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S Ramírez

Publications and source records attributed to S Ramírez.

At least 19 recordsLinked to original sources
PubMed2005

Ecotoxicological evaluation of diesel-contaminated soil before and after a bioremediation process.

Evaluation of contaminated sites is usually performed by chemical analysis of pollutants in soil. This is not enough either to evaluate the environmental risk of contaminated soil nor to evaluate the efficiency of soil cleanup techniques. Information on the bioavailability of complex mixtures of xenobiotics and degradation products cannot be totally provided by chemical analytical data, but results from bioassays can integrate the effects of pollutants in complex mixtures. In the preservation of human health and environment quality, it is important to assess the ecotoxicological effects of contaminated soils to obtain a better evaluation of the healthiness of this system. The monitoring of a diesel-contaminated soil and the evaluation of a bioremediation technique conducted on a microcosm scale were performed by a battery of ecotoxicological tests including phytotoxicity, Daphnia magna, and nematode assays. In this study we biostimulated the native microflora of soil contaminated with diesel by adding nutrients and crop residue (corn straw) as a bulking agent and as a source of microorganisms and nutrients; in addition, moisture was adjusted to enhance diesel removal. The bioremediation process efficiency was evaluated directly by an innovative, simple phytotoxicity test system and the diesel extracts by Daphnia magna and nematode assays. Contaminated soil samples were revealed to have toxic effects on seed germination, seedling growth, and Daphnia survival. After biostimulation, the diesel concentration was reduced by 50.6%, and the soil samples showed a significant reduction in phytotoxicity (9%-15%) and Daphnia assays (3-fold), confirming the effectiveness of the bioremediation process. Results from our microcosm study suggest that in addition to the evaluation of the bioremediation processes efficiency, toxicity testing is different with organisms representative of diverse phylogenic levels. The integration of analytical, toxicological and bioremediation data is necessary to properly assess the ecological risk of bioremediation processes.

Animals↗
PubMed2000

Two nitrate/nitrite transporters are encoded within the mobilizable plasmid for nitrate respiration of Thermus thermophilus HB8.

Thermus thermophilus HB8 can grow anaerobically by using a membrane-bound nitrate reductase to catalyze the reduction of nitrate as a final electron acceptor in respiration. In contrast to other denitrifiers, the nitrite produced does not continue the reduction pathway but accumulates in the growth medium after its active extrusion from the cell. We describe the presence of two genes, narK1 and narK2, downstream of the nitrate reductase-encoding gene cluster (nar) that code for two homologues to the major facilitator superfamily of transporters. The sequences of NarK1 and NarK2 are 30% identical to each other, but whereas NarK1 clusters in an average-distance tree with putative nitrate transporters, NarK2 does so with putative nitrite exporters. To analyze whether this differential clustering was actually related to functional differences, we isolated derivatives with mutations of one or both genes. Analysis revealed that single mutations had minor effects on growth by nitrate respiration, whereas a double narK1 narK2 mutation abolished this capability. Further analysis allowed us to confirm that the double mutant is completely unable to excrete nitrite, while single mutants have a limitation in the excretion rates compared with the wild type. These data allow us to propose that both proteins are implicated in the transport of nitrate and nitrite, probably acting as nitrate/nitrite antiporters. The possible differential roles of these proteins in vivo are discussed.

Anion Transport Proteins↗
PubMed1998

Prevalence of phenotypic activated protein C resistance (APCR) in venous thromboembolic patients.

Until the discovery of activated protein C resistance (APCR), less than 10% of patients with venous thromboembolism (VT) showed defects in proteins involved in the inhibition of coagulation. APCR is caused by a single point mutation in the factor V gene, and it is accepted that APCR is associated with an increased risk for VT. In this work, we studied the prevalence of APCR in venous thromboembolic patients and found it to be 10.5% compared with 4.5% in controls (p = 0.105).

Aged↗
PubMed1989

[Enterotoxigenic Staphylococcus aureus and thermonuclease: risk indicators of staphylococcal poisoning with milk products].

We examined 159 samples of milk and milk products for staphylococcal count and presence of thermonuclease. Highest count for S aureus was found in cheese, followed by raw milk. Enterotoxins, mostly A and D, were found in 32% of 34 S aureus strains isolated from cheese and milk. Thermonuclease was detected in dried milk and cheese. Identification of this enzyme is a good method to evaluate risk of food poisoning from S aureus contamination.

Animals↗
PubMedDate not supplied

[Coronary revascularization without extracorporeal circulation. An alternative therapy (preliminary report)].

Direct myocardial revascularization techniques has earned great acceptance in the treatment of ischemic coronary syndromes in the past two decades. Almost since its beginnings the procedure was done with the aid of extracorporeal circulation, since the technical accessibility with cardiac standstill further helped to evolve the procedure. As years went by, complications due to the use of the pump became evident, such as microembolism, bleeding disorders, and others. Besides this, there is a special group of patients, those with high surgical risk, with preexisting pulmonary, hepatic or cerebral disease, who benefit a great deal when bypass grafting procedure is done without the pump. In this article we delineate the indications, contraindications, and the procedure itself based in our personal experience, reporting our first five patients with this technique.

Aged↗
PubMedDate not supplied

[Permanent rhythm and conduction disorders in patients surgically treated for atrial septal defect].

Atrial septal defect (ASD) represents a congenital heart disease with good prognosis, however, atrial arrhythmias are well-documented complications. A retrospective study was performed to assess the prevalence, types and risk factors of arrhythmias in patients with ASD after surgical correction. 920 patients were analyzed retrospectively; cases with complex congenital heart disease or another systemic alteration conditioning atrial rhythm disturbances were excluded. 460 patients with ASD corrected by surgery were followed at least for six months after the procedure. 29.3% of patients were male and 70.7% female. Direct closure was performed in 63%, pericardial patch was installed in 27%. 29 patients (6.3%) had conduction and rhythm disturbances before surgery, the most common arrhythmias were atrial flutter (34.5%), first degree A-V block (31%) and low right atrial rhythm (27.6%). Six months after atrial defect closure, 65 patients (14.13%) had arrhythmias, 44.6% atrial flutter, 20% ectopic atrial rhythm, 10.8% sick sinus syndrome. The risk of atrial arrhythmias was related to age at surgical repair, pulmonary hypertension and atrial arrhythmias before surgery.

Adult↗
PubMedDate not supplied

[Double inlet left ventricle. Morphopathology and surgical anatomy].

Because of the possibility of surgical treatment of double inlet left ventricle, its basic morphologic features of surgical and imaging importance are analyzed. Seventeen hearts were studied with the segmental sequential system. The situs was solitus in thirteen; dextroisomerism in three and levoisomerism in one. The atrioventricular valves were separated in nine; there was a common atrioventricular valve in eight; straddling of the atrioventricular valve in seven and stenosis in two. The rudimentary right ventricle was to the right side in twelve hearts and to the left side in five. The discordant ventriculoarterial connection was the most frequent (seven), followed by the concordant one (five) and double outlet right ventricle (five). There was pulmonary stenosis in five. The ventricular septum did not reach the crux cordis. The ventricular septal defect was bigger in straddling atrioventricular valves than in valves completely open into the left ventricle, being restrictive in ventriculoarterial concordance. Surgical treatment varies as the complexity of this cardiopathy does, from cardiac septation to palliation procedures. The morphologic knowledge of this cardiac malformation is basic to interpret correctly the diagnostic imaging.

Cardiac Surgical Procedures↗
PubMedDate not supplied

[Trans-surgical ablation of atrial flutter in patients treated with closure of atrial septal defect. Pilot project].

Atrial flutter is one of the most common arrhythmias in patients with atrial septal defect, after surgery 14% of patients can develop it and may be associated with high morbidity. In this study we performed prophylactic and therapeutic ablation of atrial flutter during atrial septal closure surgery drawing 4 lines; line 1, isthmus cavo-tricuspid, the area between the inferior vena cava and the tricuspid ring; line 2, the area between coronary sinus ostium and inferior vena cava; line 3, the area between tricuspid valve annulus and coronary sinus ostium; and line 4, the area between lateral atriotomy and atrial septal defect. Twenty-one patients were included, 6 (28.5%) patients had atrial flutter before surgery and 15 (71.4%) were in sinus rhythm. There were no new cases of atrial flutter, but at six months follow up 2 (33.3%) patients recidivated with atrial flutter. One patient developed high degree atrio-ventricular block and a pacemaker had to be implanted. Older age at the time of surgery and high systolic pulmonary pressure were significantly higher in those patients with atrial flutter before surgery and in patients with arrhythmias recurrence. Ablation of atrial flutter during atrial septal closure surgery can be a good option for the treatment and prevention of atrial arrhythmias, but more studies are still needed.

Adolescent↗
PubMedDate not supplied

[The usefulness of electrophysiology in a patient undergoing cardiomyoplasty].

The cardiomyoplasty is a new surgical procedure that uses a skeletal muscle electrostimulated in order to reinforce or even substitute partially the cardiac muscle. We present the electrophysiology aspects in a patient with dilated cardiomyopathy that underwent cardiomyoplasty. First the latissimus dorsi muscle was prepared with a neurostimulant ITREL II. During the surgical procedure a dual-chamber pacemaker mode DDD brand CPI was placed. After three months, ablation radiofrequency of the AV node was performed in order to control the atrial fibrillation that caused heart failure. By means of the AV block we obtained synchrony between the ventricular stimulation and the latissimus dorsi muscle, and by this the patient improved. Using the modern pacemakers and radiofrequency we can control the bradyarrhythmias as well as the tachyarrhythmias frequent in patients with dilated cardiomyopathy, increasing the success rate of cardiomyoplasty.

Adult↗
PubMedDate not supplied

[Surgical resection of a focus of ventricular tachycardia guided by endocardial and epicardial mapping].

We describe a case of a 46 years old female with chagasic heart disease. In one year she presented six episodes of sustained ventricular tachycardia, heart rate 230 beats per minute, morphology of RBBB AQRS -60 degrees, with hemodynamic deterioration that needed electrical cardioversion. She was treated with several antiarrhythmic drugs but not good response was obtained. Programmed electrical stimulation was done and it show three different types of ventricular tachycardia, trough pace-mapping the site of the clinical tachycardia was located in the portion inferior and inferior-posterior of the left ventricle that was confirmed by entrainment. Epicardial mapping was performed in 38 ventricular sites following the modified Harken sketch and the location of the site of outlet was confirmed in the posterior base of the left ventricle, at this point the surgical resection was done with no complication. The results were satisfactory. Eight days later programmed electrical stimulation was done and the ventricular tachycardia could not be induced. Six months afterwards the patient is asymptomatic without medical treatment.

Cardiac Pacing, Artificial↗
PubMedDate not supplied

[Atrioventricular and ventriculoatrial conduction in patients operated on for the Wolff-Parkinson-White syndrome].

Over the last decade the surgical treatment of the Wolff-Parkinson-White syndrome has been well accepted. It is important to make an early diagnosis for surgical success. For this purpose we utilized programmed electrical stimulation to assess the functional characteristics of atrioventricular and ventriculoatrial conduction in our post-operative patients. In 55% of the cases we found accelerated nodal conduction. Programmed electrical stimulation correctly identified 90% of successfully treated patients. We did not found any false positive curve, therefore, this method has a high specificity. We concluded that in post-operative patients with the Wolff-Parkinson-White syndrome: 1- There is a high incidence of accelerated nodal conduction and 2- programmed electrical stimulation can correctly identify most of the patients who were successfully treated.

Adolescent↗
PubMedDate not supplied

[Surgical treatment of supraventricular tachycardias (Wolff Parkinson White and Occult Kent). Experience at the "Ignacio Chávez" National Institute of cardiology].

We report our initial experience in the surgical section of the accessory pathway in thirteen patients: eight patients with Wolff Parkinson White syndrome and five with accessory pathway functioning only in direction ventricle to atrium (Kent concealed), with recurrent episodes of paroxysmal supraventricular tachycardia with no response to medical treatment. Three of these patients had episodes of auricular fibrillation with interval RR lower than 250 msec and one patient presented syncope. A total of fifteen accessory pathways were sectioned: 7 left lateral, 5 left posterior, one left posterolateral, one right lateral, and another one right anteroseptal. In the same procedure two patients had correction of another heart malformation: one with patent ductus arteriosus and another with and another with atrial septal defect. All patients had successful outcome, one of them needed a second surgery for persistent accessory pathway. We had two post-operatory complications: one mediastinitis and one patient with ectopic auricular tachycardia.

Adolescent↗