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E Guzmán

Publications and source records attributed to E Guzmán.

At least 19 recordsLinked to original sources
PubMed2003

Remote sensing study of emissions from motor vehicles in the Metropolitan Area of Mexico City.

Remote sensing was employed for the first time to measure nitric oxide (NO) levels of on-road light-duty motor vehicles of the Metropolitan Area of Mexico City (MAMC). The sensor placed at 12 different sites also measured the concentration of CO2, CO, and total hydrocarbons (THC) in the exhaust emissions. A database was compiled containing 122 800 readings, of which 84 650 (69%) records were valid emissions measurements. CO, HC, and NO valid readings were 68.9, 63.4, and 62.9%, respectively, of the total attempted measurements. Furthermore, 42 822 vehicles were number-plate-matched to model year with the information provided by the Inspection/Maintenance Program. The mean emissions of total valid readings for CO, HC, and NO were determined to be 1.31 vol %, 440 ppm (propane), and 914 ppm, respectively. In 1991 and 1994, remote sensing measurements of CO and HC tailpipe emissions were performed in the MAMC in five different locations (30 000 valid readings). Large drops in both pollutants were observed for the intervening years, but sufficient vehicle information was not available at that time to fully explain the observed trends. Compared with those reports, our results point out to a steady decrease in CO and HC exhaust emissions with vehicle model year. The fleet emissions measured exhibit a gamma-distribution, with 10% of the most polluting fleet studied being responsible for 45%, 25%, and 29% of the CO, HC, and NO emissions, respectively. NO emissions in taxis are the highest among the vintage of vehicles, a matter of concern since according to the distance traveled per year, they represent 22% of the total activity in the MAMC.

Air Pollutants↗
PubMed2003

Evaluation of the vehicle inspection/maintenance program in the Metropolitan Area of Mexico City.

The Inspection/Maintenance Program in the Metropolitan Area of Mexico City (MAMC) mandates a test every 6 months for all gasoline motor vehicles as one of the strategies to decrease emissions of vehicular pollutants. FTP-75 and ASM procedures were performed in our facilities to a fleet of 108 in-use motor vehicles before and after the approval of the I/M mandatory test When our laboratory-simulated ASM data were compared with those of the official certificate, a large difference was observed between them. On the other hand, audits at the test-only centers indicate poor maintenance of the analytical instruments and dynamometers. On the basis of our FTP results, an estimation of the emissions change for the MAMC fleet shows a net 4% decrease in CO emissions, while total hydrocarbons and NOx increased 9 and 8%, respectively. Our results indicate that the I/M system in the MAMC lacks the technical capability and investment to ensure that software and hardware are properly maintained, calibrated, and upgraded. Sometimes limited attention is paid to ensure adequate training of inspectors, auditors, and quality control staff.

Air Pollutants↗
PubMed2001

Environmental implications on the oxygenation of gasoline with ethanol in the metropolitan area of Mexico City.

Motor vehicle emission tests were performed on 12 in-use light duty vehicles, made up of the most representative emission control technologies in Mexico City: no catalyst, oxidative catalyst, and three way catalyst. Exhaust regulated (CO, NOx, and hydrocarbons) and toxic (benzene, formaldehyde, acetaldehyde, and 1,3-butadiene) emissions were evaluated for MTBE (5 vol %)- and ethanol (3, 6, and 10 vol %)-gasoline blends. The most significant overall emissions variations derived from the use of 6 vol % ethanol (relative to a 5% MTBE base gasoline) were 16% decrease in CO, 28% reduction in formaldehyde, and 80% increase in acetaldehyde emissions. A 26% reduction in CO emissions from the oldest fleet (< MY 1991, without catalytic converter), which represents about 44% of the in-use light duty vehicles in Mexico city, can be attained when using 6 vol% ethanol-gasoline, without significant variation in hydrocarbons and NOx emissions, when compared with a 5% vol MTBE-gasoline. On the basis of the emissions results, an estimation of the change in the motor vehicle emissions of the metropolitan area of Mexico city was calculated for the year 2010 if ethanol were to be used instead of MTBE, and the outcome was a considerable decrease in all regulated and toxic emissions, despite the growing motor vehicle population.

Air Pollutants↗
PubMed2000

High-resolution localization of Drosophila Spt5 and Spt6 at heat shock genes in vivo: roles in promoter proximal pausing and transcription elongation.

Recent studies have demonstrated roles for Spt4, Spt5, and Spt6 in the regulation of transcriptional elongation in both yeast and humans. Here, we show that Drosophila Spt5 and Spt6 colocalize at a large number of transcriptionally active chromosomal sites on polytene chromosomes and are rapidly recruited to endogenous and transgenic heat shock loci upon heat shock. Costaining with antibodies to Spt6 and to either the largest subunit of RNA polymerase II or cyclin T, a subunit of the elongation factor P-TEFb, reveals that all three factors have a similar distribution at sites of active transcription. Crosslinking and immunoprecipitation experiments show that Spt5 is present at uninduced heat shock gene promoters, and that upon heat shock, Spt5 and Spt6 associate with the 5' and 3' ends of heat shock genes. Spt6 is recruited within 2 minutes of a heat shock, similar to heat shock factor (HSF); moreover, this recruitment is dependent on HSF. These findings provide support for the roles of Spt5 in promoter-associated pausing and of Spt5 and Spt6 in transcriptional elongation in vivo.

Animals↗
PubMed2000

[Familial recurrence of non syndromic cleft lip with or without cleft palate in Chilean populations].

BACKGROUND: The presence of major genes in the susceptibility of non syndromic cleft lip with or without cleft palate (CL/P) in Chile has been postulated, considering the high prevalence and familial aggregation of this condition. AIM: To study the familial recurrence of CL/P in Chile. PATIENTS AND METHODS: The recurrence risk of CL/P was studied in 217 extended pedigrees where 33 (15.2%) were multiplex (21 male and 12 female propositi). These multiplex extended pedigrees (with more than one affected individual) represented 75 nuclear pedigrees, constituted by 840 males and 803 females and are the basic information of this study. RESULTS: A significantly higher frequency of affected males (4.15%) than affected females (2.27%) was observed, independent of the difference in number of propositi by sex. Even though no differences were observed between families where both parents were unaffected, compared to those with only one affected parent, a higher proportion of affected descendants was found when the affected propositi was the mother. In multiplex families, the recurrence risk, according to the genetic proximity to the proband, was 10.1, 3.6 and 3.3% respectively for first, second and third degree relatives. The figures were 1.5, 0.5 and 0.4% respectively, when adjusted to the 217 extended pedigrees. Considering that the risk for the general population in Chile is approximately 0.16%, it is 10.3, 3.2 and 2.6 times higher among affected families. CONCLUSIONS: The high heritability of CL/P and the risk encountered for the Chilean population supports the hypothesis of major genes involved in its susceptibility.

Chile↗
PubMed1999

Transcription factor TFIIH is required for promoter melting in vivo.

The Rad25 protein in yeast is a DNA helicase and a subunit of the general transcription factor TFIIH. While in vitro studies have led to the hypothesis that TFIIH helicase activity plays a role in promoter melting, in vivo tests are lacking. Using potassium permanganate, which preferentially modifies single-stranded DNA, we show that a temperature-sensitive rad25(ts) mutant severely reduces the normally extensive promoter melting observed in vivo on the highly expressed genes TDH2 and PDC1 and on the induced heat shock gene HSP82. Loss of promoter melting can be observed in as little as 30 s after a shift to the nonpermissive temperature and is accompanied by a dramatic reduction in transcription. These effects on the promoter are specific, since the mutation does not affect TATA box occupancy or, in the case of HSP82, recruitment of TATA-binding protein to the TATA element or that of heat shock factor to heat shock elements. Additionally, using the technique of formaldehyde cross-linking coupled with restriction endonuclease cleavage and ligation-mediated PCR, we were able to map the polymerase density on the promoter of HSP82. This high-resolution mapping allowed us to determine that the polymerase II (Pol II) density on the promoter is also dramatically reduced after inactivation of TFIIH. These data provide strong support for the hypothesis that TFIIH functions with Pol II in the transcriptionally required step of promoter melting and show, surprisingly, that the extent of TFIIH-dependent promoter melting observed in vivo is several times larger than that seen in vitro.

DNA Helicases↗
PubMed1995

[Experience with bladder-amniotic shunts].

Four bladder-amniotic shunts were done in three fetuses with megacystis. The procedure was successful in all cases on the first attempt. The interval between the shunt insertion and delivery was range from three to twenty eight days. Pulmonary and renal damage were irreversible in two fetuses. Spontaneous abortion occurred with the third fetus which had multiple malformations. We believe that selection of candidates for such procedures should be improved. Early diagnosis and referral to high technology centers will increase clinical experience.

Adult↗
PubMed1994

Purification and characterization of O-acetylserine sulfhydrylase isoenzymes from Datura innoxia.

Three isoenzyme forms (designated A, B, and C) of O-acetylserine sulfhydrylase were purified from Datura innoxia suspension cultures. Isoenzyme A is the most abundant form, comprising 45-60% of the total activity. Isoenzymes C and B comprise 35-40% and 10-20% of the activity, respectively. The specific activities of the purified isoenzymes are similar (870-893 mumol of cysteine/min/mg of protein). Molecular masses for isoenzymes A, B, and C, estimated by analytical size exclusion high performance liquid chromatography, are 63, 86, and 63 kDa, respectively. Isoenzymes A and B are homodimers; isoenzyme C is a heterodimer. Spectral analysis indicates that these isoenzymes possess a pyridoxal 5'-phosphate cofactor that binds the O-acetylserine substrate. Binding is reversible by addition of the sulfide substrate. The O-acetylserine sulfhydrylase isoenzymes are active over a broad temperature range, with maximum activity between 42 and 58 degrees C. They are active only between pH 7 and 8, with optimal activity at pH 7.6. Kinetic analysis indicates these enzymes are allosterically regulated and exhibit positive cooperativity with respect to both substrates. They are inhibited by sulfide concentrations above 200 microM. The kinetic analysis together with the physical and spectrophotometric characteristics indicate that the O-acetylserine sulfhydrylase enzymes have two active sites.

Cells, Cultured↗
PubMed1992

[Nutritional changes caused by the germination of legumes commonly eaten in Chile].

The changes promoted by germination on phytates, oligosaccharides, crude protein, amino acids and riboflavin contents of black and white cultivars of beans, lentils, chicken-pea and peas, were studied. Seeds germination was carried out in darkness at 25 degrees C and 85% RH during 72 hours, previously soaked overnight in a solution of sodium hypochlorite at a concentration of 50 ppm. Germination capacity was assessed by determining hypocotyl and epicotyl lengths and percent of sprouted seed. The seeds were milled and freeze-dried for the chemical analysis. Germination promoted a significant increase in crude protein content and reduction also significant in phytates levels. These changes were attributed to an increase of proteases and phytase activities. In fact, this enzyme would make a solubilization of phytates and would release soluble protein and minerals. A significant reduction of flatulence oligosaccharides took place, which was also explained by an increase of alpha-galactosidase concentration. Sprouted seeds showed a higher content of almost all amino acid than crude legumes, although this change was variable. Significant increase of riboflavin was also found. Finally, germination decreased ashes and fat contents. These findings were determined in all legumes, although both cultivars of beans showed a higher response to the biochemical changes.

Amino Acids↗
PubMed1991

Nutritional quality of lupine (Lupinus albus cv. Multolupa) as affected by lactic acid fermentation.

The effects of selected NRRL strains of Lactobacillus acidophilus, L. buchneri, L. cellobiosus and L. fermentum upon oligosaccharide, phytate and alkaloid contents, as well as on the nutritive value of lupine, were investigated. Lupine was processed to a 12% total solids suspension, inoculated with 1% (v/v) cultures and fermented until a final desired pH of 4.5. L. acidophilus B-2092 and L. buchneri B-1837 growth was related to a significant sucrose breakdown and decreases of phytates, whereas L. acidophilus B-1910 and L. fermentum B-585 reduced the content of flatulence oligosaccharides. The activity of L. acidophilus B-1910 was particularly associated with lowering of alkaloids and increase of riboflavin. Lactic acid fermentation produced slight changes in lysine and methionine contents. No significant differences in net protein ratio values and protein digestibility were found between fermented and unfermented lupine (P less than 0.05). A 1:1 ratio mixture of B-1910 and B-2092 strains of L. acidophilus lead to a final fermented lupine with nutritional advantages to those given by the individual cultures.

Alkaloids↗
PubMed1990

Heavy metals, chlorine and antibiotic resistance in Escherichia coli isolates from ambulatory patients.

The susceptibility of Escherichia coli strains isolated from ambulatory patients to heavy metals, chlorine and antibiotics was evaluated. It seemed that heavy metal resistance was associated with antibiotic resistance. On the other hand, chlorine resistant strains seemed to be more sensitive to antibiotics. Clinical and ecological implications of these results are discussed.

Ambulatory Care↗
PubMed1989

[Sweet lupine (Lupinus luteus, var. Aurea/Weico and Lupinus albus, var. Multolupa) proteins. I. Extraction and filtration by Sephadex].

Samples of Lupinus luteus, var. Aurea/Weico and Lupinus albus var. Multolupa flours were analyzed. The flour proteins were extracted and fractionated by gel filtration, and the per cent pattern for both globulins and albumins was then determined. The dehulled seeds, previously analyzed for composition, were ground, defatted and consecutively extracted with distilled water (pH 5.0) and phosphate buffer (0.05 M, pH 8.5). The extracted protein content was measured by the Lowry simplified method. Globulins (pH 8.5 fraction) from both species were filtered through Sephadex G-100; besides, Lupinus albus globulins were filtered through Sephadex G-150, and absorbance of the collected fractions was measured at 280 nm. The dehulled seed (DS) of L. luteus and L. albus revealed a good protein content (58.2 and 41.0%, respectively). The protein extracted from L. luteus was constituted by 17% albumins and 58.4% globulins. In contrast, L. albus presented a higher albumin content (55.6%) than globulins (31.5%). The elution pattern for the Sephadex G-200 gel filtration showed for both lupine species analyzed a preponderant peak I corresponding in L. luteus to 55.0% and in L. albus to 84.1% of the total globulins content. From these results, it may be concluded that the dehulled seed protein content is 42.0% higher for the L. luteus sample than for the L. albus. The applied methodology indicated a predominant content of globulins above albumins in L. luteus, while in the case of L. albus, the albumin content was the highest.

Albumins↗
PubMed1989

[Sweet lupine (Lupinus luteus, var. Aurea/Weico and Lupinus albus, var. Multolupa) proteins. II. Separation by electrophoresis].

The albumins and globulins extracted from Lupinus luteus var. Aurea/Weico and Lupinus albus var. Multolupa defatted flour samples were analyzed by polyacrilamide gel electrophoresis. The purpose was to determine the percentage distribution of pattern in the electrophoretograms and the relative mobility values of protein. The L. luteus albumins densitogram showed six fractions, two of them, No. 2 and No. 4, represented 58.1% of the total. On the other hand, the globulins densitogram revealed five fractions, numbers 1, 2 and 3 representing 90.7%. The densitogram of peak I from Sephadex G-100 globulins filtration indicated two fractions similar to those number 1 and 2 of the total globulins, showing low relative mobility values (from 0.26 to 0.39). The L. albus albumins resolved in four fractions, with No. 2 being the most prevalent (54.3%). In regard to the L. albus globulins, these showed five fractions identical in distribution with those of peak I, fraction 2 appearing as the most important (48.2%). It was found that Sephadex G-100 did not perform a good separation. As to the relative mobility values of globulins, fractions 2 and 3 were the most prominent (relative mobility of 0.35 and 0.48, respectively). It may be concluded that L. luteus albumins presented more components but with lower relative mobility values than those of L. albus. As for the globulins from both lupine flour samples, the gel separated fractions were classified in two groups of components, those of high and of low relative mobility.

Albumins↗
PubMed1989

[Preliminary experience in fetal blood obtainment through cord punction].

Seven umbilical cord punctures where done in viable fetuses. The procedure was successful in all cases, the fetuses had anomalies or non immune hydrops fetalis. There was one case in which the indication was autoimmune thrombocytopenic purpura. There is high risk in the punction, but the prenatal diagnostic studies is necessary and useful. The authors comment advantages and complications in this procedure.

Anencephaly↗
PubMed1989

[Doppler in 42 high risk pregnancies: predictive values of the flow velocity wave indexes in the arcuate and umbilical arteries].

Doppler exams were done in forty two risk pregnancy. We explored arcuate and umbilical arteries in order to determine the predictive values of different index in flows velocity wares. Method sensibility was 83.33% y 100% in arcuate and umbilical arteries respectively. Specificity was 100% and 94.9% predictive value of negative test was 97.24 y 100% in both arteries. Predictive value of positive test was 100% and 71.42% in both arteries. The results are very similar to others scientific reports in the same subject.

Adult↗