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Biomedical subjects

A Lorenzo

Publications and source records attributed to A Lorenzo.

At least 91 records · Page 5Linked to original sources
PubMed1982

Preliminary studies on transmural potential and intensity of the short-circuit current in intestine of Gobius maderensis.

The electrical difference (PD) and short-circuit current (Isc) across anterior intestine have been studied in vitro with solutions of different ionic composition in Gobius maderensis. 30 minutes after the beginning of the experiment a PD of about 2 mv negative serosa and an Isc of approximately 200 micro A/cm2 were recorded. Omission of sodium (Tris as substitute) from the luminal side or from both sides leads to an increment of 800% in PD more negative serosa together with an increase of 969% in Isc. In the absence of chloride (sulphate as substitute) the PD and Isc decreased and attained constant positive values. When the potassium was omitted from the luminal side or from both sides neither the P nor the Isc changed. These findings corroborate the assumption that active transport of chloride ions from mucosa to serosa is the major factor for transmural PD and account for the short-circuit current in the anterior intestine of Gobius maderensis.

Animals↗
PubMed1982

Comparative studies on the transmural potential difference and the intensity of the short-circuit current between the duodenum and the ileum of pigeon.

The transmural potential difference (PD), short circuit current intensity (Isc) and tissue resistance has been studied in duodenum and ileum of pigeon (Columbia livia var domestica) in media of different ionic compositions. When the tissue is incubated in a standard solution, the PD across the duodenum is approximately zero, while across the ileum is 7.2 mV (serosa positive with respect to mucosa). The PD and Isc measurements in duodenum in the absence of sodium on one hand and in the absence of chlorine on the other, reveal the existence of an active sodium absorption from mucosa to serosa, which draws chlorine along in the same direction. When sodium is substituted in the ileon (Tris as substitute), the PD and the Isc show a marked increase in serosa negativity. In the absence of the chloride ion sulphate as substitute) in ileon the PD and the Isc tend to zero, which indicate that the presence of the ion is necessary for the sodium transport.

Animals↗
PubMed1980

[Oxygen uptake and active transport of glucose by small intestine of lizard Lacerta galloti (author's transl)].

The lizard intestine capability for active transport of D-glucose has been studied in vitro at 30 degrees C. A release of glucose and fructose from intestinal tissue to the medium took place throughout the incubation period. An active transport of glucose against a concentration gradient from the mucosal to the serosal compartment was found, but in a Na+--free medium (Tris as a substitute) this process was strongly inhibited--. The oxygen uptake was 50% higher in the presence of glucose than in its absence.

Animals↗
PubMed1971

Epilepsy.

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Animals↗
PubMed1970

Epilepsy.

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Anticonvulsants↗
PubMedDate not supplied

Methodological variables in the assessment of beta amyloid neurotoxicity.

Cell culture systems for evaluating the biological effects of the beta-amyloid protein are potentially important tools in the study of the pathogenesis of Alzheimer's disease. In this report, methodological considerations in the assessment of beta-amyloid neurotoxicity are discussed. Chronic incubation of beta 1-40 in primary human cortical cultures results in progressive neuronal degeneration. The neurodegenerative process occurs in association with localized deposition of beta-amyloid on the neuronal soma ultimately resulting in the formation of compact beta-amyloid deposits. A beta 1-40 preparation from another laboratory was tested that did not form neuronal beta-amyloid deposits and was not neurotoxic. Thus, the conformational state of the beta 1-40 peptide leading to the formation of neuronal amyloid deposits is an important determinant of neurotoxicity. Variables in peptide preparation that influence this property may account for variation in neurotoxic potency.

Amyloid beta-Peptides↗
PubMedDate not supplied

ROC analysis of diagnostic performance utilizing serum antiproteases in cancer patients.

Assessment of the accuracy of diagnostic procedures is made independent of diagnostic criteria by means of a receiver-operating-characteristics (ROC) curve. We performed ROC analysis for the major serum antiproteases: alpha-1-antitrypsin (A1AT) and alpha-2-macroglobulin (A2M), in 99 cancer patients compared with 71 normal individuals. A1AT and A2M were significantly higher in cancer patients (p less than 0.0005). By comparing true positive and false positive rates for different serum levels, ROC analysis showed that serum A1AT quantification seems more useful in clinical practice than serum A2M.

Adult↗
PubMedDate not supplied

[Simultaneous analysis of myocardial perfusion and ventricular function. Normal values in the Mexican population].

UNLABELLED: Myocardial perfusion imaging is an useful procedure in the evaluation of patients with coronary artery disease, Gated SPECT technique evaluates simultaneously perfusion and ventricular function, left ventricular ejection fraction (LVEF), ventricular volumes and the transient ischemic dilatation of the left ventricle. OBJECTIVE: To evaluate the normal ventricle volumes and the ejection fraction of the LV obtained automatically with the Gated SPECT in Mexican population. METHODS: 100 patients were studied with low likelihood for CAD. All of them were studied with Tc-99m Sestamibi Gated SPECT. We obtained automatically the LVEF, and the end diastolic and systolic left ventricular volumes. RESULTS: Myocardial perfusion, regional motion and systolic thickening were normal in all patients. We obtained the mean values of EF and end diastolic and systolic volumes. These values were lower in female. CONCLUSION: Tc-99m Sestamibi myocardial perfusion SPECT is an useful procedure, with high accuracy for the simultaneous evaluation of myocardial perfusion and ventricular function.

Coronary Circulation↗
PubMedDate not supplied

[Myocardial perfusion evaluated with a 2-isotope technique. Experience with the first 1600 cases in Mexico].

SPECT has a high sensitivity for the diagnosis of coronary artery disease. Dual isotope protocol using rest thallium and stress MIBI was introduced in Mexico 4 years ago. This protocol reunite the advantages of both radiotracers for the study of myocardial perfusion. We present our experience of the first three years. One thousand six hundred patients were studied with suspected myocardial ischemia; 288 were excluded because of an absence of a proper follow up. In 895 of the 1312 patients a coronariography was performed. Images were evaluated by dividing the heart in 20 segments using a 5 points scale (0 = normal to 4 = absence of perfusion). It was considered a perfusion defect when a segment had a score greater or equal to 2 and the SPECT study was considered abnormal if two or more segments had a MIBI stress score equal or greater than 2. The global sensitivity for diagnosis of ischemia was 96.28%. Dual isotope method is appropriate for the diagnosis of ischemic heart disease. It has a high sensitivity and specificity for the recognition of global coronary disease and for specific coronary territories. This work constitutes the greatest series in Latin America that uses this diagnosis method.

Adult↗
PubMedDate not supplied

[Simultaneous assessment of myocardial perfusion and ventricular function using thallium-201 at rest/Tc-99m tetrofosmin at effort with single-photon emission computerized tomography, synchronized with electrocardiogram (synchronized SPECT). Initial experience in Latin America].

UNLABELLED: Gated SPECT is a useful technique to evaluate myocardial perfusion, wall motion abnormalities and wall thickening. There is not published experience in Latin-America using dual isotope rest Thallium-201/stress Tc-99m Tetrofosmin Gated SPECT. METHOD: We studied 27 patients with coronary artery disease. Coronary angiography was performed in all the patients. We used an injection at rest of 3 mCi of Thallium-201 followed by stress and the administration of 15 mCi of Tetrofosmin and Gated SPECT acquisition. Five days after, the patients were injected with 20 mCi of Sestamibi at stress, with a second Gated SPECT acquisition. Perfusion data were analyzed using 20 SPECT segment analysis. To study the wall motion, we divided the heart in 29 segments and every segment was scored using a 4 points scale (3 = normal, 2 = mild hipokinesia, 1 = severe hipokinesia, 0 = akinesia). RESULTS: The perfusion and wall motion segmental score agreement between stress Tc-99m tetrofosmin and stress Tc-99m sestamibi were 97% and 84% respectively. CONCLUSIONS: Rest Thailium-201/stress Tc-99m Tetrofosmin Dual isotope Gated SPECT technique is a good protocol to assess simultaneous myocardial perfusion and wall motion. There is a good agreement of the results with the use of rest Thallium-201/stress Tc-99m Sestamibi Dual isotope Gated SPECT study.

Adult↗
PubMedDate not supplied

[CT diagnosis of appendicitis. Report of a case and review of the literature].

Diagnosis of appendicitis has been historically supported in clinical findings. Imaging studies such as US and CT have been used mainly in cases where clinical diagnosis of appendicitis is uncertain. CT techniques have ranged between full abdominopelvic examinations after administration of oral and intravenous contrast media and unhenhanced scanning limited to the right bowel quadrant. We present the case report of an 18-year-old male patient with recurrent abdominal pain, with clinical suspicion of appendicitis; an abdominopelvic CT examination was performed that showed a suggestive image of appendicitis. This diagnosis was confirmed with the results of surgery and pathologic examination of the appendix.

Adolescent↗
PubMedDate not supplied

[Changes in carbohydrate metabolism in the HIV/AIDS patient].

Over the last few years, there has been a considerable reduction in the mortality and morbidity associated with HIV patients, due to the use of protease inhibitors which have led to a true revolution in the treatment of this infection. A new problem has arisen with the increased life expectancy: the onset of a plurimetabolic syndrome characterized by hypertriglyceridaemia, hypercholesterolaemia and hyperglycaemia; in addition to anomalies in composition and distribution of body fat (central obesity and loss of peripheral fat) due to the associated lipodystrophy. As a result of the metabolic alterations, there is an increase in the risk of cardiovascular disease. Hyperglycaemia is the result of insulin resistance and is detected in between 13.6% and 46% of patients, possibly leading to type 2 diabetes (diagnosed in between 2.4% and 7% of the patients). These alterations have been documented as potentially related with the use of protease inhibitors and other drugs used in the handling of HIV patients. The appropriate treatment of altered metabolism of carbohydrate requires: 1) a customized dietary approach depending on individual BMI and lipid alterations; 2) a physical exercise programme; 3) the use of insulin sensitization drugs: metformin and thiazolidinediones and, where the therapeutic goals are not achieved or there is a contraindication for oral hypoglycaemic drugs; 4) insulin therapy with regimens similar to other diabetic patients.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Ultrastructural observations on blood vessels surrounding normal and regenerating spinal cord in newt.

The ultrastructural analysis of capillaries surrounding normal and regenerating caudal spinal cords of two species of newt (Triturus vulgaris and T. cristatus) is reported. Around normal spinal cords, capillaries were generally continuous. Surrounding the regenerating spinal cords the various capillaries of the regenerating blastema appeared discontinuous with small or broad gaps along the capillary wall. This was seen even after two months of tail regeneration when the spinal cord was similar to the normal and many axons were myelinating. These morphological findings suggest that during tail regeneration in newts the blood-brain barrier is not very effective. Also extravasating mature and immature blood cells were observed inside regenerating capillaries. Therefore growing capillaries can exchange metabolites and, possibly, growth factors with the nervous tissue and the other regenerating tissues.

Animals↗
PubMedDate not supplied

Plasmatic fibronectin in malignancies.

Plasmatic fibronectin has been studied in tumor patients on the basis of the role that unspecific opsonin may play in tumor growth and spreading. Alterations in fibronectin levels might be used as a biological marker and our purpose has been to evaluate the significance of this test in the biological diagnosis of cancer. When comparing the levels found in the control group (22.86 +/- 1.40 mg/dl) and in tumor patients (23.80 +/- 1.90 mg/dl), we observed no difference in the overall group. However, in relation to the localization of tumors, a significant increase was found in breast cancer (31.83 +/- 3.83 mg/dl) and a significant decrease in squamous cell carcinoma of the head and neck (9.56 +/- 1.68 mg/dl). These results suggest that plasmatic fibronectin could be useful as a biomarker in some types of tumors. Our conclusion was confirmed by analysis of ROC curves related to every one of the studied tumors.

Adolescent↗