Uptake and translocation of brominated flame retardants in tomato plants (Solanum lycopersicum L.): Results from a standard soil-based biotest

The uptake and translocation of four polybrominated diphenyl ethers (PBDEs) and four novel brominated flame retardants (NBFRs) in tomato plants (Solanum lycopersicum L.) were investigated via the RHIZOtest, a standard soil-based biotest, optimized for organic compounds. Tomato plants were exposed to soil samples spiked with 0 (i.e. control), 5.00 or 50.00 ng g-1dw of each compound. Compared of those of the control, exposure to increasing spiking concentrations resulted in average reductions of 13% and 26% (w/w) in tomato plant biomass. Higher concentrations of NBFRs were analyzed both in roots, ranging from 0.23 to 8.01 ng g-1dw for PBDEs and from 1.25 to 18.51 ng g-1dw for NBFRs, and in shoots, ranging from 0.09 to 5.58 ng g-1dw and from 0.47 to 7.78 ng g-1dw for PBDEs and NBFRs, respectively. This corresponded to an average soil uptake of 5% for PBDEs and 9% for NBFRs at the lower soil-spiking level, and 3% for PBDEs and 6% for NBFRs at the higher soil spiking level. Consequently, among both initial spiking levels, the soil-root concentration factor (RCF) values were lower on average for PBDEs (0.13 ± 0.05 g dw soil g-1dw roots) than for NBFRs (0.33 ± 0.16 g dw soil g-1dw roots). Conversely, nondifferent values of the root-shoot transfer factor (TF) were calculated for both PBDEs (0.54 ± 0.13 g dw roots g-1dw shoots) and NBFRs (0.49 ± 0.24 g dw roots g-1dw shoots). The differences and similarities reported in the RCF and TF between and within the two groups of compounds can be explained by their properties. The calculated RCF and TF values of the PBDEs exhibited a decreasing trend as the number of bromine atoms increased. Additionally, a robust negative linear correlation was observed between RCF values and the respective logKow values for the PBDEs, at both soil-spiking levels. The root uptake of NBFRs exhibited a negative correlation with their hydrophobicity; however, this was not observed in the context of root-to-shoot transfer. The presence of a second aromatic ring appears to be the key factor influencing the observed variations in NBFRs, with biphenyl NBFRs (BTBPE and DBDPE) characterized by lower uptake and reduced translocation potential than monophenyl PBEB and HBB. Understanding the transfer of these compounds to crops, especially near plastic recycling waste sites, is crucial for understanding the risks of their potential inclusion in the human food chain.

Fully automated deep learning models with smartphone applicability for prediction of pain using the Feline Grimace Scale

This study used deep neural networks and machine learning models to predict facial landmark positions and pain scores using the Feline Grimace Scale© (FGS). A total of 3447 face images of cats were annotated with 37 landmarks. Convolutional neural networks (CNN) were trained and selected according to size, prediction time, predictive performance (normalized root mean squared error, NRMSE) and suitability for smartphone technology. Geometric descriptors (n = 35) were computed. XGBoost models were trained and selected according to predictive performance (accuracy; mean square error, MSE). For prediction of facial landmarks, the best CNN model had NRMSE of 16.76% (ShuffleNetV2). For prediction of FGS scores, the best XGBoost model had accuracy of 95.5% and MSE of 0.0096. Models showed excellent predictive performance and accuracy to discriminate painful and non-painful cats. This technology can now be used for the development of an automated, smartphone application for acute pain assessment in cats.

Vascular effects and electrolyte homeostasis of the natriuretic peptide isolated from Crotalus oreganus abyssus (North American Grand Canyon rattlesnake) venom

Crotalus oreganus abyssus is a rattlesnake that is usually found in the Grand Canyon, United States of America. Knowledge regarding the composition of C. o. abyssus venom is scarce. New natriuretic peptides (NPs) have been isolated and characterized from the venoms of members of the Crotalinae family. The NP family comprises three members, ANP (atrial natriuretic peptide), BNP (b-type natriuretic peptide) and CNP (c-type natriuretic peptide), and has an important role in blood pressure regulation and electrolyte homeostasis. The aim of the present study was to characterize a novel natriuretic-like peptide (Coa_NP2), isolated from C. o. abyssus venom. The Coa_NP2 presents an average molecular mass of 3419.88Da (theoretical average molecular mass 3418.94Da, monoisotopic molecular mass 3416.66Da and theoretical PI 7.78) and its amino acid sequence presents the loop region that is characteristic of natriuretic peptides. The peptide has 32 amino acids and its complete sequence is SYGISSGCFGLKLDRIGTMSGLGCWRLLQDSP. Coa_NP2 is a natriuretic peptide of the ANP/BNP-like family, since the carboxyterminal region of CNP has its own NP domain. We demonstrate, herein, that Coa_NP2 produces a dose-dependent decrease in mean arterial pressure in rats, followed by significant increases in concentrations of markers of nitric oxide formation measured in the plasma and vasorelaxation in a thoracic aortic ring bath. The structural and biological aspects confirm Coa_NP2 as a new natriuretic peptide, isolated from snake venom.

cDNA and deduced primary structure of basic phospholipase A2 with neurotoxic activity from the venom secretion of the Crotalus durissus collilineatus rattlesnake

To illustrate the construction of precursor complementary DNAs, we isolated mRNAs from whole venom samples. After reverse transcription polymerase chain reaction (RT-PCR), we amplified the cDNA coding for a neurotoxic protein, phospholipase A2 D49 (PLA2 D49), from the venom of Crotalus durissus collilineatus (Cdc PLA2). The cDNA encoding Cdc PLA2 from whole venom was sequenced. The deduced amino acid sequence of this cDNA has high overall sequence identity with the group II PLA2 protein family. Cdc PLA2 has 14 cysteine residues capable of forming seven disulfide bonds that characterize this group of PLA2 enzymes. Cdc PLA2 was isolated using conventional Sephadex G75 column chromatography and reverse-phase high performance liquid chromatography (RP-HPLC). The molecular mass was estimated using matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry. We tested the neuromuscular blocking activities on chick biventer cervicis neuromuscular tissue. Phylogenetic analysis of Cdc PLA2 showed the existence of two lines of N6-PLA2, denominated F24 and S24. Apparently, the sequences of the New World's N6-F24-PLA2 are similar to those of the agkistrodotoxin from the Asian genus Gloydius. The sequences of N6-S24-PLA2 are similar to the sequence of trimucrotoxin from the genus Protobothrops, found in the Old World.

High-throughput single-molecule fluorescence spectroscopy using parallel detection

Solution-based single-molecule fluorescence spectroscopy is a powerful new experimental approach with applications in all fields of natural sciences. The basic concept of this technique is to excite and collect light from a very small volume (typically femtoliter) and work in a concentration regime resulting in rare burst-like events corresponding to the transit of a single-molecule. Those events are accumulated over time to achieve proper statistical accuracy. Therefore the advantage of extreme sensitivity is somewhat counterbalanced by a very long acquisition time. One way to speed up data acquisition is parallelization. Here we will discuss a general approach to address this issue, using a multispot excitation and detection geometry that can accommodate different types of novel highly-parallel detector arrays. We will illustrate the potential of this approach with fluorescence correlation spectroscopy (FCS) and single-molecule fluorescence measurements obtained with different novel multipixel single-photon counting detectors.

Effect of umbelliferone (7-hydroxycoumarin, 7-HOC) on the enzymatic, edematogenic and necrotic activities of secretory phospholipase A2 (sPLA2) isolated from Crotalus durissus collilineatus venom

Flavonoids, coumarins and other polyphenolic compounds are powerful antioxidants both in hydrophilic and lipophylic environments with diverse pharmacological properties including anti-inflammatory activity. Despite being widely used as powerful therapeutic agents for blood coagulation disorders, more specifically to control some serine protease enzymes, the mechanism of anti-inflammatory activity of coumarins is unknown, unlike that of flavonoids. Although their controlling effect on serine proteases is well acknowledged, their action on secretory phospholipase A2 (sPLA2) remains obscure. The present study describes the interaction between umbelliferone (7-HOC) and the sPLA2 from Crotalus durissus collilineatus venom. In vitro inhibition of sPLA2 enzymatic activity by 7-HOC was estimated using 4N3OBA as substrate, resulting in an irreversible decrease in such activity proportional to 7-HOC concentration. The biophysical interaction between 7-HOC and sPLA2 was examined by fluorescent spectral analysis and circular dichroism studies. Results from both techniques clearly showed that 7-HOC strongly modified the secondary structure of this enzyme and CD spectra revealed that it strongly decreased sPLA2 alpha-helical conformation. In addition, two-dimensional electrophoresis indicated an evident difference between HPLC-purified native and 7-HOC-treated sPLA2s, which were used in pharmacological experiments to compare their biological activities. In vivo anti-inflammatory activity was assessed by the sPLA2-induced mouse paw edema model, in which 7-HOC presented an effect similar to those of dexamethasone and cyproheptadine against the pro-inflammatory effect induced by native sPLA2 on the mouse paw edema, mast cell degranulation and skin edema. On the other hand, 7-HOC exhibited a more potent inhibitory effect on sPLA2 than that of p-bromophenacyl bromide (p-BPB). Our data suggest that 7-HOC interacts with sPLA2 and causes some structural modifications that lead to a sharp decrease or inhibition of the edematogenic and myotoxic activities of this enzyme, indicating its potential use to suppress inflammation induced by sPLA2 from the snake venom.

Neuromuscular activity of BaTX, a presynaptic basic PLA2 isolated from Bothrops alternatus snake venom

We have previously isolated a Lys49 phospholipase A(2) homolog (BaTX) from Bothrops alternatus snake venom using a combination of molecular exclusion chromatography and reverse phase HPLC and shown its ability to cause neuromuscular blockade. In this work, we describe a one-step procedure for the purification of this toxin and provide further details of its neuromuscular activity. The toxin was purified by reverse phase HPLC and its purity and molecular mass were confirmed by SDS-PAGE, MALDI-TOF mass spectrometry, amino acid analysis and N-terminal sequencing. BaTX (0.007-1.4 microM) produced time-dependent, irreversible neuromuscular blockade in isolated mouse phrenic nerve-diaphragm and chick biventer cervicis preparations (time to 50% blockade with 0.35 microM toxin: 58+/-4 and 24+/-1 min, respectively; n=3-8; mean+/-S.E.) without significantly affecting the response to direct muscle stimulation. In chick preparations, contractures to exogenous acetylcholine (55 and 110 microM) or KCl (13.4 mM) were unaltered after complete blockade by all toxin concentrations. These results, which strongly suggested a presynaptic mechanism of action for this toxin, were reinforced by (1) the inability of BaTX to interfere with the carbachol-induced depolarization of the resting membrane, (2) a significant decrease in the frequency and amplitude of miniature end-plate potentials, and (3) a significant reduction (59+/-4%, n=12) in the quantal content of the end-plate potentials after a 60 min incubation with the toxin (1.4 microM). In addition, a decrease in the organ bath temperature from 37 degrees C to 24 degrees C and/or the replacement of calcium with strontium prevented the neuromuscular blockade, indicating a temperature-dependent effect possibly mediated by enzymatic activity.

Molecular modeling and inhibition of phospholipase A2 by polyhydroxy phenolic compounds

Phospholipases A(2) are enzymes responsible for the hydrolysis of membrane phospholipids that release arachidonic acid, which serves as substrate for pro-inflammatory mediators, such as prostaglandins and leucotriens. The design of specific inhibitors for PLA(2) might help in the development of new anti-inflammatory drugs. Polyhydroxy phenolic compounds, such as flavonoids, vitamin E, rosmarinic acid and aristolochic acid, are able to inhibit PLA(2) from different sources. Herein, we have studied the kinetic behavior and the capacity of inhibiting edema formation induced by PLA(2) of five different polyhydroxy phenolic compounds (two phenolic derivatives and three acetophenone hydroxylated derivatives) extracted from the venom of Crotalus adamanteus. The results showed that compounds 1,3-dihydroxy benzene, 1,3,5-trihydroxy benzene and 2,4,6-trihydroxy acetophenone were the most efficient in the inhibition of the enzymatic activity and edema induction by PLA(2). It was also verified that the number of hydroxyls in each molecule is not a limiting factor for the inhibition capacity of these compounds. Molecular modeling studies indicated that the most active compounds are linked to the amino acid Asp 49 and that they destabilize the coordination of the calcium atom, which is essential to the catalytic activity. The study of potential surfaces showed that there are conditions in which the potential values must be adequate for enzyme complex formation with polyhydroxy phenolic compounds. When the potential over the hydroxyl surfaces is very high, formation of stable complexes does not occur and the enzyme does not act intensely. These results might be helpful in the design of a drug that specifically inhibits PLA(2).

Isolation and characterization of a serine protease, Ba III-4, from Peruvian Bothrops atrox venom

A serine protease from Bothrops atrox (Peruvian specimen's venom) was isolated in two chromatographic steps in LC molecular exclusion and reverse phase-HPLC. This protein was denominated Ba III-4 (33,080.265 Da determinated by MALDI-TOF mass spectrometry) and showed pI of 5.06, Km 0.2 x 10(-1 ) M and the V (máx) 4.1 x 10(-1 )nmoles p-NA/lt/min on the synthetic substrate BapNA. Ba III-4 also showed ability to coagulate bovine fibrinogen. The serine protease was inhibited by soyben trypsin inhibitor and DA2II, which is an anti-hemorrhagic factor isolated from the opossum specie Didelphis albiventris. The primary structure of Ba III-4 showed the presence of His(44), Asp(94) and Ser(193) residues in the corresponding positions to the catalytic triad established in the serine proteases and Ser(193) are inhibited by phenylmethylsulfonylfluoride (PMSF). Amino acid analysis showed a high content of Asp, Glu, Gly, Ser, Ala and Pro, as well as 12 half-cysteine residues. Ba III-4 contained 293 amino acid residues and the primary structure of VIGGDECDIN EHPFLAFMYY SPRYFCGMTL INQEWVLTAA HCRYFCGMTL IHLGVHRESE KANYDEVRRF PKEKYFIFCD NNFTDDEVDK DIMLIRLDKP VSNSEHIAPL SLPSNPPSVG SVCRIMGWGQ TTTSPIDVLS PDEPHCANIN LFDNTVCHTA HPQVANTRTS TDTLCAGDLQ GGRDTCNGDS GGPLICNEQL HGILSWGGDP CAQPNKPAFY TKVYYFDHPW IKSIIAGNKK TVNFTCPPLR SDAKDDSTTY INQEWDWVLT AEHCDRTHMR NSFYDYSSIN SDS. Titration experiments did not show the presence of free sulfhydryl groups after 4 h incubation, nor were differences found in relation to titration kinetics in the presence of nondenaturating buffer. The isolation of this protein, Ba III-4, is of potential interest for the understanding of the pathomechanism of the snake venom action and for the identification of new blood coagulation enzymes of natural sources.

Crystallization and preliminary X-ray crystallographic analysis of the heterodimeric crotoxin complex and the isolated subunits crotapotin and phospholipase A2

Crotoxin, a potent neurotoxin from the venom of the South American rattlesnake Crotalus durissus terrificus, exists as a heterodimer formed between a phospholipase A(2) and a catalytically inactive acidic phospholipase A(2) analogue (crotapotin). Large single crystals of the crotoxin complex and of the isolated subunits have been obtained. The crotoxin complex crystal belongs to the orthorhombic space group P2(1)2(1)2, with unit-cell parameters a = 38.2, b = 68.7, c = 84.2 A, and diffracted to 1.75 A resolution. The crystal of the phospholipase A(2) domain belongs to the hexagonal space group P6(1)22 (or its enantiomorph P6(5)22), with unit-cell parameters a = b = 38.7, c = 286.7 A, and diffracted to 2.6 A resolution. The crotapotin crystal diffracted to 2.3 A resolution; however, the highly diffuse diffraction pattern did not permit unambiguous assignment of the unit-cell parameters.

Structural and Functional Properties of Cr 5, a New Lys49 Phospholipase A2 Homologue Isolated from the Venom of the Snake Calloselasma rhodostoma

Cr 5 PLA(2) homologous (K49) was isolated from Calloselasma rhodostoma venom in only one chromatographic step in reverse phase HPLC (RP-HPLC) (on mu-Bondapack C-18). A molecular mass of 13.965 Da was determined by MALDI-TOF mass spectrometry. The amino acid composition showed that Cr 5 had a high content of Lys, Tyr, Gly, Pro, and 14 half-Cys residues, typical residues of a basic PLA(2). The complete amino acid sequence of Cr 5 PLA(2) contains 120 residues, resulting in a calculated pI value of 5.55. This sequence shows high identity values when compared to other K49 PLA(2)s isolated from the venoms of viperid snakes. Lower identity is observed in comparison to D49 PLA(2)s. The sequence found was SLVELGKMIL QETGKNPAKS YGAYGCNCGV LGRHKPKDAT DRCCFVHKCC YKKLTGCDPK KDRYSYSWKD KTIVCGENNP CLKEMCECDK AVAICLRENL DTYNKKYRYL KPFCKKADDC. In mice, Cr 5 induced myonecrosis and edema upon intramuscular and intravenous injections, respectively. The LD(50) of Cr 5 was 0.070 mg/kg of the animal weight, by intracerebroventricular (i.c.v.) route. In vitro, the toxin caused rapid cytolytic effect upon mouse skeletal muscle myoblasts in culture. The isolation of this PLA(2) and the combined structural and functional information obtained classify Cr 5 as a new member of the K49 PLA(2) family, since it presents typical features from such proteins.

Characterization of a New Platelet Aggregating Factor from Crotoxin Crotalus durissus cascavella Venom

In this article we investigated the platelet aggregating activity of whole crotoxin and its subunits isolated from Crotalus durissus cascavella venom. During the purification protocols of the venom, using HPLC molecular exclusion, we detected the presence of two different serine protease activities in the gyroxin fraction, and another in the crotoxin fraction, which induced strong and irreversible platelet aggregation, in addition to blood coagulation. From crotoxin, we isolated PLA2, crotapotin (both fractions corresponding approximately 85% of whole crotoxin) and another minor fraction (F20) that exhibited serine protease activity. After a new fractionation on reverse phase HPLC chromatography, we obtained three other fractions named as F201, F202 and F203. F202 was obtained with high degree of molecular homogeneity with molecular mass of approximately 28 kDa and a high content of acidic amino residues, such as aspartic acid and glutamic acid. Other important amino acids were histidine, cysteine and lysine. This protein exhibited a high specificity for BApNA, a Michaelis-Menten behavior with Vmax estimated in 5.64 microM/min and a Km value of 0.58 mM for this substrate. In this work, we investigated the ability of F202 to degrade fibrinogen and observed alpha and beta chain cleavage. Enzymatic as well as the platelet aggregation activities were strongly inhibited when incubated with TLCK and PMSF, specific inhibitors of serine protease. Also, F202 induced platelet aggregation in washed and platelet-rich plasma, and in both cases, TLCK inhibited its activity. The N-terminal amino acid sequence of F202 presented a high amino acid sequence homology with other thrombin-like proteins, but it was significantly different from gyroxin. These results showed that crotoxin is a highly heterogeneous protein composed of PLA2, thrombin-like and other fractions that might explain the diversity of physiological and pharmacological activities of this protein.

Determination of Primary Structure of Two Isoforms 6-1 and 6-2 PLA2 D49 from Bothrops jararacussu Snake Venom and Neurotoxic Characterization Using in vitro Neuromuscular Preparation

In this paper we reported the purification, the biological characterization and the amino acid sequence of two new isoforms basic 6-1 (Bj-IV) and 6-2 (Bj-V) PLA(2) D49 purified from the Bothrops jararacussu venom. The isoforms 6-1 and 6-2 had a sequence of amino acids of 121 amino acid residues 6-1: DLFEWGQMIL KETGKNPFPY YGAYGCYCGW GGRGKPKDKD TDRCCYVHDC CYKKLTGCPK TDDRYSYSWL DLTIVCGEDD PCKELCECDK AIAVCFRENL GTYNKKYRYH LKPCKKADKP C and pI value 7.83 and 6-2: DLWQFGQMIL KETGKIPFPY YGAYGCYCGW GGRGGKPKDG TDRCCYVHDC CYKKLTGCPK TDDRYSYSWL DLTIVCGEDD PCKELCECDK AIAVCFRENL GTYNKKYRYH LKPCKKADKP C with a pI value of 7.99. Skeletal muscle preparations from the young chicken have been used previously in order to study the effects of toxins on neuromuscular transmission, providing an important opportunity to study the differentiated behavior of a toxin before more than one model, because it shows differences in its sensibilities. Both isoforms have produced neuromuscular blockade in young chicken biventer cervicis nerve-muscle preparations in presence or absence of crotapotin crotalic (F3 and F4) indicating that catalytic activity was not essential for neuromuscular action in this preparation.

A new method to purify hepatic CYP1A of Prochilodus scrofa, a Brazilian freshwater fish

Cytochromes P450 constitute a superfamily of the phase I enzymes whose primary task is the detoxification of both endogenous and xenobiotic compounds. Fish, among non-mammalian species, have received great interest because they are a direct food source for humans as well as conveyors of toxic chemicals to human beings. The aim of the present study was the purification of the hepatic isoform of CYP1A in Prochilodus scrofa (Prochilodontidae), a Brazilian fish, using only one chromatographic step. The purification of CYP1A was done by Reverse Phase HPLC on a C18 column. Purified CYP1A was characterized with respect to electrophoretic, immunochemical and biocatalyst properties. CYP1A fractions produced a single uniform band on SDS-PAGE with an apparent molecular mass of 58 kDa. Purified CYP1A of P. scrofa showed strong cross-reactivity with antibodies directed against CYP1A from trout. The fraction was also encapsulated in two different reconstituted systems; one composed of neutral lipids and another of negatively charged lipids. In both of them, we could detect EROD activity but not PROD activity, which confirms that the CYP1A was purified with all its enzyme activity. There was an increase of activity when CYP1A and NADPH cytochrome P450 (CYP) reductase were encapsulated in negatively charged lipids, which confirms that the charge of lipid is essential to CYP1A activity. All these characteristics strongly suggest that this new procedure is efficient for purifying hepatic CYP1A from P. scrofa, showing that the CYP1A isoform of this fish has a highly conserved protein region.

Neurotoxic and myotoxic actions of crotoxin-like and Crotalus durissus cascavella whole venom in the chick biventer cervicis preparation

Crotoxin from Crotalus durissus cascavella venom was purified by a combination of molecular exclusion chromatography (Superdex 75 column) and HPLC molecular exclusion (Protein Pack 300SW column). Neurotoxic and myotoxic effects from C. durissus cascavella whole venom and its main fraction, the crotoxin-like, were studied in the chick biventer cervicis (CBC) nerve-muscle preparation. Both venom and its crotoxin showed significant (p < 0.05) blockade of neuromuscular transmission at concentrations as low as 0.2-1, 5 and 25 microg/ml, but no significant effect has been shown with a concentration of 0.04 microg/ml (n = 5 each). The time required to produce 50% neuromuscular blockade with the venom and its crotoxin was 53.6+/-8.2 and 65.9+/-4.9 min (0.2 microg/ml), 29.7+/-1.9 and 34.3+/-1.9 min (1 microg/ml), 24.8+/-1.6 and 21.1+/-1.5 min (5 microg/ml), 20.9+/-3.7 and 20.1+/-1.4 min (25 microg/ml), respectively. The addition to the incubation bath of acetylcholine (55 and 110 microM) or KCl (20.1 mM), either before or after the venom or the crotoxin induced contracture in the presence of a total blockade, in all the concentrations used. Morphological analysis showed that the damage caused by C. durissus cascavella venom is stronger than that caused by crotoxin. The myonecrotic picture was more marked at higher venom and crotoxin doses (1, 5 or 25 microg/ml). Only at 25 microg/ml concentrations of the venom and crotoxin, marked muscle fiber changes were detected. We concluded that the crotoxin-like and the whole venom from C. durissus cascavella possess a preponderant and quite potent neurotoxic action in this preparation, and a myotoxic action which is observed only at higher doses.

Isolation and characterization of a lectin from Annona muricata seeds

A lectin with a high affinity for glucose/mannose was isolated from Annona muricata seeds (Annonaceae) by gel filtration chromatography on Sephacryl S-200, ion exchange chromatography on a DEAE SP-5 PW column, and molecular exclusion on a Protein Pak Glass 300 SW column. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (PAGE) yielded two protein bands of approximately 14 kDa and 22 kDa. However, only one band was seen in native PAGE. The Mr of the lectin estimated by fast-performance liquid chromatography-gel filtration on Superdex 75 was 22 kDa. The lectin was a glycoprotein with 8% carbohydrate (neutral sugar) and required divalent metal cations (Ca2+, Mg2+, and Mn2+) for full activity. Amino acid analysis revealed a large content of Glx, Gly, Phe, and Lys. The lectin agglutinated dog, chicken, horse, goose, and human erythrocytes and inhibited the growth of the fungi Fusarium oxysporum, Fusarium solani, and Colletotrichum musae.

Inflammatory responses induced in mice by lectin from Talisia esculenta seeds

A novel lectin from Talisia esculenta seeds (TEL) has recently been purified and characterized. In this study we investigated the proinflammatory activity of TEL in mice using both the air-pouch and peritoneal cavity as well as paw oedema models. TEL (10-40 microg) induced significant neutrophil and mononuclear cell recruitment when injected into either mouse air-pouch or peritoneal cavity. The neutrophil accumulation into the air-pouch was dose- and time-dependent with a maximal response at 16 h, returning to control levels at 72 h whereas maximal mononuclear cell accumulation was observed at 24 h after TEL injection. The same profile of neutrophil accumulation was observed when this lectin was injected into mouse peritoneal cavity, although the maximal mononuclear cell recruitment was observed 48 h after TEL injection. Additionally, TEL (12.5-200 microg/paw) caused a dose-dependent mice paw, as evaluated at 4 h after the lectin injection. D-mannose, better than D-glucose, significantly inhibited TEL-induced neutrophil migration into the peritoneal cavity or air-pouch. D-galactose had no effect on TEL-induced neutrophil migration in either cavity studied. On the other hand, D-mannose slightly inhibited the TEL-induced paw oedema, whereas neither D-glucose nor D-galactose affected this phenomenon. In conclusion, our data show that TEL induces neutrophil and mononuclear cell accumulation by a mechanism related to their specific sugar-binding properties.

The pharmacological effect of Bothrops neuwiedii pauloensis (jararaca-pintada) snake venom on avian neuromuscular transmission

The neuromuscular effects of Bothrops neuwiedii pauloensis (jararaca-pintada) venom were studied on isolated chick biventer cervicis nerve-muscle preparations. Venom concentrations of 5-50 micro g/ml produced an initial inhibition and a secondary increase of indirectly evoked twitches followed by a progressive concentration-dependent and irreversible neuromuscular blockade. At venom concentrations of 1-20 micro g/ml, the responses to 13.4 mM KCl were inhibited whereas those to 110 micro M acetylcholine alone and cumulative concentrations of 1 micro M to 10 mM were unaffected. At venom concentrations higher than 50 micro g/ml, there was pronounced muscle contracture with inhibition of the responses to acetylcholine, KCl and direct stimulation. At 20-24 degrees C, the venom (50 g/ml) produced only partial neuromuscular blockade (30.7 +/- 8.0%, N = 3) after 120 min and the initial inhibition and the secondary increase of the twitch responses caused by the venom were prolonged and pronounced and the response to KCl was unchanged. These results indicate that B.n. pauloensis venom is neurotoxic, acting primarily at presynaptic sites, and that enzyme activity may be involved in this pharmacological action.

Renal toxicity of Bothrops moojeni snake venom and its main myotoxins

Acute renal failure is one the most common systemic complications after snakebite, however, its pathogenesis remains obscure. In this study we evaluated the renal effects of Bothrops moojeni venom and its myotoxins (Bmtx-I and BmtxII) in rat isolated perfused kidneys. The myotoxins were purified by ion-exchange chromatography and reverse phase HPLC. The whole venom (10 microg/ml) and myotoxins (5 microg/ml) were added to the perfusion system 30 min after the beginning of each perfusion. The renal effects were compared to a control group perfused with modified Krebs-Henseleit solution alone. B. moojeni venom decreased the perfusion pressure (PP), renal vascular resistance (RVR), and the percent sodium, potassium and chloride tubular transport (%TNa(+), %TK(+), %TCl(-)). In contrast, the venom increased the urinary flow (UF), glomerular filtration rate (GFR), and the sodium, potassium and chloride excretion (ENa(+), EK(+), ECl(-)). The renal effects of myotoxin I was very similar to those of the whole venom, but there was an increase rather than a decrease in the PP and RVR. Myotoxin II had no effect on renal physiology, except for a transient decrease in %TK(+). In conclusion, B. moojeni venom caused intense alterations in renal physiology, including a drop in vascular resistance associated with diuresis, natriuresis and kaliuresis. Bmtx-I had an opposite effect when compared to whole venom, showed in the parameters of PP and RVR. Bmtx-II had a mild effect in %TK(+). The apparent inability of Bmtx-II to induce the renal effect similarly to Bmtx-I should be explained by the absence in the Bmtx-II of the C-terminal lysine rich region.

Biochemical characterization of a lectin from Delonix regia seeds

A lectin from Delonix regia (DRL) seeds was purified by gel filtration on Sephadex G-100 followed by ion-exchange chromatography on diethylaminoethyl-Sepharose and reverse-phase high-performance liquid chromatography on a C18 column. Hemagglutinating activity was monitored using rat erythrocytes. DRL showed no specificity for human erythrocytes of ABO blood groups. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed a single protein in the presence of 0.1 M of dithiothreitol (DTT) and in nonreducing conditions. Native-PAGE showed that DRL is a monomer with a molecular mass of about 12 kDa, as determined by denaturing gel electrophoresis and gel filtration chromatography. An amino acid composition revealed the absence of cysteine residues, the presence of 1 mol methionine/mol protein and a high proportion of acidic amino acids and glycine. The N-terminal sequence of DRL was determined by Edman degradation, and up to 16 amino acid residues showed more than 90% homology with other lectins from the Leguminosae family. The optimal pH range for lectin activity was between pH 8.0 and 9.0, and the lectin was active up to 60 degrees C. The lectin required Mn2+ for hemagglutinating activity and remained active after reduction with 0.1 M of DTT, but lost activity in the presence of 8 M of urea. Sodium metaperiodate had no effect on the activity of DRL.

Isolation and preliminary enzymatic characterization of a novel PLA2 from Crotalus durissus collilineatus venom

A crotoxin homolog was purified from the Crotalus durissus collilineatus venom using molecular exclusion and reverse-phase HPLC. This crotoxin contained one PLA2 (Cdcolli III F6) and four crotapotin isoforms, whereas crotoxin from Crotalus durissus terrificus venom had three PLA2 iso forms and two crotapotin isoforms. SDS-PAGE showed that the C. d. collilineatus PLA2 and crotapotin had relative molecular mass of 15 and 9 kDa, respectively. Neither the PLA2 (Cdcolli III F6) nor the crotapotins (Cdcolli III F3 and F4) had any neurotoxicity in mouse phrenic nerve-diaphragm preparations when tested alone. However, when PLA2 and crotapotin were coincubated before testing, the neurotoxicity was restored to a level similar to test in the venom in native crotoxin. The two crotapotins (Cdcolli III F3 and F4) differed in their ability to inhibit PLA2 activity, perhaps because of variations in their affinities for this enzyme. Cdcolli III F6 showed allosteric enzymatic behavior, with maximal activity at pH 8.3 and 36 degrees C. Full PLA2 activity required the presence of a low Ca2+ concentration and was inhibited by Cu2+ and Zn2+ and by Cu2+ and Mg2+ in the presence and absence of Ca2+, respectively. These results indicate that crotoxin from C. d. collineatus venom is very similar enzymatically to crotoxin from C. d. terrificus.

Structural and functional characterization of basic PLA2 isolated from Crotalus durissus terrificus venom

The venom of Crotalus durissus terrificus was fractionated by reverse-phase HPLC to obtain crotapotins (F5 and F7) and PLA2 (F15, F16, and F17) of high purity. The phospholipases A2 (PLA2S) and crotapotins showed antimicrobial activity against Xanthomonas axonopodis pv. passiflorae, although the unseparated crotoxin did not. The F17 of the PLA2 also revealed significant anticoagulant activity, althrough for this to occur the presence of Glu 53 and Trp 61 is important. The F17 of the PLA2 showed allosteric behavior in the presence of a synthetic substrate. The amino acid sequence of this PLA2 isoform, determined by automatic sequencing, was HLLQFNKMLKFETRK NAVPFYAFGCYCGWGGQRRPKDATDRCCFVHDCCYEKVTKCNTKWDFYRYSLKSGY ITCGKGTWCKEQICECDRVAAECLRRSLSTYKNEYMFYPDSRCREPSETC. Analysis showed that the sequence of this PLA2 isoform differed slightly from the amino acid sequence of the basic crotoxin subunit reported in the literature. The homology with other crotalid PLA2 cited in the literature varied from 60% to 90%. The pL was estimated to be 8.15, and the calculated molecular weight was 14664.14 as determined by Tricine SDS-PAGE, two-dimensional electrophoresis, and MALDI-TOFF. These results also suggested that the enzymatic activity plays an important role in the bactericidal effect of the F17 PLA2 as well as that of anticoagulation, although other regions of the molecule may also be involved in this biological activity.

Purification and characterization of a new trypsin inhibitor from Dimorphandra mollis seeds

A second trypsin inhibitor (DMTI-II) was purified from the seed of Dimorphandra mollis (Leguminosae-Mimosoideae) by ammonium sulfate precipitation (30-60%), gel filtration, and ion-exchange and affinity chromatography. A molecular weight of 23 kDa was estimated by gel filtration on a Superdex 75 column SDS-PAGE under reduced conditions showed that DMTI-II consisted of a single polypeptide chain, although isoelectric focusing revealed the presence of three isoforms. The dissociation constant of 1.7 x 10(-9) M with bovine trypsin indicated a high affinity between the inhibitor and this enzyme. The inhibitory activity was stable over a wide pH range and in the presence of DTT. The N-terminal sequence of DMTI-II showed a high degree of homology with other Kunitz-type inhibitors.

Isolation and characterization of a convulxin-like protein from Crotalus durissus collilineatus venom

A convulxin (Cvx)-like protein was isolated from Crotalus durissus collilineatus venom by a combination of molecular exclusion and reversed-phase HPLC chromatographies. The molecular mass of the Cvx-like protein in the absence and presence of DTT was 78 kDa and 12-13 kDa, respectively. The Cvx-like protein consisted of two nonidentical polypeptide chains (alpha and beta). The N-terminal amino-acid sequences of the alpha and beta subunits were GLHCPSDWYAYDGHCYKIFNEEMNWED and GFCCPSHWSSYSRYCYKFFSQEMNWEDAEK, respectively, with both subunits having a high content of Glu, Ser, Cys, and Asp. The Cvx-like protein showed high homology with other venom C-type lectins, but had low hemagglutinating activity on intact and trypsinized erythrocytes. The Cvx-like protein stimulated insulin receptor phosphorylation and potentiated insulin secretion from isolated islets in the presence of sub- (2.8 mM) or supra-physiological (16.7 mM) glucose concentrations. These results suggest that the increase in insulin secretion induced by Cvx-like protein may be mediated by a protein tyrosine kinase-dependent pathway and may involve other membrane receptors, such as GP VI or Scr family proteins.

Crystallization and preliminary X-ray diffraction analysis of a novel trypsin inhibitor from seeds of Copaifera langsdorffii

A novel trypsin inhibitor isolated from seeds of Copaifera langsdorffii was purified to homogeneity and crystallized. Crystals suitable for X-ray analysis were grown using the hanging-drop vapour-diffusion method at 291 K in sodium acetate buffer at pH values near 4.3 using PEG 4000 as precipitant. The crystals presented symmetry compatible with the space group P4(1)2(1)2 or P4(3)2(1)2, with unit-cell parameters a = b = 58.71, c = 93.75 A, and diffracted to 1.83 A resolution at the synchrotron source.

Isolation and characterization of isolectins from Talisia esculenta seeds

Four isolectins (TEL-I, TEL-II, TEL-III and TEL-IV) were isolated from seeds of Talisia esculenta by reverse-phase high-performance liquid chromatography. RP-HPLC was performed on a u-Bondapack C18 column (0.78 cm x 30 cm) (Waters 991-PDA system) at room temperature. Rechromatography of the four fractions on a C18 column under the same conditions yielded lectins with two dissimilar subunits (Mr 20 kDa and 40 kDa) bound noncovalently. The isolectins showed very similar characteristics, such as molecular masses, N-terminal sequences, and hemagglutinating activity, but differed in their isoelectric points and in inhibition by carbohydrates.

Primary sequence determination of a Kunitz inhibitor isolated from Delonix regia seeds

A serine proteinase inhibitor was purified from Delonix regia seeds a Leguminosae tree of the Caesalpinioideae subfamily. The inhibitor named DrTI, inactivated trypsin and human plasma kallikrein with K(i )values 2.19x10(-8) M and 5.25 nM, respectively. Its analysis by SDS-PAGE 10-20% showed that the inhibitor is a protein with a single polypeptide chain of M(r) 22 h Da. The primary sequence of the inhibitor was determined by Edman degradation, thus indicating that it contained 185 amino acids and showed that it belongs to the Kunitz type family; however, its reactive site did not contain Arg or Lys at the putative reactive site (position 63, SbTI numbering) or it was displaced when compared to other Kunitz-type inhibitors.

Isolation and enzymatic characterization of a basic phospholipase A2 from Bothrops jararacussu snake venom

A novel basic phospholipase A2 (PLA2) isoform was isolated from Bothrops jararacussu snake venom and partially characterized. The venom was fractionated by HPLC ion-exchange chromatography in ammonium bicarbonate buffer, followed by reverse-phase HPLC to yield the protein Bj IV. Tricine SDS-PAGE in the presence or absence of dithiothreitol showed that Bj IV had a molecular mass of 15 and 30 kDa, respectively. This enzyme was able to form multimeric complexes (30, 45, and 60 kDa). Amino acid analysis showed a high content of hydrophobic and basic amino acids as well as 14 half-cysteine residues. The N-terminal sequence (DLWSWGQMIQETGLLPSYTTY...) showed a high degree of homology with basic D49 PLA2 myotoxins from other Bothrops venoms. Bj IV had high PLA2 activity and produced moderate myonecrosis in skeletal muscle, but showed no neuromuscular activity in mouse phrenic nerve-diaphragm preparations. Bj IV showed allosteric enzymatic behavior, with maximal activity at pH 8.2 and 35-45 degrees C. Full PLA2 activity required Ca2+ but was inhibited by Cu2+ and Zn2+, and by Cu2+ and Mg2+ in the presence and absence of Ca2+, respectively. Crotapotins from Crotalus durissus terrificus rattlesnake venom significantly inhibited the enzymatic activity of Bj IV. The latter observation suggested that the binding site for crotapotin in this PLA2 was similar to that in the basic PLA2 of the crotoxin complex from C. d. terrificus venom. The presence of crotapotin-like proteins capable of inhibiting the catalytic activity of D49 PLA2 could partly explain the low PLA2 activity of Bothrops venoms.

Structural basis for low catalytic activity in Lys49 phospholipases A2--a hypothesis: the crystal structure of piratoxin II complexed to fatty acid

Asp49 plays a fundamental role in supporting catalysis by phospholipases A2 by coordinating the calcium ion which aids in the stabilization of the tetrahedral intermediate. In several myotoxins from the venoms of Viperidae snakes, this aspartic acid is substituted by lysine. The loss of calcium binding capacity by these mutants has become regarded as the standard explanation for their greatly reduced or nonexistent phospholipolytic activity. Here we describe the crystal structure of one such Lys49 PLA2, piratoxin-II, in which a fatty acid molecule is observed within the substrate channel. This suggests that such toxins may be active enzymes in which catalysis is interrupted at the stage of substrate release. Comparison of the present structure with other PLA2s, both active and inactive, identifies Lys122 as one of the likely causes of the increased affinity for fatty acid in Lys49 enzymes. Its interaction with the mainchain carbonyl of Cys29 is expected to lead to hyperpolarization of the peptide bond between residues 29 and 30 leading to an increased affinity for the fatty acid headgroup. This strongly bound fatty acid may serve as an anchor to secure the toxin within the membrane thus facilitating its pathological effects.

Biochemical characterization and N-terminal sequences of two new trypsin inhibitors from Copaifera langsdorffii seeds

Two new trypsin inhibitors, TDI-I and TDI-II, were purified from the seeds of the native Brazilian tree Copaifera langsdorffii (Caesalpinoideae, Leguminosae). The purification procedure involved ammonium sulfate fractionation, ion-exchange chromatography on DEAE-Sepharose, affinity chromatography on trypsin-Sepharose, and reversed-phase (RP) HPLC. RP-HPLC yielded two forms (TDI-I and TDI-II), as confirmed by isoelectric focusing, with pI values between 7.0 and 8.1. The molecular mass of the TDI forms was 24 kDa based on FPLC gel filtration on Superdex 75. Under reducing conditions in tricine SDS-PAGE the molecular masses of TDI-I and TDI-II were 12 and 10 kDa, respectively. The Ki values were 1.1 and 1.2 nM for TDI-I and TDI-II, respectively, and there was no inhibitory effect on chymotrypsin. Amino acid analysis revealed high levels of aspartic acid, glutamic acid, serine, glycine, proline, and lysine but low levels of methionine and aromatic amino acids in both inhibitors; the calculated molecular masses were 11,456 and 10,008 for TDI-I and II, respectively. Based on the N-terminal sequences of TDI-I and TDI-II, TDI-I belongs to the Kunitz family of trypsin inhibitors, whereas TDI-II showed no homology to any other protein. This observation suggests that TDI-II belongs to a new inhibitor subclass of low-molecular mass proteins in the subfamily Caesalpinoideae.

Leucocyte recruitment induced by type II phospholipases A(2) into the rat pleural cavity

Bothropstoxin-I (BthTX-I) and bothropstoxin-II (BthTX-II) are Lys-49 and Asp-49 phospholipases A(2) (PLA(2)s), respectively, isolated from Bothrops jararacussu venom. Piratoxin-I (PrTX-I) is a Lys-49 PLA(2) isolated from Bothrops pirajai venom. In this study, the ability of BthTX-I, BthTX-II and PrTX-I to recruit leucocytes into the rat pleural cavity and potential mechanisms underlying this effect were investigated. Intrapleural injection of either BthTX-I or PrTX-I (10-100 microg/cavity each) caused a significant leucocyte infiltration at 12 h after injection. The maximal cell migration was observed with the dose of 30 microg/cavity (14.9+/-15.5 and 17.6+/-1. 6x10(6) cells/cavity, respectively). Leucocyte counts consisted mainly of mononuclear cells, but significant amounts of neutrophils and eosinophils were also observed. Intrapleural injection of BthTX-II (10-100 microg/cavity) caused a marked leucocyte infiltration at 6 and 12 h after injection. The maximal response was observed with the dose of 100 microg/cavity (57.3+/-3.4x10(6) cells/cavity, 6 h). The leucocyte counts were mainly composed of neutrophils and mononuclear cells. The treatment of either BthTX-I (30 microg/cavity, 12 h) or BthTX-II (30 microg/cavity, 6 h) with the PLA(2) inhibitor p-bromophenacyl bromide (p-BPB) had no effect on the total and differential leucocyte counts induced by these proteins. The same treatment partially reduced the PrTX-I-induced pleural leucocyte infiltration. In rats depleted of the histamine and 5-hydroxytryptamine (5-HT) stores by chronic treatment with compound 48/80, the total leucocyte counts in response to BthTX-I, BthTX-II and PrTX-I was not significantly affected compared to control animals. In addition, BthTX-I, BthTX-II and PrTX-I (100 microg/ml each) significantly degranulated pleural mast cells in vitro leading to the release of [(14)C]5-hydroxytryptamine ([(14)C]5-HT). p-BPB and heparin (50 IU/ml) significantly reduced the [(14)C]5-HT release induced by these PLA(2)s. Our results demonstrate that BthTX-I, BthTX-II and PrTX-I recruit leucocyte into the pleural cavity of the rat by mechanisms unrelated to enzymatic activity and pleural mast cell degranulation.

HSP72 as a complementary protection against oxidative stress induced by exercise in the soleus muscle of rats

Given the potential of reactive oxygen species to damage intracellular proteins during subsequent bouts of muscle contractions, it was suggested that, when this production exceeds the antioxidant capacity, the preexisting antioxidant pathways may be complemented by the synthesis of the defense mechanism represented by heat shock proteins (HSPs), stress proteins with the function of repair and maintaining protein folding. To test this hypothesis, we analyzed reactive carbonyl derivatives in plasma and the expression of HSP72 and activities of enzymes from the oxidative and antioxidant defense systems in the soleus muscle of sedentary rats and rats trained by two protocols: continuous and intermittent. We analyzed all three groups at rest and 2 h after acute exercise. After 8 wk of training, the animals from both groups clearly demonstrated higher resistance to exercise. Both trained groups showed significantly higher citrate synthase, catalase, and glutathione reductase activities than the control group (P < 0.01). After acute exercise, catalase and glutathione reductase activities significantly decreased (P < 0.01) and plasma reactive carbonyl derivatives significantly increased (P < 0.05) in the sedentary group, suggesting an oxidative-stress condition as responsible for exhaustion in this group. Finally, after acute exercise, the induction of HSP72 expression occurred only in the sedentary group, suggesting that HSP72 acts as a complementary protective mechanism in exercise-induced oxidative stress.

Enzymatic characterization of a novel phospholipase A2 from Crotalus durissus cascavella rattlesnake (Maracambóia) venom

The PLA2 and crotapotin subunits of crotoxin from Crotalus durissus cascavella venom were purified by a combination of high-performance liquid chromatography (HPLC) molecular exclusion (Protein Pack 300SW column) and reverse-phase HPLC (RP-HPLC). Tricine SDS-PAGE showed that the PLA2 and crotapotins migrated as single bands with estimated molecular masses of 15 and 9 kDa, respectively. The amino acid composition of the PLA2 showed the presence of 14 half-cysteines and a high content of basic residues (Lys, Arg, His), whereas the crotapotins were rich in hydrophobic, negatively charged residues and half-cysteines. The PLA2 showed allosteric behavior, with maximal activity at pH 8.3 and 35-40 degrees C. C. d. cascavella PLA2 required Ca2+ for activity but was inhibited by Cu2+ and Zn2+ and by Cu2+ and Mg2+ in the presence and absence of Ca2+, respectively. Crotapotin (F3) and heparin inhibited the catalytic activity of the PLA2 by acting as allosteric inhibitors.