• Volume 24, Issue 2

      June 1999,   pages  139-251

    • RNA-mediated signalling: a new information superhighway in plants?

      Abhilasha Gulati

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    • Model organisms in biology: Scientific and other uses

      M G Narasimhan

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    • The control of tuberculosis: a continuous game of snakes and ladders

      T Ramakrishnan P Chandrasekhar

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    • Elucidation of the lesions present in the transcription defectivefitA76 mutant ofEscherichia coli: Implication of phenylalanyl tRNA synthetase subunits as transcription factors

      Sandhya Ramalingam M Hussain Munavar S Sudha A Ruckmani R Jayaraman

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      Earlier reports from our laboratory dealt with the identification, mapping and characterization of a temperature sensitive mutant (fitA76) with a primary transcription defect at 42‡C and two of its suppressors (fitA24 andfitB). We report here the cloning and molecular characterization of a 2-1 kb DNA fragment which complemented the Ts phenotype of thefitA76 andfitA24 mutants but not that due to thefitB mutant. Cloning of this fragment in the T7 expression vector pT7.5 revealed the synthesis of a 33 kDa protein. The fragment hybridized with the Kohara phages 322 and 323 whose overlapping regions includepheS,pheT andrplT genes. Nucleotide sequencing showed that the fragment contains the entirepheS gene and the N-terminal portion ofpheT. Although these results implied that thefitA andpheS genes could be one and the same, earlier data had ruled out such a possibility. In order to know whether thefitA76 mutation defines a novel allele ofpheS, thepheS region of thefitA76 mutant was also sequenced, revealing a G → A nucleotide transition at position 293 of the coding region. This lesion is the same as that reported for thepheS5 mutant. However, it is shown that thefitA76 mutant is primarily transcription-defective while thepheS5 mutant is primarily translation-defective. These results suggested that thefitA76 mutant might harbour another mutation, in addition topheS5. In this report, we present genetic evidence for a second mutation (namedfit95) in thefitA76 mutant. Thefit95 by itself confers a Ts phenotype on rich media devoid of sodium chloride. It is proposed that the subunits of phenylalanyl tRNA synthetase could act as transcription factors (Fit) also.

    • TCRVΒ17 gene polymorphism in wild populations of IndianMus musculus

      M Awasthi P A Cazenave S Rath R K Anand

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      The Indian house mouse populations, in addition to extreme polymorphism for nuclear genes encoding for various isozymes and mitochondrial DNA also show a high level of variation for the TCRVΒ17 gene. RFLP analysis has revealed six variant forms of the gene which are classified on the basis of size of the restriction fragment. These forms are not present in the laboratory inbred strains. The new alleles are present at different frequencies in nine Indian localities. Gene expression study showed that all the alleles are functional and expressed, though at varying levels. No case of clonal deletion was observed in these animals. Variable expression levels of theVΒ17 gene in these natural populations of mice might be under the control of the MHC haplotype.

    • Acute and transient effects of stress on immunoreactive somatostatin cell bodies and fibers in the preoptic-anterior hypothalamus and median eminence of female rats

      Maheep Bhatnagar

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      Stress in rats causes acute release of hypothalamic somatostatin (SS) in median eminence (ME) that induces a marked and prolonged suppression of growth hormone (GH) secretion. This was evidenced by immunocytochemistry (ICC) and radioimmunoassay (RIA) in the present study. Adult female rats were decapitated under nonstress or for 30, 60, 120 and 180 min after 15 min leg restraint stress. The rabbit anti-SS was used to detect SS-14 and SS-28 containing cell bodies with ICC in preoptic-anterior hypothalamus (PO-AH). At 30, 60, 120 min after stress, there was marked decrease in the number and size of subsets of SS cell bodies. RIA demonstrated striking increase in SS in ME and significant decrease in GH of the portal blood. The most reproducible changes in cell bodies involved subsets of PeV neurons. Interestingly, these changes were largely reversed by 180 min. The results of the study demonstrate that stress cause acute changes in PO-AH, SS system and it appears that stress affects both SS synthesis and the secretion.

    • Age-specific differences in blood pressure among inbred and non-inbred north Indian children

      Badaruddoza Mohammad Afzal

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      Genetic and inbreeding influences on systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial blood pressure (MBP) were examined among 3015 children (1527 males and 1488 females) from the Aligarh district, Uttar Pradesh in north India. The subjects included offspring of first cousins, first cousins once removed, second cousins and unrelated spouses from the same population. The measurements of the inbred children were compared with those of their non-inbred relatives in at least 80% of the cases (matched controls). Two unique findings emerge from this study. First a consistent increase in mean values of SBP, DBP and MBP with increasing inbreeding coefficients have been observed among all age groups, including both the sexes. The results suggest that the hypothesis for a recessive gene or genes could be held responsible for higher BP. Secondly, the effects of inbreeding on mean blood pressure among children and adults may not necessarily be in the same direction. It can be said, therefore, that studies on inbreeding effects using matched controls may provide more direct information regarding the genetics of blood pressure, which has been considerably underestimated in earlier studies.

    • Isolation and immunochemical characterization of neuropeptides from the midgut of the Colorado potato beetleLeptinotarsa decemlineata

      D Muraleedharan D Sheela Devi

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      The midgut of the Colorado potato beetle showed endocrine cells immunopositive to monoclonals like MAC-18, MAC-3 and polyclonals to FMRF-amide and AKH-241. Extraction and HPLC-fractionation of the midgut extracts after partial purification and characterization showed immunopositive reaction to the monoclonals and also showed myotropic activity stimulating the potato beetle gut. Molecular mass of the two active peptides isolated were 22 and 26 kDa respectively. Both these peptides could be immunocytochemically demonstrated in the brain neurosecretory cells of the red cotton bug,Dysdercus cingulatus and the castor semilooper,Achaea janata as well.

    • Ultrastructural evidence for the presence of secretory cells in the pineal parenchyma ofHeteropneustes fossilis

      S Srivastava

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      There is an extensive literature dealing with the study of indoles, especially serotonin and melatonin, but with considerably less emphasis on the cells and cell types involved in the synthetic process. In the present electron microscopical investigation of the pineal end vesicle ofHeteropneustes fossilis, pinealocytes have been revealed in the pineal parenchyma characterized with extensive synthetic apparatus viz., rough endoplasmic reticulum, free ribosomes, lipid droplets, mitochondria and Golgi bodies. Two sub-populations of the pinealocytes are easily distinguishable on the basis of electron opacity and the preponderance of one or other morphological profile: light cells and dark cells. Light cells represent the active phase of secretion while dark cells represent the storage and release phase of secretion. A neuroendocrine role for the pineal body inHeteropneustes fossilis is suggested which may be significant in view of the nocturnal habit of the fish.

    • Age-dependent changes of the ion content and the circadian leaf movement period in thePhaseolus pulvinus

      W -E Mayer B Bok A Rieger

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      The circadian movement of the lamina of primary leaves ofPhaseolus coccineus L. depends on circadian changes of the K+, Cl- and (depending on the Cl- availability) malate content in the swelling and shrinking motor cells of the laminar pulvinus. After sowing in soil, the laminar pulvinus develops within about 26 days. When the leaves emerge from the soil (about 6 days after sowing) and the pulvinus starts with the diurnal movement (about 9 days after sowing) the pulvinar dimensions are about half of those of the mature pulvinus. The anatomical structure, however, is basically the same as in the developed pulvinus. In soil-grown plants, the K+, Cl- and malate content as well as the period length of the circadian leaf movement rhythm change in the developing pulvinus. In the embryo of the dry seed, the Cl- content is low (0.03 mmol g-1 DW), the K+ content, however, 22-fold higher than the Cl- content. When the leaves emerge from the soil, the pulvinar K+ and Cl- content is the same as in the whole embryo of the dry seed. In the developing pulvinus the K+ content increases by a factor of 2 and the Cl- content by a factor of 41 in the mature pulvinus. The pulvinar malate content increases between the 6th and 10th day from about 40 to 180Μmol g-1 DW, then decreases until the 17th day and remains thereafter on a low level (around 80 Μmol g-1 DW). These results indicate that the Cl- availability increases in the developing pulvinus with age. It explains furthermore why in young leaves malate was found as counterion to K+ in the osmotic leaf movement motor, in older ones, however, Cl-. The circadian leaf movement starts 9 days after sowing. The period length decreases during the development of the pulvinus from 31.3 to 28.6 h in leaves of intact soil-grown plants. In leaves which were cut from the plants and immersed with their petioles in distilled water, the age dependent decrease of the period length is also found. However, the period lengths are shorter by more than 1 h than in the leaves of intact plants. The increasing Cl- availability in the developing pulvinus does not seem to be the cause for the age dependent shortening of the period length, because the period length in 22 days old Cl- deprived pulvini is the same as in 22 days old pulvini with a high Cl- content.

    • Efficacy ofTrichoderma chitinases againstRhizoctonia solani, the rice sheath blight pathogen

      J Krishnamurthy R Samiyappan P Vidhyasekaran S Nakkeeran E Rajeswari J A J Raja P Balasubramanian

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      Thirty-five strains ofTrichoderma viride andT. harzianum were screened for their antagonistic ability against the rice sheath blight pathogen,Rhizoctonia solani. The strains that inhibited/overgrew the phytopathogenic fungus were considered effective. Light microscopic studies showed the antagonism of the hyphae of effectiveTrichoderma strains towards their host hyphae. Chitinase activity ofTrichoderma culture filtrates was enhanced, when colloidal chitin was used as the sole carbon source, instead of glucose. Chitinase pattern differed among the four select strains. The chitinase isoforms are induced differentially by carbon sources. The chitin affinity column fraction ofTrichoderma culture filtrate inhibited,in vitro, the growth ofR. solani.

    • Analysis of rice mitochondrial genome organization using pulsed-field gel electrophoresis

      P Senthilkumar K K Narayanan

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      Most of the plant mitochondrial (mt) genomes that have been mapped are believed to be organized as master circle molecules from which sub-genomic molecules arise through homologous recombination. We have evidence to suggest that a major part of the rice mt genome is organized as independent, sub-genomic molecules or mt chromosomes, one of which has already been mapped. This study is aimed at the identification of the other molecular entities that comprise the genome.

      Pulsed-field gel electrophoresis of the native rice mt DNA and Southern analysis with different mt gene probes have shown that in addition to the 117 kb mt chromosome, at least four more such molecules of sizes 130 kb, 95 kb, 70 kb and 56 kb account for most of the rice mt genome. A majority of the rice mt genes that encode products involved in oxidative phosphorylation are distributed among these five chromosomes. Partial restriction map of the 95 kborf 25/cox 3 chromosome, indicating the sites for the enzymesBglII andHindIII has also been determined.

    • Life history response of the mustard aphidLipaphis erysimi to phenological changes in its host

      B K Agarwala N Datta

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      The mustard aphid,Lipaphis erysimi (Kaltenbach) is a serious pest of mustard in India and other tropical regions in the world. The population dynamics of this species is considerably influenced by immigrant alatae which migrate to the mustard crop from the off-season shelter. Aphids reproduce at a higher rate in the early vegetative stage of mustard plants when the developmental period is shortest and production of winged morphs is lowest. The population reaches an asymptote when the crop is 70 days old. The species regulates its developmental period, fecundity and intrinsic rate of increase in response to developmental changes of the mustard plant and maintains its dispersal throughout the duration of the mustard crop. In succeeding generations on a mustard plant new born nymphs took increasingly longer to develop into adults and over the same period these adults produced decreasingly fewer numbers of offspring. In the inflorescence and fruiting stages of mustard plants a higher proportion of the nymphs developed into alatae.

    • Insect drift over the northern Arabian sea in early summer

      S C Pathak Vandana Kulshrestha Arun Kumar Choubey A H Parulekar

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      Air borne insects, mostly carried by wind currents, were trapped over the northern Arabian sea (16‡ to 20‡ N; 68‡ to 72‡ E), in the course of cruise No. 111, ORVSAGAR KANYA (March 14 to April 7, 1996). A total of 2,301 insects belonging to 8 different orders, 47 families and 173 species were trapped. Of these, Hymenoptera was represented by the largest number (1082), which was followed by Hemiptera (586), Diptera (552), Coleoptera (51), Neuroptera (10), Trichoptera (03), Lepidoptera (03) and Orthoptera (01). The trapped insects were mostly between 0.6 mm to over 11 mm long. The data was examined for α-diversity as well as for possible correlations between various parameters like the diversity index, size and number of insects trapped on one hand and the distance of the nearest land mass in wind direction, on the other.

    • Evolution of chemical signals in the Asian elephant,Elephas maximus: behavioural and ecological influences

      L E L Rasmussen

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      In antiquity, the Asian elephant,Elephas maximus, gradually spread southward and eastward to become a successfully surviving, ecologically dominant megaherbivore in the tropical environment of south-east Asia. The changing physical environment forced dynamic fluxes in its social structure and altered its metabolism. Such events shaped the production and ultimately the stability of certain chemicals released by body effluvia. Some of these chemicals took on significance as chemical signals and/or pheromones. This article demonstrates by experimental and observational evidence, and hypothesizes based on speculative reasoning, how and why specific chemical signals evolved in the modern Asian elephant. Evidence, including the functional criteria required by elephant social structure and ecology, is presented for the hypothesis that the recently identified female-emitted, male-received sex pheromone, (Z)-7-dodecenyl acetate evolved first as a chemical signal. Subsequently, the cohesiveness and harmony of small, matriarchally-led female groups were strengthened by a female-to-female chemical signal, recently defined behaviourally. The looser societal structure of freer, roaming males also became bounded by chemical signals; for the males, breath and temporal gland emissions, as well as urinary ones function in chemical signalling. Basic knowledge about elephant chemical signals is now linking chemical information to behaviour and beginning to demonstrate how these signals affect elephant social structure and enable the species to cope with environmental changes.

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