Glycosmis arborea extract as a hepatoprotective agent.

Glycosmis arborea is a plant possessing various medicinal properties. The aim of the present study was to investigate the hepatoprotective efficacy of the butanol extract obtained from the aerial parts of the plant. The test sample was prepared by extracting the material through different steps. The extract thus obtained was dissolved in normal saline. Albino rats were prophylactically treated with the extract (i.p.) for 3 weeks. At the end of 3rd week all the groups were injected with hepatotoxic agents. After 48 h of injection, blood was collected and livers were taken out. Different enzymes in the serum were assayed and histopathological study was performed with liver. Glycosmis arborea extract was able to overcome the toxic effects of hepatotoxic agents in terms of lowering the levels of serum GPT, alkaline phosphatase and increased level of SOD in serum. TBARS generation in liver was also altered. Moreover, necrosis of liver produced by carbon tetrachloride was reversed by the extract.

Symbiotic nitrogen fixation: molecular cloning of Rhizobium genes involved in exopolysaccharide synthesis and effective nodulation.

A transposon (Tn5)-induced mutant (strain ANU437) of Rhizobium trifolii was isolated in which no water-soluble exopolysaccharide (EPS) could be detected. This mutant was also incapable of forming nitrogen-fixing root nodules on clover plants. Molecular cloning has demonstrated that the Tn5 transposon was responsible for both of these mutant phenotypes and that there is a direct correlation between EPS synthesis in this bacterial strain and its ability to carry out symbiotic nitrogen fixation. In the mutant ANU437, Tn5 was located in a 9.4-kb EcoRI fragment that was cloned into the amplifiable plasmid pBR322. The recombinant plasmid was used as a hybridization probe to isolate the corresponding wild-type DNA sequence of R. trifolii from a lambda Charon 28 genomic clone bank. This DNA sequence was subcloned into the broad host range conjugative plasmid RP4 and introduced into the Escherichia coli strain RR1. It was then transferred to the mutant ANU437 by conjugation. The acquisition of the wild-type DNA sequence by the mutant ANU437 resulted in the restoration of its ability to synthesize normal levels of EPS and to form nitrogen-fixing nodules on white and subterranean clovers.

Changes in Wheat Leaf Polysomal Messenger RNA Populations during the Early Stages of Rust Infection: EFFECTS OF CHLORAMPHENICOL AND LINCOMYCIN ON CELL-FREE TRANSLATION BY POLYSOMES FROM HEALTHY AND INFECTED LEAVES.

Polysomes isolated from a susceptible variety of wheat leaves (cultivar W2691) and those inoculated with the wheat stem rust fungus (f. sp. tritici, race 126-ANZ-6, 7) were incubated in a cell-free protein-synthesizing system. Under these conditions, different size classes of polypeptides, ranging in molecular weight from 10,000 to 80,000, are radiolabeled. Using double-isotope labeling technique, we show that some discrete size classes of polypeptides are synthesized in significantly greater quantitites by polysomes from inoculated leaves compared to the corresponding size classes synthesized by polysomes from healthy leaves. These results confirm our previous observation that there are significant changes in the wheat leaf polysomal messenger RNA populations at 3 days after inoculation with the rust fungus.The effects of the organelle-specific inhibitors of protein synthesis, chloramphenicol and lincomycin, on in vitro polysomal messenger RNA translation were investigated. The polypeptides synthesized by polysomes from healthy and inoculated leaves in the presence of chloramphenicol were compared. The results show that, even in the presence of this antibiotic, the polysomes from inoculated leaves synthesize greater quantities of some size classes of polypeptides. These data indicate that changes in polysomal messenger RNA populations involve, at least in part, cytoplasmic messenger RNA.

Changes in the Ribonuclease Activity of Flax Cotyledons following Inoculation with Flax Rust.

There was a significant increase in the ribonuclease activity of both resistant (Bombay) and susceptible (Bison) varieties of flax (Linum usitatissimum L.) 3 to 4 days after inoculation with flax rust (Melampsora lini [Pers.] Lev., race No. 3). A second and much greater increase in the activity of this enzyme occurred only in the susceptible host at later stages of disease development. While a similar increase in ribonuclease level was also caused by mechanical injury, evidence is presented showing qualitative differences between the enzyme from parasitized tissue and that from the mechanically injured cotyledons. Comparison of the enzyme from healthy and inoculated cotyledons and from flax rust revealed the presence of a relatively unstable component and some unique catalytic properties in the enzyme from inoculated cotyledons.

Changes in the transcription pattern of flax cotyledons after inoculation with flax rust.

The rate of (32)P incorporation into RNA fractions of flax cotyledons (Linum usitatissimum L. var. Bison) was found to increase two- to three-fold by 48h after inoculation with flax rust [Melampsora lini (Pers.) Lev., race no. 3]. This was accompanied by a change in the nucleotide composition of the newly transcribed sodium chloride-soluble RNA fraction. A comparison of the nucleotide composition of the RNA synthesized in the host-parasite complex at different stages of development indicated the preferential synthesis of one or more molecular species of RNA with a high A+U/G+C ratio at a relatively early stage of infection. Treatment of healthy plants with indol-3-ylacetic acid also resulted in a substantial stimulation in the rate of (32)P incorporation into RNA but this was not accompanied by a detectable change in the nucleotide ratios of the newly synthesized RNA. These results suggest that the synthesis of one of more additional RNA species or the augmented synthesis of certain species of RNA may be a specific phenomenon elicited by host-pathogen interaction.