Carmen Contreras - Academia.edu (original) (raw)

Papers by Carmen Contreras

Journal of Immunology, Jun 1, 1979

Immune complex formation during Plasmodium berghei infection of OF1 mice was investigated. Circul... more Immune complex formation during Plasmodium berghei infection of OF1 mice was investigated. Circulating immune complexes (CIC) were detected by the Clg-binding assay and the conglutinin-binding solid-phase assay in lethal or drug-limited infections. CIC appeared on day 9 of infection, peaked on day 11, and disappeared only after complete cure of the infection. Analysis of the immune complexes detected by the Clq-binding assay revealed the following characteristics: sedimentation coefficients of 13S to 21S, resistance to DNAse, and selective removal by filtration through protein A bound to Sepharose. Glomerular deposits of IgM preceded the appearance of CIC, whereas deposits of IgG and C3 were concomitant with the appearance of CIC. Tissue-bound immunoglobulins were also found in the choroid plexus. The appearance of anti-malarial antibodies and malarial antigens in the serum was closely associated with a depression of C3 levels and the presence of CIC. Drug treatment was followed by normalization of C3 levels, and clearance of both CIC and malarial antigens.

American Journal of Tropical Medicine and Hygiene, Oct 1, 2002

The state of Bolivar in Venezuela experiences episodic outbreaks of multidrug-resistant Plasmodiu... more The state of Bolivar in Venezuela experiences episodic outbreaks of multidrug-resistant Plasmodium falciparum malaria. We obtained P. falciparum-infected blood samples in Bolivar in 1998−2000, and performed molecular assays for mutations conferring resistance to the antifolate combination of sulfadoxine-pyrimethamine (SP) and to chloroquine. All infections carried the dihydrofolate reductase (dhfr) S108A and N51I mutations, and 45% of the infections had the dhfr C50R mutation, which has been implicated in mid-level resistance to SP. Two dihydropteroate synthase (dhps) mutations also involved in SP resistance, A581G and K540E, were detected in 90% and 67% of the samples, respectively. The dhfr I164L mutation, which confers high-level resistance, was not identified. The P. falciparum chloroquine resistance transporter (pfcrt) K76T mutation, which is critical for chloroquine resistance, was found in 167 of 168 infections. Six dhfr/dhps allelotypes and four pfcrt-resistant alleles were observed. Their interrelationships suggest a semi-clonal propagation of P. falciparum malaria in Bolivar, and an invasion of multi-resistant pathogens from Brazil. Despite national restrictions on the use of SP and chloroquine, genotypic resistance to these therapies remains widespread in Bolivar.

Mycopathologia, Sep 1, 1982

The severest forms of paracoccidioidomycosis (Pcm) are associated with impaired cell-mediated imm... more The severest forms of paracoccidioidomycosis (Pcm) are associated with impaired cell-mediated immunity, a phenomenon that is reversible with therapy. It has been postulated that plasma factors could be responsible for such immune dysfunction. In this report, circulating immune complexes (C1C) were measured by the Raji cell radioimmunoassay (Raji) and by the ~251-C I q binding assay (C 1 q-BA) in sera from 14 patients with either active or inactive forms of Pcm and from 15 healthy controls. The C 1 q-BA revealed significantly elevated levels of CIC in the sera of all but one of the patients. Four of the 8 active (62%) and 2 of the 6 inactive (33%) patients had CIC levels significantly higher than the controls as determined by the Raji test. Significantly increased levels of C1C were detected only in the active patients by the Raji test. The serum of one of the patients, with a generalized infection and depressed lymphocyte responsiveness, was examined and found to contain a factor which depressed the in vitro proliferation of both homologous and normal lymphocytes. We also found that pre-culture of the patients' lymphocytes before stimulation restored their proliferative capacity, and IC were detectable in the culture supernatants. However, the subsequent addition of the patients' serum to such precultured cells did not reinduce the depression. It is suggested therefore, that the depression of T cell responses observed in Pcm is due to the presence of IC which may interact reversibly with the responding cells and/or activate a suppressor cell population whose activity is diminished by preculture.

Springer eBooks, 1995

The eradication of malaria was conceived in the mid-1950s as an activity of limited duration. Wit... more The eradication of malaria was conceived in the mid-1950s as an activity of limited duration. With the recognition in the late 1960s that eradication was not feasible, attention turned to control and newer approaches to combat this major cause of human misery. According to published estimates, malaria parasites annually infect 250 to 300 million people, cause 100-120 million clinical cases, and kill 1 to 2 million people. Including recent estimates of malaria from sub-Saharan Africa, these numbers could be as high as 500-900 million infections annually. Insecticide resistance in the mosquitoes, drug resistance in the parasites are, among many others (poverty, ignorance, social disruptions and often inadequate national resources, etc.), major causes for resurgence of malaria worldwide (Oaks et al. 1991). Over the last 20 years, major scientific advances have been made in the understanding of the immuno-biology of host-parasite interactions. The major goal of malaria research at the molecular and immunological fronts has been the identification and characterization of vaccine candidates.

PubMed, Dec 1, 1980

The development of circulating immune complexes was studied in mice of the BALB/c, A/J, OF1, CBA ... more The development of circulating immune complexes was studied in mice of the BALB/c, A/J, OF1, CBA and C57B1 strains infected with P. berghei. Complexes were evaluated in relation to levels of parasitaemia, soluble antigen, specific antibody and C3. Susceptibility to infection was greatest in BALB/c, A/J and OF/a mice. The maximum parasitaemia was 30% in CBA and 70% in all other strains. Levels of soluble antigen paralleled those of parasitaemia. Specific antibody was detected in all strains, but the titre continued to rise throughout the infection only in CBA mice. Circulating immune complexes occurred in mice of all strains from day 6; the level fell after day 9 in C57B1 whereas it was maintained in CBA mice. The development of immune complexes was associated with marked depression of C3 levels in all except CBA mice, in which a transient reduction was followed by recovery. Partial characterization of the complexes showed that IgM-containing complexes appeared earliest and reached highest levels in BALB/c mice while in CBA mice, IgM complexes were found in lesser amounts and the level fell in late infection. IgG complexes rose throughout infection in CBA and fell in later stages in BALB/c and C57B1 mice. In nude BALB/c mice, immune complexes were usually not detectable and only low levels of antibody of IgM class were produced. Differences in mortality pattern could not be related to any single serological factor.

American Journal of Tropical Medicine and Hygiene, Jun 1, 1999

Malaria antibody detection is valuable in providing retrospective confirmation of an attack of ma... more Malaria antibody detection is valuable in providing retrospective confirmation of an attack of malaria. Blood bank screening is another area were malaria serology is potentially useful. In the present study, we tested the presence of antibodies to Plasmodium falciparum in sera from blood bank donors of non-endemic and malariaendemic areas of Venezuela. Sera from 1,000 blood donors were tested by an indirect immunofluorescent antibody (IFA) assay and an IgG-ELISA for the presence of malaria antibodies using a synchronized in vitro-cultured Venezuelan isolate of P. falciparum as the antigen source. A selected group of positive and negative sera (n ϭ 100) was also tested by a dot-IgG-ELISA. Positive results (reciprocal titer Ն 40) were found in 0.8% and 3.8% of blood donors when tested by the IFA assay and in 0.8% and 2% (optical density Ն 0.2) when tested by the IgG-ELISA in Caracas (non-endemic area) and Bolivar City (endemic area), respectively. The presence of anti-malarial antibodies in some sera from non-endemic areas such as Caracas reflects the increased potential risk of post-transfusional malaria in those areas due to the mobility of the blood donors. The data obtained indicate the need to implement new blood donor policy in blood banks in developing areas. Our results also indicate that the IFA assay is the most reliable test to use in malaria serodiagnosis.

Cancer, May 1, 1982

The immunological spectrum in fifteen patients with gastric cancer is presented. Patients were di... more The immunological spectrum in fifteen patients with gastric cancer is presented. Patients were divided in three groups. Those with nonadvanced cancer, those with advanced but resectable lesions and those with advanced but nonresectable tumors. Preoperatively, elevated levels of circulating immune complexes (CIC) associated with hyporesponsiveness to phytohemagglutinin (PHA) and in mixed lymphocyte culture (MLC) as well as a positive leukocyte inhibitory serum factor (LIF-S) were found in nearly half of the patients. Inhibitory or enhancing autologous serum factors were detected. Postoperatively, immunologic parameters return to normal in patients with nonadvanced cancer, while in advanced cancer, antibody and cell-mediated immune response remained altered, with some changes associated with chemotherapy. These findings are probably related with the presence or absence of tumor and offer a distinct approach in evaluating the immunologic response of a tumor-bearing patient.

Memórias do Instituto Oswaldo Cruz, 2004

The evaluation of new antimalarial agents using older methods of monitoring sensitivity to antima... more The evaluation of new antimalarial agents using older methods of monitoring sensitivity to antimalarial drugs are laborious and poorly suited to discriminate stage-specific activity. We used flow cytometry to study the effect of established antimalarial compounds, cysteine protease inhibitors, and a quinolone against asexual stages of Plasmodium falciparum. Cultured P. falciparum parasites were treated for 48 h with different drug concentrations and the parasitemia was determined by flow cytometry methods after DNA staining with propidium iodide. P. falciparum erythrocytic life cycle stages were readily distinguished by flow cytometry. Activities of established and new antimalarial compounds measured by flow cytometry were equivalent to results obtained with microscopy and metabolite uptake assays. The antimalarial activity of all compounds was higher against P. falciparum trophozoite stages. Advantages of flow cytometry analysis over traditional assays included higher throughput for data collection, insight into the stage-specificity of antimalarial activity avoiding use of radioactive isotopes.

This article cites 52 articles, 26 of which can be accessed free at:

Memórias do Instituto Oswaldo Cruz, 2011

In Venezuela, a total of 363,466 malaria cases were reported between [1999][2000][2001][2002][200... more In Venezuela, a total of 363,466 malaria cases were reported between [1999][2000][2001][2002][2003][2004][2005][2006][2007][2008][2009]. Several states are experiencing malaria epidemics, increasing the risk of vector and possibly transfusion transmission. We investigated the risk of transfusion transmission in blood banks from endemic and non-endemic areas of Venezuela by examining blood donations for evidence of malaria infection. For this, commercial kits were used to detect both malaria-specific antibodies (all species) and malaria antigen (Plasmodium falciparum only) in samples from Venezuelan blood donors (n = 762). All samples were further studied by microscopy and polymerase chain reaction (PCR). The antibody results showed that P. falciparum-infected patients had a lower sample/cut-off ratio than Plasmodium vivax-infected patients. Conversely, a higher ratio for antigen was observed among all P. falciparum-infected individuals. Sensitivity and specificity were higher for malarial antigens (100 and 99.8%) than for antibodies (82.2 and 97.4%). Antibodypositive donors were observed in Caracas, Ciudad Bolívar, Puerto Ayacucho and Cumaná, with prevalences of 1.02, 1.60, 3.23 and 3.63%, samples were observed among the donors. However, our results show significant levels of seropositivity in blood donors, suggesting that more effective measures are required to ensure that transfusion transmission does not occur.

Brazilian Journal of Medical and Biological Research, 2007

Whole blood samples (N = 295) were obtained from different locations in Amazonas and Sucre States... more Whole blood samples (N = 295) were obtained from different locations in Amazonas and Sucre States, in Venezuela. Malaria was diagnosed by microscopy, OptiMAL™ and polymerase chain reaction (PCR), with Plasmodium vivax, P. falciparum, and P. malariae being detected when possible. We identified 93 infections, 66 of which were caused by P. vivax, 26 by P. falciparum, and 1 was a mixed infection. No infection caused by P. malariae was detected. The sensitivity and specificity of each diagnostic method were high: 95.7 and 97.9% for microscopy, 87.0 and 97.9% for OptiMAL, and 98.0 and 100% for PCR, respectively. Most samples (72.2%) showed more than 5000 parasites/µL blood. The sensitivity of the diagnosis by microscopy and OptiMAL decreased with lower parasitemia. All samples showing disagreement among the methods were reevaluated, but the first result was used for the calculations. Parasites were detected in the 6 false-negative samples by microscopy after the second examination. The mixed infection was only detected by PCR, while the other methods diagnosed it as P. falciparum (microscopy) or P. vivax (OptiMAL) infection. Most of the false results obtained with the OptiMAL strip were related to the P. falciparum-specific band, including 3 species misdiagnoses, which could be related to the test itself or to genetic variation of the Venezuelan strains. The use of the microscopic method for malaria detection is recommended for its low cost but is very difficult to implement in large scale, population-based studies; thus, we report here more efficient methods suitable for this purpose.

Kiru, Jun 1, 2008

Navarro C., Pareja MC., Maita L. Eficacia de la clorhexidina y del control mecánico en la reducci... more Navarro C., Pareja MC., Maita L. Eficacia de la clorhexidina y del control mecánico en la reducción de gingivitis en niños de 10 a 12 años.

The largest projected LSR velocities (~80 km/s) are measured at the tips of the lobes, where the ... more The largest projected LSR velocities (~80 km/s) are measured at the tips of the lobes, where the direct images show the presence of compact bow-shaped structures. The velocity of the shocks in CRL618 is in the range ~75-200 km/s, as derived from diagnostic line ratios and line profiles. We report a brightening (weakening) of [OIII]5007AA ([OI]6300AA) over the last ~10 years that may indicate a recent increase in the speed of the exciting shocks. From the analysis of the spatial variation of the nebular extinction, we find a large density contrast between the material inside the lobes and beyond them: the optical lobes seem to be `cavities' excavated in the AGB envelope by interaction with a more tenuous post-AGB wind. The electron density, with a mean value n_e~5E3-1E4 cm-3, shows significant fluctuations but no systematic decrease along the lobes, in agreement with most line emission arising in a thin shell of shocked material (the lobe walls) rather than in the post-AGB wind filling the interior of the lobes. (...)

J Food Sci, 2006

Retail-packed rump (Gluteus medius, GM) and striploins (Longissiumus dorsi, LD) steaks were maste... more Retail-packed rump (Gluteus medius, GM) and striploins (Longissiumus dorsi, LD) steaks were masterpackaged under carbon dioxide (CO 2 ) and stored at 1 • C ± 1 • C for 14, 28, 35, and 42 d. A commercial oxygen (O 2 ) scavenger (ATCO HV1000 , Standa Industrie, Caen, France) was used in the masterpacks to achieve an O 2 -free atmosphere. Similar packages without the O 2 scavengers were also prepared. At each storage time, 2 masterpacks of each treatment were opened and the retail trays were placed in a display case at 4 • C ± 2 • C for 1 and 48 h for microbiological and sensorial evaluations. The low growth rate of aerobic psychrotrophic flora on the stored beefsteaks demonstrated the bacteriostatic effect of CO 2 during storage. The maximum level of psychrotrophic aerobic bacteria reached during storage was approximately 10 6 CFU/g. The steaks stored in masterpacks with scavengers bloomed to the desirable red color associated with freshly cut meat in the display case for all of the storage periods, except in the case of GM steaks, which showed a cycle of transient discoloration. GM and LD steaks were well accepted (65% and 82%, respectively) after 42 d under CO 2 at 1 • C ± 1 • C. The GM and LD steaks stored without the O 2 scavenger showed variable fractions of discoloration that significantly detracted from the appearance of the samples.

Este artículo analiza un conjunto de consorcios tecnológicos apoyados con recursos públicos en Ar... more Este artículo analiza un conjunto de consorcios tecnológicos apoyados con recursos públicos en Argentina, Chile, Colombia y Uruguay. Estos programas buscan facilitar la interacción entre empresas e instituciones dedicadas a la producción de ciencia y tecnología. Los resultados, basados en datos recabados para un subconjunto de los grupos apoyados, ponen en relieve las dificultades y los largos tiempos que se requieren para lograr resultados concretos, en particular, en innovación tecnológica. El trabajo cuantitativo muestra una evaluación relativamente baja de las empresas respecto al efecto de estos instrumentos en la generación de innovaciones de productos y procesos y la obtención de patentes, aunque existen aspectos relativamente mejor evaluados, como el mejoramiento del acceso a conocimiento tecnológico, en ámbitos

Astrophys J, 2004

We present deep optical long-slit spectra of the peculiar protoplanetary nebula (PPN) OH 231.8+4.... more We present deep optical long-slit spectra of the peculiar protoplanetary nebula (PPN) OH 231.8+4.2 obtained with the 6.5 m Baade Telescope at Las Campanas Observatory (Chile). In addition to the molecular absorption bands characteristic of the M9-10 III star inside OH 231.8+4.2 (QX Pup), we identify lines of the Balmer series in absorption, which do not form in the cool atmospheres of late M-type stars. We also confirm the presence of a blue continuum excess with an intensity that is a factor ~30 larger than that expected for an M9-10 III star. Our results indicate the presence of a source hotter than QX Pup illuminating OH 231.8+4.2 that is likely a main-sequence star with spectral type A. We discuss how the formation and nebular evolution of OH 231.8+4.2 could have been affected by the presence of a binary system in its core.

The impact of fast, collimated jets on the spherical, slowly expanding circumstellar envelopes of... more The impact of fast, collimated jets on the spherical, slowly expanding circumstellar envelopes of AGB stars, is believed to be responsible for the remarkable bipolarity and high axial-velocities observed in most post-AGB objects (protoplanetary and planetary nebulae). From an analysis of spatially-varying Hα absorption line features in (archival) STIS long-slit spectra, we recently discovered very fast (upto 2300 km/s) collimated outflows in the prototype protoplanetary nebula, He3-1475 (Sánchez Contreras & Sahai 2001, ApJ, 553, L173). Here, we report results from a similar analysis of STIS spectra of the post-AGB object, HD44179 (also known as the Red Rectangle because of its red colors and rectangular morphology). Unlike He3-1475, the Hα absorption line profile (relative to the continuum) does not show strong changes along the slit, indicating that both the continuum and the absorption arise near or from the central star; we are mostly seeing the stellar spectrum reflected off dust in the nebula. In contrast, the Hα emission profile does change significantly along the slit, indicating its origin in a spatially resolved (although compact) region around the star. The clear velocity gradient in this inner region (the emission from the north/south lobe is blue-/red- shifted) indicates a bipolar outflow with a speed greater than or about 65 km/s. This is the first time that this inner, bipolar outflow is seen in this object and the first time that (given the unusual proximity of HD44179 at 380 pc) observations enable us to study the post-AGB wind as close as 40 AU from the central star. The expansion age of the outflow material in its innermost regions is only 3 yrs. The velocity of this outflow decreases with distance beyond +/-0".2 (75 AU). Unravelling the complex structure and kinematics of the outflow suggested by this behaviour will require detailed modeling (in progress), but should yield important insights into the physical properties of the fast post-AGB outflow in HD44179.

Bulletin of the American Astronomical Society, Dec 1, 2000

We analyse (archival) optical long-slit spectra of the Protoplanetary Nebula He3-1475 taken with ... more We analyse (archival) optical long-slit spectra of the Protoplanetary Nebula He3-1475 taken with the Space Telescope Imaging Spectrograph (STIS) onboard the Hubble Space Telescope (GO7285, PI: P. Harrington). This object shows a remarkable bipolar morphology and clear evidence of shocks probably resulting from the interaction between a fast, collimated wind and the slowly expanding envelope formed during the Asymptotic Giant Branch evolution of the central star. This shock interaction is the mechanism thought to be responsible for the shaping of planetary nebulae. A total of eight 0\farcs1-wide slits parallel to the main symmetry axis of the nebula were used, providing, with unprecedented detail, its structure and kinematics, specially of its innermost regions. The presence of two blue-shifted absorption features in the Hα profile, suggest two different components of gas outflowing at high velocity ( ~1000 and ~ 300 km s-1). The ultrahigh- and high-velocity absorption features are present in the NW lobe (closer to us) at all locations from the stellar position up to offsets of ~ 0\farcs3 and ~ 0\farcs6, respectively. In addition, the larger the distance from the star, the deeper and larger the velocity shift of the 300 km s-1 feature. These gradients could suggest that the outflowing gas between the observer and the continuum source (probably background dust), leading to this high-velocity feature, is probably collimated rather than isotropic at a distance of ~ 5x1015 cm (for an isotropic wind the deepest and bluest-shifted absortion is expected at the nebula center). We note, however, that other explanations may be possible. Extended emission in Hα , [OI]λ λ 6300,63, [NII]λ λ 6548,83, and [SII]λ λ 6316,31 is also detected from several outer (>2\arcsec) shock-excited knots in the nebula. In order to correctly interpret the complex He3-1475 spectra (that also include line and continuum scattered light) we intend to analyse the data through modelling of the spectral profiles considerig different geometries, kinematics and physical conditions in the gas. This work is partially funded through a NASA LTSA grant to R.S.

Canarias Pediatrica, 2010

... Clin Infect Dis 2009; 49:1.694-1.702. 9.Medina AM, Rivera FP, Romero LM, Kolevic LA, Castillo... more ... Clin Infect Dis 2009; 49:1.694-1.702. 9.Medina AM, Rivera FP, Romero LM, Kolevic LA, Castillo ME, Verne E, Hernandez R, Mayor YE, Barletta F, Mercado E, Ochoa TJ. ... Am J Trop Med Hyg 2010; 83:158-163. Theresa J. Ochoa 1,2, Carmen Contreras 1, Susan Mosquito 1 ...