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M J Alonso

Publications and source records attributed to M J Alonso.

133 records · Page 8Linked to original sources
PubMedDate not supplied

New strategies for the microencapsulation of tetanus vaccine.

The progress toward the development of a single dose tetanus vaccine has been limited by the poor stability of the protein antigen, tetanus toxoid (TT), during its encapsulation in, and release from, biodegradable polymer microspheres. To investigate alternative microencapsulation approaches that may improve the stability of TT under these conditions, a two-step microencapsulation method has been devised to form microcapsules which consist of: (a) forming microcores of TT in a hydrophilic support matrix by spray-congealing, followed by (b) coating the microcores with poly(lactide-co-glycolide) (PLGA) by an oil-in-oil solvent extraction method. Several protein stabilizers including gelatin (with or without poloxamer 188), dextran, sodium glutamate, and polyethylene glycol were examined as potential core-materials. Among them, gelatin was superior in its ability to impart stability to TT against heat and moisture-induced inactivation. Microcores of this latter stabilizer and TT were encapsulated in PLGA using the foregoing technique, which exposed the dry antigen to minimal water in order to prevent its irreversible inactivation during exposure to the organic solvent. The microencapsulation method resulted in minimal loss of antigenically active TT (approximately 10-20%). Microscopic analysis of the microcapsules following preparation showed the microcores to be fully encapsulated. However, microcapsules containing TT and gelatin released the active antigen nearly completely within one day. Fluorescence confocal microscopy revealed that the swelling of the hydrophilic core-material was responsible for the burst-release behaviour. Manipulation of the polymer coating could not slow down this 'explosion' of the microcapsules. TT-containing PLGA microcapsules have been prepared using a novel microencapsulation method, which retains an extremely high fraction of antigenically active TT. Hence, these mechanistic approaches may be useful in the development of effective single-dose vaccines.

Biocompatible Materials↗
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Aceclofenac-loaded poly-epsilon-caprolactone nanocapsules. Effect of coadjuvants on morphometrical properties and drug entrapment.

The physicochemical properties of aceclofenac nanocapsules, prepared by interfacial precipitation of poly-e-caprolactone at the oil/water interface, have been studied. A Central Composite Design was used to investigate the influence of polymerization adjuvants on these properties on the elaboration of aceclofenac-loaded poly-e-caprolactone nanocapsules. In this way, the effect of polymer, oil and drug concentrations in organic phase on the size and encapsulation efficiency has been analyzed. The optimized nanocapsule formulation leads to use an initial concentration of drug (aceclofenac) of 0.8 mg/ml and 0.6% of oil (Miglyol 812), being the polymer and surfactant concentrations previously fixed.

Algorithms↗
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Progressive hepatocytic fatty infiltration in rats with prehepatic portal hypertension.

BACKGROUND/AIMS: Homogenous evolution, with a narrow range of portal hypertension, degree of portosystemic shunt and hepatic atrophy has been described in the experimental model of prehepatic portal hypertension in the rat. However the great differences observed in the rats' liver weight could be attributed to a pathological alteration of the liver. Based on this, we performed an evolutive histological study of the liver. This study shows the existence of a progressive hepatocytic fatty infiltration. METHODOLOGY: Male Wistar rats with portal hypertension induced by triple stenosing ligation of the portal vein at 1 month (group II, n=4) and at 1 year (group IV, n=10) of postoperative evolution were used. The portal pressure, body, liver and splenic weights, types of collateral circulation and degree of mesenteric venous congestion were studied. The intracytoplasmatic lipid microvacuoles were quantified in hepatocytes with an image analyzer (software MIP/CID, Spain). The results were compared with those obtained in control rats with the same evolutive periods (Groups I and III). RESULTS: The hepatic fatty infiltration in Group II (TPVS 1 month) (30.12+/-53.92 micron2) is similar to that presented by Group III (Control 1 year) (16.52+/-45.20 micron2), while there is an increase (p<0.001) in Group IV (triple portal vein stenosis 1 year) (182.03+/-371.42 micron2) in relation to the other groups studied. The progressive hepatic fatty infiltration in triple portal vein stenosis rats is associated with a decrease of portal pressure and of the incidence of liver hepatic atrophy, portosystemic collateral circulation and mesenteric venous congestion. CONCLUSIONS: TPVS produces progressive hepatocytic fatty infiltration in the rat so that this prehepatic portal hypertension experimental model could also be considered as a hepatic steatosis model.

Animals↗
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Masson's vegetant intravascular hemangioendothelioma. Fine needle aspiration cytology, histology and immunohistochemistry of a case.

Masson's vegetant hemangioendothelioma is a benign intravascular tumor, sometimes confused with such malignant vascular tumors as angiosarcoma, whose clinical appearance is nonspecific and whose diagnosis can only be established through microscopic examination. The fine needle aspiration (FNA) cytologic findings together with the histologic and immunohistochemical findings of such a tumor in a 22-year-old man are presented. Cytologically, the material obtained by FNA consisted of two distinct populations of cells. One type of cell had large nuclei (sometimes displaced towards the periphery), finely granular chromatin, prominent nucleoli and abundant globular cytoplasm. The second type of cell had spindle-shaped or oval nuclei, granular chromatin and scanty eosinophilic cytoplasm. Although these findings may permit the cytologic recognition of this entity, the aspirate in this case was interpreted as showing a vascular mesenchymal tumor of probable malignancy. Histologic examination of the excised tumor, aided by immunoperoxidase studies for factor VIII antigen that revealed the endothelial nature of the proliferating cells, established the correct diagnosis.

Adult↗
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Usefulness of antral brushing samples stained with Diff-Quik in the cytologic diagnosis of Helicobacter pylori. A comparative methodologic study.

We studied the usefulness of antral cytologic specimens obtained by brushing and stained with Diff-Quik in the diagnosis of gastric colonization by Helicobacter pylori in 102 patients, comparing this method with other commonly employed techniques. We report on the sensitivity, specificity, predictive value for positive and negative cases of each of the techniques used, and diagnostic problems posed by each. In general, the Diff-Quik-stained samples proved to be the most useful. This technique is a simple, economical and practical method for the diagnosis of gastric colonization by H pylori.

Biopsy↗