• Volume 28, Issue 6

      December 2003,   pages  647-810

    • Clipboard: Het up mould unleashes a sporekiller prion

      Durgadas P Kasbekar

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    • Clipboard: Bone marrow stromal cells and multi-lineage differentiation

      Paturu Kondaiah

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    • Commentary: Global warming and terrestrial carbon sequestration

      Gamini Seneviratne

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    • Commentary: Ilya Prigogine (1917–2003)

      Albert Goldbeter

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    • Commentary: G Neuweiler: An appreciation

      M K Chandrashekaran

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    • After DNA at the MRC

      Anand Sarabhai

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    • The conservation of redundancy in genetic systems: effects of sexual and asexual reproduction

      J A Morris R D Morris

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      The relationship between probability of survival and the number of deleterious mutations in the genome is investigated using three different models of highly redundant systems that interact with a threatening environment. Model one is a system that counters a potentially lethal infection; it has multiple identical components that act in sequence and in parallel. Model two has many different overlapping components that provide threefold coverage of a large number of vital functions. The third model is based on statistical decision theory: an ideal detector, following an optimum decision strategy, makes crucial decisions in an uncertain world. The probability of a fatal error is reduced by a redundant sampling system, but the chance of error rises as the system is impaired by deleterious mutations. In all three cases the survival profile shows a synergistic pattern in that the probability of survival falls slowly and then more rapidly. This is different than the multiplicative or independent survival profile that is often used in mathematical models. It is suggested that a synergistic profile is a property of redundant systems.

      Model one is then used to study the conservation of redundancy during sexual and asexual reproduction. A unicellular haploid organism reproducing asexually retains redundancy when the mutation rate is very low (0.001 per cell division), but tends to lose high levels of redundancy if the mutation rate is increased (0.01 to 0.1 per cell division). If a similar unicellular haploid organism has a sexual phase then redundancy is retained for mutation rates between 0.001 and 0.1 per cell division. The sexual organism outgrows the asexual organism when the above mutation rates apply. If they compete for finite resources the asexual organism will be extinguished. Variants of the sexual organism with increased redundancy will outgrow those with lower levels of redundancy and the sexual process facilitates the evolution of more complex forms. There is a limit to the extent that complexity can be increased by increasing the size of the genome and in asexual organisms this leads to progressive accumulation of mutations with loss of redundancy and eventual extinction. If complexity is increased by using genes in new combinations, the asexual form can reach a stable equilibrium, although it is associated with some loss of redundancy. The sexual form, by comparison, can survive, with retention of redundancy, even if the mutation rate is above one per generation.

      The conservation and evolution of redundancy, which is essential for complexity, depends on the sexual process of reproduction.

    • Protein evolution: intrinsic preferences in peptide bond formation: a computational and experimental analysis

      Subramania Ranganathan Dinabandhu Kundu S D Vudayagiri

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      Two possibilities exist for the evolution of individual enzymes/proteins from a milieu of amino acids, one based on preference and selectivity and the other on the basis of random events. Logic is overwhelmingly in favour of the former. By protein data base analysis and experiments, we have provided data to show the manifestation of two types of preferences, namely, the choice of the neighbour and its acceptance from the amino end (left) or the carboxyl end (right). The study tends to show that if the 20 proteinous amino acids were made to combine in water, the resulting profile would be nonrandom. Such selectivity could be a factor in protein evolution.

    • The expression of GFP under the control of fibroin promotor in primary ovarian cells of Antheraea pernyi

      Wenli Li Liji Jin Pengcheng Bu Lijia An

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      The fibroin promoter can stably express foreign gene in lepidopteran cells. Total RNA was extracted from the gland of silkworm, Antheraea pernyi and the transcription initiation site of fibroin gene of A. pernyi was identified by RNA ligase mediated rapid amplification of cDNA ends (RLM-RACE). The expression vector (pGFP-N2/Fib) was constructed by use of replacing the CMV promoter with the fibroin promoter. The results of visual screening under a fluorescent inverted microscope and Western blot analysis indicated that the GFP gene was expressed in the primary cells of ovary origins from A. pernyi.

    • Calcium regulates the expression of a Dictyostelium discoideum asparaginyl tRNA synthetase gene

      Jyoti K Jaiswal Vidyanand Nanjundiah

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      In a screen for calcium-regulated gene expression during growth and development of Dictyostelium discoideum we have identified an asparaginyl tRNA synthetase (ddAsnRS) gene, the second tRNA synthetase gene identified in this organism. The ddAsnRS gene shows many unique features. One, it is repressed by lowering cellular calcium, making it the first known calcium-regulated tRNA synthetase. Two, despite the calcium-dependence, its expression is unaltered during the cell cycle, making this the first D. discoideum gene to show a calcium-dependent but cell cycle phase-independent expression. Finally, the N-terminal domain of the predicted ddAsnRS protein shows higher sequence similarity to Glutaminyl tRNA synthetases than to other Asn tRNA synthetases. These unique features of the AsnRS from this primitive eukaryote not only point to a novel mechanism regulating the components of translation machinery and gene expression by calcium, but also hint at a link between the evolution of GlnRS and AsnRS in eukaryotes.

    • Effect of pH, temperature and alcohols on the stability of glycosylated and deglycosylated stem bromelain

      Rizwan Hasan Khan Sheeba Rasheedi Soghra Khatun Haq

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      The biological significance of the carbohydrate moiety of a glycoprotein has been a matter of much speculation. In the present work, we have chosen stem bromelain from Ananas comosus as a model to investigate the role of glycosylation of proteins. Stem bromelain is a thiol protease which contains a single hetero-oligosaccharide unit per molecule. Here, the deglycosylated form of the enzyme was obtained by periodate oxidation. The differences in the glycosylated and deglycosylated forms of the glycoprotein have been studied at various temperatures and pH values, using probes such as loss of enzyme activity and by the changes in fluorescence and circular dichroism spectra. Deglycosylated bromelain showed decreased enzyme activity and perturbed fluorescence and circular dichroism spectra. In addition to this, a comparative study of their activities in different organic solvents showed a marked decrease in case of deglycosylated form of the enzyme. It is thus concluded that glycosylation contributes towards the functional stability of glycoenzymes.

    • Curcumin-induced inhibition of cellular reactive oxygen species generation: Novel therapeutic implications

      M Balasubramanyam A Adaikala Koteswari R Sampath Kumar S Finny Monickaraj J Uma Maheswari V Mohan

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      There is evidence for increased levels of circulating reactive oxygen species (ROS) in diabetics, as indirectly inferred by the findings of increased lipid peroxidation and decreased antioxidant status. Direct measurements of intracellular generation of ROS using fluorescent dyes also demonstrate an association of oxidative stress with diabetes. Although phenolic compounds attenuate oxidative stress-related tissue damage, there are concerns over toxicity of synthetic phenolic antioxidants and this has considerably stimulated interest in investigating the role of natural phenolics in medicinal applications. Curcumin (the primary active principle in turmeric, Curcuma longa Linn.) has been claimed to represent a potential antioxidant and antiinflammatory agent with phytonutrient and bioprotective properties. However there are lack of molecular studies to demonstrate its cellular action and potential molecular targets. In this study the antioxidant effect of curcumin as a function of changes in cellular ROS generation was tested. Our results clearly demonstrate that curcumin abolished both phorbol-12 myristate-13 acetate (PMA) and thapsigargin-induced ROS generation in cells from control and diabetic subjects. The pattern of these ROS inhibitory effects as a function of dose-dependency suggests that curcumin mechanistically interferes with protein kinase C (PKC) and calcium regulation. Simultaneous measurements of ROS and Ca2+ influx suggest that a rise in cytosolic Ca2+ may be a trigger for increased ROS generation. We suggest that the antioxidant and antiangeogenic actions of curcumin, as a mechanism of inhibition of Ca2+ entry and PKC activity, should be further exploited to develop suitable and novel drugs for the treatment of diabetic retinopathy and other diabetic complications.

    • Reconfirmation of antimicrobial activity in the coelomic fluid of the earthworm Eisenia fetida andrei by colorimetric assay

      Weidong Pan Xianghui Liu Feng Ge Tao Zheng

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      A novel tetrazolium salt, 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulphophenyl)-2Htetrazolium (MTS) was used in the assessment of antimicrobial activity in earthworm in the presence of phenazine methosulphate (PMS) as an electron coupling reagent. This activity was purified from the coelomic fluid of the earthworm (ECF), Eisenia fetida andrei (Oligochaeta, Lumbricidae, annelids) using a series of column chromatography techniques and was tested against three Gram-negative strains of Escherichia coli, Pseudomonas aeruginosa, Aeromonas hydrophila and three Gram-positive strains of Staphylococcus aureus, Bacillus megaterium, Arthrobacter sp., respectively. Only the pigment-free eluate of coelomic fluid of the earthworm (ECFPE) showed activity against B. megaterium amongst three isolated active fractions. The anion (DEAE-52) exchange effluent of the ECFPE was reported to have the strongest activity against P. aeruginosa amongst the three active fractions. The 20% acetonitrile eluate (AE) by Sep-Pak C18 cartridge was also tested and showed fair resistance against E. coli, P. aeruginosa and Arthrobacter sp., respectively.

    • Role of ureogenesis in tackling problems of ammonia toxicity during exposure to higher ambient ammonia in the air-breathing walking catfish Clarias batrachus

      Nirmalendu Saha Shritapa Datta Kuheli Biswas Zaiba Y Kharbuli

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      In the present study, the possible role of ureogenesis to avoid the accumulation of toxic ammonia to a lethal level under hyper-ammonia stress was tested in the air-breathing walking catfish Clarias batrachus by exposing the fish at 25 mM NH4Cl for 7 days. Excretion of ammonia by the NH4Cl-exposed fish was totally suppressed, which was accompanied by significant accumulation of ammonia in different body tissues. The walking catfish, which is otherwise predominantly ammoniotelic, turned totally towards ureotelism from ammoniotelism with a 5- to 6-fold increase of urea-N excretion during exposure to higher ambient ammonia. Stimulation of ureogenesis was accompanied with significant increase of some of the key urea cycle enzymes such as carbamyl phosphate synthetase (urea cycle-related), argininosuccinate synthetase and argininosuccinate lyase both in hepatic and non-hepatic tissues. Due to this unique physiological strategy of turning towards ureotelism from ammoniotelism via the induced urea cycle, this air-breathing catfish is able to survive in very high ambient ammonia, which they face in certain seasons of the year in the natural habitat.

    • Antennal sensilla of grasshoppers (Orthoptera: Acrididae) in relation to food preferences and habits

      Hu-Hai Chen Yun-Xian Zhao L E Kang

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      The external structure, i.e. number and distribution of sensillae on male and female antennae of 12 species of grasshoppers belonging to Pamphaginae, Catantopinae, Oedipodinae and Gomphocerinae in the grasslands of Inner Mongolia was investigated using scanning electron microscopy. Five major types of antennal sensillae were detected – trichoid, long basiconic, short basiconic, slender and short basiconic, and coeloconic sensillae. Total number of antennal sensillae varied among different sexes, subfamilies, feeding groups, life forms and eco-forms. Males showed significantly more sensillae than females, due to presence of more short basiconic and coeloconic sensillae. Species under Catantopinae showed more long basiconic sensillae than the others. The Oedipodinae had the highest number of slender and short basiconic sensillae and coeloconic sensillae, followed by Catantopinae and Gomphocerinae; while Pamphaginae had the fewest. The total number of sensillae showed the same trend for these two types amongst the subfamilies as well, species which prefer habits on the ground possessed fewer antennal sensillae than species which prefer to stay on plants. The maximal number of antennal sensillae were observed in hygrophytous species, Chorthippus albomarginatus, in the 12 grasshopper species investigated, although the data is not statistically significant. The general trend which emerged was that species feeding on grass possessed more antennal sensillae, particularly coeloconic sensillae, compared to other feeding group species.

    • Silk formation mechanisms in the larval salivary glands of Apis mellifera (Hymenoptera: Apidae)

      Elaine C M Silva-Zacarin Regina L M Silva De Moraes S R Taboga

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      The mechanism of silk formation in Apis mellifera salivary glands, during the 5th instar, was studied. Larval salivary glands were dissected and prepared for light and polarized light microscopy, as well as for scanning and transmission electron microscopy. The results showed that silk formation starts at the middle of the 5th instar and finishes at the end of the same instar. This process begins in the distal secretory portion of the gland, going towards the proximal secretory portion; and from the periphery to the center of the gland lumen. The silk proteins are released from the secretory cells as a homogeneous substance that polymerizes in the lumen to form compact birefringent tactoids. Secondly, the water absorption from the lumen secretion, carried out by secretory and duct cells, promotes aggregation of the tactoids that form a spiral-shape filament with a zigzag pattern. This pattern is also the results of the silk compression in the gland lumen and represents a high concentration of macromolecularly well-oriented silk proteins.

    • Insights from stable light isotopes on enamel defects and weaning in Pliocene herbivores

      Tamara A Franz-Odendaal Julia A Lee-Thorp Anusuya Chinsamy

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      A high prevalence of enamel hypoplasia in several herbivores from the early Pliocene Langebaanweg locality, South Africa, indicates general systemic stress during the growing years of life. The presence of several linear enamel hypoplasias per tooth crown in many teeth further suggest that these stress events may be episodic. The 𝛿18O values along tooth crowns of mandibular second molars of Sivatherium hendeyi (Artiodactyla, Giraffidae) were used to investigate the cause of the stress events in this tooth type. Results show that weaning in this fossil giraffid occurred at a similar ontogenetic age to that in extant giraffes, and that the observed enamel hypoplasia towards the base of this tooth type manifested post-weaning. Further, high-resolution oxygen isotope analyses across S. hendeyi third molars suggest that the entire development of defective tooth crowns occurred under conditions of increased aridity in which the cool, rainy part of the seasonal cycle was missing. The high prevalence of this defect in many herbivores suggests that climatic conditions were not favourable. This study reiterates the value of stable isotope analyses in determining both the behaviour of fossil animals and the environmental conditions that prevailed during tooth development.

    • A skeletochronological study of growth, longevity, and age at sexual maturity in a population of Rana latastei (Amphibia, Anura)

      Fabio M Guarino Silvia Lunardi Michela Carlomagno Stefano Mazzotti

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      Longevity and age at sexual maturity in an Italian population of Rana latastei were studied by skeletochronology performed on the phalanges. Frogs collected in 1998 and 1999 by drift fences and pitfall traps were marked by toe-clipping. After marking, individuals were released and the cut phalanges were processed for skeletochronological analysis. The maximum age so far recorded was 3 years in males and 4 years in females. The smallest male and female that were sexually mature on the basis of histological analysis of the gonads were 36 and 35 mm snout vent length (SVL), respectively. In both sexes, most individuals were estimated to breed shortly after emergence from their first overwintering. Among the European Brown Frogs, Rana latastei appears to be one of the shortest-lived and one of the first to reach sexual maturity.

    • Blood coagulation factor VIII: An overview

      G M Bhopale R K Nanda

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      Factor VIII (FVIII) functions as a co-factor in the blood coagulation cascade for the proteolytic activation of factor X by factor IXa. Deficiency of FVIII causes hemophilia A, the most commonly inherited bleeding disorder. This review highlights current knowledge on selected aspects of FVIII in which both the scientist and the clinician should be interested.

    • Subject Index

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    • Author Index

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    • Acknowledgements

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