Bela Peethambaran

Leaf biomechanical properties in Arabidopsis thaliana polysaccharide mutants affect drought survival

Individual sugars are the building blocks of cell wall polysaccharides, which in turn comprise a plant׳s overall architectural structure. But which sugars play the most prominent role in maintaining a plant׳s mechanical stability during large cellular deformations induced by drought? We investigated the individual contributions of several genes that are involved in the synthesis of monosaccharides which are important for cell wall structure. We then measured drought tolerance and mechanical integrity during simulated drought in Arabidopsis thaliana. To assess mechanical properties, we designed a small-scale tensile tester for measuring failure strain, ultimate tensile stress, work to failure, toughness, and elastic modulus of 6-week-old leaves in both hydrated and drought-simulated states. Col-0 mutants used in this study include those deficient in lignin, cellulose, components of hemicellulose such as xylose and fucose, the pectic components arabinose and rhamnose, as well as mutants with enhanced arabinose and total pectin content. We found that drought tolerance is correlated to the mechanical and architectural stability of leaves as they experience dehydration. Of the mutants, S096418 with mutations for reduced xylose and galactose was the least drought tolerant, while the arabinose-altered CS8578 mutants were the least affected by water loss. There were also notable correlations between drought tolerance and mechanical properties in the diminished rhamnose mutant, CS8575 and the dehydrogenase-disrupted S120106. Our findings suggest that components of hemicellulose and pectins affect leaf biomechanical properties and may play an important role in the ability of this model system to survive drought.

Anti-inflammatory and Anti-microbial Properties of Achillea millefolium in Acne Treatment

Inflammatory events occur very early in the development of acne lesions. Inflammation also plays a role in the late stages of acne vulgaris infection. Hence drugs used in the treatment of acne should also have anti-inflammatory properties as inflammation exists throughout the life cycle of acne lesions. This chapter gives an account of the current knowledge on the phytochemistry and pharmacological aspects of anti-acne compounds in yarrow ( Achillea millefolium ), which were also tested to be anti-inflammatory. Different parts of this plant have been in used in traditional medicine as astringent, stimulant and mild aromatic, for treating cold and influenza and as antiphlogistic. Alkaloids such as azulene extracted from flowers and leaves of yarrow have been reported to have anti-inflammatory and analgesic activity. A research study in our laboratory has established a novel alkamide isolated from the leaves and stems of Achillea “ Moonshine ” that are anti-microbial to acne causing bacteria Propionibacterium acnes . This compound was isolated from petroleum ether extracts of A . “ Moonshine ” leaves and stems, using high performance chromatography and bioactivity guided thin layer chromatography. The potent anti-acne alkamide demonstrated the ability to reduce inflammation, scavenge free radicals and reduce tyrosinase activity to remove residual pigmentation caused after acne treatment.

Abstract 3802: Selective cytotoxicty and mechanism of Myrothamnus flabellifolius, an edible medicinal plant, on acute myeloid leukemia cells

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA Current therapies for acute myeloid leukemia involve chemotherapy and radiation, which cause damage to normal and cancerous cells. There is a dire need to discover novel drugs that target only cancer cells. Myrothamnus flabellifolius is a South African resurrection plant known for its anti-viral, anti-microbial and anti-inflammatory properties. Human myeloid leukemia (HL-60) cells and normal (TK-6) lymphocytes were treated with the methanolic extract of M. flabellifolius. Cancer cells treated with extract depicted a significant reduction in viability as compared to normal cells. The first part of this project involved fractionation of the methanolic extract using HPLC and testing each fraction on the normal and leukemic cell lines to find a fraction that selectively killed the cancer cells. A phytochemical analysis was also conducted for characterization of the anticancer compounds. In terms of mechanism, the loss in HL-60 viability was accompanied by the induction of caspase dependent apoptosis by way of caspase-7 cleavage. Heat shock proteins are molecular chaperones that aid in protein reassembly under stressful conditions and protect cells from apoptosis. TK-6 cells express heat shock protein 70 at a high level while HL-60 cells do not express the protein under normal conditions. The expression of HSP70 exhibits a positive correlation with the viability of cells post treatment with extract, indicating that this vital protein plays an important role in the survival of cells post treatment with M. flabellifolius extract. Citation Format: Abeer Badiab, Jasjit Dhillon, Fizal Nabbie, Bela Peethambaran. Selective cytotoxicty and mechanism of Myrothamnus flabellifolius, an edible medicinal plant, on acute myeloid leukemia cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3802. doi:10.1158/1538-7445.AM2015-3802

Does a repeated guided-instruction approach with multiple assessments increase student learning of science?

Guided instruction is an approach that fully explains the concepts and procedures that students are required to learn. It seems intuitive that this approach should increase student learning; however, there is evidence in the literature that this may not always be the case. We wanted to assess the effectiveness of our own repeated guided-instruction approach. This idea was tested in an introductory biology course on the topic of science-process skills and in a molecular biology course on DNA replication. Each course evaluated five concepts on their topic using five multiple-choice questions at four time points. Guided instruction for these topics was provided in the form of explicit lectures, discussions, questioning, case studies and multiple assessments. In both courses, mean test scores increased significantly over the four-test sequence, although not with each assessment or each concept. Increases in molecular biology were greater than in introductory biology. Content background and concept difficulty are two possible major factors contributing to this variation. In introductory biology, students struggled most with the concepts of definition of hypothesis and type I error. Further learning gains may be realised by providing and assessing context and content background to help students overcome difficult concepts.