Subunit structure of human and rat glutathione S-transferases

In rat tissues different forms of glutathione (GSH) S-transferases represent various dimeric combinations of at least four different classes of subunits categorized on the basis of their Mr values as seen on polyacrylamide gels. These subunit types represent heterogeneous populations and the actual number of subunits in rat GSH S-transferases may be far more than is known at present. Human GSH S-transferases arise from dimeric combinations of at least four immunologically and functionally distinct subunits which can be classified into three types, A (Mr 26,500), B (Mr 24,500) and C (Mr 22,500). There is evidence for considerable charge heterogeneity in each of these subunit types.     

Glutathione S-transferases of human lung: characterization and evaluation of the protective role of the alpha-class isozymes against lipid peroxidation.

Glutathione S-transferase (GST) isozymes of human lung have been purified, characterized, quantitated, and, based on their structural and immunological profiles, identified with their respective classes. The tau-, mu-, and alpha-class GSTs represented 94, 3, and 3% activities of total human lung GSTs toward CDNB, respectively, and 60, 10, and 30% of total GST protein, respectively. Both the mu- and the alpha-class GSTs of human lung exhibited heterogeneity. The two mu-class GSTs of human lung had pI values of 6.5 and 6.25 and were differentially expressed in humans. Significant differences were seen between the kinetic properties of these two isozymes and also between the lung and liver mu-class GSTs. The alpha-class GST isozymes of lung resolved into three peaks during isoelectric focusing corresponding to pI values of 9.2, 8.95, and 8.8. All three alpha-class GSTs isozymes had blocked N-termini and were immunologically similar to human liver alpha-class GSTs. Peptide fingerprints generated by SV-8 protease digestion and CNBr cleavage indicated minor structural differences between the liver and the lung alpha-class GSTs. The three alpha-class GSTs of lung expressed glutathione peroxidase activities toward the hydroperoxides of phosphatidylcholine, phosphatidylethanolamine, and phosphatidylglycerol, with Km values in the range of 22 to 87 microM and Vmax values in the range of 67-120 mol/mol/min, indicating the involvement of the alpha-class GSTs in the protection mechanisms against peroxidation. All three classes of lung GSTs expressed activities toward leukotriene A4 methyl ester and epoxy stearic acid but the mu-class GSTs had relatively higher activities toward these substrates.     

Short communication: Protoplast formation from the thermophilic fungus Malbranchea sulfurea,using the thermostable chitinase and laminarinase of Paecilomyces varioti

Two thermostable enzymes produced by the thermophilic fungus Paecilomyces varioti, a chitinase and laminarinase, were used to isolate protoplasts of a thermophilic fungus, Malbranchea sulfurea. The frequency of protoplast regeneration observed (35%) was considerably higher than that obtained using commercial lytic enzymes.     

Stemflow: A Source of Nutrients in some Naturally Growing Epiphytic Orchids of the Sikkim Himalaya

A study on five naturally growing epiphytic orchids viz., Bulbophyllum affine Lindl., Coelogyne ochracea Lindl., Otochilus porrecta Lindl., Cirrhopetalum cornutum Lindl. and C. cornutum (var.) was carried out in the subtropical belt of Sikkim Himalaya. Stemflow leachates formed the main source of ammonium-N and nitrate-N for uptake by these orchids. Phosphorus concentration in the tissues of these orchids was high. Phosphate-P from stemflow does not seem to be a regular source of phosphorus for these orchids. Absorption/desorption results indicate that organic-N from stemflow leachates is not utilized by these orchids.     

Evidence for Differential Resistance to Peronospora parasitica (downy mildew) in Accessions of Brassica juncea (mustard) at the Cotyledon Stage

Thirty-one Brassica juncea accessions were screened at the cotyledon stage for resistance to four isolates of Peronospora parasitica. Isolates R1 and P003 were derived from crops of oilseed rape (B. napus ssp. oleifera) in the UK and isolates IP01 and IP02 were derived from crops of mustard (B. juncea) in India. B. napus cv. Ariana, which was used as a susceptible control for isolates from B. napus, was resistant to isolates from B. juncea. All, B. juncea accessions were resistant to isolates from B. napus except one accession which expressed moderate resistance to isolate P003. Five groups of B. juncea accessions with differential resistance were identified. Lines homogeneous for resistance were selected from seedling populations of accessions that exhibited a heterogeneous reaction to isolates from B. juncea. The differential resistance identified in the B. juncea-P. parasitica combination can be used as a foundation for future studies of the genetics of the host-pathogen interaction and for breeding for disease resistance.     

Movement and distribution pattern of the residues of granular insecticides in tropical soil and okra plants

Summary The increased downward mobility of phorate, quinalphos and carbofuran residues was detected in soil with increase in depth of soil column whereas aldicarb was found to remain localised mainly in 0–7.5 cm and 7.5–15.0 cm layers. Persistence of organophosphate insecticides was higher as compared to carbamates in all the soil layers. Residues of all the four insecticides got distributed in all parts of okra plant through uptake but accumulated in higher amounts in fruits only. Contribution No. 312/83 from I.I.H.R. Bangalore (India)     

Increase in Lysolecithin Content of Brain Microsomes in Phenobarbitone-Administered Rats and Its Relation to Lipid Peroxidation

Administration of phenobarbitone caused a marked increase in the capacity of rat brain microsomes to produce thiobarbituric acid-reactive substances in vitro. Enzymatic peroxidation of lipids was more affected than the nonenzymatic processes occurring in heat-inactivated preparations. Analysis of the phospholipid profile showed a drastic decrease in phosphatidylcholine and total phospholipid contents in the exposed animals, but about a fivefold increase in the lysophosphatidylcholine fraction. Data for in vivo incorporation of [14C]choline showed a similar pattern of high radioactivity in lysolecithin. The increase in lipid peroxidation could be related to the higher level of lysolecithin and the accompanying structural and functional changes in microsomes resulting from the neurotoxic effects of phenobarbitone.