Volume 22, Issue 5
December 1997, pages 529-650
pp 529-536 December 1997
Enhancing factor (EF), a mouse phospholipase A2 (PLA2), has been purified from the small intestines, based on its ability to increase the binding of epidermal growth factor in a radioreceptor assay. EF/PLA2 was found to be localized predominantly in the Paneth cells in the small intestines. Whether mouse intestinal EF/PLA2 is identical/similar to mouse secretory PLA2 was to be determined. Phospholipases are known to play a crucial role in the process of inflammation. This paper reports the presence of trace amounts of EF/PLA2 in the peritoneal exudate cells. Western blot analysis of the acid extracts showed the presence of a 14 kDa immunologically cross-reactive protein. RT-PCR analysis using EF specific primers amplified a ∼700 bp product which was further confirmed to be EF-specific by nested PCR analysis and sequencing. Presence of EF in the peritoneal exudate cells could be a unique mode of transport of growth factor modulator to the site of injury to aid in regeneration/cell proliferation of damaged tissue.
pp 537-543 December 1997
Enhancing factor (EF), a mouse intestinal phospholipase A2 (PLA2), has been isolated and characterized. EF increases the binding of epidermal growth factor (EGF) to A431 cells almost two-fold by interacting with EGF. EF binds to a 100 kDa cell surface receptor and brings about an increase in the binding of EGF. In the present study we demonstrate that EF is a heparin binding protein and at the time of iodination of EF, the heparin binding site of EF has to be protected. Heparin inhibits the enhancing activity of EF as well as the binding of labelled EF to A431 cells. Inhibition of binding of EF to cells by heparin indicates that heparin binding region forms at least part of the receptor binding domain. These data suggest that the receptor for EF on the cell surface could be a heparin sulphate proteoglycan.
pp 545-554 December 1997
Bowman-Birk inhibitors (BBI) isolated from plant seeds are small proteins active against trypsin and/or chymotrypsin. These inhibitors have been extensively studied in terms of their structure, interactions, function and evolution. Examination of the known three-dimensional structures of BBIs revealed similarities and subtle differences. The hydrophobic core, deduced from surface accessibility and hydrophobicity plots, corresponding to the two tandem structural domains of the double headed BBI are related by an almost exact two-fold, in contrast to the reactive site loops which depart appreciably from the two-fold symmetry. Also, the orientations of inhibitory loops in soybean and peanut inhibitors were different with respect to the rigid core. Based on the structure of Adzuki bean BBI-trypsin complex, models of trypsin and chymotryspin bound to the monomeric soybean BBI (SBI) were constructed. There were minor short contacts between the two enzymes bound to the inhibitor suggesting near independence of binding. Binding studies revealed that the inhibition of one enzyme in the presence of the other is associated with a minor negative cooperativity. In order to assess the functional significance of the reported oligomeric forms of BBI, binding of proteases to the crystallographic and non-crystallographic dimers as found in the crystal structure of peanut inhibitor were examined. It was found that all the active sites in these oligomers cannot simultaneously participate in inhibition.
pp 555-565 December 1997
Amino acid sequences of proteinaceous proteinase inhibitors have been extensively analysed for deriving information regarding the molecular evolution and functional relationship of these proteins. These sequences have been grouped into several well defined families. It was found that the phylogeny constructed with the sequences corresponding to the exposed loop responsible for inhibition has several branches that resemble those obtained from comparisons using the entire sequence. The major branches of the unrooted tree corresponded to the families to which the inhibitors belonged. Further branching is related to the enzyme specificity of the inhibitor. Examination of the active site loop sequences of trypsin inhibitors revealed that here are strong preferences for specific amino acids at different positions of the loop. These preferences are inhibitor class specific. Inhibitors active against more than one enzyme occur within a class and confirm to class specific sequence in their loops. Hence, only a few positions in the loop seem to determine the specificity. The ability to inhibit the same enzyme by inhibitors that belong to different classes appears to be a result of convergent evolution.
pp 567-573 December 1997
Phosphorylation of endogeneous phosholipids of rat liver mitochondrial fractions with γ[32P]ATP revealed formation of all the known inositol phospholipids, such as phosphatidylinositol, phosphatidylinositol phosphate and phosphatidylinositol bisphosphate. Additionally, a new inositol phospholipid was detected. Incorporation of [3H]-labelled insositol followed a similar profile. Enzymatic experiments indicated that the new lipid could possibly be phosphatidylinositol trisphosphate. The presence of phosphoinositides-generated second messengers such as diacylglycerol and inositol trisphosphate was also confirmed. Protein kinase C, which acts as mediator between second messengers and nuclear factors, was also found to be present in mitochondria in significant amount. These results suggest that phosphoinositide signal transduction pathway is operative in rat liver mitochondria.
pp 575-583 December 1997
The intranasal route is one of the main routes of Mycobacterium leprae infection and there is paucity of information regarding the mode of spread of the pattern. The adherence ofM.leprae to the nasal mucosa, its trapping within the sinuses of the head, and its fate after entry into the host was studied using mouse model. A comparison of the adherence profile ofM. lepraeandMycobacterium tuberculosisshowed that while larger numbers ofM. tuberculosiswere demonstrated within lungs, greater numbers ofM.leprae were present within the sinuses of the head. Adherence ofM.leprae to the nasal mucosa was dependent on surface integrity since opsonization and heat killing resulted in decreased numbers ofM.leprae in the nasal sinuses and a greater amount entering the lungs. The adherence appeared to the independent of the viability of the bacilli, as similar numbers of formalin-fixed, rifampicin-treated and viableM.leprae entered the lungs in the initial stages. However the numbers of rifampicin-treatedM. lepraein the nasal sinuses were 12-fold lower than the numbers of viableM.leprae. These results indicated that both viability and surface integrity were important in the entry ofM.leprae and it’s consequent dissemination.
pp 585-592 December 1997
Begoniaxelatiorplantlets which regenerated from leaf disk callus showed variations in plant morphology, number of flowers per plant, and flower size. Variations in flowering period, number of flowers per plant, and flower morphology were observed inSaintpaulia ionanthaL. plants directly regenerated from leaf disk explants. The cytokinins, benzylaminopurine and zeatin, tested in the culture medium did not affect the basic plant characteristics including flower colour which remained stable in both species. Micropropagation of selected somaclones having the desirable trait of high number of flowers per plant was stable in the MV2 and MV3 generations.
pp 593-603 December 1997
In northern Western Ghats (India), four tropical habitats with different disturbance levels were monitored for diversity and seasonal patterns in butterfly communities. Species richness was highest in late monsoon and early winter. Majority of the butterfly species also showed abundance peaks in these seasons. Fire played a significant role in determining species composition in fire-afflicted areas and affected flight periods of some species but did not affect species richness. Grazing had a major impact on species composition and it favoured only those Lycaenids and Nymphalids whose caterpillars feed on herbs. In case of one of the sites where phenophases of the larval foodplant and population trend of a small Lycaenid was documented, the population showed rapid increase at the time when the plants were in suitable phenophase for growth of the caterpillars. A possible evolutionary interaction between herb-feeding and non-herb-feeding Lycaenids is proposed.
pp 605-613 December 1997
Energy and economic efficiencies were evaluated on young (6 year) and old (20 year) jhum fields in Mizoram, north-eastern India during second year of cropping, and were compared with those in the first year. The effect of auxiliary measures such as tilling the soil or application of fertilizers (chemical or farm-yard manure or both in combination) was also examined on energy and economic efficiencies. The results indicated that traditional jhum cultivation is labour intensive and energy efficient, producing almost 15–20 times of energy invested. Energy and economic efficiencies decline with shortening of jhum cycle. These efficiencies decline further from first to second year of cropping. Tilling is not useful to improve either energy or economic efficiency. Fertilizer application, which is though profitable from the point of view of economic efficiency, is highly energy inefficient. Application of fertilizers during second year cropping can be encouraged. Organic manuring may be a better option than others to alleviate energy efficiency. However, a combination of organic and inorgamic manuring could be the best option to enhance economic efficiency.
pp 615-625 December 1997
Changes in soil fertility were evaluated on young (6 year) and old (20 year) jhum fields in Mizoram, north-eastern India in response to various operations involved injhum such as slashing and burning of vegetation, cropping period, and intervening fallow period between first and second year cropping. The results demonstrate that the soil is richer in nutrients in old than young field prior to the start of jhum cultivation. Slash burning depletes soil acidity, carbon and nitrogen but elevates phosphorus and cations. Soil fertility declined during first cropping phase, and further declined during second cropping phase. After two cropping years, soil fertility of old field was almost at par with that of young field, signifying that the loss of soil fertility was more in old than young field. A short intervening fallow period between first and second year of cropping did not show any pronounced improvement in soil fertility, though it provided some biomass for second burning. Tilling caused maximum loss to soil fertility. The fertilizer treatments ended with comparable or better soil fertility in comparison to no-treatment plot. There seems to be none of the fertilizer treatments superior over others from the standpoint of ending soil fertility. The unifying conclusions of this series of investigations support the hypothesis that the second year cropping holds promise to reduce the demand for forested land for jhum, and lengthen the jhum cycle substantially.
pp 627-634 December 1997
This paper presents the results of an investigation on the distribution of210Po in Mutharasanallur pond ecosystem. It has been demonstrated that210Po is non-uniformly distributed within the ecosystem. The results of the study show a dissolved210Po concentration in pond water of 1 4mBq 1−1. The sediment samplso recorded a210Po activity of 59 9 Bq kg−1. The aquatic organisms showed differential accumulation of the radionuclide with enhanced bioaccumulation in soft tissues and muscle. The210Po activity in the biota fell within the range of 1·2–53 3 Bq kg−1 (wet wt). The bivalve mussel,Lamellidens marginalis was identified to accumulate higher concentration of210Poin soft tissues, suggesting that these organisms could serve as a bio-monitor of210Po radionuclide in a freshwater system. The concentration factors of210Po for the biotic components ranged from ∼102–∼104. Analyses of the results indicate that prawn and fish represent an important source of supply of210Po to humans via dietary intake. Results of210Po activity in the abiotic and biotic components of the pond ecosystem were higher when compared with those of Cauvery river system, the primary water source of the pond.
pp 649-650 December 1997