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Biomedical subjects

N Serrano

Publications and source records attributed to N Serrano.

At least 19 recordsLinked to original sources
PubMed2005

Composite prostheses for the repair of abdominal wall defects: effect of the structure of the adhesion barrier component.

The component of a composite prosthesis, which makes contact with the visceral peritoneum, can be reabsorbable or non-reabsorbable, and laminar or reticular. This study was designed to determine whether the composition of this second, barrier component could improve its behavior at this interface. Abdominal wall defects in rabbits were repaired using a polypropylene prosthesis (PP), or the composites Sepramesh (PP + h) or Vicryl (PP + v). Fourteen days after surgery, the implants were evaluated by light and scanning electron microscopy, and immunohistochemistry. Prosthetic areas occupied by adhesions (PP: 71.08 +/- 5.09, PP + h: 18.55 +/- 4.96, P + v: 69.69 +/- 16.81%), neoperitoneal thickness (PP: 256.17 +/- 21.68, PP + h: 83.11 +/- 19.63, PP + v:213.72 +/- 35.90 microm) and macrophage counts (PP: 8.73 +/- 1.16, PP + h: 27.33 +/- 4.13, PP + v: 31.24 +/- 3.08%) showed significant differences (P < 0.05). The tested biomaterials induced an optimal recipient tissue infiltration. Least adhesion formation was observed on the PP + h implants. This suggests that the second component, although reabsorbable, should be smooth in structure.

Abdominal Wall↗
PubMed2005

Composite prostheses used to repair abdominal wall defects: physical or chemical adhesion barriers?

In a composite prosthesis, the component placed at the peritoneal interface takes the form of a physical or chemical barrier. In this experimental study performed on the white New Zealand rabbit, several composites were examined to establish the effectiveness of these barriers at impeding adhesion formation. The biomaterials tested were two polypropylene prostheses (PP) with the physical barriers of expanded polytetrafluoroethylene or polyurethane (PP + ePTFE and PP + PU) and two prostheses (one polyester and the other PP) with the absorbable chemical barriers of polyethylene glycol/glycerol and hyaluronate, respectively (PO + gl and PP + hy). The composites were used to repair 7 x 5 cm defects created in the abdominal wall of the animals by placing the implant in contact with the visceral peritoneum and the subcutaneous tissue and fixing it to recipient tissue by 4/0 polypropylene running suture. Fourteen days after surgery the animals were sacrificed and specimens were taken for light microscopy and scanning electron microscopy. Adhesions developing at the prosthesis/visceral peritoneal interface were quantified. All the prostheses induced optimal mesothelialization. Composites with physical barriers behaved similarly in terms of provoking adhesions. However, the prostheses with chemical barriers differed in their effectiveness at preventing adhesions. Overall, the best results were obtained with the PP + PU composite.

Abdominal Wall↗
PubMed2005

Patency and structural changes in cryopreserved arterial grafts used as vessel substitutes in the rat.

OBJECTIVE: To evaluate the patency and structural changes that occur in the short- and mid-term when cryopreserved syngenic arterial grafts are implanted in an experimental animal model. MATERIAL AND METHODS: Segments of iliac artery from the Spraque-Dawley rat were cryopreserved in a biological freezer according a controlled, computerized freezing protocol whereby the specimens are cooled at a rate of 1 degrees C/min. After storage at -145 degrees C in liquid N2 vapor for 30 days, the cryografts were slowly thawed. These vessels were grafted to the common iliac artery in syngenic animals. The following study groups were established: group I (GI), non-implanted cryografts; group II (GII), autografts; and group III (GIII), cryoisografts. The control group (CG) was comprised of fresh iliac arteries. The animals were sacrificed 14, 30, or 90 days post-surgery. At each of these follow-up times, graft specimens were morphologically evaluated by light and scanning and transmission electron microscopy and immunolabeling of endothelial cells (vWf). Cell damage attributed to the cryopreservation or grafting process was also determined. RESULTS: At the time of sacrifice, graft patency was 100% for the autografts, while 26.6% of the cryoisografts showed fully occlusive thrombosis. Among other complications, two pseudoaneurysms were detected. After cryopreservation, the grafts (GI) showed patches of endothelial denudation and good cellularity of the medial layer. The intimal hyperplasia observed in autografts implanted for 14 days (GII) was significantly delayed until day 30 when the graft was cryopreserved (GIII). Cryoisografts showed general thinning of the arterial wall and degeneration accompanied by medial layer cell loss. These grafts showed most cell damage at 90 days post-implant. Expression of the vWf in all specimens showing intimal hyperplasia was confined to the outermost graft layer. CONCLUSIONS: Cryopreservation modified the reparative response of the grafts. Owing to faster degeneration of the medial layer and a delay in the appearance of intimal hyperplasia, arterial wall thickness was reduced relative to that of the non-cryopreserved autografts. This thinning, at least in the short-term (90 days), does not seem to give rise to aneurysms owing to the generation of a neointima that stabilizes the vessel wall.

Animals↗
PubMed2003

Macrolide resistance in Streptococcus pneumoniae isolated from patients with community-acquired lower respiratory tract infections in Portugal: results of a 3-year (1999-2001) multicenter surveillance study.

A nationwide multicenter study (including 31 laboratories) of the antimicrobial susceptibility of 1210 Streptococcus pneumoniae isolates from patients with community-acquired lower respiratory tract infections (LRTI) was carried out over 3 years (1999-2001) in Portugal. Testing of all isolates was undertaken in a central laboratory. Overall macrolide resistance was 13.1%. Decreased susceptibility to penicillin was 24.5% (15.5% low-level and 9.0% high-level resistance). Taken into consideration, the resistance rates reported in a previous surveillance study of 1989-1993, a six-fold increase of erythromycin resistance in the last decade was documented. Resistance to erythromycin, clarithromycin, and azithromycin was higher in pediatric patients than in adults. The overwhelming majority (82.3%) of macrolide-resistant isolates were multidrug resistant, although 44.9% were fully susceptible to penicillin. Most macrolide-resistant isolates (80.4%) showed the MLSB phenotype (76.6% MLSB-constitutive resistance, and 3.8% MLSB-inducible resistance) and were also resistant to clindamycin, tetracycline, and co-trimoxazole. The M phenotype was seen in 19.6% isolates and these had MIC90 values of 8 mg/L for erythromycin and clarithromycin, and of 12 mg/L for azithromycin. The clinical significance of macrolide resistance in the management of LRTI is discussed. Because of the specific situation concerning macrolide resistance described in S. pneumoniae, careful use of macrolide antibiotics in therapy and cautious monitoring of macrolide resistance should be continued in Portugal.

Adult↗
PubMed2001

Using Bayesian networks in the construction of a bi-level multi-classifier. A case study using intensive care unit patients data.

Combining the predictions of a set of classifiers has shown to be an effective way to create composite classifiers that are more accurate than any of the component classifiers. There are many methods for combining the predictions given by component classifiers. We introduce a new method that combine a number of component classifiers using a Bayesian network as a classifier system given the component classifiers predictions. Component classifiers are standard machine learning classification algorithms, and the Bayesian network structure is learned using a genetic algorithm that searches for the structure that maximises the classification accuracy given the predictions of the component classifiers. Experimental results have been obtained on a datafile of cases containing information about ICU patients at Canary Islands University Hospital. The accuracy obtained using the presented new approach statistically improve those obtained using standard machine learning methods.

Algorithms↗
PubMed2001

A multicenter study of the antimicrobial susceptibility of Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis isolated from patients with community-acquired lower respiratory tract infections in 1999 in Portugal.

A nationwide multicenter study (including 25 laboratories) of the antimicrobial susceptibility of bacterial pathogens commonly associated with community-acquired lower respiratory tract infections (LRTI), with testing undertaken in a central laboratory, was conducted in Portugal in 1999. Antimicrobial resistance in Haemophilus influenzae has not increased in the last decade. Of the 498 isolates tested, 12.4% produced beta-lactamase and >95% were susceptible to all antimicrobials except ampicillin. In contrast, there was a rapid increase of resistance in Streptococcus pneumoniae. Of the 312 isolates tested, 24.7% exhibited decreased susceptibility to penicillin (13.5% showed low-level and 11.2% high-level resistance), 13.8% were resistant to erythromycin, clarithromycin and azithromycin, and 13.6% to cefuroxime and to tetracycline. Of the 38 Moraxella catarrhalis tested, 81.6% produced beta-lactamase. Resistance to penicillin, cefuroxime, erythromycin, clarithromycin, and azithromycin in S. pneumoniae and beta-lactamase production in H. influenzae were significantly higher in pediatric patients than in adults. Overall, amoxycillin/clavulanate was the most active antimicrobial agent in vitro against H. influenzae, S. pneumoniae, and M. catarrhalis isolated from patients with community-acquired LRTI in Portugal.

Adult↗
PubMed2001

Preeclampsia: from epidemiological observations to molecular mechanisms.

Preeclampsia is the main cause of maternal mortality and is associated with a five-fold increase in perinatal mortality in developing countries. In spite of this, the etiology of preeclampsia is unknown. The present article analyzes the contradictory results of the use of calcium supplementation in the prevention of preeclampsia, and tries to give an explanation of these results. The proposal of an integrative model to explain the clinical manifestations of preeclampsia is discussed. In this proposal we suggest that preeclampsia is caused by nutritional, environmental and genetic factors that lead to the creation of an imbalance between the free radicals nitric oxide, superoxide and peroxynitrate in the vascular endothelium. The adequate interpretation of this model would allow us to understand that the best way of preventing preeclampsia is the establishment of an adequate prenatal control system involving adequate antioxidant vitamin and mineral supplementation, adequate diagnosis and early treatment of asymptomatic urinary and vaginal infections. The role of infection in the genesis of preeclampsia needs to be studied in depth because it may involve a fundamental change in the prevention and treatment of preeclampsia.

Calcium, Dietary↗
PubMed2000

Acute adrenal insufficiency after cardiac surgery.

Adrenal insufficiency after cardiac surgery can easily be confused during the course of an immediate unstable postoperative period. If unrecognized, this condition may cause serious morbidity and can be fatal. We report on a 43-yr-old female patient with chronic known adrenal insufficiency, who, despite her adequate preoperative replacement therapy, presented with one episode of acute hypoadrenal crisis after elective open heart surgery, which could serve as a model to illustrate the salient clinical features and possible problems in this setting for diagnosing this problem to patients in whom chronic adrenal insufficiency remains unknown.

Acute Disease↗
PubMed1998

Molecular mechanism of polyhomeotic activation by Engrailed.

The Drosophila Engrailed homeoprotein has been shown to activate directly a Polycomb-group gene, polyhomeotic, during embryogenesis. The molecular mechanism involved in this activation has been studied. Two different types of Engrailed-binding fragments have been detected within the polyhomeotic locus. The P1 and D1 fragments contain several 'TTAATTGCAT' motifs, whereas the D2 fragment contains a long 'TAAT' stretch to which multiple copies of Engrailed bind cooperatively. Another homeodomain-containing protein, Extradenticle, establishes protein-protein interactions with Engrailed on the D2 fragment. We have shown by CAT assays that both types of Engrailed-binding sites (P1 or D1 and D2), as well as Extradenticle, are necessary to obtain activation by Engrailed. In vivo, we have also shown that normal polyhomeotic expression depends on extradenticle expression. Moreover, in the absence of Extradenticle, overexpression of Engrailed protein represses polyhomeotic expression.

Animals↗
PubMed1998

engrailed and polyhomeotic interactions are required to maintain the A/P boundary of the Drosophila developing wing.

Engrailed is a nuclear regulatory protein with essential roles in embryonic segmentation and wing morphogenesis. One of its regulatory targets in embryos was shown to be the Polycomb group gene, polyhomeotic. We show here that transheterozygous adult flies, mutant for both engrailed and polyhomeotic, show a gap in the fourth vein. In the corresponding larval imaginal discs, a polyhomeotic-lacZ enhancer trap is not normally activated in anterior cells adjacent to the anterior-posterior boundary. This intermediary region corresponds to the domain of low engrailed expression that appears in the anterior compartment, during L3. Several arguments show that engrailed is responsible for the induction of polyhomeotic in these cells. The role of polyhomeotic in this intermediary region is apparently to maintain the repression of hedgehog in the anterior cells abutting the anterior-posterior boundary, since these cells ectopically express hedgehog when polyhomeotic is not activated. This leads to ectopic expressions first of patched, then of cubitus interruptus and decapentaplegic in the posterior compartment, except for the dorsoventral border cells that are not affected. Thus posterior cells express a new set of genes that are normally characteristic of anterior cells, suggesting a change in the cell identity. Altogether, our data indicate that engrailed and polyhomeotic interactions are required to maintain the anterior-posterior boundary and the posterior cell fate, just prior to the evagination of the wing.

Animals↗
PubMed1997

Limb morphogenesis: connections between patterning and growth.

Limb development is a complex process involving precise control of both patterning and growth. Great strides have been made in understanding limb morphogenesis and identifying essential patterning genes in Drosophila. Differential expression of these genes divides the future limb into territories, which will give rise to different regions of the adult appendage. Recent analyses have defined the role of territorial boundaries as organizers of both patterning and growth, highlighting the connection between these two processes. The organizing activity of territorial boundaries seems to be mediated through the activity of two locally produced morphogens: Wingless and Decapentaplegic. We propose a model in which these two molecules, distributed in a graded fashion, act in synergy to promote growth of the entire appendage. We also suggest that existence of growth inhibitors that counteract the action of Wingless and Decapentaplegic; by opposing the gradient of these growth factors, the inhibitors guide the near-uniform proliferation that shapes the imaginal discs from which the adult appendages are formed in Drosophila.

Animals↗
PubMed1997

beta3-tubulin is directly repressed by the engrailed protein in Drosophila.

In Drosophila, Engrailed is a nuclear regulatory protein with essential roles during embryonic development. Although Engrailed is a transcription factor, little progress has been achieved in identifying its target genes. We report here the identification of an effector gene, the beta3-tubulin gene, as a direct target of Engrailed. The cytological location of beta3-tubulin, 60C, is a strong site of Engrailed binding on polytene chromosomes. Immunostaining analysis of a transgenic line containing a P[beta3-tubulin-lacZ] construct shows an additional site of Engrailed binding at the location of the transgene. Molecular analysis allowed identification of several Engrailed binding sites, both in vitro and in vivo, within the first intron of the beta3-tubulin locus. Engrailed binding sites identified in vitro are active in larvae. Furthermore, expression of beta3-tubulin is derepressed in the ectoderm of engrailed mutant embryos. Repression of beta3-tubulin by Engrailed is also obtained when Engrailed is ectopically expressed in embryonic mesoderm. Finally, two different sets of Engrailed binding sites are shown to be involved in the early and late regulation of beta3-tubulin by Engrailed during embryogenesis.

Animals↗