Search PubMed⌕ Search

Biomedical subjects

C Vasquez

Publications and source records attributed to C Vasquez.

At least 19 recordsLinked to original sources
PubMed2002

Genetic toxicity of a standardized mixture of citrus polymethoxylated flavones.

Flavonoids are a ubiquitous family of phytochemicals that display a variety of biological effects, both beneficial and adverse depending on the individual compound. Certain flavonoids are genotoxic while others inhibit the genotoxicity of other mutagens. In the present studies, the mutagenicity of a mixture of polymethoxylated flavones (PMFs) purified from citrus peel oil was evaluated. The mixture consisted of nobiletin (32.5%), 3,3',4',5,6,7,8-heptamethoxyflavone (25.0%), tangeretin (14.0%), trimethylscutellarein (9.1%), sinensetin (3.9%), 5-demethyl-nobiletin (2.8%), hexa-O-methylquercetagetin (3.3%), 5-demethyl-tetramethylscutellarein (0.7%), 5-hydroxy-3,3',4',6,7,8-hexamethoxyflavone (0.7%), and a small quantity of unidentified flavonoid compounds (3.9%). In vitro addition of the PMF mixture over a concentration range that spanned four log doses (0.0005-5.0 mg/plate) did not reveal any evidence of mutagenicity in five bacterial tester strains (Salmonella typhimurium TA98, TA100, TA102, TA1535 and TA1537) either in the absence or presence of S9 activation. The PMF mixture exhibited a statistically significant increase in mutagenicity of L5178Y tk(+/-) mouse lymphoma cells at 0.05 (38.5 x 10(-6); P<0.05) and 0.1 mg/ml (61 x 10(-6); P<0.01) compared with vehicle-treated controls (mutation frequency=19.7 x 10(-6)). However, these responses were within historical values observed in negative control cultures and extremely small compared to the positive control (EMS 0.5 microl/ml; 1685.3 x 10(-6)). Furthermore, in the presence of S9 there was no indication of genetic toxicity in L5178Y tk(+/-) cells. These results demonstrate that the PMF mixture is not genotoxic in in vitro assay systems.

Animals↗
PubMed2001

Calculation of mitral regurgitant orifice area with use of a simplified proximal convergence method: initial clinical application.

To validate a previously proposed simplified proximal flow convergence method for calculating mitral regurgitant orifice area (ROA), a prospective study was conducted in ambulatory patients and in patients undergoing open heart surgery. Assuming a pressure difference between the left ventricle and left atrium of approximately 100 mm Hg (jet velocity [v(p)] 500 cm/s) and setting the color aliasing velocity (v(a)) to 40 cm/s, we simplified the conventional proximal convergence method formula (ROA = 2pi(r2)v(a)/v(p)) to r2/2, where r is the radius of the proximal convergence isovelocity hemisphere. For 57 ambulatory patients with a wide range of mitral regurgitant severity (1 to 4+), ROA was calculated by the conventional (x) and simplified (y) methods, demonstrating excellent accuracy (r = 0.92; P <.001; DeltaROA [y - x] = 0.004 +/- 0.08 cm2). For 24 intraoperative patients, ROA calculated by the simplified formula (y) correlated well with the pulsed Doppler-thermodilution method (x) (r = 0.84; P <.01; DeltaROA [y - x] = -0.002 +/- 0.08cm2). This simplified proximal convergence formula yields an accurate assessment of ROA for a wide range of regurgitant severity, while the time required for this measurement is shortened by half (1.5 +/- 0.5 minutes versus 3.2 +/- 0.7 minutes). This may increase the frequency of calculating ROA in the clinical laboratory.

Aged↗
PubMed2001

Characterization of enzootic foci of Venezuelan equine encephalitis virus in western Venezuela.

The distribution of the sylvatic subtype ID Venezuelan equine encephalitis (VEE) viruses in the lowland tropical forests of western Venezuela was investigated using remote sensing and geographic information system technologies. Landsat 5 Thematic Mapper satellite imagery was used to study the reflectance patterns of VEE endemic foci and to identify other locations with similar reflectance patterns. Enzootic VEE virus variants isolated during this study are the closest genetic relatives of the epizootic viruses that emerged in western Venezuela during 1992-1993. VEE virus surveillance was conducted by exposing sentinel hamsters to mosquito bites and trapping wild vertebrates in seven forests identified and located by means of the satellite image. We isolated VEE viruses from 48 of a total of 1,363 sentinel hamsters in two of the forests on six occasions, in both dry and wet seasons. None of the 12 small vertebrates captured in 8,190 trap-nights showed signs of previous VEE virus infection. The satellite image was classified into 13 validated classes of land use/vegetation using unsupervised and supervised techniques. Data derived from the image consisted of the raw digital values of near- and mid-infrared bands 4, 5, and 7, derived Tasseled Cap indices of wetness, greenness, and brightness, and the Normalized Difference Vegetation Index. Digitized maps provided ancillary data of elevation and soil geomorphology. Image enhancement was applied using Principal Component Analysis. A digital layer of roads together with georeferenced images was used to locate the study sites. A cluster analysis using the above data revealed two main groups of dense forests separated by spectral properties, altitude, and soil geomorphology. Virus was isolated more frequently from the forest type identified on flat flood plains of main rivers rather than the forest type found on the rolling hills of the study area. The spatial analysis suggests that mosquitoes carrying the enzootic viruses would reach 82-97% of the total land area by flying only 1-3 km from forests. We hypothesize that humans within that area are at risk of severe disease caused by enzootic ID VEE viruses. By contrast, equines could actually become naturally vaccinated, thus preventing the local emergence of epizootic IC VEE virus strains and protecting humans indirectly.

Animals↗
PubMed2001

Genetic diversity and relationships among Venezuelan equine encephalitis virus field isolates from Colombia and Venezuela.

During field studies of enzootic Venezuelan equine encephalitis (VEE) viruses associated with epizootic emergence, a large number of virus isolates were made in sylvatic foci of Venezuela and Colombia. To rapidly characterize these isolates, antigenic subtypes were determined by means of immunofluorescence and by single-strand conformational polymorphism (SSCP) analysis by use of an 856-bp fragment from the P62 gene, which we used to distinguish genetic variants. Representative isolates were sequenced to assess the sensitivity of SSCP to detect genetic differences. The SSCP analysis distinguished isolates differing by as little as 1 nucleotide; overall, differences of > or = 1 nucleotide were recognized 89% of the time, and the sensitivity to distinguish strains that differed by only 1 or 4 nucleotides was 17 and 57%, respectively. Phylogenetic analyses of representative sequences showed that all recent isolates from the Catatumbo region of western Venezuela and the middle Magdalena Valley of Colombia were closely related to epizootic subtype IAB and IC strains; strains from Yaracuy and Miranda States were more distantly related. Cocirculation of the same virus genotype in both Colombian and Venezuelan foci indicated that these viruses are readily transported between enzootic regions separated by > 300 km. The SSCP analysis appears to be a simple, fast, and relatively efficient method of screening VEE virus isolates to identify meaningful genetic variants.

Aedes↗
PubMed1999

Genetic and phenotypic changes accompanying the emergence of epizootic subtype IC Venezuelan equine encephalitis viruses from an enzootic subtype ID progenitor.

Recent studies have indicated that epizootic Venezuelan equine encephalitis (VEE) viruses can evolve from enzootic, subtype ID strains that circulate continuously in lowland tropical forests (A. M. Powers, M. S. Oberste, A. C. Brault, R. Rico-Hesse, S. M. Schmura, J. F. Smith, W. Kang, W. P. Sweeney, and S. C. Weaver, J. Virol. 71:6697-6705, 1997). To identify mutations associated with the phenotypic changes leading to epizootics, we sequenced the entire genomes of two subtype IC epizootic VEE virus strains isolated during a 1992-1993 Venezuelan outbreak and four sympatric, subtype ID enzootic strains closely related to the predicted epizootic progenitor. Analysis by maximum-parsimony phylogenetic methods revealed 25 nucleotide differences which were predicted to have accompanied the 1992 epizootic emergence; 7 of these encoded amino acid changes in the nsP1, nsP3, capsid, and E2 envelope glycoprotein, and 2 were mutations in the 3' untranslated genome region. Comparisons with the genomic sequences of IAB and other IC epizootic VEE virus strains revealed that only one of the seven amino acid changes associated with the 1992 emergence, a threonine-to-methionine change at position 360 of the nsP3 protein, accompanied another VEE virus emergence event. Two changes in the E2 envelope glycoprotein region believed to include the major antigenic determinants, both involving replacement of uncharged residues with arginine, are also candidates for epizootic determinants.

Amino Acid Sequence↗
PubMed1999

Natural rodent host associations of Guanarito and pirital viruses (Family Arenaviridae) in central Venezuela.

The objective of this study was to elucidate the natural rodent host relationships of Guanarito and Pirital viruses (family Arenaviridae) in the plains of central Venezuela. Ninety-two arenavirus isolates from 607 animals, representing 10 different rodent species, were characterized to the level of serotype. The 92 isolates comprised 19 Guanarito virus strains and 73 Pirital virus strains. The 19 Guanarito virus isolates were from Zygodontomys brevicauda; 72 (98.6%) of the 73 Pirital virus isolates were from Sigmodon alstoni. These results indicate that the natural rodent associations of these 2 sympatric arenaviruses are highly specific and that Z brevicauda and S. alstoni are the principal rodent hosts of Guanarito and Pirital viruses, respectively.

Animals↗
PubMed1997

Isolation and characterization of pirital virus, a newly discovered South American arenavirus.

Specific rodent species are principal hosts for each of the well-characterized members of the virus family Arenaviridae. Guanarito virus (Arenaviridae) is the etiologic agent of Venezuelan hemorrhagic fever. A previous study on the epidemiology of Venezuelan hemorrhagic fever revealed extensive arenavirus infection (presumed to be caused by Guanarito virus) in two rodent species. Sigmodon alstoni and Zygodontomys brevicauda, collected from the region of Venezuela in which the disease is endemic. In the present study, four arenavirus isolates recovered from the Municipality of Guanarito (two isolates each from S. alstoni and Z. brevicauda) were characterized to learn more about the natural rodent host relationships of Guanarito virus. Serologic tests and analyses of nucleocapsid protein gene sequence data indicated that the two isolates from Z. brevicauda are strains of Guanarito virus and that the two isolates from S. alstoni are representatives of a novel New World arenavirus (proposed name Pirital) that is antigenically and phylogenetically distinct from all known New World arenaviruses. The results of the present study provide further evidence that the cane mouse Z. brevicauda is a natural host of Guanarito virus and suggest that the cotton rat S. alstoni is the natural reservoir host of Pirital but not Guanarito virus.

Animals↗
PubMed1997

Ruptured aneurysm of the profunda femoral artery associated with polyaneurysmal disease.

A 73-year-old man was admitted for rupture of an atherosclerotic aneurysm of the profunda femoris artery associated to popliteal and bilateral axillary arteries aneurysms. The aneurysm of the profunda femoris artery was developed between the branches of the crural nerves. Considering the patency of the superficial femoral artery and of the leg arterie, and to avoid injury to the crural nerve, no reconstruction of the profunda femoris was attempted. The aneurysm was ligated proximally and buttress sutures were placed on the site of rupture to achieve thrombosis of the aneurysms. Most of the published cases of aneurysm of the profunda femoris artery are false aneurysms developed after various trauma. Atherosclerotic aneurysm of the profunda femoris artery is a rare lesion and rupture is exceptional.

Aged↗
PubMed1992

Evaluation of interceed(TC7) for reduction of postoperative adhesions in rabbits.

OBJECTIVE: To evaluate the effectiveness of Interceed(TC7) (Johnson and Johnson, New Brunswick, NJ) in the prevention of postoperative adhesions in a rabbit uterine horn model. Interceed(TC7) was tested in the presence and absence of absorbable suture. DESIGN, SETTING, PARTICIPANTS: Forty-one New Zealand white rabbits had lesions created on bilateral uterine horns at laparotomy. Lesions were randomly allocated to treatment with Interceed(TC7) or control. The effect of Interceed(TC7) was evaluated on sutured lesions (4-0 polyglactin 910; Ethicon, Inc., Somerville, NJ) as well as on open cut lesions (no sutures applied). MAIN OUTCOME MEASURES: Adhesion formation, using a grading system ranging from 0 to 3. RESULTS: Interceed(TC7)-treated animals in the sutured group (average adhesion score +/- SD = 2.15 +/- 1.3) did not differ from controls (average score +/- SD = 2.35 +/- 0.93) in adhesion formation, P = 0.47. Rabbits with open cut lesions treated with Interceed(TC7) (average adhesion score +/- SD = 1.89 +/- 1.1) did not differ from control animals (average score +/- SD = 1.83 +/- 1.2), P = 0.88. CONCLUSIONS: Interceed(TC7) was not an effective adhesioprophylactic agent in the presence or absence of nonreactive absorbable suture.

Animals↗
PubMed1991

The problem with interpreters: communicating with Spanish-speaking patients.

The information obtained from a non-English-speaking psychiatric patient through an untrained interpreter can be inaccurate and misleading. The authors briefly outline the most common errors that untrained interpreters make, including omission, addition, condensation, substitution, and role exchange. They present two case examples, one in which misinterpretation led to minimization of a patient's suicide attempt and the other in which a patient's suicidality was exaggerated. They conclude that clinicians should observe the behaviors of both the patient and the interpreter for indications of errors that might distort or obscure the communication.

Depressive Disorder↗
PubMed1985

Foot-and-mouth disease virus capsid proteins VP0, VP1 and VP3 synthesized by "in vitro" translation are the major components of 14S particles.

Translation of foot-and-mouth disease virus RNA in extracts of rabbit reticulocytes resulted in the synthesis and assembly of viral capsid protein into immature virion intermediate structures. The particles, which sedimented in the 14S zone of the sucrose gradient and contained only viral proteins VP0, VP1 and VP3 are believed to be pentameric associations of viral protomers.

Animals↗
PubMed1984

Electron microscopy mapping of Escherichia coli RNA polymerase-binding sites on plasmids from thermophilic bacteria.

The binding sites of Escherichia coli RNA polymerase to plasmid DNA from extremely thermophilic bacteria have been mapped by electron microscopy. Templates used in these studies included plasmids pTF62 (from Thermus flavus AT62) and pTT8 (from T. thermophilus HB8) and also hybrid molecules constructed by ligation of these plasmids to pBR322. Although the affinity of the enzyme for heterologous DNA was about one-third of that for pBR322, it was possible to localize preferred binding sites on pTF62 and pTT8. Six binding sites were identified in pTT8, mapping close to 7, 28, 47, 61, 65, and 81 map units (one unit being equal to 1% of the length of the DNA). Seven such regions located at 3, 27, 48, 60, 67, 81, and 86 map units were found in pTF62. RNA polymerase binding sites found in pBR322 coincided with promoters identified previously by electron microscopy analysis of transcriptional complexes prepared in vitro. These data indicate that E. coli RNA polymerase binds preferentially to specific sequences in plasmids from thermophilic bacteria, suggesting possible promoter locations in these plasmids.

Base Sequence↗
PubMed1984

Inactivation of foot-and-mouth disease virus vaccine strains by activation of virus-associated endonuclease.

A new inactivation process for foot-and-mouth disease virus (FMDV) has been developed. This process is based on the activation of the FMDV endonuclease by incubation of unfractionated viral suspension or purified virions at 37 degrees C in the presence of high concentrations of monovalent cations such as K+, Cs+ or NH4+ at pH 8.5. This procedure completely inactivated several FMDV vaccine strains yielding preparations having similar amounts of 140S particles to untreated controls. The inactivation followed first-order kinetics and the rate of inactivation was faster than that achieved with other agents, e.g. binary ethyleneimine. Testing in suckling mice or tissue culture revealed no residual infectivity after inactivation. Virus particles purified from inactivated preparations showed (i) the same sedimentation coefficient as non-inactivated preparations, (ii) electrophoretic patterns of their viral capsid proteins identical to those derived from non-inactivated preparations, and (iii) extensive degradation of the 35S viral RNA. This method is safer than inactivation with aziridines because only innocuous chemicals are used in the process.

Animals↗
PubMed1979

A new method for the isolation of undegraded FMDV-specific RNA from infected BHK cells.

Fractionation of Foot-and-Mouth disease virus infected cells by currently described procedures, leads to the appearance of variable amounts of heterogeneous single-stranded RNA fragments. A new method based upon the fractionation of cultured cells at extremely low temperatures has been developed to minimize the degradation of the viral RNAs by cellular nucleases. It was shown that the viral RNAs obtained by this procedure were almost non-degraded, and similar to those found in other picornavirus infected cells. More than 90 per cent of the polysomal RNAs were found as genome-size molecules, presumably being messenger RNA (mRNA). It was also found that the mRNA analyzed on sucrose gradients sedimented slightly ahead of the 35S genomic RNA. However, no differences were found when the analysis was performed on polyacrylamide gels.

Animals↗