Regioselective enzymatic aminoacylation of lobucavir to give an intermediate for lobucavir prodrug

Synthesis of lobucavir prodrug, L-valine, [(1S,2R,3R)-3-(2-amino-1,6-dihydro-6-oxo-9H-purin-9-yl)-2-(hydroxymethyl)cyclobutyl]methyl ester monohydrochloride (BMS 233866), requires regioselective coupling of one of the two hydroxyl groups of lobucavir (BMS 180194) with valine. Either hydroxyl group of lobucavir could be selectively aminoacylated with valine by using enzymatic reactions. N-[(Phenylmethoxy)carbonyl]-L-valine, [(1R,2R,4S)-2-(2-amino-6-oxo-1H-purin-9-yl)-4-(hydroxymethyl)cyclobutyl]methyl ester (3, 82.5% yield), was obtained by selective hydrolysis of N,N′-bis[(phenylmethoxy)carbonyl]bis[L-valine], O,O′-[(1S,2R,3R)-3-(2-amino-6-oxo-1H-purin-9-yl)cyclobuta-1,2-diyl]methyl ester (1) with lipase M, and L-valine, [(1R,2R,4S)-2-(2-amino-1,6-dihydro-6-oxo-9H-purin-9-yl)-4-(hydroxymethyl)cyclobutyl]methyl ester monohydrochloride (4, 87% yield) was obtained by hydrolysis of bis[L-valine], O,O′-[(1S,2R,3R)-3-(2-amino-6-oxo-1H-purin-9-yl)cyclobuta-1,2-diyl]methyl ester, dihydrochloride (2), with lipase from Candida cylindracea. The final intermediate for lobucavir prodrug, N-[(phenylmethoxy)carbonyl]-L-valine, [(1S,2R,4R)-3-(2-amino-6-oxo-1H-purin-9-yl)-2-(hydroxymethyl)cyclobutyl]methyl ester (5), could be obtained by transesterification of lobucavir using ChiroCLEC™ BL (61% yield), or more selectively by using immobilized lipase from Pseudomonas cepacia (84% yield).     

Immunocytochemistry of cytoskeletal proteins in adult Schistosoma mansoni

Antisera to vertebrate actin and actin-binding proteins were used to characterize the cytoskeleton of adult Schistosoma mansoni. Actin, alpha-actinin and tropomyosin immunoreactivities were detected in the cytoplasm of the apical tegument. Antiserum to alpha-actinin bound to the tegumental spines and this protein may be involved in cross-linking of spine actin filaments. Actin, alpha-actinin and tropomyosin antisera bound to the musculature. Strongest immunoreactivity was seen in the parenchyma. Antisera to actin, alpha-actinin, tropomyosin and spectrin bound to parenchyma cells including those of the tubercles, suggesting that these proteins are located in muscle cell bodies. The distribution of cytoskeletal proteins is discussed in relation to tegumental repair processes.     

Granulosa cells as a source and target organ for tumor necrosis factor-alpha

Tumor necrosis factor (TNF-alpha), a 17 kDa cytokine, is a product of activated macrophages which was recently shown to be produced by rat and bovine granulosa cells. In the present work, human granulosa cells derived from preovulatory follicles were used. It was demonstrated that human granulosa cells produce TNF-alpha (5-10 units/300,000 cells per 15 h). This production was increased by addition of follicle-stimulating hormone or by a combination of human chorionic gonadotrophin and CSF to the culture media. TNF was also found in bovine follicular fluid and the concentration was higher in the periovulatory than mid-cycle follicles. TNF-alpha was found to increase prostaglandin F-2 alpha production by human granulosa cells (P less than 0.001). We conclude that granulosa cells are both a source and target organ for TNF-alpha.     

The mononuclear cell in human blood which mediates antibody-dependent cellular cytotoxicity to virus-infected target cells. II. Identification as a K cell.

Studies were carried out to determine whether the mononuclear cell in human blood which mediates antibody-dependent cellular cytotoxicity (ADCC) to herpes simplex virus (HSV)-infected target cells has surface Fc receptors which participate in the reaction. The F (ab')2 fragment of human IgG antibody was inactive both in ADCC and in complement-mediated cytolysis, but retained the capacity to neutralize infectious virus, to agglutinate erythrocytes coated with viral antigens, and to bind to the surface of virus-infected cells. Treatment of sensitized virus-infected target cells with staphylococcus protein A, which has affinity for the Fc epitope of IgG, strongly reduced their susceptibility to lysis by ADCC in a dose-dependent relationship. These findings indicate that the Fc portion of IgG antibody to the virus is necessary for cytotoxicity. Treatment of blood mononuclear cells with either heat-aggregated gamma-globulin or HSV immune complexes inhibited effector cell activity. The presence of "third party" cellular immune complexes also strongly inhibited ADCC. Adsorption of mononuclear cells to plastic surfaces coated with soluble third party immune complexes resulted in a significant reduction in effector cell activity. These findings demonstrate that the ADCC effector cell possesses surface Fc receptors which are utilized in the ADCC reaction. The presence of Fc receptors on the surface of the effector cell indicates that it is a K cell rather than a null cell.     

土壤中含EB病毒诱导物的检测

从广西壮族自治区梧州市、苍梧县、罗城县和北京市收集的土壤标本中发现有EB病毒诱导物。梧州市和苍梧县沿公路和江河两旁桐油树下的土壤标本,对EB病毒早期抗原诱导的阳性率为40～58％。在其他大戟科植物下的土壤标本中,也发现有EB病毒诱导物。对桐油树下土壤中EB病毒诱导物与鼻咽癌发生的可能关系进行了讨论。     

小黑杨转双价抗虫基因的研究

用根癌农杆菌介导的叶盘法,将蜘蛛杀虫肽与Bt基因C肽序列的融合基因导入小黑杨(Populus simonii×P.nigra),所获得的3株卡那霉素抗性再生植株进行PCR和PCR-Southern杂交检测的结果均为阳性,Southern杂交检测的结果2株为阳性.抗虫试验结果显示,3个转基因株系均具有明显的抗虫效果,能显著抑制舞毒蛾幼虫的生长发育,表现出强烈的抗虫作用.     

微量血胆红素测定仪的临床应用

目的 :了解微量血胆红素测定仪测定血胆红素的正确性。方法 :黄疸婴儿 5 0例 ,男 2 9例 ,女 2 1例 ,年龄平均为 2 1 6天。采用玻璃毛细管在患儿足跟采集少量血在微量血胆红素测定仪上测定 ,并与静脉采血测得的血胆红素值进行比较。结果 :二种方法测得的血红素值无显著差别 (P >0 0 5 ) ,二者之间有非常显著的相关 ,相关系数r=0 96 996 ,P <0 0 1。结论 :微量法测定血胆红素简便 ,迅速 ,减少对婴儿的损伤 ,为黄疸婴儿血胆红素的测定提供了较大方便 ,应予推广应用     

APC mutant zebrafish uncover a changing temporal requirement for wnt signaling in liver development

Developmental signaling pathways hold the keys to unlocking the promise of adult tissue regeneration, and to inhibiting carcinogenesis. Patients with mutations in the Adenomatous Polyposis Coli (APC) gene are at increased risk of developing hepatoblastoma, an embryonal form of liver cancer, suggesting that Wnt affects hepatic progenitor cells. To elucidate the role of APC loss and enhanced Wnt activity in liver development, we examined APC mutant and wnt inducible transgenic zebrafish. APC^+/− embryos developed enlarged livers through biased induction of hepatic gene programs and increased proliferation. Conversely, APC^−/− embryos formed no livers. Blastula transplantations determined that the effects of APC loss were cell autonomous. Induction of wnt modulators confirmed biphasic consequences of wnt activation: endodermal pattern formation and gene expression required suppression of wnt signaling in early somitogenesis; later, increased wnt activity altered endodermal fate by enhancing liver growth at the expense of pancreas formation; these effects persisted into the larval stage. In adult APC^+/− zebrafish, increased wnt activity significantly accelerated liver regeneration after partial hepatectomy. Similarly, liver regeneration was significantly enhanced in APC^Min/+ mice, indicating the conserved effect of Wnt pathway activation in liver regeneration across vertebrate species. These studies reveal an important and time-dependent role for wnt signaling during liver development and regeneration.     

A Label-free Selected Reaction Monitoring Workflow Identifies a Subset of Pregnancy Specific Glycoproteins as Potential Predictive Markers of Early-onset Pre-eclampsia

Pre-eclampsia (PE) is a serious complication of pregnancy with potentially life threatening consequences for both mother and baby. Presently there is no test with the required performance to predict which healthy first-time mothers will go on to develop PE. The high specificity, sensitivity, and multiplexed nature of selected reaction monitoring holds great potential as a tool for the verification and validation of putative candidate biomarkersfor disease states. Realization of this potential involves establishing a high throughput, cost effective, reproducible sample preparation workflow. We have developed a semi-automated HPLC-based sample preparation workflow before a label-free selected reaction monitoring approach. This workflow has been applied to the search for novel predictive biomarkers for PE.To discover novel candidate biomarkers for PE, we used isobaric tagging to identify several potential biomarker proteins in plasma obtained at 15 weeks gestation from nulliparous women who later developed PE compared with pregnant women who remained healthy. Such a study generates a number of “candidate” biomarkers that require further testing in larger patient cohorts. As proof-of-principle, two of these proteins were taken forward for verification in a 100 women (58 PE, 42 controls) using label-free SRM. We obtained reproducible protein quantitation across the 100 samples and demonstrated significant changes in protein levels, even with as little as 20% change in protein concentration. The SRM data correlated with a commercial ELISA, suggesting that this is a robust workflow suitable for rapid, affordable, label-free verification of which candidate biomarkers should be taken forward for thorough investigation. A subset of pregnancy-specific glycoproteins (PSGs) had value as novel predictive markers for PE.The identification of clinically relevant plasma biomarkers with diagnostic and/or predictive value continues to challenge the proteomics field. Whereas once the biomarker pipeline was described as a two part discovery and validation process, there is increasing consensus that an intermediate step is required in which the proteins identified in the discovery phase are technically verified in 50 to 200 samples. This verification step identifies false positives from the discovery phase and allows prioritization of proteins to be taken into large-scale clinical validation studies (1). Although commercial ELISA kits may be used in this phase, these are unavailable for many proteins, are expensive, and may lack specificity. In addition, sample requirements may be too high to perform ELISA on all candidates, especially if many proteins are identified as potential markers by low powered, high penetration discovery workflows.Selected reaction monitoring (SRM)¹ mass spectrometry has great potential as an alternative verification method (2–6) as it can be multiplexed, customized, and is highly specific. This potential has not been exploited to date, largely because of technical issues developing a low-cost, reproducible workflow encompassing plasma and serum preparation and LC/MS analysis with the capability to measure protein levels reproducible in hundreds of samples. With traditional stable isotope dilution SRM (SID-SRM), the high cost of accurately quantified, purified stable isotope encoded peptides or proteins may be prohibitive for the verification of multiple peptides from many proteins. Label-free relatively quantitative methods are increasingly popular in discovery proteomics but to a much lesser extent in targeted SRM studies (7, 8).For any SRM method, sample preparation workflows must balance the extent of enrichment and fractionation to enable quantification of lower abundance proteins, against increased technical variability (which is influenced by the number of sample handling steps) and reduced multiplexed potential as a consequence of fractionating peptides from the protein of interest into several distinct fractions. It is also essential that the true technical variation in the workflow is quantitatively evaluated from freezer to MS analysis, rather than just the variation within the LC-SRM part of the experiment. As a paradigm for a label-free SRM assay, we developed our workflow and applied it to the verification of candidate biomarkers that indicate the risk of pre-eclampsia (PE).PE affects 2–8% of pregnancies, and is characterized by hypertension and proteinuria, which may progress to severe maternal complications or death (9). Because delivery of the infant is the only effective intervention, a third of babies are born premature and fetal or newborn mortality is increased three- to 10-fold (10). Its complex etiology involves abnormal placentation, an altered immune response and a sensitized maternal vascular endothelium (11). Prediction of the condition in early pregnancy would allow prevention strategies, such as low dose aspirin, to be targeted to high risk women. In first-time pregnant women, a group particularly at risk, biomarkers continue to fall short of a test that would be useful or cost effective in clinical practice (12–14). Better-performing novel biomarkers are required.The aim of this study was to identify candidate predictive biomarkers for PE and then develop a verification assay using mass spectrometry to determine whether these should be taken forward into more extensive and expensive validation studies. Initial discovery experiments were employed using a pooled sample iTRAQ approach using two different MS platforms to increase plasma proteome coverage. Among the set of proteins discovered, we then developed a label-free SRM assay for relative quantification of CXCL7 (Platelet basic protein; PBP) and members of the Pregnancy specific glycoprotein (PSG) family in a 100-sample set from the international SCreeningfOr Pregnancy Endpoints (SCOPE) study (www.scopestudy.net). Our workflow allowed the specificity and linearity of response for each peptide to be determined, along with true technical variability. Although absolute concentration and LOD/LOQ cannot be calculated using this approach, we aimed to test the hypothesis that a label-free SRM approach could provide a rapid, robust, and efficient screen of candidate plasma biomarkers.