Overcoming seed dormancy in visgueiro-of-the-igapó (Parkia discolor)

This study aimed to evaluate the effects of pregerminative mechanical scarification treatments, as well as heat pre-treatments on the germination of visgueiro-of-the-igapó (Parkia discolor Spruce ex Benth.) seeds. The first experiment, with a completely randomized design and four repetitions, evaluated these pre-treatments: control (without pre-treatment); clipping at the distal portion; clipping at the proximal portion (hilum); clipping at the proximal and distal portions; scraping at the distal portion; scraping at the proximal portion; scraping at the proximal and distal portions; perforation of the husk with a soldering-iron; and perforation by pyrography. In the second experiment, with a completely randomized design and factorial 2 (heat: dry and wet) x 4 (temperature: 40ºC, 50ºC, 60ºC and 70ºC) x 5 (period of conditioning: 6, 16, 24, 30 and 48 hours), with three repetitions. The clipping or scraping of the seeds in the proximal portion and proximal and distal portions allowed faster imbibition of the seeds (143-163% in three days and half), and consequently, better germination (98-100% in four days), germination speed rate (1,351-1,460) and average time of germination (3 days). The pre-treatment with heat (wet and dry), under different temperatures and different conditioning periods did not overcome the dormancy of P. discolor seeds.O presente trabalho teve como objetivo avaliar os efeitos da aplicação de tratamentos pré-germinativos de escarificação mecânica, bem como pré-tratamentos com calor, sobre a germinação de sementes de visgueiro-do-igapó (Parkia discolor Spruce ex Benth.). No primeiro experimento, sob delineamento inteiramente ao acaso, com quatro repetições, foram avaliados os pré-tratamentostestemunha (sem pré-tratamento); desponte no lado distal; desponte no lado proximal; desponte nos lados distal e proximal; lixamento no lado distal; lixamento no lado proximal; lixamento nos lados distal e proximal; perfuração do tegumento com ferro-de-solda; e perfuração com pirógrafo. No segundo experimento, foi adotado o delineamento inteiramente casualizado, em esquema fatorial 2 (calorseco e úmido) x 4 (temperatura40ºC, 50ºC, 60ºC e 70ºC) x 5 (período de condicionamento6, 16, 24, 30 e 48 horas), com três repetições. O desponte ou lixamento das sementes na porção proximal e porções proximal e distal possibilitaram uma embebição mais rápida (143-163%, aos três dias e meio) e, conseqüentemente, melhores resultados de germinação (98-100%, aos quatro dias), do índice de velocidade de germinação (1,351-1,460) e do tempo médio de germinação (3 dias). Os pré-tratamentos com calor (úmido e seco), sob diferentes temperaturas, e por vários períodos de condicionamento não superaram a dormência de sementes de P. discolor

Atividade hemaglutinante em sementes de Dioclea rostrata Benth

Sementes de Dioclea rostrata Benth. Têm uma lectina que é melhor extraída em tampão acetato de sódio a pH 4,0 e é seletivamente adsorvida em Sephadex G-50, apresentando um alto título de hemaglutinação contra eritrócitos de coelho. A lectina também aglutina inespecificamente hemácias de carneiro e humanas. A atividade hemaglutinante é inibida por glicose, frutose, manose e alfa-metil-D-manosídeo, sendo os dois últimos os mais potentes inibidores. A lectina é uma metaloproteína, uma vez que a atividade hemaglutinamente desaparece na presença de EDTA.<br>Seeds of Dioclea rostrata Benth. Have a lectin which is best extracted with Na-acetate buffer at pH 4.0 and that is selectively adsorbed in a Sephadex G-50 matrix, yielding a protein fraction of high hemagg lutinating titre against rabbit erythrocytes. It also agglutinates sheep, and human cells inespecifically. Its hemagglutinating activity is inhibited by glucose fructose, mannose and O-methyl-D-mannopyranoside the latter two being the most active inhibitors. The lectin seems to be a metaloprotein since the hemagglutinating activity is lost in the presence of EDTA

A Lectin from Platypodium elegans with Unusual Specificity and Affinity for Asymmetric Complex N-Glycans

International audienceLectin activity with specificity for mannose and glucose has been detected in the seed of Platypodium elegans, a legume plant from the Dalbergieae tribe. The gene of Platypodium eleganslectin A has been cloned, and the resulting 261-amino acid protein belongs to the legume lectin family with similarity with Pterocarpus angolensis agglutinin from the same tribe. The recombinant lectin has been expressed in Escherichia coli and refolded from inclusion bodies. Analysis of specificity by glycan array evidenced a very unusual preference for complex type N-glycans with asymmetrical branches. A short branch consisting of one mannose residue is preferred on the 6-arm of the N-glycan, whereas extensions by GlcNAc, Gal, and NeuAc are favorable on the 3-arm. Affinities have been obtained by microcalorimetry using symmetrical and asymmetrical Asn-linked heptasaccharides prepared by the semisynthetic method. Strong affinity with K-d of 4.5 mu M was obtained for both ligands. Crystal structures of Platypodium elegans lectin A complexed with branched trimannose and symmetrical complex-type Asn-linked heptasaccharide have been solved at 2.1 and 1.65 angstrom resolution, respectively. The lectin adopts the canonical dimeric organization of legume lectins. The trimannose bridges the binding sites of two neighboring dimers, resulting in the formation of infinite chains in the crystal. The Asn-linked heptasaccharide binds with the 6-arm in the primary binding site with extensive additional contacts on both arms. The GlcNAc on the 6-arm is bound in a constrained conformation that may rationalize the higher affinity observed on the glycan array for N-glycans with only a mannose on the 6-arm

Crotacetin, A Novel Snake Venom C-type Lectin Homolog Of Convulxin, Exhibits An Unpredictable Antimicrobial Activity

Snake venom (sv) C-type lectins encompass a group of hemorrhagic toxins that are capable of interfering with blood stasis. A very well-studied svC-type lectin is the heterodimeric toxin, convulxin (CVX), from the venom of South American rattlesnake Crotalus durissus terrificus. CVX is able to activate platelets and induce their aggregation by acting via p62/GPVI collagen receptor. By using polymerase chain reaction homology screening, we have cloned several cDNA precursors of CVX subunit homologs. One of them, named crotacetin (CTC) β-subunit, predicts a polypeptide with a topology very similar to the tridimensional conformations of other subunits of CVX-like snake toxins, as determined by computational analysis. Using gel permeation and reverse-phase high-performance liquid chromatography, CTC was purified from C. durissus venoms. CTC can be isolated from the venom of several C. durissus subspecies, but its quantitative predominance is in the venom of C. durissus cascavella. Functional analysis indicates that CTC induces platelet aggregation, and, importantly, exhibits an antimicrobial activity against Gram-positive and -negative bacteria, comparable with CVX. © Copyright 2006 by Humana Press Inc. All rights of any nature whatsoever reserved.443412423Mukherjee, A.K., Maity, C.R., Biochemical composition, lethality and pathophysiology of venom from two cobras - Naja naja and N. kaouthia (2002) Comp. Biochem. Physiol. B. Biochem. Mol. Biol., 131, pp. 125-132Daltry, J.C., Wüster, W., Thorpe, R.S., Diet and snake venom evolution (1996) Nature, 379, pp. 537-540Saravia, P., Rojas, E., Arce, V., Geographic and ontogenic variability in the venom of the Neotropical rattlesnake Crotalus durissus: Pathophysiological and therapeutic implications (2002) Rev. Biol. 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Biol., 9, pp. 585-590Ogawa, T., Chijiwa, T., Oda-Ueda, N., Ohno, M., Molecular diversity and accelerated evolution of C-type lectin-like proteins from snake venom (2005) Toxicon, 45, pp. 1-14Prado-Franceschi, J., Brazil, O.V., Convulxin, a new toxin from the venom of the South American rattlesnake Crotalus durissus terrificus (1981) Toxicon, 19, pp. 875-887Murakami, M.T., Zela, S.P., Gava, L.M., Michelan-Duarte, S., Cintra, A.C., Arni, R.K., Crystal structure of the platelet activator convulxin, a disulfide-linked alpha4beta4 cyclic tetramer from the venom of Crotalus durissus terrificus (2003) Biochem. Biophys. Res. Commun., 310, pp. 478-482Batuwangala, T., Leduc, M., Gibbins, J.M., Bon, C., Jones, E.Y., Structure of the snake-venom toxin convulxin (2004) Acta Crystallogr., 60, p. 46Polgar, J., Clemetson, J.M., Kehrel, B.E., Platelet activation and signal transduction by convulxin, a C-type lectin from Crotalus durissus terrificus (tropical rattlesnake) venom via the p62/GPVI collagen receptor (1997) J. Biol. Chem., 272, pp. 13,576-13,583Hamako, J., Matsui, T., Suzuki, M., Purification and characterization of bitiscetin, a novel von Willebrand factor modulator protein from Bitis arietans snake venom (1996) Biochem. Biophys. Res. 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J., 378, pp. 399-407Furihata, K., Kato, K., Rádis-Baptista, G., Kunicki, T.J., Recombinant convulxin induces platelet aggregation (2003) Blood, 102, p. 2891Rottenberg, D., Bamberger, E.S., Kochva, E., Studies on ribonucleic acid synthesis in the venom glands of Vipera palaestinae (Ophidiae, Reptilia) (1971) Biochem. 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Differential effect of plant lectins on mast cells of different origins

Histamine release induced by plant lectins was studied with emphasis on the carbohydrate specificity, external calcium requirement, metal binding sites, and mast cell heterogeneity and on the importance of antibodies bound to the mast cell membrane to the lectin effect. Peritoneal mast cells were obtained by direct lavage of the rat peritoneal cavity and guinea pig intestine and hamster cheek pouch mast cells were obtained by dispersion with collagenase type IA. Histamine release was induced with concanavalin A (Con A), lectins from Canavalia brasiliensis, mannose-specific Cymbosema roseum, Maackia amurensis, Parkia platycephala, Triticum vulgaris (WGA), and demetallized Con A and C. brasiliensis, using 1-300 µg/ml lectin concentrations applied to Wistar rat peritoneal mast cells, peaking on 26.9, 21.0, 29.1, 24.9, 17.2, 10.7, 19.9, and 41.5%, respectively. This effect was inhibited in the absence of extracellular calcium. The lectins were also active on hamster cheek pouch mast cells (except demetallized Con A) and on Rowett nude rat (animal free of immunoglobulins) peritoneal mast cells (except for mannose-specific C. roseum, P. platycephala and WGA). No effect was observed in guinea pig intestine mast cells. Glucose-saturated Con A and C. brasiliensis also released histamine from Wistar rat peritoneal mast cells. These results suggest that histamine release induced by lectins is influenced by the heterogeneity of mast cells and depends on extracellular calcium. The results also suggest that this histamine release might occur by alternative mechanisms, because the usual mechanism of lectins is related to their binding properties to metals from which depend the binding to sugars, which would be their sites to bind to immunoglobulins. In the present study, we show that the histamine release by lectins was also induced by demetallized lectins and by sugar-saturated lectins (which would avoid their binding to other sugars). Additionally, the lectins also released histamine from Rowett nude mast cells that are free of immunoglobulins

Umbelliferone Induces Changes In The Structure And Pharmacological Activities Of Bn Iv, A Phospholipase A2 Isoform Isolated From Bothrops Neuwiedi

In this paper was demonstrated that umbelliferone induces changes in structure and pharmacological activities of Bn IV, a lysine 49 secretory phospholipase A2 (sPLA2) from Bothrops neuwiedi. Incubation of Bn IV with umbelliferone virtually abolished platelet aggregation, edema, and myotoxicity induced by native Bn IV. The amino acid sequence of Bn IV showed high sequence similarities with other Lys49 sPLA2s from B. jararacussu (BthTx-I), B. pirajai (PrTx-I), and B. neuwiedi pauloensis (Bn SP6 and Bn SP7). This sPLA2 also has a highly conserved C-terminal amino acid sequence, which has been shown as important for the pharmacological activities of Lys49 sPLA2. Sequencing of Bn IV previously treated with umbelliferone revealed modification of S(1) and S(20). Fluorescent spectral analysis and circular dichroism (CD) studies showed that umbelliferone modified the secondary structure of this protein. Moreover, the pharmacological activity of Bn IV is driven by synergism of the C-terminal region with the α-helix motifs, which are involved in substrate binding of the Asp49 and Lys49 residues of sPLA2 and have a direct effect on the Ca2+-independent membrane damage of some secretory snake venom PLA2. For Bn IV, these interactions are potentially important for triggering the pharmacological activity of this sPLA2. © 2011 Elsevier Ltd.576851860Chan, A.C., Pritchard, E.T., Gerrard, J.M., Man, R.Y., Choy, P.C., Biphasic modulation of platelet phospholipase A2 activity and platelet aggregation by mepacrine (quinacrine) (1982) Biochim. Biophys. 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Jararacussu (2008) Int. J. Mol. Sci., 9 (5), pp. 736-750Diz Filho, E.B., Marangoni, S., Toyama, D.O., Fagundes, F.H., Oliveira, S.C., Fonseca, F.V., Calgarotto, A.K., Toyama, M.H., Enzymatic and structural characterization of new PLA2 isoform isolated from white venom of Crotalus durissus ruruima (2009) Toxicon, 53 (1), pp. 104-114Fawzy, A.A., Vishwanath, B.S., Franson, R.C., Inhibition of human non-pancreatic phospholipases A2 by retinoids and flavonoids. 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