Does the Use of a "Walking Bleaching" Technique Increase Bone Resorption Markers?

OBJECTIVE: This randomized clinical trial evaluated the effect of 35% hydrogen peroxide in comparison with 37% carbamide peroxide in a nonvital bleaching technique of "walking bleaching" (four sessions of treatment) on periodontal markers: nuclear factor kappa B-ligand (RANK-L-process of root resorption marker) and interleukin 1ß (IL-1ß-inflammatory response marker). METHODS AND MATERIALS: Fifty volunteers presenting with discoloration of nonvital teeth and endodontic treatment in good condition participated. Fifty teeth were randomly divided into two study groups according to bleaching gel: HP = 35% hydrogen peroxide (n=25) and 37% carbamide peroxide (n=25). Nonvital bleaching was performed with a walking bleaching technique consisting of four sessions of bleach application. Gingival crevicular fluid samples were taken in order to quantify the RANK-L and IL-1ß levels by enzyme-linked immunosorbent assay. Samples were obtained from six periodontal sites for each bleached tooth: three vestibular and three palatine (mesial, middle, and distal) at seven time periods: baseline, after each of the four sessions of nonvital bleaching, at one week, and at one month after nonvital bleaching. Tooth color variations were analyzed in each session by VITA Bleachedguide 3D-MASTER (ΔSGU). RESULTS: Significant increments in the RANK-L and IL-1ß levels were detected in each evaluated time compared with baseline ( p<0.05); however, no differences were detected between hydrogen peroxide and carbamide peroxide on increments of the biomarkers studied. The change of color was effective for both nonvital bleaching therapies ( p<0.05). CONCLUSIONS: Nonvital bleaching induced a significant increment in the RANK-L and IL-1ß levels in periodontal tissues around bleached, nonvital teeth.

Terminação de novilhos em pastagem de aveia branca consorciada com leguminosa ou associada à suplementação energética / Finishing steers on oat pasture intercropped with legumes or receiving energetic supplementation

O objetivo do experimento foi avaliar a associação da ervilhaca (Vica sativa) ou da suplementação energética em pastagem de aveia branca (Avena sativa) sobre o desempenho de novilhos de corte na fase de terminação. Foram utilizados 18 novilhos castrados, 1/4 Marchegiana 1/4 Aberdeen Angus 2 / 4 Nelore, com peso vivo e idade média de 360kg e 19 meses, respectivamente, divididos em três tratamentos: pastagem de aveia branca, pastagem de aveia branca consorciada com ervilhaca e pastagem de aveia branca com suplementação energética (milho grão triturado, 1% do peso vivo por dia, na matéria seca)...

The aim of this experiment was to evaluate the association of vetch (Vica sativa) or energy supplementation in oat (Avena sativa) on the performance of steers in the finishing phase. The experiment was performed in 18 steers, quarter Marchegiana, quarter Aberdeen Angus and 2/4 Nellore genetic groups, with the live weight and age of 360kg and 19 months, respectively, divided into three treatments: pasture white oat, pasture white oat intercropped with vetch and oat pasture with energetic supplementation with the basis of ground corn (1% body weight per day in dry matter)...

Correlation of [RuCl3(dppb)(VPy)] cytotoxicity with its effects on the cell membranes: an investigation using Langmuir monolayers as membrane models.

One of the major challenges in drug design is to identify compounds with potential toxicity toward target cells, preferably with molecular-level understanding of their mode of action. In this study, the antitumor property of a ruthenium complex, mer-[RuCl3(dppb)(VPy)] (dppb = 1,4-bis(diphenylphosphine)butane and VPy = 4-vinylpyridine) (RuVPy), was analyzed. Results showed that this compound led to a mortality rate of 50% of HEp-2 cell with 120 ± 10 µmol L(-1), indicating its high toxicity. Then, to prove if its mode of action is associated with its interaction with cell membranes, Langmuir monolayers were used as a membrane model. RuVPy had a strong effect on the surface pressure isotherms, especially on the elastic properties of both the zwitterionic dipalmitoylphosphatidylcholine (DPPC) and the negatively charged dipalmitoylphosphatidylglycerol (DPPG) phospholipids. These data were confirmed by polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS). In addition, interactions between the positive group from RuVPy and the phosphate group from the phospholipids were corroborated by density functional theory (DFT) calculations, allowing the determination of the Ru complex orientation at the air-water interface. Although possible contributions from receptors or other cell components cannot be discarded, the results reported here represent evidence for significant effects on the cell membranes which are probably associated with the high toxicity of RuVPy.

Antimicrobial activity and chemical composition of fixed oil extracted from the body fat of the snake Spilotes pullatus.

CONTEXT: Ethnozoological studies have shown that Spilotes pullatus Linn. (Colubridae: Ophidia), is associated with medicinal and magic-religious uses in Brazil. OBJECTIVES: This study was designed to determine the chemical composition of the oil extracted from the body fat of S. pullatus and to test its antimicrobial properties, alone and in association with aminoglycosides, against fungi and bacterial strains in concentrations ranging between 1024 and 0.5 µg/mL. MATERIAL AND METHODS: The snakes were collected in the Chapada do Araripe, county of Crato, Ceará State, Brazil. The oil was extracted in a Soxhlet apparatus using hexane. The methyl esters of the fatty acids present in the samples were identified using GC-MS. The antimicrobial and drug modulatory activities of oil were tested by microdilution against fungal and bacterial strains. RESULTS: The chemical composition of the fixed oils of S. pullatus identified 10 constituents representing 94.97% of the total sample. The percentages of saturated and unsaturated fatty acids were 33.59 and 61.38%, respectively, with the most abundant components being elaidic (37.26%). The oil did not demonstrate any antimicrobial or antifungal activity when tested alone, presenting MIC values ≥ 1024 µg/mL. However, when associated with antibiotics, it demonstrated synergistic effects with gentamicin against all the bacterial lineages assayed, and antagonistic effects with amikacin and neomycin against strains of Escherichia coli. CONCLUSIONS: Oil extracted from the body fat of S. pullatus did not demonstrate any inhibitory effects on bacterial or fungal activities, but was effective in modulating the effects of certain antibiotics.

Determination of degree of ionization of poly(allylamine hydrochloride) (PAH) and poly[1-[4-(3-carboxy-4 hydroxyphenylazo)benzene sulfonamido]-1,2-ethanediyl, sodium salt] (PAZO) in layer-by-layer films using vacuum photoabsorption spectroscopy.

Electrostatic and hydrophobic interactions govern most of the properties of supramolecular systems, which is the reason determining the degree of ionization of macromolecules has become crucial for many applications. In this paper, we show that high-resolution ultraviolet spectroscopy (VUV) can be used to determine the degree of ionization and its effect on the electronic excitation energies of layer-by-layer (LbL) films of poly(allylamine hydrochloride) (PAH) and poly[1-[4-(3-carboxy-4 hydroxyphenylazo)benzene sulfonamido]-1,2-ethanediyl, sodium salt] (PAZO). A full assignment of the VUV peaks of these polyelectrolytes in solution and in cast or LbL films could be made, with their pH dependence allowing us to determine the pK(a) using the Henderson-Hasselbach equation. The pK(a) for PAZO increased from ca. 6 in solution to ca. 7.3 in LbL films owing to the charge transfer from PAH. Significantly, even using solutions at a fixed pH for PAH, the amount adsorbed on the LbL films still varied with the pH of the PAZO solutions due to these molecular-level interactions. Therefore, the procedure based on a comparison of VUV spectra from solutions and films obtained under distinct conditions is useful to determine the degree of dissociation of macromolecules, in addition to permitting interrogation of interface effects in multilayer films.

Solitary fibrous tumour of the pancreas: a case report.

The solitary fibrous tumour is an uncommon neoplasm of mesenchymal origin. It occasionally develops in extra pleural locations, and is very infrequent in the pancreas. A 40-year-old woman had an unsuspected solitary fibrous tumour detected by chance in the body of the pancreas. Detection of the mass occurred with imaging studies. CT and MRI images showed the well-circumscribed benign lesion, with 3 cm on its greatest diameter. Treatment consisted of partial pancreatectomy, and her postoperative recovery was uneventful.

Avaliação das atividades antioxidante, anti e pró-hemolítica do extrato etanólico das folhas de Pterogyne nitens Tul. (Fabaceae-Caesalpinioideae) / Evaluation of antioxidant, anti- and pro-hemolytic activities of ethanol extract from the leaves of Pterogynenitens Tul. (Fabaceae-Caesalpinioideae)

A pesquisa de produtos naturais permite a descoberta de novos princípios ativos, ou ainda, a descoberta de novas atividades para extratos de plantas (amplamente utilizados pela população brasileira) e princípios ativos naturais já conhecidos. Pterogyne nitens é uma planta cuja descrição das atividades é relativamente recente e, portanto, tem no extrato bruto boa fonte para pesquisas na área de produtos naturais. Desta forma, o objetivo deste trabalho foi estudar o perfil antioxidante do extrato bruto etanólico das folhas de P. nitens e possível interferência sobre a hemólise provocada pelo radical AAPH•. No estudo da ação antioxidante das espécies estudadas, ABTS•+, DPPH•, H2O2 e HOCl, encontrou-se os valores de IC50 de 5,0 µg mL-1, 17 µg mL-1, sem ação e 3,9 µg mL-1, respectivamente, valores relativamente baixos e que indicam bom potencial antioxidante. Foram encontradas atividades pró-hemolítica e anti-hemolítica para o extrato de forma concentração-dependente. O extrato estudado mostro boa fonte de moléculas naturais com potencial de ação biológica.

The search for natural products as a widespread practice enables the discovery of new active principles, or the discovery of new activities for plant extracts (extensively used by the population) and natural active principles already known. Pterogynenitensis is a plant whose descriptions of activities are relatively recent and therefore has in its crude extract a good source for research in the field of natural products. Thus, the aim of this study was to evaluate the antioxidant profile of crude ethanol extract from P. nitens leaves and a possible influence on the hemolysis caused by AAPH• radical. For the studied oxidant species, ABTS•+, DPPH•, HOCl and H2O2, the IC50 values were found of 5.0 µg mL-1, 17 µg mL-1, no action at all, and 3.9 µg mL-1, respectively, relatively low values, indicating a good antioxidant potential. Pro- and anti-hemolytic activities were found for the extract in a concentration-dependent way. The studied extract showed to be a good source of natural molecules with potential biological action.

Interaction of oligonucleotide-based amphiphilic block copolymers with cell membrane models.

Oligonucleotides have unique molecular recognition properties, being involved in biological mechanisms such as cell-surface receptor recognition or gene silencing. For their use in human therapy for drug or gene delivery, the cell membrane remains a barrier, but this can be obviated by grafting a hydrophobic tail to the oligonucleotide. Here we demonstrate that two oligonucleotides, one consisting of 12 guanosine units (G(12)), and the other one consisting of five adenosine and seven guanosine (A(5)G(7)) units, when functionalized with poly(butadiene), namely PB-G(12) and PB-A(5)G(7), can be inserted into Langmuir monolayers of dipalmitoyl phosphatidyl choline (DPPC), which served as a cell membrane model. PB-G(12) and PB-A(5)G(7) were found to affect the DPPC monolayer even at high surface pressures. The effects from PB-G(12) were consistently stronger, particularly in reducing the elasticity of the DPPC monolayers, which may have important biological implications. Multilayers of DPPC and nucleotide-based copolymers could be adsorbed onto solid supports, in the form of Y-type LB films, in which the molecular-level interaction led to lower energies in the vibrational spectra of the nucleotide-based copolymers. This successful deposition of solid films opens the way for devices to be produced which exploit the molecular recognition properties of the nucleotides.

Tuberculin skin testing in HIV-infected patients in Campo Grande, Mato Grosso do Sul State, Brazil

A cross-sectional study on HIV/AIDS was carried out in 108 outpatients from the university hospital of the Federal University of Mato Grosso do Sul, Campo Grande, Brazil, from July to December 2008, to investigate latent tuberculosis infection using the tuberculin skin test (TST). The prevalence of positive results was 13.9 percent. The CD4+ T cell count (p = 0.091) and the diagnosis time (p = 0.010) were statistically significant when compared with TST positivity. In the cohort of HIV/AIDS patients who had latent tuberculosis infection, the median diagnosis time was eight years. Undetectable viral load presented significant association (p = 0.046) with tuberculosis infection. The fact that numerous individuals with HIV/AIDS infection presented a negative reaction to the tuberculin skin test is probably related to alterations in the cellular immune response induced by HIV infection. The tuberculin test is a useful tool for the detection of latent tuberculosis infection and should be performed in all HIV/AIDS individuals at the time of the diagnosis and on a yearly basis, if negative. Both the early identification of the tuberculosis infection by the tuberculin skin test at the moment of immunological restoration and chemoprophylaxis in infected individuals are mechanisms to control HIV/AIDS and tuberculosis coinfection.

Exploiting distinct molecular architectures of ultrathin films made with iron phthalocyanine for sensing.

The possibility of generating distinct film properties from the same material is crucial for a number of applications, which can only be achieved by controlling the molecular architecture. In this paper we demonstrate as a proof-of-principle that ultrathin films produced from iron phthalocyanine (FePc) may be used to detect trace amounts of copper ions in water, where advantage was taken of the cross sensitivity of the sensing units that displayed distinct electrical properties. The ultrathin films were fabricated with three methods, namely physical vapor deposition (PVD), Langmuir-Blodgett (LB), and electrostatic layer-by-layer (LbL) techniques, where for the latter tetrasulfonated phthalocyanine was used (FeTsPc). PVD and LB films were more homogeneous than the LbL films at both microscopic and nanoscopic scales, according to results from micro-Raman spectroscopy and atomic force microscopy (AFM), respectively. From FTIR spectroscopy data, these more homogeneous films were found to have FePc molecules oriented preferentially, tilted in relation to the substrate surface, while FeTsPc molecules were isotropically distributed in the LbL films. Impedance spectroscopy measurements with films adsorbed onto interdigitated gold electrodes indicated that the electrical response depends on the type of film-forming method and varies with incorporation of copper ions in aqueous solutions. Using principal component analysis (PCA), we were able to exploit the cross sensitivity of the sensing units and detect copper ions (Cu(2+)) down to 0.2 mg/L, not only in ultrapure water but also in distilled and tap water. This level of sensitivity is sufficient for quality control of water for human consumption, with a fast, low-cost method.

Antioxidant activity of Maytenus ilicifolia root bark.

Maytenus ilicifolia is an important plant with potential on cancer treatment and has been largely used in Brazil and other countries. We have evaluated the crude ethanolic extract of M. ilicifolia as a potential antioxidant source using an assay based on the bleaching of the radical monocation 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS(*+)) and by HOCl scavenger capacity. Trolox and uric acid were used as positive controls. The results indicated M. ilicifolia root bark as a great source of antioxidants based on its potential as scavenger of radicals.

Indole ring oxidation by activated leukocytes prevents the production of hypochlorous acid

Hypochlorous acid (HOCl) released by activated leukocytes has been implicated in the tissue damage that characterizes chronic inflammatory diseases. In this investigation, 14 indole derivatives, including metabolites such as melatonin, tryptophan and indole-3-acetic acid, were screened for their ability to inhibit the generation of this endogenous oxidant by stimulated leukocytes. The release of HOCl was measured by the production of taurine-chloramine when the leukocytes (2 x 10(6) cells/mL) were incubated at 37°C in 10 mM phosphate-buffered saline, pH 7.4, for 30 min with 5 mM taurine and stimulated with 100 nM phorbol-12-myristate acetate. Irrespective of the group substituted in the indole ring, all the compounds tested including indole, 2-methylindole, 3-methylindole, 2,3-dimethylindole, 2,5-dimethylindole, 2-phenylindole, 5-methoxyindole, 6-methoxyindole, 5-methoxy-2-methylindole, melatonin, tryptophan, indole-3-acetic acid, 5-methoxy-2-methyl-3-indole-acetic acid, and indomethacin (10 æM) inhibited the chlorinating activity of myeloperoxidase (MPO) in the 23-72 percent range. The compounds 3-methylindole and indole-3-acetic acid were chosen as representative of indole derivatives in a dose-response study using purified MPO. The IC50 obtained were 0.10 ± 0.03 and 5.0 ± 1.0 æM (N = 13), respectively. These compounds did not affect the peroxidation activity of MPO or the production of superoxide anion by stimulated leukocytes. By following the spectral change of MPO during the enzyme turnover, the inhibition of HOCl production can be explained on the basis of the accumulation of the redox form compound-II (MPO-II), which is an inactive chlorinating species. These results show that indole derivatives are effective and selective inhibitors of MPO-chlorinating activity.

Atenção farmacêutica voltada ao Diabetes Melittus / Pharmaceutical care on Diabetes Mellitus

Foi realizada uma pesquisa junto aos profissionais farmacêuticos no município de Curitiba, no estado do Paraná, Brasil, com o objetivo de buscar informações necessárias à dispensão de medicamentos específicos ao portador de diabetes mellitus. Observou-se a falta de conhecimento no que se refere à temática abordada, incluindo procedimentos e produtos. Na discussão apresentou-se uma análise crítica dos resultados e inseriu-se os aspectos cognitivos necessários à elucidação de inúmeras dúvidas encontradas junto aos profissionais. Para tanto, propõe-se medidas de atualização sobre o diabetes mellitus pelo profissional farmacêutico, demonstrando-se as vantagens em promover o esclarecimento das dúvidas dos pacientes no momento da dispensação e, propõe-se a incorporação, no cotidiano do profissional, da atenção farmacêutica nos cuidados primários à saúde do portador do diabetes

Sentinel lymph node identification and sampling in women with early breast cancer using 99m Tc labelled dextran 500 and patent blue V dye.

The status of the homolateral axillary lymph nodes is still the most important prognostic factor in early stage breast cancer. The information obtained from the pathological examination of the lymph nodes guides is of critical importance in the decision process regarding the use of postoperative adjuvant therapy. However, lymph node axillary dissection can be followed by significant locoregional morbidity. The sentinel lymph node (SLN) technique was developed as a means of avoiding the full exploration of the axilla and consists in the identification of the first lymph node in the lymphatic drainage system of the breast tumour in the homolateral axilla. It has been demonstrated that the status of the SLN is highly predictive for the presence or absence of tumour involvement in the remaining lymph nodes in the axilla. In this study we evaluated the SLN technique using both 99mTc labelled dextran 500 and patent blue V dye in relation to the classical lymph node resection a series of 56 women with early breast cancer who attended the Breast Unit of the Academic Hospital of the Federal University of Rio Grande do Sul, Brazil. To our knowledge this is the first report in the literature of the utilization of 99mTc dextran 500 for the SLN technique. As there are no similar commercially available dedicated radiopharmaceuticals labelled for use in lymphoscintigraphy studies, we report on an effective method to label dextran 500 with 99mTc which proved to be simple, inexpensive and yielded similar results for SLN identification compared with those given in the literature. The median age of the patients was 57 years (range 32-82 years). Seventeen patients were age 50 years or less, and 39 patients were older than 50 years. The median tumour size was 2.0 cm (range 0.8-7.0 cm). The mapping of the SLN was possible in all cases during the transoperative period by using a hand-guided gamma probe and a blue dye. A median of 2.0 (range 1-5) SLN were excised per patient. The median of axillary lymph nodes excised per patient was 21 (range 10-36). The calculated sensitivity and specificity of the method were 95.6% and 100%, respectively. The negative predictive value and overall accuracy were 97% and 98.2%, respectively. In conclusion, the SLN technique was feasible and produced similar positive results as previously reported in the literature.

Cooperativity of phospholipid reorganization upon interaction of dipyridamole with surface monolayers on water.

Results from various surface sensitive characterization techniques suggest a model for the interaction of the piperidinopyrimidine dipyridamole (DIP)--known as a vasodilator and inhibitor of P-glycoprotein associated multidrug resistance of tumor cells--with phospholipid monolayers in which the drug is peripherally associated with the membrane, binding (up to) five phospholipids at a time. These multiple interactions are responsible for a very strong association of the drug with the lipid monolayer even at exceedingly low concentrations (approximately 0.2 mol%). Electrostatic interactions and hydrogen bonding are likely involved in the binding of DIP to DPPC. Cooperative effects among the lipids are invoked to explain the macroscopically measurable changes of lipid monolayer properties even when only one out of 100 DPPC molecules is directly associated with a DIP molecule. A reversal of the observed changes upon drug association with the membrane as the DIP concentration surpasses a threshold concentration (c(crit)approximately 0.5 mol%) may be explained by cooperativity in a different context, the self-aggregation of drug molecules. With its implications for the interaction of DIP with phospholipid films, this work provides a first approach to the explanation of the high sensitivity of cell membranes to piperidinopyrimidine drugs on a molecular level.

Structural Modification Influences the Characteristics of Langmuir Monolayers from Aromatic Carboxylic Acids.

The molecular organization of purely aromatic, polyphenyl carboxylic acids, as Langmuir monolayers at the air/water interface, has been investigated by means of surface pressure and electric surface potential measurements upon film compression. The monolayer characteristics of the basic compound, a symmetrical triphenylbenzene (5'-phenyl-m-terphenyl) ring with a carboxylic group at the 4 position (namely 5'-phenyl-1,1' : 3',1"-terphenyl-4-carboxylic acid), are compared with those of its derivatives containing hydrophilic (nitro) or hydrophobic (phenyl) substituents. The nature of the substituent as well as its position (2' or 4') has a profound influence on the monolayer properties. The results are discussed in view of molecular orientation deduced from values of effective dipole moments. Copyright 2001 Academic Press.

Retrospective clinical analysis of stented vs. stentless porcine aortic bioprostheses.

OBJECTIVE: The study was designed to compare hemodynamic performance, structural failure and survival of patients undergoing aortic valve replacement (AVR) with a composite aortic stented or stentless porcine bioprosthesis. METHODS: From January 1990 to June 1999, the clinical data of 725 patients undergoing AVR with stented porcine aortic bioprosthesis were reviewed. We defined two groups of patients with similar clinical characteristics: 202 patients receiving aortic stented and 205 patients stentless valves. The two patients groups were similar in age, sex, valve lesion, valve size, preoperative New York Heart Association (NYHA) class status and follow-up. RESULTS: The number of patients available for follow-up, excluding hospital and late mortality, reoperations and patients lost to follow-up, was 157 for the stented and 175 for the stentless group. There was a higher incidence of rheumatic heart disease in the stented (59%) vs. stentless group (44%), (P=0.003). Fewer patients had prior aortic bioprosthetic dysfunction in the stented (7.6%) compared to the stentless group (25%) (P<0.001). The mean intensive care unit stay, hospital mortality and late mortality were similar (P, NS). The total complication rate was higher in the stented (12%) than the stentless (3.4%)(P=0.005). Valve related death was higher in the stented (2.5%) than the stentless (0%) (P=0. 049). Postoperatively, the aortic effective orifice area (AEOA) was larger (P<0.001) and the transvalvular peak and mean gradients were lower in the stentless group (P<0.001). The leaflet tissue degeneration analysis was 8.0% in patients at risk for stented and 0. 6% for stentless (P=0.001). Actuarial analysis disclosed no statistical difference in patient survival between groups (P=0.18). Reoperations were less frequent in the stentless group (P=0.010). CONCLUSIONS: Hemodynamic benefits in the stentless group were evident and expressed by larger AEOA, lower gradients, better left ventricular remodeling with significant decrease of the left ventricular mass. Lower complication rates, lower reoperation rates, less leaflet tissue degeneration, and lower valve related mortality rates were seen in the stentless group. A controlled clinical comparison trial with longer follow-up will be required to confirm these clinical and hemodynamic benefits.

Biosynthesis of friedelane and quinonemethide triterpenoids is compartmentalized in Maytenus aquifolium and Salacia campestris.

Maytenus aquifolium (Celastraceae) and Salacia campestris (Hippocrateaceae) species accumulate friedelane and quinonemethide triterpenoids in their leaves and root bark, respectively. Enzymatic extracts obtained from leaves displayed cyclase activity with conversion of the substrate oxidosqualene to the triterpenes, 3beta-friedelanol and friedelin. In addition, administration of (+/-)5-(3)H mevalonolactone in leaves of M. aquifolium seedlings produced radio labelled friedelin in the leaves, twigs and stems, while the root bark accumulated labelled maytenin and pristimerin. These experiments indicated that the triterpenes once biosynthesized in the leaves are translocated to the root bark and further transformed to the antitumoral quinonemethide triterpenoids.

Life cycle of Trypanosoma cruzi (Y strain) in mice.

Since 1958, we have studied experimental Chagas' disease (CD) by subcutaneous inoculation of 1,000 blood forms of Trypanosoma cruzi (Y strain) in Balb/C. mice. Evolution of parasitemia remained constant, beginning on the 5th and 6th day of the disease, increasing progressively, achieving a maximum on about the 30th day. After another month, only a few forms were present, and they disappeared from the circulation after the third month, as determined from direct examination of slides and the use of a Neubauer Counting Chamber. These events coincided with the appearance of amastigote nests in the tissues (especially the cardiac ones), starting the first week, and following the Gauss parasitemia curve, but they were not in parallel until the chronic stage. In 1997, we began to note the following changes: Parasites appeared in the circulation during the first week and disappeared starting on the 7th day, and there was a coincident absence of the amastigote nests in the tissues. A careful study verified that young forms in the evolutionary cycle of T. cruzi (epi + amastigotes) began to appear alongside the trypomastigotes in the circulation on the 5th and 7th post-inoculation day. At the same time, rounded, oval, and spindle shapes were seen circulating through the capillaries and sinusoids of the tissues, principally of the hematopoietic organs. Stasis occurs because the diameter of the circulating parasites is greater than the vessels, and this makes them more visible. Examination of the sternal bone marrow revealed young cells with elongated forms and others truncated in the shape of a "C" occupying the internal surface of the blood cells that had empty central portions (erythrocytes?). We hypothesize that there could be a loss of virulence or mutation of the Y strain of Trypanosoma cruzi.