Infrequent detection of KI, WU and MC polyomaviruses in immunosuppressed individuals with or without progressive multifocal leukoencephalopathy

Conflicting prevalence of newly identified KI (KIPyV), WU (WUPyV) and Merkel Cell Carcinoma (MCPyV) polyomaviruses have been reported in progressive multifocal leukoencephalopathy (PML) patient samples, ranging from 0 to 14.3%. We analyzed the prevalence of these polyomaviruses in cerebrospinal fluid (CSF), peripheral blood mononuclear cells (PBMC), and bone marrow samples from PML patients, immunosuppressed individuals with or without HIV, and multiple sclerosis (MS) patients. Distinct PCR tests for KIPyV, WUPyV and MCPyV DNA performed in two independent laboratories detected low levels of MCPyV DNA only in 1/269 samples. The infrequent detections of these viruses in multiple samples from immunosuppressed individuals including those with PML suggest that their reactivation mechanisms may be different from that of JC polyomavirus (JCPyV) and that they do not play a role in the pathogenesis of PML.     

Programming microbial population dynamics by engineered cell-cell communication

A major aim of synthetic biology is to program novel cellular behavior using engineered gene circuits. Early endeavors focused on building simple circuits that fulfill simple functions, such as logic gates, bistable toggle switches, and oscillators. These gene circuits have primarily focused on single-cell behaviors since they operate intracellularly. Thus, they are often susceptible to cell-cell variations due to stochastic gene expression. Cell-cell communication offers an efficient strategy to coordinate cellular behavior at the population level. To this end, we review recent advances in engineering cell-cell communication to achieve reliable population dynamics, spanning from communication within single species to multispecies, from one-way sender-receiver communication to two-way communication in synthetic microbial ecosystems. These engineered systems serve as well-defined model systems to better understand design principles of their naturally occurring counterparts and to facilitate novel biotechnology applications.     

RICE MORPHOLOGY DETERMINANT encodes the type II formin FH5 and regulates rice morphogenesis

Multicellular organisms contain a large number of formins; however, their physiological roles in plants remain poorly understood. Here, we reveal that formin homology 5 (FH5), a type II formin mutated in rice morphology determinant (rmd), plays a crucial role in determining rice (Oryza sativa) morphology. FH5/RMD encodes a formin-like protein consisting of an N-terminal phosphatase tensin (PTEN)-like domain, an FH1 domain, and an FH2 domain. The rmd mutants display a bending growth pattern in seedlings, are stunted as adult plants, and have aberrant inflorescence (panicle) and seed shape. Cytological analysis showed that rmd mutants have severe cell elongation defects and abnormal microtubule and microfilament arrays. FH5/RMD is ubiquitously expressed in rice tissues, and its protein localization to the chloroplast surface is mediated by the PTEN domain. Biochemical assays demonstrated that recombinant FH5 protein can nucleate actin polymerization from monomeric G-actin or actin/profilin complexes, cap the barbed end of actin filaments, and bundle actin filaments in vitro. Moreover, FH5 can directly bind to and bundle microtubules through its FH2 domain in vitro. Our findings suggest that the rice formin protein FH5 plays a critical role in determining plant morphology by regulating actin dynamics and proper spatial organization of microtubules and microfilaments.     

Architecture of the active DNA polymerase delta.proliferating cell nuclear antigen.template-primer complex.

The relative positions of components of the DNA-dependent DNA polymerase delta (pol delta).proliferating cell nuclear antigen (PCNA).DNA complex were studied. We have shown that pol delta incorporates nucleotides close to a template biotin-streptavidin complex located 5' (downstream) to the replicating complex in the presence or absence of PCNA. PCNA-dependent synthesis catalyzed by pol delta was nearly totally (95%) inhibited by a biotin. streptavidin complex located at the 3'-end of a template with a 15-mer primer (upstream of the replicating complex), but was only partially inhibited with a 19-mer primer. With either primer, PCNA-independent synthesis was not affected by the biotin. streptavidin complex. Quantification of results with primers of varying length suggested that pol delta interacts with between 8 and 10 nucleotides of duplex DNA immediately proximal to the 3'-OH primer terminus. Using UV photocross-linking, we determined that the 125-kDa subunit of pol delta, but not the 50-kDa subunit, interacted with a photosensitive residue of a substrate oligonucleotide. Interaction apparently takes place through the C terminus of p125. Based on these results, we conclude that PCNA is located "behind" pol delta in the polymerization complex during DNA synthesis and that only the large subunit of pol delta (two-subunit form) interacts directly with DNA. A detailed model of the enzymatically active complex is proposed.     

一种放大凋亡细胞Giemsa染色法及其在抗癌药物研究中的应用

本文介绍了一种用甲醇、冰醋酸、水处理细胞再经Giemsa染色的方法,经该方法处理后,细胞体积增大,凋亡细胞形态尤其胞核结构在普通光学显微镜下非常清晰.采用高三尖杉酯碱诱导四种不同类型肿瘤细胞凋亡,经放大细胞Giemsa染色之后,可获得清晰的不同时期凋亡细胞形态学表现及动态变化特征.进一步用琼脂糖电泳法检测四种细胞的DNA降解程度,结果表明,这种放大细胞的方法比琼脂糖电泳法更适用于形成凋亡小体之前细胞形态学特征的分析,为抗癌药物及细胞凋亡的研究提供了一种直观、准确的方法.     

Distinct human immunodeficiency virus strains in the bone marrow are associated with the development of thrombocytopenia

We analyzed bone marrow and blood from human immunodeficiency virus type 1 (HIV-1)-infected individuals and described the HIV-1 quasispecies in these cellular compartments. HIV-1 isolates from the bone marrow of thrombocytopenic patients contained distinct amino acids in the V3 loop and infected T-cell lines, implicating this virus in the development of thrombocytopenia.     

Optimisation of plantlet regeneration from leaf and nodal derived callus of <Emphasis Type="Italic">Vanilla planifolia</Emphasis> Andrews

An indirect in vitro plant regeneration protocol for Vanilla planifolia has been established. Juvenile leaf and nodal segments from V. planifolia were used as explants to initiate callus. Nodal explants showed better callus initiation than juvenile leaf explants, with 35.0% of explants forming callus when cultured on Murashige and Skoog (MS) basal medium supplemented with 2.0 mg/l 1-naphthylacetic acid (NAA) and 1.0 mg/l 6-benzyladenine (BA). Almost 10.0% of juvenile leaf explants were induced to form callus on the MS basal medium containing 2.0 mg/l NAA and 2.0 mg/l BA, whereas no callus formed in the presence of any concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) and BA. After 8 weeks, callus generated was transferred to MS basal medium containing 1.0 mg/l BA and 0.5 mg/l NAA. A mean number of 4.2 shoots per callus was produced on this medium, with a mean length of 3.8 cm after 8 weeks of culture. Roots formed on 88.3% of plantlets when they were cultured on MS medium supplemented with 1.0 mg/l NAA, with a mean length of 4.4 cm after 4 weeks of culture. Of the rooted plantlets, 90.0% survived acclimatisation and were making new growth after 4 weeks.     

Comparative height crown allometry and mechanical design in 22 tree species of Kuala Belalong rainforest, Brunei, Borneo

In rainforests, trunk size, strength, crown position, and geometry of a tree affect light interception and the likelihood of mechanical failure. Allometric relationships of tree diameter, wood density, and crown architecture vs. height are described for a diverse range of rainforest trees in Brunei, northern Borneo. The understory species follow a geometric model in their diameter-height relationship (slope, β = 1.08), while the stress-elasticity models prevail (β = 1.27-1.61) for the midcanopy and canopy/emergent species. These relationships changed with ontogeny, especially for the understory species. Within species, the tree stability safety factor (SSF) and relative crown width decreased exponentially with increasing tree height. These trends failed to emerge in across-species comparisons and were reversed at a common (low) height. Across species, the relative crown depth decreased with maximum potential height and was indistinguishable at a common (low) height. Crown architectural traits influence SSF more than structural property of wood density. These findings emphasize the importance of applying a common reference size in comparative studies and suggest that forest trees (especially the understory group) may adapt to low light by having deeper rather than wider crowns due to an efficient distribution and geometry of their foliage.