Biomedical subjects

A Alvarez

Publications and source records attributed to A Alvarez.

At least 19 recordsLinked to original sources

PubMed2001

Antithrombin III prevents early pulmonary dysfunction after lung transplantation in the dog.

BACKGROUND: Ischemia-reperfusion injury with the resulting inflammatory response is a devastating complication of lung transplantation; much of the tissue damage could be diminished by control of the inflammatory response. Recent studies have show that antithrombin III (AT III) has an anti-inflammatory effect in addition to its established role in the regulation of blood coagulation. Thus, we hypothesized that the administration of AT III might help to prevent ischemia-reperfusion injury after lung transplantation. METHODS AND RESULTS: The study was performed in a dog model of orthotopic lung transplantation. Dogs were randomly assigned to receive either vehicle (controls) or AT III. We observed that in control dogs, during the 180-minute period after lung transplantation, the arterial O(2) partial pressure decreased and both the alveolar-arterial O(2) difference and the pulmonary vascular resistance increased. By contrast, these parameters remained unchanged in the group of dogs receiving AT III. Dogs with transplants receiving AT III did not show an increase in cell adhesion molecules, and histological examination revealed almost an absence of inflammatory response. The administration of AT III produced a marked increase in serum prostacyclin (PGI(2)) levels, whereas in control dogs, the PGI(2) levels did not change. The beneficial effect of AT III was not observed when dogs received indomethacin to prevent the stimulation of PGI(2) release by AT III. CONCLUSIONS: Our results demonstrate that AT III prevents ischemia-reperfusion injury in a dog model of lung transplantation and that this effect is conditioned by an increase in PGI(2) production.

6-Ketoprostaglandin F1 alpha↗

PubMed2001

Immunogenicity of recombinant class 1 protein from Neisseria meningitidis refolded into phospholipid vesicles and detergent.

The possibility of eliciting bactericidal antibodies against a recombinant class 1 protein (P1) from Neisseria meningitidis, joined to the first 45 amino acids of the neisserial LpdA protein (PM82), was examined. P1 was produced in Escherichia coli as intracellular inclusion bodies, from which it was purified and reconstituted by (a) inclusion into phospholipid vesicles and detergent and (b) refolding in 0.1% SDS. When Balb/c mice were immunised, high titres of subtype-specific bactericidal antibodies against P1 were obtained in both cases. These results suggest that in spite of being a denaturing agent, it is possible to use SDS to reconstitute the P1 protein in a conformation that exposes the immunodominat regions.

Animals↗

PubMed2001

A Cdk5-p35 stable complex is involved in the beta-amyloid-induced deregulation of Cdk5 activity in hippocampal neurons.

The cdk5 and its activator p35 constitute one of the main tau-phosphorylating systems in neuronal cells. Under normal conditions for neurons, its activity is required for modulating tau involvement in neuronal polarity and in development of the mammalian central nervous system. Recently, we reported that the treatment of rat hippocampal cells in culture with fibrillary beta-amyloid (Abeta) results in deregulation of the protein kinase cdk5. The neurotoxic effects of Abeta fibrils were prevented by inhibition of cdk5 activity by butyrolactone I or by using antisense oligonucleotides that control the expression of this kinase. Here, we show that the Abeta-promoted increase of cdk5 activity is associated with changes in tau phosphorylation patterns and in the intraneuronal distribution of tau. In addition to hippocampal cells, deregulation of cdk5 was observed in other cell types. However, butyrolactone I prevented Abeta-induced cell death only in neuronal cells in which cdk5 activation was sensitive to Abeta fibrils. This lost of cdk5 regulation in hippocampal cells exposed to Abeta fibrils appears to be associated with an increase in the cdk5-p35 complex stability. Complex stabilization was sensitive to phosphorylation of cdk5. However, no changes in cdk5 and p35 mRNAs were observed, suggesting that the main effects on cdk5 occur at the posttranslational level. These studies indicate that cdk5 phosphorylation and the formation of an abnormally active cdk5-p35 complex are directly involved in the molecular paths leading to the neurodegenerative process of rat hippocampal neurons triggered by Abeta fibrils.

Amyloid beta-Peptides↗

PubMed2001

Induction of cell proliferation by cyclosporine A in primary cultures of rat hepatocytes.

Cyclosporine A (CsA) has been reported to be able to promote cell proliferation, although the precise mechanism by which CsA stimulates cell growth remains uncertain. In the present study, we examined, in hepatocyte cultures, the effect of CsA on parameters related to the cell cycle as well as the levels of proteins involved in the control and progression of the cycle. Flow cytometry analysis detected an increase in the percentage of cells involved in the S phase of the cycle, which correlated with increases in the levels of cyclins D1 and E (two G1-progression regulators), as well as in those of PCNA (proliferating cell nuclear antigen), and without modification in p27, an inhibitory protein of CDKs. We also examined in nucleus the levels of nuclear factor kappaB (a nuclear factor involved in the transcription of the cyclin D1 gene) and found that this transcription factor increased in the presence of CsA. We conclude that the increases in cyclin D1, PCNA, and cyclin E, together with the invariable level of p27, clearly show that CsA induces hepatocytes to proliferate. These results reinforce the idea of the growth-promoting effect of CsA in cultured hepatocytes.

Animals↗

PubMed2001

Akt1/PKBalpha protects PC12 cells against the parkinsonism-inducing neurotoxin 1-methyl-4-phenylpyridinium and reduces the levels of oxygen-free radicals.

The phosphatidylinositol (PI)-3 kinase-Akt/PKB survival pathway protects neurons from apoptosis caused by diverse stress stimuli. However, its protective effect against neurotoxins that produce oxidative stress and neurodegeneration has not been investigated. We analyzed the effect of this pathway on the action of the parkinsonism-inducing neurotoxin 1-methyl-4-phenylpyridinium (MPP+). Overexpression of a membrane-targeted, N-myristylated fusion protein of enhanced green fluorescence protein (EGFP) and mouse Akt1 attenuated the apoptotic effect of the neurotoxin in PC12 cells. This effect was not due to protection of mitochondrial complex I activity or restoration of energy charge. Following MPP+-treatment, myr-EGFP-Akt1-transfected cells exhibited an unaltered mitochondrial membrane potential and lower ROS levels than control cells. These results provide a new site of action of Akt/PKB at the level of the oxidative detoxifying cell machinery and suggest that this effect may be responsible in part for the resistance of myr-EGFP-Akt1-expressing cells to oxidative stress and MPP+-induced apoptosis.

1-Methyl-4-phenylpyridinium↗

PubMed2001

Single-agent therapy with oral mercaptopurine for nonlymphoid blast crisis of chronic myeloid leukemia.

Currently, no effective treatment is available for the nonlymphoid blast crisis (BC) of chronic myeloid leukemia (CML) and because of this the prognosis for such patients remains invariably poor. In an attempt to determine the results provided by palliative treatment with oral 6-mercaptopurine (6-MP) in the above hematological condition, 30 such patients were analyzed for hospital stay, days of intravenous (i.v.) antibiotics, transfusion requirements, response rate, and survival. Thirty patients with nonlymphoid BC matched for their initial characteristics and treated with different i.v. regimens were used for comparison purposes. Patients managed with 6-MP spent less days in hospital (median: 9, range: 0-46 vs median: 42, range: 5-140; P<0.0001), needed antibiotics for less days (median: 0. range: 0-46 vs median: 20, range: 0-57; P<0.0001), and received less platelet transfusions (median: 0, range: 0-20 vs median: 6, range: 0-63; P=0.004) than those treated with i.v. chemotherapy. Although no complete or partial remission was achieved by patients receiving 6-MP vs six in the i.v. chemotherapy group, no significant difference was observed when the survival of both groups was compared (median: 4.7 months, range: 0.1-22.7 vs median: 3.8 months, range: 0.2-12, respectively). These results indicate that 6-MP therapy constitutes a good palliative treatment for patients with nonlymphoid BC of CML. However, new treatment strategies for this hematological condition are required.

Administration, Oral↗

PubMed2001

Prediction of early bronchopleural fistula after pneumonectomy: a multivariate analysis.

BACKGROUND: The aim of this study was to determine independent risk factors for early bronchopleural fistula (BPF) after pneumonectomy and to assess the efficacy of bronchial coverage in preventing this complication. METHODS: We reviewed 242 consecutive patients undergoing pneumonectomy for lung cancer. The bronchial stump was covered with autologous tissue in 178 patients (74%). Perioperative data were recorded to identify risk factors of BPF by univariate and multivariate analyses. RESULTS: Overall morbidity and mortality rates were 59% and 5.4%, respectively. The incidence of BPF was 5.4%. By univariate analysis, patients with chronic obstructive pulmonary disease (COPD; p = 0.017), hyperglycemia (p = 0.003), hypoalbuminemia (p = 0.017), previous steroid therapy (p < 0.001), poor predicted postpneumonectomy forced expiratory volume in 1 second (FEV1; p = 0.012), long bronchial stumps (p < 0.001), and mechanical ventilation (p = 0.015), were related with higher risk of BPF. In the multiple logistic regression model, the independent risk factors of BPF were the bronchial stump coverage and length, side of pneumonectomy, predicted postpneumonectomy FEV1, COPD, and mechanical ventilation. CONCLUSIONS: Bronchial stump coverage is highly recommended in all cases to minimize the risks of BPF. A shorter length of the bronchial stump and early extubation may prevent the development of BPF. Careful attention must be paid to those patients with COPD and poor predicted postpneumonectomy FEV1.

Adult↗

PubMed2001

Anti-inflammatory effect of Pimenta racemosa var. ozua and isolation of the triterpene lupeol.

Pimenta racemosa var. ozua (Myrtaceae) is a tropical plant, used in different inflammatory processes by the folk medicine of the Caribbean region. From the methanol extract of the leaves a terpenic compound identified as lupeol has been isolated for the first time in this species. The anti-inflammatory activity of the extract has been evaluated against two experimental models of acute inflammation: paw edema in rats, using carrageenan or dextran as phlogogen agents, and ear edema in mice, inducing the inflammation with 12-o-tetradecanoylphorbol acetate (TPA). Myeloperoxidase activity (MPO) was also assayed as an indicator of leukocytary migration in the inflamed ears. In the carrageenan test, the methanol extract (125 and 250 mg kg(-1) p.o.) had a dose-dependent and significant effect at different time intervals. On the contrary, when the dextran was injected in paw, the extract did not reduce the inflammation provoked. This behavior was similar to indomethacine (25 mg kg(-1)) used as a standard drug. In the TPA-induced ear edema, the methanol extract (0.5, 1 and 3 mg ear(-1)) significantly reduced the inflammation. In the MPO assay a significant inhibition of the enzyme was observed in the inflamed tissue in all the samples assayed. These results show that the methanol extract from the leaves of Pimenta racemosa var. ozua, is effective against acute inflammation processes, by oral route and when topically applied. The anti-inflammatory behavior of the extract was similar to that exhibited by the selective cyclo-oxygenase inhibitor, indomethacin. On the other hand, the reduction of MPO activity shows that the action mechanism is clearly related with the neutrophil migration.

Animals↗

PubMed2001

Airway complications after lung transplantation: a review of 151 anastomoses.

OBJECTIVE: To analyze the incidence, treatment and follow up of airway complications after lung transplantation. METHODS: From October 1993 to April 2000, 104 lung transplants were performed in 101 patients. One hundred and fifty one bronchial anastomoses at risk were included in the study (29 single lung and 61 sequential double lung). Donor lungs were flushed both antegradely and retrogradely with Eurocollins. In the recipients, either a single or a sequential bilateral lung transplantation was performed when indicated. The bronchial anastomosis was telescoped and covered with peribronchial tissue in all cases. Postoperative fiberoptic bronchoscopic examinations were dictated by clinical grounds. Recipient variables were recorded and analyzed to assess possible differences between both complicated and non-complicated groups. RESULTS: Eight bronchial anastomotic complications (5.3%) occurred in six patients (6.8%). All complicated cases developed in sequential bilateral lung recipients (P=0.08): stenosis (n=5), granulation tissue (n=2), and bronchial dehiscence (n=1). Treatment consisted of lobectomy and subsequent completion pneumonectomy in one patient, rigid bronchoscopy dilation in two, balloon bronchodilation in two, laser debridement and stenting in one, and conservative therapy in two cases. One patient with severe sepsis and bronchial dehiscence died on day +30. The rest of the patients remain well so far. Airway complications were related to longer intubation periods (P<0.01). Other perioperative donor and recipient factors including the incidence of infections and acute rejection episodes, and actuarial survival, did not differ between groups. CONCLUSION: In our experience, the incidence of airway complications after lung transplantation is 5.3%. The careful surgical technique and organ preservation, the close surveillance of rejection and infection, and early postoperative extubation might play a role in reducing this incidence. Either surgical therapy or bronchoscopic dilation and stenting methods may contribute to resolve these complications.

Adolescent↗

PubMed2001

Angiotensin II is involved in nitric oxide synthase and cyclo-oxygenase inhibition-induced leukocyte-endothelial cell interactions in vivo.

1. Chronic inhibition of nitric oxide synthase (NOS) provokes a hypertensive state which has been shown to be angiotensin II (Ang-II) dependent. In addition to raising blood pressure, NOS inhibition also causes leukocyte adhesion. The present study was designed to define the role of Ang-II in hypertension and in the leukocyte-endothelial cell interactions induced by acute NOS or cyclo-oxygenase (COX) inhibition using intravital microscopy within the rat mesenteric microcirculation. 2. While pretreatment with an Ang-II AT(1) receptor antagonist (losartan) reversed the prompt increase in mean arterial blood pressure (MABP) caused by indomethacin, it had no effect on the increase evoked by systemic L-NAME administration. 3. Pretreatment with losartan inhibited the leukocyte rolling flux, adhesion and emigration which occurs after 60 min NOS inhibition by 83, 80 and 70% respectively, and returned leukocyte rolling velocity to basal levels. 4. Losartan significantly reduced the leukocyte-endothelial cell interaction elicited by COX inhibition. In contrast, leukocyte recruitment induced by acute mast cell activation was not inhibited by losartan. 5. AT(1) receptor blockade also prevented the drop in haemodynamic parameters such as mean red blood cell velocity (V(mean)) and shear rate caused by NOS and COX inhibition. 6. In this study, we have demonstrated a clear role for Ang-II in the leukocyte-endothelial cell interactions and haemodynamic changes which arise in the absence of NO or prostacyclin (PGI(2)). This is of interest since leukocyte recruitment, which culminates in the vascular lesions that occur in hypertension, atherosclerosis and myocardial ischemia-reperfusion injury, might be prevented using AT(1) Ang-II receptor antagonists.

Angiotensin II↗

PubMed2001

Cyclic AMP elevating agents and nitric oxide modulate angiotensin II-induced leukocyte-endothelial cell interactions in vivo.

Angiotensin (Ang-II) is a key molecule in the development of cardiac ischaemic disorders and displays proinflammatory activity in vivo. Since intracellular cyclic nucleotides elevating agents have proved to be effective modulators of leukocyte recruitment, we have evaluated their effect on Ang-II-induced leukocyte-endothelial cell interactions in vivo using intravital microscopy within the rat mesenteric microcirculation. Pretreatment with iloprost significantly inhibited (1 nM) Ang-II-induced increase in leukocyte rolling flux, adhesion and emigration at 60 min by 96, 92 and 90% respectively, and returned leukocyte rolling velocity to basal levels. Pretreatment with salbutamol or co-superfusion with forskolin exerted similar effects. When theophylline was administered, leukocyte rolling flux, adhesion and emigration elicited by Ang-II were significantly attenuated by 81, 89 and 71% respectively. Rolipram administration caused similar reduction of Ang-II-induced leukocyte responses. Co-superfusion of Ang-II with the NO-donor, spermine-NO, or 8-Br-cyclic GMP, or pretreatment with a transdermal nytroglycerin patch, resulted in a significant reduction of the leukocyte-endothelial cell interactions elicited by Ang-II. Salbutamol preadministration did not modify leukocyte-endothelial cell interactions elicited by either L-NAME or L-NAME+Ang-II, indicating that the inhibitory leukocyte effects caused by cyclic AMP-elevating agents are mediated through NO release. In conclusion, we have provided evidence that cyclic AMP elevating agents and NO donors, are potent inhibitors of Ang-II-induced leukocyte-endothelial cell interactions. Thus, they could constitute a powerful therapeutical tool in the control of the leukocyte recruitment characteristic of the vascular lesions that occur in cardiovascular disease states where Ang-II plays a critical role.

Analysis of Variance↗

PubMed2001

Safety and preliminary immunogenicity of the recombinant outer membrane protein P64k of Neisseria meningitidis in human volunteers.

P64k is a meningococcal protein from Neisseria meningitidis that has been obtained by recombinant DNA technology. Recombinant P64k has been extensively characterized by physicochemical and immunological methods. Lately this protein has been found to act as a versatile immunological carrier for weak antigens in mice. In the present work, a Phase I clinical trial was carried out in healthy volunteers who received three inoculations of either placebo or recombinant P64k (20 or 50 microg). No severe adverse events occurred during the trial. Only mild adverse events in ten volunteers were observed. At 1 month after the third dose, 15 out of 18 volunteers (83.3%) who received the recombinant antigen had a P64k-specific antibody titre > or =1:100, as detected by ELISA. A fourth dose, given 9 months after the third one, elicited a potent booster immune response in P64k vaccinees. Accordingly, these P64k formulations were considered safe and immunogenic in healthy human volunteers.

Adult↗

PubMed2001

Solution structure of the lipoyl domain of the chimeric dihydrolipoyl dehydrogenase P64K from Neisseria meningitidis.

The antigenic P64K protein from the pathogenic bacterium Neisseria meningitidis is found in the outer membrane of the cell, and consists of two parts: an 81-residue N-terminal region and a 482-residue C-terminal region. The amino-acid sequence of the N-terminal region is homologous with the lipoyl domains of the dihydrolipoyl acyltransferase (E2) components, and that of the C-terminal region with the dihydrolipoyl dehydrogenase (E3) components, of 2-oxo acid dehydrogenase multienzyme complexes. The two parts are separated by a long linker region, similar to the linker regions in the E2 chains of 2-oxo acid dehydrogenase complexes, and it is likely this region is conformationally flexible. A subgene encoding the P64K lipoyl domain was created and over-expressed in Escherichia coli. The product was capable of post-translational modification by the lipoate protein ligase but not aberrant modification by the biotin protein ligase of E. coli. The solution structure of the apo-domain was determined by means of heteronuclear NMR spectroscopy and found to be a flattened beta barrel composed of two four-stranded antiparallel beta sheets. The lysine residue that becomes lipoylated is in an exposed beta turn that, from a [1H]-15N heteronuclear Overhauser effect experiment, appears to enjoy substantial local motion. This structure of a lipoyl domain derived from a dihydrolipoyl dehydrogenase resembles that of lipoyl domains normally found as part of the dihydrolipoyl acyltransferase component of 2-oxo acid dehydrogenase complexes and will assist in furthering the understanding of its function in a multienzyme complex and in the membrane-bound P64K protein itself.

Amino Acid Sequence↗

PubMed2001

Correlation of atrophy measures on MRI with neuropsychological sequelae in children and adolescents with traumatic brain injury.

To examine the relationship between neuropsychological sequelae and atrophy parameters from magnetic resonance imaging (MRI) following paediatric moderate-to-severe traumatic brain injury (TBI), 19 head injured children and adolescents were studied at least 6 years after injury. Three-dimensional MRI scans were obtained. A semi-automatic computerized method was used to estimate ventricular volumes and the corpus callosum area. Tests of intellectual, memory, visuospatial, frontal lobe, and motor speed functioning were administered to all patients and to 19 matched normal control subjects. Patients' performance significantly differed from controls in general intellectual function, visual memory, visuospatial and frontal lobe tests. The corpus callosum area correlated strongly with several measures involving processing speed and visuospatial function. Ventricular enlargement was less related to neuropsychological outcome. In conclusion, quantitative measurement of the corpus callosum on MRI reflects neuropsychological outcome better than ventricular dilation in paediatric patients.

Adolescent↗

PubMed2001

Complications of outpatient parenteral antibiotic therapy in childhood.

Complications in children receiving outpatient parenteral antibiotic therapy were reviewed. Catheter-associated complications and/or adverse drug reactions occurred in 50% of courses. Most complications were minor, and almost all infections were successfully treated. Even with early discontinuation of parenteral antibiotics because of adverse drug reactions in 24% of the courses, the outcome was excellent.

Ambulatory Care↗

PubMed2001

Gastrointestinal, liver, and pancreatic involvement in adult patients with cystic fibrosis.

BACKGROUND: The clinical prevalence of cystic fibrosis (CF) in adults continues to rise, with a consequent impact on adult gastroenterology practice. AIM: To characterize the gastrointestinal manifestations of CF in adult patients. PATIENTS AND METHODS: The clinical records of 89 adult CF patients treated at our institution from 1992 to 1999 were reviewed. Patients were distributed into two groups: group A (39 patients), which consisted of patients who were diagnosed with CF at when they were younger than 14 years old and who survived into adulthood; and group B (50 patients), who were diagnosed with CF at the age of 14 years or older. Data on CF genetic mutations, nutritional state, evidence of pulmonary, gastrointestinal, liver, or pancreatic involvement were collected for each patient. RESULTS: The most prevalent genetic mutation in our series was deltaF508, present in 50 patients (56.2%), 29 of whom belonged to group A and 21 who belonged to group B. In group A, the deltaF508 mutation was associated with exocrine pancreatic insufficiency (PI) in 26 of 29 patients (89.6%), whereas in group B it was associated with PI in only four patients (19%). Overall, PI was present in 33 of 39 patients (84.6%) in group A and in eight of 50 patients (16%) in group B. Four patients in group B had experienced previous episodes of acute pancreatitis; two of them had associated PI. Of the 89 patients, 12 (10 in group A) were malnourished. Malnutrition was invariably associated with PI. Hepatic and biliary tree abnormalities were particularly prevalent in patients in group A and was usually associated with PI. Intestinal manifestations were uncommon. CONCLUSIONS: Diagnosis of CF before the age of 14 years is associated with greater gastrointestinal compromise than diagnosis at an older age, particularly with regard to PI. CF carriers of the deltaF508 mutation have an increased risk of developing gastrointestinal manifestations.

Acute Disease↗

PubMed2001

Prevalence of human immunodeficiency virus type 1 (HIV-1) non-B subtypes in foreigners living in Madrid, Spain, and comparison of the performances of the AMPLICOR HIV-1 MONITOR version 1.0 and the new automated version 1.5.

Plasma specimens collected in 1999 from 32 human immunodeficiency virus type 1 (HIV-1)-infected foreigners living in Madrid, Spain, were examined for the presence of non-B subtypes. Furthermore, plasma viremia was quantified using two different AMPLICOR HIV-1 MONITOR tests, version 1.0 and the new upgraded and automated version 1.5 (COBAS). Most patients came from Africa, where they most likely had acquired HIV-1 infection through sexual contact. HIV-1 genetic subtyping was based on the phylogenetic analysis of the protease gene. Twenty-two subtype B, six subtype G, two subtype C, one subtype A, and one D subtype infection were found. Overall, non-B subtypes represented 31.25% of the study population. Irrespective of the HIV-1 variant, viral load values above the detection limit (200 HIV RNA copies/ml) increased from 56.2 to 71.9% for results obtained using MONITOR version 1.0 and COBAS, respectively. Moreover, significant differences in viral load values (>0.5 logs) were recognized in up to 37.5% of samples. In summary, COBAS seemed to be more reliable for testing plasma viral load in HIV-infected immigrants living in Spain, one third of whom carried non-B subtypes.

Adult↗

PubMed2001

Reactive oxygen species mediate angiotensin II-induced leukocyte-endothelial cell interactions in vivo.

Chronically elevated angiotensin II (Ang-II)-induced hypertension is partly mediated by superoxide production. In this study, we have investigated whether the leukocyte-endothelial cell interactions elicited by Ang-II involve reactive oxygen species (ROS) generation. Intravital microscopy within the rat mesenteric microvessels was used. Superfusion (60 min) with Ang-II (1 nM) induced significant increases in leukocyte rolling flux, adhesion, and emigration, which were inhibited by pretreatment with superoxide dismutase or catalase. Dihydrorhodamine-123 oxidation indicated that ROS are primarily produced by the vessel wall. Administration of dimethylthiourea, desferrioxamine, or N-acetylcysteine provoked significant reductions in Ang-II-induced leukocyte-endothelial cell interactions. In addition, a blockade of platelet-activating factor or leukotrienes also attenuated such responses significantly. The results presented indicate that in vivo Ang-II-induced leukocyte recruitment is dependent on the generation of intra- and extracellular ROS. Therefore, the use of anti-oxidants might constitute an alternative therapy for the control of the subendothelial leukocyte infiltration associated with hypertension and atherosclerosis.

Angiotensin II↗