Binding of simple carbohydrates and some N-acetyllactosamine-containing oligosaccharides to Erythrina cristagalli agglutinin as followed with a fluorescent indicator ligand

Erythrina cristagalli agglutinin, a dimeric lectin [J. L. Iglesias, et al. (1982) Eur. J. Biochem.123, 247–252] was shown by equilibrium dialysis to be bivalent for 4-methylumbelliferyl-β-d-galactoside. Upon binding to the lectin, this ligand showed a difference absorption spectrum with two maxima (at 322 and 336 nm) of equal intensity (Δ? = 1.2 × 10³m^?1 cm^?1). A similar spectrum with a comparable value of Δ? was obtained with 4-methylumbelliferyl-N-acetyl-β-d-galactosaminide. Binding of methyl-α-d-galactoside, lactose, and N-acetyllactosamine all produced small but equally intense protein difference spectra with a maximum (Δ? = 2.8 × 10² M^?1 cm^?1) at 291.6 nm. Upon binding of N-dansyl-d-galactosamine to the lectin, there was a fivefold increase in fluorescence intensity of this ligand. The association constant for N-dansyl-d-galactosamine was caused by a very favorable ΔS° of the dansyl group without affecting the strictly carbohydrate-specific character of binding. N-Dansyl-d-galactosamine was employed as a fluorescent indicator ligand in substitution titrations. This involved the use of simple carbohydrates, N-acetyllactosamine, and oligosaccharides which occur in the carbohydrate units of N-glycoproteins; the latter were Gal(β → 4)GlcNAc(β1 → 2)Man, Gal(β1 → 4)GlcNAc(β1 → 6)Man, and Gal(β1 → 4)GlcNAc(β1 → 6)[Gal(β1 → 4)GlcNAc(β1 → 2)]Man. The titrations were performed at two temperatures to determine the thermodynamic parameters. In the series N-acetyl-d-galactosamine, methyl-α-d-galactoside, and lactose, ?ΔH° increased from 24 to 41 kJ mol^?1; it increased further for N-acetyllactosamine and then remained unchanged for the N-acetyllactosamine-containing oligosaccharides (55 ± 1 kJ mol^?1). This indicated that the site specifically accommodated the disaccharide structure with an important contribution of the 2-acetamido group in the penultimate sugar. Beyond this, no additional contacts seemed to be formed. This conclusion also followed from considerations of ΔS° values which became more unfavorable in the above series (?23 to ?101 ± 4 J mol^?1 K^?1); the most negative value of ΔS° was observed with N-acetyllactosamine and the three N-acetyllactosamine-containing oligosaccharides.     

Fungal flora of the digestive tract of 5 species of triatomines vectors of Trypanosoma cruzi,Chagas 1909

A study of the mycobiota in the digestive tract of 5 important species of triatomines, Triatoma brasiliensis, T. infestans, T. sordida, T. pseudomaculata and T. vitticeps, was made. The digestive tracts of 164 adults and 535 nymphs of those triatomines were studied and 393 fungal strains were isolated.The genera with the greatest number of species were Penicillium (19 species), Aspergillus (17 species) and Acremonium (5 species) and the most frequent species, in decreasing order, were Penicillium corylophilum, Aspergillus niger, Penicillium fellutanum, Cladosporium herbarum, Penicillium waksmanii, Aspergillus awamori and Paecilomyces variotii. Among the isolated fungi, we found species that are recognized as entomopathogenic and pathogenic for humans and animals.This revised version was published online in October 2005 with corrections to the Cover Date.     

Vertical stratification of figs and fig-eaters in a Bornean lowland rain forest: how is the canopy different?

Fig trees (Ficus spp; Moraceae) are a common constituent of many tropical forests, where they produce figs that are eaten by a wide range of bird and mammal species. In our Bornean field site six Ficus seed dispersal guilds can be recognised, differentially attracting subsets of the frugivore community. Guild membership appears to be determined by figs' size, colour, crop size and height above ground, and frugivores' size, sensory and locomotory physiology and foraging height. Vertical stratification therefore appears to be an important determinant of fig and frugivore partitioning. The guild structure observed is discussed with respect to implications for seed dispersal and the differences between the canopy and understorey. Regarding figs eaten primarily by birds, larger fruit and crops can be found in the canopy where they are exposed to larger assemblages of potential frugivores than those presented in the understorey.     

Lipid peroxidation, carbohydrate hydrolysis, and Amadori-Maillard reaction at early stages of dry seed aging

Processes underlying aging of air-dry seeds were investigated. Naturally aged seeds of pea (Pisum sativum L.), cucumber (Cucumis sativus L.), and buckwheat (Fagopyrum esculentum Moench.) were separated into three fractions of different quality according to their room temperature phosphorescence (RTP): fraction I contained strong seeds; fraction II comprised weak seeds; and fraction III was composed of dead seeds. These seed fractions were used to identify the processes in air-dry seeds that account for the initial deterioration in seed quality at early stages of aging and for the possible transient improvement of seed quality at further aging. Experiments with seed powders showed that the increase in thermochemiluminescence (TCL) in the temperature range of 50?C110°C was determined by the presence of lipid peroxidation products. No difference was observed between TCL levels in fraction I and fraction II seeds; hence, lipid peroxidation is not responsible for the transition of strong seeds to the fraction of weak seeds. The TCL intensity monitored upon heating in the range of 50?C110°C increased only in the fraction of dead seeds. In fraction II seeds, a twofold increase in TCL upon heating at 150°C was observed in aged seeds; this indicates that the products of oligosaccharide hydrolysis (glucose) were more abundant in fraction II seeds than in fraction I seeds under similar conditions. This assumption was confirmed by direct determination of glucose content with a glucometer. Hence, the transition of air-dry seeds from fraction I (strong seeds) to fraction II (weak seeds) occurred due to the activation of carbohydrate hydrolysis in aging seeds. Since air-dry seeds contain no free water during aging, the seed moisture content decreases during hydrolysis, presumably, because the bound water participates in the hydrolysis reaction. The decrease in ??improved?? seeds of glucose content and the increase in moisture content suggest the activation of amino-carbonyl reaction. It is proposed that the amino-carbonyl (Amadori-Maillard) reaction is responsible for closing water channels in improved seeds, as well as for the decreased water permeability of cell membranes during seed imbibition.     

In vitro adventitious root induction in Antirrhinum majus L.

A broadly applicable method for the successful induction of root systems in a number of cultivars of A. majus has been determined. This involves a double filter-paper bridge with a liquid medium for root induction and allows the transfer of culture-grown plantlets to a glasshouse environment with minimal disturbance to the plant as a whole. 100% survival of transferred plantlets has been achieved with the inclusion of a few simple precautions upon shoot transfer and during the initial stages of plant establishment in vivo.     

A wireless communication system for determining site fidelity of juvenile dusky groupers Epinephelus marginatus (Lowe, 1834) using coded acoustic transmitters

The value of marine reserves to protect threatened and vulnerable species, such as the dusky grouper (Epinephelus marginatus), is often uncertain because of a lack of knowledge about their ecology and habitat utilisation. To address this issue, a Wireless Communication System for location-based positioning of fish tagged with coded acoustic transmitters was installed to determine site fidelity of juvenile dusky groupers (mean total length = 30.4 cm, range: 20.5–40.0 cm; mean total weight = 470 g, range: 113–950 g) within a marine reserve (Island of Ustica, Sicily, Italy). The system was based on five wireless hydrophones distributed approximately 200 m apart along the coastline of the reserve, each monitoring acoustic signals from transmitters within a reception cell. The hydrophones retransmitted detected signals as a radio signal to a land-based receiver and data logger. Unique identifiers for each hydrophone permitted the identification of the detection cell containing the tagged fish. The wireless hydrophones had partly overlapping detection ranges, dividing the marine reserve into more than five different detection cells. The average detection range was 232 m, but coverage varied from site to site and with time, depending on many factors, such as ambient noise, wave action and signal strength of the transmitters. Despite some limitations, the Wireless Hydrophone System (WHS) combined with manual tracking provided a valuable tool for investigating site fidelity in the dusky grouper. Preliminary home ranges for the fish were estimated by the kernel method (probability level of 95%), based on a limited set of manual tracking data, to be a median 5312 m² (range 1673–18626 m²).     

Characterising spatial and temporal variation in the finite rate of population increase across the northern range boundary of the annual grass <Emphasis Type="Italic">Vulpia fasciculata</Emphasis>

Understanding the factors that influence plant distributions is a considerable challenge for ecologists in the face of environmental change. Here, we quantify spatial and temporal variation in the finite rate of population increase of the annual grass Vulpia fasciculata. Specifically, we test the hypothesis that the northern range boundary is associated with finite rates of population increase of less than one. Seeds of three ecotypes of the annual grass V. fasciculata were introduced annually across a range of sites in Great Britain both within (11) and to the north (4) of its current range boundary in each of 4 years. Populations failed to establish at 17% of target sites due to disturbance. At the remaining target sites, the finite rate of population increase, λ, varied from 0.06 to 33.3 with a geometric mean of 1.88. Of the total variance in the rate of population growth, site and year effects accounted independently for 40% of the variation and in interaction for 50%; ecotype accounted for less than 5% of the variation. Variation in the weather between sites and years had little impact on plant performance, and there was no indication that the rate of population growth was lower to the north of the current range boundary. We conclude that current climatic conditions on the coast of Great Britain are not limiting the distribution of V. fasciculata and that seeds from across its current range have roughly equivalent colonising potential.