bluuebunny/crossref_metadata_2025 huggingface dataset:
Baptism of ice: J. G. Bartholomew and the naming of Antarctica
Authors: Mawer G.A.
Published: January 2008

As a proper noun, Antarctica has a long pedigree but a short history. It was coined and popularised by the Edinburgh mapmaker J. G. Bartholomew in the 1890s as a label for the supposed south polar continent outlined by John Murray of the Challenger Commission. By 1902 it was ‘slowly coming into use’ and by 1928 had been ‘generally received’ by geographers.
Defining products for a new health technology assessment agency in Madrid, Spain: A survey of decision makers
Authors: Andradas Elena , Blasco Juan-Antonio , Valentín Beatriz , López-Pedraza María-José , Gracia Francisco-Javier
Published: January 2008

Objectives:The aim of this study was to explore the needs and requirements of decision makers in our regional healthcare system for health technology assessment (HTA) products to support portfolio development planning for a new HTA agency in Madrid, Spain.

Methods:A Delphi study was conducted during 2003. Questionnaires were developed based on a review of products and services offered by other agency members of the International Network of Agencies for Health Technology Assessment, and included preference and prioritization questions to evaluate twenty-two different products and services. The initial Delphi panel involved eighty-seven experts from twenty-one public hospitals, eleven primary healthcare centers, six private hospitals, and eight departments of the Regional Ministry of Health of the Community of Madrid.

Results:The global participation rate was 83.9 percent. Ten of the twenty-two possible products were rated of high interest by more than 80 percent of respondents. Important differences in preferences and priorities were detected across different settings. Public hospitals and primary healthcare centers shared a more “micro” perspective, preferring classic technology-centered HTA products, whereas private hospitals and Ministry representatives demanded more “macro” products and services such as organizational model and information system assessments.

Conclusions:The high participation rate supports the representativeness of the results for our regional context. The strategic development of an HTA portfolio based on decision makers’ needs and requirements as identified in this type of exercise should help achieve a better impact on policy development and decision making.
Measuring the validity of early health technology assessment: Bibliometrics as a tool to indicate its scientific basis
Authors: Lundberg Jonas , Brommels Mats , Skår John , Tomson Göran
Published: January 2008

Objectives:The aim of this study was to assess whether publications of importance for improving the health system and its technologies are highly cited intrascientifically.

Methods:Bibliometric assessment of the 596 publications used as sources in the fifty SBU Alerts from 2001to 2004 from the Swedish Council on Technology Assessment in Health Care was carried out using the Thomson Scientific citation indexes. Normalized citation scores were calculated for all included studies. Additional factors such as the time and place of the research, subject categories, and journal source were analyzed.

Results:On average, the sources in SBU Alert have been cited eight times more than the world average consistently during the time period and across research areas. Articles used as its scientific basis are often published in a few, high impact, general medical journals. However, many of the articles are published in field-specific journals with low impact factors. Most articles used in SBU Alert are published by authors based in the United States or the United Kingdom. However, Swedish, Danish, and Dutch publications are overrepresented in its science base, whereas Japanese, Taiwanese, Indian, and Russian publications are underrepresented.

Conclusions:Publications used as sources in a Swedish system for identification and early assessment of new methods in health care are also highly cited within the scientific community. This finding increases the appropriateness of using bibliometric indicators in evaluations of clinical research and suggests that decision makers through SBU Alert are getting scientifically sound advice.
Does income influence demand for medical services despite Japan's “Health Care for All” policy?
Authors: Babazono Akira , Kuwabara Kazuaki , Hagihara Akito , Yamamoto Eiji , Hillman Alan
Published: January 2008

Objectives:We examined the impact of household income on the use of medical services in Japan, where there is a “health care for all” policy, with important, centralized influence by the national government designed to ensure universal access.

Methods and Subjects:All healthcare societies operating in 2003 were included in the study, representing 14,776,193 insured adults and 15,496,752 insured dependents. The mean case rate (the average number of monthly bills per patient), the mean number of service days per person, and the mean medical cost per person served as indicators of medical service use. Multiple regression analysis was performed by the forced entry method using case rate, the number of service days, and medical cost as outcome variables, and average monthly salary, dependent ratio, average age, and premium rate as the explanatory variables.

Results:In the multiple regression analyses, average monthly salary showed a high positive correlation of outpatient and dental indicators, including case rate, the number of service days, and medical cost. If the average monthly salary were reduced 20 percent lower than the mean, the estimated changes (95 percent CI) in case rate for the insured were −7.49 (−8.14 ∼ −6.84) percent for outpatient visits and −8.16 (−8.77 ∼ −7.56) percent for dental services.

Conclusions:Average monthly salary intensifies the effects of copayments on the case rate, the number of service days, and medical cost in the “Employees Health Insurance” in Japan. Thus, a low salary appears to discourage patients from seeking medical and dental services.
QUEUING, SOCIAL INTERACTIONS, AND THE MICROSTRUCTURE OF FINANCIAL MARKETS
Authors: HORST ULRICH , ROTHE CHRISTIAN
Published: January 2008

We consider an agent-based model of financial markets with asynchronous order arrival in continuous time. Buying and selling orders arrive in accordance with a Poisson dynamics where the order rates depend both on past prices and on the mood of the market. The agents form their demand for an asset on the basis of their forecasts of future prices and their forecasting rules may change over time as a result of the influence of other traders. Among the possible rules are “chartist” or extrapolatory rules. We prove that when chartists are in the market, and with choice of scaling, the dynamics of asset prices can be approximated by an ordinary delay differential equation. The fluctuations around the first-order approximation follow an Ornstein–Uhlenbeck dynamics with delay in a random environment of investor sentiment.
Mannheimia haemolyticaand bovine respiratory disease
Authors: Rice J. A. , Carrasco-Medina L. , Hodgins D. C. , Shewen P. E.
Published: January 2008

Mannheimia haemolyticais the principal bacterium isolated from respiratory disease in feedlot cattle and is a significant component of enzootic pneumonia in all neonatal calves. A commensal of the nasopharynx,M. haemolyticais an opportunist, gaining access to the lungs when host defenses are compromised by stress or infection with respiratory viruses or mycoplasma. Although several serotypes act as commensals, A1 and A6 are the most frequent isolates from pneumonic lungs. Potential virulence factors include adhesin, capsular polysaccharide, fimbriae, iron-regulated outer membrane proteins, leukotoxin (Lkt), lipopolysaccharide (LPS), lipoproteins, neuraminidase, sialoglycoprotease and transferrin-binding proteins. Of these, Lkt is pivotal in induction of pneumonia. Lkt-mediated infiltration and destruction of neutrophils and other leukocytes impairs bacterial clearance and contributes to development of fibrinous pneumonia. LPS may act synergistically with Lkt, enhancing its effects and contributing endotoxic activity. Antibiotics are employed extensively in the feedlot industry, both prophylactically and therapeutically, but their efficacy varies because of inconsistencies in diagnosis and treatment regimes and development of antibiotic resistance. Vaccines have been used for many decades, even though traditional bacterins failed to demonstrate protection and their use often enhanced disease in vaccinated animals. Modern vaccines use culture supernatants containing Lkt and other soluble antigens, or bacterial extracts, alone or combined with bacterins. These vaccines have 50–70% efficacy in prevention ofM. haemolyticapneumonia. Effective control ofM. haemolyticapneumonia is likely to require a combination of more definitive diagnosis, efficacious vaccines, therapeutic intervention and improved management practices.
Confirmation and utilization of the “production function” size‐frequency distributions of Martian impact craters
Authors: Hartmann William K. , Neukum Gerhard , Werner Stephanie
Published: January 2008

On any planetary surface, impacts of interplanetary bodies create an initial (or “production function”) size‐frequency distribution (SFD) of impact craters. Recent questions have been raised about whether this size distribution can be reliably detected, especially at small sizes. In a test area, we confirm an excellent fit to the distribution we have used previously, at diameters 11 m < D ≲ 1 km. At D ≳ 1 km, images with the High Resolution Stereo Camera (HRSC) allow us to confirm earlier proposals on how the burial of old small craters by lava flows can distort the SFD curve in some areas. As a product of this analysis, we present a new tool for quantitative analysis of geologic processes on Mars, namely use of crater statistics to interpret subsurface structure.
Multiple‐step geomagnetic storms and their interplanetary drivers
Authors: Richardson I. G. , Zhang J.
Published: January 2008

While the classic picture of a geomagnetic storm is of a main phase eventually reaching maximum intensity, followed by a recovery, the profile can often be more complex. This has been recognized in past studies that have classified storms as having “one” or “two” “steps” during the main phase. However, the intense (Dst ≤ −100 nT) storms studied during the LWS CDAW Workshop may be more complicated. We discuss the variety of interplanetary circumstances that gave rise to several storms of varying complexity.
Exciplex emission from electroluminescent ladder-type pentaphenylene oligomers bearing both electron- and hole-accepting substituents
Authors: Finlayson Chris E. , Kim Ji-Seon , Liddell Matthew J. , Friend Richard H. , Jung Sung-Hyun , Grimsdale Andrew C. , Müllen Klaus
Published: January 2008

We examine the photophysical properties of ladder-type pentaphenylenes, which have been prepared as prototypical “all-in-one” emissive materials bearing both electron-accepting (diaryloxadiazole) and electron-donating (triphenylamine) units. We find that donor-acceptor interactions are very dependent on the nature of the connectivity of these groups to the main pentaphenylene chain. When the oxadiazole and triphenylamine units were substituted on opposite sides of the π-conjugated pentaphenylene chromophore, photoluminescence with long lifetimes typical of exciplex-like species was observed, while being significantly quenched by intermolecular charge separation between the substituents. By contrast, when the triphenylamine units were attached at the ends of the chromophore, no such effects were observed and a blue/green photoluminescence was obtained with very high quantum efficiency. In this latter configuration, evidence of ambipolar charge transport and a blue/green electroluminescence were additionally observed.
High-resolution infrared spectroscopy of jet-cooled vinyl radical: Symmetric CH2 stretch excitation and tunneling dynamics
Authors: Dong Feng , Roberts Melanie , Nesbitt David J.
Published: January 2008

First high-resolution IR spectra of jet-cooled vinyl radical in the CH stretch region are reported. Detailed spectral assignments and least squares fits to an A-reduction Watson asymmetric top Hamiltonian yield rotational constants and vibrational origins for three A-type bands, assigned to single quantum excitation of the symmetric CH2 stretch. Two of the observed bands arise definitively from ground state vinyl radical, as rigorously confirmed by combination differences predicted from previous midinfrared CH2 wagging studies of Kanamori et al. [J. Chem. Phys. 92, 197 (1990)] as well as millimeter wave rotation-tunneling studies of Tanaka et al. [J. Chem. Phys. 120, 3604 (2004)]. The two bands reflect transitions out of symmetric (0+) and antisymmetric (0−) tunneling levels of vinyl radical populated at 14K slit-jet expansion temperatures. The band origins for the lower-lower (0+←0+) and upper-upper (0−←0−) transitions occur at 2901.8603(7) and 2901.9319(4)cm−1, respectively, which indicates an increase in the tunneling splitting and therefore a decrease in the effective tunneling barrier upon CH2 symmetric stretch excitation. The third A-type band with origin at 2897.2264(3)cm−1 exhibits rotational constants quite close to (but at high-resolution distinguishable from) the vinyl radical ground state, consistent with a CH2 symmetric stretch hot band built on one or more quanta of excitation in a low frequency vibration. The observed CH2 symmetric stretch bands are in excellent agreement with anharmonically scaled high level density functional theory (DFT) calculations and redshifted considerably from previous low resolution assignments. Of particular dynamical interest, Boltzmann analysis indicates that the pair of 0+ and 0− tunneling bands exhibits 1:1 nuclear spin statistics for Ka=even:odd states. This differs from the expected 3:1 ratio for feasible exchange of the two methylenic H atoms but is consistent with a 4:4 ratio predicted for interchange between all three H atoms. This suggests the novel dynamical possibility of large amplitude “roaming” of all three H atoms in vinyl radical, promoted by high internal vibrational excitation arising from dissociative electron attachment in the discharge.
Monte Carlo simulation of electrical double-layer formation from mixtures of electrolytes inside nanopores
Authors: Hou Chia-Hung , Taboada-Serrano Patricia , Yiacoumi Sotira , Tsouris Costas
Published: January 2008

The formation of the electrical double layer (EDL) in the presence of trivalent and monovalent ions inside a slit-type nanopore was simulated via the canonical Monte Carlo method using a primitive model. In large pores, the distribution of ionic species is similar to that observed in an isolated planar double layer. Screening of surface charge is determined by the competitive effects between ion size and charge asymmetry of the counterions. On the other hand, as the pore size approaches the dimension of the ionic species, phenomena such as EDL overlapping become enhanced by ion-size effects. Simulation results demonstrate that EDL overlapping is not only a function of such parameters as ionic strength and surface charge density, but also a function of the properties of the ionic species involved in the EDL. Furthermore, charge inversion can be observed under certain conditions when dealing with mixtures of asymmetric electrolytes. This phenomenon results from strong ion-ion correlation effects and the asymmetries in size and charge of ionic species, and is most significant in the case of trivalent counterions with larger diameters. The simulation results provide insights into the fundamental mechanisms behind the formation of EDL within nanopores as determined by pore size and by the properties of ionic species present in solution. The findings of this work are relevant to ion sorption and transport within nanostructured materials.
Generalization of the classical Kramers rate for non-Markovian open systems out of equilibrium
Authors: Bolivar A. O.
Published: January 2008

We analyze the behavior of a Brownian particle moving in a double-well potential. The escape probability of this particle over the potential barrier from a metastable state toward another state is known as the Kramers problem. In this work, we generalize Kramers’ rate theory to the case of an environment always out of thermodynamic equilibrium reckoning with non-Markovian effects.
First-principles study of length dependence of conductance in alkanedithiols
Authors: Zhou Y. X. , Jiang F. , Chen H. , Note R. , Mizuseki H. , Kawazoe Y.
Published: January 2008

Electronic transport properties of alkanedithiols are calculated by a first-principles method based on density functional theory and nonequilibrium Green’s function formalism. At small bias, the I-V characteristics are linear and the resistances conform to the Magoga’s exponential law. The calculated length-dependent decay constant γ which reflects the effect of internal molecular structure is in accordance with most experiments quantitatively. Also, the calculated effective contact resistance R0 is in good agreement with the results of repeatedly measuring molecule-electrode junctions [B. Xu and N. Tao, Science 301, 1221 (2003)].
Uncovering the physical origin of the difference between aliphatic chain and aromatic ring in the “hydrophobic” effects on partial molar volume
Authors: Imai Takashi , Hisadomi Yu , Sawamura Seiji , Taniguchi Yoshihiro
Published: January 2008

The partial molar volume changes in the transfer of several hydrophobic molecules, which are composed of aromatic rings and an aliphatic chain of different lengths, from carbon tetrachloride to water (ΔVhyd) are calculated using the three-dimensional interaction site model theory of molecular solvation. The theory reproduces recent experimental observations: the addition of a methyl group decreases ΔVhyd; in contrast, the addition of an aromatic ring increases ΔVhyd. The discrepancy is found to originate from the difference between chain and ring structures rather than that between aliphaticity and aromaticity. Furthermore, a general rule of the variation in ΔVhyd due to the addition of a hydrocarbon is found through the theoretical analysis. An outward addition at the trans position, which is to form chain structure, decreases ΔVhyd, while an inward addition at the cis position, which is to form ring structure, increases ΔVhyd. This is explained in terms of solvent packing rather than the so-called hydrophobic hydration. The present findings argue against the traditional idea that the hydrophobic hydration can be represented by the observed values of ΔVhyd.
Structural, magnetic, and electrical properties of Co2MnSi∕MgO∕n-GaAs tunnel junctions
Authors: Kawagishi S. , Uemura T. , Imai Y. , Matsuda K.-I. , Yamamoto M.
Published: January 2008

The structural, magnetic, and electrical properties of Co2MnSi (CMS)/MgO (0–3.0nm)∕n-GaAs tunnel junctions were investigated. CMS films with L21-ordered structures were grown epitaxially on GaAs. The crystallographic relations were CMS(001)[100]∥GaAs(001)[110] when a thin MgO interlayer was inserted between the CMS and the GaAs, and CMS(001)[110]∥GaAs(001)[110] when the CMS film was directly grown on GaAs without a MgO interlayer. The CMS film without a MgO interlayer showed strong magnetic anisotropy consisting of uniaxial anisotropy with an easy axis of CMS[1−10] (GaAs[1−10]) direction and cubic anisotropy with easy axes of CMS⟨110⟩ directions. The uniaxial anisotropy was weakened in the samples with a MgO interlayer. The magnetization value of the CMS film with a 3.0-nm-thick MgO layer was approximately 820emu∕cm3 (3.9μB∕f.u.) at room temperature (RT), a value slightly higher (∼7%) than that of the sample without MgO. The resistance value of the CMS/MgO (3.0nm)∕n-GaAs junction was approximately two to three orders of magnitude higher than that of the CMS∕n-GaAs junction at RT. The potential height and width of the tunnel barrier in the CMS∕MgO∕n-GaAs junction were estimated to be 0.6eV and 3.3nm, respectively.
Diffuse second harmonic generation under the ferroelectric switching in Sr0.75Ba0.25Nb2O6 crystals
Authors: Isakov D. V. , Belsley M. S. , Volk T. R. , Ivleva L. I.
Published: January 2008

In this work, we present observations of the polarization process in strontium barium niobate Sr0.75Ba0.25Nb2O6 (SBN-0.75) crystals by measuring the diffuse generation of the second harmonic converted by the random ferroelectric domains. The ability of a field-controlling intensity of the diffuse second harmonic generation is analyzed and discussed in terms of the specific switching scenario in SBN crystals.
Debye-shielding potential in the presence of pair correlations
Authors: Bose Anirban , Janaki M. S.
Published: January 2008

The first-order kinetic equation of the Bogoliubov–Born–Green–Kirkwood–Yvon hierarchy of equations for an equilibrium inhomogeneous plasma is shown to contain an effective force resulting from pair correlations that depends on the gradient of the average electric field modulus. Such a kinetic equation is utilized to obtain a Boltzmann distribution that includes the effects of correlations. For an electron-ion plasma with stationary ions and finite electron-electron correlations, the nature of the Debye-screening potential is investigated.
Nucleation fields in composite medium grains
Authors: Bertram H. N. , Schabes M. E. , Lomakin V. , Livshitz B.
Published: January 2008

An expression for the nucleation field from initial saturation of magnetization reversal is derived for a two-layer magnetic system with variable interlayer exchange coupling. Nonuniform domain wall-like rotations are considered in both films. A relatively simple relation occurs when magnetostatic interactions are neglected and the reversal field is applied along the particle symmetry axis. The results are compared with numerical micromagnetic solutions that inlcude magnetostatic interactions. Good agreement is obtained for a range of parameters, especially when the interlayer exchange is chosen to minimize the system coercivity. Expansion of the model to more than two interacting layers is discussed.
Reduction of a coercive field in the bilayers of CoGdTb∕NiFe with perpendicular magnetic anisotropy
Authors: Lee Seung-Kyo , Nam Chunghee , Lee Ki-Su , Jang Youngman , Cho B. K.
Published: January 2008

We have investigated the magnetic properties of CoGdTb∕NiFe bilayer with the variation of NiFe thickness (tNiFe). It was found that the composition of CoGdTb layer can be controlled by adjusting the Ar working pressure of the sputtering system. We used a CoGdTb∕NiFe bilayer with the Co concentration of 82.2at.%, which was deposited at an Ar working pressure of 3mTorr, to investigate the bilayer coercivity. The deposition of NiFe (tNiFe=1.5nm) on the CoGdTb layer caused the increase of the coercive field. It was found from the in-plane and out-of-plane hysteresis loops that the NiFe moments were aligned out of plane due to the strong coupling between NiFe and CoGdTb, leading to the increase of the coercive field. With the increase of the NiFe thickness (tNiFe=5nm), the coercive field of CoGdTb decreased rapidly, which was likely to be caused by the in-plane component of NiFe moments. With further increase of the NiFe thickness (tNiFe=10 and 15nm), no more reduction of the coercive field was observed although more portion of NiFe moments was in plane. We conjectured that the in-plane NiFe moments within the limited area near the interface between CoGdTb and NiFe contributed to the reduction of the coercive field of CoGdTb.
Theoretical and experimental investigation of gigahertz-band, temperature-compensated electromechanical coupling configurations based on AlN films
Authors: Caliendo Cinzia
Published: January 2008

Highly c-axis oriented piezoelectric AlN films were sputtered on (0001) Al2O3 substrates and four gigahertz-range surface acoustic wave (SAW) electroacoustic coupling configurations were realized by conventional photolithographic process. The thermal sensitivity of each device was experimentally estimated and found in good accordance with the theoretical predictions. Eight gigahertz-range, thermally compensated SAW devices were obtained for specific AlN thickness, SAW propagation direction, and electrical boundary conditions. A theoretical analysis of the acoustic and electrical behavior of the four coupling structures is proposed to match the achievable performances of the SAW devices with the design requirements.
Self-assembled Ge nanocrystals on BaTiO3∕SrTiO3∕Si(001)
Authors: Largeau L. , Patriarche G. , Saint-Girons G. , Delhaye G. , Hollinger G.
Published: January 2008

The structure of Ge nanocrystals (NC) grown on BaTiO3 (BTO)∕SrTiO3∕Si(001) is studied by high resolution transmission electron microscopy. The Ge NC are fully relaxed with {111}, {112}, {110}, and {113} planes parallel to the interface. These orientations allow to align one Ge⟨110⟩ in-plane direction with one BTO⟨100⟩ in-plane direction leading to a minimization of the mismatch in the BTO⟨100⟩ direction. Surprisingly, no NC with {100} planes parallel to the interface, leading to a minimization of the mismatch along the two BTO⟨100⟩ in-plane directions, are observed. This is interpreted in terms of surface energy minimization.
Comparison of different sperm cryopreservation procedures on post-thaw quality and heterologous in vitro fertilisation success in the ocelot (Leopardus pardalis)
Authors: Stoops Monica A. , Bond Jennifer B. , Bateman Helen L. , Campbell Mark K. , Levens Gregory P. , Bowsher Todd R. , Ferrell Shannon T. , Swanson William F.
Published: January 2008

Cryopreservation of spermatozoa from free-living ocelots (Leopardus pardalis) could benefit their conservation by facilitating gene flow between in situ and ex situ populations without requiring removal of additional cats from the wild. The objective of this study was to investigate three different methods of ocelot sperm cryopreservation to identify the most appropriate technique for use in a field environment. Male ocelots (n = 10), housed in North American zoos, were anaesthetised with tiletamine–zolazepam (7mg kg–1 bodyweight; i.m.) and subjected to a regimented electroejaculation procedure. Recovered semen was evaluated for sperm concentration, motility and morphology and processed for cryopreservation by three methods: (1) pelleting on dry ice, (2) freezing in straws over liquid nitrogen vapour; and (3) freezing in straws in a dry shipper. Frozen samples were thawed and assessed for post-thaw acrosome status, viability, motility over time and ability to fertilise viable domestic cat oocytes. Although several post-thaw sperm parameters varied (P < 0.05) among freezing methods, frozen–thawed ocelot spermatozoa from all treatments showed a similar (P > 0.05) capacity to bind, penetrate and fertilise viable domestic cat oocytes. These findings suggest that spermatozoa collected from male ocelots under field conditions may be frozen in straws either using liquid nitrogen alone or in a charged dry shipper to retain adequate functional competence after thawing for use with assisted reproductive procedures.
Expression of the glucocorticoid receptor and 11β-hydroxysteroid dehydrogenase 2 in pig testes cells along fetal development
Authors: Haeussler S. , Claus R.
Published: January 2008

The glucocorticoid (GC)–cortisol receptor (GCR)–11β-hydroxysteroid dehydrogenase 2 (11β-HSD2) system is involved in the regulation of Leydig cell function and spermatogenesis in mature animals. Herein, we describe the expression of the GCR and 11β-HSD2 and the occurrence of apoptosis during fetal development. Male fetuses were collected from Weeks 6, 10, 13, and 15 of pregnancy and from neonates. The testes were used for the immunocytochemical staining of GCR, 11β-HSD2 and for terminal deoxyribonucleotidyl transferase-mediated dUTP–digoxigenin nick end-labelling (TUNEL) staining of apoptosis. Apoptosis did not occur in any Leydig cells, but approximately 30% expressed GCR and 11β-HSD2. The number of GCR-positive cells was similar at all stages, but the number of 11β-HSD2-positive cells tended to be higher at Weeks 6 and 15. Steroid synthesis was also higher compared with Weeks 10 and 13. Apoptosis occurred in only a few germ cells. Nearly all germ cells were GCR positive at Weeks 10 and 13, when 11β-HSD2 was also increased. The total number of 11β-HSD2-positive germ cells was approximately 30%. Thus, elevated GCR expression coincided with the differentiation of gonocytes to spermatogonia and their migration to the basal lamina.
Cytoplasmic and nuclear determinants of the maternal-to-embryonic transition
Authors: Bettegowda Anilkumar , Lee Kyung-Bon , Smith George W.
Published: January 2008

Although improvements in culture systems have greatly enhanced in vitro embryo production, success rates under the best conditions are still far from ideal. The reasons for developmental arrest of the majority of in vitro produced embryos are unclear, but likely attributable, in part, to intrinsic and extrinsic influences on the cytoplasmic and/or nuclear environment of an oocyte and/or early embryo that impede normal progression through the maternal-to-embryonic transition. The maternal-to-embryonic transition is the time period during embryonic development spanning from fertilisation until when control of early embryogenesis changes from regulation by oocyte-derived factors to regulation by products of the embryonic genome. The products of numerous maternal effect genes transcribed and stored during oogenesis mediate this transition. Marked epigenetic changes to chromatin during this window of development significantly modulate embryonic gene expression. Depletion of maternal mRNA pools is also an obligatory event during the maternal-to-embryonic transition critical to subsequent development. An increased knowledge of the fundamental mechanisms and mediators of the maternal-to-embryonic transition is foundational to understanding the regulation of oocyte quality and future breakthroughs relevant to embryo production.
Insights and applications from sequencing the bovine genome
Authors: Adelson David L.
Published: January 2008

Humans have sought to improve/tailor cattle since their domestication a few thousand years ago. Up until the last 40–50 years, consistent genetic improvement of cattle was a hit or miss proposition. Recent progress has been more rapid, thanks to applications of quantitative genetics to breeding schemes. With the availability of the bovine genome sequence, genetic selection and on-farm management are likely to be revolutionised yet again. Genetic association studies that were previously impossible to carry out due to a lack of markers are now possible. In addition to improved genetic mapping of economic traits, the bovine genome sequence allows us to create a common context for genetic and physiological data, which will provide novel insights into gene regulation and function.
Commercialising genetically engineered animal biomedical products
Authors: Sullivan Eddie J. , Pommer Jerry , Robl James M.
Published: January 2008

Research over the past two decades has increased the quality and quantity of tools available to produce genetically engineered animals. The number of potentially viable biomedical products from genetically engineered animals is increasing. However, moving from cutting-edge research to development and commercialisation of a biomedical product that is useful and wanted by the public has significant challenges. Even early stage development of genetically engineered animal applications requires consideration of many steps, including quality assurance and quality control, risk management, gap analysis, founder animal establishment, cell banking, sourcing of animals and animal-derived material, animal facilities, product collection facilities and processing facilities. These steps are complicated and expensive. Biomedical applications of genetically engineered animals have had some recent successes and many applications are well into development. As researchers consider applications for their findings, having a realistic understanding of the steps involved in the development and commercialisation of a product, produced in genetically engineered animals, is useful in determining the risk of genetic modification to the animal v. the potential public benefit of the application.
110 COMPARATIVE ANALYSIS OF DNA AND HISTONE H3 METHYLATION REPROGRAMMING IN MOUSE, BOVINE, AND RABBIT ZYGOTES
Authors: Lepikhov K. , Zakhartchenko V. , Yang F. , Wrenzycki C. , Wolf E. , Walter J.
Published: January 2008

Active demethylation of paternal DNA in zygotes has been documented for many mammalian species, including mouse (Mayer et al. 2000 Nature 403, 501–505), rat (Zaitseva et al. 2007 Mol. Reprod. Dev. 74, 1255–1261), pig (Fulka et al. 2006 Histochem. Cell. Biol. 126, 213–217), Homo sapiens (Fulka et al. 2004 Reproduction 128, 703–708), and cow (Beaujean et al. 2004 Curr. Biol. 14, 266–267). The generality of this concept has been challenged by reports stating that there is no detectable genome-wide paternal DNA demethylation in rabbit (Shi et al. 2004 Biol. Reprod. 71, 340–347) and ovine (Beaujean et al. 2004 Curr. Biol. 14, 266–267), whereas others report partial evidence for the opposite (Zhang et al. 2005 Mol. Reprod. Dev. 72, 530–533). In order to compare the fate of DNA and histone H3 methylation (H3/K4triMe and H3/K9diMe), we performed studies on mouse, bovine, and rabbit zygotes using specific antibodies in an indirect immunofluorescence approach. We observed a similar distribution of these epigenetic modifications in maternal and paternal pronuclei of the zygote, indicating that the overall epigenetic reprogramming activities — including the DNA demethylation of the paternal pronucleus — are conserved between mammalian species. For all 3 species we found a clear asymmetry in mouse monoclonal antimethylcytosine (MeC) antibody signal intensities between paternal and maternal pronuclei at advanced stages, which suggests the presence of paternal DNA demethylation. To obtain additional evidence for the presence of DNA demethylation activity in rabbit zygotes, we examined 1-cell embryos after somatic cell nuclear transfer (SCNT) using rabbit fetal fibroblasts as nuclear donors, and we found a strong signal reduction in SCNT embryos 4 h after activation. For the majority of SCNT 1-cell embryos, we estimated at least a 4- to 6-fold decrease of MeC signal. Along with the similarities of DNA demethylation kinetics in rabbit, mouse, and bovine zygotes, we found a conserved distribution of H3/K4triMe and H3/K9diMe signals on maternal and paternal chromatin. In all 3 species, H3/K4triMe, which predominantly demarcate open chromatin, is present in both pronuclear chromatin, whereas H3/K9diMe, a hallmark of condensed chromatin, is strongly enriched in maternal pronuclear chromatin and undetectable in paternal chromatin. Furthermore, we observed a similar asymmetric compartmentalization of paternal and maternal chromosomes in early 2-cell rabbit and bovine embryos as monitored by H3/K9diMe, which marks maternally derived chromosomes. In summary, our data suggest that mechanisms of epigenetic reprogramming are conserved in mammalian species both on the level of DNA and chromatin methylation.
111 CHARACTERIZATION OF BOVINE TELOMERASE REVERSE TRANSCRIPTASE DURING PREIMPLANTATION EMBRYOGENESIS
Authors: Madan P. , King W. A. , Betts D. H.
Published: January 2008

Telomerase is a specialized reverse transcriptase that extends telomeric DNA of eukaryotic chromosomes and is composed of 2 essential subunits, the telomerase RNA component (TERC) and the telomerase reverse transcriptase (TERT). Together, this ribonucleoprotein complex is normally highly active in germ cells and stem/progenitor cells but not in normal somatic cells. In humans, this regulation of telomerase activity is primarily coordinated at the level of transcription of the TERT gene, whereas TERC is virtually ubiquitously expressed. Previous studies from our laboratory have detected telomerase activity in embryos from all stages of early bovine development. However, the regulation of the telomerase subunits remains poorly understood. Therefore, the objective of our study was to characterize the expression of bovine TERT (bTERT) during bovine preimplantation embryogenesis. UsingRT-PCR and immunofluorescence staining procedures (n = 20 embryos at timed stages of development; r = 3), we demonstrate that mRNA transcripts and protein for bTERT were detected in preimplantation bovine embryos from 1-cell to the blastocyst stage. The specificity of bTERT PCR products was confirmed by sequencing and demonstrated 94% sequence homology to the human hTERT cDNA sequence. In the immature oocyte, bTERT protein was localized within the germinal vesicle, and after 18–20 h of in vitro maturation, bTERT was observed as doublet foci co-localized with the condensed metaphase II meiotic stage chromosomes. Post-fertilization, the expression of bTERT was observed within the pronuclei. Through the initial cleavage stages, the expression of bTERT was variable, with some blastomeres showing punctuate staining and others exhibiting a uniform staining pattern. By the 8-16 cell stage, the embryos demonstrated a peri-nuclear presence of bTERT. However, in morula and blastocysts, bTERT was localized to the nuclei as demonstrated by co-localization with 42,6-diamidino-2-phenylindole staining. Based on this pattern of expression, it is tempting to speculate that bTERT could be playing an important role in regulating telomerase activity during early embryo development. The translocation of bTERT protein from the cytoplasm to the nucleus in morulae supports the telomere elongation event that is known to occur in mammalian embryos during the transition from the morula to blastocyst stages.
113 CHARACTERIZATION OF THE BOVINE EMBRYO-DERIVED CT-1 CELL LINE FOR STUDYING REGULATION OF TRANSCRIPTION FACTORS EXPRESSED WITHIN THE BOVINE TROPHECTODERM
Authors: Schiffmacher A. T. , Keefer C. L.
Published: January 2008

Cloned bovine embryos have been shown to display deviations in gene expression of trophectodermal (TE) lineage-specific transcription factors, including Cdx2, Errβ, Eomes, Mash2, and Hand1. Misregulation of these genes in the early TE has been implicated to play a causal role in abnormal placental formation and fetal loss. Because suboptimal in vitro culture conditions fail to support development beyond hatching, very little is known about regulation of peri-attachment bovine embryo development. Trophectodermal-derived bovine cell lines, such as the CT-1 cell line produced by Talbot and colleagues (Talbot et al. 2000 Biol. Reprod. 62, 235–247) could prove beneficial for understanding how regulatory factors govern early bovine TE development. The CT-1 cell line has been cultured continuously for over 2 years and appears morphologically similar to primary bovine TE outgrowths. Furthermore, these cells produce interferon τ, a cytokine unique to the early bovine TE. The objective of this study was to develop a gene expression profile of selected developmental genes that play a potential role in commitment to the TE fate, maintenance of multipotency, or differentiation into a binucleate phenotype. The CT-1 colonies were initially expanded on gamma-irradiated STO cells at 37°C and 5% CO2 and passaged weekly. Cells were cultured in DMEM supplemented with 10% fetal bovine serum and 1 mm sodium pyruvate and were passaged whenever colony edges touched. Cultures designated for RNA extraction and RT-PCR were then passaged into collagen-coated flasks or Cellbind® flasks (Corning, Lowell, MA, USA) at an average dilution of 1:4 for at least 6 feeder-free passages. Feeder-free culture at 37°C and 8.5% CO2 was optimal for adherence and growth. There were no observable differences in morphology, adherence, or growth rate between CT-1 cells grown on collagen film or a Cellbind® surface. The RT-PCR results indicate that the transcription factor Cdx2, which is homologous to the mouse master TE regulator, is abundantly expressed, whereas pluripotency specific Oct4 is weakly expressed. However, pluripotency specific transcription factors Nanog and Sox2 were undetectable. Transcription factors Eomes, Ets2, Errβ, and Id2, which may be required for proper bovine trophoblast elongation and developmental potential, were also expressed. Hand1 mRNA, a basic helix-loop-helix transcription factor that directs mouse trophoblast cells to differentiate into a giant cell phenotype, was also present and may play a role in binucleate cell formation. Together the data indicate that the CT-1 cell line can be utilized as a permissive cell line for studying transcriptional control of key TE regulatory factors that define the bovine TE lineage and allow better interpretation of gene expression data collected from assisted reproductive technology-derived embryos.
114 SPECIFIC AMINO ACIDS INFLUENCE LINEAGE DIFFERENTIATION IN MOUSE BLASTOCYSTS AND OUTGROWTHS
Authors: Sihota R. , Brooks S. , Tong C. , Cameron I. T. , Fleming T. P. , Eckert J. J.
Published: January 2008

Blastocyst biogenesis and cell lineage differentiation into inner cell mass and trophectoderm (TE) are highly regulated processes initiated during cleavage. Cell positioning and contact patterns are well-accepted broad extrinsic factors involved in regulating blastocyst formation; however, subtle changes in the chemical composition of culture media, similarly extrinsic, may exert significant consequences for differentiation. In this study, we have examined whether, when, and how the lack of branched chain amino acids impacts on blastocyst differentiation and TE development. Using superovulated MF1 mice, embryos were flushed at 50 (2 cell) or 75 (8 cell) h after hCG and cultured in mKSOM with 0.6% BSA and amino acids at uterine fluid concentrations (Porter et al. 2003 Pediatr. Res. 53, 46A) with (all) or without (–br) the branched-chain amino acids valine, leucine, and isoleucine. Blastocysts (60 or 36 h after culture onset) were differentially labeled using the TNBS-anti-DNP-complement method with propidium iodide and Hoechst, and cells were counted on z-series with overlays using Metamorph software. For outgrowths, blastocysts developed with all aa or –br from 8 cells for 36 h were placed into KSOM supplemented with 10% FCS and either all aa or –br and cultured for an additional 120 h, scored daily, and 4′,6-diamidino-2-phenylindole nuclei counts were made at 120 h. Lack of branched amino acids from the 2-cell stage onwards caused a significant increase in total blastocyst cells with predominantly higher TE numbers, whereas, when exposed to –br from the 8 cell stage onwards, the outcome was reversed (ANOVA; Table 1). Upon outgrowth, prior amino acid composition was relatively less influential in determining spreading pattern and rate over time compared to outgrowth amino acid conditions (ANOVA; Table 1). Our data indicate that lineage development in the blastocyst is sensitive to small changes in free amino acids available and responds differently according to exposure time and duration. Subsequent development predominantly depends upon outgrowth conditions, irrespective of earlier experiences, suggesting that a similar capability for adaptive changes in response to different outgrowth media is maintained. These findings may help understand developmental plasticity and consider dynamic and potential longer-term responses to minor culture changes.

Table 1. Blastocyst differentiation and outgrowth

Funding by DOHaD, Gerald Kerkut Trust, and NIH are gratefully acknowledged.
130 PREDICTION OF PARTHENOGENETIC DEVELOPMENTAL POTENTIAL BY POLAR BODY EXTRUSION AND FIRST CLEAVAGE ON IN VITRO MATURATION AND DEVELOPMENT OF PORCINE FOLLICULAR OOCYTES
Authors: Kim H. J. , Cho S. R. , Choe C. Y. , Choi S. H. , Son D. S. , Kim S. J. , Sang B. D. , Han M. H. , Ryu I. S. , Kim I. C. , Kim I. H. , Im K. S.
Published: January 2008

The objective of this study was to examine the selection effects of in vitro matured porcine follicular oocytes with polar body extrusion and early cleavage as a non-invasive marker to know the developmental competence in advance. Porcine oocytes matured for 48 h and then examined for polar body extrusion. The examined oocytes were matured for an additional 16–18 h, activated with 7% ethanol, and cultured in 5 µg mL–1 cytochalasin B for 5 h for diploid formation. The treated oocytes were examined for cleavage after 48 h and continued culturing for 5 days. Each treatment was replicated by 3–4 times. Oocytes of 21.9% (70/320) were discarded in morphological selection, and 32.1% (167/520) oocytes were discarded by failure of first polar body extrusion. The selected oocytes were matured and activated, and after 48 h, the cleavage rate was examined. In morphologically selected oocytes, 15.8% (30/190) were not cleaved, 52.6% (100/190) were normally cleaved (consisted of 2–7 cells), and 31.6% (60/190) were hyper-cleaved (consisted of 8 cells or more) at 48 h after activation. However, in the first polar body extruded oocytes, 7.1% (18/253) were not cleaved, 73.1% (185/253) were normally cleaved, and 19.8% (50/253) were hyper-cleaved. From the morphologically selected oocytes, 16.7% (10/60) were developed up to blastocyst stage from those in which cleavage selection was not performed and 31.7% (19/60) from those in which cleavage selection was performed. From the polar body extruded oocytes, 39.0% (39/100) were developed up to blastocyst stage from those in which cleavage selection was not performed and 49.0% (49/100) from those in which cleavage selection was performed. Cleavage was examined within 12 h interval after activation (0 = time of activation) up to 48 h. At 0–12, 12–24, 24–36, and 36–48 h intervals, 4.1% (9/220), 68.6% (151/220), 19.1% (42/220), and 2.3% (5/220) oocytes were cleaved, respectively, and 5.9% (13/220) oocytes were not cleaved at 48 h after activation. The cleaved embryos in each interval were cultured and developed up to blastocyst with 0 (0/9), 39.1 (59/151), 9.5 (4/42), and 0% (0/5), respectively. This result suggests that the polar body extruded and cleaved at 12–36 h embryo has higher developmental potential than the others.