Intramural coronary artery and myocardial pathology in captive tigers (Panthera tigris) and African lions (Panthera leo)

There is limited published data regarding cardiovascular disease in nondomestic felid populations. To address this knowledge gap, necropsy cases of tigers and lions with representative myocardial samples submitted to a diagnostic laboratory were histologically assessed with hematoxylin and eosin and Sirius red stains. A total of 32 submissions (15 tigers, 17 lions) were identified in a 4-year period. All tigers and lions had some degree of coronary artery lesions in the left ventricle and/or interventricular septum. Major findings included moderate to marked arteriosclerosis in 8 tigers (53%) and 4 lions (24%) and moderate to marked perivascular fibrosis in 10 tigers (67%) and 9 lions (53%). Moreover, 10 tigers (67%) and 8 lions (47%) had coronary artery lesions with variable degrees of perivascular cardiomyocyte degeneration and/or loss. To our knowledge, this is the first report describing coronary artery pathology in captive tigers and lions.

Inhaled tigecycline is effective against Mycobacterium abscessus in vitro and in vivo

BACKGROUND

Mycobacterium abscessus causes chronic pulmonary infections. Owing to its resistance to most classes of antibiotics, treatment is complex and cure rates are only 45%. Tigecycline is active against M. abscessus, but severe toxicity and the need for IV administration limit its use.

OBJECTIVES

To assess the potential of inhaled tigecycline as a treatment for M. abscessus pulmonary disease, by measuring its efficacy in a mouse model of chronic M. abscessus pulmonary disease, establishing the intracellular activity of tigecycline against M. abscessus in human macrophages and measuring the activity of tigecycline in the sputum of cystic fibrosis patients.

METHODS

We infected GM-CSF knockout mice with M. abscessus by intrapulmonary aerosol. Infected mice were treated with tigecycline in 0.25, 1.25 and 2.5 mg doses, by inhalation, or untreated, for 28 days. Tigecycline was added to human peripheral blood-derived macrophages infected with M. abscessus to assess its intracellular activity. We performed a time-kill kinetics experiment of tigecycline against M. abscessus with and without sputum of cystic fibrosis patients.

RESULTS

Inhaled tigecycline proved highly effective against M. abscessus in GM-CSF knockout mice. The effect was dose dependent. Tigecycline showed potent activity against M. abscessus in macrophages and retained most of its activity in the presence of sputum of cystic fibrosis patients.

CONCLUSIONS

Inhaled tigecycline may represent a viable treatment option for M. abscessus pulmonary disease, where treatment outcomes are currently very poor. A stable and safe formulation is required to proceed to further pharmacodynamic studies and ultimately clinical trials.

Convergent evolution of pain-inducing defensive venom components in spitting cobras

Convergent evolution provides insights into the selective drivers underlying evolutionary change. Snake venoms, with a direct genetic basis and clearly defined functional phenotype, provide a model system for exploring the repeated evolution of adaptations. While snakes use venom primarily for predation, and venom composition often reflects diet specificity, three lineages of cobras have independently evolved the ability to spit venom at adversaries. Using gene, protein, and functional analyses, we show that the three spitting lineages possess venoms characterized by an up-regulation of phospholipase A2 (PLA2) toxins, which potentiate the action of preexisting venom cytotoxins to activate mammalian sensory neurons and cause enhanced pain. These repeated independent changes provide a fascinating example of convergent evolution across multiple phenotypic levels driven by selection for defense.

Disseminated Neospora caninum infection in a dog with severe colitis

A 12-y-old spayed female Schipperke dog with a previous diagnosis of inflammatory bowel disease was presented with a 2-mo history of severe colitis. The patient's condition progressed to hepatopathy, pneumonia, and dermatitis following management with prednisolone and dexamethasone sodium phosphate. Colonic biopsies identified severe necrosuppurative colitis with free and intracellular parasitic zoites. Postmortem examination confirmed extensive chronic-active ulcerative colitis, severe acute necrotizing hepatitis and splenitis, interstitial pneumonia, ulcerative dermatitis, myelitis (bone marrow), and mild meningoencephalitis with variable numbers of intracellular and extracellular protozoal zoites. PCR on samples of fresh colon was positive for Neospora caninum. Immunohistochemistry identified N. caninum tachyzoites in sections of colon, and a single tissue cyst in sections of brain. Administration of immunosuppressive drugs may have allowed systemic dissemination of Neospora from the intestinal tract.

[Beliefs and perceptions of the diagnosis and treatment of fibromyalgia in a group of rehabilitation and physical medicine specialists in Colombia]

INTRODUCTION

Fibromyalgia is a chronic disease characterised by the presence of musculoskeletal pain, usually associated with other symptoms, including depression, fatigue, and sleep disorders. There is no objective information on the beliefs and perceptions of the diagnosis and treatment of fibromyalgia among rehabilitation and physical medicine specialists. The aim of this study was to describe these beliefs and perceptions among a group of physical medicine and rehabilitation specialists in Colombia.

METHODS

We performed a cross-sectional study. A focus group was held with the participation of 2 rheumatologists, one physical medicine and rehabilitation specialist and an expert in qualitative research. The group designed a survey to assess the beliefs and perceptions of physical medicine and rehabilitation specialists of the diagnosis and treatment of fibromyalgia. The self-administered, anonymous questionnaire was completed during meetings of the Colombian Association of Physical Medicine and Rehabilitation.

RESULTS

The questionnaire was completed by 99 physical medicine and rehabilitation specialists. Of these, 17.1% (n=17) believed there was insufficient evidence to consider fibromyalgia a disease, 86.8% (n=86) used the ACR 1990 criteria to diagnose patients with fibromyalgia, and 33.3% (n=33) used the criteria of the 2010 classification. The most commonly used drugs for the management of fibromyalgia were antidepressants, prescribed by 84.8% of the surveyed physicians, followed by analgesics (75.7%) and anticonvulsants (66.6%). Concerning multidisciplinary management, 50.6% referred these patients to a rheumatologist and 40.7% to a psychiatrist. In all, 77.2% of rehabilitation specialists believed that patients with fibromyalgia should be managed by their specialty.

CONCLUSION

This study provides information on perceptions of the diagnosis and treatment of fibromyalgia among a group of Colombian rehabilitation specialists and found frequent use of the ACR 1990 classification. Among these physicians, the use of drugs, especially antidepressants and analgesics, was high. Most believed that patients with fibromyalgia should be treated by rehabilitation specialists.

Data on the main working conditions with influence on the development of hearing loss amongst the occupational population in Spain

Obtaining reliable and objective data on certain working conditions is necessary to analyse the causes and variables that can influence the development of hearing loss amongst the working population. Objective occupational data have been collected from a heterogeneous sample of 1418 workers in Spain, see “How activity type, time on the job and noise level on the job affect the hearing of the working population. Using Bayesian networks to predict the development of hipoacusia” (Barrero et al., 2018) [1]. Among the main factors analysed are the noise levels to which these workers are exposed, measured at their respective workstations, and the assessment of their hearing status, evaluated by audiometric medical tests. These factors provide information to predict the development of hypoacusia.

[Endoscopic incision of intravesical ureteroceles in patients with duplex system]

PURPOSE

To evaluate the clinical status and renal function of pa- tients with duplex system and intravesical ureterocele after drainage by cystoscopy.

MATERIAL AND METHODS

In 9 patients with duplex system and intravesical ureterocele drainage was performed to present recurrent urinary tract infections (7 children with episodes of pyelonephritis and sepsis) or obstruction of the urinary drainage. The mean age was 33 months (range 8-108 months). The thecnique was done under general anesthesia in the operating room and puncture of the ureterocele was performed using cystourethroscopy with loop electrode. The minimum follow-up was 12 months (range 12-48 months) and includes renal ultrasound, renal isotopic study (Mag3 with furosemide) and-echocystography study in patients with preoperative vesicoureteral reflux or postoperative urinary tract infection.

RESULTS

The average operative time was 60 minutes. Mean hospital stay was 48 hours. There were no complications during the procedure. In five patients urinary infection episodes disappeared. Ultrasound demonstrated decreased hydronephrosis and megaureter. In two patients the differential renal function following the technique improved. One patient with preoperative split renal function of 14% required nephrectomy. One patient had postoperative vesicoureteral reflux.

CONCLUSIONS

The drainage of intravesical ureterocele in patients with duplex system reduces episodes of urinary tract infection and urinary tract dilation.

Using Bayesian networks to analyze occupational stress caused by work demands: preventing stress through social support

Occupational stress is a major health hazard and a serious challenge to the effective operation of any company and represents a major problem for both individuals and organizations. Previous researches have shown that high demands (e.g. workload, emotional) combined with low resources (e.g. support, control, rewards) are associated with adverse health (e.g. psychological, physical) and organizational impacts (e.g. reduced job satisfaction, sickness absence). The objective of the present work is to create a model to analyze how social support reduces the occupational stress caused by work demands. This study used existing Spanish national data on working conditions collected by the Spanish Ministry of Labour and Immigration in 2007, where 11,054 workers were interviewed by questionnaire. A probabilistic model was built using Bayesian networks to explain the relationships between work demands and occupational stress. The model also explains how social support contributes positively to reducing stress levels. The variables studied were intellectually demanding work, overwork, workday, stress, and social support. The results show the importance of social support and of receiving help from supervisors and co-workers in preventing occupational stress. The study provides a new methodology that explains and quantifies the effects of intellectually demanding work, overwork, and workday in occupational stress. Also, the study quantifies the importance of social support to reduce occupational stress.

Antiplasmodial effect of the venom of Crotalus durissus cumanensis, crotoxin complex and Crotoxin B

The antiplasmodial activity of phospholipases A(2) (PLA(2)) isolated from different animals has been studied. We explored the in vitro anti Plasmodium falciparum effect of a fraction containing crotoxin, Crotoxin B and whole venom of the rattlesnake Crotalus durissus cumanensis. Fraction II (crotoxin complex) was obtained by size exclusion chromatography, whereas Crotoxin B was purified by RP-HPLC. The whole venom is active against the parasite at concentrations of 0.17±0.03 μg/ml, fraction II at 0.76±0.17 μg/ml and Crotoxin B at 0.6±0.04 μg/ml. Differences were observed in the cytotoxic activity against peripheral mononuclear cells, with Crotoxin B exhibiting the highest cytotoxicity. The concentration of Crotoxin B required to exert cytotoxic activity was higher than that required to exert antiplasmodial activity. Lethality in mice confirmed the higher toxicity and neurotoxicity of whole venom and fraction II, whereas Crotoxin B was not lethal at the doses tested. These results suggest the potential of Crotoxin B as a lead compound for antimalarial activity.

Tailored jeffamine molecular tools for ordering mesoporous silica

Herein, we report the formation of organized mesoporous silica materials prepared from a novel nonionic gemini surfactant, myristoyl-end-capped Jeffamine, synthesized from a polyoxyalkyleneamine (ED900). The behavior of the modified Jeffamine in water was first investigated. A direct micellar phase (L(1)) and a hexagonal (H(1)) liquid crystal were found. The structure of the micelles was investigated from the SAXS and the analysis by generalized indirect Fourier transformation, which show that the particles are globular of core-shell type. The myristoyl chains, located at the ends of the amphiphile molecule, are assembled to form the core of the micelles and, as a consequence, the molecules are folded over on themselves. Mesoporous materials were then synthesized from the self-assembly mechanism. The recovered materials were characterized by SAXS measurements, nitrogen adsorption-desorption analysis, and transmission and scanning electron microscopy. The results clearly evidence that by modifying the synthesis parameters, such as the surfactant/silica precursor molar ratio and the hydrothermal conditions, one can control the size and the nanostructuring of the resulting material. It was observed that, the lower the temperature of the hydrothermal treatment, the better the mesopore ordering.

Benthic recovery after fish farming cessation: a "beyond-BACI" approach

The development of a benthic environment after fish-farming cessation was examined. To ascertain whether recovery occurred, several abiotic (granulometry, acid-volatile sulfides, total phosphorus and redox potential) and biotic (polychaete abundance) variables were monitored using a "beyond-BACI" approach. Before the cessation of farming, the geochemical conditions and polychaete assemblages differed among the impacted and control sites. After cessation, an improvement of the geochemical conditions was achieved. A significant tendency toward a recovery of the polychaete assemblage in the impacted area was observed, but significant differences still remained compared with the control sites. The acid-volatile sulfide level was responsible for these differences. The abundance of polychaete families associated with organically enriched sediments diminished at the impacted site after cessation, whereas the abundance of some sensitive and omnivorous families increased. The "beyond-BACI" approach provided a wider framework than other approaches, enabling us to differentiate the natural variability from those changes induced by the fish farm and farming cessation.

Coexistence of two kinds of fluorinated hydrogenated micelles as building blocks for the design of bimodal mesoporous silica with two ordered mesopore networks

A simple and effective route has been developed for the synthesis of bimodal (3.6 and 9.4 nm) mesoporous silica materials that have two ordered interconnected pore networks. Mesostructures have been prepared through the self-assembly mechanism by using a mixture of polyoxyethylene fluoroalkyl ether and triblock copolymer as building blocks. The investigation of the R(F)(8)(EO)(9)/P123/water phase diagram shows that in the considered surfactant range of concentrations the system is micellar (L(1)). DLS measurements indicate that this micellar phase is composed of two types of micelles; the size of the first one at around 7.6 nm corresponds unambiguously to the pure fluorinated micelles. The second type of micelles at higher diameter consists of fluorinated micelles that have accommodated a weak fraction of P123 molecules. Thus, in this study the bimodal mesoporous silica is really templated by two kinds of micelles.

Do benthic biofilters contribute to sustainability and restoration of the benthic environment impacted by offshore cage finfish aquaculture?

Benthic biofilters were deployed under a cage fish farm and in two reference locations to assess the influence of the farm on the biofilters and the surroundings, as well as to verify the usefulness of this technology as a mitigation tool. The biofilters underneath the farm recruited a fouling community practically identical to that of the control biofilters, which included a variety of trophic strategies. The former showed a higher 15N enrichment, indicating that fouling beneath the farm was benefiting from the farm waste. The waste retention efficiency was low (0.02 g N m(-2) month(-1)) beneath the farm. Benthic biofilters aggregated demersal wild fish around and within them. Pelagic wild fish also frequently used the biofilters beneath the farm, forming compact shoals around them. The increased complexity of the habitat below the fish farm enhanced biodiversity, but this improvement did not lead to the recovery of the sediments around the biofilters.

Clinical experience with linezolid for the treatment of neurosurgical infections

OBJECTIVES

We sought to evaluate the clinical use of linezolid for the treatment of neurosurgical infections.

METHODS

Retrospective observational study of a cohort of hospitalized patients who received linezolid for a culture-positive neurosurgical infection from July 2004 to February 2009 in a tertiary hospital in Spain.

RESULTS

Seventeen patients were included in the study. Main comorbidities among these patients included one or more of the following: subarachnoidal or intraventricular hemorrhage (n=8), solid neurological cancer (n=7), corticosteroids(n=9) and hydrocephalus (n=6). Eight patients underwent a craniotomy and fourteen patients had an external ventricular drainage (EVD) as predisposing factors for infection. Meningitis was the most common infection (11; 64.7%), followed by ventriculitis (4; 23.5%) and brain abscesses (2;11.8%). The main causative organisms were coagulase-negative Staphylococcus spp. (13; 76.5%). Linezolid was used as the initial therapy in 8 episodes, after therapy failure in 6 and for other reasons in 3. The oral route was used in 9 (52.9%) episodes; linezolid was initiated orally in 2 cases. The mean duration of treatment was 26.5 days (range 15-58). No adverse events were reported. Sixteen (94.1%) patients were considered cured.There was one recurrence. The mean length of hospital stay was 45.6 (range 15-112) days and the mean duration of follow-up was 7.2 (range 0.4-32) months. No related deaths occurred during active episodes.

CONCLUSIONS

Linezolid was mainly indicated in post-neurosurgical EVD-associated infections due to coagulase-negative Staphylococcus spp. It was used as initial therapy in most cases. A high rate of clinical cure was observed and no related adverse events were reported. More than half of the patients were benefited by the advantages of the oral route of administration.

Immunochemical and biological characterization of monoclonal antibodies against BaP1, a metalloproteinase from Bothrops asper snake venom

BaP1 is a P-I class of Snake Venom Metalloproteinase (SVMP) relevant in the local tissue damage associated with envenomations by Bothrops asper, a medically-important species in Central America and parts of South America. Six monoclonal antibodies (MoAb) against BaP1 (MABaP1) were produced and characterized regarding their isotype, dissociation constant (K(d)), specificity and ability to neutralize BaP1-induced hemorrhagic and proteolytic activity. Two MABaP1 are IgM, three are IgG1 and one is IgG2b. The K(d)s of IgG MoAbs were in the nM range. All IgG MoAbs recognized conformational epitopes of BaP1 and B. asper venom components but failed to recognize venoms from 27 species of Viperidae, Colubridae and Elapidae families. Clone 7 cross-reacted with three P-I SVMPs tested (moojeni protease, insularinase and neuwiedase). BaP1-induced hemorrhage was totally neutralized by clones 3, 6 and 8 but not by clone 7. Inhibition of BaP1 enzymatic activity on a synthetic substrate by MABaP1 was totally achieved by clones 3 and 6, and partially by clone 8, but not by clone 7. In conclusion, these neutralizing MoAbs against BaP1 may become important tools to understand structure-function relationships of BaP1 and the role of P-I class SVMP in snakebite envenomation.

SIA system employing the transient response from a potentiometric sensor array--Correction of a saline matrix effect

A Sequential Injection Analysis (SIA) system and an 8-potentiometric all-solid-state sensor array were coupled in a simple and automated electronic tongue device. The potentiometric sensors used were planar microfabricated structures with standard PVC membranes deposited onto a gold contact. The SIA system permitted the automated operation and generation of the calibration data, needed to build an Artificial Neural Network model, thanks to the precise dosing and mixing of volumes of stock solutions. The resolution of a four-ion mixture, i.e. ammonium, sodium, nitrate and chloride was the study case used for characterization of the system. Two different variants for signal acquisition, steady-state and transient recording, were arranged and compared. The dynamic treatment is shown to offer improved performance thanks to the benefits of the kinetic resolution. For this, it first extracts meaningful data from a FFT transform of each sensor's transient, which is then fed to an ANN model for estimation of each concentration in the four-ion mixture. While in a standard laboratory situation there was no difference between the two approaches, the dynamic treatment allowed the correction of a matrix effect in the case study, where an uncontrolled saline effect could be counterbalanced.

The Caenorhabditis elegans genome: a multifractal analysis

The Caenorhabditis elegans genome has several regular and irregular characteristics in its nucleotide composition; these are observed within and between chromosomes. To study these particularities, we carried out a multifractal analysis, which requires a large number of exponents to characterize scaling properties. We looked for a relationship between the genetic information content of the chromosomes and multifractal parameters and found less multifractality compared to the human genome. Differences in multifractality among chromosomes and in regions of chromosomes, and two group averages of chromosome regions were observed. All these differences were mainly dependent on differences in the contents of repetitive DNA. Based on these properties, we propose a nonlinear model for the structure of the C. elegans genome, with some biological implications. These results suggest that examining differences in multifractality is a viable approach for measuring local variations of genomic information contents along chromosomes. This approach could be extended to other genomes in order to characterize structural and functional regions of chromosomes.

The snake venom metalloproteinase BaP1 induces joint hypernociception through TNF-alpha and PGE2-dependent mechanisms

BACKGROUND AND PURPOSE

Matrix metalloproteinases (MMPs) have been implicated in joint tissue destruction in arthritis. However, MMPs have not been assigned a role in joint pain. We investigated the ability of BaP1, a metalloproteinase from Bothrops asper snake venom, with structural homology to MMPs, to induce joint hypernociception.

EXPERIMENTAL APPROACH

Animals received intra-articular (i.art.) BaP1. Hypernociception was assessed using the rat-knee joint articular incapacitation test. Cell influx, prostaglandin E(2) (PGE(2)), and TNF-alpha levels were assessed in joint exudates following BaP1 injection.

KEY RESULTS

BaP1 (5 microg per joint) provoked hypernociception between 1 and 6 h after i.art. injection. Cell influx, mostly neutrophils, was maximal 3 h after BaP1 i.art. injection. BaP1 also led to increase in PGE(2) and TNF-alpha levels in the joint exudates. Pretreatment with either indomethacin (4 mg.kg(-1) i.p.) or with an anti-TNF-alpha antiserum (i.art.) significantly inhibited both BaP1-induced joint hypernociception and cell influx. In isolated rat peritoneal macrophages, BaP1 increased cyclooxygenase (COX)-2 expression, while not altering that of COX-1.

CONCLUSIONS AND IMPLICATIONS

This is the first demonstration that a metalloproteinase promotes joint hypernociception. This effect involves local release of PGE(2) and TNF-alpha. BaP1-induced increase in PGE(2) is associated to increased COX-2 expression in macrophages. Blocking PGE(2) or TNF-alpha inhibits BaP1-induced hypernociception. In addition to unravelling a hitherto unknown mechanism whereby TNF blockade provides analgesia in arthritis, the data show, for the first time that MMPs are involved in inflammatory joint hypernociception and induce COX-2 expression.

Error growth patterns in systems with spatial chaos: from coupled map lattices to global weather models

Error growth in spatiotemporal chaotic systems is investigated by analyzing the interplay between temporal and spatial dynamics. The spatial correlation and localization of relative fluctuations grow and decay indicating two different regimes, before and after saturation by nonlinear effects. This general behavior is shown to hold both in simple coupled map lattices and in global weather models. This explains the increasing or decreasing trends previously observed in the exponential growth rate of these spatiotemporal systems.

Effect of calcineurin inhibitors on myotoxic activity of crotoxin and Bothrops asper phospholipase A2 myotoxins in vivo and in vitro

Previous studies have shown that calcineurin activity plays a critical role in the myotoxic activity induced by crotoxin (CTX), a group II phospholipase A(2) (PLA(2)) with neurotoxic and myotoxic actions. In order to address whether calcineurin is also important for the activity of non-neurotoxic group II PLA(2) myotoxins we have compared the effects of calcineurin inhibition on the myotoxic capacity of CTX and the non-neurotoxic PLA(2)s, myotoxin II (Mt II) and myotoxin III (Mt III) from Bothrops asper venom. Rats were treated with cyclosporin A (CsA) or FK506, calcineurin inhibitors, and received an intramuscular injection of either CTX, Mt II or Mt III into the tibialis anterior. Animals were killed 24 h after injection of toxins. Tibialis anterior was removed and stored in liquid nitrogen. Myofibers in culture were also treated with CsA or FK506 and exposed to CTX, Mt II and Mt III. It was observed that, in contrast to CTX, CsA and FK506 do not attenuate myotoxic effects induced by both Mt II and Mt III in vivo and in vitro. The results of the present study suggest that calcineurin is not essential for the myotoxic activity of Mt II and Mt III, indicating that distinct intracellular pathways might be involved in myonecrosis induced by neurotoxic CTX and non-neurotoxic Bothrops sp. PLA(2) myotoxins. Alternatively, calcineurin dependent fast fiber type shift might render the muscle resistant to the action of CTX, without affecting its susceptibility to Bothrops sp. myotoxins.

Role of nitric oxide in the local and systemic pathophysiological effects induced by Bothrops asper snake venom in mice

OBJECTIVE

To assess the role of nitric oxide in the most relevant local and systemic manifestations in mice injected with the venom of the snake Bothrops asper. Mice were pretreated with nitric oxide synthase inhibitors, and the modifications of the pathological effects induced by the venom were tested.

RESULTS

Inhibition of NO synthesis did not affect acute local myonecrosis and hemorrhage in muscle tissue upon intramuscular injection of venom. Local footpad edema was reduced in mice pretreated with the NO synthase inhibitor L-NAME, and a reduction in the extent of inflammatory infiltrate in muscle tissue was observed after envenomation in mice pretreated with L-NAME and aminoguanidine. The most pronounced effect of NOS inhibition by L-NAME was an increment in the lethal activity of the venom, when injected by the intraperitoneal route.

CONCLUSION

Nitric oxide does not seem to play a significant role in the local acute pathological alterations (hemorrhage and myonecrosis) induced by B. asper venom in mice, although it contributes to edema and inflammatory infiltrate. Nitric oxide exerts a protective role in the systemic pathophysiological manifestations leading to lethality.

Oil/water droplet formation by temperature change in the water/c(16)e(6)/mineral oil system

Droplet sizes of oil/water (O/W) nanoemulsions prepared by the phase inversion temperature (PIT) method, in the water/C16E6/mineral oil system, have been compared with those given by a theoretical droplet model, which predicts a minimum droplet size. The results show that, when the phase inversion was started from either a single-phase microemulsion (D) or a two-phase W+D equilibrium, the resulting droplet sizes were close to those predicted by the model, whereas, when emulsification was started from W+D+O or from W+D+Lalpha (Lalpha = lamellar liquid crystal) equilibria, the difference between the measured and predicted values was much higher. The structural changes produced during the phase inversion process have been investigated by the 1H-PFGSE-NMR technique, monitoring the self-diffusion coefficients for each component as a function of temperature. The results have confirmed the transition from a bicontinuous D microemulsion at the hydrophile-lipophile balance (HLB) temperature to oil nanodroplet dispersion in water when it is cooled to lower temperatures.

Approach to predictability via anticipated synchronization

Predictability of chaotic systems is limited, in addition to the precision of the knowledge of the initial conditions, by the error of the models used to extract the nonlinear dynamics from the time series. In this paper, we analyze the predictions obtained from the anticipated synchronization scheme using a chain of slave neural network approximate replicas of the master system. We compare the maximum prediction horizons obtained with those attainable using standard prediction techniques.

Pan-African polyspecific antivenom produced by caprylic acid purification of horse IgG: an alternative to the antivenom crisis in Africa

A polyspecific Pan-African antivenom has been produced from the plasma of horses immunized with a mixture of the venoms of Echis ocellatus, Bitis arietans and Naja nigricollis, the three most medically important snakes in sub-Saharan Africa. The antivenom is a whole IgG preparation, obtained by caprylic acid precipitation of non-IgG plasma proteins. The antivenom effectively neutralizes the most important toxic activities of the three venoms used in the immunization in standard assays involving preincubation of venom and antivenom before testing. This antivenom compares favourably with other antivenoms designed for use in Africa with respect to neutralization of the toxins present in the venom of E. ocellatus. Caprylic acid fractionation of horse hyperimmune plasma is a simple, convenient and cheap protocol for the manufacture of high quality whole IgG antivenoms. It constitutes a potentially valuable technology for the alleviation of the critical shortage of antivenom in Africa.

[Evaluation of cerebral blood perfusion in patients undergoing carotid endarterectomy using densitometric analysis of conventional cranial CT]

OBJECTIVE

To evaluate the efficacy of densitometric analysis of cranial CT imaging in the measurement of areas with low cerebral blood flow and lack of hemodynamic reserve in patients undergoing carotid endarterectomy.

PATIENTS AND METHODS

40 consecutive patients undergoing carotid endarterectomy have been included in the study. All of them had preoperative cranial CT, pre and postoperative basal and acetazolamide SPECT. Cranial CT imaging after digitalization and computer processing were obtained with 4 densitometric patterns: 1). normal cerebral blood perfusion; 2). ischemic or low brain blood perfusion (patron I); 3). parenchyma without cerebral hemodynamic reserve (patron nR), and 4). brain infarction.

RESULTS

32 out of 40 (80 %) patients had abnormal densitometric patterns: 19 nR patterns (47.5 %), 11 I pattern (27.5 %) and 2 established brain infarction. The correlation between densitometric cranial TC imaging and SPECT was 92% when analyzing areas with hypoperfusion (S: 96.5 %; E: 82 %). Cranial CT detected 12/13 of patients who lacked cerebral hemodynamic reserve in the SPECT analysis (S: 74 %; E: 92 %; Vpp: 95 %).

CONCLUSIONS

There is a good correlation between analysis of densitometric cranial TC imaging and SPECT in determining low cerebral blood flow areas and lack of cerebral hemodynamic reserve. This method could help to improve carotid surgery indications in patients with carotid stenosis.

Neutrophils do not contribute to local tissue damage, but play a key role in skeletal muscle regeneration, in mice injected withBothrops aspersnake venom

Local tissue damage induced by crotaline snake venoms includes edema, myonecrosis, hemorrhage, and an inflammatory response associated with a prominent cellular infiltrate. The role of neutrophils in the local tissue damage induced by Bothrops asper snake venom and by myotoxin I, a phospholipase A2 isolated from this venom, was investigated. Male Swiss mice were pretreated with either an antimouse granulocyte rat monoclonal immunoglobulin G (IgG) antibody or with isotype-matched control antibody. No significant differences in these local effects were observed between mice pretreated with antigranulocyte antibodies and those receiving control IgG. Moreover, myotoxicity induced by B. asper myotoxin I was similar in neutrophil-depleted and control mice. The role of neutrophils in the process of skeletal muscle regeneration was also assessed. Muscle regeneration was assessed by quantifying the muscle levels of creatine kinase and by morphometric histological analysis of the area comprised by regenerating cells in damaged regions of skeletal muscle. Mice depleted of neutrophils and then injected with B. asper venom showed a more deficient regenerative response than mice pretreated with control IgG. Moreover, a drastic difference in the regenerative response was observed in mice injected with myotoxin I, because animals pretreated with control IgG showed a successful regeneration, whereas those depleted of neutrophils had abundant areas of necrotic tissue that had not been removed 7 days after injection, associated with reduced contents of creatine kinase. It is concluded that (1) neutrophils do not play a significant role in the acute local pathological alterations induced by the venom of B. asper, and (2) neutrophils play a prominent role in the process of skeletal muscle regeneration after injection of B. asper venom and myotoxin I, probably related to the phagocytosis of necrotic material and the recruitment of other inflammatory cells, two events directly associated with a successful muscle regenerative response.

Hyperalgesia induced by Asp49 and Lys49 phospholipases A2 from Bothrops asper snake venom: pharmacological mediation and molecular determinants

The ability of Lys49 and Asp49 phospholipases A(2) (PLA(2)), from Bothrops asper snake venom, to cause hyperalgesia was investigated in rats, using the paw pressure test. Intraplantar injection of both toxins (5-20 micro g/paw) caused hyperalgesia, which peaked 1h after injections. Incubation of both proteins with heparin, prior to their injection, partially reduced this response. Chemical modification of Asp49 PLA(2) with p-bromophenacyl bromide (p-BPB), which abrogates its PLA(2) activity, also abolished hyperalgesia. Intraplantar injection of a synthetic peptide corresponding to the C-terminal sequence 115-129 of Lys49 PLA(2), caused hyperalgesia of similar time course, but varying magnitude, than that induced by the native protein. In contrast, a homologous peptide derived from the Asp49 PLA(2) did not show any nociceptive effect. Hyperalgesia induced by both PLA(2)s was blocked by the histamine and serotonin receptor antagonists promethazine and methysergide, respectively, by the bradykinin B(2) receptor antagonist HOE 140 and by antibodies to tumor necrosis factor alfa (TNFalpha) and interleukin 1 (IL-1). Pretreatment with guanethidine, atenolol, prazosin and yohimbine, inhibitors of sympathomimetic amines, or with indomethacin, inhibitor of the cyclo-oxygenase pathway, reduced Lys49 PLA(2)-induced hyperalgesia without interfering with the nociceptive activity of Asp49 PLA(2). The hyperalgesic response to both myotoxins was not modified by pretreatment with celecoxib, an inhibitor of the cyclo-oxygenase type II, by zileuton, an inhibitor of the lipoxygenase pathway or by N(g)-methyl-L-arginine (LNMMA), an inhibitor of nitric oxide synthase. These results suggest that Asp49 and Lys49 PLA(2)s are important hyperalgesic components of B. asper venom, and that Lys49 and Asp49 PLA(2)s exert their algogenic actions through different molecular mechanisms.

Evaluation of antivenoms in the neutralization of hyperalgesia and edema induced by Bothrops jararaca and Bothrops asper snake venoms

Neutralization of hyperalgesia induced by Bothrops jararaca and B. asper venoms was studied in rats using bothropic antivenom produced at Instituto Butantan (AVIB, 1 ml neutralizes 5 mg B. jararaca venom) and polyvalent antivenom produced at Instituto Clodomiro Picado (AVCP, 1 ml neutralizes 2.5 mg B. aspar venom). The intraplantar injection of B. jararaca and B. asper venoms caused hyperalgesia, which peaked 1 and 2 h after injection, respectively. Both venoms also induced edema with a similar time course. When neutralization assays involving the independent injection of venom and antivenom were performed, the hyperalgesia induced by B. jararaca venom was neutralized only when bothropic antivenom was administered iv 15 min before venom injection, whereas edema was neutralized when antivenom was injected 15 min or immediately before venom injection. On the other hand, polyvalent antivenom did not interfere with hyperalgesia or edema induced by B. asper venom, even when administered prior to envenomation. The lack of neutralization of hyperalgesia and edema induced by B. asper venom is not attributable to the absence of neutralizing antibodies in the antivenom, since neutralization was achieved in assays involving preincubation of venom and antivenom. Cross-neutralization of AVCP or AVIB against B. jararaca and B. asper venoms, respectively, was also evaluated. Only bothropic antivenom partially neutralized hyperalgesia induced by B. asper venom in preincubation experiments. The present data suggest that hyperalgesia and edema induced by Bothrops venoms are poorly neutralized by commercial antivenoms even when antibodies are administered immediately after envenomation.

Crystallization and preliminary diffraction data of BaP1, a haemorrhagic metalloproteinase from Bothrops asper snake venom

BaP1 is a metalloproteinase isolated from the venom of the Central American snake Bothrops asper (terciopelo). It is a 24 kDa protein consisting of a single chain which includes the metalloproteinase domain only, therefore being classified as a class P-I snake-venom metalloproteinase. BaP1 induces prominent local tissue damage, such as haemorrhage, myonecrosis, blistering, dermonecrosis and oedema. In order to elucidate its structure, BaP1 was crystallized by the hanging-drop vapour-diffusion technique in 0.1 M bicine pH 9.0, 10% PEG 20 000 and 2%(v/v) dioxane. Diffraction data were observed to a resolution of 2.7 A. Crystals belong to space group P2(1)2(1)2(1), with unit-cell parameters a = 38.22, b = 60.17, c = 86.09 A.

Systemic cytokine response in children bitten by snakes in Costa Rica

BACKGROUND

To characterize the host response to venom from snakes of the family Viperidae in Costa Rica, we investigated the release of cytokines: IL-1, IL-6, IL-8, TNF-alpha, MIP-1beta, and RANTES in pediatric patients who were bitten by a snake.

METHODS

Patients were included in this study if they were admitted to the hospital within 24 hours of the snakebite. Blood samples were taken immediately on admission to the hospital, and then at intervals of 3, 12, and 24 hours, and on days 3, 5, and 7 after the accident. Patients received gentamicin plus clindamycin or gentamicin plus penicillin intravenously for a minimum of 3 days or longer if necessary. IL-1, IL-8, TNF-alpha, MIP-1beta, and RANTES were determined by monoclonal antibody-based ELISAs, while IL-6 was determined by bioassay.

RESULTS

Eighteen patients were included in this study; 15 were bitten by Bothrops asper and three by B. lateralis. Eleven patients were male. Median (range) age was 9 (1-12) years. Nine patients had detectable serum concentrations of IL-6 (200 pg/ mL) and IL-8 (51 pg/mL) on admission, increasing to 500 pg/mL and 115 pg/mL for IL-6 and IL-8, respectively, during the first 12-24 hours. Cytokine concentrations returned to normal or undetectable ranges by 72 hours. TNF-alpha concentrations peaked at 12 hours (mean: 48 pg/mL). Low, but detectable concentrations of MIP-1beta were observed in some patients at various time intervals (48 pg/mL), whereas IL-1 was not detectable at any time point. Regulated on Activation Normal T cell Expressed and Secreted (RANTES) concentrations were evaluated in only five patients, being elevated in all of them. Patients with elevated cytokine concentrations required early fasciotomy (<24 hours after the accident) more often than those who had normal or undetectable cytokine concentrations (P < 0.05). There were no statistically significant associations between severity of envenomation, or outcome, and elevated serum cytokine concentrations (P > 0.05).

CONCLUSIONS

Bothrops sp snake venoms induce clinical and pathophysiologic alterations similar to acute trauma, with release of proinflammatory cytokines. A better understanding of the role of the inflammatory response could lead to the development of new therapeutic strategies to improve the outcome in snakebitten patients.

Bothrops asper and Bothrops jararaca snake venoms trigger microbicidal functions of peritoneal leukocytes in vivo

Venoms from snakes of the genus Bothrops cause pronounced local effects in the victims. These alterations result not only from the direct toxic action of venom components, but also from the prominent inflammatory reaction associated with these envenomations. In this study we investigated the ability of Bothrops asper (BaV) and Bothrops jararaca (BjV) venoms to induce cellular influx and microbicidal functions in leukocytes. BaV and BjV (5 microg/animal) caused a long lasting infiltration of leukocytes (3-48 h) when injected into mouse peritoneal cavity. Both venoms increased phagocytosis and production of hydrogen peroxide (H2O2) by polymorphonuclear (PMN) and mononuclear (MN) peritoneal leukocytes. In addition, nitric oxide (NO) production by macrophages was also enhanced after the venom injections. This effect was inhibited by treating animals with L-NAME and aminoguanidine, thus suggesting the induction of iNOS synthesis by the venoms. Western blot analysis confirmed the expression of iNOS in macrophages. BaV and BjV injection led to increased levels of IFN-gamma at the site of inflammation. Since IFN-gamma is an effective inducer of iNOS expression, an indirect action of the venoms on iNOS expression can be proposed. A marked formation of nitrotyrosine-containing proteins was also observed in macrophage homogenates. Based on these results, we suggest that reactive oxygen and nitrogen-derived species are involved in the pathogenesis of the local tissue damage characteristic of Bothrops sp envenomations.

Effects of chemical modifications of crotoxin B, the phospholipase A(2) subunit of crotoxin from Crotalus durissus terrificus snake venom, on its enzymatic and pharmacological activities

Crotoxin B, the basic Asp49-PLA(2) subunit from crotoxin, the main component of Crotalus durissus terrificus venom, displays myotoxic, edema-inducing, bactericidal (upon Escherichia coli), liposomal-disrupting and anticoagulant activities. Chemical modifications of His (with 4-bromophenacyl bromide, BPB), Tyr (with 2-nitrobenzenesulphonyl fluoride, NBSF), Trp (with o-nitrophenylsulphenyl chloride, NPSC) and Lys (with acetic anhydride) residues of this protein, in addition to cleavage with cyanogen bromide (CNBr) and inhibition with ethylenediaminetetraacetic acid (EDTA), were carried out in order to study their effects on enzymatic and pharmacological activities. Lethality was reduced after modification of His or Lys residues, as well as after cleavage with CNBr, while enzymatic activity was completely abolished after modification of His or incubation with EDTA. Modification of Lys or Tyr, or cleavage with CNBr, partially reduced enzymatic activity. Anticoagulant activity was modified similarly to enzymatic activity, evidencing the dependency of this pharmacological effect on catalytic activity. Myotoxicity was reduced after modification of His or Lys, as well as after cleavage with CNBr, whereas EDTA reduced this effect to a lesser extent. Bactericidal effect was significantly reduced only after modification of Lys and after cleavage with CNBr. Edema-inducing activity was partially inhibited after treatment with EDTA and strongly reduced after acetylation of Lys residues and cleavage with CNBr, being only partially reduced after His alkylation. On the other hand, liposome disrupting activity was only partially reduced after modification of His and Tyr or after cleavage with CNBr. Modification of Trp residue partially reduced lethality and myotoxicity but did not affect enzymatic or anticoagulant activities. These data indicate that enzymatic activity is relevant for some pharmacological effects induced by crotoxin B (mainly lethal, myotoxic and anticoagulant activities), and also evidence that this subunit of crotoxin displays regions different from the active catalytic site which are involved in some of the toxic and pharmacological effects induced by this phospholipase A(2).

Pharmacological modulation of hyperalgesia induced by Bothrops asper (terciopelo) snake venom

The ability of Bothrops asper snake venom to cause hyperalgesia was investigated in rats, using the paw pressure test. Intraplantar injection of the venom (5-15 microg/paw) caused a dose and time-related hyperalgesia, which peaked 2h after venom injection. Bothrops asper venom-induced hyperalgesia was blocked by the bradykinin B(2) receptor antagonist HOE 140 and attenuated by dexamethasone, an inhibitor of phospholipase A(2). Inhibition of the lipoxygenase pathway by NDGA abrogated the algogenic phenomenon. The hyperalgesic response was not modified by pretreatment with indomethacin, an inhibitor of the cyclo-oxygenase pathway, by meloxicam, an inhibitor of the type 2 cyclo-oxygenase pathway, by the PAF receptor antagonist BN52021 or by anti-TNF-alpha or anti-interleukin 1 antibodies. Intraplantar injection of the venom also caused an oedematogenic response which was not modified by any of these pharmacological treatments. These results suggest that hyperalgesia induced by Bothrops asper venom is, at least partially, mediated by bradykinin, phospholipase A(2) activity and leukotrienes. Distinct mechanisms are involved in the development of hyperalgesia and oedema induced by the venom.

Modulation of the susceptibility of human erythrocytes to snake venom myotoxic phospholipases A(2): role of negatively charged phospholipids as potential membrane binding sites

Cerrophidion (Bothrops) godmani myotoxins I (CGMT-I) and II (CGMT-II), Asp-49 and Lys-49 phospholipases A(2) (PLA2s), which drastically differ in enzymatic activity, were devoid of direct hemolytic effects on erythrocytes (RBC) from different species despite the fact that enzymatically active CGMT-I was able to hydrolyze RBC membrane phospholipids and disrupt liposomes prepared from RBC lipids. Human RBC did not become susceptible to the toxins after treatment with neuraminidase or after altering membrane fluidity with cholesterol or sublytic concentrations of detergent. Unlike normal RBC, significant hemolysis was induced by CGMT-II and another similar Lys-49 isoform, B. asper MT-II (BAMT-II), in RBC enriched with phosphatidylserine (PS). Hemolysis was greater in RBC preincubated with pyridyldithioethylamine (PDA), a potent inhibitor of aminophospholipid transport. RBC enriched with phosphatidic acid (PA) also became susceptible to the myotoxins but was unaffected by PDA. Cells enriched with phosphatidylcholine (PC) remained resistant to the action of the toxins. BAMT-II also induced damage in black lipid membranes prepared with PS but not PC alone. When RBC binding of BAMT-II was measured by enzyme-linked immunosorbent assay, it was observed that PS- and PA-enriched erythrocytes were always able to capture more toxin than normal and PC-enriched RBC. This effect was significantly improved by PDA (in the case of PS) and it was observed either in the presence or in the absence of calcium in the medium. These data suggest that negatively charged lipids in the outer leaflet of cell membranes constitute myotoxic PLA2 binding sites. The scarcity of anionic phospholipids in the outer leaflet of RBC could explain their resistance to the action of these PLA2s.

Pathological alterations induced by neuwiedase, a metalloproteinase isolated from Bothrops neuwiedi snake venom

The pathological alterations induced by neuwiedase, a 22 kDa class P-I metalloproteinase from the venom of the South American pit viper Bothrops neuwiedi, were studied in mice. Neuwiedase was devoid of hemorrhagic activity when tested in the skin up to a dose of 200 microgram, and also after intramuscular injection in the gastrocnemius. However, it induced bleeding when applied onto the mouse cremaster muscle in intravital microscopy experiments, and caused pulmonary hemorrhage when injected intravenously at doses higher than 5 microgram/g. Median lethal dose (LD(50)) by the intravenous route was 5 microgram/g, whereas LD(50) of crude venom was 0.47 microgram/g. After intramuscular injection, neuwiedase induced a mild myotoxic effect, evidenced histologically and by the increment in plasma creatine kinase activity, but it was devoid of hemorrhagic and thrombotic effects. In contrast, crude B. neuwiedi venom induced prominent hemorrhage and myonecrosis in gastrocnemius muscle. Both venom and neuwiedase induced an inflammatory reaction in muscle tissue characterized by abundant polymorphonuclear leukocytes. Moreover, a conspicuous edema developed in the foot pad after subcutaneous injection of neuwiedase. Anti-neuwiedase antibodies produced in rabbits were effective in the neutralization of hemorrhagic activity of crude venom, evidencing immunological cross-reactivity between neuwiedase and other hemorrhagic metalloproteinases present in the venom, and suggesting that metalloproteinases devoid of, or having low, hemorrhagic activity could be good immunogens to generate antibodies effective against high molecular mass metalloproteinasas having potent hemorrhagic activity. It is concluded that neuwiedase, despite its lack of hemorrhagic effect when injected in the gastrocnemius muscle, contributes to local tissue damage by inducing edema, inflammatory infiltrate and mild myotoxicity, and by degrading extracellular matrix components. In addition, large doses of neuwiedase may contribute to pulmonary bleeding

Comparison between IgG and F(ab')(2) polyvalent antivenoms: neutralization of systemic effects induced by Bothrops asper venom in mice, extravasation to muscle tissue, and potential for induction of adverse reactions

Whole IgG and F(ab')(2) equine-derived polyvalent (Crotalinae) antivenoms, prepared from the same batch of hyperimmune plasma, were compared in terms of neutralization of the lethal and defibrinating activities induced by Bothrops asper venom, their ability to reach the muscle tissue compartment in envenomated mice, and their potential for the induction of adverse reactions. Both preparations were adjusted to the same potency against the lethal effect of B. asper venom in experiments involving preincubation of venom and antivenom. Then, "rescue" experiments were performed, i.e. antivenom was administered either intravenously or intramuscularly at various times after envenomation. IgG and F(ab')(2) antivenoms were equally effective in the neutralization of lethality, both being more effective when administered i.v. than after i.m. injection. Neutralization decreased as the time lapse between envenomation and treatment increased. No significant differences were observed in the ability of antivenoms to neutralize defibrinating activity of B. asper venom in experiments involving independent injection of venom and antivenoms. There was a much higher accumulation of equine antibodies in muscle tissue that had been injected with B. asper venom than in non-envenomated tissue, indicating that venom-induced microvessel damage probably favors a prominent and similar extravasation of both IgG and F(ab')(2) antibodies. This may explain the similar effectiveness of both types of antivenom in previously reported studies on the neutralization of venom-induced local tissue damage. Both IgG and F(ab')(2) antivenoms activate human complement in vitro and induce an anti-equine immunoglobulin response in mice, indicating that Fc removal per se does not eliminate the potential for inducing adverse reactions. However, IgG antivenom had higher anticomplementary activity and induced a stronger anti-immunoglobulin response than F(ab')(2) antivenom.

Venom of the crotaline snake Atropoides nummifer (jumping viper) from Guatemala and Honduras: comparative toxicological characterization, isolation of a myotoxic phospholipase A(2) homologue and neutralization by two antivenoms

A comparative study was performed on the venoms of the crotaline snake Atropoides nummifer from Guatemala and Honduras. SDS-polyacrylamide gel electrophoresis, under reducing conditions, revealed a highly similar pattern of these venoms, and between them and the venom of the same species from Costa Rica. Similar patterns were also observed in ion-exchange chromatography on CM-Shephadex C-25, in which a highly basic myotoxic fraction was present. This fraction was devoid of phospholipase A(2) activity and strongly reacted, by enzyme-immunoassay, with an antiserum against Bothrops asper myotoxin II, a Lys-49 phospholipase A(2) homologue. A basic myotoxin of 16 kDa was isolated to homogeneity from the venom of A. nummifer from Honduras, showing amino acid composition and N-terminal sequence similar to those of Lys-49 phospholipase A(2) variants previously isolated from other crotaline snake venoms. Guatemalan and Honduran A. nummifer venoms have a qualitatively similar toxicological profile, characterized by: lethal; hemorrhagic; myotoxic; edema-forming; coagulant; and defibrinating activities, although there were significant quantitative variations in some of these activities between the two venoms. Neutralization of toxic activities by two commercially-available antivenoms in the region was studied. Polyvalent antivenom produced by Instituto Clodomiro Picado was effective in the neutralization of: lethal; hemorrhagic; myotoxic; coagulant; defibrinating; and phospholipase A(2) activities, but ineffective against edema-forming activity. On the other hand, MYN polyvalent antivenom neutralized: hemorrhagic; myotoxic; coagulant; defibrinating; and phospholipase A(2) activities, albeit with a lower potency than Instituto Clodomiro Picado antivenom. MYN antivenom failed to neutralize lethal and edema-forming activities of A. nummifer venoms.

Characterization of aspercetin, a platelet aggregating component from the venom of the snake Bothrops asper which induces thrombocytopenia and potentiates metalloproteinase-induced hemorrhage

Thrombocytopenia occurs in a number of patients bitten by Bothrops asper, a species responsible for the majority of snakebites in Central America and southern Mexico. In this work we describe the isolation of a new platelet-aggregating protein, named aspercetin, from the venom of B. asper, which induces thrombocytopenia in mice. Isolation was carried out by a combination of ion-exchange chromatography on DEAE-Sepharose and affinity chromatography on Affi-Gel Blue. Aspercetin is a disulfide-linked heterodimer, with a pI of 4.5 and a molecular mass of 29,759 Da, detemined by MALDI-ESI mass spectrometry. N-terminal sequence shows homology with a number of venom proteins which belong to the C-type lectin family. Aspercetin has functional similarities with botrocetin, from B. jararaca venom, since it induces platelet aggregation only in the presence of plasma or purified von Willebrand factor. Aspercetin-mediated platelet aggregation results from the interaction of von Willebrand factor with platelet receptor GPIb. Aspercetin lacks anticoagulant effect and does not agglutinate erythrocytes, in contrast with other representatives of the C-type lectin family isolated from snake venoms. Moreover, aspercetin is not lethal, nor does it induce myonecrosis, hemorrhage and edema. When injected intravenously or intramuscularly in mice it induces a rapid, dose-dependent drop in platelet counts and prolongs the bleeding time, suggesting that it may play a role in the thrombocytopenia that develops in a number of B. asper envenomations. Moreover, mice injected intravenously with aspercetin and then receiving an intradermal injection of B. asper hemorrhagic metalloproteinase BaP1 develop a larger hemorrhagic lesion than mice receiving only BaP1. This suggests that aspercetin, by reducing platelet numbers, may

Dissociation of Enzymatic and Pharmacological Properties of Piratoxins-I and -III, Two Myotoxic Phospholipases A2 from Bothrops pirajai Snake Venom

Piratoxins (PrTX) I and III are phospholipases A2 (PLA2s) or PLA2 homologue myotoxins isolated from Bothrops pirajai snake venom, which also induce myonecrosis, bactericidal activity against Escherichia coli, disruption of artificial membranes, and edema. PrTX-III is a catalytically active hemolytic and anticoagulant Asp49 PLA2, while PrTX-I is a Lys49 PLA2 homologue, which is catalytically inactive on artificial substrates, but promotes blockade of neuromuscular transmission. Chemical modifications of His, Lys, Tyr, and Trp residues of PrTX-I and PrTX-III were performed, together with cleavage of the N-terminal octapeptide by CNBr and inhibition by heparin and EDTA. The lethality, bactericidal activity, myotoxicity, neuromuscular effect, edema inducing effect, catalytic and anticoagulant activities, and the liposome-disruptive activity of the modified toxins were evaluated. A complex pattern of functional differences between the modified and native toxins was observed. However, in general, chemical modifications that significantly affected the diverse pharmacological effects of the toxins did not influence catalytic or membrane disrupting activities. Analysis of structural changes by circular dichroism spectroscopy demonstrated significant changes in the secondary structure only in the case of N-terminal octapeptide cleavage. These data indicate that PrTX-I and PrTX-III possess regions other than the catalytic site, which determine their toxic and pharmacological activities.

The venom of Bothrops asper from Guatemala: toxic activities and neutralization by antivenoms

Bothrops asper is responsible for approximately half of the snakebite envenomations in Central America. Despite its medical relevance, only the venom of Costa Rican populations of this species has been studied to some detail, and there is very little information on intraspecies variability in venom composition and toxicity. Venom of B. asper from Guatemala was analyzed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and two-dimensional gel electrophoresis, and its basic pharmacological activities were investigated with standard laboratory assays. Venom has lethal, hemorrhagic, myotoxic, edema-forming, coagulant, defibrinating and phospholipase A(2) activities, showing a similar toxicological profile to the one previously described for B. asper from Costa Rica. In addition, polyvalent antivenoms produced in Mexico and Costa Rica, and currently used in Guatemala, were tested for their ability to neutralize venom's toxic activities. Both antivenoms were effective against all effects studied, although the Costa Rican product showed higher potency against most activities tested and higher antibody titer against venom components, as determined by enzyme immunoassay. It is suggested that different dosage regimes should be considered when using these antivenoms in B. asper envenomations in Guatemala.

[Selective intestinal bacterial decontamination in experimental acute pancreatitis]

BACKGROUND

Bacterial translocation implies the transit of viable gastric microflora from the intestinal lumen through the intestinal wall to the mesenteric ganglia and seems to be the mechanism by which microflora reach necrotic tissue in acute pancreatitis (AP). This occurs in 40-70% of necrotizing hemorrhagic AP and plays a major role in up to 80% of deaths from this cause.

AIMS

To analyze the possible influence of bacterial decontamination in the gut on bacterial translocation in severe experimental AP.

METHODS

Severe AP was induced in 43 male Sprague-Dawley rats by administration of 0.2 ml of 2.5% taurodeoxycholate sodium in NaOH glycyl-glycine buffer after cannulizing the bilio-pancreatic duct through the duodenum and clamping the common bile duct in the hepatic junction. The rats were divided into two groups: a) control group: 24 rats in which only AP was induced; b) problem group: 19 rats that underwent bacterial decontamination through the administration of 4 mg/ml gentamicin, bacitracin and neomycin in the drinking water during the 5 days prior to AP induction. Twenty-four hours after AP induction, laparotomy was performed and a sample for the culture of mesenteric lymphatic ganglia, pancreas, liver, spleen, peritoneum and cecum was obtained.

RESULTS

Seven rats in the control group died. Of the 17 rats that survived 24 hours, positive cultures in the pancreas were obtained in nine. In the problem group, two rats died within 24 hours. Of the remaining 17 rats, positive pancreatic cultures were obtained in 2 while in 15 pancreatic cultures were negative. No microflora were cultured in the peritoneum. The microflora most frequently cultivated were Escherichia coli, enterococcus and proteus. No differences were found in the percentage of Gram-positive and Gram-negative bacteria between the two groups.

CONCLUSIONS

a) The majority of the bacteria in AP tissue originate in the intestinal microflora, E. coli being the most prevalent. b) One of the main mechanisms in this process is bacterial translocation via the lymphatic pathway; transit directly through the transperitoneal pathway is not essential. c) Bacterial translocation already occurs in the earlier phases of AP. d) Bacterial decontamination prior to AP decreases the frequency of bacterial translocation and does not interfere in the Gram-positive/Gram negative balance, nor does it increase fungal infections.

Inhibition of local hemorrhage and dermonecrosis induced by Bothrops asper snake venom: effectiveness of early in situ administration of the peptidomimetic metalloproteinase inhibitor batimastat and the chelating agent CaNa2EDTA

The effectiveness of the chelating agent CaNa2EDTA and the peptidomimetic matrix metalloproteinase inhibitor batimastat (BB-94) to inhibit local tissue damage induced by Bothrops asper snake venom was studied in mice. Both compounds totally inhibited proteolytic, hemorrhagic, and dermonecrotic effects, and partially reduced edema-forming activity, when incubated with venom prior to injection. Much lower concentrations of batimastat than of CaNa2EDTA were required to inhibit these effects. In addition, batimastat, but not CaNa2EDTA, partially reduced myotoxic activity of the venom. When the inhibitors were administered at various time intervals after envenomation at the same site of venom injection, both compounds were effective in neutralizing local hemorrhage and dermonecrosis if administered rapidly after venom. Inhibition was not as effective as the time lapse between venom and inhibitor injections increased. Owing to the relevance of metalloproteinases in the pathogenesis of local tissue damage induced by B. asper and other pit viper venoms, it is suggested that administration of peptidomimetic metalloproteinase inhibitors or CaNa2EDTA at the site of venom injection may represent a useful alternative to complement antivenoms in the neutralization of venom-induced local tissue damage.

Neutralization of crotaline snake venoms from Central and South America by antivenoms produced in Brazil and Costa Rica

A study was performed on the ability of antivenoms, produced in Brazil and Costa Rica, to neutralize lethal, hemorrhagic and coagulant activities of the venoms of 16 species of Central and South American snakes of the subfamily Crotalinae. Neutralization of lethality was studied by two different methods routinely used in the quality control of antivenoms at Instituto Butantan (IB) and Instituto Clodomiro Picado (ICP). Both antivenoms neutralized the majority of the venoms studied, but the values of effective doses 50% (ED(50)) differed markedly depending on the method used. In general, higher potencies were obtained with the method of ICP, where a challenge dose corresponding to 4 LD(50)s is used, than with the method of IB, where a challenge dose of 5 LD(50)s is employed. All venoms induced hemorrhagic activity in the mouse skin test, which was effectively neutralized by the two antivenoms. All venoms, except those of Porthidium nasutum and Bothriechis lateralis, induced coagulation of human plasma in vitro and both antivenoms were effective in the neutralization of this activity. In conclusion, our results provide evidence of an extensive cross reactivity between these antivenoms and Central and South American crotaline snake venoms.

Increments in serum cytokine and nitric oxide levels in mice injected with Bothrops asper and Bothrops jararaca snake venoms

Changes in serum levels of several cytokines and nitric oxide were studied in BALB/c mice injected intraperitoneally with one median lethal dose (LD(50)) of the venoms of Bothrops asper and Bothrops jararaca, two of the medically most important poisonous snakes of Latin America. Despite differences observed in the time-course of cytokine increments and in serum cytokine levels, both venoms induced prominent elevations of TNF-alpha, IL-1, IL-6, IL-10 and IFN-gamma. There was an early increase in TNF-alpha and IL-1, followed by a more pronounced increment by 18 h. IL-6 levels peaked between 4 and 6 h, and this cytokine probably modulates the secretion of TNF-alpha and IL-1 and the synthesis of acute-phase proteins. Both venoms induced an early increment in serum IL-10, whereas IFN-gamma levels reached higher values in mice injected with B. jararaca venom than in those receiving B. asper venom. Serum nitric oxide concentration increased in mice injected with both venoms rapidly after envenomation, remaining elevated for 24 h. It is concluded that a complex pattern of cytokine and nitric oxide synthesis and secretion occurs in severe experimental envenomation by B. asper and B. jararaca venoms. Furthermore, it is suggested that some of these mediators, particularly TNF-alpha, IL-1 and nitric oxide, might play a relevant role in the pathophysiology of systemic alterations induced by these venoms.

Effects of aqueous extract of Casearia sylvestris (Flacourtiaceae) on actions of snake and bee venoms and on activity of phospholipases A2

The crude aqueous extract from the leaves of Casearia sylvestris, a plant found in Brazilian open pastures, was assayed for its ability to inhibit phospholipase A2 (PLA2) activity and some biological activities of bee and several snake venoms, and of a number of isolated PLA2s. The extract induced partial inhibition of the PLA2 activity of venoms containing class I, II and III PLA2s. When tested against the purified toxins, it showed the highest efficacy against class II PLA2s from viperid venoms, being relatively ineffective against the class I PLA2 pseudexin. In addition, C. sylvestris extract significantly inhibited the myotoxic activity of four Bothrops crude venoms and nine purified myotoxic PLA2s, including Lys-49 and Asp-49 variants. The extract was able to inhibit the anticoagulant activity of several isolated PLA2s, with the exception of pseudexin. Moreover, it partially reduced the edema-inducing activity of B. moojeni and B. jararacussu venoms, as well as of myotoxins MjTX-II and BthTX-I. The extract also prolonged the survival time of mice injected with lethal doses of several snake venoms and neutralized the lethal effect induced by several purified PLA2 myotoxins. It is concluded that C. sylvestris constitutes a rich source of PLA2 inhibitors.

Snake venom metalloproteinases: their role in the pathogenesis of local tissue damage

The biochemical characteristics of hemorrhagic metalloproteinases isolated from snake venoms are reviewed, together with their role in the pathogenesis of the local tissue damage characteristic of crotaline and viperine snake envenomations. Venom metalloproteinases differ in their domain structure. Some enzymes comprise only the metalloproteinase domain, others have disintegrin-like and high cysteine domains and others present, besides these domains, an additional lectin-like subunit. All of them are zinc-dependent enzymes with highly similar zinc binding environments. Some metalloproteinases induce hemorrhage by directly affecting mostly capillary blood vessels. It is suggested that hemorrhagic enzymes cleave, in a highly selective fashion, key peptide bonds of basement membrane components, thereby affecting the interaction between basement membrane and endothelial cells. As a consequence, these cells undergo a series of morphological and functional alterations in vivo, probably associated with biophysical hemodynamic factors such as tangential fluid shear stress. Eventually, gaps are formed in endothelial cells through which extravasation occurs. In addition to hemorrhage, venom metalloproteinases induce skeletal muscle damage, myonecrosis, which seems to be secondary to the ischemia that ensues in muscle tissue as a consequence of bleeding and reduced perfusion. Microvessel disruption by metalloproteinases also impairs skeletal muscle regeneration, being therefore responsible of fibrosis and permanent tissue loss after snakebites. Moreover, venom metalloproteinases participate in the degradation of extracellular matrix components and play a relevant role in the prominent local inflammatory response that characterizes snakebite envenomations, since they induce edema, activate endogenous matrix metalloproteinases (MMPs) and are capable of releasing TNF-alpha from its membrane-bound precursor. Owing to their protagonic role in the pathogenesis of local tissue damage, snake venom metalloproteinases constitute relevant targets for natural and synthetic inhibitors which may complement antivenoms in the neutralization of these effects.

Myotoxic phospholipases A(2) in bothrops snake venoms: effect of chemical modifications on the enzymatic and pharmacological properties of bothropstoxins from Bothrops jararacussu

Venoms from eight Bothrops spp. were fractionated by ion-exchange chromatography on CM-Sepharose at pH 8.0 for the purification of myotoxins. Chromatographic profiles showed differences regarding myotoxic components among these venoms. B. alternatus, B. atrox and B. jararaca venoms did not show the major basic myotoxic fractions identified in the other venoms. Polyacrylamide gel electrophoresis for basic proteins also showed distinct patterns for these toxins. In vivo, all the isolated myotoxins induced release of creatine kinase due to necrosis of muscle fibers, accompanied by polymorphonuclear cell infiltration, and edema in the mouse paw. In addition, the toxins showed cytotoxic and liposome-disrupting activities in vitro. B. jararacussu bothropstoxins-I (BthTX-I) and II (BthTX-II) were submitted to chemical modifications of: His, by 4-bromophenacyl bromide (BPB) or photooxidation by Rose Bengal (RB); Tyr, by 2-nitrobenzenesulphonyl fluoride (NBSF); and Trp, by o-nitrophenylsulphenyl chloride (NPSC). The myotoxic and cytotoxic activities of BthTX-I, a Lys49 PLA(2) homologue, after modification by BPB, RB, NBSF and NPSC, were reduced to 50%, 20%, 75%, 65% and 13%, 0.5%, 76%, 58%, respectively. However, the edema-inducing and liposome-disrupting activities were not significantly reduced by the above modifications. BPB-treated BthTX-II, an Asp49 PLA(2) homologue, lost most of its catalytic, indirect hemolytic, anticoagulant, myotoxic and cytotoxic activities. The edema-inducing and liposome-disrupting activities were reduced to 50% and 80%, respectively. Lethality caused by BthTX-I and -II was strongly reduced after treatment with BPB or RB, but only partially with NBSF or NPSC. BthTX-I and -II, both native or modified, migrated similarly in a charge-shift electrophoresis. Antibodies raised against BthTX-I or -II, B. asper Basp-II and the C-terminal 115-129 peptide from Basp-II did not show significant differences in their cross-reactivity with the modified toxins, except with RB photooxidized toxins.

Identification of residues critical for toxicity in Clostridium perfringens phospholipase C, the key toxin in gas gangrene

Clostridium perfringens phospholipase C (PLC), also called alpha-toxin, is the major virulence factor in the pathogenesis of gas gangrene. The toxic activities of genetically engineered alpha-toxin variants harboring single amino-acid substitutions in three loops of its C-terminal domain were studied. The substitutions were made in aspartic acid residues which bind calcium, and tyrosine residues of the putative membrane-interacting region. The variants D269N and D336N had less than 20% of the hemolytic activity and displayed a cytotoxic potency 103-fold lower than that of the wild-type toxin. The variants in which Tyr275, Tyr307, and Tyr331 were substituted by Asn, Phe, or Leu had 11-73% of the hemolytic activity and exhibited a cytotoxic potency 102- to 105-fold lower than that of the wild-type toxin. The results demonstrated that the sphingomyelinase activity and the C-terminal domain are required for myotoxicity in vivo and that the variants D269N, D336N, Y275N, Y307F, and Y331L had less than 12% of the myotoxic activity displayed by the wild-type toxin. This work therefore identifies residues critical for the toxic activities of C. perfringens PLC and provides new insights toward understanding the mechanism of action of this toxin at a molecular level.