Comparación de una secuencia en 3D con eco de gradiente potenciada en T1 con 3 factores de reducción de imagen en paralelo diferentes, en apnea y respiración libre, utilizando una bobina de 32 canales a 1,5T. Estudio preliminar / A comparison of a T1 weighted 3D gradient-echo sequence with three different parallel imaging reduction factors, breath hold and free breathing, using a 32 channel coil at 1.5T. A preliminary study

Objetivo. Analizar si el aumento de la resolución temporal utilizando mayores factores de reducción (FR) de imagen en paralelo (IP), tanto en apnea como con respiración libre, utilizando una secuencia 3D con eco de gradiente (EG) potenciada en T1, sin contraste y una bobina de múltiples elementos (phased array) de 32 canales, proporciona una calidad de imagen diagnóstica, con posibilidad de ser aplicada en pacientes que no puedan cooperar para mantener la apnea. Material y métodos. Se incluyeron en el estudio 9 sujetos sanos (5 mujeres y 4 varones; rango de edad: 20-49; media: 36 años). Se les realizó un estudio de RM abdominal con secuencias 3D EG en un equipo de 1,5T con bobina de múltiples elementos (phased-array) de 32 canales con FR de imagen en paralelo de 2, 4 y 6, en apnea y con respiración libre. Dos revisores evaluaron retrospectiva y cualitativamente la calidad de imagen de las secuencias, la magnitud de los artefactos, incluyendo los artefactos de movimiento por reducción de señales, de solapamiento (aliasing), de granulado de los píxeles y la heterogeneidad de la señal. Los resultados se compararon mediante la prueba de Wilcoxon de los rangos con signo y la corrección de Bonferroni para comparaciones múltiples. Resultados. La adquisición en apnea proporcionó mejor calidad de imagen y menos artefactos que la adquisición con respiración libre. La tasa de artefactos fue mayor para FR más altos. La mejor calidad se obtuvo con secuencias en apnea con un FR = 2. Un FR = 4 presentó tasas menores pero diagnósticas (p = 0,004). La severidad de los artefactos, en especial el granulado de los píxeles (p = 0,004), hizo que las secuencias con un FR = 6 no fueran diagnósticas. Ninguna de las secuencias obtenidas con respiración libre fue diagnóstica. Conclusión. Las secuencias obtenidas en apnea con un FR = 2 presentaron una calidad de imagen excelente, y aquellas con un FR = 4 presentaron una calidad buena y potencialmente se pueden aplicar en pacientes poco colaboradores. Ninguna de las secuencias obtenidas con respiración libre se consideró diagnóstica (AU)

Purpose. To investigate whether increasing temporal resolution with higher parallel imaging (PI) reduction factors (RF) in both breath-hold and free breathing approaches, using a non-contrast T1-weighted 3D gradient echo (GRE) sequence and a 32-channel phased array coil, permits diagnostic image quality, with potential application in patients unable to cooperate with breath-hold requirements. Materials and methods. The 9 healthy subjects (5 females and 4 males; age range was 20-49, mean 36 yrs) were recruited. A 3D GRE MR imaging of the abdomen was performed on 1.5T MR system using a 32-element phased-array torso coil with PI RFs of 2, 4 and 6, breath hold and free breathing. Two reviewers retrospectively qualitatively evaluated all sequences for image quality, extent of artifacts, including motion, truncation, aliasing, pixel graininess and signal heterogeneity. The results were compared using Wilcoxon signed rank and a Bonferroni adjustment was applied for multiple comparisons. Results. Image quality and extent of artifacts were better with breath hold than with free breathing acquisitions. The rate of artifacts increased with higher RF. The best quality was acquired with breath hold sequence using RF=2. RF=4 had lower but diagnostic rates (P=.004). The severity of artifacts, mainly pixel graininess (P=.004), rendered sequences with RF=6 non-diagnostic. All sequences were non-diagnostic in free breathing acquisitions. Conclusion. Breath hold sequences with RF=2 had excellent quality and RF=4 had good quality and may be potentially used in partially cooperative patients. None of the sequences was considered diagnostic in free breathing acquisitions (AU)

Secuencia de disparo único eco de gradiente en fase y fase opuesta con preparación de la magnetización: descripción y optimización de la técnica con equipo de 1, 5 T / In-phase and out-of-phase single-shot magnetization-prepared gradient recalled echo: description and optimization of technique at 1.5T

Objetivo: Implementar técnicas en fase y en fase opuesta (EF/FO) con eco de gradiente con preparación de la magnetización (Magnetization-Prepared Gradient Recalled Echo [MP-GRE]) y evaluar la viabilidad y la calidad de imagen diagnóstica entre las secuencias MP-GRE antes y después de la optimización, incluyendo aquellos pacientes que no pueden colaborar manteniendo la apnea. Material y métodos: Para la realización del presente estudio retrospectivo, llevado a cabo de conformidad con la ley HIPPA de protección de datos médicos de EE.UU., se obtuvo la aprobación del Comité de Ética Institucional con exención de obtención del consentimiento informado. Se incluyeron 2 grupos de pacientes en el estudio, antes y después de la optimización de los parámetros MP-GRE, con 73 (24 no colaboradores/49 colaboradores) y 64 (22 no colaboradores/42 colaboradores) pacientes consecutivos, respectivamente. La secuencia no sensible al movimiento usada en este estudio fue 2D MP-GRE con técnica de disparo único. Dos radiólogos evaluaron cualitativamente las secuencias para identificar la presencia de artefactos de cancelación de fase en las imágenes en FO y para determinar la calidad de imagen, la extensión de los artefactos (artefacto de fantasma, artefacto de cancelación de señal, error de registro espacial y granulado de los píxeles) y la visibilidad de las lesiones en las diferentes secuencias. También se evaluó la capacidad para detectar visualmente esteatosis hepática y adenomas suprarrenales de contenido graso. Los análisis cualitativos se compararon mediante las pruebas de Wilcoxon y Mann-Whitney. Resultados: Hubo diferencias estadísticamente significativas entre todas las secuencias MP-GRE en lo relativo al artefacto de cancelación de fase (p < 0,0001), presente en las secuencias MP-GRE FO y despreciable o ausente en las secuencias MP-GRE EF, tanto antes (EF1) como después (EF2) de la optimización, en todos los pacientes. Los artefactos de cancelación de señal fueron significativamente más marcados en las secuencias in MP-GRE EF1 (p < 0,0001). El error de registro espacial fue ligeramente más marcado en las secuencias MP-GRE EF2 (p = 0,0027) en los pacientes no colaboradores. Las secuencias MP-GRE en FO y las secuencias MP-GRE EF2 mostraron una calidad de imagen significativamente mayor (p < 0,0001).En las secuencias MP-GRE se identificaron subjetivamente la esteatosis hepática (n = 20) y los adenomas suprarrenales (n = 5) basándose en la pérdida de señal desde la secuencia EF a la secuencia en FO. Conclusión: La técnica de disparo único MP-GRE EF/FO es una técnica viable que permite la obtención de imágenes resistentes al movimiento, ofreciendo una calidad de imagen diagnóstica adecuada. Esta técnica puede proporcionar información EF y en FO de pacientes que no son capaces de mantener la apnea (AU)

Purpose: To implement in-phase and out-of-phase (IP/OP) techniques with Magnetization-Prepared Gradient Recalled Echo (MP-GRE) and to evaluate the feasibility and diagnostic image quality among pre and post-optimized MP-GRE sequences, including patients unable to cooperate with breath-hold requirements. Materials and methods: Institutional review board approval with waiver of informed consent was obtained for this HIPAA-compliant retrospective study. Two groups of patients were included in the study, before and after optimization of MP-GRE parameters, with seventy-three (24 noncooperative/49 cooperative) and sixty-four (22 noncooperative/42 cooperative) consecutive patients, respectively. The motion-insensitive sequence used in this study was a single-shot 2D MP-GRE. Two radiologists qualitatively evaluated the sequences to identify the presence of phase cancellation artifact in OP images and to determine image quality, extent of artifacts (respiratory ghosting, bounce-point artifact, spatial misregistration and pixel graininess) and lesion conspicuity on the various sequences. The ability to visually detect liver steatosis and fatty adrenal adenomas was evaluated. Qualitative analyses were compared using the Wilcoxon and Mann-Whitney tests. Results: There were statistically significant differences between all MP-GRE sequences concerning phase cancellation artifact (P<.0001) which was present in MP-GRE OP sequences and negligible to absent in the pre (IP1) and post-optimized (IP2) MP-GRE IP sequences, respectively, in all patients. Bounce point artifacts were significantly more pronounced in MP-GRE IP1 (P<0.0001). Spatial misregistration was slightly more prominent in noncooperative patients with MP-GRE IP2 (P=0.0027). MP-GRE OP and MP-GRE IP2 showed significantly higher overall image quality (P<0.0001).MP-GRE sequences subjectively identified hepatic steatosis (n=20) and adrenal adenomas (n=5) based on signal loss from IP to OP sequence. Conclusion: Single shot IP/OP MP-GRE is feasible and allows motion resistant imaging with adequate diagnostic image quality. This technique is able to provide IP and OP information in patients unable to suspend respiration (AU)

A comparison of a T1 weighted 3D gradient-echo sequence with three different parallel imaging reduction factors, breath hold and free breathing, using a 32 channel coil at 1.5 T. A preliminary study.

PURPOSE: To investigate whether increasing temporal resolution with higher parallel imaging (PI) reduction factors (RF) in both breath-hold and free breathing approaches, using a non-contrast T1-weighted 3D gradient echo (GRE) sequence and a 32-channel phased array coil, permits diagnostic image quality, with potential application in patients unable to cooperate with breath-hold requirements. MATERIALS AND METHODS: The 9 healthy subjects (5 females and 4 males; age range was 20-49, mean 36 yrs) were recruited. A 3D GRE MR imaging of the abdomen was performed on 1.5 T MR system using a 32-element phased-array torso coil with PI RFs of 2, 4 and 6, breath hold and free breathing. Two reviewers retrospectively qualitatively evaluated all sequences for image quality, extent of artifacts, including motion, truncation, aliasing, pixel graininess and signal heterogeneity. The results were compared using Wilcoxon signed rank and a Bonferroni adjustment was applied for multiple comparisons. RESULTS: Image quality and extent of artifacts were better with breath hold than with free breathing acquisitions. The rate of artifacts increased with higher RF. The best quality was acquired with breath hold sequence using RF=2. RF=4 had lower but diagnostic rates (P=.004). The severity of artifacts, mainly pixel graininess (P=.004), rendered sequences with RF=6 non-diagnostic. All sequences were non-diagnostic in free breathing acquisitions. CONCLUSION: Breath hold sequences with RF=2 had excellent quality and RF=4 had good quality and may be potentially used in partially cooperative patients. None of the sequences was considered diagnostic in free breathing acquisitions.

[In-phase and out-of-phase single-shot magnetization-prepared gradient recalled echo: description and optimization of technique at 1.5 T]. / Secuencia de disparo único eco de gradiente en fase y fase opuesta con preparación de la magnetización: descripción y optimización de la técnica con equipo de 1,5 T.

PURPOSE: To implement in-phase and out-of-phase (IP/OP) techniques with Magnetization-Prepared Gradient Recalled Echo (MP-GRE) and to evaluate the feasibility and diagnostic image quality among pre and post-optimized MP-GRE sequences, including patients unable to cooperate with breath-hold requirements. MATERIALS AND METHODS: Institutional review board approval with waiver of informed consent was obtained for this HIPAA-compliant retrospective study. Two groups of patients were included in the study, before and after optimization of MP-GRE parameters, with seventy-three (24 noncooperative/49 cooperative) and sixty-four (22 noncooperative/42 cooperative) consecutive patients, respectively. The motion-insensitive sequence used in this study was a single-shot 2D MP-GRE. Two radiologists qualitatively evaluated the sequences to identify the presence of phase cancellation artifact in OP images and to determine image quality, extent of artifacts (respiratory ghosting, bounce-point artifact, spatial misregistration and pixel graininess) and lesion conspicuity on the various sequences. The ability to visually detect liver steatosis and fatty adrenal adenomas was evaluated. Qualitative analyses were compared using the Wilcoxon and Mann-Whitney tests. RESULTS: There were statistically significant differences between all MP-GRE sequences concerning phase cancellation artifact (P<.0001) which was present in MP-GRE OP sequences and negligible to absent in the pre (IP1) and post-optimized (IP2) MP-GRE IP sequences, respectively, in all patients. Bounce point artifacts were significantly more pronounced in MP-GRE IP1 (P<.0001). Spatial misregistration was slightly more prominent in noncooperative patients with MP-GRE IP2 (P=.0027). MP-GRE OP and MP-GRE IP2 showed significantly higher overall image quality (P<.0001). MP-GRE sequences subjectively identified hepatic steatosis (n=20) and adrenal adenomas (n=5) based on signal loss from IP to OP sequence. CONCLUSION: Single shot IP/OP MP-GRE is feasible and allows motion resistant imaging with adequate diagnostic image quality. This technique is able to provide IP and OP information in patients unable to suspend respiration.

Disfunción eréctil en portadores de diabetes mellitus tipo 2 en edad productiva / Erectile dysfunction among diabetic patients

Background: Diabetic microangiopathy is one of the main causes of erectile dysfunction. Aim: To study the prevalence of erectile dysfunction among diabetic patients. Material and Methods: The "international index of erectile function" survey was applied to 120 diabetic men aged 21 to 50years. Demographic data, evolution time of diabetes, a glycosilated hemoglobin measured in the last three months, weight, height and treatment received were also recorded. Results: Fifty five percent of patients had erectile dysfunction. Patients with an inadequate metabolic control had a significantly higher risk of having this condition (odds ratio 5.5; 95% confidence intervals 2.3-81). Conclusions: Erectile dysfunction is common among diabetic patients and closely associated with an inadequate metabolic control.

[Erectile dysfunction among diabetic patients]. / Disfunción eréctil en portadores de diabetes mellitus tipo 2 en edad productiva.

BACKGROUND: Diabetic microangiopathy is one of the main causes of erectile dysfunction. AIM: To study the prevalence of erectile dysfunction among diabetic patients. MATERIAL AND METHODS: The "international index of erectile function" survey was applied to 120 diabetic men aged 21 to 50 years. Demographic data, evolution time of diabetes, a glycosilated hemoglobin measured in the last three months, weight, height and treatment received were also recorded. RESULTS: Fifty five percent of patients had erectile dysfunction. Patients with an inadequate metabolic control had a significantly higher risk of having this condition (odds ratio 5.5; 95% confidence intervals 2.3-81). CONCLUSIONS: Erectile dysfunction is common among diabetic patients and closely associated with an inadequate metabolic control.

Reversible exposure of hydrophobic residues on albumin as a novel strategy for formulation of nanodelivery vehicles for taxanes.

BACKGROUND: We report herein a novel strategy for the preparation of protein-based nanodelivery vehicles for hydrophobic active pharmaceutical ingredients. METHODS: The procedure consisted of three steps, ie, exposure of hydrophobic residues of a protein to a pH-induced partial unfolding: interaction between hydrophobic residues on the protein and the hydrophobic active pharmaceutical ingredient, and a final step where the structure of the protein was reversed to a native-like state by returning to neutral pH. As proof of concept, the interaction of paclitaxel with partially unfolded states of human serum albumin was evaluated as a potential method for the preparation of water-soluble complexes of the taxane with albumin. RESULTS: We found that paclitaxel readily binds to pH-induced partially unfolded albumin, leading to the formation of optically clear water-soluble complexes. The complexes thus formed were more stable in solution when the albumin native state was at least partially restored by neutralization of the solution to a pH around 7. It was also observed that the hydrodynamic radius of human serum albumin was only slightly increased after the cycle of pH changes, remaining in a monomeric state with a size according to paclitaxel binding. Furthermore, paclitaxel binding did not affect the overall exposure of charged groups of human serum albumin, as evaluated by its interaction with an ionic exchange resin. CONCLUSION: The in vitro biological activity of the complexes formed was qualitatively equivalent to that of a Cremophor(®)-based formulation.

Polyisoprene matrix for progesterone release: in vitro and in vivo studies.

Latex, a polyisoprene (PI) hydrophobic elastomer, was evaluated in vitro and in vivo as a matrix for intravaginal steroid hormone delivery. Matrices containing hormone were prepared by swelling latex in chloroform that contained soluble progesterone (P4). In vitro studies demonstrate that P4 release from PI follows a zero order model during at least 100 h and depends on initial load up to 10 mg cm(-2). The release of P4 from a PI matrix was found to be two times faster than from a polydimethylsiloxane (PDMS) matrix. FT-IR and X-ray powder diffraction analysis of P4 polymorphs show that when nucleated in PDMS, the hormone crystallizes only in alpha-form while in latex, crystallizes as a mixture of alpha- and beta-form. In vivo studies show that devices with a PI matrix containing 0.5 g of P4 are effective to reach plasma levels above 1 ng ml(-1) that are needed to synchronize estrous in cattle. Altogether, the results show that PI, a vulcanized polymer with a carbon-carbon backbone, can be used as a new matrix for the intravaginal administration of progesterone with improved release profile than silicone and that the matrix can influence the crystalline state of the hormone.

Room temperature vulcanizing silicone sheaths on a reusable support for progesterone delivery in estrous synchronization treatments in cattle.

High temperature vulcanizing silicone elastomers have been widely used in controlled delivery systems of steroid hormones with the aim of controlling estrous cycle in livestock. This paper reports experiments conducted to evaluate the possibility of using room temperature vulcanizing (RTV) silicone elastomers for the intravaginal administration of progesterone to cattle. In vitro studies showed that RTV silicones and high-temperature vulcanizing silicone release progesterone at a similar rate. Y-shaped inserts made of different polymers were designed as supports of RTV silicone sheaths to test the in vivo release of progesterone. Field evaluation showed that RTV silicone sheaths containing 0.75 g of progesterone were at least as effective at estrous synchronization as commercially available intravaginal inserts.

Evaluación de factores de riesgo en una población con alta prevalencia de estados hipertensivos del embarazo / Risk factors evaluation in a high gestational hypertension prevalence population

Los objtivos furon: determinar la prevalencia de los estados h`pertensivos del embarazo en pacientes aistidas en el Centro Médico OSPECOM de Tucumán y determinar los factores de riesgo más frecuentes asociados

Evaluación de factores de riesgo en una población con alta prevalencia de estados hipertensivos del embarazo / Risk factors evaluation in a high gestational hypertension prevalence population

Los objtivos furon: determinar la prevalencia de los estados h`pertensivos del embarazo en pacientes aistidas en el Centro Médico OSPECOM de Tucumán y determinar los factores de riesgo más frecuentes asociados

American cutaneous leishmaniasis outbreak, Tartagal city, province of Salta, Argentina, 1993.

An American cutaneous leishmaniasis outbreak, with cases clustering during 1993 in Tartagal city, Salta, was reported. The outbreak involved 102 individuals, 43.1% of them with multiple ulcers. Age (mean: 33 years old) and sex distribution of cases (74.5% males), as well as working activity (70 forest-related), support the hypothesis of classical forest transmission leishmaniasis, despite the fact that the place of permanent residence was in periurban Tartagal. Moreover, during July, sandflies were only collected from one of the 'deforestation areas'. Lutzomyia intermedia was the single species of the 491 phlebotomines captured, reinforcing the vector incrimination of this species. Most infections must have been acquired during the fall (April to June), a pattern consistent with previous sandfly population dynamics data. Based on the epidemiological and entomological results, it was advised not to do any vector-targeted periurban control measures during July. Further studies should be done to assess if the high rate of multiple lesions was due to parasite factors or to infective vector density factors.

Characterization of human semen alpha-L-fucosidases.

Human semen contains a large amount of alpha-L-fucosidase activity, the great majority of which is found in the seminal fluid. Immunocytochemical studies indicate that a small amount of semen fucosidase activity is present on the sperm plasma membrane, primarily in the posterior head region. Subcellular fractionation studies also indicate that sperm alpha-L-fucosidase is present in the plasma membrane-enriched fraction. Comparative characterization of human seminal fluid and sperm alpha-L-fucosidases indicates that seminal fluid alpha-L-fucosidase has a broad pH optimum curve with a number of near-equal maxima between pH 4.8 and 7.0 while sperm fucosidase has a major optimum between pH 3.4 and 4.0. Isoelectric focusing indicates that seminal fluid alpha-L-fucosidase contains three to six isoforms with isoelectric points (pI) of 5-7 while sperm fucosidase contains two distinct isoforms with pI values of 5. 2 +/- 0.2 and 7.0 +/- 0.2. Western blotting indicates that seminal fluid fucosidase contains a major protein band with a molecular mass ratio (M(r)) of approximately 56 kDa while sperm fucosidase contains a major protein band of approximately 51 kDa. The overall results indicate the presence of a low-abundance, plasma membrane-associated human sperm alpha-L-fucosidase, which is different in its properties from human seminal fluid alpha-L-fucosidase(s), and whose function is not yet known.

[Study of cases of leishmaniasis in the Province of Salta: evidences of mixed infection with Trypanosoma cruzi and Leishmania spp]. / Estudio de casos de leishmaniasis en la provincia de Salta. Evidencias de infección mixta por trypanosoma cruzi y leishmania spp.

In many regions of South America there are overlapping endemic areas for American Trypanosomiasis (Chagas' disease) and Leishmaniasis. T. cruzi and Leishmania spp, the causative agents of these parasitoses belong to the Trypanosomatidae family and share various antigens that cause cross-reactivity in serological diagnosis when complex antigenic mixtures are used. We studied patients who sought medical attention because of cutaneous or mucocutaneous lesions typical of leishmaniasis infection. These patients were from the province of Salta where Trypanosomiasis and Leishmaniasis are endemic diseases. Sixty-two patients gave a positive Montenegro skin test and, of these, 53 (85, 48%) showed the presence of amastigotes in Giemsa stained smears of dermal scrapings. Seven patients were not included because they were negative for both assays. We analyzed the leishmaniasic sera against homologous antigens to study the immune response and against complex heterologous antigens from T. cruzi to evaluate cross-reactivity phenomena. We also tested these sera against specific antigens for diagnosis of Chagas' disease in order to search for mixed infections. When complex antigens from leishmania were used, the sera showed an unusually strong antibody response 100% positive by IFA, 88.7% by ELISA and 80.6% by immunoblotting. Furthermore, significant cross-reactivity was found when conventional antigens for the serodiagnosis of Chagas' disease were used: 74.19% by IHA, 91.93% by IFA, and 76.80% by ELISA. We have previously purified by immunoaffinity, using a monoclonal antibody, an antigen termed Ag163B6 which is not present in L. mexicana. This antigen has shown the ability to specifically differentiate sera of chronic chagasic patients from those of leishmaniasic patients in ELISA. Furthermore, recent studies from our laboratory by immunoblotting, have demonstrated that chronic chagasic patients exhibit a specific reactivity pattern against T. cruzi epimastigotes that can be distinguished from those presented by leishmaniasic patients in spite of cross-reactive antigens. According to the results obtained in these assays, we classified the patients in two groups: 1) Patients with evidence of T. cruzi infection, those who tested positive in at least one assay: 2) Patients with no evidence of T. cruzi infection who were negative for both assays. More than 50% (32/62) of the patients showed strong evidence of mixed infection with T. cruzi. On the other hand, high cross-reactivity between these two parasitoses was shown in the second group without any evidence of T. cruzi infection since 18 out of 30 were positive in at least two conventional serological reactions. This implies that they would be misdiagnosed as chagasics if conventional reactions were used. These results emphasize the importance of the use of defined antigens and appropriate techniques for the differential diagnosis of these parasitoses, which is more important in areas endemic for both of them.

[Proteolytic, procoagulant activity and electrophoretic characterization of the proteins of 2 toxic extracts of Loxosceles laeta venom]. / Aportes al estudio de las acciones proteolítica, procoagulante y caracterización electroforética de las proteínas de dos extractos tóxicos de veneno de Loxosceles laeta.

Some biochemical properties and proteic components of the brown spider (Loxos celes laeta) venom were studied. The electrophoretic profiles of glandular venom and venom obtained through electrical stimulation were compared using two electrophoretic systems. The first, using a polyacrylamide gel with SDS in tubes, and the second, using an acrylamide gradient on slides. The glandular venom presented 20 and 35 bands respectively, while the venom obtained through electrical stimulation presented 19 and 24 bands. The molecular weight of the proteins detected ranged from 13.5 Kd to 220 Kd. A thermolabil proteolitic activity of casein was detected, and was optimum at pH 9. The effects of the divalent ions, calcium and magnesium, as well as that of chelating agents upon the proteolytic activity of the venom were analyzed. The venom had a procoagulant effect upon citrated human plasma, and was not able to activate the Factor X of the coagulation system in vitro.

Actividad de una 5' nucleotidasa en el veneno de la serpiente Bothrops atrox (L.) "Jergon". / Activity of 5' nucleotidase in the venom of Bothrops atrox (L.) \"Jergon\"

Se ha estudiado las caracteristicas de una 5'nucleotidasa del veneno de Bothrops atrox (L.). La enzima muestra variacion de pH optico en un rango que fluctua entre 6,2 a 8,2 con buffer Tris-HCI y un pico a 8,6 con buffer Glicina-NaOH, mostrando una mayor afinidad con este ultimo.Estos valores de actividad son modificados por accion de magnesio 5 mM. Los iones calcio producen inhibicion de actividad enzimatica en grado variable, mientras que el magnesio es un ion activador, evidenciandose competencia ionica a valores de pH mayores que 8,6. Asi mismo se ha encontrado que la enzima es sensible al efecto termino, a la accion de agentes quelantes como citrato de sodio, EDTA y a L-aminoacidos como: glicina, prolina, ac. glutamico y lisina.En cambio los agentes reductores 2-Mercaptoetanol y L-Cisteina causan notable incremento de la actividad de la enzima a pH 8,6 con buffer Tris-HCl. La adicion de magnesio 5 mM e mezclas de reaccion que contienen L-aminoacidos incrementan la velocidad de hidrolisis