Serine palmitoyltransferase (SPT) deficient mice absorb less cholesterol

Serine palmitoyltransferase (SPT) is the key enzyme for the biosynthesis of sphingolipids. It has been reported that oral administration of myriocin (an SPT inhibitor) decreases plasma sphingomyelin (SM) and cholesterol levels, and reduces atherosclerosis in apoE knockout (KO) mice. We studied cholesterol absorption in myriocin-treated WT or apoE KO animals and found that, after myriocin treatment, the mice absorbed significantly less cholesterol than controls, with no observable pathological changes in the small intestine. More importantly, we found that heterozygous Sptlc1 (a subunit of SPT) KO mice also absorbed significantly less cholesterol than controls. To understand the mechanism, we measured protein levels of Niemann-Pick C1-like 1 (NPC1L1), ABCG5, and ABCA1, three key factors involved in intestinal cholesterol absorption. We found that NPC1L1 and ABCA1 were decreased, whereas ABCG5 was increased in the SPT deficient small intestine. SM levels on the apical membrane were also measured and they were significantly decreased in SPT deficient mice, compared with controls. In conclusion, SPT deficiency might reduce intestinal cholesterol absorption by altering NPC1L1 and ABCG5 protein levels in the apical membranes of enterocytes through lowering apical membrane SM levels. This may be also true for ABCA1 which locates on basal membrane of enterocytes. Manipulation of SPT activity could thus provide a novel alternative treatment for dyslipidemia.     

Staphylococcus aureus persistence properties associated with bovine mastitis and alternative therapeutic modalities

Staphylococcus aureus is an important agent of contagious bovine intramammary infections in dairy cattle. Its ability to persist inside the udder is based on the presence of important mechanisms such as its ability to form biofilms, polysaccharide capsules small colony variants, and their ability to invade professional and nonprofessional cells, which will protect S. aureus from the innate and adaptive immune response of the cow, and from antibiotics that are no longer considered to be sufficient against S. aureus bovine mastitis. In this review, we present the recent research outlining S. aureus persistence properties inside the mammary gland, including its regulation mechanisms, and we highlight alternative therapeutic strategies that were tested against S. aureus isolated from bovine mastitis such as the use of probiotic bacteria, bacteriocins and bacteriophages. Overall, the persistence of S. aureus inside the mammary gland remains a pressing veterinary problem. A thorough understanding of staphylococcal persistence mechanisms will elucidate novel ways that can help in the identification of novel treatments.     

Splicing‐dependent NMD does not require the EJC in Schizosaccharomyces pombe

Nonsense‐mediated mRNA decay (NMD) is a translation‐linked process that destroys mRNAs with premature translation termination codons (PTCs). In mammalian cells, NMD is also linked to pre‐mRNA splicing, usually PTCs trigger strong NMD only when positioned upstream of at least one intron. The exon junction complex (EJC) is believed to mediate the link between splicing and NMD in these systems. Here, we report that in Schizosaccharomyces pombe splicing also enhances NMD, but against the EJC model prediction, an intron stimulated NMD regardless of whether it is positioned upstream or downstream of the PTC and EJC components are not required. Still the effect of splicing seems to be direct—we have found that the important NMD determinant is the proximity of an intron to the PTC, not just the occurrence of splicing. On the basis of these results, we propose a new model to explain how splicing could affect NMD.     

A Gly/Ala switch contributes to high affinity binding of benzoxazinone-based non-peptide oxytocin receptor antagonists

Non-peptide antagonists of the oxytocin receptor (OTR) have been developed to prevent pre-term labour. The benzoxazinone-based antagonists L-371,257 and L-372,662 display pronounced species-dependent pharmacology with respect to selectivity for the OTR over the V(1a) vasopressin receptor. Examination of receptor sequences from different species identified Ala(318) in helix 7 of the human OTR as a candidate discriminator required for high affinity binding. The mutant receptor [A318G]OTR was engineered and characterised using ligands representing many different chemical classes. Of all the ligands investigated, only the benzoxazinone-based antagonists had decreased affinity for [A318G]OTR. Molecular modelling revealed that Ala(318) provides a direct hydrophobic contact with a methoxy group of L-371,257 and L-372,662.     

S100A4基因表达在肿瘤转移中的作用

肿瘤转移是细胞恶性的重要标志之一,有许多基因和因子都参与这一过程。对S100A4基因的研究发现,它可参与细胞周期调控、细胞增殖与分化、血管生成、细胞外基质重建等多种生命过程,调控细胞的生长和运动。在某些特定的肿瘤细胞内,它的表达含量的增加可促进肿瘤细胞发生转移,并与癌症的发生具有某些相关性,可能对人类癌症的发生具有预后作用。现就S100A4基因表达与肿瘤转移的关系进行初步的探讨,以期对癌症的临床诊断提供一些参考。     

乙型肝炎表面抗原疑难判定血清的研究

用中国药品生物制品检定所检定合格的国内外HBsAgEIA试剂及ABBOTT抗 HBs、抗 HBcEIA试剂 ,对所收集的 13份HBsAg疑难判定血清进行检测 ,并用PCR方法检测血清中HBVDNA ,结果显示国内外HBsAg试剂对部分HBVDNA阳性样品的检出率差异较大 ,提示这些样品可能为S基因突变株或HBsAg含量较低 ,因此 ,HBsAgEIA试剂的敏感度仍有待进一步提高 ,并应进一步研制检测S基因突变株的HBsAg诊断试剂。     

Pteridophyte diversity and species composition in four Amazonian rain forests

Abstract. Local variation in individual density, species composition, species richness and species diversity of terrestrial pteridophytes were studied at four sites in the tropical lowland rain forest of western Amazonia. 15 568 pteridophyte individuals representing 40 species were recorded in four plots. The variability among subplots within the same plot was considerable in all the characteristics measured (number of individuals, number of species, species diversity); the square 1‐ha plot was more homogeneous in these respects than any of the three 5 m by 1300 m transects. Species richness was affected by the density of individuals both within and among plots. Density of individuals was not affected by topographical position within any of the plots, whereas in some of the plots both species richness and species diversity were. Clustering and ordination analyses showed that floristically similar subplots could be found in different plots: although there was a tendency for subplots from the same plot to be floristically similar and therefore to group together, many recognized groups included subplots from two or more plots. Both within and among plots, the floristic differences corresponded to topographic position and were probably related to soil drainage. This was also evident in that the abundance patterns of many species followed the topography.     

PSEUDONEOCHLORIS MARINA (CHLOROPHYTA), A NEW COCCOID ULVOPHYCEAN ALGA, AND ITS PHYLOGENETIC POSITION INFERRED FROM MORPHOLOGICAL AND MOLECULAR DATA

Ultrastructural and molecular sequence data were used to assess the phylogenetic position of the coccoid green alga deposited in the culture collection of the University of Texas at Austin under the name of Neochloris sp. (1445). This alga has uninucleate vegetative cells and a parietal chloroplast with pyrenoids; it reproduces by forming naked biflagellate zoospores. Electron microscopy revealed that zoospores have basal bodies displaced in the counterclockwise absolute orientation and overlapped at their proximal ends. Four microtubular rootlets numbering 2 and 2/1 are alternatively arranged in a cruciate pattern. A system I fiber extends beneath each d rootlet and a system II fiber (rhizoplast) originates from each basal body and extends peripherally along each d rootlet. These features differ substantially from those of the three genera, Ettlia (Komárek) Deason et al., Neochloris (Starr) Deason et al., and Parietochloris Watanabe et Floyd, all of which were previously accommodated in the single genus Neochloris Starr. Sequence data from the nuclear small subunit ribosomal RNA gene were obtained and compared with published green algal sequences. Results from the ultrastructural and sequence data support the placement of Neochloris sp. (The Culture Collection of Algae at the University of Texas at Austin [UTEX] no. 1445) in the Ulvophyceae. This isolate is described as Pseudoneochloris marina , gen. et sp. nov. in the Ulotrichales, Ulvophyceae.     

First isolation of Streptococcus downei from human dental plaques

In this study, we isolated four bacterial strains grown on mitis-salivarius sucrose bacitracin agar. The strains had similar biochemical characteristics to biotypes I or II of mutans streptococci. The four isolates were identified as Streptococcus downei by 16S rDNA and dextranase gene (dex) sequencing as well as polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) targeting dex. To our knowledge, this is the first report of the isolation and identification of S. downei from dental plaque in humans. The results suggest that S. downei can inhabit the human oral cavity.     

Health and wealth: The late-20th century obesity epidemic in the U.S.

Obesity is a rapidly growing public health issue. This paper investigates obesity's relationship to individuals' wealth by analyzing data from a large U.S. longitudinal socio-economic survey. The results show a large negative association between BMI and White female's net worth, a smaller negative association for Black women and White males and no relationship for Black males. Weight changes and dieting also appear associated with wealth changes. Individuals who lose small amounts of weight experience little change in net worth, but those who lose large amounts of weight have a dramatically improved financial position, with Whites showing larger changes than Blacks.