Community structures in allelopathic interaction networks: An ecoevolutionary approach.

Evidence is mounting that the race of living organisms for adaptation to the chemicals synthesized by their neighbors may drive community structures. Here, an ecoevolutionary model for community assembly through resource competition, toxin-mediated interactions (allelopathy), and evolutionary branching is investigated. We found that stable communities with increasing biodiversity can emerge at weak allelopathic suppression, but strong chemical warfare drastically impairs diversity. For successive invasion events, the allelopathic interaction networks exhibit, respectively, Gaussian and Weibull degree distributions at weak and strong allelopathy. For the branching process dynamics, degrees scale as power laws truncated by stretched exponentials in both regimes. In addition, allelochemical interactions tend to be arranged in modules with low clustering coefficients and disassortative behavior to ensure community stability. So, in a homogeneous environment, species-rich communities can be assembled only at the context of a weak biochemical warfare between organisms, and even under this regime species interact with only a few others.

Invasion waves in the biochemical warfare between living organisms.

Microorganisms and plants very commonly release toxic secondary chemical compounds (allelochemicals) that inhibit or kill sensitive strains or individuals from their own or other species. In this work we study a model that describes two species interacting through allelopathic suppression and competing for resources. Employing linear stability analysis, the conditions for coexistence or extinction of species in spatially homogeneous systems were determined. We found that the borders between the regimes of bistability, coexistence, and the extinction of the weaker by the stronger competitor, are altered by allelopathic interactions. In addition, traveling wave solutions for one species invasion were obtained considering the spatially explicit nature of the model. Our findings indicate that the minimum speed of the invasion wavefronts depends primarily on the competition coefficients and the parameters characterizing the species' functional responses to their allelochemicals. As a general rule, the species provided with the most effective chemical weapons dominates the population dynamics. Finally, we found a tristability at the coexistence region due to the combination of allelopathy and patchy population distributions in space. So, our model provides a distinct mechanism, independent of social behaviors, that produces such unexpected tristability impossible in classical competition models involving one-to-one individual interactions.

TSST-1, enterotoxin and bacteriocin-like substance production by Staphylococcus aureus isolated from foods / TSST-1, enterotoxinas e substâncias tipo bacteriocina produzidas por Staphylococcus aureus isolados de alimentos

The production of Toxic Shock Syndrome Toxin-1 (TSST-1), enterotoxins and bacteriocin-like substances was evaluated in 95 strains of Staphylococcus aureus recovered from raw bovine milk (n=31) and from food samples involved in staphylococcal food poisoning (n=64). Enterotoxigenicity tests with the membrane over agar associated to optimal sensibility plate assays were performed and showed that 96.77% of strains recovered from milk and 95.31% from food samples produced enterotoxins A, B, C, D or TSST-1. Reference strains S. epidermidis, Bacillus cereus, Listeria monocytogenes, Lactobacillus casei, Pseudomonas aeruginosa, S. aureus, Salmonella Typhimurium, Escherichia coli, Enterococcus faecalis and Bacteroides fragilis were used as indicator bacteria in the antagonistic assays, the first five being sensitive to antagonistic substances. Brain heart infusion agar, in pH values ranging from 5.0 to 7.0 in aerobic atmosphere showed to be the optimum condition for antagonistic activity as evaluated with the best producer strains against the most sensitive indicator bacterium, L. monocytogenes. Sensitivity to enzymes confirmed the proteinaceous nature of these substances. Neither bacteriophage activity nor fatty acids were detected and the antagonistic activity was not due to residual chloroform. Results did not establish a positive correlation between the bacteriocinogenic profile and toxigenicity in the tested S. aureus strains.

Avaliou-se a produção de toxina-1 da síndrome do choque tóxico (TSST-1), enterotoxinas e substâncias antagonistas tipo bacteriocina em 95 amostras de Staphylococcus aureus recuperadas de leite bovino in natura (n=31) e de alimentos envolvidos em surto de intoxicação (n=64). Testes de enterotoxigenicidade pelo método da membrana sobre ágar, associado à técnica da sensibilidade ótima em placa, revelaram que 96,77% das amostras do leite e 95,31% daquelas dos alimentos produziram enterotoxinas estafilocócicas tipos A, B, C, D ou TSST-1. Nos ensaios de antagonismo, foram utilizadas como reveladoras amostras de referência de S. epidermidis, Bacillus cereus, Listeria monocytogenes, Lactobacillus casei, Pseudomonas aeruginosa, S. aureus, Salmonella typhimurium, Escherichia coli, Enterococcus faecalis e Bacteroides fragilis, sendo as cinco primeiras sensíveis às substâncias produzidas. As condições ótimas para a atividade antagonista, avaliadas com as melhores produtoras contra a indicadora mais sensível, L. monocytogenes, foram observadas em aerobiose, em ágar infuso de cérebro-coração, nos valores de pH entre 5,0 e 7,0. A sensibilidade a enzimas confirmou a natureza proteica destas substâncias. Não foram detectadas atividades de bacteriófagos nem de ácidos graxos, e a atividade antagonista não foi devido ao clorofórmio residual. Os resultados não mostraram correlação entre o perfil bacteriocinogênico e a toxigenicidade nas amostras de Staphylococcus testadas.

In vitro and in vivo activities of 1,3,4-thiadiazole-2-arylhydrazone derivatives of megazol against Trypanosoma cruzi.

From a series of 1,3,4-thiadiazole-2-arylhydrazone derivatives of megazol screened in vitro against Trypanosoma cruzi, eight (S1 to S8) were selected for in vivo screening by single-dose oral administration (200 mg/kg of body weight) to infected mice at 5 days postinfection (dpi). Based on significant decreases in both parasitemia levels and mortality rates, S2 and S3 were selected for further assays. Despite having no in vivo effect, S1 was included since it was 2-fold more potent against trypomastigotes than megazol in vitro. Trypomastigotes treated with S1, S2, or S3 showed alterations of the flagellar structure and of the nuclear envelope. When assayed on intracellular amastigotes, the selectivity index (SI) for macrophages was in the range of >27 to >63 and for cardiac cells was >32 for S1 and >48 for megazol. In noninfected mice, S1 did not alter the levels of glutamic oxalacetic transaminase (GOT), glutamate pyruvate transaminase (GPT), or urea. S2 led to an increase in GOT, S3 to increases in GOT and GPT, and megazol to an increase in GOT. Infected mice were treated with each derivative at 50 and 100 mg/kg from dpi 6 to 15: S1 did not interfere with the course of infection or reduce the number of inflammatory foci in the cardiac tissue, S2 led to a significant decrease of parasitemia, and S3 decreased mortality. There was no direct correlation between the in vitro effect on trypomastigotes and amastigotes and the results of the treatment in experimental models, as S1 showed a high potency in vitro while, in two different schemes of in vivo treatment, no decrease of parasitemia or mortality was observed.

Screening filamentous tropical fungi for their nutritional potential as sources of crude proteins, lipids and minerals.

The use of fungal and yeast biomass in foodstuff, either as supplements or as major ingredients in formulations is an area of growing interest for the modern food industry. The aim of this study was to evaluate the nutritional potential of biomasses obtained from filamentous fungi Penicillium sclerotiorum, Penicillium janthinellum, Rhizopus stolonifer and Syncephalastrum racemosum. Biomasses presented 26-37% of total proteins, 1.7-3.5% of lipids and 4.6-9.1% of ashes. The humidity level reached 75-83%. Ashes were screened for minerals contents with a special outcome for S. racemosum biomass that presented 3438 mg/100 g (dw) of magnesium. Fatty acids present in the biomasses were screened and the palmitic (C16:0), estearic (C18:0), elaidic (18:1n9-t), oleic (18:1n9-c), linolelaidic (C18:2n6-t), linoleic (C18:2n6-c) and γ-linolenic (C18:3n6) acids were found to be the most abundant, from a total of 88-90% of identified fatty acids. Overall data indicate that the filamentous fungi studied have good nutritional properties, possessing a combination of good level of proteins, low level of fat, and presence of essential fatty acids, including omega-3 derivatives, along with the presence of Ca, Mg, Zn and Fe.

Leishmanicidal activity of new megazol derivatives.

A series of thirteen new megazol derivatives, designed exploring the molecular hybridization approach between megazol (3) and heterocombretastatins (2), was synthesized. These new compounds were tested for in vitro antiparasitic activity upon axenic amastigotes of Leishmania donovani. Biological results led us to identify a new potent megazol derivative (4g), which presents an IC(50) = 0.081microg/mL, more active tham the reference drug miltefosine (IC(50) = 0.131microg/mL).

[Vestibular evoked myogenic potential findings on multiple sclerosis]. / Hallazgos de potenciales vestibulares miogénicos evocados en la esclerosis múltiple.

INTRODUCTION: Vestibular evoked myogenic potential (VEMP) elicited by acoustic stimulation, has been proposed in the assessment of vestibulospinal pathways. AIM: To research the clinical utility of VEMP on multiple sclerosis (MS). SUBJECTS AND METHODS: Forty-four individuals were evaluated (30 normal state and 14 had MS). The acoustic stimuli were short tone burst (1 kHz, 118 dBNa, rise-fall 1 ms, plateau 2 ms) presented through a supra-aural earphone. The stimulation rate was 5 stimuli per second. RESULTS: All the healthy subjects showed a normal VEMP response. In the MS group, abnormal VEMP was recorded among 92.8% of patients and normal in just one case. The P13-N23 increased of prolongation which was the most frequently alteration (57.1%), followed by absence of response among four (28.5%) cases. CONCLUSION: VEMP was considered a good method of diagnostic support of vestibulospinal tract in cases of MS.

Tratamento da esquistossomose mansoni com praziquantel em duas doses únicas diárias consecutivas / Treatment of schistosomiasis mansoni with praziquantel administered as two consecutive single daily doses

Testar esquema alternativo de tratamento da esquistossomose mansoni, visando incremento da eficácia aliado à redução nos efeitos adversos. Foram tratados com praziquantel, na dose total de 80 mg/kg de peso, 100 pacientes com diagnóstico parasitológico da helmintíase, administrando-se o medicamento em uma dose única diária de 40 mg/kg de peso, por dois dias consecutivos. O controle de cura foi realizado pela execução de, no mínimo, seis exames parasitológicos de fezes, pelos métodos de Hoffman, Pons & Janer e Kato-Katz após o tratamento. Dos 72 pacientes que cumpriram os critérios de cura, obtivemos negatividade nas seis coproscopias em 43 dos pacientes (59,7 por cento). Os efeitos adversos foram verificados com frequência semelhante àquela observada com o uso da droga em dose única, destacando-se a ocorrência de urticária em oito pacientes (8 por cento). Concluímos que a utilização do praziquantel no esquema proposto não mostrou incremento na eficácia, bem como resultou em efeitos adversos semelhantes, em qualidade e frequência, aos observados quando da utilização de doses únicas desse fármaco.

Evaluation of anti-Schistosoma mansoni IgG antibodies in patients with chronic schistosomiasis mansoni before and after specific treatment.

The circumoval precipitin test (COPT), enzyme-linked immunosorbent assay (ELISA) and the immunoblotting anti-adult worm antigen (AWA) and soluble egg antigen (SEA) tests were applied to 17 chronically schistosome-infected patients for the detection of anti-Schistosoma mansoni antibodies before and on four occasions after oxamniquine administration over a period of six months. Compared to a control group, schistosomiasis patients showed high levels of IgG antibodies in AWA and SEA-ELISA. A decrease in IgG levels was observed six months after treatment, although negative reactions were not obtained. Significant decreases in IgG1, IgG3 and, mainly, IgG4, but not anti-SEA IgG2 levels were observed six months after treatment, again without negativity. Analysis of anti-AWA IgG antibodies by immunoblotting before treatment showed a 31 kDa strand in 14 patients (82%) which disappeared in three cases up to six months after treatment; furthermore, anti-SEA IgG antibodies showed the same band in nine patients (53%) before treatment, which disappeared in only four cases up to six months after treatment.

Spinal cord injury and psychological response.

Psychological adjustment and psychopathological morbidity issues during rehabilitation of patients with spinal cord injury, have been documented in international literature. However, most authors are faced with methodological difficulties, and results are contradictory. In this prospective study, the first to be made in the Portuguese population, a sample of 65 patients being treated in a rehabilitation unit during the years of 1993, 1994 and 1995, was obtained. The authors study the type of psychological response, when it does occur, which personality traits point to less suffering, which coping mechanisms are used by the better adjusted patients and the differences between the scores of paraplegic and quadriplegic patients. Two assessments were made. The following assessment instruments were used: an anamnestic data questionnaire, the SCL-90-R (Derogatis, 1983), the EPI (Eysenck & Eysenck, 1984), the Coping Styles Evaluation Scale (Figueira, 1990). The second assessments were carried out with the SCL-90-R only. The findings indicate that psychopathological scores consistent with depression occurred in 60% of patients if we consider any evaluation. Sleep disturbances, suicide ideation and guilt occurred in the same proportion. In 33% of them, we found persistent depressive scores in the two assessments. The authors find a highly significant positive correlation between psychopathology and neuroticism. On the contrary, the extroversion dimensions of EPI seem to be a good prognosis predictive factor as far as the occurrence of psychopathology is concerned. No differences in the psychopathological response were found concerning the paraplegic-quadriplegic situation.

[Determination of HIV protein 24 in feces of Triatoma infestans fed with blood from AIDS patients]. / Pesquisa da proteína 24 do vírus da imunodeficiência humana (HIV) nas fezes de triatomíneos alimentados em pacientes com AIDS.

OBJECTIVE: To verify any possibility of the elimination of p24 in feces of Triatoma infestans, p24 being an antigen and one of the markers of HIV infection. The purpose of the study was the evaluation of any risk of contamination by laboratory staff who work with activities related to this particular insect, and also investigate any mechanism that might thus lead to the dissemination of HIV. METHOD: Triatoma infestans were fed with p24-marked blood from 23 AIDS patients. Twenty-four and 48 hours later, their feces were examined in order to verify the presence of the antigen. The search for p24 was performed by means of the immunoenzymatic technique. RESULT AND CONCLUSION: No protein 24 was detected in any of the samples. In accordance with the applied methodology, the purpose of showing that the elimination of p24 does not occur, was obtained. Were this question approached in other ways different results might reveal new information in terms of risks of HIV dissemination.

[Infection by Clonorchis sinensis in Asian immigrants in Brazil. Treatment with praziquantel]. / Infecção por Clonorchis sinensis em imigrantes asiáticos no Brasil. Tratamento com praziquantel.

Fifteen adult patients with assymptomatic infection due to Clonorchis sinensis, diagnosed by coprological examination, were studied. They all came from Asia (twelve from Taiwan, two from South Korea and one from Hong Kong) and were examined at the Adolfo Lutz Institute and the Department of Infectious Diseases, School of Medicine, University of São Paulo, in São Paulo, Brazil. Six patients were women and nine men. All studied patients were admitted to hospital and treated with praziquantel (60 mg/kg). Previous to treatment and on the 15th, 30th and 60th days after praziquantel administration, patients were submitted to quantitative stool examinations, according to Kato-Katz's technique and to hematological and biochemical serum analysis. After a 60 day follow-up nine patients (60%) were negative for C. sinensis eggs in stools. Those not cured after praziquantel administration (six patients, 40%) revealed a sharp decline in faecal elimination of C. sinensis eggs.

[Treatment of experimental infection by Strongyloides venezuelensis in rats, with the use of injectable ivermectin and levamisole]. / Tratamento da infecção experimental de ratos por Strongyloides venezuelensis, mediante uso da ivermectina e do levamisol injectáveis.

For the therapy of human strongyloidiasis, are necessary effective drugs to eliminate both larvae and adult worm parasitism, which may also be used by parenteral route, to obviate the particular conditions presented by many patients. A study based on the experimental infection by Strongyloides venezuelensis in rats was done, administering injectable ivermectin or levamisole. Both drugs were shown to be active, when used in single doses of 0.2 to 0.5 mg/kg of ivermectin, or 26 mg/kg for levamisole. Ivermectin was slightly more effective as far as larval stage of the infection is concerned, and the same happened for levamisole for the adult worm stage. Promising perspectives are visualized to improve the therapy of patients with serious disseminated infection by Strongyloides stercoralis.