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Biomedical subjects

Francisco Gonzalez

Publications and source records attributed to Francisco Gonzalez.

14 recordsLinked to original sources
PubMed2006

Temporal characteristics of visual receptive fields in primary visual cortex and medial superior temporal cortex areas.

We mapped the receptive fields of 49 cells from primary visual cortex and 19 cells from medial superior temporal cortex in two awake monkeys. The receptive field structures we obtained lasted a mean time of 32.7 ms in primary visual cortex and 38.4 ms in medial superior temporal cortex, showing no statistical difference. This result suggests that both areas have the same time requirements for processing visual information. In primary visual cortex, 100% of cells had conformed the receptive field structure at 65 ms pre-spike, whereas in medial superior temporal cortex it occurred at 150 ms. In both areas, cells with shorter response latencies had receptive field structures with longer durations. This may indicate that cells tend to synchronize their output to other areas.

Action Potentials↗
PubMed2006

Hemifield dependence of responses to colour in human fusiform gyrus.

To investigate the hemifield dependence of visually evoked responses to colour in the human fusiform gyrus we recorded evoked potentials from subdural electrodes in a patient suffering from occipital epilepsy. The responses in the fusiform gyrus show a strong hemifield dependence and discriminate the onset from the offset of the stimulus. Additionally, we found responses to squares made of random dots, whereas no responses were found to squares with a homogeneous bright surface. Our findings further support the idea that the fusiform gyrus is related to colour and pattern perception. However, the hemifield dependence we found may indicate that further processing is required in order to combine information from both visual hemifields.

Color Perception↗
PubMed2006

Lower pole pelvi-ureteric junction obstruction in duplicated collecting systems.

OBJECTIVE: To determine the incidence and efficacy of treatment for pelvi-ureteric junction obstruction (PUJO, the most common cause of hydronephrosis in the fetal kidney) in duplicated systems. PATIENTS AND METHODS: We retrospectively assessed patients with PUJO in a duplex collecting system, reviewing each case for age, sex, anatomy, presenting symptoms and type of management. RESULTS: From 1994 to 2004, 1413 patients were identified to have hydronephrosis; 243 of them had pyeloplasty for PUJO, and five (2%) involved the lower pole of a duplicated collecting system. In two of the patients the presentation was prenatal hydronephrosis (mean age at diagnosis 6 weeks) and the remainder presented with flank pain and pyelonephritis (mean age 5 years); all were boys. There was only one incomplete duplication (Y type). Four patients had a dismembered pyeloplasty and one a ureteric calycostomy. Vesico-ureteric reflux was present in three patients and two required common sheath reimplantation. On a radioisotope scan during the follow-up (mean 12 months) the five patients showed an improvement and no evidence of functional obstruction. CONCLUSION: The incidence of PUJO in duplicated systems was 2%; treatment should be individualized and requires a careful preoperative evaluation. This anomaly appears to be more common in boys and in completely duplicated systems.

Child↗
PubMed2005

Orbital emphysema after sneezing.

Orbital emphysema is a rare condition in the absence of trauma or sinus disease. We report two cases of orbital emphysema caused by sneezing. The patients presented with sudden unilateral eyelid swelling after sneezing. Otorhinolaryngologic and ophthalmic examinations were accompanied by computed tomography (CT). Patient examination disclosed crepitant eyelid swelling, ptosis, and mild unilateral exophthalmos. CT demonstrated areas of emphysema in the orbit. One patient had history of past trauma. The other patient had a history of nasal surgery and concurrent chronic sinusitis. Sneezing may cause orbital emphysema in patients with a history of old periorbital trauma or surgery.

Adult↗
PubMed2005

Retinal correspondence of monocular receptive fields in disparity-sensitive complex cells from area V1 in the awake monkey.

PURPOSE: To explore the neural mechanisms underlying disparity sensitivity in complex cells of the macaque visual cortex, the relationship between interocular receptive field (RF) positional shift and disparity sensitivity was studied in area V1. METHODS: Single-unit recordings were made from area V1 of awake Macaca mulatta. Monocular RFs were mapped by means of a reverse cross-correlation technique, and their centers were determined after performing a bidimensional Gaussian function fitting. Interocular RF shifts were calculated for both bright and dark stimuli. Similarly, Gabor adjustments were obtained from disparity profiles to bright and dark dynamic random-dot stereograms (RDSs). RESULTS: Twenty-five complex cells were studied. The response profiles to disparity were similar for bright and dark RDSs. Interocular RF positional shift correlated significantly with both the peaks of Gabor fittings of disparity-sensitivity profiles and the peaks of the Gaussian envelopes of these Gabor fittings. Correlation between interocular RF positional shift and the peaks of the Gaussian envelopes was stronger than correlation between interocular RF positional shift and peaks of Gabor fittings. CONCLUSIONS: Interocular shift of monocular RFs is more related to the center of the range of disparities to which the cell is sensitive, than to the preferred disparity of the cell.

Animals↗
PubMed2005

Publication output in telemedicine in Spain.

We searched the MEDLINE database for publications about telemedicine from 1966 to 2003. Only publications with a first institutional address in Spain and from journals listed in the JCR Science Edition 2002 were included in the study. A total of 118 publications were found. The first publication appeared in 1988 and publication output showed a sudden increase starting in 1995, reaching a maximum in 2002 with 21 publications. The number of authors per publication in non-multicentre studies ranged from 1 to 14 (median 6.5). Most authors (79%) contributed to only a single publication; 10% of authors participated in three or more publications. Most publications were full papers (88%). The most active Autonomous Community in the number of publications relative to inhabitants was Galicia (0.91 publications per 100,000 inhabitants). The Community that produced the highest absolute number of publications was Madrid (29% of the total). The mean impact factor of the journals in which the publications appeared was 0.961. Production of telemedicine publications in Spain has followed the same temporal course as has been observed worldwide. There is an unequal geographical and institutional distribution of publications. The highest production is concentrated in a few institutions and only a small number of authors show steady research activity.

Bibliometrics↗
PubMed2005

Measurements of the periocular facial area with Web-based software.

We developed a simple Web-based program to make measurements on displayed photographs between several ocular and periocular landmarks. The measurements were: (1) vertical distance between the margin of the upper and lower eyelids (palpebral aperture), (2) distance between the lower eyelid margin and the inferior corneal margin (palpebro-limbar distance); (3) interpupillary distance; (4) ocular proptosis. We measured the distances using the Web program and compared them with manual measurements on the subject's face. The measurements involved 102 eyes of 51 patients with a variety of ophthalmic conditions. There was good agreement between manual and computer measurements. For example, for manual measurements in 49 patients, we obtained interpupillary distances ranging from 45 to 69 mm (mean 61, SD 6), whereas for computer measurements we found values ranging from 42 to 49 mm (mean 59, SD 6). The mean of the differences between manual and computer measurements was -2.0 mm (SD 4.3) and the 95% limits of agreement were -6.5 to 10.5 mm. Thus, computer measurements tended to give a higher reading by between 0.8 and 3.2 mm (95% confidence interval for the difference). Web-based software may be used to perform measurements on two-dimensional pictures and the technique appears to be suitable for telemedical purposes.

Adolescent↗
PubMed2004

Evidence of basal temporo-occipital cortex involvement in stereoscopic vision in humans: a study with subdural electrode recordings.

Stereoscopic vision is based on small differences in both retinal images known as retinal disparities. We investigated the cortical responses to retinal disparities in a patient suffering from occipital epilepsy by recording evoked potentials to random dot stereograms (RDS) from subdural electrodes placed in the parieto-occipito-temporal junction, medial surface of the occipital lobe (pericalcarine cortex) and basal surface of the occipital and temporal lobes (fusiform gyrus). Clear responses to disparity present in RDS were found in the fusiform cortex. We observed that the fusiform responses discriminate the onset from the offset of the stimulus, correlation from uncorrelation, and they show a longer latency than responses found in the pericalcarine cortex. Our findings indicate that the fusiform area is involved in the processing of the stereoscopic information and shows responses that suggest a high level of stereoscopic processing.

Brain Mapping↗
PubMed2004

Binocular interaction and performance of visual tasks.

Binocular vision implies the fusion of the right and left retinal images to perceive a single image. For this, interocular interaction is required. We measured the reaction times to carry out a visual fixation task in order to determine whether binocular interaction influences performance. Several combinations of test and distraction stimuli were monocularly and binocularly presented to one monkey and three human subjects. The overall median reaction times were 340 ms for the animal and 308, 342 and 381 for human subjects 1, 2 and 3 respectively. Reaction time was shorter when the test stimulus was presented binocularly. Moreover, we observed that the presence of a distraction stimulus increased the reaction time and that a correlated distraction stimulus had a greater influence on this increase than an uncorrelated distraction stimulus. These findings indicate that with binocular vision a more rapid performance of a visual task occurs.

Adult↗
PubMed2003

Sensitivity to horizontal and vertical disparity and orientation preference in areas V1 and V2 of the monkey.

It has been suggested that cells are most sensitive to disparities along the axis orthogonal to their orientation preference. To test this assumption we studied the orientation preference of 73 cells sensitive to retinal disparity, 44 from V1 and 29 from V2. Orientation preference and disparity sensitivity were not related in tuned excitatory and tuned inhibitory cells. We found 18 near/far cells with orientation preference. Of these, 10 (56%) had a preferred orientation less than 30% away from the orthogonal to the disparity axis whereas the remaining eight cells (44%) exceeded this value. Our data suggests that the neural mechanisms for encoding retinal disparities present in dynamic random dot stereograms may not be related to the preferred orientation of the cell.

Animals↗
PubMed2002

Digital retinal images and teleophthalmology for detecting and grading diabetic retinopathy.

OBJECTIVE: Detecting and grading of diabetic retinopathy (DR) by means of digital retinal images sent via the Internet. RESEARCH DESIGN AND METHODS: Four nonstereoscopic digital retinal images (45 degrees field each) of 126 eye fundus images from 70 diabetic patients were obtained with a nonmydriatic camera at two peripheral units. The images were sent via the Internet using a web-based system to a reference center, where they were diagnosed and graded by one ophthalmologist. These results were compared with those obtained by two other ophthalmologists, one at each peripheral unit, after direct examination of the patients. A modified severity scale of Airlie House was used for grading DR in all cases. Agreement between observers was assessed using unweighted kappa for categorical data and the intraclass correlation coefficient (ICC) for continuous data. RESULTS: Presence of DR was detected in 69 eyes (55%). All eyes with DR (69 of 69, 100%) were correctly identified (kappa = 1) by inspecting the digital images. In 118 eyes (118 of 126, 94%), 57 with no DR and 61 with DR, there was an agreement between the gradation made after the direct examination and the gradation made after the inspection of the images (ICC = 0.92). In eight eyes with DR (8 of 126, 6%), there was disagreement in the grading made with both techniques. CONCLUSIONS: Inspection of digital retinal images sent via the Internet allowed diagnosis and grading of DR. The presence or absence of DR was correctly assessed by inspection of the images in all instances. We also found agreement, in most cases, between retinopathy gradation made from the images and the gradation made by direct examination of the eyes. These findings suggest that this technique is suitable for screening procedures.

Diabetic Retinopathy↗
PubMedDate not supplied

Kasabach-merritt phenomenon: a retrospective study of treatment with vincristine.

PURPOSE: Kasabach-Merritt phenomenon (KMP) is characterized by profound thrombocytopenia, microangiopathic hemolytic anemia, a consumptive coagulopathy, and an enlarging vascular lesion. The syndrome develops in infancy and is associated with a high morbidity and mortality rate. The purpose of this study was to assess the effectiveness of vincristine in the treatment of KMP. METHODS: We retrospectively reviewed the clinical and laboratory data of 15 patients with KMP treated with vincristine at 9 institutions across the United States, South America, and Europe. RESULTS: All 15 patients had profound thrombocytopenia and consumption of fibrinogen at presentation. Ten patients had biopsies of their lesions, and results included five (33.3%) kaposiform hemangioendotheliomas, three (20%) tufted angiomas, one lesion (6.7%) with features of both kaposiform hemangioendothelioma and tufted angioma, and one (6.7%) unclassified vascular tumor. All 15 patients had an increase in platelet count of at least 20,000 with an average response time of 4.0 weeks after initiation of vincristine therapy. Thirteen patients had an increase in fibrinogen level of 50 mg/dL with an average response time of 3.4 weeks. In 13 patients there was a significant decrease in the size of the vascular lesion. The average duration of treatment was 21.5 (+/-12.6) weeks. Four patients (26%) relapsed. All four were successfully treated with a second course of vincristine. Complications included one patient with abdominal pain, one patient with transient loss of deep tendon reflexes, and one patient with irritability. CONCLUSION: Vincristine presents a safe and sometimes effective treatment option in the management of KMP.

Antineoplastic Agents, Phytogenic↗