Biomedical subjects

A López-Bravo

Publications and source records attributed to A López-Bravo.

17 recordsLinked to original sources

PubMed2007

Acrylic bone cements with bismuth salicylate: Behavior in simulated physiological conditions.

In a previous work, we reported the development of acrylic bone cement formulations for application in percutaneous vertebroplasty, by using bismuth salicylate (BS) as the radiopaque agent. Our objective was to obtain high radiopacity along with a therapeutical effect produced by the release of salicylic acid in situ. To follow that study, the setting kinetics and static and dynamical mechanical properties of the BS cements were studied in simulated physiological conditions. Moreover, radiopacity after various times of immersion in saline and the wettability of the cements surfaces were determined. The study finished with the analysis of the biological response. From the results, it can be concluded that physiological conditions did not affect negatively to the cements performance, since all BS-loaded cements fulfilled the ISO standard requirements. Radiopacity of the formulations was maintained over time and cements with BS were found to be biocompatible.

Acrylates↗

PubMed2004

Injectable self-curing bioactive acrylic-glass composites charged with specific anti-inflammatory/analgesic agent.

Injectable bioactive acrylic formulations based on poly(methyl methacrylate) (PMMA) and different amounts of bioactive glasses in the system SiO2-CaO-Na2O-P2O5 have been prepared in the presence of the anti-inflammatory analgesic drug fosfosal, the sodium salt of 2-phosphonoxibenzoic acid, to be used in minimally invasive surgery. The injectability of the formulations evaluated according to the established protocol was around 80%. The experimental formulations provided maximum temperatures in the range 50-60 degrees C, which were lower than those of commercial acrylic bone cements currently used in percutaneous vertebroplasty (PVP). Residual monomer content of any formulation was inferior to 5%. Compressive yield strength of dry specimens was in the range 80-95 MPa, but it decreased after immersion in SBF to values in the range 30-50 MPa, due to the dissolution of the bioactive glasses and the drug in the medium. The release of fosfosal was evaluated in vitro (pH = 7.0). The release profile against time obtained from a PMMA cement was quasi-linear and the 80% of the initial amount of drug was released in 175 h. However, for bioactive cements, the 80-100% of the fosfosal charged was released in approximately 48 h, due to the dissolution of the glasses in the medium. Values of weight loss of the cements determined gravimetrically ranged between 16% and 26% depending on the initial amount of fosfosal, i.e. 20 or 30 wt%, respectively. The weight loss and the water uptake were simultaneous processes, and values of hydration degree were around 10-14%. The formation of an apatite-like layer was detected on the surface of the cements at different periods of time depending on the composition of the bioactive glasses. The cements containing the glasses with P2O5 produced the growth of the apatite layer in shorter periods of time. The presence of fosfosal accelerated the precipitation of this layer independently on the glasses. The in vivo biocompatibility studied by intramuscular implantation in rats showed the absence of an anti-inflammatory response and a fibrous layer around the implant for the cement prepared with PMMA/fosfosal which is attributed to the therapeutic action of fosfosal acting in situ. The response to cements prepared with bioactive glasses and fosfosal showed a mild inflammatory reaction with the formation of the typical fibrous capsule around the implanted material.

Analgesics↗

PubMed2003

Biocompatibility and other properties of acrylic bone cements prepared with antiseptic activators.

Acrylic bone cements prepared with activators of reduced toxicity have been formulated with the aim of improving the biocompatibility of the final material. The activators used were N,N-dimethylaminobenzyl alcohol (DMOH) and 4,4'-dimethylamino benzydrol (BZN). The toxicity, cytotoxicity, and antiseptic action of these activators were first studied. DMOH and BZN presented LD50 values 3-4 times higher than DMT, were less cytotoxic against polymorphonuclear leucocytes, and possessed an antimicrobial character, with a high activity against the most representative microorganisms involved in postoperative infections. The properties of the acrylic bone cements formulated with DMOH and BZN were evaluated to determine the influence of these activators on the curing process and the physicochemical characteristics of the cements. A decrease of the peak temperature was observed for the curing with DMOH or BZN with respect to that of one commercially available formulation (CMW 3). However, residual monomer content and mechanical properties in tension and compression were comparable to those of CMW 3. The biocompatibility of acrylic bone cements containing DMOH or BZN was studied and compared with CMW 3. To that end, intramuscular and intraosseous implantation procedures were carried out and the results were obtained from the histological analysis of the surrounding tissues at different periods of time. Implantation of rods of cement into the dorsal muscle of rats showed the presence of a membrane of connective tissue, which increased in collagen fibers with time of implantation, for all formulations. The intraosseous implantation of the cements in the dough state in the femur of rabbits, revealed a higher and early osseous neoformation, with the presence of osteoid material surrounding the rest of the cured material, for the cement prepared with the activator BZN in comparison with that obtained following the implantation of the cement cured with DMOH or DMT (CMW 3).

Alcohols↗

PubMed2001

Modulated release of cyclosporine from soluble vinyl pyrrolidone--hydroxyethyl methacrylate copolymer hydrogels. A correlation of 'in vitro' and 'in vivo' experiments.

Soluble, uncrosslinked and high molecular weight copolymers of vinylpyrrolidone, VP, with 2-hydroxyethyl methacrylate, HEMA, prepared by free radical copolymerization, are proposed as supports for the modulated release of the immunosuppressor cyclosporine. Two copolymeric systems with copolymer compositions f(VP)=0.52 (namely VP--HEMA 60--40) and 0.42 (VP--HEMA 40--60) have been prepared and tested in vitro and in vivo using rats as animal model. Micellar electrokinetic capillary chromatography, MEKC, has been used for the simultaneous detection of the polymer reabsorption and the drug release for the in vitro experiments. The composition and microstructural distribution of the copolymer system controls the solubilization rate which modulates the in vitro release of the drug (with time profiles from a few days to several weeks for the VP--HEMA 60--40 and 40--60, respectively) and the in vivo response that correlates with the previous in vitro results: the more hydrophobic implant (VP--HEMA 40--60) reverts the immune response more slowly (2--4 weeks) compared to the more hydrophilic one (VP--HEMA 60--40, 1--2 weeks).

Animals↗

PubMed2000

Hydrophilic polymers derived from vitamin E.

Vitamin E containing copolymers for biomedical applications was obtained by copolymerization reaction of vitamin E methacrylate (VEMA) with 2-hydroxyethyl methacrylate (HEMA), N,N-dimethyl acrylamide (DMA) or vinyl pyrrolidone (VP), in different experiments. High molecular weight copolymers prepared by free radical reactions initiated by azobisisobutironitrilo, AIBN, present a random distribution of vitamin E derivatives along the macromolecular chains, and the average composition depends on the initial composition of the reaction medium. The relative flexibility of the polymeric systems was analyzed measuring the glass transition temperature of copolymeric sequences and that of the pure alternating diad (Tg12) obtained by the application of the treatments proposed by Johnston and Barton to all the systems. Tg12 was higher than the average T of both homopolymers (Tg) for the VEMA-HEMA system, Tg12 was lower than Tg for the VEMA-DMA system and Tg12 was similar to Tg for the VEMA-VP system. VEMA-HEMA copolymers gave rise to hydrogels in water, acidic and alkaline media. VEMA-DMA copolymers gave rise to hydrogels in acidic medium and dissolved in water and alkaline medium. VEMA-VP copolymers were soluble in all media. The swelling of all the hydrogels fit a second order kinetics. A VEMA-HEMA hydrogel was selected for in vivo experiments in order to study the influence of vitamin E on the regeneration process of Achilles tendon. The polymeric derivatives of vitamin E stimulated the regenerative process as a consequence of the antiaging effect in the local area of application.

Acrylamides↗

PubMed2000

Hydrophilic polymers derived from vitamin E.

Vitamin E containing copolymers for biomedical applications were obtained by copolymerization reaction of vitamin E methacrylate (VEMA) with 2-hydroxyethyl methacrylate (HEMA), N,N-dimethyl acrylamide (DMA) or vinyl pyrrolidone (VP), in different experiments. High molecular weight copolymers prepared by free radical reactions initiated by azobisisobutironitrilo, AIBN, present a random distribution of vitamin E derivatives along the macromolecular chains, and the average composition depends on the initial composition of the reaction medium. The relative flexibility of the polymeric systems was analyzed measuring the glass transition temperature of copolymeric sequences and that of the pure alternating diad (Tg12) obtained by the application of the treatments proposed by Johnston and Barton to all the systems. Tg12 was higher than the average Tg of both homopolymers (Tg) for the VEMA-HEMA system, Tg12 was lower than Tg for the VEMA-DMA system and Tg12 was similar to Tg for the VEMA-VP system. VEMA-HEMA copolymers gave rise to hydrogels in water, acidic and alkaline media. VEMA-DMA copolymers gave rise to hydrogels in acidic medium and dissolved in water and alkaline medium. VEMA-VP copolymers were soluble in all media. The swelling of all the hydrogels fit a second-order kinetics. A VEMA-HEMA hydrogel was selected for in vivo experiments in order to study the influence of vitamin E on the regeneration process of Achilles tendon. The polymeric derivatives of vitamin E stimulated the regenerative process as a consequence of the antiaging effect in the local area of application.

Animals↗

PubMed1997

Duodenal leishmaniasis diagnosed by biopsy in two HIV-positive patients.

We describe two cases of duodenal leishmaniasis in patients with human immunodeficiency virus (HIV) infection, diagnosed by light and electron microscopy. The patients presented nonspecific signs and symptoms, blood cultures were sterile, and serological tests for Leishmania spp. were negative. Endoscopy showed normal-appearing mucosa in one patient and possible peptic duodenitis in the other patient. In these patients, the parasite was only detected in a duodenal biopsy specimen. In view of the unusual location of the parasite and the fact that the diagnostic and dissemination of the disease was established by means of conventional biopsy, this is not a routine procedure for the diagnosis of leishmaniasis because the classic procedures require the demonstration of antibodies and visualization in bone marrow, lymph nodes, liver and/or spleen aspirates. We decided to report these two cases to call attention to the possible finding of Leishmania amastigotes in biopsies from intestinal mucosa in HIV infected patients.

Adult↗

PubMed1996

Hepatic Morphological alterations induced by zidovudine (ZDV) in an experimental model.

Zidovudine (AZT) inhibits HIV replication. Many studies have demonstrated its toxic myopathic effect in both HIV-positive patients treated with the drug and experimental animal models. So far hepatic lesions induced by AZT have not been reported. In our study, an experimental rat model was used in which the rats were administered AZT (1 mg/ml) in drinking water; histological and ultrastructural alterations were observed in the liver of treated animals and compared with the findings in control animals. The histological alterations detected were turbid swelling, vacuolar degeneration and microvacuolar fatty degeneration of panlobular distribution; these lesions were progressively greater as the duration of treatment increased. The ultrastructural alterations detected involved the mitochondria (similar to those described in cardiac muscle), smooth and rough endoplasmic reticulum (SER and RER), and the accumulation of fat and glycogen in the hepatocytes of treated animals. The histopathological and ultrastructural findings in our experimental model suggest hepatotoxicity induced by AZT or its catabolites in treated, as compared to control animals.

Animals↗

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

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↗

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↗

PubMed1993

Synaptic and non-synaptic immunolocalization of GABA and glutamate acid decarboxylase (GAD) in cerebellar cortex of rat.

The existence of a large number of GABA receptors in the cerebellar molecular layer, and the observation of numerous punctate immunoreactive deposits of GABA synthesizing enzyme (GAD) throughout this layer, could indicate the existence of numerous axon terminals that may be involved in neurotransmission modulated by GABA. These axon terminals may be different from those considered classically as cerebellar GABAergic axon terminals. Therefore, we have reinvestigated the localization of GABA- and GAD-immunoreactivities in the cerebellar cortex of the rat with the PAP method, using different antisera obtained from rabbits immunized with GABA, baclofen and GAD. The results observed in our investigation have demonstrated GABA- and GAD-immunoreactivities in the axon terminals considered classically as GABAergic, as well as in others which, until now, have not been considered GABAergic. This fact leads us to think that the distribution of GABA or molecules structurally similar to GABA is far more extended than previously thought in the cerebellum. We have also observed both GABA- and GAD-immunoreactivities within dendrites and glial cells. These facts suggest us a possible extrasynaptic release of GABA.

Animals↗

PubMed1992

Study of infection by human papillomavirus in severe dysplasias and carcinomas in situ of the uterine cervix using immunohistochemistry and in situ hybridization.

Diagnosis of human papillomavirus (HPV) infection in uterine cervical lesions is usually based on histopathological criteria and, in some cases, is confirmed by immunohistochemistry. The recent development of in situ hybridization techniques has facilitated the detection of HPV in these lesions. Consequently, we carried out a study on 18 uterine cervical biopsy specimens histopathologically diagnosed as severe dysplasias and carcinomas in situ, using an immunohistochemical method with a rabbit polyclonal antibody against the HPV common structural antigen and in situ hybridization techniques with three biotinylated DNA probes for HPV types 6/11, 16/18, and 31/35/51. By immunohistochemistry only one case (5.5%) proved to be positive, whereas by in situ hybridization 12 HPV-positive cases were obtained (66.6%), of which 7 were positive for HPV types 16/18 (38.8%) and 6 for HPV types 31/35/51 (33.3%). One case was positive with positive with both DNA probes. From our results it can be inferred that in situ hybridization is a more sensitive technique than immunohistochemistry for confirming the presence of HPV in severe dysplasias and carcinomas in situ of the uterine cervix. Furthermore, in situ hybridization provides much more information than immunohistochemistry since it permits the identification of the HPV types causing the lesion.

DNA Probes↗

PubMed1992

[Trophic activity of neurotensin in massive intestinal resection].

Regulatory peptides are among the main factors affecting the proliferative adaptive process of the small bowel; its mechanisms of action remains unknown. An 80% small bowel resection was done in Wistar rats (250-300 g) randomly assigned to two groups: control and neurotensin (300 mu/kg). Jejunal and ileal samples were taken on day 14 post-resection and histomorphometric (villous length) and proliferative (DNA content) measures were obtained. Results show an increase in villous length in the neurotensin group but no changes in DNA content were observed. We conclude that neurotensin increases intestinal mucosal growth after massive intestinal resection in the rat.

Animals↗

PubMed1992

[The effect of resection of the jejunum and ileum on intestinal mucosal trophism. An experimental study on the rat].

Intestinal resection leads to anatomo-physiological adaptive changes in the small bowel depending on its localization and extension. Two 50% resection models were done, jejunal resection (55 cm.) and ileal resection (55 cm.), in the attempt to determine the trophic response of the remnant bowel from jejunal and ileal samples. Significant increases were seen in mucosal villous length, jejunal values were greater than ileal and the greatest values were when the whole ileum was conserved. No significant changes were observed in DNA contents. These data suggest the importance of the ileal segment in the intestinal adaptive process, especially on the jejunal segment, as well as the apparent end of this response two weeks after resection.

Animals↗

PubMedDate not supplied

Resorbable polyacrylic hydrogels derived from vitamin E and their application in the healing of tendons.

A hydrogel containing vitamin E (alpha-tocopherol) was prepared by free radical polymerization of 2-hydroxyethyl methacrylate (HEMA) and alpha-tocopheryl methacrylate (VEMA), the latter being synthesized previously to its use. The hydrogel containing 20 wt % of VEMA showed equilibrium water content in the range of those of hydrogel networks, at any pH. The swelling of the hydrogel followed Fick's law, indicating that sorption of water molecules is controlled by diffusion, although the values of diffusion coefficients for the VEMA-containing hydrogel were lower than those of poly-HEMA in any medium. Surface characterization of the VEMA-containing hydrogel revealed a decrease in the surface energy of solid owing to a decrease of the polar component mainly. The application of finely powdered xerogel of HEMA-VEMA copolymer bearing 20 wt % of the vitamin E derivative gave a very fast and positive response showing an activated regeneration capacity, probably due to the stimulation of the cellular proliferation or the more plausible effect, the cellular protection associated to the antioxidant properties of the vitamin E residue.

Journal Article↗