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R Quintero

Publications and source records attributed to R Quintero.

35 records · Page 2Linked to original sources
PubMed1992

The delta-endotoxin protein family displays a hydrophobic motif that might be implicated in toxicity.

A computer-based analysis of hydropathy and surface probability of representative members of each class of the Cry family of proteins was performed. A highly conserved hydrophobic motif within the previously described block, D2, is present not only in lepidopteran toxin genes but also in toxins active against diptera and coleoptera. An interesting feature of this hydrophobic motif is the presence of an aspartic residue (highly hydrophilic) in its middle part. Comparison with the amino acid sequence from diphtheria toxin showed that it also contains a hydrophobic motif similar to the one present in the Bacillus thuringiensis toxins. It also contains an aspartic residue in the middle part and some speculations are presented on the function of this specific region with regard to the toxic mechanism of action.

Amino Acid Sequence↗
PubMed1991

Amniotic fluid white blood cell count: a rapid and simple test to diagnose microbial invasion of the amniotic cavity and predict preterm delivery.

The purpose of this study was to determine the value of amniotic fluid white blood cell count in the diagnosis of microbial invasion of the amniotic cavity. Amniotic fluid was retrieved by amniocentesis from 195 patients with preterm labor and intact membranes. Fluid was cultured for aerobic and anaerobic bacteria, as well as for mycoplasmas. The prevalence of a positive amniotic fluid culture was 12.8% (25/195). Patients with a positive amniotic fluid culture had a significantly higher median amniotic fluid white blood cell count than did patients with a negative amniotic fluid culture (median, 6 cells/mm3; range, 0 to 11,000 cells/mm3 vs median, 320 cells/mm3; range, 1 to 4480 cells/mm3; p less than 0.0001). An amniotic fluid white blood cell count greater than or equal to 50 cells/mm3 had a sensitivity of 80% (20/25), a specificity of 87.64% (149/170), a positive predictive value of 48.78% (20/41), and a negative predictive value of 96.75% (149/154) in the detection of a positive amniotic fluid culture for microorganisms. Although the sensitivity of an amniotic fluid white blood cell count (greater than or equal to 50 cells/mm3) in the detection of microbial invasion of the amniotic cavity was greater than that of the Gram stain of amniotic fluid (80% [20/25] vs 48% [12/25]; p less than 0.05), the specificity was lower (87.64% [149/170] vs 98.8% [168/170]; p less than 0.05). However, 88% (15/17) of all patients with an amniotic fluid white blood cell count greater than or equal to 50 cells/mm3 and a negative amniotic fluid culture had a spontaneous preterm delivery. We conclude that the amniotic fluid white blood cell count is a sensitive, simple, and inexpensive test for the detection of microbial invasion of the amniotic cavity. An elevated amniotic fluid white blood cell count is a risk factor for preterm delivery.

Adult↗
PubMed1991

Design of two immobilized cell catalysts by entrapment on gelatin: internal diffusion aspects.

Experimental results obtained during the design of two immobilized cell catalysts by entrapment on gelatin are presented. Strong diffusional limitations are found and explained with the usual parameters and models, introducing an empirical correlation between substrate concentration and effectiveness factor. The effect of particle size, enzyme load, and specific activity in the system is discussed in terms of cooperation between bioengineers and geneticists.

Catalysis↗
PubMed1990

Microbial sensor for penicillins using a recombinant strain of Escherichia coli.

E. coli harboring the multicopy plasmid pBR327, which codes for beta-lactamase synthesis, was immobilized on acetylcellulose membranes. These were placed in the vicinity of a flat pH electrode, thus constituting a penicillin biosensor based on the detection of changes in pH using a reference pH electrode. A response time of 8 min was obtained with at least 2 mg of cells cm-2 of membrane. A linear detection range between 5 and 30 mM of penicillin was achieved. Buffering capacity decreased the sensitivity, but to a lower extent as when compared with probes using purified enzyme. The sensor was completely stable for at least 13 days and proved to be useful for penicillin estimation in complex media such as fermentation broths and milk.

Biosensing Techniques↗
PubMed1989

Diagnosis of intra-amniotic infection: the acridine orange stain.

The rapid diagnosis of intra-amniotic infection in patients with premature rupture of the membranes (PROM) and preterm labor is of utmost importance. The Gram's stain examination of amniotic fluid can only detect half of these infections. The acridine orange (AO) stain has been claimed to be superior to the Gram's stain in the detection of bacteria in biologic fluids. Therefore, we undertook the present study to examine the value of AO in the detection of bacteria in amniotic fluid. One hundred and thirty-eight patients with a culture-documented prevalence of intra-amniotic infection of 23.2% were studied. The diagnostic indices of the AO were: sensitivity, 43.8%, specificity, 97.2%, positive predictive value, 82.8%, and negative predictive value, 85.1%; the diagnostic indices for the Gram's stain were: sensitivity, 46.8%, specificity, 98.1%, positive predictive value, 88.2%, and negative predictive value, 85.9%. There was no difference in the diagnostic values of the tests. The agreement between the two techniques was substantial, as indicated by a kappa index of 0.72 (SE = 0.17, p less than 0.001). The AO offered no significant advantage over the Gram's stain examination of amniotic fluid in the detection of intra-amniotic infection. However, the AO stain was able to identify mycoplasma infections that escaped detection by the Gram's stain. Therefore, the AO is presently the only microscopic technique capable of detecting mycoplasma in amniotic fluid.

Acridine Orange↗
PubMed1988

The value and limitations of the Gram stain examination in the diagnosis of intraamniotic infection.

Gram stain examination of amniotic fluid is a method used for the rapid diagnosis of intraamniotic infection in patients with preterm premature rupture of membranes and preterm labor. The management of these patients relies heavily on the Gram stain results. Therefore, it is critical that the diagnostic value and limitations, optimal technique, and outcome correlates be precisely established. Most studies have focused on culture results rather than on Gram stain results to describe neonatal and maternal outcome. However, management is based on the Gram stain because culture results are not immediately available. One hundred eighty-seven amniocenteses were performed in 131 patients with preterm premature rupture of the membranes (n = 90) and preterm labor (n = 41). Spun and unspun Gram stains were performed. Centrifugation of the sample did not improve the sensitivity of the technique significantly. The agreement between the two methods was substantial (kappa index 0.89, p less than 0.001). The sensitivity of the Gram stain was 44.8% and the specificity was 97.6%. The sensitivity of the Gram stain was directly proportional to the number of bacteria present in amniotic fluid. In the presence of greater than 10(5) colony forming units per milliliter, 80% of the Gram stains were positive. The absence of both bacteria and white blood cells in a smear was associated with a negative culture of amniotic fluid in 95% of the cases. Clinical chorioamnionitis was associated with a positive Gram stain of amniotic fluid (p less than 0.001). There was a trend toward a higher incidence of endometritis in patients with a positive Gram stain compared with those with a negative Gram stain (p = 0.07). There was no neonatal infectious morbidity in patients with a true negative Gram stain. Patients with a false negative Gram stain had a 25% incidence of neonatal infectious complications (proved and suspected sepsis).

Adult↗
PubMed1988

Intraamniotic infection and the onset of labor in preterm premature rupture of the membranes.

The purpose of this study was to examine the relationship between intraamniotic infection and the onset of labor in patients with preterm premature rupture of the membranes. Two hundred and thirty consecutive patients were admitted with premature rupture of the membranes to Yale-New Haven Hospital from January 1985 to July 1987. Amniotic fluid was retrieved by amniocentesis from 96% (221/230). Sixty-one patients were in labor on admission (27.6%, 61/221) and 39% of them (24/61) had a positive amniotic fluid culture. Patients in labor on admission were more likely to have a positive amniotic fluid culture than those who were not in labor on admission (24/61 versus 41/160, p = 0.049). Of the 160-patients who were not in labor on admission, 81 subsequently went into spontaneous labor; microbiologic information at the time of labor was known in 48 of these patients (59.2%). Seventy-five percent (36/48) of these patients had a positive amniotic fluid culture. The incidence of intraamniotic infection in quiescent women who subsequently went into labor was higher than that of patients admitted in active labor (75% versus 39%, p = 0.0004). These results provide a basis for the clinical impression that the onset of labor in women with preterm premature rupture of the membranes is associated with a subclinical intraamniotic infection. The mechanisms responsible for the onset of labor in women without an intraamniotic infection may be associated with an extraamniotic infection (e.g., deciduitis) or a noninfectious process.

Amniotic Fluid↗
PubMed1987

Arachidonate lipoxygenase metabolites in amniotic fluid of women with intra-amniotic infection and preterm labor.

This study was undertaken to examine the effects of intrauterine infection and preterm labor on the amniotic fluid concentrations of arachidonate lipoxygenase metabolites in women with premature rupture of membranes. Amniotic fluid was obtained from four groups of women with premature rupture of membranes: group 1, women without labor or infection; group 2, women with labor but without infection; group 3, women with intra-amniotic infection but without labor; and group 4, women with both infection and labor. 12-Hydroxyeicosatetraenoic acid, 15-hydroxyeicosatetraenoic acid, and leukotriene B4 were measured by radioimmunoassays. Amniotic fluid concentrations of 12-hydroxyeicosatetraenoic acid were found not to differ significantly among the four groups. Amniotic fluid concentrations of 15-hydroxyeicosatetraenoic acid in group 4 were significantly higher than in women in groups 1 and 3 (p less than 0.05). In addition, amniotic fluid concentrations in leukotriene B4 were significantly higher in group 4 than in any of the other three groups (p less than 0.05). Leukotriene B4 concentrations were higher in groups 2 and 3 than in group 1, suggesting that the presence of both labor and infection increases the concentration of this metabolite in amniotic fluid. Infection and labor had an additive effect in the elevation of amniotic fluid concentrations of leukotriene B4. These results suggest that the amniotic fluid concentrations of arachidonate lipoxygenase metabolites are affected differently by the presence of infection and labor in women with premature rupture of membranes.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1987

Prostaglandin concentrations in amniotic fluid of women with intra-amniotic infection and preterm labor.

This study was undertaken to examine the effects of intrauterine infection and preterm labor on the amniotic fluid concentrations of prostaglandins in women with premature rupture of the membranes. Amniotic fluid was obtained from four groups of patients with premature rupture of the membranes: group 1, patients without labor or infection; group 2, patients with labor but without infection; group 3, patients with an intra-amniotic infection but without labor; group 4, patients with both infection and labor. Prostaglandins E2 and F2a were measured by radioimmunoassays. Preterm labor, in the absence of infection, was not associated with significant increases in amniotic fluid concentrations of prostaglandins. Women with preterm labor and intra-amniotic infections had higher amniotic fluid concentrations of prostaglandins than women with preterm labor in the absence of infection or women with intra-amniotic infection in the absence of labor. These observations are compatible with the participation of prostaglandins in the mechanisms of onset of preterm labor associated with intra-amniotic infection.

Adult↗
PubMedDate not supplied

Endoscopic documentation of unintentional perforation of the dividing membrane during amnioreduction for twin-twin transfusion syndrome.

OBJECTIVE: The purpose of this report is to document endoscopically the occurrence of unintentional piercing of the dividing membrane in a monochorionic twin pregnancy with twin-twin transfusion syndrome (TTTS). MATERIALS AND METHODS: The dividing membrane was visualized endoscopically during laser therapy in a patient with TTTS who had previously undergone therapeutic amniocentesis. The donor twin had no visible bladder, but the amniotic fluid volume had normalized after amniocentesis. RESULTS: The suspected membrane perforation was identified endoscopically during laser surgery. Five areas of vascular communications were identified and photocoagulated. CONCLUSIONS: Sonographic evidence of normalization of the amniotic fluid volumes after therapeutic amniocentesis with persistent nonvisualization of the bladder of the donor twin should not be interpreted as a sign of improvement of TTTS, but rather as indirect evidence of unintentional perforation of the dividing membrane. This complication can be confirmed endoscopically.

Adult↗
PubMedDate not supplied

In utero fetal urine analysis and renal histology correlate with the outcome in fetal obstructive uropathies.

We evaluated 8 second-trimester fetuses who had undergone termination because of obstructive uropathies and correlated the renal histopathology with fetal urine biochemical prognostic parameters. Prenatal evaluation included serial vesicocentesis, karyotyping, and sonography. According to the urinary biochemical parameters, 3 fetuses were classified to be in the good prognostic category, 2 in the borderline prognostic category, and 3 in the poor prognostic category. The kidneys were evaluated both grossly and microscopically for hydronephrosis, pelvicaliceal dilatation, cystic changes and fibrosis. Fetuses in the poor prognostic category had severely damaged renal architecture, microcysts, macrocysts, and extensive fibrosis. Fetuses in the good prognostic category had minimal histopathologic changes with preservation of the architecture. Fetuses in the borderline category showed a moderate degree of renal damage but with focally preserved architecture. We conclude (1) that there is a direct correlation between elevation in urinary electrolytes and proteins and extent of underlying renal histopathological damage and (2) that appropriate detailed prenatal evaluation of the renal function can identify fetuses who could potentially benefit from in utero therapy.

Calcium↗
PubMedDate not supplied

Looking for "indicants" in the differential diagnosis of jaundice.

The differential diagnosis between intra- and extrahepatic causes of jaundice was studied. At the "20 Noviembre" ISSSTE Hospital in Mexico City, between January 1977 and May 1984, data were collected in 1,263 jaundiced patients. To the clinical data for 1,000 of these 1,263 patients and a new set of 105 jaundiced patients, the COMIC study group algorithm was applied. The differential diagnosis between medical and surgical causes of jaundice was correct in 90% of the cases. In 85% the algorithm could also differentiate between acute and chronic disease, or between benign and malignant causes of jaundice. The COMIC algorithm was then modified and applied to the same 1,000 cases examined previously, with 96% accuracy in distinguishing medical and surgical causes of jaundice and 94% accuracy in discriminating between acute and chronic, or benign and malignant, disease. In a new set of 105 cases of jaundiced patients the modified COMIC algorithm made the correct diagnosis between intra- and extrahepatic causes for 98% of the patients, and for 93% it was also capable of distinguishing benign from malignant and acute from chronic causes of jaundice.

Adult↗