Evaluation of inflammatory biomarkers associated with oxidative stress and histological assessment of magnetic therapy on experimental myopathy in rats.

The effect of pulsed electromagnetic field (PEMF) therapy, also called magnetic therapy, upon inflammatory biomarkers associated with oxidative stress plasma fibrinogen, nitric oxide (NO), L-citrulline, carbonyl groups, and superoxide dismutase (SOD) was evaluated through histological assessment, in rats with experimental myopathy. The groups studied were: (A) control (intact rats that received PEMF sham exposures); (B) rats with myopathy and sacrificed 24 h later; (C) rats with myopathy; (D) rats with myopathy and treated with PEMF; and (E) intact rats treated with PEMF. Groups A, C, D, and E were sacrificed 8 days later. Myopathy was induced by injecting 50 µl of 1% carrageenan λ (type IV) once sub-plantar. Treatment was carried out with PEMF emitting equipment with two flat solenoid disks for 8 consecutive days in groups D and E, at 20 mT and 50 Hz for 30 min/day/rat. The biomarkers were determined by spectrophotometry. The muscles (5/8) were stained with Hematoxylin-Eosin and examined by optic microscopy. Quantitative variables were statistically analyzed by the Fisher test, and categorical applying Pearson's Chi Squared test at p < 0.05 for all cases. In Groups B and C, the biomarkers were significantly increased compared to A, D, and E groups: fibrinogen (p < 0.001); NO, L-citrulline and carbonyl groups (p < 0.05); SOD (p < 0.01) as well as the percentage of area with inflammatory infiltration (p < 0.001). PEMF caused decreased levels of fibrinogen, L-citrulline, NO, SOD, and carbonyl groups and significant muscle recovery in rats with experimental myopathies.

[Clinical experience of treatment with onabotulinumtoxin A in patients with refractory migraine]. / Experiencia clinica del tratamiento con onabotulinumtoxin A en pacientes con migrana refractaria.

AIM: To analyse our experience in the treatment of refractory chronic migraine, episodic frequent refractory migraine (≥10 days/month), with onabotulinumtoxin A (OnabotA). PATIENTS AND METHODS: Retrospective analysis of patients with refractory migraine who underwent, at least two sessions of OnabotA pericranial injections following the PREEMPT protocol between 2008 and 2012. The efficacy of OnabotA was evaluated comparing the basal situation with 12-16 weeks after the second session. We analysed the subjective improvement of the patients, number of days with headache, preventive and abortive drugs consumption, and adverse effects. RESULTS: Forty-one patients (37 women, 4 male) were identified. 65.8% patients experienced subjective improvement after OnabotA treatment. 36.58% responded (reduction of > 50% in headache days). Differences between days with headache before the first session (24.5 ± 7.3), and 12-16 weeks after the second session (17.4 ± 11.6), as well as the differences between the number of abortive drugs taken before the first session (26.8 ± 23.1) and 12-16 weeks after the second session (16.7 ± 19.3), were statistically significant (p < 0.001). Subgroups analysis showed that all differences were significant, except for the reduction of the number of days with headache in patients with episodic frequent refractory migraine. CONCLUSION: Our work shows that treatment with OnabotA is safe and useful in patients with episodic and chronic refractory migraine, including those patients with medication overuse headache.

Experiencia clínica del tratamiento con onabotulinumtoxin A en pacientes con migraña refractaria / Clinical experience of treatment with onabotulinumtoxin A in patients with refractory migraine

Objetivo. Mostrar nuestra experiencia en el tratamiento de onabotulinumtoxin A (OnabotA) en pacientes con migraña refractaria, tanto crónica como episódica frecuente (≥ 10 días/mes). Pacientes y métodos. Análisis retrospectivo de pacientes con migraña refractaria que habían recibido al menos dos infiltraciones de OnabotA siguiendo el protocolo PREEMPT entre los años 2008 y 2012. Se evaluó la eficacia de OnabotA comparando la situación basal y transcurridas entre 12-16 semanas después de la segunda infiltración, determinando: mejoría subjetiva de los pacientes, número de días con cefalea, consumo de fármacos preventivos y analgésicos, y efectos adversos. Resultados. Se identificaron 41 pacientes (37 mujeres, cuatro varones). Un 65,8% de los pacientes encontró mejoría subjetiva tras el tratamiento. Un 36,58% respondió al tratamiento con OnabotA (reducción > 50% en los días de cefalea). La diferencia entre los días al mes de cefalea antes de la primera infiltración (24,5 ± 7,3) y después de la segunda infiltración (17,4 ± 11,6), y la diferencia entre la dosis de analgésicos al mes antes de la primera infiltración (26,8 ± 23,1) y la de después de la segunda infiltración (16,7 ± 19,3) fueron significativas (p < 0,001). En el análisis por subgrupos, todas las diferencias fueron significativas, salvo en el caso de pacientes con migraña episódica frecuente refractaria, donde la reducción en los días al mes de cefalea no alcanzó la significación. Conclusión. El tratamiento con OnabotA es útil en pacientes con migraña refractaria crónica, y podría ser también beneficioso en migraña refractaria episódica frecuente (AU)

Aim. To analyse our experience in the treatment of refractory chronic migraine, episodic frequent refractory migraine (≥ 10 days/month), with onabotulinumtoxin A (OnabotA). Patients and methods. Retrospective analysis of patients with refractory migraine who underwent, at least two sessions of OnabotA pericranial injections following the PREEMPT protocol between 2008 and 2012. The efficacy of OnabotA was evaluated comparing the basal situation with 12-16 weeks after the second session. We analysed the subjective improvement f the patients, number of days with headache, preventive and abortive drugs consumption, and adverse effects. Results. Forty-one patients (37 women, 4 male) were identified. 65.8% patients experienced subjective improvement after OnabotA treatment. 36.58% responded (reduction of > 50% in headache days). Differences between days with headache before the first session (24.5 ± 7.3), and 12-16 weeks after the second session (17.4 ± 11.6), as well as the differences between the number of abortive drugs taken before the first session (26.8 ± 23.1) and 12-16 weeks after the second session (16.7 ± 19.3), were statistically significant (p < 0.001). Subgroups analysis showed that all differences were significant, xcept for the reduction of the number of days with headache in patients with episodic frequent refractory migraine. Conclusion. Our work shows that treatment with OnabotA is safe and useful in patients with episodic and chronic refractory migraine, including those patients with medication overuse headache (AU)

Migraña crónica y abuso de analgésicos / Chronic migraine and abuse of analgesics

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Evaluation of inflammatory biomarkers associated with oxidative stress and histological assessment of low-level laser therapy in experimental myopathy.

UNLABELLED: The objective of the present work was to study the effect of helium-neon (He-Ne) and gallium-arsenide (Ga-As) laser upon inflammatory biomarkers associated with oxidative stress: fibrinogen, nitric oxide (NO), L-citrulline, and superoxide dismutase (SOD). These were evaluated through histological assessment, in rats with experimental myopathy. MATERIALS AND METHODS: The groups studied were: (A) control, (B) injured, (C) injured and treated with He-Ne laser, (D) injured and treated with Ga-As laser, (E) irradiated with He-Ne; and (F) irradiated with Ga-As laser. Myopathy was induced by injecting 0.05 mg/rat/day of adrenaline in the left posterior limb muscle at the same point on 5 consecutive days, in groups B, C, and D. Low-level laser therapy (LLLT) was applied with 9.5 J/cm(2) daily for 7 consecutive days with each laser. The determination of the biomarkers was made by spectrophotometry. The muscles (5/8, single blinded) were stained with Gomori Trichrome and examined by optic microscopy. The quantitative variables were statistically analyzed by the Fisher's test and categorical data by the Axionvision 4.8 program. Pearson's chi-squared test was applied, setting significant difference at P < 0.05 for all cases. RESULTS: In group B, the biomarkers were significantly increased compared to the other groups (P < 0.001), except for NO which in group B decreased significantly (P < 0.001). In group B, there was a higher inflammatory infiltration level (80.67%) in relation to destroyed fibers. CONCLUSIONS: LLLT caused significant changes in inflammatory biomarkers and oxidative stress: decreased levels of fibrinogen, L-citrulline and SOD as opposed to the increase of NO in rats with experimental myopathies and significant muscle recovery.

Studies of membrane fluidity and heart contractile force in Trypanosoma cruzi infected mice

In Chagas disease serious cardiac dysfunction can appear. We specifically studied the cardiac function by evaluating: ventricle contractile force and norepinephrine response, affinity and density of beta-adrenergic receptors, dynamic properties of myocardial membranes, and electrocardiography. Albino swiss mice (n = 250) were infected with 55 trypomastigotes, Tulahuen strain and studied at 35, 75, and 180 days post-infection, that correspond to the acute, indeterminate, and chronic phase respectively. Cardiac beta-adrenergic receptors' affinity, myocardial contractility, and norepinephrine response progressively decreased from the acute to the chronic phase of the disease (p < 0.01). The density (expressed as fmol/mg.prot) of the receptors was similar to non-infected mice (71.96 ± 0.36) in both the acute (78.24 ± 1.67) and indeterminate phases (77.28 ± 0.91), but lower in the chronic disease (53.32 ± 0.71). Electrocardiographic abnormalities began in the acute phase and were found in 65 percent of the infected-mice during the indeterminate and chronic phases. Membrane contents of triglycerides, cholesterol, and anisotropy were similar in all groups. A quadratic correlation between the affinity to beta-adrenergic receptors and cardiac contractile force was obtained. In conclusion the changes in cardiac beta-adrenergic receptors suggests a correlation between the modified beta-adrenergic receptors affinity and the cardiac contractile force.

Laser therapy on arthritis induced by urate crystals.

OBJECTIVE: We aimed to evaluate low-power laser therapy efficacy on fibrinogen (PF) in the plasma of rats with arthritis induced by urate crystals. In addition, anatomopathological (AP) studies were carried out. BACKGROUND DATA: Raised blood uric acid may form microscopic crystals in the joint. These crystals set up the inflammation called "acute gouty arthritis." METHODS: Two mg of uric acid were injected in both joints of the lower limbs of rats over 2 days. A group was treated with He-Ne laser (6 mW) on the injected joints during 3 consecutive days. After 96 h of the first injection, animals were sacrificed to determine fibrinogen by spectrophotometry. Sections from the lower limbs were used for AP studies. RESULTS: A statistically significant increase (p < 0.001) in plasma fibrinogen levels was observed in the group injected with urates, when compared to both control group and the laser-treated group. The AP observed in the untreated group showed an intense fibroblastic proliferation and chronic inflammation. In the group treated with laser no inflammatory reaction was observed. CONCLUSIONS: Laser therapy has an anti-inflammatory effect in arthropathy induced in rats injected with urates, determined by fibrinogen levels and by histological involution.

Studies of membrane fluidity and heart contractile force in Trypanosoma cruzi infected mice.

In Chagas disease serious cardiac dysfunction can appear. We specifically studied the cardiac function by evaluating: ventricle contractile force and norepinephrine response, affinity and density of beta-adrenergic receptors, dynamic properties of myocardial membranes, and electrocardiography. Albino swiss mice (n = 250) were infected with 55 trypomastigotes, Tulahuen strain and studied at 35, 75, and 180 days post-infection, that correspond to the acute, indeterminate, and chronic phase respectively. Cardiac beta-adrenergic receptors' affinity, myocardial contractility, and norepinephrine response progressively decreased from the acute to the chronic phase of the disease (p < 0.01). The density (expressed as fmol/mg.prot) of the receptors was similar to non-infected mice (71.96 +/- 0.36) in both the acute (78.24 +/- 1.67) and indeterminate phases (77.28 +/- 0.91), but lower in the chronic disease (53.32 +/- 0.71). Electrocardiographic abnormalities began in the acute phase and were found in 65% of the infected-mice during the indeterminate and chronic phases. Membrane contents of triglycerides, cholesterol, and anisotropy were similar in all groups. A quadratic correlation between the affinity to beta-adrenergic receptors and cardiac contractile force was obtained. In conclusion the changes in cardiac beta-adrenergic receptors suggests a correlation between the modified beta-adrenergic receptors affinity and the cardiac contractile force.

Trypanosoma cruzi reinfections provoke synergistic effect and cardiac beta-adrenergic receptors' dysfunction in the acute phase of experimental Chagas' disease.

Cardiac beta-adrenergic receptors' function was studied in the acute phase of Chagas' disease in mice reinfected with Trypanosoma cruzi Tulahuen strain (Tul) and with parasites isolated from an infected patient (SGO-Z12). Genetic characterization of SGO-Z12 isolates demonstrated that it belongs to the zimodeme Z12, one of the prevalent ones in humans in Argentina. Electrocardiography, heart histopathology, parasitemias, and survival in infected and reinfected mice were also analyzed. Reinfected mice reached higher parasitemias, 14% of the infected with SGO-Z12 and 76% of the reinfected groups showed electrocardiographic abnormalities. Similar results were found in mice that were infected and reinfected with Tul. SGO-Z12-Reinfected and Tul-Infected groups exhibited cardiac beta-adrenergic receptors' affinity significantly diminished (p<0.001) and its density significantly increased (p<0.001) than in infected and non-infected groups. Histopathologic alterations in hearts from Tul and SGO-Z12-Reinfected mice were detected. Reinfections with T. cruzi, Tulahuen strain or SGO-Z12 isolate provoked cardiac dysfunctions of different degrees, from the acute phase on.

Indeterminate Chagas' disease: Trypanosoma cruzi strain and re-infection are factors involved in the progression of cardiopathy.

Chagas' disease is caused by Trypanosoma cruzi, which is transmitted by reduviid bugs. The World Health Organization has estimated that about 16-18 million people in the Americas are infected, and that more than 100 million are at risk. In the present study we have used a murine model to analyse if particular T. cruzi strains (Tulahuen strain and SGO-Z12 isolate from a chronic patient) and/or re-infection may determine, during the indeterminate phase of experimental Chagas' disease, changes that could explain the different evolution of cardiac lesions. Re-infected mice reached higher parasitaemias than those infected for the first time. The survival in the indeterminate phase of mice infected with Tulahuen strain was 50.0%, while the SGO-Z12-infected group presented a significantly higher survival rate (77.1%; P <0.01). The SGO-Z12-re-infected group showed a survival rate (70.9%) significantly higher than that of the Tulahuen-re-infected group (37.0%; P <0.01). Electrocardiographic abnormalities were found in 66% of Tulahuen-infected mice, while in SGO-Z12-infected group such abnormalities were found in only 36% of animals ( P <0.01). The two groups exhibited similar percentages of electrocardiographic dysfunction on re-infection, although intraventricular blocks were more frequent in Tulahuen-re-infected mice ( P <0.01). Hearts from infected or re-infected mice with either parasite showed mononuclear infiltrates. The SGO-Z12-re-infected and Tulahuen-re-infected groups exhibited a significantly diminished affinity ( P <0.05) and a significantly increased density ( P <0.05) of cardiac beta-adrenergic receptors compared with the infected and non-infected groups. The indeterminate phase of Chagas' disease is defined as a prolonged period that is clinically silent, but the present findings show that different T. cruzi strains and re-infection are able to alter the host-parasite equilibrium, and these factors may be responsible for inducing progressive cardiopathy.

Trypanosoma cruzi reinfections in mice determine the severity of cardiac damage.

In two murine models we studied Trypanosoma cruzi reinfection in the acute and chronic phase of experimental Chagas' disease in order to elucidate the relevance of reinfections in determining the variability of cardiac symptoms and the irreversible cardiac damage. They were followed for 120 and 600 days post infection (p.i.) for the acute and chronic model, respectively. Reinfected mice reached higher parasitaemia levels than infected mice. The survival was 33 and 21% in the chronic phase for mice reinfected in the acute phase and 13% for mice reinfected in the chronic stage at the end of the experiments. Sixty-six percent of the infected group presented electrocardiographic abnormalities (heart frequency, prolonged PQ segment or QRS complex) in the chronic stage whereas 100% of the reinfected animals exhibited electric cardiac dysfunction since 90 and 390 days p.i. for the acute and chronic reinfected model, respectively (P<0.01). Heart histopathological studies showed fibrosis and necrosis areas and mononuclear infiltrates supporting the view that parasite persistence is a major factor in continuing the tissue inflammation. This work shows that T. cruzi reinfections could be related to the variability and severity of the clinical course of Chagas' disease and that parasite persistence is involved in exacerbation of the disease.

Cardiac beta receptors density or affinity modified by different Trypanosoma cruzi amount

Chagasdisease presents complex physiopathogenic mechanism, many of them poorly understood, that in our country generally produce cardiac lesions. The acute phase related with the presence of the parasite is usually asymptomatic. This report studies if the amount of T. cruzi that induced acute infection could modify the myocardiopathy evolution. Previous works have shown that Albino Swiss mice inoculated with 45 tripomastigotes (AcL) presented alterations in the cardiac pharmacological response to adrenergic agonist and anatogonist studied at 30 days post-infection (p.i.). Mice inoculated with 7 x 10(4) parasites/animal showed similar behaviour at 7 days p.i. We studied the involvement of the affinity and density of cardiac beta receptors in both acute groups by binding with (3)H/DHA. The AcH group presented less cardiac beta receptors number (p<0.001), but their affinity was conserved. The AcL model presented significantly less affinity (p<0.01) but desinty, was not different from non infected animals. Beta receptorsaffinity of both infected groups were similar, but AcH density was significantly diminished when compared with AcL. These studies demonstrates that the amount of T. cruzi received by the host determines and acelerates the evolution of the chagasic myocardiopathy. (AU)

Cardiac beta receptors' density or affinity modified by different Trypanosoma cruzi amount

Chagas'disease presents complex physiopathogenic mechanism, many of them poorly understood, that in our country generally produce cardiac lesions. The acute phase related with the presence of the parasite is usually asymptomatic. This report studies if the amount of T. cruzi that induced acute infection could modify the myocardiopathy evolution. Previous works have shown that Albino Swiss mice inoculated with 45 tripomastigotes (AcL) presented alterations in the cardiac pharmacological response to adrenergic agonist and anatogonist studied at 30 days post-infection (p.i.). Mice inoculated with 7 x 10(4) parasites/animal showed similar behaviour at 7 days p.i. We studied the involvement of the affinity and density of cardiac beta receptors in both acute groups by binding with (3)H/DHA. The AcH group presented less cardiac beta receptors number (p<0.001), but their affinity was conserved. The AcL model presented significantly less affinity (p<0.01) but desinty, was not different from non infected animals. Beta receptors'affinity of both infected groups were similar, but AcH density was significantly diminished when compared with AcL. These studies demonstrates that the amount of T. cruzi received by the host determines and acelerates the evolution of the chagasic myocardiopathy.

Cardiac B-receptors in experimental Chagas`disease

Estudaram-se os receptores beta cardiacos de camundongos infectados pelo Trypanosoma cruzi na fase pos-aguda da doenca de Chagas para estabelecer em que medida os mesmos contribuem a gerar respostas anomalas as catecolaminas observadas nestes miocardios. Utilizara-se 3-H/DHA para a marcacao dos receptores beta cardiacos dos camundongos normais e dos infectados na fase pos-aguda (45 a 90 dias pos-infeccao). O numero dos sitios de fixacao foi similar nos dois grupos, 78.591 ñ 3.125 fmol/mg. Proteina no grupo controle. Em vez disso, a afinidade verificou-se significamente diminuida no grupo chagasico (Kd = 7.299 ñ 0.212 nM) p < 0.001. Os resultados obtidos demonstraram que as modificacoes observadas na estimulacao adrenergica do miocardio chagasico se correlacionam com a menor afinidade dos receptores beta cardiacos e que estas alteracoes exerceriam uma parte determinante para as consequencias funcionais que sao detectadas na fase cronica.

Isometric developed tension and histopathology of myocardium of chagasic mice. II

In a preceding paper we reported the evolution of chagasic cardiopathy in mice inoculated with low number of T. cruzi from 2 days to 75 days post-infection (p.i.). The present work analyzed the contractility, pharmacological response and histopathology of myocardium isolated from chronic chagasic mice from 90 days until 180 days. p.i. Myocardium contractile force reached values similar to controls until 165 days p.i. From this to the end contractility was significantly lower. At 90 days p.i. NE provoked negative inotropic effect or had no effect in 13% of the cases tested. The others had a reactivity to NE similar to normal ventricles. From 105 days until 180 days p.i. NE induced to a positive inotropic effect significantly lower than in normal. ACh effect was significantly smaller from 165 days to the end. Previously ACh ventricles responses were as control. The effects of dibenamine, propranolol and atropine (10-6M) on chagasic ventricles were similar to those observed in normal tissues. At 90 days p.i. the histopathology showed focalized inflammatory infiltrates. At 180 days p.i. fibers fragmentations and loss of typical striated characteristic of cardiac tissue. The abnormal pharmacological response described could be attributed to alterations in cardiac beta and muscarinic receptors probably due to a lower oxygen support. The present paper shows that during chronic Chagas disease myocardial function and pharmacological reactivity are seriously and definitively compromised (Au)

Isometric developed tension and histopathology of myocardium of chagasic mice. II

In a preceding paper we reported the evolution of chagasic cardiopathy in mice inoculated with low number of T. cruzi from 2 days to 75 days post-infection (p.i.). The present work analyzed the contractility, pharmacological response and histopathology of myocardium isolated from chronic chagasic mice from 90 days until 180 days. p.i. Myocardium contractile force reached values similar to controls until 165 days p.i. From this to the end contractility was significantly lower. At 90 days p.i. NE provoked negative inotropic effect or had no effect in 13% of the cases tested. The others had a reactivity to NE similar to normal ventricles. From 105 days until 180 days p.i. NE induced to a positive inotropic effect significantly lower than in normal. ACh effect was significantly smaller from 165 days to the end. Previously ACh ventricles responses were as control. The effects of dibenamine, propranolol and atropine (10-6M) on chagasic ventricles were similar to those observed in normal tissues. At 90 days p.i. the histopathology showed focalized inflammatory infiltrates. At 180 days p.i. fibers fragmentations and loss of typical striated characteristic of cardiac tissue. The abnormal pharmacological response described could be attributed to alterations in cardiac beta and muscarinic receptors probably due to a lower oxygen support. The present paper shows that during chronic Chagas' disease myocardial function and pharmacological reactivity are seriously and definitively compromised

Isometric developed tension and histopathology of myocardium of chagasic mice. I

La enfermedad cardíaca es usualmente la complicación más seria de la infección humana por T. cruzi en nuestro país. Este trabajo estudia la evolución de la cardiopatía chagásica en ratones inoculados con bajo número de parásitos en la etapa aguda indeterminada bajo diferentes aspectos: contractilidad, histopatología, respuesta farmacológica. Desde los 2-45 días post-infección (p.i) (etapa aguda) la contractilidad miocárdica alcanzó valores significativamente superiores que los controles, pero la respuesta a la norepinefrina (NE) fue inferior. La acetilcolina (ACh) produjo un efecto inotrópico negativo similar al observado en el grupo control. El daño cardíaco en este período evolucionó a una miocarditis aguda intersticial. En la fase indeterminada de esta parasitosis (45-75 días p.i.) NE produjo menor efecto inotrópico positivo, inotropismo negativo o no tuvo efecto de acuerdo con los distintos días en que se analizaron los ventrículos. La respuesta a ACh fue significativamente menor que la de los controles. En esta etapa se observó fibrosis perivascular subendocárdica y necrosis en la pared de los vasos. La respuesta farmacológica anormal descripta podría deberse a modificaciones en el número o en la afinidad de los receptores miocárdicos beta y muscarínicos. Los presentes resultados muestran que la contractilidad, histopatología y respuesta a la droga del miocardio aislado de ratones infectados con T. cruzi estaban alterados desde las 48 horas p.i., alcanzando un desorden máximo a los 60 días p.i (AU)

Isometric developed tension and histopathology of myocardium of chagasic mice. I

La enfermedad cardíaca es usualmente la complicación más seria de la infección humana por T. cruzi en nuestro país. Este trabajo estudia la evolución de la cardiopatía chagásica en ratones inoculados con bajo número de parásitos en la etapa aguda indeterminada bajo diferentes aspectos: contractilidad, histopatología, respuesta farmacológica. Desde los 2-45 días post-infección (p.i) (etapa aguda) la contractilidad miocárdica alcanzó valores significativamente superiores que los controles, pero la respuesta a la norepinefrina (NE) fue inferior. La acetilcolina (ACh) produjo un efecto inotrópico negativo similar al observado en el grupo control. El daño cardíaco en este período evolucionó a una miocarditis aguda intersticial. En la fase indeterminada de esta parasitosis (45-75 días p.i.) NE produjo menor efecto inotrópico positivo, inotropismo negativo o no tuvo efecto de acuerdo con los distintos días en que se analizaron los ventrículos. La respuesta a ACh fue significativamente menor que la de los controles. En esta etapa se observó fibrosis perivascular subendocárdica y necrosis en la pared de los vasos. La respuesta farmacológica anormal descripta podría deberse a modificaciones en el número o en la afinidad de los receptores miocárdicos beta y muscarínicos. Los presentes resultados muestran que la contractilidad, histopatología y respuesta a la droga del miocardio aislado de ratones infectados con T. cruzi estaban alterados desde las 48 horas p.i., alcanzando un desorden máximo a los 60 días p.i