Scielo RSS <![CDATA[Biological Research]]> vol. 43 num. 3 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>A Tribute to Professor Gustavo Hoecker Salas</b>]]> <![CDATA[<b>Vertical transmission of <i>Trypanosoma cruzi </i>in the Province of Choapa, IV Region, Chile</b>: <b>Preliminary Report (2005-2008)</b>]]> Congenital Chagas disease acquired special importance in Chile after the certification of the control of Triatoma infestans and transmission by blood donors affected with Trypanosoma cruzi. In order to establish adequate protocols for intervention and control in infected mother-neonate pairs in endemic zones of Chagas disease, we present partial results (2005-2008) of a pilot project which is being carried out in the Province of Choapa, IV Region, Chile, whose objectives are: determine the current prevalence of the disease in pregnant women, estimate the incidence of vertical transmission of T. cruzi to newborns, determine the lineages of the parasite present in mothers who do and do not transmit the disease, determine the prevalence of Chagas disease in maternal grandmothers of neonates and study placental histopathology. Preliminary results indicated that in this study period, 3.7% of the women who gave birth in the Province have Chagas disease and 2.5% of their newborns were infected. The most frequent T. cruzi genotypes found in mothers studied during pregnancy were TCI and TCIId, either alone or in mixed infections. A high percentage (74.3%) of the grandmothers studied was infected with the parasite. In 29 placentas from mothers with Chagas disease we observed edema, necrosis, fibrinoid deposits and slight lymphoplasmocyte infiltration. In three placentas we found erythroblastosis and in one of them amastigote forms of T. cruzi; this was one of the cases of congenital infection. The evaluation of the diagnostic and control protocols generated will allow us to determine if it has been possible to modify the natural history of vertical transmission of T. cruzi in Chile. <![CDATA[<b>Model of chromosome associations in <i>Mus domesticus </i>spermatocytes</b>]]> Understanding the spatial organization of the chromosomes in meiotic nuclei is crucial to our knowledge of the genome's functional regulation, stability and evolution. This study examined the nuclear architecture of Mus domesticus 2n=40 pachytene spermatocytes, analyzing the associations among autosomal bivalents via their Centromere Telomere Complexes (CTC). The study developed a nuclear model in which each CTC was represented as a 3D computer object. The probability of a given combination of associations among CTC was estimated by simulating a random distribution of 19 indistinguishable CTC over n indistinguishable "cells" on the nuclear envelope. The estimated association frequencies resulting from this numerical approach were similar to those obtained by quantifying actual associations in pachytene spermatocyte spreads. The nuclear localization and associations of CTC through the meiotic prophase in well-preserved nuclei were also analyzed. We concluded that throughout the meiotic prophase: 1) the CTC of autosomal bivalents are not randomly distributed in the nuclear space; 2) the CTC associate amongst themselves, probably at random, over a small surface of the nuclear envelope, at the beginning of the meiotic prophase; 3) the initial aggregation of centromere regions occurring in lepto-zygotene likely resolves into several smaller aggregates according to patterns of preferential partitioning; 4) these smaller aggregates spread over the inner face of the nuclear envelope, remaining stable until advanced stages of the meiotic prophase or even until the first meiotic division. <![CDATA[<b>Comparative <i>in vivo </i>antiangiogenic effects of calreticulin from <i>Trypanosoma cruzi </i>and <i>Homo sapiens sapiens</i></b>]]> Angiogenesis is a complex multi-step process of neovascularization arising from preexisting blood vessels whose generation is regulated by pro- and anti-angiogenic factors. Both Trypanosoma cruzi calreticulin (TcCRT) and its human counterpart (HuCRT) are antiangiogenic. This is the first report where the TcCRT and HuCRT anti-angiogenic properties are compared in vivo. In the chick embryonic chorioallantoid membrane assay (CAM) and at equimolar concentrations, TcCRT displayed significantly higher antiangiogenic activities than its human counterpart. LPS had marginal effects at the concentrations present in the recombinant protein preparations and the TcCRT antiangiogenic effects were largely inhibited by specific polyclonal antibodies, thus, reinforcing the fact that the observed TcCRT effects can be attributed to the parasite-derived molecule and not to the endotoxin. The antiangiogenic TcCRT effects correlate with its anti-tumor in vivo effects, as recently shown in our laboratory. <![CDATA[<b>Immunohistochemical evidences showing the presence of thymulin containing cells located in involuted thymus and in peripheral lymphoid organs</b>]]> Thymulin is a well-characterized thymic hormone that exists as a nonapeptide coupled to equimolar amounts of Zn2+. Thymulin is known to have multiple biological roles, including T cell differentiation, immune regulation, and analgesic functions. It has been shown that thymulin is produced by the reticulo-epithelial cells of the thymus, and it circulates in the blood from the moment of birth, maintain its serum level until puberty diminishing thereafter in life. To study the localization of this hormone, we prepared polyclonal and monoclonal antibodies against the commercial peptide and utilized immunocytochemical techniques for visualization. The results indicate that thymulin stains the thymic reticular cells, the outer layers of Hassall's corpuscles and a large round cellular type, which is keratin-negative and does not show affinity for the common leukocyte antigen (CD-45). In mice, this thymulin-positive cell remains in the thymus throughout life and even appears in relatively increased numbers in old involuted thymi. It also appears in thymus-dependent areas of the spleen and lymph nodes, demonstrating that at least one of the thymus cells containing this peptide can be found in peripheral lymphoid tissue. <![CDATA[<b>Omissions in the synthetic theory of evolution</b>]]> The Synthetic Theory of Evolution is the most unifying theory of life science. This theory has dominated scientific thought in explaining the mechanisms involved in speciation. However, there are some omissions that have delayed the understanding of some aspects of the mechanisms of organic evolution, principally: 1) the bridge between somatic and germinal cells, especially in some phylum of invertebrates and vertebrates; 2) horizontal genetic transferences and the importance of viruses in host adaptation and evolution; 3) the role of non-coding DNA and non-transcriptional genes; 4) homeotic evolution and the limitations of gradual evolution; and 5) excessive emphasis on extrinsic barriers to animal speciation. This paper reviews each of these topics in an effort to contribute to a better comprehension of organic evolution. Molecular findings suggest the need for a new evolutionary synthesis. <![CDATA[<b>Infection and invasion mechanisms of <i>Trypanosoma cruzi </i>in the congenital transmission of Chagas' disease</b>: <b>A proposal</b>]]> Chagas' disease is produced by the haemophlagelated protozoan Trypanosoma cruzi and transmitted by haematophages insects such as Triatoma infestans (vinchuca). Due to vector control, congenital transmission gains importance and is responsible for the presence and expansion of this disease in non-endemic areas. The mechanisms of congenital infection are uncertain. It has been suggested that the parasite reaches the fetus through the bloodstream by crossing the placental barrier, and that congenital Chagas' disease is the result of complex interactions between the immune response, placental factors, and the parasite's characteristics. We review the cellular and molecular mechanisms of infection and invasion of the parasite and how immune and placental factors may modulate this process. Finally, we propose a possible model for the vertical transmission of Chagas' disease. <![CDATA[<b>Betamethasone inhibits tumor development, microvessel density and prolongs survival in mice with a multiresistant adenocarcinoma TA3</b>]]> Tumor resistance to traditional cancer treatments poses an important challenge to modern science. Thus, angiogenesis inhibition is an important emerging cancer treatment. Many drugs are tested and corticosteroids have shown interesting results. Herein we investigate the effect on microvessel density, survival time and tumoral volume of mice with TA3-MTX-R tumors. Twenty six mice were inoculated with lxlO6 tumor cells, 4-5 days after injection, six mice were injected with PBS (group A) and twenty mice were treated with p-met (group B). All animals from Group A died on day 22. Group B was divided into Bl (treated discontinued) and B2 (treated daily) and observed until day 88. All mice were processed for histo-immunohistochemical analysis and the blood vessels were counted. A decrease in microvessel density and tumoral volume and longer survival times were observed in the treated group. We propose that the antiangiogenic p-met effect explains, at least partially, its tumor inhibitory properties. As an important perspective, we will experimentally combine these strategies with those recently described by us with regard to the important antiangiogenic-antitumor effects of Trypanosoma cruzi calreticulin. Since the molecular targets of these strategies are most likely different, additive or synergic effects are envisaged. <![CDATA[<b>Chagas disease</b>: <b>Present status of pathogenic mechanisms and chemotherapy</b>]]> There are approximately 7.8 million people in Latin America, including Chile, who suffer from Chagas disease and another 28 million who are at risk of contracting it. Chagas is caused by the flagellate protozoan Trypanosoma cruzi. It is a chronic disease, where 20%-30% of infected individuals develop severe cardiopathy, with heart failure and potentially fatal arrhythmias. Currently, Chagas disease treatment is more effective in the acute phase, but does not always produce complete parasite eradication during indeterminate and chronic phases. At present, only nifurtimox or benznidazole have been proven to be superior to new drugs being tested. Therefore, it is necessary to find alternative approaches to treatment of chronic Chagas. The current treatment may be rendered more effective by increasing the activity of anti-Chagasic drugs or by modifying the host's immune response. We have previously shown that glutathione synthesis inhibition increases nifurtimox and benznidazole activity. In addition, there is increasing evidence that cyclooxygenase inhibitors present an important effect on T. cruzi infection. Therefore, we found that aspirin reduced the intracellular infection in RAW 264.7 cells and, decreased myocarditis extension and mortality rates in mice. However, the long-term benefit of prostaglandin inhibition for Chagasic patients is still unknown. <![CDATA[<b>Cyclosporin A-treated Dendritic Cells may affect the outcome of organ transplantation by decreasing CD4+CD25+ regulatory T cell proliferation</b>]]> One of the mechanisms for generation of tolerance involves immature dendritic cells (DCs) and a subpopulation of regulatory CD4+ CD25+ T lymphocytes (T REG). The purpose of this work was to analyze how Cyclosporine A (CsA), a widely used immunosuppressive drug, may affect T REG proliferation. Purified and activated murine DCs obtained from bone marrow precursors differentiated with rGMCSF were co-cultured with purified CFSE-labeled T REG from OTII mice, and their phenotype and proliferation analyzed by flow cytometry. Our data indicate that DCs differentiated in the presence of CsA show an altered phenotype, with a lower expression of MHC-II and a lower activating capacity. Additionally, these CsA-treated DCs show decreased production of IL-2 and IL-12 and increased IL-10 secretion when stimulated with LPS, indicating an effect on the polarization of the immune response. Interestingly, CsA-treated DCs show an anti-tolerogenic effect since they reduce the proliferation of T REG cells from 72 to 47%. Further inhibition to a 24% of T REG proliferation was obtained as a direct effect of CsA on T REG. In conclusion, the anti-tolerogenic effect of CsA should be considered in the planning of immunosuppression in the context of clinical transplantation. <![CDATA[<b>Histocompatibility and Immunogenetics in Cord Blood Transplantation</b>]]> This review of the immunogenetics of cord blood transplantation attempts to highlight the connections between classical studies and conclusions of the tissue transplantation field as a scholarly endeavor, exemplified by the work of Professor Hoecker, with the motivations and some recent and key results of clinical cord blood transplantation. The authors review the evolution of understanding of transplantation biology and find that the results of the application of cord blood stem cells to Transplantation Medicine are consistent with the careful experiments of the pioneers in the field, from the results of tumor and normal tissue transplants, histocompatibility immunogenetics, to cell and molecular biology. Recent results of the National Cord Blood Program of the New York Blood Center describe the functioning in cord blood transplantation of factors, well known in transplantation immunogenetics, like the Fl anti-parent effect and the tolerance-like status of donors produced by non-inherited maternal HLA antigens. Consideration of these factors in donor selection strategies can improve the prognosis of transplantation by characterizing "permissibility" in HLA-incompatible transplantation thereby increasing the probability of survival and reducing the likelihood of leukemic relapse. <![CDATA[<b>Sexual orientation, handedness, sex ratio and fetomaternal tolerance-rejection</b>]]> Fraternal birth order (FBO) appears as a prenatal cause of 15% of homosexual males (gays) through mnemonic maternal anti-male factors. Non-right-handed men seem to be protected from homosexuality. Four hypotheses are proposed: (1) androgenic factors of non-right-handedness neutralize anti-male factors; (2) non-right-handedness and homosexuality are lethal or produce mental impairment; (3) non-right-handed male embryos are insensitive to anti-male factors; (4) mothers of non-right-handed fetuses do not produce anti-male factors. Studies of the sex ratio (SR) of older and younger siblings show: (1) a significant heterogeneity in the SR of siblings of right or non-right handed heterosexual men and women; (2) lesbians are born among siblings with high SR; (3) siblings of right-handed gays show a higher SR than non-right-handed gays that present a low SR. Based on our discovery of maternal tolerance-rejection processes, associated with genetic systems (ABO, Rh), where zygotes or embryos different from their mother induce better pregnancy and maternal tolerance than do those that share antigens with their mothers, I propose a new explanation for sexual relationships, sexual orientation, handedness and sibling SR. Lesbian embryos could induce tolerance from mothers with anti-female factors. Non-right-handedness could induce maternal tolerance, or change the maternal compatibility of "gay" embryos. Alternatively, gay embryos could be poor inducers of maternal tolerance towards male traits. <![CDATA[<b>Chronic toxicity bioassay with populations of the crustacean <i>Artemia salina </i>exposed to the organophosphate diazinon</b>]]> A chronic toxicity bioassay was conducted with the microcrustacean Artemia salina as the testing organism for the toxic organophosphate diazinon in order to determine if the species is an appropriate indicator of pollution in aquatic environments. Tests of animal exposure to different concentrations of the toxicant were performed for 24, 48 and 72 hours after larvae hatching. Registered mortality data was used to obtain the lethal dose 50 (LD50) of the organophosphate for each exposure time, considering the immobilization of A. salina larvae as the mortality parameter. The lethal concentration (LD50) in the same exposure times was calculated by evaluating morphological changes on the three initial stages of larval development. Both doses were determined by using probit statistical analysis. Results indicate greater dose-response exactitude after 24 hours of exposure to the toxicant. High sensitivity of the organism to the toxicant was determined, thus indicating that A. salina is an appropriate ecotoxicological bioindicator of aquatic environments polluted with pesticides, with the special consideration that this species is a natural resident of saline water bodies, and thus could be used to control pollution in these environments as a result of the unrestrained usage of such toxic substances. <![CDATA[<b>Cytoprotective and suicidal signaling in oxidative stress</b>]]> Oxidative stress is an imbalance between pro-oxidants and antioxidants in favor of the pro-oxidants, leading to different responses depending on the level of pro-oxidants achieved and the duration of exposure. In this article, we discuss the cytoprotective or suicidal signaling mechanisms associated with oxidative stress by addressing: (i) the development of an acute and mild pro-oxidant state by thyroid hormone administration eliciting the redox upregulation of the expression of proteins affording cell protection as a preconditioning strategy against ischemia-reperfusion liver injury; and (ii) the role of prolonged and severe oxidative stress and insulin resistance as determinant factors in the pathogenesis of non-alcoholic fatty liver disease associated with obesity.