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Biomedical subjects

E Peña

Publications and source records attributed to E Peña.

At least 19 recordsLinked to original sources
PubMed2006

Influence of the tunnel angle in ACL reconstructions on the biomechanics of the knee joint.

BACKGROUND: A high tension in anterior cruciate ligament grafts affects both graft and knee functional performance. Clinical observations suggest that impingement of the graft against the posterior cruciate ligament might cause high graft tensions. Also, meniscal injury has been well documented in association with damage in the anterior cruciate ligament. METHODS: In this paper, we present the results obtained in a three-dimensional finite element model of the human knee, corresponding to different aspects of anterior cruciate ligament reconstruction with bone-patellar tendon-bone grafts. This model was used to investigate the effect of the angle in the coronal plane of femoral and tibial tunnels. Firstly, graft tension was computed in a knee moved from 0 degrees to 60 degrees of flexion and the results were compared with experimental ones obtained by other authors. Secondly, the resulting kinematics under an anterior load of 134 N was compared to that of the intact knee. FINDINGS: The obtained results showed that the closest anterior tibial translation to that of the intact knee was obtained with femoral and tibial tunnels with angles of 60 degrees. In this same case, a lower graft tension was also obtained. The results demonstrated noticeable increases in the meniscal stresses after anterior cruciate ligament reconstruction. INTERPRETATION: Our results showed that impingement only depends on the femoral tunnel angle. On the contrary, laxity principally depends on the tibial tunnel angle. The angle of the femoral tunnel affects the graft tension while the tibial tunnel affects laxity, meniscal stresses and strains.

Anterior Cruciate Ligament↗
PubMed2006

Biomechanical modeling of refractive corneal surgery.

The aim of refractive corneal surgery is to modify the curvature of the cornea to improve its dioptric properties. With that goal, the surgeon has to define the appropriate values of the surgical parameters in order to get the best clinical results, i.e., laser and geometric parameters such as depth and location of the incision, for each specific patient. A biomechanical study before surgery is therefore very convenient to assess quantitatively the effect of each parameter on the optical outcome. A mechanical model of the human cornea is here proposed and implemented under a finite element context to simulate the effects of some usual surgical procedures, such as photorefractive keratectomy (PRK), and limbal relaxing incisions (LRI). This model considers a nonlinear anisotropic hyperelastic behavior of the cornea that strongly depends on the physiological collagen fibril distribution. We evaluate the effect of the incision variables on the change of curvature of the cornea to correct myopia and astigmatism. The obtained results provided reasonable and useful information in the procedures analyzed. We can conclude from those results that this model reasonably approximates the corneal response to increasing pressure. We also show that tonometry measures of the IOP underpredicts its actual value after PRK or LASIK surgery.

Biomechanical Phenomena↗
PubMed2005

Sleep disturbances, socioeconomic status, and seizure control as main predictors of quality of life in epilepsy.

Improving quality of life is the most important goal for patients with epilepsy. To recognize the factors associated with quality of life in patients with epilepsy in Mexico, we performed a cross-sectional survey using the Quality of Life in Epilepsy 31 (QOLIE-31) inventory to assess the quality of life of 401 adult patients with epilepsy at the National Institute of Neurology and Neurosurgery of Mexico. Clinical and demographical data were collected. Multiple regression was used to determine which factors affected quality of life in our patients. The variables that most strongly predicted a lower QOLIE-31 total score after multiple regression were sleep disorders (P<0.001), socioeconomic status (P<0.001), female gender (P=0.002), and high seizure frequency (P=0.001). In our study, neither depression nor time of evolution of epilepsy had significant influence on QOLIE-31 scores.

Adult↗
PubMed2005

A three-dimensional finite element analysis of the combined behavior of ligaments and menisci in the healthy human knee joint.

We present here a three-dimensional FE model of the healthy human knee that included the main structures of the joint: bones, all the relevant ligaments and patellar tendon, menisci and articular cartilages. Bones were considered to be rigid, articular cartilage and menisci linearly elastic, isotropic and homogeneous and ligaments hyperelastic and transversely isotropic. Initial strains on the ligaments and patellar tendon were also considered. This model was validated using experimental and numerical results obtained by other authors. Our main goal was to analyze the combined role of menisci and ligaments in load transmission and stability of the human knee. The results obtained reproduce the complex, nonuniform stress and strain fields that occur in the biological soft tissues involved and the kinematics of the human knee joint under a physiological external load.

Finite Element Analysis↗
PubMed2005

A finite element simulation of the effect of graft stiffness and graft tensioning in ACL reconstruction.

BACKGROUND: The anterior cruciate is the most frequent knee ligament to be totally disrupted. Surgical reconstruction of the anterior cruciate ligament is a common practice to treat the disability or chronical instability of knees due to anterior cruciate ligament insufficiency. Some of the factors that influence the success or failure of the anterior cruciate ligament reconstruction are the integrity of secondary restraints, the preoperative laxity of the knee, the status of the articular and meniscal cartilages, the selection of the graft material, the surgical technique, the graft tension and the postoperative rehabilitation. METHODS: In this paper we present and discuss the results obtained with a three-dimensional finite element model of the human knee joint corresponding to different aspects of human anterior cruciate ligament reconstruction. In particular, this model was used to investigate the effect of graft stiffness and graft tensioning on the knee joint biomechanics. The initial graft tension was set to 0, 20, 40 or 60 N with the knee at 0 degrees , 30 degrees and 60 degrees of flexion. Three different stiffnesses corresponding to those of patellar tendon, gracilis and quadrupled semitendinosus grafts were analyzed. FINDINGS: The resulting kinematics in each of these cases under an anterior load of 134 N was compared to that of the intact knee. The obtained results showed that, after reconstruction, the closest anterior tibial translation to that of the intact knee is obtained with a bone-patellar tendon-bone graft with a pretension of 60 N. INTERPRETATION: However, this initial tension produces an important additional stress in the graft during the knee movement. This may cause problems in revascularization and remodelling during the postoperative healing process. A lower pretension of about 40 N should therefore be recommended in the present conditions.

Anterior Cruciate Ligament Injuries↗
PubMed2005

Finite element analysis of the effect of meniscal tears and meniscectomies on human knee biomechanics.

BACKGROUND: Many authors have suggested that the high levels of shear and tensile stresses that appear in the articular cartilage after meniscectomy are partly responsible for cartilage pathologies, such as osteoarthrosis. METHODS: In this paper, we investigate the effect of meniscal tears and meniscectomies on the human knee joint. Solid models of the tibia, femur, menisci and cartilage were generated from MRI images. A three-dimensional finite element model was developed that included the femur, tibia, cartilage layers, menisci and ligaments. The femur and tibia were considered to be rigid, the articular cartilage and menisci to be linearly elastic, isotropic and homogeneous and the ligaments were modelled as hyperelastic. Three different situations were compared: a healthy tibio-femoral joint, a tibio-femoral joint with tears in one meniscus and a tibio-femoral joint after meniscectomy. FINDINGS: The minimal principal stresses corresponding to a compressive load at 0 degrees flexion were obtained for the posterior zone of the medial meniscus and the corresponding region of the articular cartilage. Under an axial femoral compressive load, the maximal contact stress in the articular cartilage after meniscectomy was about twice that of a healthy joint. INTERPRETATION: This fact could partially explain the cartilage damage and degeneration that have been observed after meniscectomy.

Adult↗
PubMed2005

Basiliximab in lung transplantation: preliminary experience.

BACKGROUND: Basiliximab is a chimeric anti-interleukin-2 monoclonal antibody that has shown safety and efficacy in the prophylaxis of acute organ rejection in renal, liver, heart, and kidney-pancreas transplantation (Tx). The aim of this study was to present our initial experience with the use of Basiliximab in lung Tx. METHODS: Basiliximab (2 doses of 20 mg on day 0 and day 4) was administered to 16 patients treated with cyclosporine, azathioprine, and steroids between September 13, 2001 and August 26, 2003, including 12 men and 4 women patients with a mean age of 56.5 years (range, 19-69). The indication for use in transplantations were: reduced renal function (n = 14), post-Tx acute renal failure (n = 1) and steroid-resistant acute rejection (n = 1). Eight double-lung and eight single-lung Tx were performed for emphysema (n = 6), idiopathic pulmonary fibrosis (n = 7), silicosis (n = 2), and cystic fibrosis retransplantation (n = 1). RESULTS: The incidence of acute rejection was 16.6% (2 patients). Infections included cytomegalovirus (CMV) 33.3% (n = 4), bacterial 16.6% (n = 2), and fungal 8.3% (n = 1). Two patients died in the postoperative period and another at 3 months. There was no reaction to the medicine, and no malignancies or Bronchiolitis Obliterans Syndrome (BOS) during a follow-up period of more than 1 year in 10 patients. CONCLUSION: Basiliximab appeared to reduce the incidence of acute organ rejection and showed a good safety profile in terms of infections and adverse events.

Antibodies, Monoclonal↗
PubMed2004

Enzymolysis approach to compare cu availability from human milk and infant formulas.

The purpose of the present paper is to develop an easy and quick in vitro method to compare copper availability from breast milk and infant formulas. This study focuses on the differences caused by the use of pH 2.0 (adult gastric pH) or pH 5.0 (newborn gastric pH) in the first stage of the enzymolysis. pH affects Cu solubility, a possible estimator of the availability. Selection of a digestor, times of enzymolysis, centrifugation parameters, and Cu determination by ETAAS were discussed as well. Percentage of Cu solubility was larger from breast milk (gastric pH 2.0, 65.3 +/- 14.0 vs 40.0 +/- 13.9%; gastric pH 5.0, 61.2 +/- 16.5 vs 26.6 +/- 10.3%), but the soluble content was larger from infant formulas for both pHs (gastric pH 2.0, 245.3 +/- 82.1 vs 113.0 +/- 103.4 ng mL(-1); gastric pH 2.0, 169.3 +/- 76.9 vs 75.3 +/- 21.9 vs ng mL(-1)).

Biological Availability↗
PubMed2001

[Autoimmune hepatitis with prolonged IGM antibodies to HAV. Are serological markers reliable in ruling out a diagnosis of autoimmune hepatitis?].

We present the case of a 44-year-old woman who was referred to us for jaundice, choluria and acholia. Review of the patient's clinical history revealed that tests for hepatitis A virus (HAV) IgM antibody had been positive 4 and 2 years previously and continued to be so. The patient showed a score of 16 in the International Autoimmune Hepatitis Group's system when the HAV marker was not taken into account and a score of 13 when this marker was taken into account. The persistence of this viral marker for so many years in such patients is probably associated with polyclonal hypergammaglobulinemia. Consequently, we believe that the inclusion of this antibody as a negative datum in the diagnosis of autoimmune virus should be viewed with caution.

Adult↗
PubMed2001

Copper fractionation by SEC-HPLC and ETAAS: study of breast milk and infant formulae whey used in lactation of full-term newborn infants.

This method will allow the determination of bound copper to low relative molecular mass compounds in milk. The milk whey obtained by ultracentrifugation was submitted to fractionation by size exclusion chromatography (SEC) on a TSK-Gel2000 (Toso Haas) column with a mobile phase of 0.2 M NH4NO3 + NH3, pH 6.7. Fractions of effluent corresponding to the protein peaks were collected and the copper content was determined by ETAAS. The method was sensitive (LOD 0.4 microgram l-1 and LOQ 1.5 micrograms l-1 in the fraction; LOQ 7.5-22.5 micrograms l-1 referred to the milk sample and depended on fraction volume) and precise (RSD +/- 10%). Media sample recoveries from the column were 101.2%. Cu was predominantly present in fractions corresponding to relative molecular mass 76 and 15 kDa of breast milk while copper was mostly found in fractions corresponding to 14 and 38 kDa of cow's milk-based infant formulae; moreover, copper was eluted in the relative molecular mass region < 6 kDa.

Chromatography, High Pressure Liquid↗
PubMed2001

[Evolution and treatment response in microscopic colitis].

AIM: To study the clinical characteristics, treatment response and evolution in patients with microscopic colitis. MATERIAL AND METHODS: We performed a retrospective analysis of 24 patients (15 with collagenous colitis and 9 with lymphocytic colitis). Clinical and diagnostic features, treatment response and evolution according to the presence of maintenance therapy were evaluated. RESULTS: The mean age of the patients was 59.7 years and most were male. Nine patients took non-steroidal anti-inflammatory drugs (NSAID). No significant association was found with other drugs. Four patients presented associated rheumatological disease. Most patients presented insidious-onset diarrhea without pathological products, which was frequently associated with other symptoms (abdominal pain, bloating, weight loss, asthenia, tenesmus, and incontinence). Seven patients showed a slight increase in globular sedimentation rate. Fat in stools and radiological investigations (transit and opaque enema) were normal in patients who underwent these tests. Endoscopy revealed non-specific alterations in 42% of the patients while results were normal in the remaining patients. One patient showed clinical improvement on withdrawal of NSAIDs and 4 patients improved spontaneously. Clinical response was achieved in 7 of 13 patients treated with antimotility drugs, in 8 of 9 patients treated with salicylates, in 3 treated with oral corticoids, in 1 treated with cholestyramine and in 1 treated with topical budesonide. Nineteen patients required no maintenance therapy, 4 were administered salicylates and 1 was administered cholestyramine. After a mean follow-up of 42 months, evolution was chronic and intermittent in 14 patients and chronic and continuous in 1; 9 patients presented a single episode. No significant differences were found between patients administered maintenance therapy and those who were not or between collagenous colitis and lymphocytic colitis in the parameters analyzed. CONCLUSIONS: Microscopic colitis constitutes a group of diseases characterized by chronic diarrhea, few systemic effects and minimal radiological and/or endoscopic alterations. Evolution is characterized by recurrent episodes, with good response to treatment with cholestyramine, salicylates or corticoids when required.

Adult↗
PubMed2000

[Collagenous colitis: an entity with diverse therapeutic options].

Collagenous colitis is a disorder which has been diagnosed with increasing frequency in the last few years, probably due to the routine obtention of colon biopsy specimens in the study of patients with chronic diarrhoea. Good responses have been reported with a number of therapies, although only a scarce number of clinical trials have been performed, partly because of the small number of patients studied. Two cases of collagenous colitis with different therapeutic approaches are here reported. All medical therapy options for this interesting disorder are reviewed.

Administration, Topical↗
PubMed2000

[Idiopathic chronic pancreatitis (with diffuse stenosis of Wirsung's duct) in ulcerative colitis].

We describe a case of chronic idiopathic pancreatitis associated with ulcerative colitis. Pancreatitis is a rare extra-intestinal manifestations of inflammatory bowel disease. Chronic idiopathic pancreatitis associated with ulcerative colitis are usually painless, without calcification, with stricture of the main pancreatic duct and with severe exocrine pancreatic insufficiency.

Chronic Disease↗
PubMed1999

Linking extraction and purification of maize samples for fumonisin analysis.

Fumonisins are produced by several fungal species that are common contaminants of maize. The most abundant naturally occurring fumonisin, fumonisin B1 (FB1), has been shown to induce several animal disease syndromes. The development of analytical methods is therefore important. A new method is described that integrates extraction and purification of maize samples in one step. It efficiency is compared against well-known methods, and shows similar results for naturally contaminated maize. It is concluded that the proposed method can be applied to fumonisin B1 and fumonisin B2 (FB2) analysis in maize at least within the concentration range found.

Carboxylic Acids↗
PubMed1998

Neonatal exposure of male rats to estradiol benzoate causes rete testis dilation and backflow impairment of spermatogenesis.

Estrogens administered to perinatal rodents cause spermatogenesis impairment; this study was undertaken to determine the mechanisms by which estrogens exert this effect. Neonatal male Wistar rats received estradiol benzoate (either 0.5 mg/5g BW or 1 mg/5g BW) and were killed at days 10, 22, 33, 45, and 60. Controls received vehicle. In tubule cross-sections of transverse sections of the right testes, 1) tubular diameter (TD) and seminiferous epithelium height (SEH) were measured, 2) normal and impaired spermatogenesis were classified in terms of the most advanced germ cell type present, including tubules lined by Sertoli cells only. A significant dose-dependent rise in the tubule percentage lined by Sertoli cells only at day 60 reflected spermatogenesis impairment. This was evidenced by the presence of multinucleated germ cells in a thin epithelium and sloughed into an enlarged tubular lumen, which was reflected in a significant dose-dependent increase in TD/SEH values from day 22 onward. TD was significantly greater and SEH significantly lower in tubular segments located at the cranial than the caudal halves of rat testes treated with the high (days 22, 33, and 60) and the low dose (day 33). This indicated distension in cranial tubular segments, perhaps due to the fact that these segments were the closest to the dilated rete testis. Consequently, they showed the highest TD/SEH values and the most regressive features of spermatogenesis (tubules lined by Sertoli cells only). In contrast, caudal segments in rat testes treated with the low dose showing TD/SEH values similar to controls displayed a delayed maturation of spermatogenesis coinciding with the late appearance of mature Leydig cells.

Age Factors↗
PubMed1998

[Nutritional status of institutionalized elderly. Valencia, State of Carabobo, Venezuela].

To assess the nutritional status of 80 elderly living in a geriatric home, a cross-sectional study was designed. 40 men (76.1 +/- 8.2 years) and 40 women (83.1 +/- 6.9 years) were randomly selected. Anthropometric indicators (weight (W), height (H), triceps skinfold (TSF), muscle area (MA), fat area (FA), mid-arm circumference (MAC), arm muscle circumference (AMC) and body mass index (BMI)), biochemical parameters (hemoglobin, ferritin, cholesterol, albumin, zinc and vitamin A) and dietary intake (weighed method) were determined. MAC and AMC in men and PT and FA in women were below 10th percentile. 35.3% did not show signs of undernutrition, 39.7% was at nutritional risk (1 sign) and the other 25% was undernourished (2 or more signs). 8% showed anemia 52% had low values of ferritin, 13% were hypozincemic, 8% had vitamin A deficiency, 29% had hypoalbuminemia and 7.9% hipocholesterolemia. 50% and 48% of men and women had energy intake below 1.5 x BMR (n = 47). Vitamin A, C and zinc adecuacies were below 2/3 RDA. Evidence of the high nutritional risk of this elderly group is provided by alteration of anthropometric, biochemical and dietary indicators. Some other parameters must be assessed (reduced appetite, lack of foods) in order to detect more subtle changes of the nutritional status, and a nutritional intervention should be started immediately.

Aged↗