The entrance route: Oral, mucous, cutaneous, or systemic has a marked influence on the outcome of Trypanosoma cruzi experimental infection.

In recent decades, the oral infection of Trypanosoma cruzi has gathered increased attention due to frequent outbreaks that can lead to more severe clinical signs than those usually found in the areas of vector transmission. This study addresses the main routes of infection using metacyclic trypomastigotes (MT) and blood trypomastigotes (BT). Herein, BALB/c mice were infected with the Colombian (TcI) strain via intraperitoneal (IP), oral, intragastric (IG), ocular (OC) and cutaneous (CT) routes with 106 culture-derived MT or BT. Parasitemia was intermittent and low in animals inoculated with MT, in contrast, high parasitemia levels were found in BT-mice. A tropism for the muscles was observed in oral or IG infection with BT. Differently, the parasite was widely distributed in the tissues of mice infected with MT. However, the intensity of the inflammation infiltrating the tissues was higher in oral or IG infection with BT. Animals inoculated with BT via the IG route had similar serum levels of IFN-γ and smaller IL-10 compared to those infected with MT via the IG route. TNF-α levels were higher in the serum from BT-animals, which could explain the higher intensity of heart inflammation in these animals. Our results suggest that the infective form and the route of infection differentially modulated the outcome of Trypanosoma cruzi mice infection.

Echocardiographic Measurements in a Preclinical Model of Chronic Chagasic Cardiomyopathy in Dogs: Validation and Reproducibility.

Background: The failure to translate preclinical results to the clinical setting is the rule, not the exception. One reason that is frequently overlooked is whether the animal model reproduces distinctive features of human disease. Another is the reproducibility of the method used to measure treatment effects in preclinical studies. Left ventricular (LV) function improvement is the most common endpoint in preclinical cardiovascular disease studies, while echocardiography is the most frequently used method to evaluate LV function. In this work, we conducted a robust echocardiographic evaluation of LV size and function in dogs chronically infected by Trypanosoma cruzi. Methods and Results: Echocardiography was performed blindly by two distinct observers in mongrel dogs before and between 6 and 9 months post infection. Parameters analyzed included end-systolic volume (ESV), end-diastolic volume (EDV), ejection fraction (EF), and fractional shortening (FS). We observed a significant LVEF and FS reduction in infected animals compared to controls, with no significant variation in volumes. However, the effect of chronic infection in systolic function was quite variable, with EF ranging from 17 to 66%. Using the cut-off value of EF ≤ 40%, established for dilated cardiomyopathy (DCM) in dogs, only 28% of the infected dogs were affected by the chronic infection. Conclusions: The canine model of CCC mimics human disease, reproducing the percentage of individuals that develop heart failure during the chronic infection. It is thus mandatory to establish inclusion criteria in the experimental design of canine preclinical studies to account for the variable effect that chronic infection has on systolic function.

Parasitaemia and parasitic load are limited targets of the aetiological treatment to control the progression of cardiac fibrosis and chronic cardiomyopathy in Trypanosoma cruzi-infected dogs.

It is still unclear whether the progression of acute to chronic Chagas cardiomyopathy is predominantly associated with the limited efficacy of aetiological chemotherapy, or with the pharmacological resistance profiles and pathogenicity of specific Trypanosoma cruzi strains. Thus, we tested the hypothesis that parasitic load could be a limited target of aetiological chemotherapy to prevent chronic cardiomyopathy in dogs infected by different T. cruzi strains. Animals were infected with benznidazole-susceptible (Berenice-78) and -resistant (VL-10 and AAS) strains of T. cruzi. A quantitative real-time PCR strategy was developed to comparatively quantify the parasite load of the three different strains using a single standard curve. For dogs infected with the VL-10 strain, benznidazole treatment reduced cardiac parasitism during the acute phase of infection. However, similar parasite load and collagen deposition were detected in the myocardium of treated and untreated animals in the chronic phase of the infection. In animals infected with the AAS strain, benznidazole reduced parasite load, myocarditis and type III collagen deposition in the acute phase. However, increased type III collagen deposition was verified in the chronic phase. Dogs infected with the Berenice-78 strain showed a parasitological cure and no evidence of myocardial fibrosis. Parasitic load and cardiac fibrosis presented no correlation in acute or chronic phases of T. cruzi infection. Our findings in a canine model of Chagas disease suggest that parasite burden is a limited predictor for disease progression after treatment and show that benznidazole, although not inducing parasitological cure, is able to prevent total fibrosis in the early stages of infection, as well as complete prevention of cardiac damage when it eliminates parasites at the onset of infection.

Time and dose-dependence evaluation of nitroheterocyclic drugs for improving efficacy following Trypanosoma cruzi infection: A pre-clinical study.

Benznidazole and nifurtimox-treatments regimens currently used in human are supported by very limited experimental data. This study was designed to evaluate the time and dose dependence for efficacy of the most important nitroheterocyclic drugs in use for Chagas disease. In order to evaluate time dependence, Y strain-infected mice received benznidazole for a total of 1, 3, 7, 10, 20, and 40 days. Treatment courses of 3-10-day were effective in clearing parasitaemia and suppressing mortality, but parasitological cure was not achieved. Extending the treatments to 20 or 40 days clearly improved benznidazole efficacy. The 20-day treatment induced cure in 57.1% of Y strain infections (partially drug resistant) but failed to cure Colombian strain infections (full drug resistant), while the 40-day treatment resulted in cure of 100% of Y and 50% of Colombian strain infected mice. The increased cure rates in T. cruzi infected animals that received nifurtimox for 40 days confirm the relationship between the length of treatment and efficacy. An improvement in efficacy was observed with increasing benznidazole doses; cure was verified in 28.6% (75 mg/kg), 57.1% (100 mg/kg) and 80% (300 mg/kg). Overall, these nonclinical study data provide evidence that the efficacy of benznidazole is dose and time dependent. These findings may be relevant for optimizing treatment of human Chagas disease.

Myocarditis in different experimental models infected by Trypanosoma cruzi is correlated with the production of IgG1 isotype.

This study was designed to verify the relationship between IgG antibodies isotypes and myocarditis in Trypanosoma cruzi infection using mice and dogs infected with different T. cruzi strains. The animals were infected with benznidazole-susceptible Berenice-78 and benznidazole-resistant AAS and VL-10 strains. The IgG subtypes were measured in serum samples from dogs (IgG, IgG1, and IgG2) and mice (IgG, IgG1, IgG2a, and IgG2b). The infection of dogs with VL-10 strain induced the highest levels of heart inflammation while intermediate and lower levels were detected with Berenice-78 and AAS strains, respectively. Similar results were found in mice infected with VL-10, but not in those infected with AAS or Berenice-78 strains. The AAS strain induced higher levels of heart inflammation in mice, while Berenice-78 strain was not able to induce it. Correlation analysis between myocarditis and antibody reactivity index revealed very interesting results, mainly for IgG and IgG1, the latter being the most exciting. High IgG1 showed a significant correlation with myocarditis in both experimental models, being more significant in dogs (r=0.94, p<0.0001) than in mice (r=0.58, p=0.047). Overall, our data suggest that IgG1 could be a good marker to demonstrate myocarditis intensity in Chagas disease.

Benznidazole/Itraconazole Combination Treatment Enhances Anti-Trypanosoma cruzi Activity in Experimental Chagas Disease.

The nitroheterocyclic drugs nifurtimox and benznidazole are first-line drugs available to treat Chagas disease; however, they have limitations, including long treatment courses and toxicity. Strategies to overcome these limitations include the identification of new drugs with specific target profiles, re-dosing regimens for the current drugs, drug repositioning and combination therapy. In this work, we evaluated combination therapy as an approach for optimization of the current therapeutic regimen for Chagas disease. The curative action of benznidazole/itraconazole combinations was explored in an established infection of the mice model with the T. cruzi Y strain. The activities of the benznidazole/itraconazole combinations were compared with the results from those receiving the same dosage of each individual drug. The administration of benznidazole/itraconazole in combination eliminated parasites from the blood more efficiently than each drug alone. Here, there was a significant reduction of the number of treatment days (number of doses) necessary to induce parasitemia suppression with the benznidazole/itraconazole combination, as compared to each compound administered alone. These results clearly indicate the enhanced effects of these drugs in combination, particularly at the dose of 75 mg/kg, as the effects observed with the drug combinations were four times more effective than those of each drug used alone. Moreover, benznidazole/itraconazole treatment was shown to prevent or decrease the typical lesions associated with chronic experimental Chagas disease, as illustrated by similar levels of inflammatory cells and fibrosis in the cardiac muscle tissue of healthy and treated mice. These results emphasize the importance of exploring the potential of combination treatments with currently available compounds to specifically treat Chagas disease.

Antitrypanosomal activity of fexinidazole metabolites, potential new drug candidates for Chagas disease.

This study was designed to verify the in vivo efficacy of sulfoxide and sulfone fexinidazole metabolites following oral administration in a murine model of Chagas disease. Female Swiss mice infected with the Y strain of Trypanosoma cruzi were treated orally once per day with each metabolite at doses of 10 to 100 mg/kg of body weight for a period of 20 days. Parasitemia was monitored throughout, and cures were detected by parasitological and PCR assays. The results were compared with those achieved with benznidazole treatment at the same doses. Fexinidazole metabolites were effective in reducing the numbers of circulating parasites and protecting mice against death, compared with untreated mice, but without providing cures at daily doses of 10 and 25 mg/kg. Both metabolites were effective in curing mice at 50 mg/kg/day (30% to 40%) and 100 mg/kg/day (100%). In the benznidazole-treated group, parasitological cure was detected only in animals treated with the higher dose of 100 mg/kg/day (80%). Single-dose pharmacokinetic parameters for each metabolite were obtained from a parallel group of uninfected mice and were used to estimate the profiles following repeated doses. Pharmacokinetic data suggested that biological efficacy most likely resides with the sulfone metabolite (or subsequent reactive metabolites formed following reduction of the nitro group) following administration of either the sulfoxide or the sulfone and that prolonged plasma exposure over the 24-h dosing window is required to achieve high cure rates. Fexinidazole metabolites were effective in treating T. cruzi in a mouse model of acute infection, with cure rates superior to those achieved with either fexinidazole itself or benznidazole.

Myocardial scars correlate with eletrocardiographic changes in chronic Trypanosoma cruzi infection for dogs treated with Benznidazole.

OBJECTIVES: The cardiac form of Chagas disease is evidenced by a progressive cardiac inflammation that leads to myocarditis, fibrosis and electrocardiographic (ECG) conduction abnormalities. Considering these characteristics, the aim of this study was to prospectively evaluate the early ECG changes in dogs that were experimentally inoculated with Benznidazole (Bz)-susceptibly (Berenice-78) and Bz-resistant (VL-10, and AAS) Trypanosoma cruzi strains and, later, evaluate the efficacy of Bz treatment for preventing these ECG alterations. METHODS: Electrocardiographic changes of treated and untreated animals were prospectively evaluated for up to 270 days after infection, at which point collagen (right atrium) quantification was performed. RESULTS: All infected dogs had a high intensity of heart fibrosis (4616.00 ± 1715.82 collagen/74931 µm(2) in dogs infected with Berenice-78 strain, 5839.2 ± 1423.49 collagen/74931 µm(2) in infected by AAS and 6294.40 ± 896.04 collagen/74931 µm(2) in animals infected with VL-10 strain), while 78.57% of all infected dogs showed ECG alterations. Bz Therapy reduced or prevented fibrosis in Bz-susceptible Berenice-78 (2813.00 ± 607.13 collagen/74931 µm(2) ) and Bz-resistant AAS strains (4024 ± 1272.44 collagen/74931 µm(2) ), coincident with only 10% de ECG alterations at 270 days. However, in those animals infected with a Bz-resistant VL-10 strain, specific treatment did not alter collagen deposition (6749.5 ± 1596.35 collagen/74931 µm(2) ) and there was first atrioventricular block and chamber overload at 120 and 270 days after infection, with 75% abnormal ECG exams. CONCLUSIONS: These findings indicate that an effective antiparasitic treatment in the early stage of Chagas disease can lead to a significant reduction in the frequency and severity of the parasite-induced cardiac disease, even if parasites are not completely eliminated.

Fexinidazole: a potential new drug candidate for Chagas disease.

BACKGROUND: New safe and effective treatments for Chagas disease (CD) are urgently needed. Current chemotherapy options for CD have significant limitations, including failure to uniformly achieve parasitological cure or prevent the chronic phase of CD, and safety and tolerability concerns. Fexinidazole, a 2-subsituted 5-nitroimidazole drug candidate rediscovered following extensive compound mining by the Drugs for Neglected Diseases initiative and currently in Phase I clinical study for the treatment of human African trypanosomiasis, was evaluated in experimental models of acute and chronic CD caused by different strains of Trypanosoma cruzi. METHODS AND FINDINGS: We investigated the in vivo activity of fexinidazole against T. cruzi, using mice as hosts. The T. cruzi strains used in the study were previously characterized in murine models as susceptible (CL strain), partially resistant (Y strain), and resistant (Colombian and VL-10 strains) to the drugs currently in clinical use, benznidazole and nifurtimox. Our results demonstrated that fexinidazole was effective in suppressing parasitemia and preventing death in infected animals for all strains tested. In addition, assessment of definitive parasite clearance (cure) through parasitological, PCR, and serological methods showed cure rates of 80.0% against CL and Y strains, 88.9% against VL-10 strain, and 77.8% against Colombian strain among animals treated during acute phase, and 70% (VL-10 strain) in those treated in chronic phase. Benznidazole had a similar effect against susceptible and partially resistant T. cruzi strains. Fexinidazole treatment was also shown to reduce myocarditis in all animals infected with VL-10 or Colombian resistant T. cruzi strains, although parasite eradication was not achieved in all treated animals at the tested doses. CONCLUSIONS: Fexinidazole is an effective oral treatment of acute and chronic experimental CD caused by benznidazole-susceptible, partially resistant, and resistant T. cruzi. These findings illustrate the potential of fexinidazole as a drug candidate for the treatment of human CD.

Marcos legais da propaganda de medicamentos: avanços e retrocessos / Legal frameworks of drug advertisement: progress and setbacks

Desde o início da civilização brasileira,já existe divulgação de produtos farmacêuticos, sendo os medicamentos os preferidos dos anúncios. A propaganda de medicamentos, enquanto estratégia persuasiva, pode representar risco sanitário, caso não se comprometa com a divulgação de informação correta e segura. Nesse sentido, várias são as tentativas de controle sanitário por parte do Estado, as quais parecem consolidar-se em embates de domínio ético e legal. Em busca de compreendero contexto que norteia a atual conjuntura da problemática sobre propaganda de medicamentos, opresente estudo traça um percurso histórico, a partir dos principais marcos legais: a Junta Central de Higiene (1851), a Lei de Vigilância Sanitária (1976) e a criação da AN VISA (1999). Identificou-se que os marcos acompanham o contexto estrutural dopaís, contribuindo para a consolidação do campo da regulação hoje.

Low doses of simvastatin therapy ameliorate cardiac inflammatory remodeling in Trypanosoma cruzi-infected dogs.

Chagas cardiomyopathy remodeling is based on the presence of Trypanosoma cruzi in heart tissue and on the complex inflammatory response leading to a myocardium fibrosis and alterations in conductive and functional heart parameters. This study aims to evaluate Simvastatin on the inflammatory response and heart functionality using dogs infected with Y strain of T. cruzi. Animals were treated daily with Simvastatin (20 mg) for 6 months and submitted to clinical and immunopathological evaluations. Simvastatin reduced heart expression and serum levels of interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) but not interleukin-10 (IL-10), possibly favoring blood parasitism but reducing inflammation and fibrosis in the left ventricle and right atrium. Simvastatin also ameliorated ejection fraction, diastolic diameter, and mass index of the left ventricle 6 months after infection. This study suggests that more investigation should be performed on the use of statins as a prophylactic therapy against cardiac remodeling because of their effects on modifying immune response and benefiting functional parameters in dogs with T. cruzi-induced ventricular dysfunctions.

[Drug advertising to the general public: conceptual parameters of a risk producer practice]. / Propaganda de medicamentos para grande público: parâmetros conceituais de uma prática produtora de risco.

This article analyzes some concepts relating to marketing, advertising, medications, regulation and manipulation. It discusses ethical and health surveillance parameters of drugs advertising for the general public. The focus of this work is the analysis of contradictions from a conceptual point of view between the practice of pharmaceutical advertising as a tool for the increase of sales and the conquest of markets versus the policy of rational use of medicines. Academic studies and monitoring of drugs advertising conducted by the National Health Surveillance Agency show that the contents of the advertising pieces oriented towards the general public overestimate the - sometimes dubious - qualities of their medication, focusing almost exclusively on the benefits and put them in a central position in the therapeutic process. They also fail to mention the risks inherent in their use. Rather than focusing on regulatory proposals aimed at creating constraints to this practice, this article discusses the impossibility, considering the interests of public health, of the coexistence of marketing with the policies for the correct, rational and safe use of drugs.

Propaganda de medicamentos para grande público: parâmetros conceituais de uma prática produtora de risco / Drug advertising to the general public: conceptual parameters of a risk producer practice

Este artigo analisa alguns conceitos relativos a marketing, propaganda, medicamento, regulação e manipulação, discutindo parâmetros éticos e de vigilância sanitária relativos à prática da propaganda de medicamentos para o grande público. O foco deste trabalho é a análise das contradições, desde o ponto de vista conceitual, da prática da propaganda farmacêutica como instrumento de elevação das vendas e conquista de mercados versus a política de uso racional de medicamentos. Estudos acadêmicos e a monitoração da propaganda farmacêutica realizada pela Agência Nacional de Vigilância Sanitária demonstram que os conteúdos das peças publicitárias de medicamentos direcionadas ao grande público superestimam as qualidades do produto, enaltecem quase exclusivamente seus benefícios, colocando-os em uma posição central no processo terapêutico; e omitem os riscos inerentes à sua utilização e exageram suas qualidades, às vezes duvidosas. Mais que se debruçar sobre propostas reguladoras que objetivariam criar constrangimentos a esta prática, este artigo discute a impossibilidade, considerando-se os interesses da saúde pública, da convivência de interesses tão díspares quanto os do marketing - que busca sempre expandir mercados - e das políticas de uso correto, racional e seguro de medicamentos.

This article analyzes some concepts relating to marketing, advertising, medications, regulation and manipulation. It discusses ethical and health surveillance parameters of drugs advertising for the general public. The focus of this work is the analysis of contradictions from a conceptual point of view between the practice of pharmaceutical advertising as a tool for the increase of sales and the conquest of markets versus the policy of rational use of medicines. Academic studies and monitoring of drugs advertising conducted by the National Health Surveillance Agency show that the contents of the advertising pieces oriented towards the general public overestimate the - sometimes dubious - qualities of their medication, focusing almost exclusively on the benefits and put them in a central position in the therapeutic process. They also fail to mention the risks inherent in their use. Rather than focusing on regulatory proposals aimed at creating constraints to this practice, this article discusses the impossibility, considering the interests of public health, of the coexistence of marketing with the policies for the correct, rational and safe use of drugs.

Medication advertising in Brazil. Can it be regulated?

The regulation of medication advertising in Brazil has four weak points. Inspection and punishment of irregularities is carried out a posteriori to the infraction being committed (when the population has already been exposed to a sanitary risk). The fines charged by the Brazilian Sanitary Surveillance Agency (Anvisa) have a derisory value compared to investments in advertising. There is no mechanism that prevents fines from being transferred to prices. The phrase 'If symptoms persist, consult your doctor', rather than warning about the risks of self-medication, encourages using at least the first medication without a prescription, advising a visit to the doctor only if symptoms persist. Anvisa data and academic studies reveal that 90% to 100% of advertising shown in the media contains irregularities. Thus, the Anvisa Collegiate Board of Directors Resolution 102/2000, which seeks to regulate the sector, makes up a system that benefits the infractor and keeps the population at risk. This work analyses alternative regulation, looking at advertising's previous compliance statute through the surveillance system; it studies international statutes and proposes an alteration in the structure of the current model, inserting the logic of sanitary risk prevention.

Propaganda de medicamentos no Brasil: é possível regular? / Medication advertising in Brazil: can it be regulated?

The regulation of medication advertising in Brazil has four weak points. Inspection and punishment of irregularities is carried out a posteriori to the infraction being committed (when the population has already been exposed to a sanitary risk). The fines charged by the Brazilian Sanitary Surveillance Agency (Anvisa) have a derisory value compared to investments in advertising. There is no mechanism that prevents fines from being transferred to prices. The phrase If symptoms persist, consult your doctor, rather than warning about the risks of self-medication, encourages using at least the first medication without a prescription, advising a visit to the doctor only if symptoms persist. Anvisa data and academic studies reveal that 90 percent to 100 percent of advertising shown in the media contains irregularities. Thus, the Anvisa Collegiate Board of Directors Resolution 102/2000, which seeks to regulate the sector, makes up a system that benefits the infractor and keeps the population at risk. This work analyses alternative regulation, looking at advertising's previous compliance statute through the surveillance system; it studies international statutes and proposes an alteration in the structure of the current model, inserting the logic of sanitary risk prevention.

Assimetria nas relações internacionais, propriedade industrial e medicamentos anti-aids / Asymmetry in international relations, industrial property rights and anti-HIV medication

Este artigo analisa a assimetria nas relações internacionais entre países no que diz respeito ao reconhecimento da propriedade industrial no setor específico da indústria farmacêutica. O foco é o impacto destas relações no acesso a medicamentos anti-retrovirais (ARV), questão de interesse mundial em face da sua relação com o desenvolvimento das nações. A disputa de interesses no campo e o posicionamento de alguns países frente às leis patentárias, ao longo do tempo, apontam um cenário pouco favorável para acesso aos medicamentos anti-aids pelos países que não pertencem ao núcleo do sistema mundial. O sucesso do programa brasileiro de Doenças Sexualmente Transmissíveis (DSTs) e Aids nas negociações dos preços dos ARV, ao contrário, aponta para novas possibilidades de enfrentamento desta realidade. A saída parece ser o fortalecimento interno dos Estados Nacionais e um papel ativo das Agências do Sistema das Nações Unidas na defesa dos interesses humanos coletivos.

This paper analyzes the asymmetry in the international relations as refers to the recognition of industrial property rights in the pharmaceutical industry. It focuses on the impact of such relations upon the access to ARV medication, an issue of worldwide interest due to its connection with the development of the nations. Clashing interests and the position taken by some countries in their patent laws point to a scenario less favorable for the access of peripheral countries to anti-HIV/AIDS medication. On the other hand, it seems that the success of the Brazilian STD/AIDS program in negotiating ARV prices will open new possibilities. The solution may be the internal strengthening of the National States and the active role played by the Agencies of the United Nations System in defense of the collective human interests.

[Asymmetry in international relations, industrial property rights and anti-HIV medication]. / Assimetria nas relações internacionais, propriedade industrial e medicamentos anti-aids.

This paper analyzes the asymmetry in the international relations as refers to the recognition of industrial property rights in the pharmaceutical industry. It focuses on the impact of such relations upon the access to ARV medication, an issue of worldwide interest due to its connection with the development of the nations. Clashing interests and the position taken by some countries in their patent laws point to a scenario less favorable for the access of peripheral countries to anti-HIV/AIDS medication. On the other hand, it seems that the success of the Brazilian STD/AIDS program in negotiating ARV prices will open new possibilities. The solution may be the internal strengthening of the National States and the active role played by the Agencies of the United Nations System in defense of the collective human interests.

Desenvolvimento de um modelo para o biospeckle na análise de sementes de feijão (Phaseolus vulgaris L.) / Development of a model for the biospeckle applied to analise been seed (Phaseolus vulgaris L.)

O biospeckle é uma figura de interferência formada pela reflexão difusa da luz coerente espalhada ao interagir com um objeto que apresenta algum tipo de atividade, biológica ou não. O padrão de interferência se modifica ao longo do tempo devido às estruturas responsáveis pelo espalhamento estarem em atividade. Esse fenômeno tem sido estudado com o intuito de se desenvolver um método rápido e não destrutivo para avaliação de materiais biológicos. A obtenção de um modelo simples que descreva os aspectos essenciais do fenômeno é um importante passo para o domínio da técnica. Neste trabalho é apresentado um modelo para descrever a formação do biospeckle, desenvolvido a partir de hipóteses simples sobre como o tecido biológico difrata a luz coerente e qual o efeito da atividade biológica sobre a difração. Foram comparados os resultados da simulação do modelo com resultados experimentais obtidos de sementes. O modelo reproduz com sucesso algumas das características básicas do padrão dinâmico.

Biospeckle is an interference pattern phenomenon formed by the diffuse reflection of coherent light scattered by any type of activity, biological or not. The interference pattern changes in time due to the movement of the structures that scatter the light. This phenomenon has been studied with the goal of developing a fast and non-destructive method for evaluating biological material. Building a simple model that describes the essential aspects of the phenomenon is an important step towards the development of this technique. In this work is presented a model that describes the formation of the biospeckle, based on simple assumptions about the scattering of coherent light by the biological material and the nature of biological activity. We compare the results provided by the model with experimental biospeckle obtained from seeds. The model reproduces successfully some of the basic characteristics of the dynamical experimental pattern.