamber gassed with 5% CO2. Effects of these chemicals on oocyte activation were then examined and compared with the controls, in which oocytes were cultured in TCM-199 for 4 h without chemical supplement. Our results showed that rates of cleavage, morula and blastocyst were 72.7, 43.9 and 32.4% (n = 139), respectively, by treatment with ionomycin + 6-DMAP. And rates of cleavage, morula and blastocyst were 61.1, 29.7 and 17.8% (n = 134), respectively, by treatment with ethanol + 6-DMAP. However, the rates of cleavage, morula and blastocyst were 5, 0 and 0% (n = 101) in the control group. Meanwhile, the rates of oocyte cleavage (72.7% vs 61.1%), morula (43.9% vs 29.7%) and blastocyst (32.4% vs 17.8%) between 2 treatments of ionomycin + 6-DMAP and ethanol + 6-DMAP were significantly different (P < 0.05). In conclusion, parthenogenetic activation of Sika deer oocytes with ionomycin + 6-DMAP is more effective than that with ethanol + 6-DMAP. These results have begun to elucidate parameters important for animal modeling and cloning with the Sika deer and should facilitate the development of genetically defined animal models in this species.
This work was supported by the grant from the China Postdoctoral Science Foundation (No. 20090451135).
202 SEX PRE-SELECTION IN RABBITS: AN ATTEMPT TO SKEW OFFSPRING SEX THROUGH PERCOLL AND SWIM-UP SPERM PREPARATION TECHNIQUES
Authors: Copello M. , Perez A. , Marquez S. , Sansinena M.
Published: December 2011

Sperm preparation techniques could have an effect on the birth ratio (male vs female offspring) through enrichment of either X- or Y-bearing sperm populations, although studies have been poorly controlled and results have been inconclusive. In the rabbit, producers may be interested in producing a majority of males (meat producing systems) or females (hybrid producing systems). The objective of this study was to evaluate the effect of modified Percoll and Swim-up protocols on the enrichment of the male and female birth ratios in rabbits. Four hybrid mature bucks of adequate body condition score and proven fertility were used. The same four bucks were used throughout the study (8 replicates). Ejaculates were collected using a warmed, solid, artificial vagina. Progressive motility was assessed at 200× magnification under brightfield microscopy on a heated (37°C) stage. Sperm concentration for each buck was determined using a Neubaur chamber and adjusted (350 × 106 total spermatozoa mL–1); they were then combined (1 mL/buck) to form a heterospermic sample (final heteropsermic sample volume = 4 mL). The heteropsermic sample was then divided into 3 sperm preparation treatments: (1) diluted in commercial tri-buffered extender followed by immediate AI (control); (2) modified Percoll centrifugation in a 90 to 45% density gradient (diluted in human tubal fluid medium); and (3) Swim-up (in human tubal fluid medium). In total, 125 females were inseminated. Does were treated with PMSG (20 UI/doe, 48 h before AI) and inseminated with 30 to 40 × 106 spermatozoa; ovulation was induced with 20 μg of gonadotropin-releasing hormone (GnRH)/doe immediately after AI. Sex of newborn kits was determined 35 days after birth by an experienced technician through external visualization of genitalia. Results were statistically analyzed using ANOVA and Tukey test (Infostat). The insemination of does with heterospermic ejaculates (control) resulted in a progeny distribution of 49 ± 2% males and 51 ± 2% females, which is in good agreement with the expected theoretical 50:50 ratio. Sex ratios from modified Percoll and Swim-up treatments deviated significantly from the control (P < 0.01). Percoll gradient resulted in a progeny distribution of 32 ± 2% males and 68 ± 2% females; Swim-up resulted in a 64 ± 2% male and a 36 ± 2% female distribution (P < 0.01), whereas prolificacy, perinatal mortality and birth weight were not affected by treatment (Table 1). Our results indicate sperm preparation techniques could be used to skew birth ratios towards male or female offspring in rabbits; Percoll preparation could be used to increase proportion of female kits whereas Swim-up could be used to increase the proportion of males. Further studies are needed to determine the underlying mechanisms of action.

Table 1.Progeny distribution after Percoll or Swim-up sperm preparation in rabbits