Shared behavioral mechanisms underlie C. elegans aggregation and swarming.

In complex biological systems, simple individual-level behavioral rules can give rise to emergent group-level behavior. While collective behavior has been well studied in cells and larger organisms, the mesoscopic scale is less understood, as it is unclear which sensory inputs and physical processes matter a priori. Here, we investigate collective feeding in the roundworm C. elegans at this intermediate scale, using quantitative phenotyping and agent-based modeling to identify behavioral rules underlying both aggregation and swarming-a dynamic phenotype only observed at longer timescales. Using fluorescence multi-worm tracking, we quantify aggregation in terms of individual dynamics and population-level statistics. Then we use agent-based simulations and approximate Bayesian inference to identify three key behavioral rules for aggregation: cluster-edge reversals, a density-dependent switch between crawling speeds, and taxis towards neighboring worms. Our simulations suggest that swarming is simply driven by local food depletion but otherwise employs the same behavioral mechanisms as the initial aggregation.

Perfil epidemiológico da hanseníase no período de 2009 a 2013 no município de Montes Claros (MG) / Epidemiological profile of leprosy in the period 2009 to 2013 in thecity Montes Claros (MG), Brazil

OBJETIVO: Avaliar o perfil epidemiológico da hanseníase nomunicípio de Montes Claros (MG), no período de 2009 a 2013.MÉTODOS: Trata-se de um estudo observacional, retrospectivocom variáveis quantitativas em que os dados foram extraídosda ficha de notificação/investigação de hanseníase do Sistema deInformação de Agravos de Notificação (SINAN). RESULTADOS:oram notificados 230 casos durante o período estudado.Observou-se a predominância de casos no sexo masculino e dacor parda, sendo que o grau zero de incapacidade foi detectadoem 79,56% dos pacientes. A maioria era multibacilar, pertencenteprincipalmente às formas clínicas dimorfa e virchowiana.CONCLUSÃO: Nos últimos anos, houve uma redução expressivano número de casos da hanseníase na população estudada,sendo atingida a meta proposta pela Organização Mundial daSaúde nos anos de 2012 e 2013. Para que esse índice seja sustentadonos próximos anos, é necessário que as campanhas deconscientização, a busca ativa de casos, e o tratamento precoce eeficaz sejam trabalhados e mantidos.(AU)

OBJECTIVE: To evaluate the epidemiological profile ofhanseniasis in Montes Claros (MG), Brazil, from 2009 up to2013. METHODS: n observational, retrospective study withquantitative variables showing data which were obtained from the record files dealing with notification and investigationabout hanseniasis from the Sistema de Informação de Agravosde Notificação (SINAN). RESULTS: A total of 230 caseswere reported during the studied period. We observed thepredominance of cases in males and mulatto, whereas the zerodegree of disability was detected in 79.56% of the patients,the majority of them being multibacillar, belonging mainly todimorphal and the virchowiana clinical forms. CONCLUSION:In the last years an significant reduction in the number ofhanseniasis cases in the studied population was evident. Thedesirable goal proposed by World Health Organization wasattained in the years 2012 and 2013. For this reason, in order tomaintain this index in the coming years, it is necessary to keepthe awareness campaigns, the active search for positive cases, aswell as the early and effective treatment.(AU)

Direct potable reuse of reclaimed wastewater: it is time for a rational discussion.

Water shortage arising from rapid population growth and relocation has produced an unprecedented degree of stress on regional water resources. Engineered solutions to relieve water stress are frequently based on the use of water of impaired initial quality. Chief among these impaired waters is reclaimed wastewater. For the most part, however, the breadth of both acceptable uses and use-dependent degree of treatment for reclaimed wastewater remain to be established.The chief advantages of direct potable reuse (DPR) relative to other forms of wastewater reclamation and reuse are that(i) all wastewater reclaimed for DPR can be readily used in water-stressed areas and (ii) delivery to points of use does not require a separate distribution system. The drawbacks are related to the need for highly competent, continuous on-line verification of water quality and the cost of treating all reclaimed wastewater to meet potable use requirements when only a small fraction will be used for potable purposes.We have attempted to explore those differences, providing quantitative comparisons where possible, to support selection among water reuse options in water-stressed areas.

Mechanisms of chromosome banding. VII. Interaction of methylene blue with DNA and chromatin.

The binding of methylene blue to DNA and chromatin treated in various ways was examined by equilibrium dialysis. The maximum r value (moles of bound dye/mole of nucleotide) was 1.0 for DNA, 0.6 for unfixed chromatin, and 0.83 for chromatin fixed in methanol-acetic acid. When fixed chromatin was treated with saline-citrate at 60 degrees C for 3 hours, as used for G-banding chromosomes, the r value decreased from 0.83 to 0.55. When unfixed chromatin was treated as for R-banding the r values also dropped. Equilibrium dialysis indicated there was no disproportionate increase of dye binding as the concentration of DNA increased. -- These results, and others, suggest that some of the Giemsa negative regions of G- and R-banded chromosomes are due to the denaturation of non-histone proteins so that they more effectively cover the DNA and prevent side binding of the thiazin dyes.

Mechanisms of chromosome banding. V. Quinacrine banding.

A series of biochemical investigations were undertaken to determine the mechanism of Q-banding. The results were as follows: 1. In agreement with previous studies, highly AT-rich DNA, such as poly(dA)-poly(dT), markedly enhanced quinacrine fluorescence while GC containing DNA quenched fluorescence. These effects persisted at DNA concentrations comparable to those in the metaphase chromosome. 2. Studies of quinacrine-DNA complexes in regard to the hypochromism of quanacrine, DNA Tm, DNA viscosity, and equilibrium dialysis, indicated the quinacrine was bound be intercalation with relatively little sid binding. 3. Single or double stranded nucleotide polymers, in the form of complete or partial helices, were 1000-fold more effective in quenching than solutions of single nucleotides, suggesting that base stacking is required for quenching. 4. Studies of polymers in the A conformation, such as transfer RNA and DNA-RNA hybrids, indicated that marked base tilting does not affect the ability of nuclei acids to cause quenching or enhancement of quinacrine fluorescence. 5. Salts inhibit the binding of quinacrine to DNA. 6. Spermine, polylysine and polyarginine, which bind in the small groove of DNA, inhibited quinacrine binding and quenching, while histones, which probably bind in the large groove, had little effect. This correlated with the observation that removal of histones with acid has no effect on Q-banding. 7. Mouse liver chromatin was separated into five fractions. At concentrations of quinacrine from 2 times 10-6 to 2 times 10-5 M all fractions inhibited to varying degrees the ability of the chromatin DNA to bind quinacrine and quench quinacrine fluorescence. At saturating levels of quinacrine two fractions, the 400 g pellet (rich in heterochromatin) and a dispersed euchromatin supernatant fraction, showed a decreased number of binding sites for quinacrine. These two fractions were also the richest in non-histone proteins. 8. DNA isolated from the different fractions all showed identical quenching of quinacrine fluorescenc. 9. Mouse GC-rich, mid-band, AT-rich, and satellite DNA, isolated by CsCL AND Cs-2SO-4-Ag+ centrifugation all showed identical quenching of quinacrine fluorescence, indicating that within a given organism, except for very AT or GC-rich satellites, the variation in base composition is not adequate to explain Q-banding. We interpret these results to indicate that: (a) quinacrine binds to chromatin by intercalation of the three planar rings with the large group at position 9 lying in the small groove of DNA, (b) most pale staining regions are due to a decrease binding of quinacrine, and (c) this inhibition of binding is predominately due to non-histone proteins.