Exposure to 2500 lux increases serum melatonin in Venezuelan equine encephalomyelitis.

When mice infected with the Venezuelan equine encephalomyelitis (VEE) virus were exposed to 2500 lux with a 12 h light: 12 h dark photoperiod, the serum levels of melatonin (MLT) remained constantly elevated. In mice exposed to 400 lux low levels of serum MLT were detected during the day and high levels during the night. An increase in the survival rate of the infected mice from 6 to 13 days after virus inoculation was also observed. The significant increment in the concentration of serum MLT produced by the high intensity light could be responsible for the longer survival rate of mice infected with the VEE virus.

[Importance of transmission electron microscopy in the diagnosis of a Venezuelan equine encephalitis outbreak in 1995 in the Venezuelan Guajira]. / Importancia de la microscopía electrónica de transmisión en el diagnóstico de la epidemia de encefalitis equina venezolana de 1995 en la Guajira Venezolana.

Transmission electron microscopy of the brain in 25 newborn mice was performed. Mice were intracerebrally inoculated with cultured VERO cells infected with VEE to be used as positive control, with samples of serum of cerebrospinal fluid from patients with clinical symptoms and signs of encephalitis, with serum from healthy patients or with serum from sick equines. Borate bovine albumin serum was also inoculated in some mice to be used as negative control. All samples were obtained during the epizootic and epidemic outbreak in the Venezuelan Guajira area, northern of Zulia State during October 1995. The ultrastructural study was blindly performed, however the presence of Togavirus particles were detected in 100% of the virologically positive cases. The usefulness, accuracy and speed of the employed methodology is stressed.

Melatonin protects mice infected with Venezuelan equine encephalomyelitis virus.

We investigated whether the administration of melatonin (MLT) reduces the death rate and evolution of the disease in mice infected with Venezuelan equine encephalomyelitis (VEE) virus. Our results show that, MLT protects mice infected with the virus. The mortality rate was reduced from 100% to 16% merely by increasing the dose from 0 to 1000 micrograms/MLT per kg body weight MLT significantly postponed the onset of the disease and death by several days. In surviving mice very high titres of VEE virus IgM antibodies were found seven weeks after virus inoculation. MLT significantly reduced VEE virus levels in blood and brain of infected mice and increased the survival rate when the length of pretreatment was augmented from 3 to 7 or 10 days before virus inoculation. Serum levels of interleukin-2 were not affected by MLT administration. In control mice receiving MLT as well as in infected mice treated or non-treated with MLT, interferon gamma levels in sera were increased. Interleukin-4 concentrations were found to be elevated in sera of non-infected mice receiving MLT, but did not differ from controls in infected mice treated or non-treated with the hormone. MLT reduced the degree of cell destruction produced by VEE virus in culture plates of chicken embryo fibroblasts. The protective effect of MLT warrants further investigation of the possibility of using this hormone for the treatment of humans and equines infected with VEE virus.

[Effect of the attenuated strain (TC-83) of Venezuelan equine encephalitis virus on nuclear transcription in rat brain cells]. / Efecto de la cepa atenuada (TC-83) del virus de la Encefalitis Equina Venezolana sobre la transcripción nuclear en las celulas cerebrales de ratas.

In the present study the effect of the attenuated strain TC-83 of the Venezuelan Equine Encephalitis virus on the nuclear transcription in brain cells of rats was assessed. The transcription activity of the DNA depending RNA polymerases (types I and II) in the isolated nuclei of brain of infected rats and controls was determinated by incorporation of the (3H) UTP. Simultaneously a viral replication curve in the brain and the serum was carried out by plaque forming method in chicken embryo cell cultures. RNA polymerase I activity was only significantly reduced after 25 hours of infection, respect to control values, while polymerase II activity was progressive and significantly diminished from inicial stages of the viral infection at 10, 15, 20 y 25 hours post-infection compared to control values. The virus was not detected in the brain but after 25 hours post-infection with very low titers (< 0.7 log10 P.F.U./ml.), while the viral presence in the blood was demonstrated after a 10 hour period. Our results demonstrated a marked effect of the attenuated strain on the brain nuclear transcription, although the presence of the virus was not detected in the brain of the infected rats. This finding suggest a mechanism of action which deserves further studies to elucidate the cerebral metabolic response and the pathogenesis of the Venezuelan Equine Encephalitis infection.