Biomedical subjects

A Arriaga

Publications and source records attributed to A Arriaga.

11 recordsLinked to original sources

PubMed2004

Evaluation of L1 and L2 minimum norm performances on EEG localizations.

OBJECTIVE: In this work we study the performance of minimum norm methods to estimate the localization of brain electrical activity. These methods are based on the simplest forms of L(1) and L(2) norm estimates and are applied to simulated EEG data. The influence of several factors like the number of electrodes, grid density, head model, the number and depth of the sources and noise levels was taken into account. The main objective of the study is to give information about the dependence, on these factors, of the localization sources, to allow for proper interpretation of the data obtained in real EEG records. METHODS: For the tests we used simulated dipoles and compared the localizations predicted by the L(1) and L(2) norms with the location of these point-like sources. We varied each parameter separately and evaluated the results. RESULTS: From this work we conclude that, the grid should be constructed with approximately 650 points, so that the information about the orientation of the sources is preserved, especially for L(2) norm estimates; in favorable noise conditions, both L(1) and L(2) norm approaches are able to distinguish between more than one point-like sources. CONCLUSIONS: The critical dependence of the results on the noise level and source depth indicates that regularized and weighted solutions should be used. Finally, all these results are valid both for spherical and for realistic head models.

Artifacts↗

PubMed2000

A structural and immunocytochemical study of palatine and labial salivary glands from chronic alcoholics.

In the present study we investigated tissue changes in palatine (PG) and labial (LG) minor salivary glands from individuals who had died of alcoholic hepatic cirrhosis, to characterize histopathological parameters of alcoholic sialosis, that may be used for differential diagnosis. Samples obtained from autopsies were processed using cytochemical techniques for mucosubstances and immunocytochemical labelling for cytokeratines, PS 100 and T-cells. Both PG and LG showed dilated excretory ducts with atrophic epithelium, which contained PAS+ metachromatic material and detached cells. Intra and interlobular ductal hyperplasia was present in some areas, mainly in PG. CK expression was heterogeneous in ductal cells, and negative in acinar cells. Most of the acinar cell nuclei were normal, but some of them were atypical in shape and distribution. Myoepithelial cells, serous demilunes and the basal region of the cells of the striated ducts expressed PS 100. In PG, 85% of the mononuclear infiltrates expressed T-cell markers, whereas in LG only 40% of these cells were T-cells. These findings, in addition to other histopathological parameters seen in previous studies, may be used as indicators for differential diagnosis with other gland pathologies.

Aged↗

PubMed1999

Histological study of parotid, submaxillary and von Ebner salivary glands in chronic alcoholics.

Samples from parotid, submaxillary, and von Ebner salivary glands of six chronic alcoholic individuals who had died of alcoholic hepatic cirrhosis were analyzed by topographic and histochemical routine stains and marked for cytokeratins; two normal adult individuals were used as control. Modifications in the acinar cells were found, but the most evident changes were observed in the ductal system: enlargement of major ducts, heterogeneous expression of cytokeratins and athrophy in epithelial cells, desquamated cells and stasis of content, and ductal hyperplasia in von Ebner glands. The lymphoplasmocytic infiltration does not represent the typical lymphocytic focus on Sjögren's syndrome or other connective tissue pathologies. Our findings indicate that functional and structural variations are produced both in serous acini and ducts parotid, submaxilar and von Ebner glands affected by alcoholic sialosis.

Adult↗

PubMed1996