Antagonic effect of the inhibition of inducible nitric oxide on the mortality of mice acutely infected with Escherichia coli and Bacteroides fragilis

Sepsis, the leading cause of death in intensive care units, is associated with overproduction of nitric oxide (NO) due to inducible NO synthase (iNOS), responsible for some of the pathologic changes. Aminoguanidine (AG) is a selective iNOS inhibitor with reported inconsistent actions in sepsis. To investigate the influence of iNOS, we studied models of acute bacterial sepsis using acute challenges with aerobic (Escherichia coli) and anaerobic (Bacteroides fragilis) bacteria in the presence of AG. Six-week-old, 23 g, male and female BALB/c and C57Bl/6j mice, in equal proportions, were inoculated (ip) with bacteria in groups of 4 animals for each dose and each experiment in the absence or presence of AG (50 mg/kg, ip, starting 24 h before challenge and daily until day 6) and serum nitrate was measured by chemiluminescence. Both types of bacteria were lethal to mice, with an LD50 of 6 nephelometric units (U) for E. coli and 8 U for B. fragilis. Nitrate production peaked on the second day after E. coli inoculation with 8 and 6 U (P < 0.05), but was absent after non-lethal lower doses. After challenge with B. fragilis this early peak occurred at all tested doses after 24 h, including non-lethal ones (P < 0.05). AG-treated mice challenged with E. coli presented higher survival (P < 0.05) and increased LD50. AG-treated mice challenged with B. fragilis had lower LD50 and higher mortality. Control AG-treated animals presented no toxic effects. The opposite effect of iNOS blockade by AG in these models could be explained by restriction of oxygen for immune cells or an efficient action of NO in anaerobic localized infections. The antagonic role of NO production observed in our bacterial models could explain the reported discrepancy of NO action in sepsis.

Infectivity of cysts of the ME-49 Toxoplasma gondii strain in bovine milk and homemade cheese

Objetivo: Analisar a infecciosidade e a resistência de cistos de T. gondii em leite e queijo fresco caseiro, pela infecção artificial de leite bovino. Métodos: O leite bovino pasteurizado foi infectado artificialmente com 10 cistos/ml de T.gondii cepa ME49 e inoculado em grupos de camundongos, imediatamente ou após ser estocado por 5, 10 e 20 dias a 4oC. Preparou-se queijo fresco caseiro com leite infectado, sendo testado em grupos de camundongos, utilizando a mesma conservação. A infecção foi detectada pela presença de cistos no cérebro dos camundongos desafiados ou testes sorológicos após cinco semanas, também confirmada por Western Blotting e histologia. Resultados: A infecciosidade dos cistos da cepa ME49 de T.gondii foi mantida mesmo quando armazenado no leite até 20 dias de conservação em condições de refrigeração a 4oC. Os cistos resistiram ao processo de fabricação do queijo e eram infectantes após um período de 10 dias nas mesmas condições. Conclusões: Os achados mostraram que o leite e seus derivados podem ser uma importante fonte de contaminação humana pelo T.gondii, reforçando a importância da pasteurização do leite antes de qualquer processamento ou ingestão

Effect of 60CO gamma radiation on Biomphalaria glabrata (Mollusca, Gastropoda) embryos: mortality, malformation and hatching

A study was carried out on the radiosensitivity of Biomphalaria glabrata embryos submitted to doses of 5, 10, 15, 20 and 25 Gy of 60Co during the cleavage, blastula, gastrula, young trochophore and trochophore stages. Mortality, malformation and hatching were the parameters used to evaluate the damage induced by ionizing radiation. Estimated LD(50) values (15 days) showed that the cleavage stage (4.3 Gy) was approximately four times more radiosensitive than the trochophore stage (l7.0 Gy). Susceptibility to malformation induction was higher in the blastula, gastrula and young trochophore stages. Several types of morphogenetic malformations were observed, such as head malformations, exogastrulas, shell malformations, and embryos with everted stomodeum, with nonspecific malformations being the most frequent. The types of malformation induced by radiation probably are not radiation-specific and do not depend on the dose applied. The dose of 15 Gy was sufficient to greatly reduce the number of hatching snails regardless of the embryonic stage irradiated. We conclude that the effect of (60)Co gamma radiation on B.glabrata embryos presented a specific pattern.

Effect of dietary iron on the course of Plasmodium berghei malaria in young rats

Clinical and experimental evidence suggests that iron-deficient hosts are less susceptible to severe malaria and that iron supplementation aggravates infection. In the present study, 60 weanling Wistar rats were fed standard diets with different iron concentrations: 21 mg/kg (group 1), 45 mg/kg (group 2) and 113 mg/kg (group 3). Ferrous sulfate (FeSO4 x 7H2O) was added to the normal-iron and iron-supplemented diets (groups 2 and 3, respectively). Data are reported as mean +/- SEM. After 16 days of regimen, eight rats from each group were killed to measure serum iron concentration (SI) and transferrin saturation capacity (TSC). At this moment, rats from group 1 were underweight and their dietary intake was significantly lower than that of animals from the other groups. Severe iron deficiency (SI = 49.2 +/- 4.5 micrograms/100 ml and TSC = 8.3 +/- 0.7 per cent ) was observed in rats from group 1, while the animals from the other groups were iron-sufficient (group 2: SI = 186.5 +/- 28.5 micrograms/100 ml and TSC = 27.3 +/- 3.4 per cent ; group 3: SI = 137.3 +/- 18.2 micrograms/100 ml and TSC = 21.3 +/- 2.3 per cent ). Nine animals from each group were then infected with the malaria parasite Plasmodium berghei, whereas three animals from each group were used as noninfected controls. Parasitemias ( per cent of infected red blood cells) peaked 7 days post-infection in animals from groups 2 and 3 (mean values of 2.4 per cent and 1.7 per cent , respectively), but in animals from group 1 parasitemias increased until the 9th day post-infection (mean at peak, 2.3 per cent ) and parasite clearance was significantly slower than in the other groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunochemical detection of purified crotoxin from crotalus durissus terrificus venom in the motor end plate of striaqted muscle in CBA/J mice

Electrophysiological studies of crotoxin, a potent neurotoxic fraction from Crotalus durissus terrificus venom, have shown a pre- and post-synaptic action. In order to determine the specific site of this activity, we performed an immunohistochemicaql analysis on striated muscle from CBA/J mice, injected with crotoxin (5LD50), iv, using a single-step immunoperoxidase assay with peroxidase-conjugated antibodies to whole venom. Control muscle and muscle obtained from treated animals 15 min after injection showed no staining. However, 30 min after injection, the neuromuscular motor end plate of mice who received crotoxin was clearly stained, including thin terminations, without any morphological alteration. Sixty min after administration, the motor end plate was no longer intact, but only roughly formed stained areas without clearly identifiable structures were present. These data show specific crotoxin binding to neural end plates in striated muscle, with a subsequent toxin-induced degeneration of this structure

Comparative and sequential histopathology of plasmodium chabaudi-infected balb/c mice

1. Rodent experimental models have been useful to study severe malaria but few serial and controlled studies have been conducted. In the presente investigation, we describe the histopathology of lethal and non-lethal rodent malaria induced by Plasmodium berghei and P. chabaudi. P. berghei malaria shows a uniformly lethal course, while P. chabaudi malaria produces a non-lethal acute infection with recovery and periodical recurdescences. Sequential histopathological changes were also characterized in P. chabaudi malaria to determine the evolution of the lesions. 2. P. berghei-infected mice have a more severe organ involvement and lower blood regenerative changes than P. chabaudi-infected mice. Two patterns of organ involvement were observed by cimparing the two infections. The first is related to nonspecific parasitized red blood cell clearance by liver and spleen. The second is related to specific changes due to a specific parasite strain interaction with the host, such as those found in the lungs. 3. Sequential changes in P. chabaudi-infected mice were characterized by perihepatocytic reticulin fiber deposition during the recovery from infection, which faded in subsequent stages. Other organs had a similar regressive evolution, except splenic lymphoid tissue which underwent histological restoration or even hypertrophy after depletion in the acute stage. No brain or heart lesions were observed in either model during the acute and subsequent stages. 4. P. chabaudi infection, whose histopathology is described here for the first time, should be useful as a non-lethal experimental model to study the evolution of histological alterations in malaria