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Biomedical subjects

M D Romero

Publications and source records attributed to M D Romero.

17 recordsLinked to original sources
PubMed2006

A kinetic study of isoamyl acetate synthesis by immobilized lipase-catalyzed acetylation in n-hexane.

The objective of this work was to propose a reaction mechanism and to develop a rate equation for the synthesis of isoamyl acetate by acylation of the corresponding alcohol with acetic anhydride using the lipase Novozym 435 in n-hexane. The reaction between isoamyl alcohol and acetic anhydride occurred at high rate in first place. Then, if excess alcohol was used, produced acetic acid further reacted with remaining alcohol, leading to yields higher than 100% (based on initial acetic anhydride content). This reaction was much slower and took place only when acetic anhydride had been totally consumed. Optimal pH for Novozym 435 was 7.7. Acetic acid strongly inactivated the enzyme but it was partially caused by the pH drop in the biocatalyst aqueous microenvironment. Acetic anhydride also showed an important inhibition effect. On the contrary, isoamyl alcohol and isoamyl acetate had no negative effect on the lipase. The analysis of the initial rate data showed that reaction followed a Ping-Pong Bi-Bi mechanism with inhibition by acetic anhydride. The kinetic constants were obtained by multiple regression analysis of experimental findings. Equation predictions and experimental reaction rate values matched very well at conditions where acetic acid concentration in the medium was low.

Acetic Acid↗
PubMed2003

Biochemical and genetic studies of two Heterodera avenae resistance genes transferred from Aegilops ventricosa to wheat.

Two Heterodera avenae resistance genes, Cre2 from Aegilops ventricosa AP-1 and Cre5 from Ae. ventricosa #10, were shown to confer a high level of resistance to the Spanish pathotype Ha71. No susceptible plants were found in the F(2) progeny from the cross between the two accessions of Ae. ventricosa, suggesting that their respective resistance factors were allelic. However, genes Cre2 and Cre5 apparently were transferred to a different chromosomal location in the wheat line H-93-8 and in the 6M(v)(6D) substitution, respectively, as proved by F(2) segregation of their cross progeny. The induction of several defence responses during early infection by the same H. avenae pathotype in resistant lines carrying Cre2 or Cre5 genes was studied. Isoelectrofocusing (IEF) isozyme analysis revealed that peroxidase, esterase and superoxide dismutase activity increased after nematode infection, in roots of resistant lines in comparison with their susceptible parents. Differential induced isoforms were also identified when IEF patterns of resistant lines were compared. A DNA marker, absent in Cre5-carrying genotypes, was found to be linked, thought not very tightly, to the Cre2 gene in the H-93-8 line. The differences observed between the Cre2 and Cre5 genes with respect to their chromosomal location in wheat introgression lines, de-toxificant enzyme induction and behaviour against different pathotypes, suggest they are different H. avenae resistance sources for wheat breeding.

Animals↗
PubMed2001

Influence of canal paresis and compensation on gain and time constant of nystagmus slow-phase velocity to yaw-axis rotation.

In order to assess the influence of canal paresis and compensation on the yaw-axis rotatory chair test parameters gain and time constant, a study was conducted in 435 patients diagnosed with unilateral peripheral vestibulopathy. Patients were grouped according to the amount of canal paresis found in the caloric test and by the result of a bedside examination of the vestibulo-ocular reflex (VOR). The time constant of the VOR diminishes as canal paresis increases and, when using a high-velocity sinusoidal test, there is a similar reduction in gain. Mean time constant was reduced when rotations were to the side of the lesion (ipsilesional) and to the normal (contralesional) and differences between both rotations were found for 21-80%, canal paresis. Ipsilesional gain was significantly less than contralesional gain, which had a normal result independent of the amount of canal paresis; differences between them were significant when canal paresis was > 41%. Spontaneous nystagmus significantly influenced the appearance of asymmetries in gain and time constant in the tests performed while, with high-velocity sinusoidal rotation, gain was found to be significantly different for ipsilesional and contralesional rotations in non-acute symptomatic patients.

Adolescent↗
PubMed1998

[Caudal regression syndrome].

INTRODUCTION: The regression caudal syndrome includes a spectrum of malformations which vary from the symptomless coccygeal agenesis until thoracic vertebrae and sacrococcygeal agenesis with severe neurological deficit; it is associated sometimes with malformations in other organs and systems. We present a case of partial agenesis of sacro and coccix with neuromuscular, sphincter and orthopedist alterations. CLINICAL CASE: A 4-year-old patient consults because of walk alterations, with daytime and nocturnal enuresis and urinary incontinence, constipation/encopresis and rectal prolapse. Familiar and personnel precedents are uninteresting. She began to walk at normal age, referring only rectal prolapse with constipation from nursing and urinary tract infections and encopresis when she was 3 years old, with normal complementary explorations (digestive and nephrourologyc). She presents in lumbosacral X-rays four lumbar vertebrae, a dysplasic sacro and absence of coccix. Hypoplasy of sacro with bilateral stenosis of the pelvis and coxa vara in both femurs are seen in the lumbar CT. In RMI is observed agenesis of sacro and coccix vertebrae. CONCLUSIONS: There are a wide variety of sacrococcygeal agenesis, which are classified by Renshaw and modified by Pang. As etiologics factors we find the gestational diabetes, in addition to genetic factors. The clinic exploration guides us toward a flaccid paraparesia/areflexia, with orthopaedist alterations, sometimes of artrogripotyc type. With image techniques (X-rays, CT, MRI) we can accomplish the diagnosis and we can discard or demonstrate associated medullary anomalies. We concluded that in all patient with alterations of walk and/or lack of sphincters control we should explore the lumbosacral region searching for medulodiysplasic or vertebral alterations.

Abnormalities, Multiple↗
PubMed1996

Applications of laser-induced breakdown spectrometry (LIBS) in surface analysis.

The applicability of laser-induced breakdown spectrometry (LIBS) for surface analysis is presented in terms of its lateral and depth resolution. A pulsed N(2) laser at 337.1 nm (3.65 J/cm(2)) was used to irradiate solar cells employed for photovoltaic energy production. Laser produced plasmas were collected and detected using a charge-coupled device. An experimental device developed in the laboratory permits an exact synchronization of sample positioning using an XY motorized system with laser pulses. Multielement analysis with lateral resolution of up to 30 microm is feasible with the present system. Three-dimensional capabilities of the system are used for studies on the distribution of carbon impurities at the surface of the solar cells.

Journal Article↗
PubMed1996

Analysis of Heterodera avenae populations by the random amplified polymorphic DNA technique.

Eleven populations of the Heterodera avenae complex (four Spanish, two British, two French, and three Swedish) were studied by random amplified polymorphic DNA analysis. From 5 to 11 fragments were obtained with each of 14 random primers, with fragment size ranging from 200 to 2200 bp. Cluster analysis of the 11 populations, using 108 scorable markers, separate these populations into two main groups. These groups coincide with what is known as the "true" H. avenae and the "Gotland strain" or "British pathotype 3" of H. avenae. The results also clarify the relationships among some members of the H. avenae complex established previously using morphological and biochemical criteria.

Animals↗
PubMed1995

Intravenacaval membrane oxygenation and carbon dioxide removal in severe acute respiratory failure.

STUDY OBJECTIVE: To characterize the physiologic response to, and safety of, intravenacaval membrane oxygenation and carbon dioxide removal. DESIGN: Interventional before-after study. SETTING: University teaching hospital ICU. PATIENTS: Twenty-two patients with severe acute respiratory distress syndrome (ARDS). INTERVENTIONS: Implantation of a hollow-fiber membrane oxygenator (IVOX; CardioPulmonics; Salt Lake City, Utah) into the superior and inferior venae cavae by venotomy of the right femoral or right internal jugular vein for a duration of up to 20 days. MEASUREMENTS: Hemodynamic measurements using pulmonary artery and systemic artery catheters, ventilator settings (FIO2, minute ventilation, peak inspiratory pressure, and positive end-expiratory pressure), arterial and mixed venous blood gases (pH, PCO2, PO2, and measured saturation), and clinical laboratory determinations (CBC, fibrinogen, plasma hemoglobin, complement C3 and C5) were obtained. Calculations of PaO2/FIO2 ratio and PaCO2-VE product were used to assess gas exchange efficacy. Microbiologic cultures were obtained from the device and wound following explantation. Survival to ICU discharge and hospital discharge were recorded. RESULTS: Implantation was successful in 20 of 22 patients. Gas exchange rates averaged 50.4 +/- 15.8 mL.min-1 for carbon dioxide and 71.1 +/- 20.2 mL.min-1 for oxygen. A reduction in FIO2 from 0.78 +/- 0.16 to 0.63 +/- 0.21 and in VE from 177 +/- 94 mL.kg-1.min-1 to 127 +/- 58 mL.kg-1.min-1 was possible within 4 h post-implantation. By 12 h, FIO2 was reduced to 0.57 +/- 0.18. Indices of gas exchange improved significantly after implantation, with PaO2/FIO2 ratio increasing from 79 +/- 20 to 112 +/- 47 and PaCO2-VE product decreasing from 7.6 +/- 4.2 to 4.9 +/- 2.5 within 4 h. A significant reduction in peak inspiratory pressure was achieved (45 +/- 10 to 38 +/- 9 cm H2O). Major complications were blood loss during implantation requiring transfusion in 11 patients, a retroperitoneal bleed in 1 patient, and femoral deep venous thrombosis in 4 patients, but there were no long-term sequelae or IVOX-related deaths. The ICU and hospital survival were 10/20 (50%) and 8/20 (40%), respectively. CONCLUSIONS: Intravenacaval membrane oxygen and carbon dioxide removal can provide partial respiratory support during severe respiratory failure and permit reductions in the level of mechanical ventilator support, with an acceptable safety profile.

Adult↗
PubMed1993

Prolonged intracorporeal support of gas exchange with an intravenacaval oxygenator.

Patients with severe respiratory failure undergoing conventional mechanical ventilation typically are exposed to levels of ventilator support that place the patient at risk of barotrauma or oxygen toxicity. In severe cases, gas exchange may be inadequate despite maximal ventilator support. We report two cases of advanced respiratory failure in which augmentation of gas exchange was provided for prolonged periods (18 and 13 days) with an intravenacaval hollow-fiber membrane oxygenator (IVOX). Following implantation, significant reductions in ventilator support were possible with improvement in arterial blood gas values. No significant complications were noted. IVOX can provide clinically useful augmentation of gas exchange in respiratory failure and can be used for prolonged periods.

Adult↗
PubMed1993

Immobilization of beta-glucosidase from Penicillium funiculosum on nylon powder.

beta-Glucosidase from Penicillium funiculosum was immobilized on nylon powder previously activated with triethyloxonium tetrafluoroborate, 1,2-diaminoethane and glutaraldehyde. The activation of the nylon powder and the immobilization processes were studied and optimized for the enzyme and the matrix. A high activity retention (67%) was obtained using the activation and immobilization conditions finally selected.

Borates↗
PubMed1990

Cardiovascular and metabolic response to red blood cell transfusion in critically ill volume-resuscitated nonsurgical patients.

We examined the cardiovascular and metabolic response to RBC transfusion in patients with circulatory shock after volume resuscitation. Data were analyzed from 36 transfusions in 32 patients who were undergoing continuous hemodynamic monitoring. Transfusions were administered for moderate to severe anemia, mean Hgb 8.3 g/dl. The diagnosis were sepsis (19/36), cardiogenic shock (14/36), connective tissue disease (2/36), and severe hypocalcemia (1/36). Benefit from transfusion was defined as an improvement in tissue oxygen utilization (increased oxygen consumption [VO2] or decreased lactate), a decrease in myocardial VO2 (MAP x HR), or a decrease in myocardial work (left ventricular work index). Mean transfusion volume was 577 ml over 4.5 h. Hgb and oxygen delivery (DO2) increased by 27% and 28%, respectively, while pulmonary artery wedge pressure and cardiac index were unchanged. No significant change was noted in VO2, or lactate, after augmentation of red cell mass. An increase occurred in myocardial work indices and MAP x HR. No changes were identified when subgroups were analyzed based on diagnosis, pretransfusion Hgb, lactate, or VO2 levels. We conclude that selective increase in DO2 by augmentation of RBC mass and oxygen-carrying capacity did not improve the shock state in these volume-resuscitated patients, regardless of the etiology of the shock.

Adolescent↗
PubMed1990

Accuracy of flexible fiberoptic endoscopy in identifying abnormal endotracheal tube positions.

This study was carried out to investigate the accuracy of a simple, nonmaneuverable, flexible fiberoptic catheter in identifying both normal and abnormal endotracheal tube (ETT) positions. In addition, the utility of flexible fiberoptic endoscopy (FFE) for ETT position determination in inexperienced hands was examined. One adult dog was sedated and instrumented in the esophagus and trachea with identical ETTs. Four possible ETT positions (trachea, carina, bronchus, esophagus) were randomly assigned. One investigator positioned the ETT into the assigned position by fluoroscopy. Four other blinded investigators were asked to determine the ETT position using the fiberoptic catheter. Each blinded investigator was given 15 seconds to complete the examination and record the ETT position. Randomization resulted in 25 ETT positions examined by each of the four blinded investigators for a total of 100 FFE determinations. FFE ETT determination was correct in 97% of the examinations. All esophageal intubations were correctly identified. Two tracheal locations were misdiagnosed as carina and bronchial, while one carinal location was incorrectly judged as tracheal. The sensitivity of FFE ETT localization was 91.7%, and the specificity was 98.6%. There was no difference in performance by investigator training level or endoscopy experience. We conclude that FFE is a rapid and accurate method for determining both normal and abnormal ETT locations. ETT position determination can be confidently performed by health professionals with minimal training.

Animals↗
PubMed1990

Tracheoesophageal fistula formation in intubated patients. Risk factors and treatment with high-frequency jet ventilation.

Two ventilator dependent patients developed tracheoesophageal fistulas. Their subsequent treatment using high frequency jet ventilation resulted in transient clinical improvement. Risk factors for the development of tracheoesophageal fistulas in intubated patients are discussed and preventive measures are outlined. High frequency jet ventilation may be useful in managing these patients by preventing death from respiratory failure and allows time for definitive therapy.

Adult↗
PubMed1990

Effect of red cell transfusion on oxygen consumption following fluid resuscitation in septic shock.

Previous studies have shown that fluid resuscitation in septic shock improves oxygen consumption. Red cell transfusion during resuscitation from septic shock has also been shown to enhance oxygen consumption in patients with elevated lactate levels. This study investigates the effect of increasing oxygen delivery (DO2) through an isolated increase in arterial oxygen content following adequate fluid resuscitation from septic shock in humans. Nineteen patients receiving red cell transfusion (591 +/- 55 SEM ml) were monitored for changes in hemodynamic and oxygen utilization variables before and after transfusion. Transfusion resulted in a significant increase in hemoglobin (8.3 +/- 0.3 to 10.7 +/- 0.3 g.dl-1) and DO2 (483 +/- 29 to 621 +/- 32 ml.min-1.m-2). No increase in cardiac output or pulmonary artery wedge pressure (PAWP) resulted from the transfusion. In spite of the increase in delivery, there was no increase in oxygen consumption (VO2) or decrease in lactate. Subset analysis revealed that a pretransfusion oxygen extraction ratio under 24% was associated with an increase in VO2, but the pretransfusion level of cardiac index, PAWP, lactate, or VO2 was not. An isolated increase in arterial oxygen content as a means of increasing DO2 does not improve VO2 in septic shock following adequate fluid resuscitation. Patients with a low oxygen extraction ratio (less than 24%) represent a subset of patients which did improve consumption with transfusion, and may represent a more severe microcirculatory disturbance not amenable to fluid loading.

Blood Transfusion↗
PubMedDate not supplied

Effects of gas leak around endotracheal tubes on indirect calorimetry measurement.

The use of uncuffed endotracheal tubes (ETT) in pediatric patients raises concern over the accuracy of indirect calorimetry measurement in the presence of a gas leak around an ETT. We examined the effects of ETT gas leak on respiratory gas measurements in a dog model. Mongrel dogs (n = 12) were sedated, paralyzed, intubated, and placed on mechanical ventilation. Leak was achieved by adjusting cuff volume. Oxygen consumption (VO2), CO2 production (VCO2), respiratory exchange ratio (RER), and resting energy expenditure (REE) were measured at each leak pressure (Pleak). Peak inspiratory pressure (PIP), Pleak, inspiratory and expiratory tidal volume (VTinsp, VTexp), VE, end tidal CO2 (ETCO2), and blood gases were recorded at each leak pressure. VO2, VCO, and REE decreased significantly with increasing gas leak. There was a linear relationship between VO2, VCO2, and REE with both TVratio (VTexp/VTinsp) and Pdiff (PIP-Pleak). Multiple regression equations based on TVratio and Pdiff were obtained which allowed correction of the measurement error in VO2, VCO2, and REE, with correlation coefficients (R2) of 0.71, 0.75, and 0.73, respectively. ETT gas leak affects measurements of VO2, VCO2, and REE, but not RER. Measurements made with TVratio greater than 0.80 required no correction. Measurements made with TVratio greater than 0.45 could be corrected to actual values in our model with regression equations based on TVratio and Pdiff. We conclude that indirect calorimetry measurements can be useful in the presence of tracheal gas leak around an ETT.

Animals↗
PubMedDate not supplied

[Indomethacin in the treatment of acute cholecystitis and biliary colic].

Prostaglandins GE2 produces on the gallbladder a rise in intraluminal pressure, an increase in in intraluminal secretion, improves gallbladder contraction and decreases its absorption capacity. In this study, patients who received indomethacin twice a day by rectum, showed a significant reduction in volume and area of gallbladder after 24 and 48 hours (P < 0.05). The gallbladder volume after 24 hours had SEM 9.13 cm3, 95% CI 55.28 + 73.49 (P < 0.05). Score pain reduction after 24 hours was also significant (P < 0.001). The patients who underwent the classical Baralcina treatment of one IV vial BID showed a reduction in diameter and area of gallbladder but this was not statistically significant (P < 0.10). Reduction of volume at 24 hours was SEM 5.34 cm3 95% CI - 64.72 + 76.60 P 0.10 NS; and at 48 hours SEM 3.5 cm3, 95% CI 59.52% + 66.52 P 0.40. Score pain reduction was only significant at 48 hours P 0.001. The number of patients without pain at 24 hours was significantly higher in the indomethacin group ESP 0.21; 95% CI 0.46 + 0.88 P 0.001. In conclusion indomethacin is a useful medication in the treatment of acute cholecystitis and biliary colic due to its anti-prostaglandin effect on the gallbladder.

Acute Disease↗