Immune response in cattle induced by inactivated rabies vaccine adjuvanted with aluminium hydroxide either alone or in combination with avridine.

In a comparative study of two commercial baby hamster kidney rabies vaccines produced in Brazil, the authors were able to demonstrate the following: a) both vaccines provoked a high level of antibody response and protection against challenge in cattle b) in primary vaccination, at least, the addition of avridine (a synthetic lipoidal amine) enhances the immune response in terms of the level and persistence of antibody c) over 90% of cattle vaccinated with either vaccine were protected against experimental challenge one year after revaccination, and the antibody response profile indicated that these vaccines were capable of maintaining antibody titres above protective levels for more than two years after revaccination. On the basis of these results, the authors recommend optional revaccination of young animals (i.e. "primo-vaccinates") at six months of age. Thereafter, annual revaccination should be sufficient to ensure high levels of antibody between vaccination cycles.

Laboratory diagnosis of rabies by the fluorescent antibody test applied to brain tissues of experimentally inoculated mice and either preserved in formalin or under refrigeration

Avaliou-se a adequaçäo do emprego de cérebros preservados em formol para o estabelecimento rápido do diagnóstico da raiva pela reaçäo de imunofluorescência direta, utilizando a técnica de digestäo enzimática de pepsina e tripsina e método de impressäo para o preparo de lâminas. O delineamento proposto contou com fragmentos de cérebros de camundongos experimentalmente infectados submetidos a diferentes tratamentos de conservaçäo, com o uso de soluçöes de formol com pH corrigidos, ou submetidos à refrigeraçäo; os testes de imunofluorescência foram realizados em 10 fases experimentais, por um período de 28 dias. Os resultados da prova de imunofluorescência variaram de 58.0 por cento a 90.0 por cento de positividade, dependendo dos tratamento dispensados. Nas condiçöes do experimento, os materiais destinados à prova de imunofluorescência podem ser conservados em temperatura de refrigeraçäo por até 96 horas; após este período aumentam os resultados irregulares devido à degradaçäo tissular. Nos tecidos mantidos em formol e após digestäo enzimática, com a aplicaçäo do método de impressäo, observou-se o fenômeno de restauraçäo da antigenicididade do vírus rábico, permitindo uma adequada identificaçäo através da prova de imunofluorescência; no entanto, estes procedimentos näo devem substituir os métodos atualmente empregados para o diagnóstico rápido da raiva

Evaluation of the toxicity of 3-allyl-beta-lapachone against Trypanosoma cruzi bloodstream forms.

In vitro incubation of Trypanosoma cruzi (Y strain) with 3-allyl-beta-lapachone was followed by: (1) growth inhibition of epimastigotes, (2) damage to cellular membranes, especially of the mitochondria, alterations in the chromatin structure and swelling of mitochondria, (3) increase in the respiratory rate, (4) increase in the rate of H2O2 generation by the epimastigotes, (5) increase of the rate of lipid peroxidation as detected by malonyldialdehyde formation, (6) decrease or total disappearance of trypomastigotes from mouse-infected blood. This drug might therefore be useful in preventing transmission of Chagas' disease during blood transfusion. It is not, however, active against infections in mice.

In vitro and in vivo evaluation of the toxicity of 1,4-naphthoquinone and 1,2-naphthoquinone derivatives against Trypanosoma cruzi.

The toxic effect of lapachol, beta-lapachone and several 1,2-naphthoquinone derivatives on the growth, viability and infectivity of Trypanosoma cruzi were compared. beta-lapachone was the most active compound in vitro. No inhibition was observed in suspensions which contained inactivated foetal calf serum or rabbit haemoglobin solution. The infectivity of trypomastigotes in mice was not affected when cells were previously incubated with beta-lapachone or one of several other naphthoquinone derivatives in vitro in the presence of blood. It is suggested that beta-lapachone and the other compounds can be inactivated either by reduction in the presence of oxyhaemoglobin or by interaction with serum proteins. A beta-lapachone derivative, allyl-beta-lapachone, was not inactivated in the presence of blood and remained effective in suppressing trypomastigote infectivity.

Generation of free radicals from phenazine methosulfate in Trypanosoma cruzi epimastigotes.

A significant growth inhibition of Trypanosoma cruzi epimastigotes by phenazine methosulfate (PMS) was observed in Warren's medium. This toxic activity could be related to the following parameters: a) formation of phenazinium free radical, b) generation of superoxide anion in intact cells incubated with PMS, and c) PMS also increased significantly the rate of O2- generation in epimastigotes mitochondrial and microsomal fractions using NADH as electron donor.

Toxicity of 4-nitroquinoline 1-oxide for Crithidia fasciculata.

Growth inhibition of Crithidia fasciculata by 4-nitroquinoline 1-oxide (NQO) was observed in defined and complex media at 28 C. Aromatic amino acids, cystein, and nicotinic acid, among several other substances, were ineffective in overcoming NQO toxicity. Dicoumarol and bovine albumin reversed NQO inhibition. While bovine albumin probably acted by the extra-cellular binding of NQO, dicoumarol inhibited the activity of DT-diaphorase, which reduces NQO to 4-hydroxyaminonitroquinoline 1-oxide (HAQO). The DT-diaphorase from C. fasciculata had the same characteristics as the enzyme from rat liver. The specific protection by dicoumarol against NQO inhibition suggests that HAQO is the active toxic substance for C. fasciculata.