Ultrastructural Changes of Caudate Nucleus in Mice Chronically Treated with Manganese.

Manganese (Mn) is able to cross the blood-brain barrier and induces functional and structural alterations during the intoxication by this metal. Therefore, the effects of chronic administration of Mn in the caudate nucleus of mice were evaluated by electron microscopy. Male albino mice were injected intraperitoneally with MnCl2 (5 mg/kg/d) 5 d per week during 9 weeks. The control group received only 0.9% of NaCl solution. The caudate nuclei were extracted and subsequently processed to be observed on a conventional transmission electron microscope at 2, 4, 6, and 9 weeks after treatment. A high percentage of vacuolated and swollen mitochondria were found throughout all the analyzed periods. Myelin disarrangement and ultrastructural alterations related to edema were observed increased in Mn-treated mice at week 9. Granular degeneration of myelin at week 9 accompanied with deposition of electron dense granules in the neuropil was also observed. Edema in neuropil and glial cells was detected from week 2 to week 9 accompanied by swollen mitochondria. Neuronal bodies, synaptic terminals, and perivascular cells were found swollen. Decreased electron density in postsynaptic areas and decreased and dispersed synaptic vesicles in presynaptic areas were noted in Mn-treated animals. Some neurons from Mn-treated mice showed cisternae dilation of the Golgi apparatus. These results suggest that Mn-treatment produces structural alterations in the caudate nucleus that could be responsible for some of the neurotoxic effects of this metal.

Longterm melatonin administration alleviates paraquat mediated oxidative stress in Drosophila melanogaster / La administración de melatonina a largo plazo mitiga el estrés oxidativo mediado por paraquat en Drosophila melanogaster

We investigated the effect of melatonin (MEL) in the activities of cytosolic superoxide dismutase (SOD) and catalase as well as in the levels of H2O2 and mitochondrial malondialdehyde (MDA) in paraquat-intoxicated Drosophila melanogaster. Paraquat (40 mM) was administrated for 36 h. Three groups of flies intoxicated with paraquat were used: PQ (exposed during 36h to paraquat), PQ-MEL (exposed during 36h to paraquat and then treated with MEL [0.43 mM] for 12 days) and PQ-Control (maintained in standard corn meal for 12 days). Two additional groups without pre-intoxication with PQ were added: Control (maintained in standard corn meal) and MEL (treated with MEL for 12 days). Immediately after PQ intoxication the concentration of MDA (17.240 ± 0.554 nmoles MDA/mg protein) and H2O2 (3.313 ± 0.086 nmol hydrogen peroxide/mg protein) and the activities of SOD and catalase (419.667 ± 0.731 and 0.216 ± 0.009 Units/mg of protein, respectively) in the PQ group were significantly increased with respect to Control. After 12 days of intoxication with PQ, the PQ-Control flies showed increases in H2O2 (4.336 ± 0.108) and MDA levels (8.620 ± 0.156), and in the activities of SOD and catalase (692.570 ± 0.433 and 0.327 ± 0.003, respectively) as compared to PQ-MEL (p<0.001). Treatment with MEL extended the life span of the groups PQ-MEL and MEL when compared to their corresponding controls. Motor activity decreased significantly in PQ-Control and PQ-MEL flies, suggesting that the damage caused by PQ affected the nervous system of flies. Our findings showed that oxidative damage caused by paraquat was observed even after 12 days and that melatonin mitigates this damage.

Investigamos el efecto de la melatonina (MEL) en la actividad de la superóxido dismutasa citosólica (SOD) y la catalasa, así como en las concentraciones del H2O2 y del malondialdehido mitocondrial (MDA) en la toxicidad inducida por paraquat (PQ) en Drosophila melanogaster. El paraquat (40 mM) fue administrado durante 36h. Tres grupos de moscas se utilizaron después de la intoxicación con paraquat: PQ (expuestas a paraquat durante 36 h), PQ-MEL (expuestas durante 36 horas a PQ y luego tratadas con MEL [0,43 mM] por 12 días) y PQ-Control (mantenidas en medio estándar por 12 días). Se incluyeron dos grupos adicionales sin pre-intoxicación con PQ: Control (mantenido en medio estándar) y MEL (tratado con MEL por 12 días). Inmediatamente después de la intoxicación con PQ, las concentraciones de MDA (17,240 ± 0,554 nmol de MDA/mg de proteína), H2O2 (3,313 ± 0,086 nmol de H2O2/mg de proteína) y las actividades de la SOD y catalasa (419,667 ± 0,731 y 0,216 ± 0,009 unidades/mg de proteína, respectivamente) se incrementaron significativamente con respecto al Control. Doce días después de la intoxicación con PQ, las moscas PQ-Control mostraron un aumento en la concentración de H2O2 (4,336 ± 0,108), de los niveles de MDA (8,620 ± 0,156) y en las actividades de la SOD y la catalasa (692,570 ± 0,433 y 0,327 ± 0,003, respectivamente) en comparación con el grupo PQ-MEL (p<0,001). El tratamiento con MEL extendió el tiempo de vida de los grupos PQ-MEL y MEL en comparación con sus correspondientes controles. La actividad motora disminuyó significativamente en las moscas de los grupos PQ-Control y PQ-MEL, lo que sugiere que el PQ afectó el sistema nervioso de las moscas. Nuestros hallazgos demostraron que el daño oxidativo causado por paraquat en las moscas fue observado aún después de 12 días de intoxicadas y que la melatonina logró mitigar este daño.

Effects of melatonin on oxidative stress, and resistance to bacterial, parasitic, and viral infections: a review.

Melatonin, a hormone secreted by the pineal gland, works directly and indirectly as a free radical scavenger. Its other physiological or pharmacological activities could be dependent or independent of receptors located in different cells, organs, and tissues. In addition to its role in promoting sleep and circadian rhythms regulation, it has important immunomodulatory, antioxidant, and neuroprotective effects suggesting that this indole must be considered as a therapeutic alternative against infections. The aim of this review is to describe the effects of melatonin on oxidative stress and the resistance to bacterial (Klebsiella pneumoniae, Helicobacter pylori, Mycobacterium tuberculosis, and Clostridium perfringens), viral (Venezuelan equine encephalomyelitis virus and respiratory syncytial virus), and parasitic (Plasmodium spp., Entamoeba histolytica, Trypanosoma cruzi, Toxoplasma gondii, and Opisthorchis viverrini) infections.

Minocycline increases the activity of superoxide dismutase and reduces the concentration of nitric oxide, hydrogen peroxide and mitochondrial malondialdehyde in manganese treated Drosophila melanogaster.

The toxicity caused by high concentrations of manganese (Mn) could be due to a production of free radicals. Minocycline is an effective antioxidant with a high potential to capture free radicals. We investigated the effect of minocycline in the activities of superoxide dismutase (SOD) and catalase, and in the concentrations of nitric oxide (NO), hydrogen peroxide (H2O2) and mitochondrial malondialdehyde (MDA) in manganese-treated Drosophila melanogaster. Five groups of flies were used: (1) control: not treated; (2) continuously treated with minocycline (0.05 mM); (3) treated with 30 mM Mn for 6 days and then no additional treatment; (4) continuously treated with Mn; (5) treated only with Mn for 6 days and then treated with minocycline; (6) simultaneously treated with Mn and minocycline. On the 6th day, Mn treatment caused 50% mortality; in the surviving flies increased levels of MDA (67.93%), NO (11.04%), H2O2 (14.62%) and SOD and catalase activity (165.34 and 71.43%, respectively) were detected. All the flies continuously treated with Mn died by the 21st day. On day 40, MDA levels were decreased in groups two, three and five (43.04, 29.67, and 34.72% respectively), as well as NO in group two (29.21%) and H2O2 in groups two and five (53.94% and 78.69%, respectively), while in group three the concentration of H2O2 was increased (408.25%). In conclusion, Mn exerted a pro-oxidant effect on the 6th day as shown by the increased levels of oxidative markers. Minocycline extended the lifespan, increased the activity of SOD and reduced the levels of NO, H2O2 and mitochondrial MDA.

Longterm melatonin administration alleviates paraquat mediated oxidative stress in Drosophila melanogaster.

We investigated the effect of melatonin (MEL) in the activities of cytosolic superoxide dismutase (SOD) and catalase as well as in the levels of H2O2 and mitochondrial malondialdehyde (MDA) in paraquat-intoxicated Drosophila melanogaster. Paraquat (40 mM) was administrated for 36 h. Three groups of flies intoxicated with paraquat were used: PQ (exposed during 36h to paraquat), PQ-MEL (exposed during 36h to paraquat and then treated with MEL [0.43 mM] for 12 days) and PQ-Control (maintained in standard corn meal for 12 days). Two additional groups without pre-intoxication with PQ were added: Control (maintained in standard corn meal) and MEL (treated with MEL for 12 days). Immediately after PQ intoxication the concentration of MDA (17.240 +/- 0.554 nmoles MDA/mg protein) and H2O2 (3.313 +/- 0.086 nmol hydrogen peroxide/mg protein) and the activities of SOD and catalase (419.667 + 0.731 and 0.216 +/- 0.009 Units/mg of protein, respectively) in the PQ group were significantly increased with respect to Control. After 12 days of intoxication with PQ, the PQ-Control flies showed in- creases in H2O2 (4.336 +/- 0.108) and MDA levels (8.620 +/- 0.156), and in the activities of SOD and catalase (692.570 +/- 0.433 and 0.327 +/- 0.003, respectively) as compared to PQ-MEL (p<0.001). Treatment with MEL extended the life span of the groups PQ-MEL and MEL when compared to their corresponding controls. Motor activity decreased significantly in PQ-Control and PQ-MEL flies, suggesting that the damage caused by PQ affected the nervous system of flies. Our findings showed that oxidative damage caused by paraquat was observed even after 12 days and that melatonin mitigates this damage.

Minocycline, but not ascorbic acid, increases motor activity and extends the life span of Drosophila melanogaster.

In the present study we compared the effects of minocycline and ascorbic acid in the life span, motor activity and lipid peroxidation of Drosophila melanogaster, in an effort to find a substance capable of providing protection against oxidative stress in aging. In the flies treated with minocycline a very significant increase in the life span (101 +/- 1.33 days) was observed when compared to those treated with ascorbic acid and controls (42.3% and 38.4%, respectively). The motor activity of minocycline treated flies also increased significantly with respect to control and ascorbic acid fed flies, from the 3rd to the 9th week of treatment. With regard to lipid peroxidation, it was found that the levels of malondialdehyde (MDA) in flies treated with minocycline showed no statistical differences to the control on the first day of treatment, but a significantly lower content on the day of 50% survival. In contrast, in flies treated with ascorbic acid significantly elevated levels of MDA compared to control and minocycline treated flies were detected throughout. These results suggest a protective effect of minocycline against oxidative stress and aging in D. melanogaster. An inhibitory effect on reactive oxygen species production may be an important contributing factor.

Minocycline, but not ascorbic acid, increases motor activity and extends the life span of Drosophila melanogaster / La minociclina, pero no el ácido ascórbico, incrementa la actividad motora y extiende el período de vida de Drosophila melanogaster

In the present study we compared the effects of minocycline and ascorbic acid in the life span, motor activity and lipid peroxidation of Drosophila melanogaster, in an effort to find a substance capable of providing protection against oxidative stress in aging. In the flies treated with minocycline a very significant increase in the life span (101 ± 1.33 days) was observed when compared to those treated with ascorbic acid and controls (42.3% and 38.4%, respectively). The motor activity of minocycline treated flies also increased significantly with respect to control and ascorbic acid fed flies, from the 3rd to the 9th week of treatment. With regard to lipid peroxidation, it was found that the levels of malondialdehyde (MDA) in flies treated with minocycline showed no statistical differences to the control on the first day of treatment, but a significantly lower content on the day of 50% survival. In contrast, in flies treated with ascorbic acid significantly elevated levels of MDA compared to control and minocycline treated flies were detected throughout. These results suggest a protective effect of minocycline against oxidative stress and aging in D. melanogaster. An inhibitory effect on reactive oxygen species production may be an important contributing factor.

En el presente estudio se compararon los efectos del ácido ascórbico y la minociclina en la duración del periodo de vida, la actividad motora y la peroxidación lipídica de Drosophila melanogaster en un esfuerzo por encontrar una sustancia capaz de proporcionar protección contra el estrés oxidativo en el envejecimiento. En las moscas tratadas con minociclina se observó un aumento significativo en la duración de la vida (101 ± 1,33 días) en comparación con los tratados con ácido ascórbico y los controles (42,3% y 38,4%, respectivamente). La actividad motora de las moscas tratadas con minociclina aumentó significativamente cuando se comparó con las tratadas con ácido ascórbico y el control, desde la 3ra hasta la 9na semana de tratamiento. Con respecto a la peroxidación lipídica, se encontró que los niveles de malondialdehído (MDA) en moscas tratadas con minociclina no mostraron diferencias estadísticas con relación al control en el primer día de tratamiento; sin embargo, se detecto una disminución significativa de la concentración de MDA cuando se alcanzó el 50% de sobrevida. En contraste, en moscas tratadas con ácido ascórbico observamos que los niveles de MDA estaban significativamente elevados, cuando se compararon con las moscas tratadas con minociclina y el control a lo largo de todo el tratamiento. Estos resultados sugieren un efecto protector de la minociclina frente al estrés oxidativo y el envejecimiento en D. melanogaster, aunque un efecto inhibidor sobre la producción de especies reactivas del oxígeno puede ser un factor contribuyente importante.

The life span of Drosophila melanogaster is affected by melatonin and thioctic acid.

Aging and reduced longevity are due in part to the action of free radicals (FR). Melatonin (Mel) and thioctic acid (TA) are effective in protecting against the damage caused by FR. In this study, the effect of Mel and TA on the life cycle of Drosophila melanogaster was determined. We used a control group of flies, another group that was provided with Mel (0.43 mM) throughout their life cycle (Mel-c), a third group received Mel upon reaching adulthood (Mel-a) and two groups were fed with TA (2.15 mM) in the same manner (TA-c and TA-a). The number of eclosed, survival, phenotype changes, motor activity and the content of malondialdehyde (MDA) was evaluated in each group. Mel-c increased the eclosion rate and the motor activity of the flies. Mel-c and Mel-a increased the life span and decreased the concentrations of MDA. By contrast, TA-c diminished the eclosion rate, produced phenotypic changes and increased MDA levels and motor activity of the flies. TA-a extended the life span of flies, and did not alter MDA levels and motor activity when compared with the control group. In conclusion, Mel mitigated the effects caused by FR generated during aging, while TA-c increased lipid peroxidation and altered the phenotype of flies.

The life span of Drosophila melanogaster is affected by melatonin and thioctic acid / El ciclo de vida de la Drosophila melanogaster es afectado por la melatonina y el ácido tióctico

Aging and reduced longevity are due in part to the action of free radicals (FR). Melatonin (Mel) and thioctic acid (TA) are effective in protecting against the damage caused by FR. In this study, the effect of Mel and TA on the life cycle of Drosophila melanogaster was determined. We used a control group of flies, another group that was provided with Mel (0.43 mM) throughout their life cycle (Mel-c), a third group received Mel upon reaching adulthood (Mel-a) and two groups were fed with TA (2.15 mM) in the same manner (TA-c and TA-a). The number of eclosed, survival, phenotype changes, motor activity and the content of malondialdehyde (MDA) was evaluated in each group. Mel-c increased the eclosion rate and the motor activity of the flies. Mel-c and Mel-a increased the life span and decreased the concentrations of MDA. By contrast, TA-c diminished the eclosion rate, produced phenotypic changes and increased MDA levels and motor activity of the flies. TA-a extended the life span of flies, and did not alter MDA levels and motor activity when compared with the control group. In conclusion, Mel mitigated the effects caused by FR generated during aging, while TA-c increased lipid peroxidation and altered the phenotype of flies.

El envejecimiento y la disminución de la longevidad se deben, en parte, a la acción de los radicales libres (RL). La melatonina (Mel) y el ácido tióctico (AT) son antioxidantes efectivos contra el daño ocasionado por los RL. En este estudio se determinó el efecto de la Mel y el AT en el ciclo de vida de la Drosophila melanogaster. Se utilizó un grupo de moscas control, otro grupo al que se le suministró Mel (0,43 mM) durante todo su ciclo de vida (Mel-c), un tercer grupo recibió Mel al alcanzar la adultez (Mel-a) y dos grupos a los que se le suministró AT (2,15 mM) de la misma manera (AT-c y AT-a). Se evaluó el número de eclosionados, la sobrevida, el fenotipo, la actividad motora y el contenido de malondialdehído (MDA) en cada uno de los grupos. Mel-c incrementó la tasa de eclosión y aumentó la actividad motora. Mel-a y Mel-c aumentaron la sobrevida y disminuyeron las concentraciones de MDA. Por el contrario, el AT-c disminuyó la tasa de eclosión, produjo cambios fenotípicos, no afectó la sobrevida de las moscas, aumentó los niveles de MDA y la actividad motora. El AT-a extendió la duración de la vida de los animales, no alteró los niveles de MDA, ni la actividad motora al comparar con el grupo control. En conclusión, la Mel mitigó los efectos causados por los RL generados durante el envejecimiento, mientras que el AT-c aumentó la peroxidación lipídica y alteró el fenotipo de las moscas.

Effectiveness of melatonin in tardive dyskinesia.

Tardive Dyskinesia (TD) is a movement disorder associated with the clinical administration of antipsychotics. It is believed that TD is due, among other factors, to an increase in the oxidative damage produced by free radicals. Antioxidants, like vitamin E, have been used in the treatment of TD but there is no evidence of their effectiveness. Melatonin (MEL) is 6 to 10 times more effective, as an antioxidant, than vitamin E and it has been used with an apparent higher effectiveness in the treatment of TD, although the results have not been conclusive. A randomized, double blind, placebo controlled design was used to determine the effectiveness of MEL (20 mg/day) during 12 weeks in 7 patients with TD. Six patients with TD were treated with placebo. The Abnormal Involuntary Movement Scale (AIMS) was chosen to assess the severity of TD initially and after 4, 8 and 12 weeks. The psychiatric evaluation was done following the Brief Psychiatric Rating Scale. In two patients treated with MEL a significant improvement (more than 60%) of the values of AIMS was detected. In the remainder five, as well as in the patients treated with placebo, no difference was observed during the 12 weeks. When compared the AIMS score in all the MEL-treated patients with the values in the placebo-treated patients, no significant differences were detected during the 12 weeks of the study. However, the significant clinical improvement observed in two patients must be considered before reaching a final conclusion on the usefulness of MEL in TD.

Effectiveness of melatonin in tardive dyskinesia / Efectividad de la melatonina en la discinesia tardía

Tardive Dyskinesia (TD) is a movement disorder associated with the clinical administration of antipsychotics. It is believed that TD is due, among other factors, to an increase in the oxidative damage produced by free radicals. Antioxidants, like vitamin E, have been used in the treatment of TD but there is no evidence of their effectiveness. Melatonin (MEL) is 6 to 10 times more effective, as an antioxidant, than vitamin E and it has been used with an apparent higher effectiveness in the treatment of TD, although the results have not been conclusive. A randomized, double blind, placebo controlled design was used to determine the effectiveness of MEL (20mg/day) during 12 weeks in 7 patients with TD. Six patients with TD were treated with placebo. The Abnormal Involuntary Movement Scale (AIMS) was chosen to assess the severity of TD initially and after 4, 8 and 12 weeks. The psychiatric evaluation was done following the Brief Psychiatric Rating Scale. In two patients treated with MEL a significant improvement (more than 60%) of the values of AIMS was detected. In the remainder five, as well as in the patients treated with placebo, no difference was observed during the 12 weeks. When compared the AIMS score in all the MEL-treated patients with the values in the placebo-treated patients, no significant differences were detected during the 12 weeks of the study. However, the significant clinical improvement observed in two patients must be considered before reaching a final conclusion on the usefulness of MEL in TD.

La Discinesia Tardía (DT) es un trastorno de los movimientos asociado al uso crónico de antipsicóticos que parece producirse, entre otros factores, por un incremento en los procesos oxidativos. La vitamina E se ha utilizado en su tratamiento, pero no hay evidencia de su efectividad. Como la melatonina (MEL) es 6 a 10 veces más efectiva como antioxidante que la vitamina E, se ha utilizado con una aparente mayor efectividad, aunque los resultados no han sido concluyentes. Se realizó un estudio doble ciego, al azar y controlado con placebo, para determinar la efectividad de la administración de la MEL durante 12 semanas en 7 pacientes con DT. Seis pacientes con DT fueron tratados con placebo. La Escala de Movimientos Involuntarios Anormales (AIMS) se usó para evaluar la evolución de los movimientos al inicio y a las 4, 8 y 12 semanas de tratamiento. La evaluación clínica psiquiátrica se hizo con la Escala Breve de Evaluación Psiquiátrica. En dos pacientes tratados con MEL se observó una mejoría clínica superior al 60% pero en los restantes, así como en los tratados con placebo los valores de la AIMS no variaron significativamente en el transcurso de las 12 semanas. Cuando se compararon los valores de la AIMS de la totalidad de los pacientes tratados con MEL, con los del grupo placebo, no se detectó ninguna diferencia significativa. Sin embargo, la mejoría clínica significativa de dos de los pacientes estudiados debe considerarse para llegar a una conclusión sobre la utilidad de la MEL en la DT.

Ultrastructural study of the hypothalamus in mice chronically treated with manganese / Estudio ultraestructural del hipotálamo de ratones tratados crónicamente con manganeso

Manganese (Mn) is an essential metal that is an integral part of some metalloproteins and acts as a cofactor of several enzymes. Mn is able to cross the blood-brain barrier and enter the nervous system. It has a low toxicity but exposure to high concentrations or for prolonged periods of time produce neurological disorders in humans that initially cause hallucinations and compulsive behaviour followed by stiffness, muscle weakness, ataxia, memory loss and a tremor resembling Parkinson’s disease. This study assessed the ultrastructural alterations produced in the hypothalamus of male albino mice injected intraperitoneally with MnCl2 (5 mg Mn/Kg/day) and a control group injected with NaCl 0.9% (0.1 mL) daily for 9 weeks. The animals were sacrificed by cervical dislocation. The hypothalamus was extracted and subsequently processed to be observed on the conventional transmission electron microscope at 2, 4, 6 and 9 weeks of treatment. After 2 weeks it was observed a slight disruption of the Golgi apparatus and the myelin fibers. After 4 weeks the disorganization was accentuated and dilatation of the endoplasmic reticulum (ER) and alterations of mitochondria were observed. After 6 weeks the normal pattern of the myelin sheath was lost. After 9 weeks of treatment it was found swollen mitochondria with lost of crystae, a marked dilatation of rough and smooth endoplasmic reticulum and dendrites with a high degree of swelling. These results suggest that the neurotoxic effect of Mn increases as time of exposure passes and produces ultrastructural alterations of nerve cells in the hypothalamus.

El manganeso (Mn) es un metal esencial que forma parte de algunas metaloproteínas y actúa como cofactor de varias enzimas. El Mn es capaz de atravesar la barrera hematoencefálica e ingresar al sistema nervioso. Presenta baja toxicidad, pero la exposición a altas concentraciones o por tiempos prolongados produce alteraciones neurológicas en humanos que inicialmente provocan alucinaciones y conducta compulsiva seguidas por rigidez, debilidad muscular, ataxia, pérdida de la memoria y temblor, síntomas similares a los de la enfermedad de Parkinson. En el presente estudio se evaluaron los efectos tóxicos del Mn sobre la ultraestructura del hipotálamo de ratones. Se inyectaron intraperitonealmente ratones albinos machos con MnCl2 (5 mg Mn/Kg/día durante 9 semanas). El grupo control recibió NaCl 0,9% (0,1 mL/dosis). Los animales se sacrificaron por dislocación cervical, extrayéndose y disecándose el hipotálamo, que posteriormente se procesó para realizar observaciones al microscopio electrónico de transmisión convencional a las 2; 4; 6 y 9 semanas de tratamiento. A las 2 semanas, se observó ligera desorganización en el aparato de Golgi y en las fibras mielínicas. A las 4 semanas, se acentuó la desorganización y se comenzó a observar dilatación del retículo endoplasmático liso y rugoso asi como mitocondrias alteradas. A las 6 semanas, se encontró pérdida del patrón normal de la cubierta mielínica. Finalizadas las 9 semanas de tratamiento, se observaron mitocondrias hinchadas con pérdida de las crestas, dilatación acentuada del retículo endoplasmático rugoso y liso y dendritas con cierto grado de edema. Estos resultados parecen indicar que el efecto neurotóxico del Mn aumenta a medida que transcurre el tiempo de exposición para producir alteraciones ultraestructurales de las células nerviosas del hipotálamo.

Ultrastructural changes of the olfactory bulb in manganese-treated mice

The effect of manganese toxicity on the ultrastructure of the olfactory bulb was evaluated. Male albino mice were injected intraperitoneally with MnCl2 (5 mg/Kg/day) five days per week during nine weeks. The control group received NaCl (0.9%). The olfactory bulbs of five mice from each group were processed for transmission electron microscopy after 2, 4, 6 and 9 weeks of manganese treatment. On week 2, some disorganization of the myelin sheaths was observed. After 4 weeks, degenerated neurons with dilated cisternae of rough endoplasmic reticulum and swollen mitochondria appeared. A certain degree of gliosis with a predominance of astrocytes with swollen mitochondria, disorganization of the endomembrane system, dilation of the perinuclear cisternae and irregularly shaped nuclei with abnormal chromatin distribution were observed after 6 weeks. Some glial cells showed disorganization of the Golgi apparatus. On week 9, an increase in the number of astrocytes, whose mitochondrial cristae were partially or totally erased, and a dilation of the rough endoplasmic reticulum were found. Neurons appear degenerated, with swollen mitochondria and a vacuolated, electron dense cytoplasm. These changes seem to indicate that the olfactory bulb is sensitive to the toxic effects of manganese.

Ultrastructural changes of the olfactory bulb in manganese-treated mice

The effect of manganese toxicity on the ultrastructure of the olfactory bulb was evaluated. Male albino mice were injected intraperitoneally with MnCl2 (5 mg/Kg/day) five days per week during nine weeks. The control group received NaCl (0.9%). The olfactory bulbs of five mice from each group were processed for transmission electron microscopy after 2, 4, 6 and 9 weeks of manganese treatment. On week 2, some disorganization of the myelin sheaths was observed. After 4 weeks, degenerated neurons with dilated cisternae of rough endoplasmic reticulum and swollen mitochondria appeared. A certain degree of gliosis with a predominance of astrocytes with swollen mitochondria, disorganization of the endomembrane system, dilation of the perinuclear cisternae and irregularly shaped nuclei with abnormal chromatin distribution were observed after 6 weeks. Some glial cells showed disorganization of the Golgi apparatus. On week 9, an increase in the number of astrocytes, whose mitochondrial cristae were partially or totally erased, and a dilation of the rough endoplasmic reticulum were found. Neurons appear degenerated, with swollen mitochondria and a vacuolated, electron dense cytoplasm. These changes seem to indicate that the olfactory bulb is sensitive to the toxic effects of manganese.(AU)

Ultrastructural changes of the olfactory bulb in manganese-treated mice.

The effect of manganese toxicity on the ultrastructure of the olfactory bulb was evaluated. Male albino mice were injected intraperitoneally with MnCl2 (5 mg/Kg/day) five days per week during nine weeks. The control group received NaCl (0.9%). The olfactory bulbs of five mice from each group were processed for transmission electron microscopy after 2, 4, 6 and 9 weeks of manganese treatment. On week 2, some disorganization of the myelin sheaths was observed. After 4 weeks, degenerated neurons with dilated cisternae of rough endoplasmic reticulum and swollen mitochondria appeared. A certain degree of gliosis with a predominance of astrocytes with swollen mitochondria, disorganization of the endomembrane system, dilation of the perinuclear cisternae and irregularly shaped nuclei with abnormal chromatin distribution were observed after 6 weeks. Some glial cells showed disorganization of the Golgi apparatus. On week 9, an increase in the number of astrocytes, whose mitochondrial cristae were partially or totally erased, and a dilation of the rough endoplasmic reticulum were found. Neurons appear degenerated, with swollen mitochondria and a vacuolated, electron dense cytoplasm. These changes seem to indicate that the olfactory bulb is sensitive to the toxic effects of manganese.

Paraquat-induced oxidative stress in drosophila melanogaster: effects of melatonin, glutathione, serotonin, minocycline, lipoic acid and ascorbic acid.

The efficacy of melatonin, glutathione, serotonin, minocycline, lipoic acid and ascorbic acid in counteracting the toxicity of paraquat in Drosophila melanogaster was examined. Male Oregon wild strain flies were fed for 5 days with control food or food containing the test substance. They were transferred in groups of five to vials containing only filter paper soaked with 20 mM paraquat in 5% sucrose solution. Survival was determined 24 and 48 h later. All the substances assayed increased the survival of D. melanogaster. At equimolar concentrations (0.43 mM) melatonin was more effective than serotonin, lipoic acid and ascorbic acid. However, lower concentrations of glutathione (0.22 mM) and minocycline (0.05 mM) were as efficient as melatonin. The highest survival rate (38.6%) after 48 h of paraquat treatment was found with 2.15 mM of lipoic acid. No synergistic effect of melatonin with glutathione, serotonin, minocycline, lipoic acid and ascorbic acid was detected.

Melatonin and viral infections.

The therapeutic effects of melatonin against viral infections, with emphasis on the Venezuelan equine encephalomyelitis (VEE), are reviewed. Melatonin has been shown to prevent paralysis and death in mice infected with the encephalomyocarditis virus and to decrease viremia. Melatonin also postpones the onset of the disease produced by Semliki Forest virus inoculation and reduces the mortality of West Nile virus-infected mice stressed by either isolation or dexamethasone injection. An increase in the host resistance to the virus via a peripheral immunostimulatory activity is considered responsible for these effects. It has also been demonstrated that melatonin protects some strains of mink against Aleutian disease, and prevents the reduction of B- and T-cells as well as Th1 cytokine secretion in mice infected with leukemia retrovirus. In VEE-infected mice, melatonin postpones the onset of the disease and death for several days and reduces the mortality rate. This protective effect seems to be due to the increase in the production of interleukin-1beta (IL-1beta), as 100% of the infected mice treated with melatonin die when IL-1beta is blocked with antimurine IL-1beta antibodies. Although melatonin administration raises serum levels of tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma), the mortality observed in neutralization experiments with the corresponding anticytokine antibodies, suggests that neither TNF-alpha nor IFN-gamma are essential for the protective effect of melatonin on murine VEE virus infection. Melatonin treatment also enhances the efficiency of immunization against the VEE virus. Reactive oxygen species have been implicated in the dissemination of this virus, and their deleterious effects may be diminished by melatonin. This indole inhibits nitric oxide synthetase activity and it is a potent scavenger of nitric oxide, which also plays an important role in the spread of the VEE virus. In conclusion, the immunomodulatory, antioxidant, and neuroprotective effects of melatonin suggest that this indole must be considered as an additional therapeutic alternative to fight viral diseases.

Melatonin increases interleukin-1beta and decreases tumor necrosis factor alpha in the brain of mice infected with the Venezuelan equine encephalomyelitis virus.

The effect of melatonin (MLT) on the brain levels of tumor necrosis factor alpha (TNF-alpha) and interleukin-1beta (IL-1beta) in Venezuelan equine encephalomyelitis (VEE) virus infection was determined. Brain homogenates from mice inoculated with 10 LD50 of VEE virus, untreated or treated with 500 microg MLT/kg body weight were assayed by ELISA to measure the levels of TNF-alpha and IL-1beta. MLT was injected daily starting 3 days before and continuing to 7 days after virus inoculation. Infected mice treated with MLT showed decreased levels of TNF-alpha when compared to the untreated infected mice on days 1, 3, 4, and 5 postinoculation (P < 0.001). In contrast, IL-1beta levels increased from days 1 to 5 in the infected mice treated with MLT when compared with the untreated infected animals (P < 0.01). The results suggest that the protective effect of MLT on the VEE virus infection could be due, among other factors, to a decrease in TNF-alpha synthesis along with an increase in the production of IL-1beta.

Melatonin induces changes to serum cytokines in mice infected with the Venezuelan equine encephalomyelitis virus.

We determined the influence of melatonin (MLT) on the induction of interleukin (IL)-2, IL-1 beta, IL-4, tumour necrosis factor-alpha (TNF-alpha) and gamma interferon (IFN-gamma) on mice infected with the Venezuelan equine encephalomyelitis (VEE) virus. Levels of IFN-gamma in the MLT-treated group were significantly increased (P < 0.001) when compared with the control non-infected group from day 1 to 6 post-infection (p.i.), while in infected mice treated with 500 micrograms MLT/kg of bodyweight enhanced levels of IFN-gamma were evident from 4 to 6 days p.i. No differences were detected in the levels of IL-2 between the controls, the infected mice treated with MLT and the infected untreated group, from day 2 p.i. No changes in serum levels of IL-4 were detected. In infected mice treated with MLT, blood levels of IL-1 beta were elevated almost 10-fold from day 1 to day 6 p.i. when compared to the control, the infected and the non-infected MLT-treated mice (P < 0.001). A highly significant rise (P < 0.001) of TNF-alpha was found in infected mice treated with MLT, from day 1 to 6 p.i. when compared to the other groups. A significant rise (P < 0.001) was also evident in the infected non-MLT-treated group and a less pronounced rise in the non-infected mice treated with MLT when compared to controls. The blockade of IFN-gamma and TNF-alpha did not inhibit the protective effect of MLT but when IL-1 beta was neutralized, 100% of the infected mice died suggesting that IL-1 beta induced by MLT treatment is a target cytokine to generate an immune response against the viral infection.

Extension of life span and stress resistance of Drosophila melanogaster by long-term supplementation with melatonin.

According to the free radical theory of aging, free radicals are involved in the production of changes in cellular metabolism that lead to a time-dependent functional decline in all living beings. Consequently, antioxidant and/or free radicals scavengers may retard the aging process. We explored the effect of melatonin on the life span of Drosophila melanogaster (Oregon wild strain). It was presumed that given the antioxidant and free radicals scavenger properties of melatonin, this hormone would prevent oxidative damage to the fly tissues and slow down the process of aging. Melatonin, added daily to the nutrition medium at a concentration of 100 microg/ml, increased significantly the life span of D. melanogaster. The maximum life span was 61.2 days in controls and 81.5 days in melatonin fed flies. Relative to the controls, the percentage increase in the melatonin fed flies was 33.2% in maximum life span, 19.3% in the onset of 90% mortality, and 13.5% in median life span. Furthermore, in a test of superoxide mediated toxicity it was shown that melatonin treatment increased the resistance of D. melanogaster to paraquat. Finally, the augmented resistance to an ambient temperature of 36 degrees C was also a demonstration of the antioxidative protection provided by the hormone.