Functional response of staging semipalmated sandpipers feeding on burrowing amphipods

Despite its fundamental relevance to many ecological processes in predator–prey relationships, the functional response, which relates predator intake rate to prey density, remains difficult to document in the field. Here, I document the functional response of semipalmated sandpipers (Calidris pusilla) foraging on a burrowing amphipod Corophium volutator during three field seasons at the peak of fall migration in the upper Bay of Fundy (New Brunswick, Canada). I gathered data during the ebbing tide when all sandpipers are highly motivated to feed after a lengthy hide-tide fast. As birds follow the receding tideline, foragers encounter prey at different densities and do not aggregate in the richest food patches. Results show that intake rate increased at a decreasing rate with Corophium density, yielding a type II functional response typical of many shorebird species. Intake rate decreased in the later stages of migration stopover at a time where preferred prey items have been shown to occur at lower densities due to prior depletion. At this period of lower prey availability, intake rate also decreased with sandpiper density providing evidence for interference at low prey density. The results illustrate the fact that the functional response may not be unique but instead vary as a function of the type of competitive relationship among foragers.     

Incubation capacity and clutch size determination in two calidrine sandpipers: a test of the four-egg threshold

Several groups of vertebrate taxa, including shorebirds, are unusual in that they produce a fixed number of offspring. The aim of this study was to examine whether the incubation capacity of western sandpipers (Calidris mauri) and semipalmated sandpipers (C. pusilla) limits their maximum clutch size to four eggs. Experimental enlargement of clutch size had no effect on rates of nest abandonment, nest attendance or loss of body mass by incubating sandpipers. The duration of incubation was significantly longer for enlarged five-egg nests, and there were trends towards increased partial clutch loss and asynchrony at hatch, but overall hatching success was unaffected by experimental egg number. I conclude that small, calidrine sandpipers with biparental care are able to compensate for an additional egg in an enlarged nestbowl, despite the constraints of conically shaped eggs and two brood patches. Possibly, shorebirds do not lay more than a fixed clutch size of four eggs because selection on factors acting during egg production or brood-rearing is more important in regulating offspring number. Received: 20 June 1996 / Accepted: 30 September 1996     

Foraging behaviour of western sandpipers changes with sediment temperature: implications for their hemispheric distribution

Migratory shorebirds need to replenish their energy reserves by foraging at stop-over sites en route. Adjusting their foraging behaviour to accommodate variation in local prey availability would therefore be advantageous. We test whether western sandpipers (Calidris mauri), a sexually dimorphic shorebird, adjust their foraging behaviour in response to local changes in prey availability, as inferred by changes in diurnal time and sediment temperature. Both males and females showed quantitative changes to foraging mode in relation to each of these variables. Probing, for example, which is used to exploit infaunal prey, was significantly more common at higher temperatures. The results presented here are consistent with the notion that western sandpipers can adjust their foraging behaviour in response to variation in prey availability. Further, we speculate that temperature-induced changes to prey location may contribute to the striking sexual segregation observed for this species during the non-breeding season.     

Effect of Azospirillum Lectins on the Activities of Wheat-root Hydrolytic Enzymes

This work studied the effect of two cell-surface lectins isolated from the nitrogen-fixing soil bacterium Azospirillum brasilense Sp7 and from its mutant defective in hemagglutinating activity, A. brasilense Sp7.2.3, on the activities of α-glucosidase, β-glucosidase and β-galactosidase in the exocomponent, membrane and apoplast fractions of wheat-seedling roots. Lectin (40 μg mL⁻¹) incubation for 1 h of the plant fractions increased the enzymes’ activities; both wild-type and mutant lectins were most stimulatory to the activities of all the exocomponent-fraction enzymes studied and to the apoplast-fraction β-glucosidase. Pretreatment of the lectins with their carbohydrate hapten, L-fucose, lowered the effect. The observed differences in the lectins’ ability to influence enzyme catalytic activity are explained by change in the antigenic properties of the mutant lectin.     

The use of norbornene derivatives in the synthesis of conformationally constrained peptides and pseudo-peptides

Summary The desymmetrisation ofendo-norborn-5-ene-2,3-dicarboxylic anhydride by proline esters has been used to prepare conformationally constrained pseudo-peptides with two peptide chains parallel to one another. A Curtius rearrangement on the desymmetrication adduct produced the corresponding isocyanate which was used to prepare both a peptide incorporating anendo-2-amino-3-carboxy-norborn-5-ene unit, and a pseudo-peptide with two peptide chains parallel to one another but offset by the presence of a urea unit. The conformational analysis of the resulting peptides was carried out, and the norbornene unit was found to induce the formation of β-turns and parallel β-sheets.     

Comparison between Yeasts from Grape and Agave Musts for Traits of Technological interest

Summary In Mexico there are different alcoholic beverages produced from agave juices from different agave plants, which are cooked, fermented and distilled. For tequila production only Agave tequilana is allowed. In this study we compared yeast strains of different species from different origin (agave and grape juice) for parameters of technological interest, such as SO₂ and copper resistance, ethanol tolerance and enzymatic activities. All agave strains were found to be more resistant to SO₂ and agave non-Saccharomyces yeasts were more tolerant to ethanol, whereas grape strains exhibited positive results for β-glucosidase and β-xylosidase activities. As regards fermentations of Agave tequilana juice with ethanol added at different concentrations, only agave Saccharomyces strains were more tolerant to ethanol than grape strains.     

Towards a Complex, Plural and Dynamic Approach to Diversity: Rejoinder to Myers and Patil, Podani, and Sarkar

This reply paper includes two brief remarks in rejoinder to the commentary papers of Myers and Patil, Podani, and Sarkar. The first observation concerns the fundamental nature of ecological diversity measures, while the second one specifically addresses some interesting mathematical connections between α- and β-diversity.     

Characterization of Esterases in a Brazilian Population of Zaprionus Indianus (Diptera: Drosophilidae)

The aim of this study was to characterize esterases in Zaprionus indianus, a drosophilid recently introduced into Brazil. A further aim was study the variation of activity of esterases in the presence of inhibitors and their expression according to sex, sexual activity and age of individual flies. Polymorphisms were detected in two esterase loci (Est-2 and Est-3) and monomorphisms in four others (Est-1, Est-4, Est-5 and Est-6). Biochemical tests using α- and β-naphthyl acetate and the inhibitors malathion, eserine sulphate and PMSF allowed us to classify EST-2 and EST-5 as β-esterases, both carboxyl-esterases, and EST-1, EST-3, EST-4 and EST-6 as α-esterases. EST-1 and EST-3 were classified as carboxyl-esterases and EST-4 and EST-6 as cholinesterases. EST-5 activity was more pronounced in males and EST-2 was restricted to them or to recently copulated females. EST-4, rarely detected, was not characterized. Based on their biochemical characteristics possible roles for these enzymes are suggested.     

Transforming growth factor-beta: Its effect on phenotype reexpression by dedifferentiated chondrocytes in the presence and absence of osteogenin

Summary The single and combined actions of transforming growth factor (TGF)-beta and osteogenin were evaluated with regard to induction of colony formation and reexpression of the differentiated phenotype by dedifferentiated rabbit articular chondrocytes in soft agarose under serum-free conditions. TGF-beta alone did not promote colony formation and induced accumulation of proteoglycans and type II collagen at significantly lower levels than those induced by osteogenin. Although synergism between these two growth factors occurred with respect to the induction of colony formation, their joint action on reexpression of the differentiated phenotype was additive. Complex interactions between the two growth factors may explain the latter phenomenon.     

Preparation of Concanavalin A-β-galactosidase conjugate and its application in lactose hydrolysis

A Concanavalin A-β-galactosidase conjugate was prepared using glutaraldehyde as the crosslmking reagent. The conjugate bound to Sephadex G-50 beads was more thermostable and hydrolyzed lactose faster than the free enzyme. The immobilized enzyme may prove useful in the preparation of low lactose milk which is required by persons suffering from lactose intolerance.     

Peptidyl Carbamates: Efficient Synthesis Using N-Fmoc-β-aminoalkoxy Carbonyl Chlorides/Active Pentachlorophenyl Carbonates as Monomeric Building Blocks

A simple protocol for the synthesis of linear peptidylcarbamates employing Fmoc-β-aminoalkoxy carbonyl chlorides is described. The N-Fmoc-β-aminoalkoxy carbonyl chlorides were prepared by the reaction of phosgene or triphosgene with Fmoc-protected β-amino alcohol which were isolated as solids. These oxycarbonyl chlorides were also converted to the corresponding pentachlorophenyl carbonates by reacting with pentachlorophenol. Fmoc-β-aminoalkoxy carbonyl chlorides as well as pentachlorophenol carbonates were successfully used as monomeric building blocks for the synthesis of several peptidyl carbamates.     

Production,purification and application-relevant characterisation of an <Emphasis Type="Italic">endo</Emphasis>-1,3(4)-β-glucanase from <Emphasis Type="Italic">Rhizomucor miehei</Emphasis>

Growth on a wheat bran media induced production of an extracellular β-glucanase by Rhizomucor miehei (DSM 1330). The enzyme was purified to homogeneity. Substrate specificity studies coupled with protein database similarity searching using mass spectrometry-derived sequence data indicate it to be an endo-1,3(4)-β-glucanase (EC 3.2.1.6). The enzyme was characterised in terms of potential suitability for use in animal (poultry) feed. Significant activity was observed over the entire pH range typical of the avian upper digestive tract (pH 2.6–6.5). The enzyme was also found to be more thermostable than current commercialized β-glucanases, particularly when heated at a high enzyme concentration, and retained twice as much residual activity as the latter upon exposure to simulated avian digestive tract conditions. There are no previous reports of the production, purification or characterization of a β-glucanase from a Rhizomucor, and the enzyme’s application-relevant physicochemical characteristics render it potentially suited for use in animal feed.     

Actin cytoskeletal isoforms in human endothelial cellsin vitro: Alteration with cell passage

Summary The microfilamentous actin component of the cytoskeleton is crucial to endothelial angiogenesis and vascular permeability. Differences in actin cytoskeletal profiles in cultured human endothelial cells were explored: when first isolated, both primary human umbilical vein endothelial cells (HUVEC) and primary human placental microvascular endothelial cells (HPMEC) expressed F-actin, but notβ-actin orα-smooth muscle actin. A similar endothelial actin profile was observed in cryo-sections of freshly delivered term umbilical cord and placenta. In subsequent cell culture, although the actin cytoskeleton of HUVEC remained unchanged, the actin profiles of HPMEC altered after the second passage with the induction ofα-smooth muscle actin expression, which was intercellularly heterogeneous and increased to 20% at P4. This behavior occurred in HPMEC monolayers cultured on a variety of extracellular matrices. Comparisons with a spontaneously immortalized human microvascular cell-line, HGTEN 21, revealed that inprolonged passage, bothα-smooth muscle actin andβ-actin were expressed, whereas HPMEC at P4 showed a lower level ofβ-actin expression. Therefore, in comparison with large vessels, microvascular cells are more likely to dedifferentiate. This may reflect the ability of microvascular cells to remodel according to changing requirement for new vessel formation. In conclusion, passage of human microvascular endothelial cells, but not of larger vessel endothelial cells, alters the expression of actin isoforms. This may be important in relation to comparisons ofin vitro andin vivo vascular permeability; higher passage microvascular endothelial cells should thus be used with caution in such studies.     

Using progesterone 5β-reductase, a gene encoding a key enzyme in the cardenolide biosynthesis, to infer the phylogeny of the genus Digitalis

Summary The progesterone 5β-reductase (5β-POR), a key enzyme in the cardenolide biosynthesis, was sequenced for 21 species of Digitalis and Isoplexis to infer phylogenetic and biogeographic relationships. This new secondary metabolism molecular marker was compared to the previously applied nuclear ITS and plastid trnL-F sequences. The results from separate analyses show high congruence within the genus Digitalis and support the conclusion that all species of Isoplexis have a common origin and are embedded in Digitalis. The genus Isoplexis therefore should be reduced to sectional rank within the genus Digitalis. The sequence analyses give further evidence that additional sequence data increase support for relationships. It demonstrates that poorly supported relationships in smaller data sets may lead to erroneous conclusions about the evolution of the investigated taxa.     

Heterologous expression and characterization of man gene from Bacillus Subtilis in Pichia Pastoris

β-Mannanase catalyzes endo-wise hydrolysis of the backbone of mannan and heteromannan, which are abundant in the cell wall structure of ungerminated leguminous seeds. The mature β-mannanase originated from Bacillus subtilis was expressed in Pichia pastoris, a methylotrophic yeast, using the leader peptide sequence of Saccharomyces cerevisiae α-factor. The cultivation of β-mannanase expressing Pichia pastoris yields up to 1.8 g/L protein. In the supernatant the activity of the 40 kDa—total mannanase attained a level of 1102.0 IU/mL. The properties of the β-mannanase were characterized. Optimum pH and temperature for the recombinant enzyme were 5.5 and 50°C respectively. The enzyme was stable at pH 5.0–10.0 and maintained over 30% original activity after incubating at 70°C for 30 min. __________ Translated from China Biotechnology, 2005, 26(7): 52–56 [译自: 中国生物工程杂志]     

New conjugates of antitumor antibiotic doxorubicin with water-soluble galactomannan: Synthesis and biological activity

New water-soluble conjugates in the form of Schiff bases (DGM-1 and DGM-2) were prepared by the interaction of water-soluble periodate-oxidized galactomannan with doxorubicin or N-(L-lysyl)doxorubicin, respectively. The water-soluble galactomannan (DAVANAT®, a commercial product of Pro-Pharmaceuticals company) was obtained by partial acidic hydrolysis of high-molecular-mass galactomannan from Cyamopsis tetragonoloba (guar gum) seeds. The conjugate stability was studied in aqueous solutions. The DGM-1 anti-proliferative activity was comparable with that of doxorubicin on three models: cell lines of murine melanoma B16-F1 and human breast cancer MCF-7 (HTB-22) and human colon cancer HT-29 (HTB-38). DGM-2 was poorly active in all the three tests. DGM-1 can thus be regarded as a high-molecular-mass depot form of doxorubicin.     

Relationship between Poly- β-hydroxybutyrate Production and δ-endotoxin for Bacillus thuringiensis var. kurstaki

A linear relationship between total solid concentration (TSC), δ-endotoxin production [Cry = 0.2795(TSC)−0.2472, R² = 0.8644] and poly-β-hydroxybutyrate (PHB) accumulation [PHB = 0.1327(TSC) + 0.3974, R² = 0.9877] in Bacillus thuringiensis var. kurstaki HD-73 was observed. A similar correlation between δ-endotoxin and PHB accumulation [Cry = 2.1573(PHB)−1.1248, R² = 0.9181] was found. A minimum PHB accumulation of 0.52 mg l⁻¹ was required before the onset of δ-endotoxin production. Revisions requested 28 September 2005 and 4 November 2005; Revisions received 28 October 2005 and 1 February 2006     

1β,7β-Dihydroxydehydroabietic acid,a new biotransformation product of dehydroabietic acid by Aspergillus niger

Microbial transformation of dehydroabietic acid by Aspergillus niger afforded the new derivative 1β,7β-dihydroxydehydroabietic acid and the known 1β-hydroxy and 7β-hydroxy derivatives. The structures were elucidated by spectroscopic methods. The compounds were assessed towards Gram (+) and Gram (−) bacteria and showed a weak antimicrobial effect. This revised version was published online in August 2006 with corrections to the Cover Date.     

Hydrolases as markers of wine aging

Indigenous wine hydrolytic enzymes come from both grape berries and the microorganisms involved in the fermentation process. The levels of these enzymes in wine vary according to the elaboration period and to wine aging; among them invertase and polygalacturonase are enzymes fairly resistant to denaturation and with utility to determine wine aging. Invertase may be employed as a marker of wine aging and it may be also used for differentiating wines from different regions of origin and different grape varieties. Polygalacturonase is a good indicator useful to differentiate the year of harvesting for wines elaborated with the same grape variety. Both enzymes may possibly be used as indicators of potentially fraudulent “aging-accelerated” processes.