Evaluation of chemotherapy in experimental toxocarosis by determination of specific immune complexes

Parasitism by the larval phase of Toxocara canis is a chronic process in which the larvae survive in the tissues, resulting in the constant stimulation of the immune system. As a result, the detection of specific antibodies may not reflect the active state of the parasite. We have studied the dynamics of the production of specific immune complexes by ELISA with the monoclonal antibody TC-1 in rabbits inoculated with single and multiple doses of T. canis eggs. We also compared this with the production of specific antibodies and their possible modification after treatment with mebendazole. The specific antibodies against excretory-secretory antigen were detected with peaks at 10 and 12 weeks depending on the dose and remained positive during the entire experiment (62 weeks). Treatment caused an increase in the level of detectable antibodies dropping to similar levels to the controls. Specific immune complexes were detected only in multiple doses, and were then positive during the entire experiment. From the beginning of treatment the values of immune complexes fell quickly, remaining at undetectable levels during the rest of the experiment. For this reason the detection of specific immune complexes is a valid technique for monitoring the efficiency of treatment.     

Effect of converting enzyme inhibition with captopril on baroreflex sensitivity

Clinical and experimental data suggest that both Captopril and angiotensin II (AII) reduce baroreflex responsiveness, and the main action of this converting enzyme inhibitor (CEI) seems clear to suppress AII synthesis. The aim of this work is to investigate this striking similarity of effects. We have verified that CEI (4 mg/kg) originates tachycardia significantly lower (P less than 0.001) than that produced in response to a similar hypotension elicited by an unspecific vasodilator: sodium nitroprusside (10-45 micrograms/kg min). CEI SQ 20881 has been reported to increase plasma vasopressin concentrations (AVP); this peptide is also known to modify baroreflex responses and has a small direct negative chronotropic effect. However, our determinations of AVP do not show any difference between the control group and the group treated with Captopril (4.78 +/- 0.87 and 5.26 +/- 0.19 pg/ml respectively). On the other hand, although CEI did not modify the rapid responses of heart rate (HR) to changes of mean arterial pressure (MAP), the decrease of MAP induced by nitroprusside was higher in the group treated with Captopril than in control group; it could mean a baroreflex ability decrease to buffer the hypotension. However, AII elicited a strong impairment of both rapid responses of HR and the buffering of hypotension produced by NP, these actions being suggested as centrally mediated. These results could indicate that the suppression of peripheral AII synthesis and therefore, the lack of pre- and postjunctional sympathetic potentiation owing to this hormone, is responsible for the absence of tachycardia under Captopril treatment.     

Persistence of immune response in human toxocariasis as measured by ELISA.

The antibody titer was followed in a group of patients, clinically diagnosed with toxocariasis, during a 5 year period. We observed that larvae can survive for at least 5 years in humans. Antigenic stimulation was enough to keep high levels of immunoglobulins over this period. Antibody levels decreased slowly and this pattern is similar to that shown by animal models.     

QSAR modeling and transmission electron microscopy stereology of altered mitochondrial ultrastructure of white blood cells in patients diagnosed as schizophrenic and treated with antipsychotic drugs.

Treatment of patients diagnosed as schizophrenic with antipsychotic drugs (neuroleptics) is known to cause occasional unexplained depletion of white blood cells, especially neutrophil granulocytes. It has been known for many years that neuroleptics can interfere with the mitochondrial respiratory chain in vitro. Because there has been a growing interest recently in mitochondrial targeting of drugs, and since a quantitative structure-activity relationship (QSAR) model that predicts mitochondrial accumulation of neuroleptics has been published, we investigated the effects of neuroleptics on white blood cell mitochondria. Venous blood samples were collected from both patients undergoing treatment with neuroleptics and healthy volunteers. The samples were processed for transmission electron microscopy. The resulting images of white blood cells were analyzed using stereology to compare quantitatively mitochondrial morphology in the patient and control groups. We found that in patients, but not in controls, there was swelling of mitochondria and fragmentation of the mitochondrial cristae. There also were fewer mitochondria in patients than in controls, although due to the swelling of the organelles, the volume density of mitochondria in the two groups was not significantly different. Such changes are typical of a toxic insult. Consequently, it seems plausible that, since schizophrenia is not a disease considered to affect white blood cells per se, these changes probably are due to the medication.     

Genital microsporidiosis in women with AIDS: A post-mortem study

BackgroundMicrosporidiosis is a life threatening opportunistic infection of AIDS patients. The infection is usually restricted to specific anatomical areas, but could become systemic depending on the involved species. Genital microsporidiosis in female patients is rare.ObjectiveTo report genital microsporidiosis in female AIDS patients.MethodsTissues samples from the genital tract (ovary, fallopian tubes and uterus) of eight deceased women who died of wasting syndrome associated to AIDS and disseminated microsporidiosis at the Institute of Tropical Medicine Pedro Kourí were collected between 1997 and 2005. Using an indirect immunohistochemistry assay the microsporidia species involved in those cases were identified.ResultsWe report several cases of microsporidial infection of the female genital tract. Six out of eight women with the disseminated form of the disease showed the presence of microsporidia in the genital tract. Encephalitozoon cuniculi and Encephalitozoon hellem were identified in the internal lining epithelium of the fallopian tubes and endometrium.ConclusionsMicrosporidia species could disseminate to other organs and become systemic in severe immunocompromised cases. To our knowledge this is the greatest number of female genital tract microsporidiosis cases so far reported in humans.     

Animal models in ocular toxocariasis

Ocular toxocariasis is a clearly defined disease. However, much remains to be learned concerning the migratory route, ocular changes, diagnosis and treatment. Studies in paratenic hosts have contributed to our understanding and will yield more information. Various experimental animals have been used, such as mice, rabbits, guinea pigs, primates, hamsters and gerbils. Of these, the last appear to be the most appropriate model due to their high susceptibility to ocular infection. Results obtained from different animal models are often not comparable due to the fact that dose and routes of inoculation are diverse. Early stages in the pathogenesis of ocular toxocariasis are manifested by haemorrhages in the anterior chamber and iris, replaced in time by accumulations of white cells. Ocular migration produces an early cell reaction, formed by an infiltration of neutrophils accompanied by vasculitis and retinal microinfarcts. Over a period of time, an increase of macrophages and the distribution of the infiltrates is observed. Later, granulomatous lesions are formed. These do not necessarily contain a larva and their appearance varies in different animal models. Local production of IgE and the presence of specific IgG have been described.     

Cross-reactivity induced by Anisakis simplex and Toxocara canis in mice

The aim of this study was to verify whether cross-reactivity appeared between Toxocara canis and Anisakis simplex in an experimental rodent model. No cross-reactions were detected using sera from mice infected with T. canis eggs. When responses obtained against T. canis ES antigen using sera from BALB/c and C57BL/10 mice infected with T. canis eggs were compared with those obtained by testing sera from mice infected with one A. simplex L3, an increase in cross-reactions was observed using the C57BL/10 strain.     

Isotype specific immune responses in murine experimental toxocariasis

In this work, a murine experimental model of toxocariasis has been developed in BALB/c, C57BL/10 and C3H murine strains orally inoculated with 4,000 Toxocara canis embryonated eggs, in order to investigate the isotype-specific immune responses against excretory-secretory antigens from larvae. T. canis specific IgG+M, IgM, IgG, IgA, IgG1, IgG2a and IgG3 were tested by ELISA. The dynamics of the specific immunoglobulins (IgG+IgM) production showed a contrasting profile regarding the murine strain. Conversely to the results obtained with the IgM isotype, the IgG antibody class showed similar patterns to those obtained with IgG+IgM antibodies, only in the case of the BALB/c strain, being different and much higher than the obtained with IgG+IgM antibodies, when the C3H murine strain was used. The antibodies IgG+IgM tested in BALB/c and C57BL/10 were both of the IgM and IgG isotypes. Conversely, in the C3H strain only IgG specific antibody levels were detected. The IgG1 subclass responses showed a similar profile in the three murine strains studied, with high values in BALB/c, as in the case of the IgG responses.     

Can submerged macrophytes be effective for controlling waterborne phytopathogens in irrigation ponds? An experimental approach using microcosms

Irrigation ponds may act as a source of phytopathogenic species that might infest crops through the irrigation systems. Many studies have shown that submerged macrophytes can improve water clarity by out-competing phytoplankton by means of various mechanisms: favoured phytoplankton-grazing zooplankton, reduced nutrient and light availability, increased sinking losses and the release of allelopathically active substances. However, less information is available on the effects of submerged macrophytes on heterotrophic aquatic organisms such as pathogenic bacteria, fungi or oomycete species. This paper studies the effects of three submerged macrophytes—Chara fragilis, Potamogeton pectinatus and Najas marina—on the viability in water of propagules of two phytopathogenic isolates of the oomycetes Pythium aphanidermatum and Pythium ultimum. Moreover, we tested general antimicrobial properties (against bacteria and fungi in water) for these macrophytes. The results showed clear inhibitory effects of all three macrophytes on bacterial density in water and of C. fragilis on the viability of Pythium. Thus, preserving aquatic vegetation in irrigation ponds (i.e. charophytes), besides its purely environmental interest, may have important agronomic benefits owing to their role as biological control against some phytopathogenic agents.