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Biomedical subjects

M J Alonso

Publications and source records attributed to M J Alonso.

At least 91 records · Page 5Linked to original sources
PubMed1996

Distribution of glyoxylate dehydrogenase activity in cortical and subcortical regions of the rat brain. A light microscopic histoenzymological study.

The distribution of the glyoxylate dehydrogenase (GLYO-DH) (Glyoxylate oxidoreductase) activity has been investigated in rat brain using the corresponding histochemical method. The results have demonstrated a positive histochemical reaction in neurons of several cortical and subcortical areas. These neurons are located in the same regions in which operate monoaminergic neurotransmitters. These facts suggest a possible interaction between glyoxylic acid and monoaminergic neurotransmission.

Aldehyde Oxidoreductases↗
PubMed1996

Neuronal and non-neuronal localization of acid sulfated glycosaminoglycans (sGAG) and chondroitin proteoglycans in the rat medulla oblongata.

Acid sulfated glycosaminoglycans (sGAG) and chondroitin proteoglycans have been biochemically and immunohistochemically demonstrated in certain cortical areas of the CNS. Such molecules display an important role in cerebral function, modulating cell adhesion, migration and signal neuromediation. In the present study we have evidenced the presence of sGAG using the colloidal iron method and C0S, C4S- and C6S-proteoglycans by the immunohistochemical pre-embedding PAP method. Our results have demonstrated the presence of such molecules in several structures of nervous (axon terminals, neuronal bodies, dendrites) and non-nervous nature (glial processes, capillaries). This fact led us to suggest that the chondroitin localizations advocate for their different functions. In their various localization exist distinct proteoglycans constituted by chondroitins with diverse concentrations and other attached radicals.

Animals↗
PubMed1995

Microdialysis sampling to determine the pharmacokinetics of unbound SDZ ICM 567 in blood and brain in awake, freely-moving rats.

The free concentrations of the serotoninergic 5-HT3 antagonist SDZ ICM 567 in blood and in the central nervous system were examined in awake, freely-moving rats using blood and brain microdialysis coupled to liquid chromatography. Microdialysis probes were implanted in the jugular vein and in the frontal cortex and dialysis samples were simultaneously collected from both sites. Pharmacokinetic parameters were calculated after a 10 mg/kg intravenous dose of [14C]SDZ ICM 567. The elimination half lives measured in whole blood, brain and blood microdialysates were similar (congruent to 1.7 h). The AUC0-5h corresponding to the unbound drug was 462 +/- 142 ng.ml-1.h in blood dialysate, not significantly different from the AUC corresponding to the free concentration in whole blood, i.e. 586 +/- 63 ng.ml-1.h. The free fraction in blood obtained in vitro by equilibrium dialysis (21%) or by microdialysis (19%) was not statistically different from that obtained in vivo (17%) in microdialysis experiments. The unbound concentrations (AUC0-5h) of SDZ ICM 567 in the brain cortex were 86 +/- 24 ng.ml-1.h, lower than those expected from unbound blood concentrations, suggesting an active transport out of the central nervous system. Finally, microdialysis sampling allowed the determination of pharmacokinetic parameters of SDZ ICM 567 in blood and brain as well as the estimation of the free fraction of drug in blood.

Animals↗
PubMed1995

Effects of Bay K 8644 in aorta from spontaneously hypertensive and Wistar Kyoto rats of different ages.

1. The Ca(2+)-channel agonist, Bay K 8644, induced small contractions in aortae from Wistar-Kyoto (WKY) rats of 5-week-, 3-month-, 1-year- and 1.5-year-old, which were unaltered with age. These contractions were increased by partial depolarization with 15 mM K+. 2. In segments from spontaneously hypertensive rats (SHR), the contractions obtained in both situations were similar and equivalent to those observed in segments from normotensive animals partially depolarized. Responses to Bay K 8644 were modified by age only in tissues from the SHR, the responses to this agent in basal conditions being increased in tissues from 3-month- and 1-year-old animals and depressed in those from 1.5-year SHR. 3. A reduction of the response to Bay K 8644 was observed in partial depolarized endothelium denuded segments from WKY of all ages, and no modification in basal situation. However, the direct contractions induced by Bay K 8644 in aortae from 3-month- and 1.5-year-old SHR were reduced by endothelium removal. 4. These results suggest that: (a) in the hypertensive strain the voltage-gated Ca2+ channels seem to be partially activated; (b) the direct contractions induced by Bay K 8644 were unaltered by age in aortae from WKY but increased in tissues from SHR of 3-month-and-1-year old and depressed in those from 1.5 years, and (c) the contractions evoked by Bay K 8644 seem to involve an endothelium-derived contracting factor in aortae from both strains, or the endothelium produces a partial depolarization of vascular smooth muscle that increases the responsiveness to Bay K 8644.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1995

Diagnosis of genital infection caused by human papillomavirus using in situ hybridisation: the importance of the size of the biopsy specimen.

AIM: To determine the size of a cervical biopsy specimen with human papillomavirus (HPV) infection required to enable in situ hybridisation to be carried out with a guarantee of a reliable result. METHODS: In situ hybridisation was carried out in 142 cervical uterine biopsy specimens classified histologically as low grade and high grade squamous intraepithelial lesions. Epithelial length at the level of the basal membrane was measured by image analysis. The specimens were divided into 10 groups based on epithelial length. RESULTS: Of the biopsy specimens, 61.2% were HPV positive. In specimens with an epithelial length below 5 mm 31.9% were HPV positive; in those between 5 and 9 mm in length 67.5% were HPV positive; and in those greater than 9 mm in length 81.8% were positive for HPV. For low grade squamous intraepithelial lesions (n = 90), 68.4% of specimens with an epithelial length greater than 5 mm were HPV positive. For high grade squamous intraepithelial lesions (n = 52), 86.8% of specimens with an epithelial length greater than 5 mm were HPV positive. CONCLUSIONS: For a diagnosis of HPV infection using in situ hybridisation, the minimum length of epithelium in a cervical biopsy specimen should be 5 mm. For high grade squamous intraepithelial lesions, specimens over 5 mm in length are suitable. For low grade squamous intraepithelial lesions, to minimise the number of false negative results, the ideal minimum length is 10 mm.

Biopsy↗
PubMed1995

Immunohistochemical demonstration of taurine in the rat cerebellar cortex. Evidence for its location within mossy fibers and Golgi axons.

Taurine, 2-aminoethanesulfonic acid, is one of the most abundant amino acid present in the Central Nervous System. Nevertheless, its functions are remain uncertain. Taking as a basis the immunocytochemical pre-embedding PAP-techniques for demonstrating Taurine-Like substances on cerebellar cortex of rats we have observed positive immunoreaction within Purkinje cell bodies and their dendrites. Likewise, taurine has been demonstrated within mossy fibers and Golgi axons, as well as in glial processes. Our results demonstrate the wide distribution of Taurine in the cerebellar cortex, justifying its possible involvement as an inhibitory neurotransmitter, neuromodulator or as a gliotransmitter.

Animals↗
PubMed1995

L-aspartate aminotransferase and L-asparaginase in rat lymph node: a histoenzymological and immunohistochemical study.

L-asparaginase and L-aspartate aminotransferase are both involved in the synthesis of L-aspartic acid. It has been observed that L-asparaginase is involved in the immunosuppressor morphine-dependent syndrome in lymphoid cells whereas L-aspartic acid blocks the development of this syndrome. The aim of the present study was to clarify the localization of L-AATase activity and L-asparaginase in rat lymph nodes using histoenzymological and immunohistochemical methods, respectively. No positive reaction was demonstrated for L-AATase while L-asparaginase shown to be present in lymphocytes and lymphoblastic cells. These observations lead us to suggest that L-asparaginase is the enzyme mainly responsible for the synthesis of the L-aspartic acid necessary for satisfying the living requirements of lymphoid cells. Therapeutically administered L-asparaginase could exert its action intracellularly after crossing the cell membrane.

Animals↗
PubMed1994

Biodegradable microspheres as controlled-release tetanus toxoid delivery systems.

Purified tetanus toxoid, a high-molecular-weight protein, was entrapped within poly(L-lactic acid) (PLA) and poly(D,L-lactic/glycolic acid) (PLGA) microspheres prepared by either a solvent extraction or a solvent evaporation method carried out in a multiple emulsion system (water-in-oil-in-water). The physical integrity and antigenicity of the protein treated under different processing conditions were investigated. A reduction of antigenicity that was related to the percentage of aggregated protein was noticed under some experimental conditions. This partial loss of antigenicity was associated with the lyophilization process and affected by the nature of the organic solvent. All types of microspheres prepared with different molecular weight PLA and PLGA displayed a high protein-loading efficiency (> 80%) but their size was strongly influenced by polymer molecular weight (3000 versus 100,000). Protein release pattern was influenced by both polymer molecular weight and composition (PLA versus PLGA). A constant release pattern after an induction period of 10 days was observed for microspheres composed of high-molecular-weight polymers (PLA and PLGA). The release rate was lower from PLA microspheres than from PLGA microspheres. In contrast, a continuously increasing release rate preceded by a burst was observed for low-molecular-weight (3000) PLGA microspheres. Microencapsulated tetanus toxoid was significantly more immunogenic in mice than fluid toxoid as determined by IgG anti-tetanus antibody levels and neutralizing antibodies. However, the magnitude and duration of the antibody response did not differ significantly from a similar dose of aluminium phosphate-adsorbed toxoid. We conclude that microencapsulated tetanus toxoid shows significant adjuvant activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Novel approaches to controlled-release antigen delivery.

Two strategies for vaccine-delivery systems, both relying on concepts of controlled-release technology, are described in this review. The first strategy involves using biodegradable polymer microspheres for parenteral and oral delivery of antigens. The other strategy combines two technologies, the encapsulation of antigen within liposomes and liposome encapsulation in hydrogels, to protect them from a rapid degradation in vivo. Both strategies have shown promise in terms of increasing the immunogenicity of poorly immunogenic peptides and protein vaccines. The microencapsulation process, antigen stability, mechanism of antigen release, and optimal release kinetics for vaccine delivery are reviewed, and the strengths and weaknesses of each approach are discussed.

Antigens↗
PubMed1994

Development and characterization of microencapsulated microspheres.

A process for the coating of polymer microspheres with the same or different polymers and the characterization of these particles is described. Coated microspheres were manufactured from degradable and non-degradable polymers. Several physicochemical methods were used to establish that the particles were fully coated. Polarized light microscopy revealed strong birefringence of coated microspheres resulting in the appearance of Maltese Crosses on coated microspheres. After staining the core and the coating of particles using different fluorescent dyes, the uneven distribution of the dyes in the core and on the surface allows one to verify the coating success. After cutting microspheres using a cryomicrotome we were able to assess the microstructure of the coated microspheres. Electron Spectroscopy for Chemical Analysis (ESCA) was used to determine the surface composition of coated microspheres. Determining the carbon and oxygen content of samples we were able to verify the completeness of the coating procedure. To examine the benefit of coating microspheres, the effect of coating on the release of tetanus toxoid from polylactide microspheres was studied as a possible pharmaceutical application.

Delayed-Action Preparations↗
PubMed1994

Gastrointestinal leishmaniasis in human immunodeficiency virus-infected patients: report of five cases and review.

We describe five cases of gastrointestinal leishmaniasis in patients with human immunodeficiency virus infection and review 10 additional cases reported in the literature. All of the patients had CD4+ cell counts of < 200/mm3, and AIDS had been previously diagnosed for 12 patients. Fever and splenomegaly were present in 46% of cases. Thirteen patients had digestive symptoms; these symptoms included diarrhea (6), dysphagia and/or odynophagia (6), abdominal pain (2), epigastric pain (2), gastrointestinal hemorrhage (1), and rectal discomfort (1). The regions of the digestive tract most frequently affected by Leishmania organisms were the duodenal mucosa (90%) and the gastric mucosa (75%). Endoscopy showed normal-appearing mucosa in 45% of cases. In 10 cases the diagnosis of visceral leishmaniasis was first made by biopsy of the gastrointestinal mucosa. In most cases treatment with antimonial agents was not effective.

AIDS-Related Opportunistic Infections↗
PubMed1994

Muscarinic receptors involved in modulation of norepinephrine release and vasodilatation in guinea pig carotid arteries.

Acetylcholine (ACh, 1-50 microM) and carbachol (1-10 microM) concentration-dependently enhanced the electrically evoked tritium overflow in guinea pig carotid arteries preincubated with [3H]norepinephrine (NE). However, lower concentrations of ACh and carbachol (0.05 and 0.1 microM) slightly reduced this overflow. Phentolamine (1 microM) potentiated the inhibitory and reduced the facilitatory effects of ACh, whereas hexamethonium (300 microM) did not modify either effect. Several muscarinic receptor antagonists shifted both ACh effects to the right. The order of potencies (apparent pKb values) was, for the facilitatory effect, atropine (10.14) > pirenzepine (8.66) > p-fluoro-hexahydrosila-difenidol (p-F-HHSiD) (6.82) > or = to methoctramine (6.33), and the order for the inhibitory effect in the presence of phenotolamine was atropine (10.00) > methoctramine (7.86) > or = to AF-DX 116 (7.70) > pirenzepine (6.72) > p-F-HHSiD (6.00). ACh (0.01-10 microM) induced endothelium-dependent vasodilatation in perfused segments of guinea pig carotid arteries, and this effect was competitively inhibited by the above-mentioned muscarinic receptor antagonists. The order of potencies (pA2 values) was atropine (9.96) > p-F-HHSiD (8.05) > pirenzepine (7.64) > methoctramine (6.83). These results suggest that the noradrenergic nerve endings in guinea pig carotid arteries possess M2 inhibitory and M1 facilitatory muscarinic receptors that modulate NE release, and the endothelial cells possess M3 muscarinic receptors that mediate ACh-induced vasodilatation.

Acetylcholine↗
PubMed1994

Light and electron microscopic immunolocalization of L-asparaginase in the rat central nervous system.

The investigation on the localization of L-asparaginase, the enzyme involved in the synthesis of L-aspartic acid, has been carried out using the immunohistochemical method. Antibodies against this enzyme were obtained immunizing BALB/c mice with purified Escherichia coli L-asparaginase. Light microscopic observation revealed positive immunoreactivity in the great majority of neurons and glial cells, and electron microscopic analysis demonstrated immunological localization of the enzyme in the cytosol. The ubiquitous distribution of L-asparaginase suggests its involvement in many important functions of the central nervous system.

Animals↗
PubMed1994

[Autoimmune hemolytic anemia associated with ulcerative colitis arising after colectomy].

Autoimmune hemolytic anemia is a rare, although not exceptional, complication of ulcerative colitis. This report presents a case of this association, which is noteworthy in that the hematologic picture appeared immediately after colectomy was performed due to colonic perforation. The features of the only three reported cases in which anemia developed after colectomy are reviewed, and the role of this surgical technique in the treatment of hemolytic anemia associated with ulcerative colitis is discussed. Although colectomy does not protect patients with ulcerative colitis from the onset of hemolytic anemia, we consider that proctocolectomy should be included among the therapeutic alternatives when this association is present, especially in the case of refractory colitis.

Adult↗
PubMed1993

Determinants of release rate of tetanus vaccine from polyester microspheres.

Controlled-release formulations based on poly(lactic) (PLA) and poly(lactic/glycolic) acid (PLGA) microspheres containing tetanus vaccine were designed. The polymers forming the microspheres were L-PLA of different molecular weights and DL-PLGA, 50:50. These microspheres were prepared by two solvent elimination procedures, both using a double emulsion, and were characterized for size, morphology, and toxoid release kinetics. The influence of formulation variables such as polymer type, vaccine composition, and vaccine/polymer ratio was also investigated. Both techniques yielded microspheres with similar size, morphology, and release properties. Microsphere size was dependent on the type of polymer and the presence of the surfactant L-alpha-phosphatidylcholine, which led to a reduction in microsphere size. On the other hand, the release kinetics of encapsulated protein were affected by the polymer properties (ratio lactic/glycolic acid and molecular weight) as well as by the vaccine composition, vaccine loading, and microsphere size. Moreover, for some formulations, a decrease in microsphere size occurred simultaneously, with an increase in porosity leading to an augmentation of release rate. The changes in the PLA molecular weight during in vitro release studies indicated that release profiles of tetanus toxoid from these microspheres were only marginally influenced by polymer degradation. A significant fraction of protein (between 15 and 35%) was initially released by diffusion through water-filled channels. In contrast, the decrease in the PLGA molecular weight over the first 10 days of incubation suggested that erosion of the polymer matrix substantially affects protein release from these microspheres. Among all formulations developed, two differing in microsphere size, polymer hydrophobicity, and release profile were selected for in vivo administration to mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Design of new formulations for topical ocular administration: polymeric nanocapsules containing metipranolol.

To investigate the potential of polymeric nanocapsules for ocular delivery of beta-blockers, several formulations of polyisobutylcyanoacrylate and polyepsiloncaprolactone nanocapsules containing metipranolol base were developed. These formulations differed in the polymer forming the coating and in the type and volume of the oil encapsulated. Analysis of particle-size distribution, electrophoretic mobility, and loading efficiency of the nanocapsules revealed that the type of oil is the most important factor influencing these properties. From the in vitro release studies, we concluded that drug diffusion through a dialysis membrane is delayed as a consequence of the encapsulation process. However, the release profiles were not influenced by the polymeric coating, suggesting that drug release from these systems is governed mainly by the partition of the drug between the oily core and the aqueous release medium. Nevertheless, despite the inability of the polymer coat to control the release of the drug, its contribution to the stabilization of the emulsion was noted. Finally, the suitability of these formulations for ophthalmic administration was investigated. Although the pharmacologic response was not affected by the encapsulated metipranolol compared with the commercial eye drops, a drastic reduction of the drug's systemic side effects was observed.

Animals↗