Reduced methyl group acceptance of 1-β-d-arabinofuranosylcytosine-containing DNA polymers

Previous studies have shown that 1-β-d-arabinofuranosylcytosine (ara-C) can induce differentiation of various malignant cells and that DNA methylation patterns become altered under ara-C treatment of those cells. The aim of this study was to investigate whether this influence on DNA methylation is caused by a direct effect of DNA-incorporated ara-C molecules on nuclear DNA methylase. For this reason, we constructed various ara-C-substituted DNA polymers and used them as substrates for highly purified eukaryotic DNA methylase isolated from murine P815 mastocytoma cells. The ara-C incorporation into DNA polymers was measured by either an ara-C-specific radioimmunoassay or by use of radioactive-labelled ara-C during the synthesis of those polymers. We found an inverse correlation between the level of ara-C substitution of the DNA polymers and their methyl group acceptance. Kinetic experiments performed with ara-C-modified DNA polymers pointed out that the mode of action of DNA methylase remains unaltered. DNA methylase is neither detached nor fixed at an ara-C site, but is somehow hindered in its enzymatic activity, probably by slowing down the walking mechanism. Hence, the previously observed hypermethylation of DNA of some eukaryotic cells, propagated in the presence of ara-C, is apparently not due to a direct effect of DNA-incorporated ara-C molecules on endogenous DNA methylase.     

Chirality of the acyl group of β-hydroxy-β-methylglutarylhydroxyabscisic acid

The β-carbon of the acyl group of β-hydroxy-β-methylglutarylhydroxyabscisic acid was shown to possess R-configuration by HPLC analysis of the reduced product.     

Polycomb group蛋白复合体

Polycomb group (PcG) 蛋白是一组通过染色质修饰调控靶基因的转录抑制子, 从生化和功能上它可以分成两个主要的核心蛋白复合体PRC1(Polycomb repressive complex 1)和PRC2(Polycomb repressive complex 2)。研究发现PcG蛋白不仅控制个体正确的发育模式, 而且与细胞的增殖、分化和肿瘤发生有关。文章就PcG蛋白的组成、作用机制及功能进行综述, 并对PcG未来的研究方向进行展望。     

Neighboring group stabilization by σ-holes

We have used density-functional theory to investigate the neighboring-group stabilization of iodine, arsenic, and phosphorus-centered oxyanion moieties in species such as deprotonated 2-iodoxybenzoic acid (IBX) and its analogs. The magnitudes of different stabilizing effects and further candidates for analogous stabilization are analyzed.      

Should you form a group?

In this discussion, greatest emphasis has been placed upon the personal factors involved, rather than upon the mechanical aspects of creating and maintaining a group, since it is the personal factors, the authors say, that are the most often overlooked.     

Preparation of 3β,16β-dihydroxyandrost-5-en-17-one: Stabilization of its α-ketolic group toward alkali by formation of a semicarbazone

Alkaline hydrolysis of a 16β-acetoxy-17-oxo steroid is accompanied by almost complete rearrangement of the product to a 16-oxo-17β-hydroxy steroid. Hydrolysis can be achieved without rearrangement by 1) formation of a C-17 semicarbazone, 2) alkaline removal of the acetate group, and 3) removal of the semicarbazone group in the presence of pyruvic acid-acetic acid. By employing this technique, the title compound was obtained from its diacetate in a yield of 65%.     

Phosphatocopina – ostracode-like sister group of Eucrustacea

The Phosphatocopina were long considered as the oldest, Cambrian, record of ostracode Crustacea. However, our detailed analysis of more than 2,500 specimens from the Upper Cambrian ‘Orsten’ of Sweden reveals that Phosphatocopina are neither Ostracoda nor Eucrustacea. The antenna and mandible of the phosphatocopines investigated consist of a prominent limb stem which carries a two-segmented endopod and multi-annulated exopod. This stem portion is now recognised as the fusion product of the coxa and basipod during ontogeny. Phosphatocopina share features, such as the coxa and basipod on antennae and mandibles, as well as ventral body structures such as the prominent pre-oral labrum and a single post-oral cephalic plate, the sternum (with paragnaths on the mandibular sternal portion), exclusively with the Eucrustacea. As a plesiomorphy, the ontogeny of Phosphatocopina starts with a ‘head larva’ with four pairs of limbs, a larva type found in the ground pattern of the Euarthropoda as well as the Crustacea. In contrast, eucrustacean ontogeny begins with a nauplius with three pairs of limbs, a ‘short-head larva’ or orthonauplius. Again, the post-mandibular limbs of phosphatocopines retain the plesiomorphic limb design of a basipod with a setiferous ‘ proximal endite’, whereas Eucrustacea, including the Ostracoda, have their first post-mandibular limb differentiated into a ‘ mouthpart’, the maxillula. Autapomorphies of Phosphatocopina include the small antennula with few terminal setae, a bivalved shield with interdorsum, and the fused coxa and basipod on antenna and mandible. We therefore consider the Phosphatocopina to be the sister group of the Eucrustacea. The respective phosphatocopine species of the Upper Cambrian of southern Sweden are restricted to a particular time zone and may be useful as stratigraphic markers.     

Does information sharing promote group foraging?

Individuals may join groups for several reasons, one of which is the possibility of sharing information about the quality of a foraging area. Sharing information in a patch-foraging scenario gives each group member an opportunity to make a more accurate estimate of the quality of the patch. In this paper we present a mathematical model in which we study the effect of group size on patch-leaving policy and per capita intake rate. In the model, group members share information equally in a random search for food. Food is distributed in patches according to a negative binomial distribution. A prediction from our model is that, the larger the group, the earlier each group member should leave the current patch. We also find that the benefit from enhanced exchange of information does not exceed the cost of sharing food with group members. The per capita intake rate decreases as the group size increases. Therefore, animals should only form groups when other factors outweigh the costs, which is easiest to achieve when the travelling time is short.     

Experimental studies of group selection: what do they tell us about group selection in nature?

The study of group selection has developed along two autonomous lines. One approach, which we refer to as the adaptationist school, seeks to understand the evolution of existing traits by examining plausible mechanisms for their evolution and persistence. The other approach, which we refer to as the genetic school, seeks to examine how currently acting artificial or natural selection changes traits within populations and focuses on current evolutionary change. The levels of selection debate lies mainly within the adaptationist school, whereas the experimental studies of group selection lie within the genetic school. Because of the very different traditions and goals of these two schools, the experimental studies of group selection have not had a major impact on the group selection debate. We review the experimental results of the genetic school in the context of the group selection controversy and address the following questions: Under what conditions is group selection effective? What is the genetic basis of a response to group selection? How common is group selection in nature?     

Dose-dependent increase in repair of 1-β-d-arabinofuranosylcytosinedetectable DNA lesions in UV-treated xeroderma pigmentosum (group A) fibroblasts

The extent of DNA-excision repair was determined in human fibroblast strains from clinically normal and xeroderma pigmentosum complementation group A (XP-A) donors after irradiation with 254-nm ultraviolet (UV) light. Repair was monitored by the use of 1-β-d-arabinofuranosylcytosine (araC), a potent inhibitor of DNA synthesis, and alkaline sucrose velocity sedimentation to quantitate DNA single-strand breaks. In this approach, the number of araC-accumulated breaks in post-UV incubated cultures becomes a measure of the efficiency of a particular strain to perform long-patch excision repair. The maximal rate of removal of araC-detectable DNA lesions equalled ∼ 1.8 sites/10⁸ dalton/h in the normal strains (GM38, GM43), while it was more than 10-fold lower in both XP-A strains (XP4LO, XP12BE) examined. In normal fibroblasts the number of lesions removed during the first 4 h after irradiation saturated at ∼ 10 J/m². In contrast, the residual amount of repair in the excision-deficient cells increased as a linear function of UV fluence over a range 5–120 J/m². Thus we conclude that the repair of araC-detectable UV photoproducts in XP group A fibroblasts is limited by availability of damaged regions in the genome to repair complexes.     

adjuvant chemotherapy group, 56 patients received a

1%,26.6% and 27.7% respectively.there was no significant discrepancy(P>0.05).The 5-year survival in 3 or 4 cycles patients were 26.7% and the 5-year survival in 5 or 6 cycles patients were 28.9% .there was no significant discrepancy(P>0.05).Conclusion:Postoperative adjuvant chemotherapy with platinum-based regimen for 3 or 4 cycles can improve survival rate for stage Ⅲ NSCLC patients.Non-small-cell lung cancer; Surgery; Adjuvant chemotherapy; Survival rate0临床肿瘤学杂志Chinese Clinical Oncology19-21R734.2E0724E;E072_4潘泓;173-175长春瑞滨联合卡铂治疗老年晚期非小细胞肺癌胡兴胜;张湘茹;储大同; 中国医学科学院     

Controlled group designs in biofeedback research: Ask, “what does the control group control for?”

The extant literature on the specific role of biofeedback in promoting skeletal muscular relaxation is reviewed and found deficient with respect to the use of properly controlled group outcome research. The review emphasizes the failure of commonly used control procedures to adequately control a number of potentially confounding variables. Strengths and weaknesses of three types of controlled group design (attention placebo, pseudofeedback, and altered contingency) are discussed with respect to their relative usefulness in controlling certain nonspecific or placebo effects in biofeedback research. Many published biofeedback studies failed to measure the credibility of control procedures or the subject's ability to discriminate different feedback contingencies. The studies reviewed suggest that the various control procedures used are not inert and are not equivalent with respect to their effects on control group behavior. The suggestion is made that the controlled group outcome design be accepted as the minimum requirement for testing the specific effects of biofeedback, and possible methods for improving control procedures are discussed.     

Role of hydroxyl group on the mesomorphism of alkyl glycosides: synthesis and thermal behavior of alkyl 6-deoxy-β-d-glucopyranosides

A homologous series of alkyl 6-deoxy-β-d-glucopyranoside amphiphiles was prepared, in an effort to identify the role of hydroxyl group in the mesomorphic behavior of alkyl glycosides. Synthesis was performed by a chlorination of the sugar moiety in alkyl β-d-glucopyranosides with methylsulfonyl chloride in DMF, followed by a metal mediated dehalogenation to secure alkyl 6-deoxy-β-d-glucopyranosides, wherein the alkyl chain length varied from C₉ to C₁₆. The mesomorphic behavior of these 6-deoxy alkyl glycosides was assessed using polarizing optical microscopy, differential scanning calorimetry and X-ray diffraction method. Whereas the lower homologues exhibited a monotropic SmA phase till sub-ambient temperatures, the higher homologues formed a plastic phase. A partial interdigitized bilayer structure of SmA phase is inferred from experimental d-spacing and computationally derived lengths of the molecules. The results were compared with those of normal alkyl glucopyranosides, retained with hydroxyl groups at C-2–C-6 carbons, and alkyl 2-deoxy-glucopyranosides, devoid of a hydroxyl group at C-2 and the comparison showed important differences in the mesomorphic behavior.     

Are polycomb group bodies gene silencing factories?

Polycomb group (PcG) proteins mediate long-range associations between Hox genes, which correlate with gene repression in vivo. Bantignies et al. (2011) identify a physiological role for the nuclear localization of Hox genes in PcG-mediated gene silencing, strengthening the evidence that nuclear positioning regulates gene expression.     

A 3-hydroxy β-end group in xanthophylls is preferentially oxidized to a 3-oxo ε-end group in mammals

We previously found that mice fed lutein accumulated its oxidative metabolites (3′-hydroxy-ε,ε-caroten-3-one and ε,ε-carotene-3,3′-dione) as major carotenoids, suggesting that mammals can convert xanthophylls to keto-carotenoids by the oxidation of hydroxyl groups. Here we elucidated the metabolic activities of mouse liver for several xanthophylls. When lutein was incubated with liver postmitochondrial fraction in the presence of NAD⁺, (3′R,6′R)-3′-hydroxy-β,ε-caroten-3-one and (6RS,3′R,6′R)-3′-hydroxy-ε,ε-caroten-3-one were produced as major oxidation products. The former accumulated only at the early stage and was assumed to be an intermediate, followed by isomerization to the latter. The configuration at the C3′ and C6′ of the ε-end group in lutein was retained in the two oxidation products. These results indicate that the 3-hydroxy β-end group in lutein was preferentially oxidized to a 3-oxo ε-end group via a 3-oxo β-end group. Other xanthophylls such as β-cryptoxanthin and zeaxanthin, which have a 3-hydroxy β-end group, were also oxidized in the same manner as lutein. These keto-carotenoids, derived from dietary xanthophylls, were confirmed to be present in plasma of normal human subjects, and β,ε-caroten-3′-one was significantly increased by the ingestion of β-cryptoxanthin. Thus, humans as well as mice have oxidative activity to convert the 3-hydroxy β-end group of xanthophylls to a 3-oxo ε-end group.     

A practical synthesis of N α -Fmoc protected l-threo-β-hydroxyaspartic acid derivatives for coupling via α- or β-carboxylic group

Abstract  

A simple and practical general synthetic protocol towards orthogonally protected tHyAsp derivatives fully compatible with Fmoc solid-phase peptide synthetic methodology is reported. Our approach includes enantioresolution of commercially available d,l-tHyAsp racemic mixture by co-crystallization with l-Lys, followed by ion exchange chromatography yielding enantiomerically pure l-tHyAsp and d-tHyAsp, and their selective orthogonal protection. In this way N ^α -Fmoc protected tHyAsp derivatives were prepared ready for couplings via either α- or β-carboxylic group onto the resins or the growing peptide chain. In addition, coupling of tHyAsp via β-carboxylic group onto amino resins allows preparation of peptides containing tHyAsn sequences, further increasing the synthetic utility of prepared tHyAsp derivatives.     

Cancer-retina antigens — A new group of tumor antigens

Some photoreceptor proteins normally specific for the eye retina are aberrantly expressed in malignant tumors. These proteins include recoverin, visual rhodopsin, transducin, cGMP-phosphodiesterase 6 (PDE 6), cGMP-dependent cationic channels, guanylyl cyclase 1, rhodopsin kinase, and arrestin. By analogy with cancer-testis antigens, these photoreceptor proteins form the group of cancer-retina antigens. It is shown that an aberrant demethylation of the promoter region of recoverin is involved in the aberrant expression of this protein. The cascade Wnt5a → Frizzled-2 → transducin → PDE 6 is shown to function in skin melanoma cells, and this suggests that these cancer-retina antigens can play a functional role. The events accompanying the signal transduction in this cascade, including those involving calcium ions and cGMP-dependent protein kinase (protein kinase G), are discussed.     

Within‐ and across‐group dating in Hawaii

Abstract

224 subjects from 5 different racial/ethnic groups responded to a dating questionnaire. There are both sex and racial/ethnic differences in frequency of cross‐ethnic dating in Hawaii and in attitudes (as reported by Ss) of parents and close friends toward within‐and across‐ethnic dating. Females date within their own groups more frequently than males and also report stronger support of within‐ and lesser support of across‐group dating by significant others. Racial/ethnic differences are substantial, with groups higher in mean income being more supportive of within‐group dating, being more accepted by other groups, and being less accepting of dating other groups. Amount of actual intergroup dating was related, in part, to group differences in income, with the two groups lowest in income (Filipinos and Hawaiians/Part Hawaiians) showing the highest amount of cross‐ethnic dating, but with the association breaking down in the upper income groups, possibly because of group differences in group size and in length of residence. The results are remarkably similar to those reported earlier on within‐ and across‐group marriage in Hawaii.     

Why do male chimpanzees defend a group range?

Male chimpanzees, Pan troglodytes, cooperate to defend a community range within which resident females range in smaller core areas. There has been debate over exactly what males are defending, whether mates, territory or both. One hypothesis holds that males are defending mates, and that an increase in community range size will lead directly to the acquisition of more females. However, males frequently attack females as well as males at the edge of the community range. We examined 18 years of observational data on the Gombe chimpanzees to determine the behaviour of males during extragroup encounters, and the consequences of changes in community range size on the number of adult females and indirect measures of food availability. Males were always aggressive to males from other communities, and often attacked adult females, especially those that were not sexually receptive, were older, and/or had more than one offspring. The number of females did not increase with range size, but several measures suggested an increase in food availability with range size. These measures include more time spent in large foraging parties, higher encounter rates with resident females, more encounters with sexually receptive females and higher female reproductive rates. These findings suggest that males defend a feeding territory for their resident females and protect them from sexual harassment. Although a large range may eventually attract more females, this is not an immediate consequence of range expansion. Male number was not correlated with community range size.