• Issue front cover thumbnail

      Volume 33, Issue 3

      September 2008,   pages  309-421

    • Clipboard: Functional embryo sac formation in Arabidopsis without meiosis – one step towards asexual seed formation (apomixis) in crops?

      Anna M G Koltunow Matthew R Tucker

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    • A surgeon's quest

      M S Valiathan

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      This last part of surgery, namely, operations, is a reflection on the healing art; it is a tacit acknowledgement of the insufficiency of surgery. It is like an armed savage who attempts to get that by force which a civilised man would get by stratagem.

    • What history tells us XIV. Regulation of gene expression by non-coding RNAs: the early steps

      Michel Morange

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    • Observations on sporozoite detection in naturally infected sibling species of the Anopheles culicifacies complex and variant of Anopheles stephensi in India

      Susanta Kumar Ghosh Satyanarayan Tiwari Kamaraju Raghavendra Tiruchinapalli Sundaraj Aditya Prasad Dash

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      Sporozoites were detected in naturally infected sibling species of the primary rural vector Anopheles culicifacies complex in two primary health centres (PHCs) and a variant of the urban vector Anopheles stephensi in Mangalore city, Karnataka, south India while carrying out malaria outbreak investigations from 1998–2006. Sibling species of An. culicifacies were identified based on the banding patterns on ovarian polytene chromosomes, and variants of An. stephensi were identified based on the number of ridges on the egg floats. Sporozoites were detected in the salivary glands by the dissection method. Of the total 334 salivary glands of An. culicifacies dissected, 17 (5.08%) were found to be positive for sporozoites. Of the 17 positive samples, 11 were suitable for sibling species analysis; 10 were species A (an efficient vector) and 1 was species B (a poor vector). Out of 46 An. stephensi dissected, one was sporozoite positive and belonged to the type form (an efficient vector). In malaria epidemiology this observation is useful for planning an effective vector control programme, because each sibling species/variant differs in host specificity, susceptibility to malarial parasites, breeding habitats and response to insecticides.

    • A comparative analysis of green fluorescent protein and 𝛽-glucuronidase protein-encoding genes as a reporter system for studying the temporal expression profiles of promoters

      P Kavita Pradeep Kumar Burma

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      The assessment of activity of promoters has been greatly facilitated by the use of reporter genes. However, the activity as assessed by reporter gene is a reflection of not only promoter strength, but also that of the stability of the mRNA and the protein encoded by the reporter gene. While a stable reporter gene product is an advantage in analysing activities of weak promoters, it becomes a major limitation for understanding temporal expression patterns of a promoter, as the reporter product persists even after the activity of the promoter ceases. In the present study we undertook a comparative analysis of two reporter genes, 𝛽-glucuronidase (gus) and green fluorescent protein (sgfp), for studying the temporal expression pattern of tapetum-specific promoters A9 (Arabidopsis thaliana) and TA29 (Nicotiana tabacum). The activity of A9 and TA29 promoters as assessed by transcript profiles of the reporter genes (gus or sgfp) remained the same irrespective of the reporter gene used. However, while the deduced promoter activity using gus was extended temporally beyond the actual activity of the promoter, sgfp as recorded through its fluorescence correlated better with the transcription profile. Our results thus demonstrate that sgfp is a better reporter gene compared to gus for assessment of temporal activity of promoters. Although several earlier reports have commented on the possible errors in deducing temporal activities of promoters using GUS as a reporter protein, we experimentally demonstrate the advantage of using reporter genes such as gfp for analysis of temporal expression patterns.

    • Differential dynamics of splicing factor SC35 during the cell cycle

      Kaushlendra Tripathi Veena K Parnaik

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      Pre-mRNA splicing factors are enriched in nuclear domains termed interchromatin granule clusters or nuclear speckles. During mitosis, nuclear speckles are disassembled by metaphase and reassembled in telophase in structures termed mitotic interchromatin granules (MIGs). We analysed the dynamics of the splicing factor SC35 in interphase and mitotic cells. In HeLa cells expressing green fluorescent protein (GFP)-SC35, this was localized in speckles during interphase and dispersed in metaphase. In telophase, GFP-SC35 was highly enriched within telophase nuclei and also detected in MIGs. Fluorescence recovery after photobleaching (FRAP) experiments revealed that the mobility of GFP-SC35 was distinct in different mitotic compartments. Interestingly, the mobility of GFP-SC35 was 3-fold higher in the cytoplasm of metaphase cells compared with interphase speckles, the nucleoplasm or MIGs. Treatment of cells with inhibitors of cyclin-dependent kinases (cdks) caused changes in the organization of nuclear compartments such as nuclear speckles and nucleoli, with corresponding changes in the mobility of GFP-SC35 and GFP-fibrillarin. Our results suggest that the dynamics of SC35 are significantly influenced by the organization of the compartment in which it is localized during the cell cycle.

    • Purification and molecular cloning of a new galactose-specific lectin from Bauhinia variegata seeds

      Luciano S Pinto Celso S Nagano Taianá M Oliveira Tales R Moura Alexandre H Sampaio Henri Debray Vicente P Pinto Odir A Dellagostin Benildo S Cavada

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      A new galactose-specific lectin was purified from seeds of a Caesalpinoideae plant, Bauhinia variegata, by affinity chromatography on lactose–agarose. Protein extracts haemagglutinated rabbit and human erythrocytes (native and treated with proteolytic enzymes), showing preference for rabbit blood treated with papain and trypsin. Among various carbohydrates tested, the lectin was best inhibited by D-galactose and its derivatives, especially lactose. SDS-PAGE showed that the lectin, named BVL, has a pattern similar to other lectins isolated from the same genus, Bauhinia purpurea agglutinin (BPA). The molecular mass of BVL subunit is 32 871 Da, determined by MALDI-TOF spectrometry. DNA extracted from B. variegata young leaves and primers designed according to the B. purpurea lectin were used to generate specific fragments which were cloned and sequenced, revealing two distinct isoforms. The bvl gene sequence comprised an open reading frame of 876 base pairs which encodes a protein of 291 amino acids. The protein carried a putative signal peptide. The mature protein was predicted to have 263 amino acid residues and 28 963 Da in size.

    • The polymorphisms of bovine cocaine- and amphetamine-regulated transcripts and their associations with cattle (Bos taurus) growth traits

      Chun Lei Zhang Hong Chen Yan Hong Wang Xian Yong Lan Chu Zhao Lei Xing Tang Fang

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      We investigated the polymorphisms of bovine cocaine- and amphetamine-regulated transcripts (CART). The coding and regulating regions of CART were screened in 7 cattle breeds by the single-stranded conformation polymorphism (SSCP) technique. The four loci (C1, C2, C3 and C4) studied were all polymorphic. Polymerase chain reaction (PCR) products representing different SSCP variants were sequenced and a total of 9 single-nucleotide polymorphisms (SNPs) were found. The associations between polymorphic loci and the growth traits of Nanyang cattle were analysed. The results indicated that genotype A1A1 of the C1 locus was associated with a higher body weight (𝑃 < 0.05) than heterozygous A1B1. Genotype A2A2 of the C2 locus was associated with lower body weight and average daily weight gain (𝑃 ≤ 0.001) than heterozygous A2B2. C3 and C4 loci had no significant effect on Nanyang cattle growth traits (P > 0.05).

    • Impact of cytomixis on meiosis, pollen viability and pollen size in wild populations of Himalayan poppy (Meconopsis aculeata Royle)

      V K Singhal Puneet Kumar

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      We report the occurrence of cytomixis in wild populations of Himalayan poppy (Meconopsis aculeata Royle), which is considered to be an important and threatened medicinal plant growing in the high hills of the Himalayas. The impact of cytomixis on meiotic behaviour, reduced pollen viability and heterogeneous-sized pollen grains was also studied. Cytological studies in the seven wild populations from the high hills of Himachal Pradesh revealed that all the Himalayan populations exist uniformly at the tetraploid level (2n=56) on x=14. The phenomenon of chromatin transfer among the proximate pollen mother cells (PMCs) in six populations caused various meiotic abnormalities. Chromatin transfer also resulted in the formation of coenocytes, aneuploid, polyploid and anucleated PMCs. Among individuals that showed chromatin transfer, chromosome stickiness and interbivalent connections were frequently observed in some PMCs. The phenomenon of cytomixis in the species seems to be directly under genetic control; it affects the meiotic course considerably and results in reduced pollen viability.

    • Spatio-temporal tumour model for analysis and mechanism of action of intracellular drug accumulation

      Somna Mishra V K Katiyar

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      We have developed a one-dimensional tumour simulator to describe the biodistribution of chemotherapeutic drugs to a tumoral lesion and the tumour cell’s response to therapy. A three-compartment model is used for drug dynamics within the tumour. The first compartment represents the extracellular space in which cells move, the second corresponds to the intracellular fluid space (including cell membrane) which is in direct equilibrium with the extracellular space, and the third is a non-exchangeable compartment that represents sequestered drug which is trapped in the nucleus to damage the cellular DNA, directly triggering cell death. Analytical and numerical techniques (Finite Element Method) are used to describe the tumour’s response to therapy and the effect of parameter variation on the drug concentration profiles in the three compartments.

    • Patchiness in a minimal nutrient – phytoplankton model

      Hiroshi Serizawa Takashi Amemiya Kiminori Itoh

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      We present a minimal two-component model that can exhibit various types of spatial patterns including patchiness. The model, comprising nutrients and phytoplankton, includes the effect of nutrient uptake by phytoplankton as a Holling type II functional response, and also includes the effect of zooplankton grazing on phytoplankton as a Holling type II non-dynamical term. The mean-field model without the diffusion and advection terms shows both bistability and limit-cycle oscillations as a few parameters such as the input rate of nutrients and the maximum feeding rate of zooplankton are changed. If the parameter values are chosen from the limit-cycle oscillation region, the corresponding reaction–advection–diffusion equations show spatial pattern formations by the combined effects of advection and diffusion by turbulent stirring and mixing, and biological interactions. As the nutrient input is increased, the system behaviour changes from the extinction of the entire phytoplankton to the formation of filamentous patterns, patchiness patterns and homogeneous distributions. These observations suggest that the spatial pattern of phytoplankton can function as an indicator to evaluate the eutrophication level in aquatic ecosystems.

    • Astrocyte, the star avatar: redefined

      Pankaj Seth Nitin Koul

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      Until recently, the neuroscience community held the belief that glial cells such as astrocytes and oligodendrocytes functioned solely as “support” cells of the brain. In this role, glial cells simply provide physical support and housekeeping functions for the more important cells of the brain, the neurons. However, this view has changed radically in recent years with the discovery of previously unrecognized and surprising functions for this underappreciated cell type. In the past decade or so, emerging evidence has provided new insights into novel glial cell activities such as control of synapse formation and function, communication, cerebrovascular tone regulation, immune regulation and adult neurogenesis. Such advances in knowledge have effectively elevated the role of the astrocyte to one that is more important than previously realized. This review summarizes the past and present knowledge of glial cell functions that has evolved over the years, and has resulted in a new appreciation of astrocytes and their value in studying the neurobiology of human brain cells and their functions. In this review, we highlight recent advances in the role of glial cells in physiology, pathophysiology and, most importantly, in adult neurogenesis and “stemness”, with special emphasis on astrocytes.

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