Lower Neighborhood Socioeconomic Status Associated with Reduced Diversity of the Colonic Microbiota in Healthy Adults

In the United States, there are persistent and widening socioeconomic gaps in morbidity and mortality from chronic diseases. Although most disparities research focuses on person-level socioeconomic-status, mounting evidence suggest that chronic diseases also pattern by the demographic characteristics of neighborhoods. Yet the biological mechanisms underlying these associations are poorly understood. There is increasing recognition that chronic diseases share common pathogenic features, some of which involve alterations in the composition, diversity, and functioning of the gut microbiota. This study examined whether socioeconomic-status was associated with alpha-diversity of the colonic microbiota. Forty-four healthy adults underwent un-prepped sigmoidoscopy, during which mucosal biopsies and fecal samples were collected. Subjects’ zip codes were geocoded, and census data was used to form a composite indicator of neighborhood socioeconomic-status, reflecting household income, educational attainment, employment status, and home value. In unadjusted analyses, neighborhood socioeconomic-status explained 12–18 percent of the variability in alpha-diversity of colonic microbiota. The direction of these associations was positive, meaning that as neighborhood socioeconomic-status increased, so did alpha-diversity of both the colonic sigmoid mucosa and fecal microbiota. The strength of these associations persisted when models were expanded to include covariates reflecting potential demographic (age, gender, race/ethnicity) and lifestyle (adiposity, alcohol use, smoking) confounds. In these models neighborhood socioeconomic-status continued to explain 11–22 percent of the variability in diversity indicators. Further analyses suggested these patterns reflected socioeconomic variations in evenness, but not richness, of microbial communities residing in the sigmoid. We also found indications that residence in neighborhoods of higher socioeconomic-status was associated with a greater abundance of Bacteroides and a lower abundance of Prevotella, suggesting that diet potentially underlies differences in microbiota composition. These findings suggest the presence of socioeconomic variations in colonic microbiota diversity. Future research should explore whether these variations contribute to disparities in chronic disease outcomes.     

Cytokinin metabolism in tomato plants. II. Metabolites of kinetin and benzyladenine in decapitated roots

Decapitated tomato plants were supplied via the roots with [8-¹⁴C]-kinetin or [8-¹⁴C]-benzyladenine in a nutrient solution for a period of 24 h. After this time the root material, the root sap produced during the 24 h period and the nutrient solution remaining at the end of the experiments were analysed for cytokinins. HPLC techniques and chemical treatments were used to tentatively identify radioactive metabolites formed. Uptake of kinetin and benzyladenine by the roots was found to be limited but once within the root tissues metabolism was both rapid and extensive.At least 14 metabolites of kinetin were recovered from root tissue and root sap. Many of these appeared to be degradation products. There was, however, some evidence of formation of zeatin-like derivatives. Side-chain cleavage of the original kinetin which occurs rapidly is suggested as a possible route for the eventual production of these endogenous cytokinin forms.The benzyladenine taken up by the roots was apparently both ribosylated and glucosylated. No unmetabolized benzyladenine was detected in the root tissues after 24 h. Only very low levels of radioactivity were associated with the retention time of adenine, suggesting that in the case of benzyladenine side-chain cleavage is of limited importance.The significance of these reactions in relation to the potential use of cytokinins in the regulation of plant growth is discussed.     

Evolution of the 28S ribosomal RNA gene in anurans: regions of variability and their phylogenetic implications

Fifteen restriction sites were mapped to the 28S ribosomal RNA gene of individuals representing 54 species of frogs, two species of salamanders, a caecilian, and a lungfish. Eight of these sites were present in all species examined, and two were found in all but one species. Alignment of these conserved restriction sites revealed, among anuran 28S rRNA genes, five regions of major length variation that correspond to four of 12 previously identified divergent domains of this gene. One of the divergent domains (DD8) consists of two regions of length variation separated by a short segment that is conserved at least throughout tetrapods. Most of the insertions, deletions, and restriction-site variations identified in the 28S gene will require sequence-level analysis for a detailed reconstruction of their history. However, an insertion in DD9 that is coextensive with frogs in the suborder Neobatrachia, a BstEII site that is limited to representatives of two leptodactylid subfamilies, and a deletion in DD10 that is found only in three ranoid genera are probably synapomorphies.      

Neutron fibre diffraction study of DNA hydration

Interactions with water are crucial to the conformation assumed by the DNA double helix. The location of water around the D conformation has been investigated in a neutron fibre diffraction study which shows that water is ordered in the minor groove of the DNA. The D conformation is important since its occurrence is limited to specific DNA base pair sequences which have been identified as functionally significant. This study is of particular interest because the D conformation has not been reported in single crystal studies of oligonucleotides.     

Characterization of cross-bridge elasticity and kinetics of cross-bridge cycling during force development in single smooth muscle cells

Force development in smooth muscle, as in skeletal muscle, is believed to reflect recruitment of force-generating myosin cross-bridges. However, little is known about the events underlying cross-bridge recruitment as the muscle cell approaches peak isometric force and then enters a period of tension maintenance. In the present studies on single smooth muscle cells isolated from the toad (Bufo marinus) stomach muscularis, active muscle stiffness, calculated from the force response to small sinusoidal length changes (0.5% cell length, 250 Hz), was utilized to estimate the relative number of attached cross-bridges. By comparing stiffness during initial force development to stiffness during force redevelopment immediately after a quick release imposed at peak force, we propose that the instantaneous active stiffness of the cell reflects both a linearly elastic cross-bridge element having 1.5 times the compliance of the cross-bridge in frog skeletal muscle and a series elastic component having an exponential length-force relationship. At the onset of force development, the ratio of stiffness to force was 2.5 times greater than at peak isometric force. These data suggest that, upon activation, cross-bridges attach in at least two states (i.e., low-force-producing and high-force-producing) and redistribute to a steady state distribution at peak isometric force. The possibility that the cross-bridge cycling rate was modulated with time was also investigated by analyzing the time course of tension recovery to small, rapid step length changes (0.5% cell length in 2.5 ms) imposed during initial force development, at peak force, and after 15 s of tension maintenance. The rate of tension recovery slowed continuously throughout force development following activation and slowed further as force was maintained. Our results suggest that the kinetics of force production in smooth muscle may involve a redistribution of cross-bridge populations between two attached states and that the average cycling rate of these cross-bridges becomes slower with time during contraction.     

A direct fuel cell for the production of electricity from lignin

This report describes the use of an anthraquinone mediated fuel cell for the direct production of electrical energy from sulfonated lignin and Kraft Black Liquor. The cell produces the equivalent of 1 kWh for each 2-3 lb sulfonated lignin and 5-8 lb black liquor combustibles. In the case of the sulfonated lignin, chain session occurs during the oxidation process, reducing the molecular weight from ca. 2 x 10(4) to less than 1000 D.     

Metabolism of kinetin by soybean callus

Soybean callus metabolised applied 6-furfurylamino (8^-14C) purine very rapidly to polar compounds, some of which were retained on a Dowex 50 cation exchange resin, and were unaffected by alkaline phosphatase; while others were apparently phosphorylated and were detected in the aqueous fraction. Adenine was detected as an intermediate and it can be concluded that it was formed as a result of the rapid and efficient removal of the furfuryl side chain. The formed adenine was rapidly incorporated into the polar metabolites. Exactly how the presence of this cytokinin stimulates cell division is not apparent from the results.The financial support of the C.S.I.R., Pretoria, and The Natal University Development Fund is gratefully acknowledged.     

Chromosome size polymorphisms in Plasmodium falciparum can involve deletions and are frequent in natural parasite populations

A comparison of independent cultured isolates of Plasmodium falciparum revealed that while chromosome number was constant, the sizes of analogous chromosomes varied widely. We show here that chromosome size polymorphisms are not generated during differentiation of the asexual blood stages, as the molecular karyotype of a cloned parasite line is constant through this part of the life cycle. Experiments using whole P. falciparum chromosomes as hybridization probes to examine polymorphisms within two independent parasite populations indicate that the polymorphisms observed here are not the consequence of large-scale interchromosomal exchanges, and imply that deletions/duplications represent one mode of generating chromosome length polymorphisms. Although the deletions probably involve repetitive DNA, we show here that structural genes for P. falciparum antigens can also be lost. Furthermore, these dramatic size polymorphisms occur not only in cultured lines of P. falciparum, but with surprising frequency in natural malarial infections.