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Biomedical subjects

Eduardo Fernández

Publications and source records attributed to Eduardo Fernández.

11 recordsLinked to original sources
PubMed2006

A design framework to model retinas.

Neuro-engineering is providing biomedical engineers with technology to interface the nervous system, which is useful to create prosthetic devices to palliate sensorial or motor disabilities. Motivated by the success of cochlear implants for deaf patients, we are now facing the challenge of creating a prosthetic visual system for the blind. An artificial retina whose response to stimuli can be matched to biological ones is required. To make easier the task of modeling, tuning and testing these retinal models, we have created a software tool that allows flexible and parametric definition and testing of retina-like models. The program can be fed with a variety of video or image sources, and the results can be easily compared to biological recordings of retinal ganglionar activity in response to the same stimuli. This tool can be useful, not only for this prosthetic purpose, but for any other research involving bio-inspired image processing with a neuromorphic output.

Artificial Organs↗
PubMed2006

An atypical presentation of visual hallucinatory experiences following prolonged blindness.

We report a patient with long-standing blindness experiencing both simple and complex visual hallucinations secondary to a cortical arteriovenous malformation (AVM). The hallucinations were located in the right visual field corresponding to the contra-lateral site of cortical damage. This case contributes to our understanding of neurophysiological mechanisms underlying visual hallucinations and ongoing research investigating the phenomenology of hallucinations with respect to the cause and localization of neural damage.

Aged↗
PubMed2005

Oral ulcers in children under chemotherapy: clinical characteristics and their relation with Herpes Simplex Virus type 1 and Candida albicans.

OBJECTIVE: The objective of this study was to determine the clinical characteristics of oral ulcers in pediatric oncology patients undergoing chemotherapy and their relation with the presence of Herpes Simplex Virus (HSV) type 1 and Candida albicans. STUDY DESIGN: The sample consisted of 20 ulcerative lesions from 15 children treated with chemotherapy in the Pediatric Service of the Regional Hospital of Concepción, Chile. Two calibrated clinicians performed clinical diagnosis of the ulcers and registered general data from the patients (age, general diagnosis, absolute neutrophil count, and number of days after chemotherapy) and clinical characteristic of the ulcers: number, size, location, presence or absence of pain and inflammatory halo, edge characteristics, and exudate type. Additional to clinical diagnosis, culture for Candida albicans (C) and polymerase chain reaction (PCR) for Herpes Simplex Virus type 1 was performed. RESULTS: Ten ulcers occurred in patients with acute lymphoblastic leukemia, five in patients with acute myeloblastic leukemia and five in patients with other neoplastic diseases. Eight ulcers were HSV (+) / C (-), 6 HSV (-) / C (-), 4 HSV (+) / C (+) and 2 HSV (-) / C (+). Preferential location was the hard palate. Most lesions were multiple, painful, with inflammatory halo, irregular edges and fibrinous exudate. The average size was 6,5 millimeters, and the mean number of days after chemotherapy was 7.5 days. CONCLUSIONS: Oral ulcers in children with oncological diseases did not present a specific clinical pattern. They were strongly associated with HSV.

Adolescent↗
PubMed2005

Cinefluoroscopic assessment of mechanical disc prostheses: its value as a complementary method to echocardiography.

BACKGROUND AND AIM OF THE STUDY: Many types of mechanical prostheses are used for heart valve replacement, but it is difficult to distinguish between them using transthoracic echocardiography. Hence, cinefluoroscopy complements the echocardiographic evaluation of cardiac prostheses. The aims of the present study were to: (i) describe the contribution of cinefluoroscopy in identifying different prostheses; (ii) compare gradients obtained by Doppler echocardiography with the opening angle of the discs assessed by cinefluoroscopy; and (iii) assess the ability of cinefluoroscopy to distinguish normal from dysfunctional prostheses. METHODS: A total of 229 mechanical disc prostheses was prospectively evaluated with cinefluoroscopy. Eight prosthetic valves (six aortic, two mitral) were excluded due to the coexistence of severe left ventricular dysfunction. Thus, the final analysis comprised 221 prosthetic valves (146 aortic, 75 mitral). RESULTS: Based on the characteristics of the ring and the discs, cinefluoroscopy identified 87 single-leaflet and 134 bileaflet prostheses. Disc motion allowed distinction to be made between normal and dysfunctional prostheses (opening angle: 74 +/- 13 degrees versus 49 +/- 18 degrees). Fluoroscopy could not define disc profile or the ring in 6% of aortic valves and in 26% of mitral prostheses. The technique could be used to identify the TriTechnologies and HP-Biplus valves, but could not provide data on prosthetic function due to radiolucency of the discs. Among the 146 aortic prostheses, Doppler echocardiography helped to identify 109 normal valves and 37 dysfunctional valves. Among 75 mitral prostheses, 54 normal and 21 dysfunctional prosthetic valves were identified. When both methods were correlated, the sensitivity, specificity and positive and negative predictive values of fluoroscopy to distinguish normal from malfunctioning prostheses were 83%, 80%, 89%, and 71%, respectively. CONCLUSION: Each prosthesis type has radioscopic characteristics that allow its identification. Fluoroscopy permitted rapid and easy evaluation of mechanical prosthetic valve function, and in most cases allowed a distinction to be made between normal and dysfunctional prostheses. The presence of high gradients by Doppler echocardiography, with normal opening angles by fluoroscopy, and without pannus on transesophageal echocardiography, is indicative of patient-prosthesis mismatch. Fluoroscopy was superior to echocardiography in identifying disc motion, whilst Doppler study allowed the measurement of gradients and areas, and semiquantification of regurgitation. Thus, cinefluooscopy rapidly provides valuable information which is complementary to that obtained by echocardiography.

Aged↗
PubMed2004

Use of the humanized anti-epidermal growth factor receptor monoclonal antibody h-R3 in combination with radiotherapy in the treatment of locally advanced head and neck cancer patients.

PURPOSE: To evaluate safety and preliminary efficacy of the humanized anti-epidermal growth factor receptor monoclonal antibody h-R3 in combination with radiotherapy (RT) in unresectable head and neck cancer patients. Secondary end points were the measurement of h-R3 serum levels and the assessment of the potential mechanisms of antitumor effect on patient biopsies. Anti-idiotypic response to h-R3 was assessed. To predict pharmacologic effect, a mathematical model for antibodies recognizing antigens expressed in tumors and normal tissues was built. PATIENTS AND METHODS: Twenty-four patients with advanced carcinomas of the head and neck received six once-weekly infusions of h-R3 at four dose levels in combination with RT. Pretreatment tumor biopsies were obtained to evaluate epidermal growth factor receptor expression as an enrollment criterion. Second biopsies were taken to evaluate the proliferative activity and angiogenesis in comparison with the pretreatment samples. Patient serum samples were collected to measure h-R3 levels and anti-idiotypic response. RESULTS: The combination of h-R3 and RT was well tolerated. Antibody-related adverse events consisted in infusion reactions. No skin or allergic toxicity appeared. Overall survival significantly increased after the use of the higher antibody doses. Immunohistochemistry studies of tumor specimens before and after treatment revealed that antitumor response correlated with antiproliferative and antiangiogenic effect. One patient developed antibodies to h-R3. The mathematical model predicted that the maximum difference between the area under the curve in tumors and normal tissues is reached when the antibody has intermediate affinity. CONCLUSION: h-R3 is a well-tolerated drug that may enhance radiocurability of unresectable head and neck neoplasms.

Aged↗
PubMed2004

Conditioned spikes: a simple and fast method to represent rates and temporal patterns in multielectrode recordings.

Increasing evidence suggests that the brain utilizes distributed codes that can only be analyzed by simultaneously recording the activity of multiple neurons. This paper introduces a new methodology for studying neural ensemble recordings. The method uses a novel representation to provide complementary information about the stimuli which are contained in the temporal pattern of the spike sequence. By using this procedure, a high correlation of synchronized events with stimuli times is apparent. To quantify the results and to compare the performance of this method against the most traditional raster plot, we have used Fano factor and cross-correlation analysis. Our results suggest that several consecutive spikes from different neurons within an extended time window may encode behaviorally relevant information. We propose that this new representation, in addition to the other approaches currently used (standard raster plots, multivariate statistical methods, neuronal networks, information theory, etc.), can be a useful procedure to describe population spike dynamics.

Action Potentials↗
PubMed2004

[Sclerosing hemangioma presenting as a solitary lung nodule. Report of one case].

Lung sclerosing hemangioma is an uncommon tumor that presents as a solitary asymptomatic nodule and that affects middle age women. It derives from type II pneumocytes. We report a 52 years old female with a solitary lung nodule detected in a chest X ray requested for the diagnosis of an acute respiratory disease. The nodule was excised by video thoracoscopy and the frozen section biopsy was informed as a non small cell undifferentiated carcinoma. Therefore an inferior right lobectomy with lymph node resection was performed. The definitive biopsy was informed as a lung sclerosing hemangioma.

Biopsy↗
PubMed2003

Morphometrical analysis of dendritic arborization in axotomized retinal ganglion cells.

It has been reported that section of the optic nerve in mammals causes death in >90% of the retinal ganglion cells (RGCs). The cells which survive the section experience an irreparable loss of many of their dendritic segments and a rapid retraction of the dendritic tree. However, some growth cones and abnormal processes have been also reported. Our aim was to make a quantitative study of the morphological changes found in rabbit RGCs after optic nerve section. The morphometrical analysis of the RGCs which survived the axotomy showed an increase in the diameter of the soma and a significant increase in the area of the dendritic field; also, the length of the dendritic segments was significantly longer in axotomized RGCs than in control cells. Terminal dendritic segments (T) and preterminal segments (PT) were both measured in control and axotomized cells; the length ratio of T : PT segments was significantly greater in the axotomized cells than in the controls. We conclude that RGCs which survived the axotomy experienced a significant growth of their terminal dendritic branches.

Animals↗
PubMed2002

Allergic contact dermatitis from mercury antiseptics and derivatives: study protocol of tolerance to intramuscular injections of thimerosal.

BACKGROUND: Mercury derivatives are frequent contact allergens and their cross-reactivity is not constant. Thimerosal is an organic mercurial used as an antiseptic and as a preservative in most vaccines. OBJECTIVE: To evaluate cross-reactivity, exposure factors, and tolerance to vaccines containing thimerosal in patients sensitized to mercury derivatives. METHODS DESIGN: Observational study (cross-sectional); PATIENTS: 125 patients were recruited for the study, 72 women and girls and 53 boys and men, average age 18.7 years old, range 3 to 65, with positive patch tests to mercury derivatives and/or thimerosal; INTERVENTIONS: All patients were studied by means of enquiry, patch tests, intradermal tests, and intramuscular challenge with thimerosal. RESULTS: A sensitization to thimerosal was observed in 57 patients. Twenty-four of these 125 patients presented a positive intradermal reaction. Ammoniated mercury seems to be a good marker of mercury sensitization eliciting positive reaction in 78% of all patients and merbromin in 66%. In most cases, (100/125) cross-reactivity was found among mercury derivatives. The intramuscular injection of thimerosal induced a mild local reaction in only 5 patients (4% of the total, 9% of thimerosal positive reactions). Childhood vaccinations, merbromin used as an antiseptic, broken thermometers, and the use of drops were the main sources of exposure. CONCLUSIONS: The majority of the patients showed positive tests to both organic and inorganic mercury derivatives. Vaccination with thimerosal is relatively safe, even for individuals with delayed type hypersensitivity to this chemical, since more than 90% of allergic patients tolerated intramuscular challenge tests with thimerosal. A simplified protocol of patch tests to study mercury derivatives is proposed. It would be advisable to restrict the use of mercurial antiseptics and mercury thermometers.

Adolescent↗
PubMedDate not supplied

Use of a national reporting system for occupational injuries in Costa Rica.

Occupational injury surveillance in developing countries may be hindered by the lack of health data infrastructure as well the large numbers of informal-sector workers. The goal of this study was to elucidate the scope of occupational injury in the Monteverde district of Costa Rica using data collected through the national workers social security system. A list of occupational injuries occurring in the district reported to the National Insurance Institute (INS) central office between 1998 and 2002 was taken to the regional INS office, and the original injury reports for the cases were pulled. Specific data on the injuries were collected. There were 184 injuries reported during the five year period. Occupations with the highest number of injuries included production, building and grounds maintenance, and agricultural/forestry/fishing. Descriptive data showed that prevention efforts in this rural region should target food manufacturing, hotels, and construction.

Accidents, Occupational↗