pp 157-158 June 2008
pp 159-161 June 2008
pp 163-169 June 2008 Perspectives
The nineteenth-century British botanist, Joseph Dalton Hooker, was one of the people whose career became a model for that of the modern, professional scientist. However, he preferred to refer to himself as a philosophical botanist, rather than a professional. This paper explores the reasons for this choice, and analyses Hooker’s imperial approach to plant classification, the consequences of which are still with us.
pp 171-175 June 2008 Series
pp 177-184 June 2008 Articles
Issues related to the nicotine content of tobacco have been public concerns. Several reports have described decreasing nicotine levels by silencing the putrescine N-methyltransferase (PMT) genes, but the reported variations of nicotine levels among transgenic lines are relatively low in general. Here we describe the generation in tobacco (Nicotiana tabacum) lines with widely different, reduced nicotine levels using three kinds of RNA-silencing approaches. The relative efficacies of suppression were compared among the three approaches regarding the aspect of nicotine level in tobacco leaves. By suppressing expression of the PMT genes, over 200 transgenic lines were obtained with nicotine levels reduced by 9.1–96.7%. RNA interference (RNAi) was the most efficient method of reducing the levels of nicotine, whereas cosuppression and antisense methods were less effective. This report gives clues to the efficient generation of plants with a variety of metabolite levels, and the results demonstrate the relative efficiencies of various RNA-silencing methods.
pp 185-193 June 2008 Articles
A set of Ds-element enhancer trap lines of Arabidopsis thaliana was generated and screened for expression patterns leading to the identification of a line that showed root-specific expression of the bacterial uidA reporter gene encoding 𝛽-glucuronidase (GUS). The insertion of the Ds element was found to be immediately downstream to a glycosyltransferase gene At1g73160. Analysis of At1g73160 expression showed that it is highly root-specific. Isolation and characterization of the upstream region of the At1g73160 gene led to the definition of a 218 bp fragment that is sufficient to confer root-specific expression. Sequence analysis revealed that several regulatory elements were implicated in expression in root tissue. The promoter identified and characterized in this study has the potential to be applied in crop biotechnology for directing the root-specific expression of transgenes.
pp 195-207 June 2008 Articles
Human seminal proteinase and prostate-specific antigen (PSA) were each isolated from human seminal fluid and compared. Both are glycoproteins of 32–34 kDa with protease activities. Based on some physicochemical, enzymatic and immunological properties, it is concluded that these proteins are in fact identical. The protein exhibits properties similar to kallikrein-like serine protease, trypsin, chymotrypsin and thiol acid protease. Tests of the activity of the enzyme against some potential natural and synthetic substrates showed that bovine serum albumin was more readily hydrolysed than casein. The results of this study should be useful in purifying and assaying this protein. Based on published studies and the present results, the broad proteolytic specificity of human seminal proteinase suggests a role for this protein in several physiological functions.
pp 209-220 June 2008 Articles
Involution of the rat ventral prostate and concomitant modulation of gene expression post-castration is a well-documented phenomenon. While the rat castration model has been extensively used to study androgen regulation of gene expression in the ventral prostate, it is not clear whether all the gene expression changes post-castration are due to androgen depletion alone. To obtain insights into this, we performed differential display reverse transcriptase polymerase chain reaction (DD-RT-PCR) which resulted in the identification of castration and/or flutamide-regulated genes in the rat ventral prostate. These include clusterin, methionine adenosyl transferase II𝛼, and prostate-specific transcripts such as PBPC1BS, S100RVP and A7. While clusterin, PBPC1BS and methionine adenosyl transferase II𝛼 are regulated by both castration and flutamide, S100 RVP and A7 are regulated by castration alone. Interestingly, we show that flutamide, unlike castration, does not induce apoptosis in the rat ventral prostate epithelium, which could be an underlying cause for the differential effects of castration and flutamide treatment. We propose that castration leads to enrichment and depletion of stromal and epithelial cell types, respectively, resulting in erroneous conclusions on some of the cell type-specific transcripts as being androgen regulated.
pp 221-230 June 2008 Articles
Mycobacterium tuberculosis survives and persists for prolonged periods within its host in an asymptomatic, latent state and can reactivate years later if the host’s immune system weakens. The dormant bacilli synthesize and accumulate triacylglycerol, reputed to be an energy source during latency. Among the phospholipases, phospholipase C plays an important role in the pathogenesis. Mutations in a known phospholipase C, plcC, of M. tuberculosis attenuate its growth during the late phase of infection in mice. Hydrolysis of phospholipids by phospholipase C generates diacylglycerol, a well-known signalling molecule that participates in the activation of extracellular signal-regulated kinases (ERK) through protein kinase C leading to macrophage activation. In the present study, we show that M. tuberculosis possesses an additional cell wall-associated protein, Rv3487c, with phospholipase C activity. The recombinant Rv3487c hydrolyses the substrate phosphatidylcholine and generates diacylglycerol by removing the phosphocholine. Furthermore, Rv3487c is expressed during infection as it exhibits significant humoral immunoreactivity with sera from children with tuberculosis, but not with that from adult patients.
pp 231-237 June 2008 Articles
The aim of this study was to propose the use of red light-emitting diode (LED) as an alternative light source for methylene blue (MB) photosensitizing effect in photodynamic therapy (PDT). Its effectiveness was tested against Staphylococcus aureus (ATCC 26923), Escherichia coli (ATCC 26922), Candida albicans (ATCC 90028) and Artemia salina. The maximum absorption of the LED lamps was at a wavelength of 663 nm, at intensities of 2, 4, 6 and 12 J.cm–2 for 10, 20, 30 and 60 min of exposure, respectively. Assays with and without LED exposure were carried out in plates containing MB at concentrations of 7 to 140.8 𝜇M for microorganisms and 13.35 to 668.5 𝜇M for microorganisms or microcrustaceans. The LED exposure induced more than 93.05%, 93.7% and 93.33% of growth inhibition for concentrations of 42.2 𝜇M for S. aureus (D-value=12.05 min) and 35.2 𝜇M for E. coli (D-value=11.51 min) and C. albicans (D-value=12.18 min), respectively after 20 min of exposure. LED exposure for 1 h increased the cytotoxic effect of MB against A. salina from 27% to 75%. Red LED is a promising light device for PDT that can effectively inhibit bacteria, yeast and microcrustacean growth.
pp 239-247 June 2008 Articles
The present investigation was carried out to know the seasonal variation in plasma glucose, insulin and glucagon cells during the reproductive cycle of untreated Melanochelys trijuga. Pancreatic endocrine cells were immunochemically localized. Insulin-immunoreactive (IR) cells occurred in groups of 3–20 and were in close apposition, while glucagon-IR cells were distributed individually between the exocrine pancreas or formed anastomosing cords where cells were not intimately attached. Whenever both IR cell types were present together forming an islet, insulin-IR cells formed clusters in the centre with glucagon-IR cells being scattered at the periphery. Glucagon-IR cells seemed to be secretory throughout the pancreas during the reproductive cycle, while insulin-IR cells were found to be pulsating in their secretion. Mean size of the islet was 1.306, 0.184 and 2.558 mm in the regenerative, reproductive and regressive periods, respectively. In general, insulin-IR cells measured 5.18 𝜇m and glucagon-IR cells 5.22 𝜇m in their longest axis. Invariably, glucagon-IR cells were more in number than insulin-IR cells. The fasting plasma glucose level was 69.97 mg% during the regenerative period, which increased to 97.96 mg% during the reproductive period, and reached a peak value of 113.52 mg% in the regressive period.
pp 249-257 June 2008 Articles
Coat protein (CP)-mediated resistance against an Indian isolate of the Cucumber mosaic virus (CMV) subgroup IB was demonstrated in transgenic lines of Nicotiana benthamiana through Agrobacterium tumefaciens-mediated transformation. Out of the fourteen independently transformed lines developed, two lines were tested for resistance against CMV by challenge inoculations. The transgenic lines exhibiting complete resistance remained symptomless throughout life and showed reduced or no virus accumulation in their systemic leaves after virus challenge. These lines also showed virus resistance against two closely related strains of CMV. This is the first report of CP-mediated transgenic resistance against a CMV subgroup IB member isolated from India.
pp 259-267 June 2008 Articles
A fungus was isolated from the stem cuttings of Taxus celebica, which produced paclitaxel in liquid-grown cultures. The fungus was identified as Fusarium solani based on colony characteristics, morphology of conidia and the 26S rDNA sequence. Paclitaxel was identified by chromatographic and spectroscopic comparison with authentic paclitaxel and its cytotoxic activity towards Jurkat cells in vitro.
pp 269-277 June 2008 Articles
Most drugs and xenobiotics induce the expression of cytochrome P450 (CYP) enzymes, which reduce the bioavailability of the inducer and/or co-administered drugs. Therefore, evaluation of new drug candidates for their effect on CYP expression is an essential step in drug development. The available methods for this purpose are expensive and not amenable to high-throughput screening. We developed a fluorescence-based in vivo assay using transgenic Caenorhabditis elegans worms that express the green fluorescent protein (GFP) under the control of various CYP promoters. Using this assay, we found striking similarities between the worm CYPs and their human orthologs in their response to treatment with various drugs. For example, the antibiotic rifampicin, one of the strongest inducers of the human gene CYP3A4, was the strongest inducer of the worm ortholog CYP13A7. Since worms can be easily grown in liquid medium in microtitre plates, the assay described in this paper is suitable for the screening of a large number of potential lead compounds in the drug discovery process.
pp 279-287 June 2008 Articles
A novel nafion–riboflavin membrane was constructed and characterized by the scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-visible spectroscopy and cyclic voltammetric techniques. The estimated average diameter of the designed nanoparticles was about 60 nm. The functional membrane showed a quasi-reversible electrochemical behaviour with a formal potential of –562 ± 5 mV (vs Ag/AgCl) on the gold electrode. Some electrochemical parameters were estimated, indicating that the system has good and stable electron transfer properties. Moreover, horseradish peroxidase (HRP) was immobilized on the riboflavin–nafion functional membrane. The electrochemical behaviour of HRP was quasi-reversible with a formal potential of 80 ± 5 mV (vs Ag/AgCl). The HRP in the film exhibited good catalytic activity towards the reduction of H2O2. It shows a linear dependence of its cathodic peak current on the concentration of H2O2, ranging from 10 to 300 𝜇M.
pp 289-301 June 2008 Articles
Living systems are spectacular examples of spatiotemporally organized structures. During the development of complex organization there is dynamic equilibrium between the local and global processes acting at the intra- and intercellular levels in multiple space and time scales. Although in modelling studies such spatiotemporal systems can be described by different space–time scales and at many organizational levels, the experimental quantities measured and predictions useful for practical applications are at a macroscopic (coarser or averaged) level/scale; these are limited by the resolution of the measuring method and experimental protocol. In this work, we address whether the spatiotemporal collective dynamics exhibited by a multiscale system can discriminate between, or be borne out by, the coarse-grained and averaged measurements done at different spatial and temporal scales. Using a simple model of a ring of cells, we show that measurements of both spatial and spatiotemporal average behaviour in this multicellular ensemble can mask the variety of collective dynamics observed at other space–time scales, and exhibit completely different behaviours. Such outcomes of measurements can lead to incomplete and incorrect understanding of physiological functions and pathogenesis in multicell ensembles.
pp 303-306 June 2008 Mini-review
pp 307-307 June 2008