Endocrine and exocrine secretion of leptin by the gastric mucosa.

Leptin is a hormone that plays important roles in nutritional status and in obesity. By means of immunocytochemistry, two populations of leptin-secreting cells were found in the lower half of the gastric mucosa. One consists of numerous large cells located around the gastric pits, the Chief epithelial cells, whereas the second refers to much smaller cells, strongly stained, few in number, and scattered between the gastric pits, the endocrine cells. By double immunostaining, leptin and pepsinogen were colocalized in the Chief cells, whereas the endocrine cells were positive only for leptin. Immunoelectron microscopy showed that leptin is present along the rough endoplasmic reticulum-Golgi-granules secretory pathways of the Chief and endocrine cells. On the other hand, leptin-receptor (long and short forms) immunolabelings, although absent in the gastric epithelial cell plasma membranes, were present in enterocytes at the level of their apical and basolateral membranes. Duodenal, jejunal, and ileal enterocytes displayed similar labelings for the leptin receptor. Thus, exocrine and endocrine secretions of leptin together with the presence of leptin receptors on enterocyte plasma membranes constitute a gastroenteric axis that coordinates the role played by leptin in the digestive tract.     

牛血清白蛋白对小鼠原核期胚胎玻璃化冷冻的影响

以小鼠原核期胚胎为对象,以胚胎的存活率、卵裂率、囊胚率以及囊胚细胞数作为检测指标,在M2液的基础上添加8种浓度(0,2,4,8,16,32,64,96mg/mL)牛血清白蛋白(BSA)配置防冻液,探讨防冻液和玻璃化冷冻后对胚胎发育的影响。BSA防冻液对胚胎发育影响的实验结果表明,8个浓度组间以及与对照组间胚胎的卵裂率、囊胚率以及囊胚细胞数无显著差异(P>0.05),说明在防冻液中加入一定浓度的BSA对小鼠胚胎无毒性作用。防冻液经玻璃化冷冻后对胚胎发育影响的实验表明,8个浓度组间冷冻胚胎复苏后的存活率、卵裂率、囊胚率及囊胚细胞数无显著差异(P>0.05)。表明BSA在这种防冻液中没有明显的保护作用。从经济、实用、生物安全角度考虑,不支持在玻璃化防冻液中添加BSA。     

眼镜蛇及竹叶青蛇咬伤与心肌酶谱研究

目的 探讨眼镜蛇和竹叶青蛇咬伤后心肌酶谱改变的关系,以提高蛇伤的诊治水平.方法 选择在我科住院治疗的眼镜蛇咬伤病人124例及竹叶青蛇咬伤86例,根据其肢体肿胀程度分为轻度、中度、重度3组,所有病人在入院时均查心肌酶谱及心电图,心肌酶谱中还增加了肌红蛋白(Mb)、抗心肌钙蛋白T(cTnT)、肌钙蛋白I(cTnI)检测参数.并对实验室检测的心肌酶谱进行统计分析.结果 124例眼镜蛇咬伤病人中,心肌酶谱异常者占87.8%;86例竹叶青蛇咬伤病人中,心肌酶谱异常者占79.4%.中度肿胀组和重度肿胀组心肌酶谱异常发生率为100%;中度组与轻度组比较,心肌酶谱各项指标明显升高(P＜0.05);重度组与轻度组比较,心肌酶谱各项指标更显著(P＜0.01).眼镜蛇咬伤中、重度肿胀组,其心电图改变有显著性差异(P＜0.05),但竹叶青蛇伤组,心电图变化无特殊临床意义.结论 我国南方常见的眼镜蛇及竹叶青蛇咬伤,心肌酶谱变化显著,且升高与受伤的严重程度呈正相关,可作为诊断和观察病情的敏感指标.     

Development of a simple molecular marker specific for detecting the self-compatible<Emphasis Type="Italic">S4′</Emphasis> haplotype in sweet cherry (<Emphasis Type="Italic">Prunus avium</Emphasis> L.)

In sweet cherry (Prunus avium L.), theS4′ haplotype, characterized by a self-incompatibility (SI) defect in pollen, is self-compatible and is derived from the self-incompatibleS4 haplotype by x-ray mutagenesis.SFBs (S haplotype-specific F-box protein genes) have been found to associate with pollen determinant of SI. This report identified theSFB4′ of the self-compatibleS4′ haplotype. The alignment of the sequences ofSFB4′ andSFB4 by the BLAST program revealed a 4-bp deletion inSFB4′, which is TTTA. The sequence polymorphism generated by the TTTA deletion inSFB4′ was exploited to develop a simple molecular marker specific for detecting theS4′ but not theS4 haplotype. The simple marker specific to theS4′ haplotype can be visualized directly on an agarose gel, so it can be immediately applied to a marker-assistant cherry-breeding program. Thus, this work provides a practical molecular marker for cherry breeding. Principal author. An erratum to this article is available at .     

Genistein induces G<Subscript>2</Subscript>/M cell cycle arrest via stable activation of ERK1/2 pathway in MDA-MB-231 breast cancer cells

Genistein is an isoflavonoid present in soybeans that exhibits anti-carcinogenic effect. Several studies have shown that genistein can trigger G2/M cell cycle arrest and inhibit cell growth in human breast cancer cells. In the present study, we assessed the role of MEK-ERK cascade in regulation of genistein-mediated G2/M cell cycle arrest in the hormone-independent cell line MDA-MB-231. Flow cytometric analysis showed that treatment of MDA-MB-231 cells with genistein induced a concentration-dependent accumulation of cells in the G2/M phase of the cell cycle, with a parallel depletion of the percentage of cells in G0/G1. Genistein-mediated G2/M arrest was associated with a decrease in the protein levels of Cdk1, cyclinB1, and Cdc25C as determined by Western blot analysis. Genistein induced a slow and stable activation of phosphorylated ERK1/2 in a concentration- and time-dependent manner in MDA-MB-231 cells. MEK1/2-specific inhibitor PD98059 blocked genistein-induced activation of ERK1/2 and markedly attenuated genistein-induced G2/M arrest. Furthermore, genistein induced the expression of Ras and Raf-1 protein. Genistein also up-regulated steady-state levels of both c-Jun and c-Fos. PD98059 did not depress genistein-induced up-regulation of Ras and Raf-1 protein. However, it markedly blocked genistein-induced up-regulation of c-Jun and c-Fos. These results suggest that the Ras/MAPK/AP-1 signal pathway may be involved in genistein-induced G2/M cell cycle arrest in MDA-MB-231 breast cancer cells.     

A rugged free energy landscape separates multiple functional RNA folds throughout denaturation

The dynamic mechanisms by which RNAs acquire biologically functional structures are of increasing importance to the rapidly expanding fields of RNA therapeutics and biotechnology. Large energy barriers separating misfolded and functional states arising from alternate base pairing are a well-appreciated characteristic of RNA. In contrast, it is typically assumed that functionally folded RNA occupies a single native basin of attraction that is free of deeply dividing energy barriers (ergodic hypothesis). This assumption is widely used as an implicit basis to interpret experimental ensemble-averaged data. Here, we develop an experimental approach to isolate persistent sub-populations of a small RNA enzyme and show by single molecule fluorescence resonance energy transfer (smFRET), biochemical probing and high-resolution mass spectrometry that commitment to one of several catalytically active folds occurs unexpectedly high on the RNA folding energy landscape, resulting in partially irreversible folding. Our experiments reveal the retention of molecular heterogeneity following the complete loss of all native secondary and tertiary structure. Our results demonstrate a surprising longevity of molecular heterogeneity and advance our current understanding beyond that of non-functional misfolds of RNA kinetically trapped on a rugged folding-free energy landscape.     

An approach of orthology detection from homologous sequences under minimum evolution

In the field of phylogenetics and comparative genomics, it is important to establish orthologous relationships when comparing homologous sequences. Due to the slight sequence dissimilarity between orthologs and paralogs, it is prone to regarding paralogs as orthologs. For this reason, several methods based on evolutionary distance, phylogeny and BLAST have tried to detect orthologs with more precision. Depending on their algorithmic implementations, each of these methods sometimes has increased false negative or false positive rates. Here, we developed a novel algorithm for orthology detection that uses a distance method based on the phylogenetic criterion of minimum evolution. Our algorithm assumes that sets of sequences exhibiting orthologous relationships are evolutionarily less costly than sets that include one or more paralogous relationships. Calculation of evolutionary cost requires the reconstruction of a neighbor-joining (NJ) tree, but calculations are unaffected by the topology of any given NJ tree. Unlike tree reconciliation, our algorithm appears free from the problem of incorrect topologies of species and gene trees. The reliability of the algorithm was tested in a comparative analysis with two other orthology detection methods using 95 manually curated KOG datasets and 21 experimentally verified EXProt datasets. Sensitivity and specificity estimates indicate that the concept of minimum evolution could be valuable for the detection of orthologs.     

A compatible exon-exon junction database for the identification of exon skipping events using tandem mass spectrum data

Background  

Alternative splicing is an important gene regulation mechanism. It is estimated that about 74% of multi-exon human genes have alternative splicing. High throughput tandem (MS/MS) mass spectrometry provides valuable information for rapidly identifying potentially novel alternatively-spliced protein products from experimental datasets. However, the ability to identify alternative splicing events through tandem mass spectrometry depends on the database against which the spectra are searched.     

Humicola insolens cutinase-catalyzed lactone ring-opening polymerizations: kinetic and mechanistic studies

This paper explores reaction kinetics and mechanism for immobilized Humicola insolenscutinase (HIC), an important new biocatalyst that efficiently catalyzes non-natural polyester synthetic reactions. HIC, immobilized on Lewatit, was used as catalyst for epsilon-caprolactone (CL) and omega-pentadecalactone (PDL) ring-opening polymerizations (ROPs). Plots of percent CL conversion vs time were obtained in the temperature range from 50 to 90 degrees C. The kinetic plot of ln([M]0/[M]t) vs time (r2 = 0.99) for HIC-catalyzed bulk ROP of CL was linear, indicating that chain termination did not occur and the propagation rate is first order with respect to monomer concentration. Furthermore, linearity to 90% conversion for M(n) vs fractional CL conversion is consistent with a chain-end propagation mechanism. Deviation from linearity above 90% conversion indicates that a competition between ring-opening chain-end propagation and chain growth by steplike polycondensations takes place at high monomer conversion. HIC was inactive for catalysis of L-lactide and (R,S)-beta-butyrolactone ROP. HIC-catalyzed ROP of epsilon-CL and PDL in toluene were successfully performed, giving high molecular weight poly(epsilon-caprolactone) and omega-poly(pentadecalactone). In addition, the relative activities of immobilized Candida antarctica lipase B (CALB) and HIC for epsilon-CL and PDL polymerizations are reported herein.