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M Preda

Publications and source records attributed to M Preda.

12 recordsLinked to original sources
PubMed2004

Historical trace metal fluxes in the Mexico City Metropolitan Zone as evidenced by a sedimentary record from the Espejo de los Lirios lake.

The accumulation of selected trace metals (Ag, Cd, Co, Cr, Cu, Hg, Ni, Pb, V and Zn) was studied in a sediment core collected at Espejo de los Lirios lake, a precipitation-dominated seepage lake in Northern Mexico City Metropolitan Zone (MCMZ). A (210)Pb-derived chronology, obtained from the same core, was used to reconstruct the historical metal fluxes at the site, allowing evaluation of the impact of environmental changes promoted by the development of the City during the last approximately 125 years. The highest levels of metal enrichment above natural concentration levels (NCL) in the sediments from Espejo de los Lirios lake were found for Ag and Pb (approximately 250%) as well as a slight enrichment for Cd (55%), Cr (84%), Co (20%), Cu (60%), Hg (47%), Ni (45%), V (59%) and Zn (66%). Fluxes of trace metals appeared to have noticeably increased from the last 45 years showing the maximum increments for Cd, Co, Cr, Ni, V and Zn during the 1980's (9 to 13 fold natural fluxes), for Ag and Cu (17 and 12 fold, respectively) during the 1990's and for Hg and Pb (2 and 13 fold) during the middle 1970's. Low levels of metal enrichment observed have evidenced that the most conspicuous consequences of the expansive growth of this area of the MCMZ, are mostly related to deforestation and erosion of the surrounding areas, rather than to trace metal pollution. Based on PCA, it can be assumed that atmospheric deposition, weathering of bedrock and soil within the watershed and authigenic production, are the most important processes that explain the trace metal distribution in the site.

Calcium Carbonate↗
PubMed2003

Polymorphic properties of micronized carbamazepine produced by RESS.

Carbamazepine microparticles were produced by the rapid expansion of supercritical carbon dioxide solutions (RESS) method. The characteristics of the resulting particles were studied by X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and image analysis. X-ray diffractograms and SEM photomicrographs revealed that the crystalline nature of the produced carbamazepine microparticles depended on operating pressure and temperature conditions. Different polymorphs were obtained under various operating conditions. Under certain temperature (below 40 degrees C) and pressure (below 240 bar) conditions, it was possible to form primarily the carbamazepine polymorph stipulated by US Pharmacopeia. A significant reduction was observed in the particle size and size distribution range of carbamazepine produced by RESS. The processed particles had a mean diameter smaller than 3 microm and a size distribution range between 0.5 and 2.5 microm compared to unprocessed starting material with a mean diameter of approximately 85 microm and a size distribution range between 15 and 336 microm. Thus, this study demonstrates that the polymorphic characteristics of carbamazepine microparticles produced by the RESS method can be controlled by varying operating pressure and temperature parameters.

Calorimetry, Differential Scanning↗
PubMed2002

[Iris-corneal dysgenesis].

This work presents a family, a mother and her 3 daughters, aged: 10 months, 4 years, 5 years with Rieger's anomaly. For children, this anomaly is associated with glaucoma and buphtalmy, this last element is the one that made the family ask for medical assistance and come to the hospital. The study of the disease was done on five generations in the same family, on the mother's line. This revealed that in the mother's family the grand grandmother and her two sisters were blind at an early age (30-40 years old). The presence of the anomaly in many generations proves the genetic transmission of the disease. We have to mention that in the last generation, the most serious appearance was registered at the patient with the earliest age (10 months).

Adult↗
PubMed2001

[Less frequent etiology in uveitis].

This material intends to present three clinical observations regarding the uveitis etiology, that is represented by the association of some etiological factors less known: Toxoplasma gondii, Listeria monocytogenes, Leptospira icterohaemorrhagiae. The uveitis described here have been severe in the fast evolution and with trends of reappearence. This work demonstrates that the strict etiological antibacteria and antiparasite therapy is not enough and only corticotherapy is able to fight against the accentuated inflammatory phenomena that go along with type of uveitis.

Adrenal Cortex Hormones↗
PubMed2000

Structure-properties relationship in cross-linked high-amylose starch for use in controlled drug release.

Cross-linked high-amylose starch (CLHAS), obtained by high-amylose starch cross-linking, was recently introduced as an excipient (Contramid) for monolithic dosage forms that are able to control drug release over 18-24 h. These control properties are related to tablet swelling and are strongly dependent on the degree of the cross-linking of CLHAS. The permeability of solutes through CLHAS hydrogels depends on the chemical structure of the polymer. The aim of this study was to obtain a better understanding of how modifications in CLHAS molecular structures at the level of long-range and short-range order during the cross-linking and processing conditions relate to the release properties of the CLHAS matrices. Structural parameters such as crystallinity contribute significantly to the physical and mechanical aspects of starch products. X-ray diffractometry, FTIR spectroscopy, dissolution tests in vitro, and mechanical hardness (of dry tablets) were found to be sensitive to the cross-linking degree (cld) variation. Best release properties and highest mechanical hardness were obtained from CLHAS matrices with low-to-moderate crystallinity, where the V- and the B-type structures coexist with amorphous regions. X-ray and FTIR profiles of dry CLHAS powders were found to be predictive for release properties of CLHAS tablets.

Amylose↗
PubMed1997

[The characteristics of crystalline lens metabolism].

The crystalline lens has a slow metabolism comparatively with others ocular structures: its energy is necessary to keep the transparency, ensure the nourishment for development and growth of the fibres. At the origin of the cataract are the old mitochondria that establish decreasing of available energy. This decreases the transport and necessary metabolism for the synthesis of proteins.

Carbohydrate Metabolism↗
PubMedDate not supplied

Oxprenolol-loaded bioadhesive microspheres: preparation and in vitro/in vivo characterization.

Biologically adhesive delivery systems offer important advantages over conventional drug-delivery systems. In this paper, microspheres intended as a sustained release carrier for oral or nasal administration have been prepared by associating a known bioadhesive polymer, poly(acrylic acid), in gelatin microspheres. A model drug oxprenolol hydrochloride was chosen. It was found that some of the formulation variables can influence the characteristics of the beads in a controlled manner. The internal structure of the microspheres studied by X-ray diffraction, thermal analysis and optical microscopy showed the absence of drug crystals in microspheres and a lowering in the glass transition temperature. The dynamic swelling of the beads obeyed the square root of time and a shift from the diffusional to the relaxational process dependent on the content of poly(acrylic acid) in gelatin microspheres was observed. As expected, drug release from gelatin/poly(acrylic acid) microspheres was influenced by the poly(acrylic acid) content in beads, by the particle size of microspheres and by the pH of the medium. The mechanism of release was analysed by applying the empirical exponential equation and by calculation of the approximate contribution of the diffusional and relaxational mechanisms to the anomalous release process by fitting the data to the coupled Fickian/Case II equation. In vitro and in vivo experiments in rats showed good adhesive characteristics of the gelatin/poly(acrylic acid) microspheres, which were greater if the poly(acrylic acid) content was greater. A significant retardation in gastric and intestinal emptying time of the beads was observed. This was also suggested by the bioavailability of the model drug after intragastric and intranasal administration of the microspheres. The pharmacokinetic parameters after microsphere administration were more appropriate to a slow release drug-delivery system. The work suggests the potential of this pharmaceutical delivery system as an alternative controlled-release dosage form, either for oral or nasal administration.

Acrylates↗
PubMedDate not supplied

[Plagiocephaly with telorbitism].

The case of a 5-year-old child, who is hospitalized for right eye deviation in divergence and facial asymmetry, is presented. The clinical exam together with the radiologic exploration, form the diagnosis of plagiocephaly with telorbitism. The plagiocephaly is a craniostenosis determined by early unilateral synostosis of the coronal link, and it is the cause of the malformation of interorbital space.

Child, Preschool↗