A resonant sextuplet of sub-Neptunes transiting the bright star HD 110067.

Planets with radii between that of the Earth and Neptune (hereafter referred to as 'sub-Neptunes') are found in close-in orbits around more than half of all Sun-like stars1,2. However, their composition, formation and evolution remain poorly understood3. The study of multiplanetary systems offers an opportunity to investigate the outcomes of planet formation and evolution while controlling for initial conditions and environment. Those in resonance (with their orbital periods related by a ratio of small integers) are particularly valuable because they imply a system architecture practically unchanged since its birth. Here we present the observations of six transiting planets around the bright nearby star HD 110067. We find that the planets follow a chain of resonant orbits. A dynamical study of the innermost planet triplet allowed the prediction and later confirmation of the orbits of the rest of the planets in the system. The six planets are found to be sub-Neptunes with radii ranging from 1.94R⊕ to 2.85R⊕. Three of the planets have measured masses, yielding low bulk densities that suggest the presence of large hydrogen-dominated atmospheres.

Cellular specificity and replication rate of Maedi Visna virus in vitro can be controlled by LTR sequences.

The long terminal repeats (LTR) sequence divergence among Maedi Visna virus (MVV) isolates leads to LTRs with distinct transcriptional activities, which may result in distinct biological behaviours. The genetic heterogeneity, as well as basal and Tat-induced transcriptional activity of the LTRs from P1OLV and WLC-1 MVV viruses, slow/low and rapid/high isolates, respectively, have been examined and compared with LTRs from other strains of small ruminant lentiviruses (SRLV). Transfection assays using a reporter construct containing the LTR fused to a luciferase gene demonstrated that the LTR from P1OLV virus had the weakest promoter activity, suggesting a correlation between the level of promoter activity and the viral replication rate. To confirm this hypothesis, the promoter of P1OLV was cloned into infectious molecular clone KV1772kv72/67 and the resulting chimeric virus was tested for growth in various cell types. Compared to the parental KV1772, the LTR-chimeric virus KV1772/P1OLV exhibited a drastic reduction in replication rate in sheep choroid plexus (SCP) and lung cells, while in ovine macrophages and goat synovial membrane cells (GSM), chimeric virus showed a growth rate similar to that of parental virus. These observations suggest that the LTR is responsible for the slow/low in vitro phenotype presented by P1OLV in SCP and lung cells.

Avaliação produtiva e econômica de sistemas de produção bovina em pastagens de capim-elefante / Productive and economic evaluation of cattle production systems on elephant-grass pastures

Avaliou-se o desempenho produtivo de novilhas manejadas em capim-elefante com suplementação alimentar e estudou-se a viabilidade econômica dos sistemas de produção. Utilizaram-se novilhas Holandês-Zebu com idade média de 17 meses e peso médio de 215±8kg, distribuídas nos seguintes sistemas de produção: SP1 - sem suplementação; SP2 - suplementadas com ração concentrada; e SP3 - suplementadas com leguminosa Stylosanthes guianensis, cv. Mineirão. Foram utilizadas 22 novilhas sendo 12 distribuídas nos três sistemas e as demais utilizadas como animais de equilíbrio em função da quantidade de forragem disponível. Os ganhos de peso médio diário foram 429±18g, 624±23g e 535±8g para SP1, SP2 e SP3, e os ganhos de peso diário por área de 2,38; 3,46 e 1,43kg/ha/dia, para SP1, SP2 e SP3, respectivamente. A taxa interna de retorno obtida foi 29,6 por cento, 30,1 por cento e 10,5 por cento para SP1, SP2 e SP3, respectivamente. O preço de venda das novilhas foi o fator de maior impacto no desempenho econômico dos sistemas de produção.