Pollen-pistil interaction in Linum grandiflorum

A detailed investigation of the receptive surface of the stigma of a dimorphic taxon, Linum grandiflorum, was carried out using scanning electron microscopy, cytochemistry and polyacrylamide gel electrophoresis. The stigma surfaces of the pin and thrum morphs showed distinct differences. The stigma of the pin morph was of the dry type and the papillae were covered with a uniform cuticle-pellicle layer. The stigma of the thrum morph, on the other hand, resembled the wet type; the cuticle-pellicle layer was disrupted at places and a secretion product was released onto the surface of the stigma. Coomassie blue staining material was present on the surface of only the thrum stigma. Although esterases and acid phosphatases were present on the stigma of both the morphs, their activity was invariably higher on the thrum stigma. Polyacrylamide gel electrophoresis of stigma leachates also showed distinct differences in the protein profiles of the two morphs.     

Inhibitors of HIV-1 attachment. Part 2: An initial survey of indole substitution patterns

The effects of introducing simple halogen, alkyl, and alkoxy substituents to the 4, 5, 6 and 7 positions of 1-(4-benzoylpiperazin-1-yl)-2-(1H-indol-3-yl)ethane-1,2-dione, an inhibitor of the interaction between HIV gp120 and host cell CD4 receptors, on activity in an HIV entry assay was examined. Small substituents at C-4 generally resulted in increased potency whilst substitution at C-7 was readily tolerated and uniformly produced more potent HIV entry inhibitors. Substituents deployed at C-6 and, particularly, C-5 generally produced a modest to marked weakening of potency compared to the prototype. Small alkyl substituents at N-1 exerted minimal effect on activity whilst increasing the size of the alkyl moiety led to progressively reduced inhibitory properties. These studies establish a basic understanding of the indole element of the HIV attachment inhibitor pharmacophore.     

Monitoring microbial aeroflora using vegetable waste media: an ecological aspect

For isolation of aeromicroflora in ecologically different zones, a liquid vegetable waste, deproteinised leaf juice (DLJ) was used instead of usual media. DLJ samples from three different plants, cowpea (Vigna sinensis), turnip (Brassica campestris) and radish (Raphanus sativus), were used in order to determine their efficiency as potential growth media for different types of microbes. Four different ecological zones of West Bengal, India were selected to study the aeromicroflora. The zones were as follows: (i) densely populated and industrially polluted Calcutta (CAL); (ii) plateau region of western part of the state (WEST); (iii) Terai region of Northern Bengal (TER); (iv) sandy coastal zone of Midnapore district of Southern Bengal (SB). Each zone was subdivided into three subzones. The variation in population of fungi, bacteria and actinomycetes among these zones was studied. The relative abundance and species diversities of microbes were noted. The study indicates that pollution and ecological diversity both play important roles in controlling the above two factors.     

Efficient hydrolysis of β-substituted methyl esters susceptible to elimination by pig liver esterase

Methyl esters substituted at position with good leaving groups (nucleofugals) are smoothly hydrolysed by Pig Liver Esterase (PLE) in moderate to high yields.     

Design, synthesis, biological evaluation and QSAR studies of novel bisepipodophyllotoxins as cytotoxic agents

Two moieties of epipodophyllotoxin have been linked at C4-position to provide novel bisepipodophyllotoxin analogues. These have been evaluated for their anticancer potential and DNA-topoisomerase II poisoning activity. Most of these analogues have exhibited promising in vitro anticancer activity against different human tumour cell lines and interestingly 4(')-O-methylated analogues have shown increased cytotoxic activity. Similarly, the DNA-topo II poisoning activity tested for these compounds has not only exhibited the DNA cleavage potential comparable to etoposide, but for some compounds this cleavage potential is superior to etoposide. Further, an interesting structure-activity relationship of these epipodophyllotoxin dimers have been generated on the basis of GI(50) values. The equations indicated that GI(50) activity is strongly dependent on structural and thermodynamic properties. These QSAR results are discussed in conjunction with conformational analysis from molecular modelling studies. QSAR models developed in these studies will be helpful in the future to design novel potent bispodophyllotoxin analogues by minor structural modifications.     

The BCR/ABL tyrosine kinase induces production of reactive oxygen species in hematopoietic cells

The BCR/ABL oncogene causes chronic myelogenous leukemia, a myeloproliferative disorder characterized by clonal expansion of hematopoietic progenitor cells and myeloid cells. It is shown here that transformation of the hematopoietic cell lines Ba/F3, 32Dcl3, and MO7e with BCR/ABL results in an increase in reactive oxygen species (ROS) compared with quiescent, untransformed cells. The increase in ROS was directly due to BCR/ABL because it was blocked by the ABL-specific tyrosine kinase inhibitor STI571. Oxidative stress through ROS is believed to have many biochemical effects, including the potential ability to inhibit protein-tyrosine phosphatases (PTPases). To understand the significance of increased production of ROS, a model system was established in which hydrogen peroxide (H(2)O(2)) was added to untransformed cells to mimic the increase in ROS induced constitutively by BCR/ABL. H(2)O(2) substantially reduced total cellular PTPase activity to a degree approximately equivalent to that of pervanadate, a well known PTPase inhibitor. Further, stimulation of untransformed cells with H(2)O(2) or pervanadate increased tyrosine phosphorylation of each of the most prominent known substrates of BCR/ABL, including c-ABL, c-CBL, SHC, and SHP-2. Treatment of the BCR/ABL-expressing cell line MO7/p210 with the reducing agents pyrrolidine dithiocarbamate or N-acetylcysteine reduced the accumulation of ROS and also decreased tyrosine phosphorylation of cellular proteins. Further, treatment of MO7e cells with H(2)O(2) or pervanadate increased the tyrosine kinase activity of c-ABL. Drugs that alter ROS metabolism or reactivate PTPases may antagonize BCR/ABL transformation.