NMR detection of structures in the HIV-1 5'-leader RNA that regulate genome packaging

The 5'-leader of the HIV-1 genome regulates multiple functions during viral replication via mechanisms that have yet to be established. We developed a nuclear magnetic resonance approach that enabled direct detection of structural elements within the intact leader (712-nucleotide dimer) that are critical for genome packaging. Residues spanning the gag start codon (AUG) form a hairpin in the monomeric leader and base pair with residues of the unique-5' region (U5) in the dimer. U5:AUG formation promotes dimerization by displacing and exposing a dimer-promoting hairpin and enhances binding by the nucleocapsid (NC) protein, which is the cognate domain of the viral Gag polyprotein that directs packaging. Our findings support a packaging mechanism in which translation, dimerization, NC binding, and packaging are regulated by a common RNA structural switch.     

The Efficacy and Residual Toxicity of certain Granular Insecticides against Mustard Aphid,Lipaphis erysimi (Kalt)

Abstract

The systemic activity of four granular insecticides (phorate 10%, Temik 10%, diazinon 5% and Sevidol [8% carbaryl + 8% gamma-BHC]) was evaluated for the control of mustard aphid, Lipaphis erysimi (Kalt). The granules were applied in the soil to one month old mustard plants transplanted in pots. 3rd and 4th instar nymphs were used for the trial. Mortality counts were made 24 hours after release. Of the insecticides tested, phorate and Temik at 1 lb a.i./ac proved most effective. Temik had a quick knockdown effect as compared to phorate, as it gave 100% control within 24 hours, while with phorate 100% kill was obtained only after 72 hours. Diazinon at 4 lb a.i./ac gave 83.3% kill after 72 hours. Sevidol proved ineffective as an aphidicide. Residual toxicity of three of the granular insecticides, namely phorate, Temik and diazinon, was tested. Phorate and Temik at 1 lb a.i./ac exhibited the same residual toxicity up to 4 weeks, i.e. 100% and 76% kill obtained at the end of 2 and 4 weeks respectively. Although the toxicity of both pesticides gradually declined there was no significant difference in percentage kill over a period of 5 weeks. After 6 weeks, however, the mortality recorded with Temik was 37.1% and with phorate was 51.1%. The residual toxicity of phorate was further found to last up to 8 weeks, when the mortality obtained was 40%. The residual toxicity of diazinon sharply declined within 2 weeks.     

Seed Priming Influence on Early Crop Growth,Phenological Development and Yield Performance of Linola (Linum usitatissimum L.)

Reduced early crop growth and limited branching are amongst yield limiting factors of linola. Field response of seed priming treatments viz. 50 mmol L⁻¹ salicylic acid (SA), 2.2% CaCl₂ and 3.3% moringa leaf extract (MLE) including untreated dry and hydropriming controls was evaluated on early crop growth and yield performance of linola. Osmopriming with CaCl₂ reduced emergence time and produced the highest seedling fresh and dry weights including Chl. a contents. Osmopriming with CaCl₂ reduced crop branching and flowering and maturity times and had the maximum plant height, number of branches, tillers, pods and seeds per pod followed by MLE. Increase in seed weight, biological and seed yields was 9.30, 34.16 and 39.49%, harvest index (4.12%) and oil contents (13.39%) for CaCl₂ osmopriming. Positive relationship between emergence and seedling vigor traits, 100-seed weight, seed yield with maturity time, 100-seed weight and seed yield were found. The study concludes that seed osmopriming with CaCl₂ or MLE can play significant role to improve early crop growth and seed yields of linola.     

Transmission dynamics of the etiological agent of SARS in Hong Kong: impact of public health interventions

We present an analysis of the first 10 weeks of the severe acute respiratory syndrome (SARS) epidemic in Hong Kong. The epidemic to date has been characterized by two large clusters-initiated by two separate "super-spread" events (SSEs)-and by ongoing community transmission. By fitting a stochastic model to data on 1512 cases, including these clusters, we show that the etiological agent of SARS is moderately transmissible. Excluding SSEs, we estimate that 2.7 secondary infections were generated per case on average at the start of the epidemic, with a substantial contribution from hospital transmission. Transmission rates fell during the epidemic, primarily as a result of reductions in population contact rates and improved hospital infection control, but also because of more rapid hospital attendance by symptomatic individuals. As a result, the epidemic is now in decline, although continued vigilance is necessary for this to be maintained. Restrictions on longer range population movement are shown to be a potentially useful additional control measure in some contexts. We estimate that most currently infected persons are now hospitalized, which highlights the importance of control of nosocomial transmission.