Calcium isotopes in deep time: Potential and limitations

Calcium is an essential element in the biogeochemical cycles that regulate the long-term climate state of Earth. The removal of CO2 from the ocean-atmosphere system is controlled by the burial of carbonate sediments (CaCO3), ultimately linking the global calcium and carbon cycles. This fundamental link has driven the development of the stable calcium isotope proxy with applica-tion to both ancient skeletal and non-skeletal bulk carbonate sediments. Calcium isotope ratios (44/40Ca) have been used to track long-term changes in seawater chemistry (e.g., aragonite vs. calcite seas) and to elucidate short-term climatic perturbations associated with mass extinction events. However, developments in the calcium isotope proxy have shown that 44/40Ca values in carbonate minerals also are sensitive to changes in precipitation rates, mineralogy and diagene-sis, thereby complicating the application of the proxy to the reconstruction of global cycles. First, inorganic carbonate precipitation experiments have demonstrated that carbonate 44/40Ca values are sensitive to precipitation rates with higher rates generally leading to larger fractiona-tion. Second, 44/40Ca values are sensitive to carbonate mineralogy with inorganic aragonite and calcite being on average ~1.5‰ and ~0.9‰ depleted relative to contemporaneous seawater, re-spectively. The effects of both changes in carbonate mineralogy and precipitation rates affect primary and secondary minerals, but are particularly pronounced during carbonate diagenesis where relatively slow rates of recrystallization and neomorphism can lead to significant changes in bulk sediment 44/40Ca values. Third, changes in faunal composition expressed in skeletal fossil archives can lead to large changes in carbonate 44/40Ca values that are decoupled from changes in global cycles. Nevertheless, when these factors are appropriately considered the ap-plication of calcium isotopes in ancient carbonate sediments becomes a powerful tool for under-standing biogeochemical processes that operate over many scales; from diagenetic changes with-in the sediment pore-space, to regional changes across ancient carbonate platforms, and to global changes in seawater chemistry through time. Importantly, the processes that contribute to varia-bility in carbonate 44/40Ca values are likely to impact other carbonate-bound proxies, highlight-ing the potential for calcium isotopes as a hint to better understand the variability of other iso-tope systems

Application of hepatitis B virus (HBV) DNA sequence polymorphisms to the study of HBV transmission

Short sequences in hypervariable regions of the hepatitis B virus (HBV) genome can be used to identify different strains, providing a novel approach to the study of HBV transmission. The nucleotide sequence in positions 2551-2650 (1: EcoRI site) was determined for serum HBV DNA from 96 Chinese children living in Hong Kong and from 38 of their parents. HBV DNA was extracted and sequenced after amplification with the polymerase chain reaction, using as primers oligonucleotides corresponding to two conserved sequences. Among 82 unrelated children, 32 HBV DNA variants were present. One sequence was present in 33 children and 31 variants were found among the other 49. Siblings within each of nine families had the same variant; in three families siblings had different variants. Six of the eight fathers and 28 of the 30 mothers had HBV DNA sequences identical to those of their offspring. A total of 34 variants were found among the 134 individuals. The hypothesis of random assortment of sequences in parents and children was rejected (P < .00005). Thus, this new approach proves the occurrence of intrafamilial transmission of HBV among Chinese.published_or_final_versio

Effect of sialic acid loss on dendritic cell maturation

Sialic acids are key structural determinants and contribute to the functionality of a number of immune cell receptors. Previously, we demonstrated that differentiation of human dendritic cells (DCs) is accompanied by an increased expression of sialylated cell surface structures, putatively through the activity of the ST3Gal.I and ST6Gal.I sialyltransferases. Furthermore, DC endocytosis was reduced upon removal of the cell surface sialic acid residues by neuraminidase. In the present work, we evaluate the contribution of the sialic acid modifications in DC maturation. We demonstrate that neuraminidase-treated human DCs have increased expression of major histocompatibility complex (MHC) and costimulatory molecules, increased gene expression of specific cytokines and induce a higher proliferative response of T lymphocytes. Together, the data suggest that clearance of cell surface sialic acids contributes to the development of a T helper type 1 proinflammatory response. This postulate is supported by mouse models, where elevated MHC class II and increased maturation of specific DC subsets were observed in DCs harvested from ST3Gal.I(-/-) and ST6Gal.I(-/-) mice. Moreover, important qualitative differences, particularly in the extent of reduced endocytosis and in the peripheral distribution of DC subsets, existed between the ST3Gal.I(-/-) and ST6Gal.I(-/-) strains. Together, the data strongly suggest not only a role of cell surface sialic acid modifications in maturation and functionality of DCs, but also that the sialic acid linkages created by different sialyltransferases are functionally distinct. Consequently, with particular relevance to DC-based therapies, cell surface sialylation, mediated by individual sialyltransferases, can influence the immunogenicity of DCs upon antigen loading

Adeno-associated virus-mediated heme oxygenase-1 gene transfer suppresses the progression of micronodular cirrhosis in rats

Aim: To test the hypothesis that enhancement of the activity of heme oxygenase can interfere with processes of fibrogenesis associated with recurrent liver injury, we investigated the therapeutic potential of over-expression of heme oxygense-1 in a CCI 4-induced micronodular cirrhosis model. Methods: Recombinant adeno-associated viruses carrying rat HO-1 or GFP gene were generated. 1×10 12 vg of adeno-associated viruses were administered through portal injection at the time of the induction of liver fibrosis. Results: Conditioning the rat liver with over-expression of HO-1 by rAAV/HO-1 significantly increased the HO enzymatic activities in a stable manner. The development of micronodular cirrhosis was significantly inhibited in rAAV/HO-1-transduced animals as compared to controls. Portal hypertension was markedly diminished in rAAV/ HO-1-transduced animals as compared to controls, whereas there are no significant changes in systolic blood pressure. This finding was accompanied with improved liver biochemistry, less infiltrating macrophages and less activated hepatic stellate cells (HSCs) in rAAV/ HO-1-transduced livers. Conclusions: Enhancement of HO activity in the livers suppresses the development of cirrhosis. © 2006 The WJG Press. All rights reserved.published_or_final_versio

The economic burden of influenza-associated outpatient visits and hospitalizations in China: a retrospective survey

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Examining the relationship between principals leadership style and their level of emotional intelligence / Prof. Madya Dr. Ngee Kiong Lau and Sueb Hj. Ibrahim

As the context of leadership is changing, to lead effectively will be critical to the long term success of organizations. Therefore, school principals will need to combine several leadership qualities in order to succeed. School principals have to develop their rational in establishing which leadership style will result to high performance outcomes and leadership effectiveness. Thus, the nature of the leader's emotional connectedness to others is apparently in the growing interest in numerous studies on the effect of emotional intelligence on leadership. Moreover, at present, there seems to be increasing attention being given to organizational life and leadership and general agreement about the need to incorporate the role of emotion into research on educational leaders.To be effective school leaders in pursuit of effective leadership, there should be a significant link between principals' leadership style and their level of emotional intelligence and how this link can be a driving force that can bring an impact on their leadership effectiveness. Moreover, to build the leadership capacity necessary for effective leadership, school principals will not only need to possess effective leadership style, but also well-developed social and emotional skills. A high IQ can do much to resolve leadership challenges; however, without allowing the heart to intervene, one is at disadvantage in being an effective leader (Chemise & Adler, 2000; Goleman, 1995; Ryback, 1998). Therefore, utilizing these connections, this study seeks to identify the connection of principal's leadership style and emotional intelligence

A conceptual model of performance measurement for supply chains

Supply chain management (SCM) has gained a tremendous amount of attention from both industries and researchers since the last decade. Until now, there are numerous papers, articles, and reports that address SCM, but there is still a lack of integration between the existing performance measurement methods and practical requirements for the SCM. An innovative performance measurement method is proposed to provide necessary assistance for performance improvement in SCM. The proposed method will address this purpose in these four aspects: a simplified supply chain model; tangible and intangible performance measures in multiple dimensions; a cross-organizational performance measurement; and fuzzy set theory and weighted average method.published_or_final_versio

Identification of Novel Rosavirus Species That Infects Diverse Rodent Species and Causes Multisystemic Dissemination in Mouse Model

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