Quantitation of strand breaks in human DNA using 32P-Alu hybridization: application to exponential and plateau-phase cells

A sensitive quantitation of DNA (0.2 to 10 ng) can be achieved using a 32P-labeled Alu probe to hybridize human DNA spotted onto nylon membrane. This allows the determination of radiation-induced single-strand breaks without the use of [3H]thymidine prelabeling of cells in culture. The sensitivity of this technique in HeLa cells is comparable to results obtained using the alkaline unwinding technique. The method is applicable to cells in both exponential and plateau phases of growth.     

Isoaurmillone,an isoflavone from the pods of Milletia auriculata

The pods of Milletia auriculata have yielded a new substance, 5,7-dihydroxy-6-methoxy-4′-O-prenyloxyisoflavone.     

A new species of Oberonia (Orchidaceae) from Western Ghats of Kerala,India

A new Oberonia species, O. muthikulamensis (Orchidaceae), is described and illustrated from Muthikulam forest, Western Ghats of Kerala, India. It is compared with a closely morphologically similar species, O. sebastiana, endemic to Western Ghats.     

Steric Effect of a Bulky Substituent At 5′-Position on the Regioselectivity of 2′ vs. 3′-O-Methylation of N6- Cyclohexyladenosine

Abstract

Steric effect of a trityl or substituted trityl group at 5′-OH of N⁶-cyclohexyladenosine on the regioselective 2′ vs. 3′-O-methylation under phase transfer catalysis conditions was investigated. Compound 4 showed only a modest increase in the selectivity of 2′ over 3′-O-methylation compared to compound 1.     

The gp120 Protein Is a Second Determinant of Decreased Neurovirulence of Indian HIV-1C Isolates Compared to Southern African HIV-1C Isolates

Regional differences in neurovirulence have been documented among subtype/clade-C HIV-1 isolates in India and Southern Africa. We previously demonstrated that a C31S substitution in Clade-C Tat dicysteine motif reduces monocyte recruitment, cytokine induction and direct neurotoxicity. Therefore, this polymorphism is considered to be a causative factor for these differences in neurovirulence. We previously reported on the genotypic differences in Tat protein between clade-C and rest of the clades showing that approximately 90% of clade-C HIV-1 Tat sequences worldwide contained this C31S polymorphism, while 99% of non-clade C isolates lacked this Tat polymorphism at C31 residue (Ranga et al. (2004) J Virol 78∶2586–2590). Subsequently, we documented intra-clade-C differences in the frequency of Tat dicysteine variants between India and Southern Africa, as the basis for differential disease severity and showed the importance of the Tat dicysteine motif for neuropathogenesis using small animal models. We have now examined if determinants of neurovirulence besides Tat are different between the clade-C HIV-1 isolates from Southern Africa and India. Envelope glycoprotein gp120 is a well-documented contributor to neurotoxicity. We found that gp120 sequences of HIV-1 isolates from these two regions are genetically distinct. In order to delineate the contribution of gp120 to neurovirulence, we compared direct in vitro neurotoxicity of HIV-infected supernatants of a representative neurovirulent US clade-B isolate with two isolates each from Southern Africa and India using primary human neurons and SH-SY5Y neuroblastoma cells. Immunodepletion of gp120 of both US clade B and the Southern African clade C isolates revealed robust decreases in neurotoxicity, while that of the Indian isolates showed minimal effect on neurotoxicity. The gp120 as a cause of differential neurotoxicity was further confirmed using purified recombinant gp120 from HIV isolates from these regions. We conclude that gp120 is one of the key factors responsible for the decreased neurovirulence of Indian clade C HIV-1 isolates when compared to South African clade C HIV-1.