Stimulatory and period-specific effect of nitric oxide on in vitro caulogenesis in Albizzia lebbeck (L.) Benth.

The paper reports stimulatory effect of nitric oxide (NO) on in vitro caulogenesis in Albizzia lebbeck, a tree legume. Exogenously supplied NO donor, sodium nitroprusside (SNP) stimulated shoot differentiation from hypocotyl explants of Albizzia lebbeck, excised from its in vitro seedlings. Potassium ferrocyanide, a structural analog of SNP incapable of releasing NO, did not promote shoot organogenesis. Likewise, metabolic products of NO, NO₂ ⁻ and NO₃ ⁻, provided as NaNO₂ and NaNO₃ did not enhance shoot differentiation. The NO scavenger, 2-(4-carboxy-phenyl)-4, 4, 5, 5-tetramethylimideazoline-1-oxyl-3-oxide (cPTIO), supplemented along with SNP, at equimolar concentration, reversed the stimulatory effect of the latter, thus, confirming the role of NO in promotion of in vitro caulogenesis. The transfer of explants cultured on the basal medium (BM) to the same containing SNP and vice versa after different time intervals revealed that for its enhancing effect, SNP was required only during the initial phase (5 days) of culture. Its presence or administration beyond 5 days neither promoted nor inhibited the caulogenic response.     

Effect of Carbon Source on the Shoot Proliferation Potential of Epicotyl Explants of Syzygium cuminii

Black plum (Syzygium cuminii) explants were grown in vitro on Murashige and Skoog medium. Among the various saccharides tested, the best caulogenic response was afforded by sucrose both in terms of explant response and shoot developing potential. Within monosaccharides, mannose was totally inhibitory as on the medium supplemented with this the shoot buds failed to develop, while, fructose and xylose completely inhibited the opening as well as the elongation of shoot buds. Glucose and galactose did not completely inhibit the caulogenic response. Among disaccharides, other than sucrose, maltose totally inhibited the elongation of the developed shoot buds while lactose supported it to a limited extent. Sugar alcohols, though not as good as sucrose, proved better sources of carbon and energy than the other tested sugars. Sucrose at concentration 4 % proved to be the best in developing 4.2 shoots per explant. This revised version was published online in July 2006 with corrections to the Cover Date.     

Adh 1 first intron polymorphisms in Argentinean populations of Ceratitis capitata

DNA size polymorphisms were utilized in a study of 24 natural populations of Ceratitis capitata Wiedemann (Diptera: Tephritidae) from Argentina. The first intron of alcohol dehydrogenase 1 gene (Adh₁) was amplified using exon priming intron crossing‐polymerase chain reaction. Three size variants were detected among the 307 samples analyzed. To better differentiate the size variants, further digestion of PCR products with the EcoRI restriction enzyme was carried out. Complete nucleotide sequences of the three‐allele variants were obtained and single changes, insertions, deletions, and EcoRI recognition sites were located. Population allele frequencies were analyzed and a global mean heterozygosity (He) of 0.33 was obtained. In most populations, observed allelic frequencies conformed to Hardy–Weinberg expectations. Significant differences between provinces and sampling sites within these provinces, and among some populations were found. The average number of insects exchanged among populations (Nm) was estimated and high values were observed between Argentina and populations from two African countries (Morocco and Kenya), Australia, and Hawaii (Kauai). Pest introduction sources and dispersion patterns in Argentina are discussed based on these results as well as on available bibliographical data.     

Quantitative structure-activity relationship study on some dihydropteridine reductase inhibitors

The dihydropteridine reductase (DHPR) inhibitory potencies of some 4-phenyltetrahydropyridines, 4-phenylpiperidines, and 4-phenylpyridines, are analyzed in relation to their physico-chemical and molecular properties. They are found to have significant correlation with Hammett constant sigma and the van der Waals volume Vw. The correlation is linear with sigma and parabolic with Vw. Hence, it is argued that DHPR inhibition involves dispersion interaction and is enhanced by electron donation from the substituents but hindered by steric effects produced by large substituents. It is also found that these electronic and steric effects are significant only when they are produced by substituents being at specific position in the molecules.     

Pseudomonas aeruginosa homoserine lactone triggers apoptosis and Bak/Bax‐independent release of mitochondrial cytochrome C in fibroblasts

Pseudomonas aeruginosa use N‐(3‐oxododecanoyl)‐homoserine lactone (C12) as a quorum‐sensing molecule to regulate gene expression in the bacteria. It is expected that in patients with chronic infections with P. aeruginosa, especially as biofilms, local [C12] will be high and, since C12 is lipid soluble, diffuse from the airways into the epithelium and underlying fibroblasts, capillary endothelia and white blood cells. Previous work showed that C12 has multiple effects in human host cells, including activation of apoptosis. The present work tested the involvement of Bak and Bax in C12‐triggered apoptosis in mouse embryo fibroblasts (MEF) by comparing MEF isolated from embryos of wild‐type (WT) and Bax^?/?/Bak^?/? (DKO) mice. In WT MEF C12 rapidly triggered (minutes to 2 h): activation of caspases 3/7 and 8, depolarization of mitochondrial membrane potential (Δψ_mito), release of cytochrome C from mitochondria into the cytosol, blebbing of plasma membranes, shrinkage/condensation of cells and nuclei and, subsequently, cell killing. A DKO MEF line that was relatively unaffected by the Bak/Bax‐dependent proapoptotic stimulants staurosporine and etoposide responded to C12 similarly to WT MEF: activation of caspase 3/7, depolarization of Δψ_mito and release of cytochrome C and cell death. Re‐expression of Bax or Bak in DKO MEF did not alter the WT‐like responses to C12 in DKO MEF. These data showed that C12 triggers novel, rapid proapoptotic Bak/Bax‐independent responses that include events commonly associated with activation of both the intrinsic pathway (depolarization of Δψ_mito and release of cytochrome C from mitochondria into the cytosol) and the extrinsic pathway (activation of caspase 8). Unlike the proapoptotic agonists staurosporine and etoposide that release cytochrome C from mitochondria, C12's effects do not require participation of either Bak or Bax.