Intersectional cytoplasmic hybrids in Nicotiana

Summary Cybrid plants having the nuclear genomes of one species and either or both plastomes and chondriomes of another species were obtained by fusing protoplasts of Nicotiana sylvestris, as recipients, with X-irradiated protoplasts of N. rustica as donors of chloroplasts and mitochondria. Forty-nine flowering plants, derived from 28 calli, were analysed. As expected, they all had N. sylvestris (i.e. recipients) morphology. Chloroplast DNA restriction patterns indicated that 8 and 41 plants had N. rustica and N. sylvestris plastomes, respectively. Some of the plants with either type of plastomes produced sterile pollen but none showed anther malformation typical to alloplasmic male sterility. Chondriome identification by mitochondrial DNA restriction analysis of cybrid plants revealed only restriction patterns which were either similar or identical to those of N. sylvestris while no cybrids with N. rustica restriction patterns were detected.     

Isolation of two cDNA clones from tomato containing two different superoxide dismutase sequences

A cDNA library was derived from the poly(A)⁺ RNA of young tomato leaves. The library was cloned in a gt11 system and screened by synthetic oligonucleotide probes having sequences that match the codes of conserved regions of amino acid sequences of Cu,Zn superoxide dismutase (SOD) proteins from a wide range of eukaryotic organisms. Two cDNAs were isolated, cloned and sequenced. One of the cDNAs, P31, had a full-size open reading frame of 456 bp with a deduced amino acid sequence having an 80% homology with the deduced amino acid sequence of the cytosolic SOD-2 cDNA of maize. The other cDNA, T10 (extended by T1), had a 651 bp open reading frame that revealed, upon computer translation, 90% homology to the amino acid sequence of mature spinach chloroplast SOD. The 5 end of the reading frame seems to code for a putative transit peptide. This work thus suggests for the first time an amino acid sequence for the transit peptide of chloroplast SOD. Northern hybridizations indicated that each of the P31 and T10 clones hybridized to a blotted poly(A)⁺ RNA species. These two species are differentially expressed in the plant organs: e.g., the species having the T10 sequence was detected in the leaves but not in roots, while the one with the P31 sequence was expressed in both leaves and roots. The cDNA clones P31 and T10 were also hybridized to Southern blots of endonuclease fragmented tomato DNA. The clones hybridized to specific fragments and no cross hybridization between the two clones was revealed under stringent hybridization conditions; the hybridization pattern indicated that, most probably, only one locus is coding for each of the two mRNA species.     

Seroprevalence of Helicobacter pylori and Length of Stay in a Nursing Home

Background. Helicobacter pylori infection appears to be contracted mainly in childhood, and it is associated with disadvantaged socioeconomic conditions, overcrowding, and living in institutions. In this study we determined the seroprevalence of H. pylori among elderly patients (age ≥ 70 years) admitted to a major medical center in Israel, and studied the relationship between seroprevalence of H. pylori and the duration of stay in a nursing home prior to the admission.
Patients and Methods. Whole blood from 182 consecutive patients hospitalized at the Rabin Medical Center was tested for the presence of anti- H. pylori IgG using Helisal Rapid Blood Test kit (Cortecs Diagnostics). Multivariate logistic regression analysis was used to study the relation between H. pylori seropositivity and possible predictive factors such as age, gender and duration of stay in a nursing home.
Results. Of the 182 patients included in the study, 80 (44%) were living in nursing homes (NH) and 102 (56%) were living in their own homes (H) prior to admission. Subjects that stayed in nursing homes for more than 15 months were significantly more likely to be seropositive than subjects with a shorter duration of stay (84% and 63% respectively, p = 0.03). Using a multivariate logistic regression analysis on both the NH group and the whole group, seropositivity was found to be significantly associated with duration of stay in a nursing home (  p = 0.03 and p = 0.01 respectively). Seropositivity was not associated with age in either group.
Conclusions. Living in a nursing home is associated with increased risk for H. pylori infection in the elderly. There is a strong correlation between the duration of stay in a nursing home and the prevalence of H. pylori infection.     

A NEW METHOD FOR THE ESTIMATION OF CELL CYCLE PHASES

A method is described, which is applicable to cell renewal systems with an anatomical structure in which all cell locations may be uniquely mapped. Its use is demonstrated on the rat incisor inner enamel epithelium, which forms a one cell thick column in the sagittally sectioned tooth. Cells born in the apical part of the column migrate toward the distal end of the tooth, where they mature. As the cells migrate along the column, they traverse the various cell cycle phases. The present study has been designed to estimate the probability of a cell being in a given phase; all cells touching the basement membrane were numbered, and the number of cells separating any two cells was taken as a measure of distance. Since generally all cells move in one direction (lateral cell migration may occur), it is possible to solve the problem with the aid of functions describing the renewal counting stochastic process in which cell distance serves as an independent variable. The method predicts labelled cell and mitotic rates which agree with those estimated in the usual way. It was then utilized to estimate the fraction of cells in G₂.     

Small and Large Ribosomal Subunit Deficiencies Lead to Distinct Gene Expression Signatures that Reflect Cellular Growth Rate

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A Role for the Juxtamembrane Cytoplasm in the Molecular Dynamics of Focal Adhesions

Focal adhesions (FAs) are specialized membrane-associated multi-protein complexes that link the cell to the extracellular matrix and play crucial roles in cell-matrix sensing. Considerable information is available on the complex molecular composition of these sites, yet the regulation of FA dynamics is largely unknown. Based on a combination of FRAP studies in live cells, with in silico simulations and mathematical modeling, we show that the FA plaque proteins paxillin and vinculin exist in four dynamic states: an immobile FA-bound fraction, an FA-associated fraction undergoing exchange, a juxtamembrane fraction experiencing attenuated diffusion, and a fast-diffusing cytoplasmic pool. The juxtamembrane region surrounding FAs displays a gradient of FA plaque proteins with respect to both concentration and dynamics. Based on these findings, we propose a new model for the regulation of FA dynamics in which this juxtamembrane domain acts as an intermediary layer, enabling an efficient regulation of FA formation and reorganization.     

RNA Editing Genes Associated with Extreme Old Age in Humans and with Lifespan in C. elegans

Background

The strong familiality of living to extreme ages suggests that human longevity is genetically regulated. The majority of genes found thus far to be associated with longevity primarily function in lipoprotein metabolism and insulin/IGF-1 signaling. There are likely many more genetic modifiers of human longevity that remain to be discovered.

Methodology/Principal Findings

Here, we first show that 18 single nucleotide polymorphisms (SNPs) in the RNA editing genes ADARB1 and ADARB2 are associated with extreme old age in a U.S. based study of centenarians, the New England Centenarian Study. We describe replications of these findings in three independently conducted centenarian studies with different genetic backgrounds (Italian, Ashkenazi Jewish and Japanese) that collectively support an association of ADARB1 and ADARB2 with longevity. Some SNPs in ADARB2 replicate consistently in the four populations and suggest a strong effect that is independent of the different genetic backgrounds and environments. To evaluate the functional association of these genes with lifespan, we demonstrate that inactivation of their orthologues adr-1 and adr-2 in C. elegans reduces median survival by 50%. We further demonstrate that inactivation of the argonaute gene, rde-1, a critical regulator of RNA interference, completely restores lifespan to normal levels in the context of adr-1 and adr-2 loss of function.

Conclusions/Significance

Our results suggest that RNA editors may be an important regulator of aging in humans and that, when evaluated in C. elegans, this pathway may interact with the RNA interference machinery to regulate lifespan.