bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of nitrogen incorporation on performance and bias temperature instability of metal oxide semiconductor field effect transistors with ultrathin high-k gate stacks
Authors: Liao J. C. , Fang Y. K. , Chen C. H. , Hou Y. T. , Hsu P. F. , Lin K. C. , Huang K. T. , Lee T. L. , Liang M. S.
Published: November 2008

This paper reports a comprehensive study on the influence of nitrogen incorporation on high-k (HK) device performance and reliability. Two approaches including dielectric nitrogen annealing and interfacial layer (IL) nitrogen annealing are investigated. It is found the HK nitrogen annealing is a better solution for the trade-off between mobility and inversion oxide thickness than IL annealing. The positive bias temperature instability characteristic is improved by HK annealing. However, the HK nitrogen annealing lowers the barrier of dielectric and thus results in an abnormally high leakage current.
Space-charge trap mediated conductance blockade in tunnel junctions with half-metallic electrodes
Authors: Feng J. F. , Kim T.-H. , Han X. F. , Zhang X.-G. , Wang Y. , Zou J. , Yu D. B. , Yan H. , Li A. P.
Published: November 2008

A conductance blockade effect has been observed in the magnetic tunnel junction consisting of La0.7Sr0.3MnO3 electrodes and a SrTiO3 barrier. The blockade effect is correlated with the space-charge trap states in the barrier. The blockade threshold eVB=128meV is significantly greater than Coulomb charging energy EC=11meV. The blockade can be lifted with a magnetic field, accompanied by a very large magnetoresistance up to 10 000%. The intriging blockade behavior is distinctly different from the conventional Coulomb blockade effect, showing a unique spin-dependent tunneling process mediated by the localized charge trap states.
Thermal coercivity mechanism in Fe nanoribbons and stripes
Authors: Garcia-Sanchez F. , Chubykalo-Fesenko O.
Published: November 2008

We investigate the influence of thermally activated process on coercivity values of long Fe nanostripes. By means of the Lagrangian multiplier technique and the micromagnetic approach, we evaluate energy barriers separating the two magnetization states of long Fe nanostripes, varying their width from 30to250nm. As the width of nanostripes decreases, the reversal time, evaluated through the Arrhenius–Neel law, becomes comparable to the measurement time scale (characteristic for typical magnetometer) for fields below the values obtained through zero-temperature micromagnetic approach. We found appreciable variation of the coercivity due to thermal activation for stripe widths below 100nm.
A comprehensive diagram to grow InAlN alloys by plasma-assisted molecular beam epitaxy
Authors: Fernández-Garrido S. , Gačević Ž. , Calleja E.
Published: November 2008

Indium incorporation and surface morphology of InAlN layers grown on (0001) GaN by plasma-assisted molecular beam epitaxy were investigated as a function of the impinging In flux and the substrate temperature in the 450–610 °C range. In incorporation was found to decrease with substrate temperature due to thermal decomposition of the growing layer, while for a given temperature it increased with the impinging In flux until stoichiometry was reached at the growth front. The InN losses during growth followed an Arrhenius behavior characterized by an activation energy of 2.0 eV. A growth diagram highly instrumental to identify optimum growth conditions was established.
An artificial molecular switch that mimics the visual pigment and completes its photocycle in picoseconds
Authors: Sinicropi Adalgisa , Martin Elena , Ryazantsev Mikhail , Helbing Jan , Briand Julien , Sharma Divya , Léonard Jérémie , Haacke Stefan , Cannizzo Andrea , Chergui Majed , Zanirato Vinicio , Fusi Stefania , Santoro Fabrizio , Basosi Riccardo , Ferré Nicolas , Olivucci Massimo
Published: November 2008

Single molecules that act as light-energy transducers (e.g., converting the energy of a photon into atomic-level mechanical motion) are examples of minimal molecular devices. Here, we focus on a molecular switch designed by merging a conformationally locked diarylidene skeleton with a retinal-like Schiff base and capable of mimicking, in solution, different aspects of the transduction of the visual pigment Rhodopsin. Complementary ab initio multiconfigurational quantum chemistry-based computations and time-resolved spectroscopy are used to follow the light-induced isomerization of the switch in methanol. The results show that, similar to rhodopsin, the isomerization occurs on a 0.3-ps time scale and is followed by <10-ps cooling and solvation. The entire (2-photon-powered) switch cycle was traced by following the evolution of its infrared spectrum. These measurements indicate that a full cycle can be completed within 20 ps.
Genome-wide screen of
Saccharomyces cerevisiae
null allele strains identifies genes involved in selenomethionine resistance
Authors: Bockhorn Jessica , Balar Bharvi , He Dongming , Seitomer Eden , Copeland Paul R. , Kinzy Terri Goss
Published: November 2008

Selenomethionine (SeMet) is a potentially toxic amino acid, and yet it is a valuable tool in the preparation of labeled proteins for multiwavelength anomalous dispersion or single-wavelength anomalous dispersion phasing in X-ray crystallography. The mechanism by which high levels of SeMet exhibits its toxic effects in eukaryotic cells is not fully understood. Attempts to use
Saccharomyces cerevisiae
for the preparation of fully substituted SeMet proteins for X-ray crystallography have been limited. A screen of the viable
S. cerevisiae
haploid null allele strain collection for resistance to SeMet was performed. Deletion of the
CYS3
gene encoding cystathionine gamma-lyase resulted in the highest resistance to SeMet. In addition, deletion of
SSN2
resulted in both increased resistance to SeMet as well as reduced levels of Cys3p. A methionine auxotrophic strain lacking
CYS3
was able to grow in media with SeMet as the only source of Met, achieving essentially 100% occupancy in total proteins. The
CYS3
deletion strain provides advantages for an easy and cost-effective method to prepare SeMet-substituted protein in yeast and perhaps other eukaryotic systems.
Binocular spatial induction for the perception of depth does not cross the midline
Authors: Hudson Todd E. , Matin Leonard , Li Wenxun
Published: November 2008

Although horizontal binocular retinal disparity between images in the two eyes resulting from their different views of the world has long been the centerpiece for understanding the unique characteristics of stereovision, it does not suffice to explain many binocular phenomena. Binocular depth contrast (BDC), the induction of an appearance of visual pitch in a centrally located line by pitched-from-vertical flanking lines, has particularly been the subject of a good deal of attention in this regard. In the present article, we show that BDC does not cross the median plane but is restricted to the side of the visual field containing a unilateral inducer. These results cannot be explained by the use of retinal disparity alone or in combination with any additional factors or processes previously suggested to account for stereovision. We present a two-channel three-stage neuromathematical model that accounts quantitatively for present and previous BDC results and also accounts for a large number of the most prominent features of binocular pitch perception: Stage 1 of the differencing channel obtains the difference between the retinal orientations of the images in the two eyes separately for the inducer and the test line; stage 1 of the summing channel obtains the corresponding sums. Signals from inducer and test stimuli are combined linearly in each channel in stage 2, and in stage 3 the outputs from the two channels are combined along with a bias signal from the body-referenced mechanism to yield θ′, the model's prediction for the perception of pitch.
La adquisición del pretérito imperfecto en situación de inmersión
Authors: Martínez Arbelaiz Asunción , Rodríguez Isabel Pereira
Published: November 2008

Este estudio investiga en qué medida el estudio de la lengua meta en situación de inmersión favorece el desarrollo de la competencia gramatical de los alumnos. Investigaciones anteriores han encontrado un efecto positivo del estudio en el extranjero particularmente sobre la fluidez oral (Freed 1995; Segalowiz y Freed 2004), pero no hay resultados concluyentes de su efecto sobre la corrección gramatical. El presente trabajo compara los datos escritos recogidos sobre el uso del pretérito imperfecto de alumnos anglohablantes de español en un contexto de inmersión con el de alumnos que estudiaban español en una universidad norteamericana. El primer grupo mostró un uso más extenso y correcto de este tiempo, sobre todo en lo que a su función descriptiva se refiere. En conclusión, los resultados permiten afirmar que la corrección gramatical de los alumnos en situación de inmersión mejoró al menos en lo que al uso del pretérito imperfecto se refiere.
Reflexiones metalingüísticas acerca del voseo costarricense
Authors: Thomas Juan Antonio
Published: November 2008

Este trabajo describe los resultados de una encuesta metalingüística completada por veinte costarricenses sobre el uso del pronombre de tratamiento (vos, tú o usted) en varios contextos sociales. En esta investigación, se ha valido del programa S.P.S.S. para cruzar las respuestas del uso pronominal con las variables sociales de género, estado civil, edad, ingresos, estudios y provincia de nacimiento. La forma de tratamiento no-marcada en todas las situaciones estudiadas es el pronombre usted, tanto en ámbitos de solidaridad (familiaridad, amistad y confianza) como en los de distanciamiento y de poder. Los encuestados indican el empleo del vos, siempre la forma marcada y de uso minoritario, en ciertas relaciones de confianza y amistad, por ejemplo, con miembros de la familia, amigos y, a veces, con compañeros de trabajo. La prueba chi-cuadrado de Pearson muestra una dependencia significativa entre el empleo del vos en contextos de confianza y las variables independientes de género y edad. El uso costarricense del vos no equivale ni al vos de otras regiones voseantes ni tampoco al tú. El tratamiento con tú, pronombre tradicionalmente ajeno al sistema costarricense, aparece con escasa frecuencia entre las respuestas.
Their language, our Spanish
Authors: Schwartz Adam
Published: November 2008

This study exposes ‘gringo Spanish’ as a discursive site for the reproduction of privilege, racism and social order in White public spaces. I begin my arguments by exploring Whiteness, doing so by unpacking what I term ‘Gringoism’, which involves the active celebration of a White, monolingual (un)consciousness through particular linguistic and cultural performance. Brief analysis of one particular educational text (Harvey 1990/2003) supports greater discussions of indexicality, intersubjectivity, the elevation of Whiteness and discourses of ‘making sense’ of Spanish-speaking Others. The study closes with implications for the field of Mexican American studies, which in turn offers considerations for scholars studying Spanish within greater educational, anthropological and socio-cultural contexts.
Natural versus elicited data in cross-cultural speech act realisation
Authors: Bou-Franch Patricia , Lorenzo-Dus Nuria
Published: November 2008

This paper explicitly addresses the ‘elicited versus natural data debate’ in cross-cultural speech act realisation research through critical discussion of an empirical study of comparable request sequences by Spanish and British undergraduates to one of their lecturers. Elicited (discourse completion tests) and natural data (unsolicited emails) were used and, not unexpectedly, produced significantly different results for each language community. That these differences related to crucial aspects of the interpretation and performance of requesting behaviour — such as organisation, density and politeness choices — leads us to argue that the goals of cross-cultural speech act realisation research can be best pursued through the analysis of natural data. The latter, however, should not be regarded as some methodological panacea but needs to be exposed to the same intellectual rigour that elicited data have been.
Counting what counts
Authors: Grbić Nadja , Pöllabauer Sonja
Published: November 2008

This paper presents the results of a study on research on spoken and signed language community interpreting (CI) in German-speaking countries (Austria, Germany, German-speaking regions of Switzerland). A set of different scientometric, network analytical and text linguistic (keyword analysis, title word analysis, co-occurrence analysis) methodological tools is used to investigate this specific field of research. The paper is a follow-up to a first brief introductory paper on that topic (Grbić and Pöllabauer 2006a) and presents an in-depth analysis of the subject. The corpus of the study includes 595 publications on research into spoken and signed CI in German-speaking countries, which were published between 1979 and 2006. It was compiled on the basis of a comprehensive search of the literature. The study focuses, among other aspects, on the types of documents published in that field of research (with a specific focus on journal articles, collective volumes, papers in collective volumes, graduation and doctoral theses) and the nature of the publications, the overall growth rates of publications on that field, the most common languages of publication, the disciplinary affiliation of the authors, the agents (people, institutions) involved in researching CI as well as the networks of authors and co-authorships, and the topics touched upon in research on CI and the most common co-occurrences of topics.
Making Models Count
Authors: Alexandrova Anna
Published: November 2008

What sort of claims do scientific models make and how do these claims then underwrite empirical successes such as explanations and reliable policy interventions? In this paper I propose answers to these questions for the class of models used throughout the social and biological sciences, namely idealized deductive ones with a causal interpretation. I argue that the two main existing accounts misrepresent how these models are actually used, and propose a new account.
Natural Selection as a Mechanism
Authors: Barros D. Benjamin
Published: November 2008

Skipper and Millstein (2005) argued that existing conceptions of mechanisms failed to “get at” natural selection but left open the possibility that a refined conception of mechanisms could resolve the problems that they identified. I respond to Skipper and Millstein, and argue that while many of their points have merit, their objections can be overcome and that natural selection can be characterized as a mechanism. In making this argument, I discuss the role of regularity in mechanisms, and develop an account of stochastic (i.e., probabilistic) mechanisms. Explaining the phenomenon of adaptation through the mechanism of natural selection illustrates the power and flexibility of using mechanistic strategies to explain natural phenomena.
Quantitation of LMW‐GS to HMW‐GS Ratio in Wheat Flours
Authors: Cinco‐Moroyoqui Francisco J. , MacRitchie Finlay
Published: November 2008

A comparison was made of methods for measuring the LMW/HMW glutenin subunit (GS) ratio for glutenin. A set of near‐isogenic wheat lines with the number of HMW‐GS varying from 0 to 5 was utilized to provide a wide range of LMW/HMW‐GS. Glutenin preparations were obtained from ground whole meal after solubilization of monomeric proteins by dimethyl sulfoxide (DMSO) or 50% propanol or by fraction collection from a preparative SE‐HPLC column. Analyses were made on the reduced glutenin from each of the three preparations by RP‐HPLC, SE‐HPLC, and SDS‐PAGE. Both solvents, DMSO and 50% propanol, extracted appreciable amounts of polymeric protein, thus casting some doubts on the accuracy of the determinations. This problem was largely avoided when the polymeric fraction was collected from the eluate of a total glutenin extract run on a preparative SE‐HPLC column. Less glutenin was removed by the two solvents for lines with a greater number of HMW‐GS or with strength‐associated HMW‐GS 5+10 coded by the 1D chromosome. Collection of the polymeric protein in SE‐HPLC, followed by separation of the glutenin subunits in RP‐HPLC, was the best method for quantitating the LMW/HMW‐GS ratio. SE‐HPLC gave a clear separation of the two groups of subunits as well as HMW albumins. RP‐HPLC has the potential advantage of being able to quantitate individual subunits.
Minimal residual disease detection in childhood acute lymphoblastic leukaemia patients at multiple time‐points reveals high levels of concordance between molecular and immunophenotypic approaches
Authors: Ryan Jacqueline , Quinn Fiona , Meunier Armelle , Boublikova Ludmila , Crampe Mireille , Tewari Prerna , O’Marcaigh Aengus , Stallings Ray , Neat Michael , O’Meara Ann , Breatnach Fin , McCann Shaun , Browne Paul , Smith Owen , Lawler Mark
Published: November 2008

In this single centre study of childhood acute lymphoblastic leukaemia (ALL) patients treated on the Medical Research Council UKALL 97/99 protocols, it was determined that minimal residual disease (MRD) detected by real time quantitative polymerase chain reaction (RQ‐PCR) and 3‐colour flow cytometry (FC) displayed high levels of qualitative concordance when evaluated at multiple time‐points during treatment (93·38%), and a combined use of both approaches allowed a multi time‐point evaluation of MRD kinetics for 90% (53/59) of the initial cohort. At diagnosis, MRD markers with sensitivity of at least 0·01% were identified by RQ‐PCR detection of fusion gene transcripts,IGH/TRGrearrangements, and FC. Using a combined RQ‐PCR and FC approach, the evaluation of 367 follow‐up BM samples revealed that the detection of MRD >1% at Day 15 (P = 0·04), >0·01% at the end of induction (P = 0·02), >0·01% at the end of consolidation (P = 0·01), >0·01% prior to the first delayed intensification (P = 0·01), and >0·1% prior to the second delayed intensification and continued maintenance (P = 0·001) were all associated with relapse and, based on early time‐points (end of induction and consolidation) a significant log‐rank trend (P = 0·0091) was noted between survival curves for patients stratified into high, intermediate and low‐risk MRD groups.
Non‐working nurses in Japan: estimated size and its age‐cohort characteristics
Authors: Nakata Yoshifumi , Miyazaki Satoru
Published: November 2008

Aims and objectives.  This paper aims to forecast the total number of non‐working nursing staff in Japan both overall and in terms of separate age groups for assistant nurses and fully qualified nurses. This also examines policy implications of those forecasts.

Background.  Although the existence of around 550,000 of non‐working nursing staff has been announced, the actual number of non‐working nurses is not so clear that we might make errors in making policy to meet nurse workforce demand and supply in Japan.

Design and method.  Estimations by integrating various data on the quantitative characteristics of non‐working nursing staff were carried out. Considering the length and the type of education or training in referred four nursing positions; registered nurses, assistant nurses, public health nurses and midwives, we first estimated the number of students who completed a full course. And then multiplying by the ratio for gender and age classifications at the time of entry into courses, the number of those who obtained licenses was estimated.

Results.  The number of non‐working nurses was estimated at 100,000 higher than those in 2005 by government. Looking at age group, it is also possible to see a strong reflection of an employment pattern that follows the life cycle of female workers. Further analysis of life cycle effects and cohort effects proved the effect of life cycles even when subtracting the differences between the working behaviours of different generations.

Conclusions.  Our findings strongly suggest the need to provide an urgent policy that workplace conditions can be created in which a balance between work and family is achievable. Moreover, to empower clinical activity, we also believe there is an urgent need to reexamine the overall career vision for assistant nurses including in terms of compensation.

Relevance to clinical practice.  Our findings strongly suggests that consideration for work‐life balance of nursing staff; particularly, female staff is all the more important to provide a stable quality care.
Real‐time quantitative polymerase chain reaction (qPCR) analysis with fluorescence resonance energy transfer (FRET) probes reveals differential expression of the four ERBB4 juxtamembrane region variants between medulloblastoma and pilocytic astrocytoma
Authors: Zeng N. , Liu L. , McCabe M. G. , Jones D. T. W. , Ichimura K. , Collins V. P.
Published: November 2008

Aims: We report a comparative study on the mRNA expression of ErbB receptor tyrosine kinases, and in particular ERBB4 transcript variants, in two common paediatric brain tumours: medulloblastoma (MB) and pilocytic astrocytoma (PA). Methods: While the conventional real‐time quantitative polymerase chain reaction was used to measure the expression of ERRBs and ErbB4‐processing protease genes, the LightCycler fluorescence resonance energy transfer probes were specifically designed to investigate all of the known ERBB4 juxtamembrane (JM) and cytoplasmic transcript variants. Results: The overall expression of ERBBs suggests that ErbB2/ErbB4 heterodimers and ErbB4 homodimers may be major functional units of the ErbBs in MB, while ErbB2/ErbB3 heterodimers may play a more prominent role in addition to ErbB4‐containing dimers in PA. Different expression patterns of ERBB4 JM transcripts in MB, PA and normal brain were observed. The JM‐d variant was only detected in MBs, while JM‐c was present in MB and PA but was not identified in normal brain. The expression of cleavable ERBB4 transcript variants was elevated in PAs and MBs compared with normal brain, while mRNA levels of ErbB4‐processing proteases were similar in both tumour types and normal brain. This suggests that proteolytic cleavage of ErbB4 may be more common in MB and PA, which leads to signalling events divergent from those in normal brain. Conclusion: Taken together, these results suggest that ErbB4 processing and function may be altered in brain tumours, such as MB and PA, via differential expression of JM transcript variants.
Management of pulmonary tuberculosis in Tajikistan: which factors determine hospitalization?
Authors: Thierfelder Clara , Makowiecka Krystyna , Vinichenko Tatyana , Ayé Raffel , Edwards Phil , Wyss Kaspar
Published: November 2008

Objective  To assess predictors for tuberculosis hospitalization and treatment outcome in Tajikistan.

Methods  Stratified, single stage cluster sample survey of 1495 adult patients with pulmonary TB during 2 calendar years (2005–2006) from the registries of 10 TB centres chosen by simple random sampling. The primary outcome was referral to hospital. Logistic regression was conducted to test associations with the study outcome using linearization and a variance formula.

Results  Prevalence of hospitalization for tuberculosis was 58%. The odds of patients with smear‐positive tuberculosis being referred were three times those of smear‐negative patients [OR 2.99 (95% CI 1.81–4.96)]. Other predictors for hospitalization were the availability of TB hospital beds within the same district [OR 2.15 (95% CI 1.22–3.76)] and male gender [OR 1.46 (95% CI 1.07–2.48)]. The overall treatment success was 80%.

Conclusions  Hospitalization of patients with pulmonary tuberculosis was determined by positive sputum smear, supply of hospital beds, and gender. Reducing hospitalization with support of national guidelines is not expected to have a negative impact on treatment outcome and spread of disease, but could lead to improved efficiency and effectives of health service delivery for pulmonary tuberculosis in Tajikistan.
Does a ‘reverse’ atopic march exist?
Authors: Barberio G. , Pajno G. B. , Vita D. , Caminiti L. , Canonica G. W. , Passalacqua G.
Published: November 2008

The classical description of the atopic march usually refers to the progression from atopic dermatitis towards asthma, but this pathway has been questioned. We assessed in a prospective observation the possible onset of atopic dermatitis in children with asthma alone at baseline, and evaluated retrospectively their characteristics. Seven hundred and forty‐five children (360 male, 6–9 years of age) with asthma alone, without food allergy or atopic dermatitis, were followed‐up with regular visits for 9 years. 692 children completed the 9‐year observation, and 20% of them were found to have developed atopic dermatitis at 9 years. Comparing retrospectively the children who developed AD with the remaining, no significant difference existed at baseline concerning the demographic characteristics and family history. There was a significantly higher proportion ( χ2 = 0.01) of subjects with single sensitization to mites and a significantly lower proportion of polysensitized subjects ( χ2 = 0.01) within the children who developed AD. Sensitization to foods appeared in 9% of children who developed AD and in 3.8% in the other children (NS). According to these observations, the development of a particular allergic disease does not necessarily follow the classical paradigm of the atopic march.
Corticosteroid enhances TNF‐α‐mediated leukocyte adhesion to pulmonary microvascular endothelial cells
Authors: Matsuda A. , Orihara K. , Fukuda S. , Fujinaga H. , Matsumoto K. , Saito H.
Published: November 2008

Background:  Some severe asthma patients are characterized by elevated levels of tumor necrosis factor alpha (TNF‐α) and neutrophilic inflammation in the airways. Although such phenotypic changes in asthma might contribute to corticosteroid refractoriness, the role of TNF‐α in the process remains unclear. TNF‐α exerts its biological effects mainly by acting on the vascular endothelium, and thereby upregulates leukocyte recruitment into inflamed tissues. The aim of this study was to investigate the effects of dexamethasone (DEX) on the TNF‐α‐mediated responses of human microvascular endothelial cells from lung blood vessels (HMVEC‐LBl) in vitro.

Methods:  HMVEC‐LBl were cultured with TNF‐α in the presence and absence of DEX. The effects of DEX on various TNF‐α‐mediated responses, such as the expressions of chemokines and cellular adhesion molecules, leukocyte adhesion were determined.

Results:  TNF‐α significantly induced growth‐related oncogene alpha (GRO‐α), interleukin 8 (IL‐8), regulated on activation, normal T‐cell expressed and secreted (RANTES) and interferon‐inducible protein 10 (IP‐10) productions and cell surface expressions of intracellular adhesion molecule 1 (ICAM‐1) and vascular cell adhesion molecule 1 (VCAM‐1) on HMVEC‐LBl. TNF‐α‐induced GRO‐α and IL‐8 were slightly attenuated by DEX treatment (reaches to 89% and 79%, respectively), whereas expressions of IP‐10, ICAM‐1 and VCAM‐1 were significantly enhanced by the same treatment (up to 172%, 152% and 139%, respectively). Correspondingly, in vitro adhesion of eosinophils and neutrophils to TNF‐α‐treated HMVEC‐LBl were significantly enhanced by DEX.

Conclusions:  Some proinflammatory effects of DEX, a corticosteroid, were found in TNF‐α‐mediated in vitro reactions of pulmonary microvascular endothelial cells, i.e. chemokine productions and leukocyte adhesion. These in vitro results may explain, at least in part, the corticosteroid refractoriness accompanied by a marked increase in TNF‐α production that is seen in severe asthmatic patients.
Human xenoreactive natural antibodies of the IgM isotype activate pig endothelial cells
Authors: Vanhove Bernard , de Martin Rainer , Lipp Joachim , Bach Fritz H.
Published: November 2008

Abstract: Preformed, xenoreactive natural antibodies (XNA) and complement (C) are involved in the initiation of vascular rejection of organs transplanted between discordant species, presumably by stimulating donor organ endothelial cells (EC). Although C is known to play a role in the activation of EC, it has not been clear whether the antibodies serve only to anchor the initial components of C, and thus permit the C cascade to proceed, or whether the antibodies themselves deliver a signal to the EC. We have tested affinity‐purified human IgM containing XNA (IgM‐XNA) for its ability to stimulate in vitro the up‐regulation of genes in pig EC. Northern blot analysis shows that IgM, which contains XNA, stimulates mRNA accumulation for certain genes (including IL‐8, PAI‐1, and ECI‐7, a new gene that we have found is associated with EC activation), but not others known to be up‐regulated in response to TNF, IL‐1 or LPS. Our results show that XNA provide a signal to EC, and thus may themselves participate in activation of EC and consequent vascular rejection.
Characterization of xenoreactive natural secreting cells in rats
Authors: Scares Miguel , van Beneden Ronald , Havaux Xavier , Van der Werf Wlllem , Bach Fritz H. , Latinne Dominique , Bazin Hervé
Published: November 2008

Abstract: IgM xenoreactive natural antibodies (XNA) and the activation of complement are thought to be the main components involved in the hyperacute rejection (HAR) of discordant xenografts. Nevertheless few studies have focused on the B cell population responsible for the production of XNA. Using the guinea pig to rat discordant xenograft model we have developed a xenoreactive ELISA‐spot technique allowing the specific detection of XNA secreting cells in rats. In order to detect rat XNA‐secreting cells, guinea pig platelet membrane extracts, which have been shown to share major xenoantigens as recognized by XNA, with endothelial cells, were used as targets for rat XNA. Adult LOU/C rats lymphocytes from spleen, mesenteric lymph nodes, Peyer's patches, bone marrow, and the peritoneal cavity were used as source of XNA secreting cells. The number of IgM, IgG2a, Ig k light chain XNA, and IgM XNA secreting cells was measured using standard and xenoreactive ELISA‐spot techniques respectively. Data presented here show that IgM XNA secreting cells are almost exclusively located in the spleen. Moreover, IgM XNA secreting cells represent around 0.0001% of spleen lymphocytes corresponding to 0.1% of the IgM secreting cells in the spleen. Although circulating IgG2a XNA are detectable, by cellular ELISA, in normal LOU/C rats, IgG2a secreting cells were not found in any of the cell suspensions analyzed. In contrast, Ig k light chain XNA were found in the spleen, mesenteric lymph nodes, and the bone marrow but not in the peritoneal cavity. Taken together these results suggest that extremely low numbers of secreting cells producing isotypes other than IgM and IgG2a might exist in different rat organs but are not detectable using the xenoreactive ELISA‐spot technique. In conclusion, our data show that only 0.0001% of spleen lymphocytes were found to be IgM XNA secreting cells. Moreover this IgM XNA secreting cells population is located almost exclusively in the spleen further illustrating the role of the spleen in the production of XNA.
Pig‐to‐human xenotransplantation: The expression of Galα(l–3)Gal epitopes on pig islet cells
Authors: McKenzie Ian F.C. , Xing Pei‐Xiang , Sandrin Mauro S. , Koulmanda Maria , Mandel Tom E.
Published: November 2008

Abstract: Previous histological studies of porcine tissues using the Galα(l–3)Gal specific lectin, IB4‐biotin, and an immunoperoxidase technique demonstrated the widespread distribution of Galα(l–3)Gal in pigs—particularly in the endothelium of all vessels and in the parenchyma of liver and kidney. An exception was the endocrine (islets) and exocrine tissue of the pig pancreas—adult islets did not express Galα(l–3)Gal and apart from ducts, and the exocrine pancreas was also nonreactive. Because of the potential use of islet xenotransplantation for the treatment of diabetes, a more extensive study was undertaken of fetal pancreas and of cultured islet cell clusters. Like the adult pancreas, islets from fetuses at term or earlier, essentially did not express Galα(l–3)Gal; however, during culture, under a variety of conditions, they became strongly reactive with IB4 and expressed large amounts of Galα(l–3)Gal. Staining for pancreatic hormones (insulin, glucagon, and somatostatin) demonstrated that true islets were being examined, although double staining for insulin and Galα(l,3)Gal indicated that cells secreting insulin were not Galα(l–3)Gal positive. The origin of the Galα(l–3)Gal+ cells is not apparent, nor is whether they are precursors of hormone secreting cells. It was of interest that, after transplantation to nude mice and allowing for maturation, the islets resembled the adult phenotype and were Galα(l–3)Gal negative. The implications of the findings are not clear but indicate that some cells in the cultured fetal islet (other than insulin secreting cells) could be the target of antibody mediated destruction.
Long‐term culture, low‐temperature culture, and hyperoxic culture do not prolong fish‐to‐mouse islet xenograft survival
Authors: Wright James R. , Kearns Heather
Published: November 2008

Abstract: Macroscopic, anatomically discrete islets called Brockmann bodies (BB) were harvested from tilapia with microscissors and then cultured under various conditions known to prolong islet allograft survival. BBs were cultured in 95% air/5% CO2 at 37°C either overnight (groups 1 and 2) or for 1 week (group 3); in 95% O2/5% CO2 at 37°C for 1 week (group 4), or in 95% air/5% CO2 at 24°C for 1 week (groups 5 and 6). Viability and function of cultured islets was confirmed by fluorescein diacetate/ethidium bromide staining and by transplantation under the left renal capsules of streptozotocin‐diabetic balb/c mice. Recipient mice in groups 2 and 6 received CsA (50 mg/kg/d p.o.) × 4 days. All recipient mice became normoglycemic posttransplant. Mean graft survival times (± S.D.) for groups 1, 2, 3, 4, 5, and 6 were 7.6 (± 1.1), 6.2 (± 1.5), 6.4 (± 0.79), 8.2 (± 2.3), 7.0 (± 0.71), and 6.2 (± 0.45) days, respectively. Rejection (i.e., nonfasting plasma glucose levels > 200 mg/dl) was confirmed histologically in all instances; rejection was characterized by infiltrates composed of mononuclear cells, plasma cells, and eosinophils. In our study, neither short‐term CsA nor any of the culture protocols significantly prolonged discordant fish‐to‐mouse islet xenograft survival.
Sheep lung as xenograft oxygenator of human blood: An ex vivo study
Authors: Riquet M. , LePimpec‐Barthes F. , Waldmann T. , Nataf P. , Cabrol C. , Pavie A. , Eme D. , Gandjbakhch I. , Briere J. , Douguet D. , Zelter M.
Published: November 2008

Abstract: In order to study whether sheep lung could be used as a suitable oxygenator for human blood, the left lungs of two groups of five sheep were used in an “isolated perfused working lung model system.” A desaturator was inserted in the circuit and the lung was ventilated with ambient air. The lung was perfused in group 1 with heparinated autologous sheep blood and in group 2 with washed human erythrocytes suspended in buffered gelatin. Blood oxygenation as well as hemodynamics and airway parameters followed similar time course in both groups.
Functional cooperation of xenoproteins after hamster‐to‐rat liver transplantation: With particular reference to hamster C3 and secretory component for rat IgA
Authors: Celli S. , Valdivia L.A. , Fung J.J. , Pan F. , Tsugita M. , Starzl T.E. , Kelly R.H. , Demetris A.J. , Rao A.S.
Published: November 2008

Abstract: Long‐term survival after hamster‐to‐rat liver xenotransplantation has provided the opportunity to study the posttransplantation source of major serum proteins and the functional consequences of several different receptor‐ligand interactions, where one or the other is a xenogeneic protein. We report here that serum albumin, α‐1‐antitrypsin, complement component 3, and other acute phase reactants switch from recipient to donor origin during the first week after transplantation while serum immunoglobulins remain largely that of recipient. Despite the disparate source of complement (hamster) and immunoglobulins (rat), these two proteins were able to cooperate effectively to produce lysis of sheep red blood cells. Moreover, rat IgA was successfully processed by hamster hepatocytes and biliary epithelial cells, being present in the bile of successful liver xenograft recipients within one day after transplantation. The ability of these liver xenograft recipients to survive long‐term in conventional and viral‐free animal facilities without grossly obvious morbidity or unusual susceptibility to stress, suggests that xenogeneic proteins are able to successfully interact with several different physiologic I systems in the hamster‐to‐rat combination.
Rat‐SCID chimeras: Functional characteristics of the immune system of SCID mice after transplantation of rat fetal hematopoietic cells
Authors: Ninova Dora I. , Krom Ruud A.F. , Wettstein Peter J.
Published: November 2008

Abstract: It has been demonstrated that allogeneic and xenogeneic lymphocytes can survive and expand in severe combined immunodeficiency (SCID) mice, but the T‐cell function of the chimeras has not always been tested. The aim of this study was to develop a rat‐SCID xenogeneic chimera and to examine the T cell response against RT1‐incompatible rat cells. Fetal liver cells (FLC) from Lewis (LEW) rats were injected i.v. into irradiated C.B‐17‐scid (SCID) mice at a dose of 4×107 cells/mouse. After 4 weeks, FACS analysis of peripheral blood lymphocytes (PBL) with monoclonal antibodies specific for rat lymphocyte subpopulations showed full reconstitution. The mice carried 6.2(±1.6)×106 PBL/ml and 92.5 (±39.5)×106 cells in the spleen. PBL, spleen, and lymph nodes showed distribution of CD4, CD8, and RT1 rat cellular markers similar to that observed in normal rats. Spleen cells from rat‐SCID chimeras demonstrated normal proliferative T cell responses to Concanavalin A. Chimeras were primed i.p. with 107 Brown Norway (BN) and ACI rat spleen cells, and the responder spleen cells of these primed chimeras showed specific proliferative responses in mixed lymphocyte culture (MLC) against BN and ACI stimulator lymphoid cells, respectively. Specific proliferative responses of rat‐SCID chimeras were higher against ACI than BN stimulators. These MLCs also expanded cytolytic T lymphocytes that lysed 51Cr labeled BN and ACI targets at levels up to 50–90%, respectively. In conclusion, rat FLC injected into SCID mice differentiate and repopulate the immune system as well as function in generating alloantigen‐specific cytolytic and helper T cells.
Identification of swine and primate cellular adhesion molecules (CAM) using mouse anti‐human monoclonal antibodies
Authors: Kumagai‐Braesch Makiko , Schacter Bernioe , Yan Zengmin , Michaelson James , Arn Scott , Smith Mary , White‐Scharf Mary , Monroy Rodney , Sachs David H. , Kurnick James T.
Published: November 2008

Abstract: A series of adhesion molecules of swine and Cynomolgus monkeys were identified by screening for cross‐reactivity with a panel of monoclonal murine anti‐human adhesion molecule antibodies obtained from the 5th International Workshop and Conference on Human Leukocyte Differentiation Antigens (Boston, MA, USA, 1993). Of 162 antibodies tested, 25 were found that cross‐react significantly with swine cells, while 67 were found to react strongly with cells of Cynomolgus monkeys. Cross reactivities to swine were found with antibodies to CD 18 (β2 integrin), CD29 (β1 integrin), β7 integrin, CD49d (α4 integrin) CD49b(α2 integrin), and to a lesser extent to CD62p(P‐selectin), CD62L(L‐selectin), CD102(ICAM‐2), CD11b, and CD49c (α3 integrin). Cross‐reactivities to primate cells also included CD18, CD29, CD49d, and CD49b. In addition, reactivities to Cynomolgus monkey cells were detected with antibodies to CD11 (a, b, and c), CD31, CD44, CD49e, CD49f, CD50, CD54, CD56, CD62p, CD 102 and CD56. The tissue distribution and molecular weight of the swine antigens are similar to their human counterparts. These findings provide a spectrum of monoclonal antibodies that react with shared epitopes on homologous adhesion molecules of human, swine, and monkey cells, thus facilitating study of the role of these molecules in the immunobiology of monkeys and swine. These reagents may be useful to dissect the role of adhesion molecules in both alio‐ and xenoreactivity.
Advantages of combined fetal and adult porcine islets as donor tissue for transplantation
Authors: Mullen Yoko
Published: November 2008

Abstract: The molecular similarity between human and porcine insulin is the primary reason for selecting the pig as a donor for islet xenotransplantation in order to treat type I diabetes. Porcine islets can be prepared from adult, newborn, or fetal pigs. However, each of these islet types possesses advantages and disadvantages due to their anatomical, developmental, and physiological characteristics. We have evaluated both adult and fetal porcine islets for their ability to reverse diabetes using an allograft model. Based on our accumulated data, we recommend transplantation of combined adult and fetal porcine islets as a prospective approach for pig to man islet xenotransplantation. The advantages of combined adult and fetal islet transplantation are as follows: 1) Adult porcine islets can reverse hyperglycemia soon after transplantation; 2) well controlled blood glucose at the critical developmental stage of fetal islets will provide the time and environment necessary to achieve the optimal proliferation, growth and maturation of fetal β cells; 3) after 2 to 3 months, fetal islets will functionally mature and begin to share the insulin‐producing load previously carried by adult islets, while new islets will continuously emerge and proliferate from stem cells; and 4) islets from fetal pigs will subsequently play a primary role in controlling hyperglycemia, and provide long‐lasting insulin independence.
Cryopreservation, transplantation, and susceptibility to diabetogenic agents of fetal porcine proislets
Authors: Bretzel Reinhard G. , Liu Xuemei , Hering Bernhard J. , Brendel Mathias , Federlin Konrad
Published: November 2008

Abstract: This study reports the morphology and in vitro function of fetal porcine proislets (FPP) after cryopreservation or culture and the in vivo effects of frozen‐thawed FPP in comparison to cultured FPP on the glucose metabolism after transplantation into nude mice rendered diabetic by streptozotocin (STZ). Furthermore, the morphology and the in vitro function of removed grafts is examined in an in vitro:ex vivo model and the in vitro and in vivo effects of FPP of the diabetogenic substance, STZ, is assessed. The data demonstrate that cryopreservation has no adverse effects on the morphology and in vitro function of FPP when compared to cultured FPP. Frozen‐thawed FPP are equally effective to normalize blood glucose levels in nude mice rendered diabetic by streptozotocin. Histological and in vitro:ex vivo examination of the removed graft revealed that the extent of differentiation and proliferation in vivo of cryopreserved FPP is comparable with that of cultured FPP. Streptozotocin is not toxic (diabetogenic) to FPP, neither in vitro nor in vivo. We conclude that cryopreserved fetal porcine proislets, easily yielded and pooled from pregnant sows bred in a microbiologically controlled environment, may be a potential source for future xenotransplantation in Type 1 diabetic humans.
Antisense inhibition of pig α1,3galactosyl‐transferase leads to a reduction in expression of the major target for human natural antibodies on pig vascular endothelial cells
Authors: Strahan Karen M. , Preece Andrew F. , Xu Yuanxin , Gustafsson Kenth
Published: November 2008

Abstract: The expression of epitopes on pig cells for human natural antibodies (NAb) currently constitutes a major barrier to the use of pig organs and tissues in clinical transplantation. This is of particular significance to vascularized organs where the presence of carbohydrate antigens invariably leads to a hyperacute rejection when exposed to human blood or serum. It has been strongly suggested that the major antigen in this context consists of a terminal Galα1,3Galβ1,4GlcNAc trisaccharide. We have previously proposed that decreased expression of this epitope for human NAb may lead to elimination of hyperacute rejection. We have now used mRNA targeted antisense oligonucleotides to decrease the expression of the α1,3galactosyltransferase directing the terminal synthesis of this epitope on pig vascular endothelial cells. This mRNA antisense targeting leads to a decreased expression of the Galα1,3Galβ1,4GlcNAc structure as detected by epitope specific lectin. Moreover, a very similar reduction in mean fluorescence was seen when staining the same cells with human Galα1,3Galα1,4GlcNAc‐specific IgM NAb. We feel these findings constitute an important step in the process of providing conclusive evidence that reduction of or complete elimination of this epitope will overcome the hyperacute response in this species combination. In addition, such pig tissues may be less susceptible to further antibody rejection once the hyperacute phase has been overcome.
Anti‐Gal activity In diabetic patients transplanted with fetal porcine Islet cell clusters
Authors: Gaiili Uri , Tibeil Annika , Samuelsson Bo , Rydberg Lennart , Groth Carl Gustav
Published: November 2008

Abstract: The natural anti‐Gal antibody seems to create a major obstacle for discordant xenotransplantation in humans. It is produced in large amounts in humans (20–100 μg/ml serum), and interacts specifically with the carbohydrate structure Galα1–3Galβ1–4GlcNAc‐R (termed, the a‐galactosyl epitope). The a‐galactosyl epitope is produced in large amounts on porcine cells, as on cells of other nonprimate mammals (1×106 to 35×106 epitopes per cell). The interaction of anti‐Gal with α‐galactosyl epitopes on the xenograft was found to mediate the immune destruction of discordant xenografts. In view of the intensive production of anti‐Gal under physiologic conditions, it was of interest to determine whether the immune system in humans reacts against α‐galactosyl epitopes on xenografts by increasing the activity (i.e., titer and affinity) of this antibody. For this purpose, anti‐Gal titer and affinity were studied in sera of diabetic patients transplanted with fetal porcine islet cell clusters (ICC) by Groth and colleagues (Lancet 1994:344:1402). Titers of anti‐Gal were determined by a hemagglutination assay with rabbit red blood cells and by ELISA with mouse laminin as a solid‐phase antigen. Affinity of the antibody was estimated by equilibrium dialysis with the radiolabeled free haptenic form of the a‐galactosyl epitope, i.e. [3H]Galα1–3Galβ1–4GlcNAc. All assays revealed a marked increase in anti‐Gal activity within 5–8 weeks posttransplantation. The increase in anti‐Gal titers ranged between eight‐and sixty‐four fold. A similar increase was observed in the affinity of anti‐Gal, as assayed in equilibrium dialysis. Immunoglobulin concentration did not increase posttransplantation, suggesting that the observed increase in anti‐Gal activity is the result of a specific immune response against α‐galactosyl epitopes on the xenograft. The elevation in anti‐Gal activity was observed in all three immunoglobulin classes and the highest activity was found within the IgG class. Furthermore, analysis of antibodies against porcine endothelial cells in ELISA has indicated that most of the increased activity against these cells in the serum of the transplanted patients, may be attributed to the elevation in activity of anti‐Gal. These findings raise the possibility that anti‐Gal, which is highly active in patients with xenotransplants, may contribute to chronic rejection of the xenograft by binding effectively to α‐galactosyl epitopes on the xenograft cells and inducing inflammatory reactions against the graft.