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Biomedical subjects

A Prat

Publications and source records attributed to A Prat.

At least 37 records · Page 2Linked to original sources
PubMed2000

Characterization of T cell lines derived from glatiramer-acetate-treated multiple sclerosis patients.

We analyzed the effects of glatiramer acetate (GA) therapy on in vitro proliferative responses and cytokine production by lymphocytes derived from multiple sclerosis patients receiving this therapy. We confirmed that lymphocytes derived from GA naïve patients show a high frequency of response when initially exposed to GA in vitro; this frequency decreased following GA therapy. The frequency of lymphocytes responding to whole MBP stimulation did not change with GA therapy. GA- and MBP-specific T cell lines generated from these patients by repeated cycles of in vitro stimulation did not cross react. Some (23%) whole MBP-reactive T cell lines did cross react with MBP peptide 83-99. The mean levels of interferon (IFN) gamma secretion and the mean ratio of IFN-gamma/IL-5 were lower for GA-reactive cell lines, derived from patients both prior to and during GA therapy, compared to MBP-reactive T cell lines. The proportion of IFN-gamma(+) cells in unfractionated lymphocyte preparations derived from the GA-treated patients did not differ from that found for healthy controls. Our findings indicate that GA-reactive T cell lines derived from GA-treated MS patients continue to show a relative Th2 cytokine bias consistent with a bystander suppressor function. GA treatment is not associated with a cytokine phenotype shift in the total T cell or MBP-reactive T cell populations.

Adult↗
PubMed2000

N-arginine dibasic convertase (nardilysin) isoforms are soluble dibasic-specific metalloendopeptidases that localize in the cytoplasm and at the cell surface.

N-arginine (R) dibasic (NRD) convertase (nardilysin; EC 3.4.24.61), a metalloendopeptidase of the M16 family, specifically cleaves peptide substrates at the N-terminus of arginines in dibasic motifs in vitro. In rat testis, the enzyme localizes within the cytoplasm of spermatids and associates with microtubules of the manchette and axoneme. NRD1 and NRD2 convertases, two NRD convertase isoforms, differ by the absence (isoform 1) or presence (isoform 2) of a 68-amino acid insertion close to the active site. In this study, we overexpressed both isoforms, either by vaccinia virus infection of BSC40 cells or transfection of COS-7 cells. The partially purified enzymes exhibit very similar biochemical and enzymic properties. Microsequencing revealed that NRD convertase is N-terminally processed. Results of immunocytofluorescence, immunoelectron microscopy and subcellular fractionation studies argue in favour of a primary cytosolic localization of both peptidases. Although the putative signal peptide did not direct NRD convertase into microsomes in an in vitro translation assay, biotinylation experiments clearly showed the presence of both isoforms at the cell surface. In conclusion, although most known processing events at pairs of basic residues are achieved by proprotein convertases within the secretory pathway, NRD convertase may fulfil a similar function in the cytoplasm and/or at the cell surface.

Animals↗
PubMed2000

[Norwalk virus-like food poisoning after eating oysters].

BACKGROUND: The aim of this study was to conduct a clinical-epidemiological and microbiological investigation into an outbreak of food-borne disease due to the consumption of oysters. PATIENTS AND METHODS: A historic cohort study was conducted into the consumption of 15 food items and clinical symptoms. The influence of each foodstuff was assessed by Mantel-Haenzel stratified relative risk (RRM-H) at 95% confidence intervals, and was confirmed by dose-response analysis with a chi 2 test tendency. We investigated sample stools from 5 patients and 2 food-handlers. RESULTS: The overall attack rate was 38.0% (19/50). The median period of incubation was 39.0 h (maxim 62 and minimum 3 h). The symptoms were: fever 17.6% (3/17), diarrhoea 57.9% (11/19), vomits 84.2% (16/19), nausea 89.5% (17/19) and abdominal pain 89.5% (17/19). In stratified analysis, the Mantel-Haenzel method revealed a statistically risk for oysters (RRM-H = 3.3; IC 95%: 1.1-8.7), while the RRM-H value for sea snails was not significant (RRM-H = 2.8; IC 95%: 0.9-41.1). For oyster consumption, the dose-response test was statistically significant (p = 0.005). Examination by electron microscopy revealed small round structured viruses compatible with Norwalk-like virus. The oyster contamination was reported to the public health authority. CONCLUSIONS: This research highlights the usefulness of dose-response analysis in presenting epidemiological evidence, reveals the potential role of oyster consumption in food-borne disease such us Norwalk-like virus and show the need for monitoring production centres and oyster beds in order to prevent further cases of contamination.

Adult↗
PubMed2000

Echocardiographic follow-up after Ross procedure in 100 patients.

The Ross procedure could provide an ideal aortic valve replacement method in children and young adults. We evaluated midterm echocardiographic results to assess pulmonary homograft function as well as pulmonary autograft dimensions and function. In all, 105 patients (26 women and 79 men) underwent the Ross procedure; median age at implant was 29 years. All patients underwent free root replacement. Transvalvular gradients and autograft dimensions were measured at 3 levels (annulus, sinuses of Valsalva, and proximal aorta) at discharge, at 6 months, and annually thereafter. Perioperative mortality was 4.7%. The mean period for echocardiographic follow-up in 100 patients was 32.7 months (range 0.5 to 7 years), during which 4 noncardiac-related deaths occurred. Two patients underwent late reintervention. No moderate or severe regurgitation was recorded. There was 1 case of mild homograft regurgitation and 4 of mild autograft regurgitation at late follow-up. Autograft peak gradients were low and reproducible (5 +/- 2.8 mm Hg at discharge vs 5.5 +/- 3.5 mm Hg at last follow-up, p = NS). Homograft peak gradients increased significantly without severe obstruction (7.8 +/- 5.7 mm Hg at discharge vs 15.8 +/- 9.2 mm Hg at last follow-up). The diameter of the autograft annulus was stable during follow-up, whereas autograft dimensions at sinuses and proximal aorta increased significantly. One group of patients was identified with sinus diameter increases >20% (group A). The 90 remaining patients were classified into group B. The only parameter significantly different between the 2 groups was the sinus diameters measured at discharge (1.74 cm/m2 (group A) vs 1.92 cm/m2 (group B); p = 0.036). In 100 patients and with echocardiographic follow-up for up to 7 years, the Ross procedure showed excellent results. For 10% of patients, we observed a 20% dilation of sinus diameters, but in only 3 patients (3%) was this beyond the upper normal limit.

Adolescent↗
PubMed2000

Brain-immune connection: immuno-regulatory properties of CNS-resident cells.

Even though the immune privileged status of the central nervous system (CNS) limits access of systemic immune cells through the blood brain barrier (BBB), an immune response can occur in this compartment with or without major breach of the BBB. In this review, we consider properties of resident cells of the CNS, that participate in regulating the neural antigen (Ag)-directed immune responses implicated in autoimmune diseases such as multiple sclerosis (MS). Under such conditions, the CNS is usually viewed as the target or victim of the immune assault, because such immune responses are thought to be initiated and regulated within the systemic immune compartment. The CNS-endogenous cells may themselves, however, initiate, regulate and sustain an immune response. We consider the immune regulatory functions within the CNS in terms of events occurring within the CNS parenchyma (microglia, astroglia) and at the vascular interface. These regulatory functions involve antigen presentation to T cells and polarization of the cytokine response of these cells. Such responses may contribute not only to the overall tissue injury in primary immune disorders but also in a wide range of traumatic, ischemic and degenerative processes.

Animals↗
PubMed2000

Effect of mitral valve surgery on exercise capacity, ventricular ejection fraction and neurohormonal activation in patients with severe mitral regurgitation.

OBJECTIVES: The purpose of this study was to prospectively investigate the effects of surgical correction of mitral regurgitation (MR) on exercise performance, cardiac function and neurohormonal activation. BACKGROUND: Little is known about the effect of surgical correction of MR on functional status or on neurohormonal activation. METHODS: Cardiopulmonary exercise test, radionuclide angiography and blood samples for assessment of neurohormonal status were obtained in 40 patients with nonischemic MR before and within one year (216+/-80 days) after surgery. Twenty-four patients underwent mitral valve repair (MVr), and 16 underwent valve replacement (VR) with anterior chordal transection. RESULTS: Despite an improvement in New York Heart Association functional class, exercise performance did not change (peak oxygen consumption: 19.3+/-6.1 to 18.5+/-5.6 ml/kg/min, percentage of maximal predicted oxygen consumption: 79.5+/-18.2% to 76.8+/-16.9%). After surgery, left ventricular (LV) ejection fraction (EF) decreased (64.2+/-10.3% to 59.9+/-11.4%, p = 0.003) while right ventricular (RV) EF increased (41.4+/-9.6% to 44.7+/-9.5%, p = 0.03). Left ventricular EF did not change after MVr (64.3+/-11.5% to 61.5+/-12.2%), but RVEF improved (40.4+/-9.2% to 46.0+/-10.0%, p = 0.02). In contrast, VR was associated with an impairment of LV function in the apicolateral area and a decrease in LVEF (64.1+/-8.5% to 57.4+/-10.0%, p = 0.01), whereas RVEF did not change (42.9+/-10.3% to 42.8+/-8.6%). Moreover, there was only a slight decrease in neurohormonal activation after surgery. CONCLUSIONS: Despite an improvement in symptomatic status, exercise performance was not improved seven months after either MVr or VR for MR, and neurohormonal activation persisted. Compared with MVr, VR resulted in a significant impairment of cardiac function in this study.

Aged↗
PubMed2000

Stentless bioprostheses have ideal haemodynamics, even in the small aortic root.

OBJECTIVE: To determine normal Doppler and 2D gradients and flow characteristics of the Freestyle stentless aortic bioprosthesis related to valve size. BACKGROUND: The Freestyle stentless aortic bioprosthesis is one of the newer aortic xenografts. Only limited data are available of the echocardiographic flow characteristics during a mid-term follow-up period of this valve. Therefore valve performance related to valve size was measured during a follow-up period of two years. METHODS: 175 consecutive patients with a Freestyle aortic bioprosthesis underwent an echocardiographic and Doppler examination according to a common protocol. Investigations were done within 4 weeks after operation, after 3 to 6 months, and after 1 and 2 years. RESULTS: With a valve size from 19 to 27 mm mean gradients decreased from 8.0 +/- 5.1 mmHg at discharge to 5.8 +/- 3.8 mmHg after 3-6 months (p < 0.001). Thereafter gradients remained stable. The performance index, the ratio of the measured effective orifice area in the patient divided by the effective orifice area measured in vitro increased from 69 +/- 20% at discharge to 79 +/- 29% after one, two and three years. Performance index was especially very high in the smaller sized valves with a performance index of 85 +/- 17% for the 21 mm valve. During follow-up mean gradients remained below 10 mmHg even in the 21 mm valve. CONCLUSION: Stentless xenografts have ideal haemodynamics, even in the small aortic root.

Animals↗
PubMed2000

Atrial right-to-left shunting causing severe hypoxaemia despite normal right-sided pressures. Report of 11 consecutive cases corrected by percutaneous closure.

BACKGROUND: Hypoxaemia resulting from a right-to-left shunt occurs in patients with atrial septal defects and high pulmonary vascular resistance, but it is uncommon without pulmonary hypertension. METHODS: We report on 11 consecutive patients (age: 59-78 years) in whom a patent foramen ovale or a small atrial septal defect with normal right-sided pressures led to significant cyanosis with clinical symptoms. Six of them had associated platypnoea and orthodeoxia. The diagnosis was confirmed by contrast transoesophageal echocardiography showing an atrial right-to-left shunt. RESULTS: All but one were successfully treated by percutaneous closure of the inter-atrial defect. In one patient, delivery of the occluder failed due to kinking of the introducing sheath. Four complications were observed following the procedure: two supraventricular arrhythmias and a cerebrovascular accident, all resolved without sequelae; one patient died from a septic shock unrelated to the procedure. During follow-up (up to 30 months), no patient experienced any episode of desaturation due to inter-atrial shunting. CONCLUSION: Cyanosis without pulmonary arterial hypertension in the adult should prompt the performance of contrast transoesophageal echocardiography to identify a possible atrial right-to-left shunt. Percutaneous closure of the defect allows efficient and rapid correction of the hypoxaemia and avoids the need for surgical closure.

Aged↗
PubMed2000

The Kex2p proregion is essential for the biosynthesis of an active enzyme and requires a C-terminal basic residue for its function.

The Saccharomyces cerevisiae prohormone-processing enzyme Kex2p is biosynthesized as an inactive precursor extended by its N-terminal proregion. Here we show that deletion of the proregion renders Kex2p inactive both in vivo and in vitro. Absence of the proregion impaired glycosylation and stability and resulted in the retention of the enzyme in the endoplasmic reticulum. These phenotypes were partially complemented by expression of the proregion in trans. Trans complementation was specific to Kex2p proregion because expression of any of the seven mammalian prohormone convertase propeptides had no effect. These data are consistent with a model whereby Kex2p proregion functions as an intramolecular chaperone and indicate that covalent linkage to the protein is not an absolute requirement for proregion function. Furthermore, extensive mutagenesis revealed that, in addition to their function as proteolytic recognition sites, C-terminal basic residues play an active role in proregion-dependent Kex2p activation.

Amino Acid Sequence↗
PubMed2000

Kinin B1 receptor expression and function on human brain endothelial cells.

The kinin B1 receptor is an inducible receptor expressed in response to inflammatory mediators. We sought to determine whether kinin B1 receptor can be expressed on human brain endothelial cells (HBECs) in vitro and whether signaling via this receptor can regulate permeability and chemokine production properties of these cells. Multiplex RT-PCR amplification and western blot techniques were used to evaluate B1 receptor expression by HBECs. Although B1 receptor mRNA and protein could not be detected on resting HBECs, interferon-gamma induced a dose- and time-dependent up-regulation of B1 receptor mRNA and protein on HBECs. Stimulation of interferon-gamma-treated HBECs with the selective B1 agonist R-838 (Sar [D-Phe8] des Arg9-BK) induced a dose- and time-dependent increase in the production of inositol 3,4,5 tri-phosphate and nitric oxide. Permeability of the HBECs monolayer, as measured by BSA diffusion, was significantly increased by application of the B1 agonist. This biological effect of R-838 could be prevented by R-715, a B1 receptor antagonist and by L-NAME, a nitric oxide synthase blocker. R-838 also inhibited interleukin-8 release from HBECs. We demonstrate that B1 receptors can be up regulated on the surface of HBECs by molecules released during inflammatory response and that signaling via this receptor can regulate BBB permeability and chemokine production in vitro.

Adult↗
PubMed2000

B7 expression and antigen presentation by human brain endothelial cells: requirement for proinflammatory cytokines.

Interaction between systemic immune cells with cells of the blood-brain barrier is a central step in development of CNS-directed immune responses. Endothelial cells are the first cells of the blood-brain barrier encountered by migrating lymphocytes. To investigate the antigen-presenting capacity of human adult brain endothelial cells (HBECs), we used HBECs derived from surgically resected temporal lobe tissue, cocultured with allogeneic peripheral blood derived CD4+ T lymphocytes. HBECs in response to IFN-gamma, but not under basal culture conditions, expressed HLA-DR, B7.1 and B7.2 antigens. Despite such up-regulation, these IFN-gamma-treated HBECs, in contrast to human microglia and PB monocytes, did not sustain allogeneic CD4+ cell proliferation, supported only low levels of IL-2 and IFN-gamma production, and did not stimulate IL-2 receptor expression. CD4+ T cell proliferation and increased IL-2 receptor expression could be obtained by addition of IL-2. Our data suggests that, although HBECs cannot alone support T cell proliferation and cytokine production, HBECs acting in concert with cytokines derived from a proinflammatory environment could support such a response.

Adult↗
PubMed2000

Heterogeneity of T-lymphocyte function in primary progressive multiple sclerosis: relation to magnetic resonance imaging lesion volume.

We found that in vitro migration and interferon-gamma production by lymphocytes derived from primary progressive multiple sclerosis patients preselected on the basis of a high T2-weighted lesion volume (>10 cm3) on magnetic resonance imaging, were increased compared with that in primary progressive multiple sclerosis patients with a low T2-weighted lesion volume (<3 cm3) and controls. Whether the heterogeneity of immune function within the primary progressive population will correlate with response to therapy remains to be established.

Adult↗
PubMed2000

Is 10 minutes the optimum immersion time in 0.6% glutaraldehyde for human pericardium?

BACKGROUND AND AIM OF THE STUDY: Pericardial fixation with 0.6% glutaraldehyde is usually assessed by measuring the shrinkage temperature of the tissue: the higher the shrinkage temperature, the greater the degree of cross-linking induced between collagen molecules. Animal pericardium studies have shown maximum response to be obtained after brief immersion (10 min). Our aim was to evaluate the effect of glutaraldehyde immersion time on shrinkage temperature of human pericardium which, to our knowledge, has not yet been studied. METHODS: Pericardial strips were harvested from 40 patients undergoing cardiac surgery. Time of immersion in glutaraldehyde ranged from 3 min to 6 months. Fresh untreated human pericardium samples were used as controls. The relationship between shrinkage temperature and time of treatment with glutaraldehyde was studied using a regression analysis. RESULTS: Glutaraldehyde treatment of pericardial tissues caused an increase in shrinkage temperature that was related biphasically to the time of immersion in glutaraldehyde. Mathematical expression of this curve permitted glutaraldehyde immersion time to be evaluated in relation to the degree of optimal shrinkage temperature. The time required for optimal fixation with glutaraldehyde, as measured by shrinkage temperature, was 100+/-0.77 min. CONCLUSION: Our results suggested that a 10-min exposure to glutaraldehyde was insufficient for 'correct' fixation of human pericardium. Inadequate glutaraldehyde exposure of human pericardium may explain mid and long-term failures reported with this tissue in cardiac surgery.

Bioprosthesis↗
PubMed1999

Bradykinin B1 receptor expression and function on T lymphocytes in active multiple sclerosis.

BACKGROUND: Lesion development in MS is initiated by migration of inflammatory cells into the central nervous system, a process dependent on endothelial cell-lymphocyte interaction. Bradykinin B1 receptor is a membrane-bound G protein-coupled receptor shown to be upregulated on the surface of various cells types during inflammation. OBJECTIVE: To assess the expression and function of the bradykinin B1 receptor on T lymphocytes from MS patients. METHODS: The authors used multiplex polymerase chain reaction amplification and Western blot techniques to demonstrate B1 receptor expression by T cells. A modified Boyden chamber assay also was used to assess the effect of B1 agonist and antagonist on T cell migration. RESULTS: The authors demonstrated that the expression of B1 receptor was upregulated on T cells derived from peripheral blood of MS patients. Expression of this receptor was upregulated on T cells from patients with secondary progressive MS and relapsing-remitting patients in active relapse. Expression was lower in relapsing remitting patients in remission and least in control subjects, including patients with epilepsy, chronic inflammatory demyelinating polyneuritis, and systemic lupus erythematosus. In vitro treatment of cells from healthy control subjects with tumor necrosis factor-alpha and interferon-gamma also induced the expression of B1 receptors. The authors also found that the significantly higher rate of migration of MS T lymphocytes, compared with control subjects in the Boyden chamber assay, could be prevented by the addition of the selective and stable B1 agonist Sar (D-Phe8) desArg9-BK. CONCLUSION: The authors demonstrate that B1 receptors are upregulated by T lymphocytes during the course of MS and that signaling through this receptor with a B1 agonist can negatively regulate T-cell migration in vitro.

Adult↗
PubMed1999

[Excess length of stay attributable to nosocomial bacteremia: usefulness of the Hospitalization Appropriateness Protocol].

BACKGROUND: To evaluate the usefulness of the Appropriateness Evaluation Protocol (AEP) for assessing the extra length of stay attributable to nosocomial bacteremia. PATIENTS AND METHODS: Retrospective review of the medical records (1989, 1990 and 1991) of all patients, who developed Staphylococcus aureus nosocomial bacteremia. Evaluation of hospital stay was performed using the AEP. Calculation of the kappa index and intraclass correlation coefficient. RESULTS: A total of 158 patients were included S. aureus nosocomial bacteremia is responsible for a mean excess length of stay of 4.3 days per patient. Kappa index for the method used was 76%, and intraclass correlation coefficient was 61%. CONCLUSIONS: The AEP has been shown to be a reliable tool for assessing the extra days of stay attributable to nosocomial bacteremia in the Spanish National Health System. The use of AEP should be extended to assess the extra stay attributable to other types of nosocomial infections.

Adult↗
PubMed1999

Lymphocyte migration and multiple sclerosis: relation with disease course and therapy.

Lymphocyte migration into the central nervous system is a central event in lesion formation in multiple sclerosis. By using a fibronectin-coated membrane Boyden chamber assay, we observed that migration rates of immediately ex vivo lymphocytes from patients with relapsing-remitting, with or without concurrent clinical relapse, or with secondary progressive disease, were increased compared with healthy donors. Migration rates of lymphocytes from relapsing-remitting multiple sclerosis patients receiving either glatiramer acetate (Copaxone 20 mg daily) or interferon-beta1b (Betaseron 8 MIU, three times per week) were significantly reduced compared with untreated relapsing-remitting patients. In vitro treatment with interferon-beta1b (1,000 U/ml), but not glatiramer acetate (20 microg/ml), significantly reduced lymphocyte-migration rates, suggesting that the effects of these two therapeutic agents on migration result from different mechanisms of actions. Interferon-beta1b acts, at least in part, by a direct effect on this cell property, whereas glatiramer acetate effects are indirect.

Adult↗
PubMed1999

Covered stents in the treatment of peripheral arterial aneurysms: procedural results and midterm follow-up.

PURPOSE: To evaluate initial and midterm results of percutaneous treatment of peripheral aneurysms using covered stents. METHODS: Between June 1994 and December 1997 we used covered stents (EndoPro System or Passager) on 19 patients with peripheral aneurysms (7 iliac, 5 subclavian, 3 femoral, 3 popliteal, 1 carotid). RESULTS: Successful aneurysm exclusion was achieved in 18 of 19 patients (95%). In the short term (<30 days), one patient died of puncture site hemorrhage complicated by myocardial infarction; two femoral stents were surgically removed because of leakage. At subsequent follow-up (mean 20 months) two further unrelated deaths occurred. At 1 year (intention-to-treat) the stent was patent in 13 of 19 patients (68%) and the aneurysm was excluded in 17 of 19 (89%). CONCLUSION: Treatment of peripheral aneurysms with covered stents has a high rate of immediate procedural success. Continued exclusion of the aneurysms is achieved in a large proportion of patients but there is a relatively high rate of stent thrombosis.

Adolescent↗