Lignans from Piper cubeba

From the hot petrol extract of Piper cubeba ftuits, six lignans were isolated. Two of these, which have been obtained from a natural source for the first time, have been characterized as (2R,3R)-2-(3″,4″,5″-trimethoxybenzyl)-3-(3′,4′-methylenedioxybenzyl)-1,4-butanediol [(?)-dihydroclusin] and (3R,4R)-3,4-bis-(3,4,5-trimethoxybenzyl)tetra-hydro-2-furanol [(?)-cubebinin]. (?)Cubebin, (?)-hinokinin, (?)-clusin and (?)-dihydrocubebin were also found in this plant. Only (?)-cubebin has been reported so far from this source.     

Immobilization of dextranase on bentonite

Dextranase (1,6-α-d-glucan 6-glucanohydrolase, EC 3.2.1.11) from Penicillium aculeatum culture has been immobilized on a bentonite support. The matrix-bound enzyme could be stored as acetone-dried powder or as a suspension in acetate buffer, pH 5.6, for about three weeks at 4°C without any loss of activity. There was no change in the specific activity of the enzyme on immobilization and the enzyme yield was 0.1–0.6 mg/g bentonite matrix. In the presence of sucrose, thermal stability of the immobilized enzyme was high and the bound enzyme could be used for about six cycles.     

Comparison of murine B-cell proliferative response to bacterial lipopolysaccharide and DNP derivative ofMycobacterium tuberculosis antigens

The DNP derivative of sonicate antigens of the H37Ra strain ofMycobacterium tuberculosis (Ra-DNP) is known to induce marked B-cell proliferation. In order to understand whether B-cell proliferation in response to Ra-DNP was antigen driven or represented a non-specific mitogenic effect of Ra-DNP, the effect of Ra-DNP was compared with that of lipopolysaccharide a potent B-cell mitogen. Parameters used for comparison were (i) thymidine incorporation, (ii) viable cell counts, (iii) amount of lg secreted, (iv) isotype profile of Ig released and (v) cell cycling pattern of B-cells in culture. Overall the effect of Ra-DNP was found to be essentially similar to that of lipopolysaccharide for all parameters examined. Yet quantitatively, the effect of the former was always relatively poorer. At optimal doses, the effect of Ra-DNP ranged from 50 to 70% of the lipopolysaccharide effect in different assays. These results suggest that Ra-DNP may have a B-cell mitogenic effect similar to the effect of lipopolysaccharide, but all B-cells may not respond to Ra-DNP.     

Topcats and underdogs: intraguild interactions among three apex carnivores across Asia's forestscapes

Intraguild interactions among carnivores have long held the fascination of ecologists. Ranging from competition to facilitation and coexistence, these interactions and their complex interplay influence everything from species persistence to ecosystem functioning. Yet, the patterns and pathways of such interactions are far from understood in tropical forest systems, particularly across countries in the Global South. Here, we examined the determinants and consequences of competitive interactions between dholes Cuon alpinus and the two large felids (leopards Panthera pardus and tigers Panthera tigris) with which they most commonly co-occur across Asia. Using a combination of traditional and novel data sources (N = 118), we integrate information from spatial, temporal, and dietary niche dimensions. These three species have faced catastrophic declines in their extent of co-occurrence over the past century; most of their source populations are now confined to Protected Areas. Analysis of dyadic interactions between species pairs showed a clear social hierarchy. Tigers were dominant over dholes, although pack strength in dholes helped ameliorate some of these effects; leopards were subordinate to dholes. Population-level spatio-temporal interactions assessed at 25 locations across Asia did not show a clear pattern of overlap or avoidance between species pairs. Diet-profile assessments indicated that wild ungulate biomass consumption by tigers was highest, while leopards consumed more primate and livestock prey as compared to their co-predators. In terms of prey offtake (ratio of wild prey biomass consumed to biomass available), the three species together harvested 0.4–30.2% of available prey, with the highest offtake recorded from the location where the carnivores reach very high densities. When re-examined in the context of prey availability and offtake, locations with low wild prey availability showed spatial avoidance and temporal overlap among the carnivore pairs, and locations with high wild prey availability showed spatial overlap and temporal segregation. Based on these observations, we make predictions for 40 Protected Areas in India where temporally synchronous estimates of predator and prey densities are available. We expect that low prey availability will lead to higher competition, and in extreme cases, to the complete exclusion of one or more species. In Protected Areas with high prey availability, we expect intraguild coexistence and conspecific competition among carnivores, with spill-over to forest-edge habitats and subsequent prey-switching to livestock. We stress that dhole–leopard–tiger co-occurrence across their range is facilitated through an intricate yet fragile balance between prey availability, and intraguild and conspecific competition. Data gaps and limitations notwithstanding, our study shows how insights from fundamental ecology can be of immense utility for applied aspects like large predator conservation and management of human–carnivore interactions. Our findings also highlight potential avenues for future research on tropical carnivores that can broaden current understanding of intraguild competition in forest systems of Asia and beyond.     

Detection and identification of ferricrocin produced by ectendomycorrhizal fungi in the genusWilcoxina

The ectendomycorrhizal fungiWilcoxina mikolae isolates CSY-14 and RMD-947 andW. rehmii isolate CSY-85 were grown in pure culture under iron-limiting conditions. All three isolates tested positive for siderophore formation using both the ferric perchlorate assay and a sensitive HPLC iron-binding assay. A peptide siderophore was isolated from the culture medium by HPLC and shown to contain the amino acids serine, glycine and ornithine in a 1:2:3 ratio. This siderophore was identified as ferricrocin on the basis of electrospray mass spectroscopy and its co-chromatography in two different HPLC systems with ferricrocin isolated fromAspergillus fumigatus. Ferricrocin was the only siderophore isolated from theseWilcoxina cultures. This is the first report of siderophore formation by ectendomycorrhizal fungi.     

Production of high-fructose syrup by a heat-fixed Lactobacillus sp.

A Lactobacillus sp. isolated from soil and capable of growing on xylose-containing medium exhibited high glucose isomerase activity. The enzyme was thermostable, stable toward dialysis, and activated by heat treatment. It did not show the presence of xylose or ribose isomerase activities; the K_m for glucose and xylose substrates were 0.48M and 0.513M, respectively. The heat treatment of ultrasonic crude extract gave insoluble fixed active glucose isomerase enzyme. The properties of free and immobilized enzyme in heat-fixed whole cells differed in many respects. The optimum temperature for enzyme activity changed from 70 to 85°C, the optimum substrate concentration changed from 1.0M to 2.4M, and the optimum pH from 7.4 to 6.0. Co²⁺ and Mg²⁺ ions activated the enzyme when used singly, but in combination they inhibited the enzyme and Mn²⁺ had no effect on the enzyme. Free and immobilized enzymes, when used in the used in the conversions of corn and bagasse hydrolysates to fructose, gave 58, 25.6%, and 50, 27.6% conversions, respectively. Immobilized enzyme retained a significant activity for more than 30 hr and was able to operate at higher glucose concentrations showing less products inhibition effect as compared to free enzyme. In the batch process it was able to operate for about eight cycles.     

Bandwidth Enhancement of Planar Terahertz Metasurfaces via Overlapping of Dipolar Modes

Plasmonics - We present enhancement of operational bandwidths of planar terahertz metasurfaces by incorporating a complex unit cell that consists of a pair of concentric ring resonators. The inner...