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Biomedical subjects

F Laurent

Publications and source records attributed to F Laurent.

At least 91 records · Page 5Linked to original sources
PubMed1999

Treatment of experimental pneumonia in rats caused by a PER-1 extended-spectrum beta-lactamase-producing strain of Pseudomonas aeruginosa.

The antibacterial activity of imipenem, cefepime and piperacillin-tazobactam alone or in combination with amikacin against a Pseudomonas aeruginosa strain producing an extended-spectrum beta-lactamase (PER-1) were compared using an experimental model of pneumonia in non-leucopenic rats. Animals were infected intratracheally with 8.0 +/- 0.4 log10 cfu of P. aeruginosa, and therapy was initiated 3 h later, by which time animal lungs showed bilateral pneumonia containing >7 log10 P. aeruginosa cfu/g of tissue. Since rats eliminate antibiotics much more rapidly than humans, renal impairment was induced in all animals to simulate the pharmacokinetic parameters of humans. MICs determined using an inoculum of 4 log10 cfu/mL were as follows: imipenem, 1 mg/L; cefepime, 8 mg/L; piperacillin-tazobactam, 32 mg/L; and amikacin, 16 mg/L. A noticeable inoculum effect was observed with the four antimicrobial agents tested, which was greatest for cefepime and piperacillin-tazobactam. In-vitro studies indicated that imipenem was the beta-lactam with the greatest bactericidal effect and that amikacin was synergic only in combination with cefepime and imipenem. Cefepime and piperacillin-tazobactam alone failed to decrease bacterial counts in the rats' lungs 60 h after therapy onset, whereas imipenem and, to a lesser extent, amikacin significantly reduced the number of viable microorganisms. Combination of amikacin with any of the three beta-lactams tested was synergic, despite a high amikacin MIC for the infecting strain. These results paralleled our in-vitro data showing a marked inoculum effect for cefepime and piperacillin-tazobactam. Based on the results of this study, the best treatment for infections caused by this type of extended-spectrum beta-lactamase-possessing strain would be imipenem plus amikacin.

Amikacin↗
PubMed1999

Segmented 5 versus nonsegmented flow quantitation: comparison of portal vein flow measurements.

RATIONALE AND OBJECTIVES: Times of acquisition, mean velocities, mean flows, and their respective standard deviations provided by segmented and nonsegmented flow quantifications (FQ) were compared in the main portal veins of ten healthy adults. METHODS: The segmented FQ performed five phase-encoding lines per segment. The authors successively applied the two electrocardiogram-triggered techniques in the same slice perpendicular to the portal flow direction. Their measurements were compared in particular by means of the statistical analysis proposed by Bland and Altman. RESULTS: The segmented 5 FQ reduced the acquisition time by two compared with the nonsegmented FQ. The mean velocity and mean flow values of the two techniques were not significantly different. The standard deviations were similar. CONCLUSIONS: The segmented 5 FQ showed its major advantage in the portal vein: the acquisition time was reduced without any loss of accuracy or any uncertainty enhancement.

Adult↗
PubMed1999

Biochemical-genetic analysis and distribution of FAR-1, a class A beta-lactamase from Nocardia farcinica.

From genomic DNA of the clinical isolate Nocardia farcinica VIC, a 1. 6-kb Sau3AI fragment was cloned and expressed in Escherichia coli JM109. The recombinant strain expressed a beta-lactamase (pI, 4.6), FAR-1, which conferred high levels of resistance to amoxicillin, piperacillin, ticarcillin, and cephalothin. The hydrolysis constants (kcat, Km, Ki, and 50% inhibitory concentration) confirmed the MIC results and showed that FAR-1 activity is inhibited by clavulanic acid and at a low level by tazobactam and sulbactam. Moreover, FAR-1 beta-lactamase hydrolyzes aztreonam (at a low level) without significant activity against ceftazidime, cefotaxime and imipenem. FAR-1 mature protein of molecular mass ca 32 kDa, has less than 60% amino acid identity with any other class A beta-lactamases, being most closely related to PEN-A from Burkholderia cepacia (52%). A blaFAR-1-like gene was found in all studied N. farcinica strains, underlining the constitutive origin of this gene.

Amino Acid Sequence↗
PubMed1999

Distribution of lung density after strenuous, prolonged exercise.

The postexercise alteration in pulmonary gas exchange in high-aerobically trained subjects depends on both the intensity and the duration of exercise (G. Manier, J. Moinard, and H. Stoïcheff. J. Appl. Physiol. 75: 2580-2585, 1993; G. Manier, J. Moinard, P. Techoueyres, N. Varène, and H. Guénard. Respir. Physiol. 83: 143-154, 1991). In a recent study that used lung computerized tomography (CT), evidence was found for accumulation of water within the lungs after exercise (C. Caillaud, O. Serre-Cousine, F. Anselme, X. Capdevilla, and C. Prefaut. J. Appl. Physiol. 79: 1226-1232, 1995). On representative slices of the lungs, mean lung density increased by 0.040 +/- 0.007 g/cm(3) (19%, P < 0.001) in athletes after a triathlon. To verify and quantify the mechanism, we determined the change in pulmonary density and mass after strenuous and prolonged exercise using another exercise protocol and methodology for CT scanning. Nine trained runners (age 30-46 yr) volunteered to participate in the study. Each subject ran for 2 h on a treadmill at a rate corresponding to 75% of maximum O(2) consumption. CT measurements were made before and immediately after the exercise test with the subject supine and holding his breath at a point close to functional residual capacity. The lungs were scanned from the apex to the diaphragm and reconstructed in 8-mm-thick slices. Attenuation values of X-rays in each part of the lung were expressed in Hounsfield units (HU), which are related to density (D): D = 1 + HU/1,000. No significant alteration in pulmonary density (0.37 +/- 0.04 vs. 0.35 +/- 0.03, not significant) was observed after the 2-h run test. Although lung volume slightly increased (change of 166 +/- 205 ml, P < 0.05), lung mass remained stable because of a change in density distribution. We failed to detect any changes in postexercise lung mass, suggesting that other mechanisms need to be considered to explain the observed alterations in pulmonary gas exchange after prolonged strenuous exercise.

Adult↗
PubMed1999

Surgical treatment of an endovascular metastatic melanoma of the superior vena cava.

A 42-year-old woman, who had undergone excision of a melanoma of her right forearm 3 years before (Breslow's index 4.4 mm), was admitted to hospital for the evaluation of an superior vena cava syndrome. The thoracic CT scan and the phlebography showed obstruction of the superior vena cava by an endovascular tumor. Abdominal, pelvis and cranial CT scans did not reveal any other metastatic localization. Surgery with extracorporeal circulation was performed. The mass was resected and histopathologic examination confirmed the endovascular metastatic melanoma. There was no heart metastasis. The patient was then given a polychemotherapy. She was still alive after 18 months of follow-up after the initial metastasis. To our knowledge, no similar case has previously been reported and surgical treatment, as for isolated heart metastatic melanoma, may be considered for vascular metastasis, as in our case.

Adult↗
PubMed1999

Assessment of bronchial inflammation using an automated cell recognition system based on colour analysis.

The aim of this study was to develop an automated system of cell recognition based upon colour analysis suitable for microscopic examination of bronchial inflammation. Human bronchi obtained from 17 patients undergoing thoracotomy were embedded in glycolmethacrylate to perform immunohistochemistry with antibodies against: neutrophil elastase, tryptase, chymase, eosinophil cationic protein, CD68, CD3 and immunoglobulin E. The image analysis system calculates three independent criteria (optic density, hue density, hue) combined with morphological parameters to specifically recognize a positive staining. This automated analysis was applied to the study of bronchial inflammation in smokers and nonsmokers in terms of the absolute number of cells and the expression of different markers by a single cell. The use of these criteria enabled the characterization of a positive stain on single (intraclass correlation coefficient (ICC) = 0.88 or serial (ICC = 0.84) sections. Cell counts obtained by the automated system were highly reproducible. Regarding bronchial inflammation, it was found that the number of inflammatory cells was significantly higher in smokers than in nonsmokers, the majority of these cells bearing immunoglobulin E. These results demonstrate that such computerized analysis of colours is a valuable method for quantifying inflammatory cells in bronchial tissue and for analysing the expression of different markers by a single cell.

Aged↗
PubMed1999

Usefulness of somatostatin receptor scintigraphy in patients with occult ectopic adrenocorticotropin syndrome.

SRIF receptor scintigraphy (SRS) has been proposed for the localization of ectopic ACTH-secreting tumors responsible for Cushing's syndrome. However, in most cases reported, the tumors were also visible using conventional imaging. Therefore, the usefulness of SRS in localizing truly occult ectopic ACTH-secreting tumors remains unknown. We report the results of SRS in 12 patients with ectopic ACTH syndrome (EAS) and in whom the source of ACTH was occult at presentation despite carefully performed conventional imaging. The diagnosis of EAS was made by identification of an ACTH-secreting tumor during follow-up in 5 patients or given a pituitary-to-peripheral ACTH ratio of 1.9 or less during petrosal sinus sampling combined with CRH injection and a negative pituitary magnetic resonance imaging (MRI). Whole-body planar SRS, using (111)In-pentetreotide, was performed 19 times in the 12 patients during initial workup and/or follow-up. Axial tomography imaging (single-photon emission-computed tomography) was performed in 7 of these. Conventional imaging was performed within a month of SRS, allowing comparison of the two approaches for the localization of the ACTH-secreting tumors. In addition, the response of plasma cortisol, after a single injection of 200 microg octreotide, was studied in 6 patients. Five patients had negative SRS and conventional imaging studies. The source of ACTH secretion remains occult despite 10-55 months of follow-up in four of these, whereas a 2-cm ileal carcinoid tumor, with liver micrometastases, was found at laparotomy in one patient, 14 months after presentation. SRS was positive in 4 of 12 patients. It was false-positive in 1 patient with follicular thyroid adenoma. Nineteen months after presentation, SRS identified liver metastasis that was also visible using MRI in one patient, but the primary tumor remains occult. SRS identified a 10-mm pancreatic tumor that became detectable, using computed tomography (CT) scanning 9 months later, in 1 patient; and 2 mediastinal lymph nodes of 10 mm, previously ignored by MRI, in another patient, whereas no tumor was detectable within the parenchymal lung. SRS had little influence on therapeutic options in these 2 patients, in whom no final diagnosis could be made. Repetition of SRS during the follow-up of patients with previously negative scintiscans was useless. Conventional imaging was positive in 6 of 12 patients. In the 2 patients with pancreatic tumor and isolated mediastinal lymph nodes, conventional imaging studies were interpreted as positive only after the results of SRS. One patient had liver metastasis that was also visible using SRS. Thin-section CT scanning visualized ACTH-secreting bronchial tumors and metastatic mediastinal lymph nodes of 10-15 mm in diameter in 3 patients after 14-72 months of follow-up, whereas SRS was negative. There was no evident relationship between the endocrine status (hyper- or eucortisolism) and the results of SRS. The in vivo response of plasma cortisol to octreotide correlated to the results of SRS in 4 of 6 cases. In conclusion, both imaging procedures had a low diagnostic yield in this series. However, the sensitivity of SRS for the detection of bronchial carcinoids was lower than that of thin-section CT scanning. We therefore advocate the use of conventional imaging, including thin-section CT scanning of the chest, analyzed by experienced radiologists, as the first-line investigation in patients with occult EAS. SRS should not be repeated during the follow-up in patients with a previously negative scintigram.

ACTH Syndrome, Ectopic↗
PubMed1999

Pneumothoraces and chest tube placement after CT-guided transthoracic lung biopsy using a coaxial technique: incidence and risk factors.

OBJECTIVE: This study investigates factors influencing the risk of pneumothorax and chest tube placement in patients undergoing CT-guided transthoracic lung biopsy for pulmonary lesions using a coaxial technique. SUBJECTS AND METHODS: The study included 307 patients with pulmonary lesions biopsied under CT guidance. Patient-related parameters considered were age, sex, presence of emphysema or bullae, and lung function data. Lesion-related variables were size, location, cavitary appearance on CT, pleural contact, and depth of the lesion. Procedure variables were duration, type of needle, and experience of the operator. All variables were analyzed as single and multiple dependent variables for occurrence of pneumothorax. RESULTS: Pneumothorax occurred in 61 (19.9%) of the 307 patients, and chest tube placement was required in six patients (2.0%). Univariate analysis showed that lesion size, lesion location, lesion depth, and difficulty of the procedure were significantly associated with a higher rate of pneumothorax. Using multivariate logistic regression analysis, we found that lesion depth from the pleural entry point was the sole variable that was significantly associated with an increased risk of pneumothorax. This risk increased with the depth of the lesion. Chest tube placement was required more frequently in patients with severe emphysema, obstructive lung disease, or hyperinflation. CONCLUSION: Lesion depth is the predominant risk factor for pneumothorax in patients undergoing CT-guided transthoracic lung biopsy. Chest tube placement is necessary more frequently in patients with severe emphysema, obstructive lung disease, or hyperinflation.

Adult↗
PubMed1999

[Utilization of Bichrolatex albicans test for the rapid identification of Candida albicans in blood culture bottles in fungemia: preliminary results from a multicenter study].

In patients with fungemia, reliable and rapid identification of the causative organism has a large impact on treatment decisions. The Bichrolatex albicans test (Fumouze, Levallois-Perret, France) allows rapid identification of Candida albicans in colonies. Its usefulness for identifying C. albicans in liquid blood culture media was evaluated using a previously published protocol. Ninety-seven blood culture bottles from 86 fungemia episodes in 13 study centers were studied. C. albicans contributed 52% of the fungemia episodes, whereas C. glabata and C. tropicalis contributed 15% and 11.5%, respectively. The 48 bottles containing a yeast other than C. albicans were all negative by the Bichrolatex albicans test. Of the remaining 48 bottles, which were positive for C. albicans, 33 produced marked to moderate agglutination and 15 were negative. In one case of mixed fungemia (C. albicans plus C. glabata), weak agglutination was seen. Sensitivity of the test was 69%, negative predictive value was 76%, specificity was 100%, and positive predictive value was 100%. Because of its limited sensitivity, the Bichrolatex albicans test cannot be recommended as a confirmation test for C. albicans fungemia. In contrast, the specificity and positive predictive value of the test are excellent.

Blood↗
PubMed1999

[Transthoracic aspiration. Evaluation of cytologic and histologic diagnosis in a pulmonary nodule by retrospective comparison of 2 series of 267 cytoaspirations and 292 coaxial needle aspirations].

Percutaneous fine-needle aspiration is a well established method for the diagnosis of peripheral lung lesion. In order to compare different methods of aspiration, we analyze retrospectively two different series: 267 fine needle aspirations (FNA) compared with the histological diagnosis on surgical specimens and 292 lung biopsies using a coaxial technique with comparison between cytological diagnosis--smears and imprints--and histological diagnosis simultaneously obtained on the same specimen. The sensitivity (91%), the specificity (90%) and the overall typing accuracy related to the histological types obtained by FNAB are equivalent to those of the literature. The low rate of pneumothorax in the series (6%) is related to the use of immediate interpretation of the specimen. Automated biopsy with a coaxial cutting needle provide cytological specimens--smears and imprint--with a high rate of sensibility (95.3%) and of sensibility (98%). The overall sensitivity of the cytological methods alone is better than biopsy (95.3% vs. 92.9%), but the typing accuracy is not as good as biopsy alone (98% vs. 100%). False-positive and false-negative diagnoses are the same in both series. In conclusion the percutaneous aspiration method choose to establish a morphological diagnosis in lung lesion depends now on the habits of the radiologist and the pathologist.

Biopsy, Needle↗
PubMed1999

[Exposure to asbestos. Role of thoracic imagery in screening and follow-up].

Chest radiograph and computed tomography are the most appropriate imaging tools for detecting asbestos-related pleural and parenchymal disease due to their availability and performances. The cost and irradiation delivery of conventional chest X-rays are limited. Technical parameters and reading should be standardized. Digital chest radiograph will progressively replace conventional techniques but technical standards and performance data are lacking. Computed tomography, using spiral or conventional mode, explores the whole lung and pleura. High resolution computed tomography samples both lung and pleura but its sensitivity for parenchymal fibrosis detection is greater. Several methods can be employed and should be recommended to reduce radiation dose in spiral and high resolution computed tomography. Computed tomography is more sensitive and specific than chest radiograph in early detection of pleural plaques and parenchymal fibrosis but is not infallible. The error reading rate of chest radiograph for early detection of bronchial carcinoma is high. Computed tomography is more sensitive but lacks specificity and leads to detect a high rate of lesions the relation to asbestos exposure of which are difficult to establish. No scientific data are available to assess the contribution of imaging in early detection of mesothelioma.

Asbestosis↗
PubMed1998

Localized fibrous tumor of the liver: imaging findings.

We report the imaging of a localized fibrous tumor of the liver, focusing on color Doppler US, CT, MR imaging, and angiographic findings. We discuss the differential diagnosis of such a rare, benign lesion of the liver. Detailed imaging of this tumor has not been reported in the literature previously.

Aged↗
PubMed1998

Mediastinal masses: diagnostic approach.

In most clinical situations the modern radiological approach to a mediastinal mass consists of performing a CT scan following the chest radiograph. Magnetic resonance imaging is indicated when CT findings are equivocal and as the first-line method in particular situations such as suspected involvement of the posterior mediastinum. In both techniques, tissular components of the mass assessed by density or signal intensity analysis, together with the precise location, are the leading edge of the radiological diagnosis. This review deals mainly with the differential diagnosis of primary neoplasms according to CT and MRI findings.

Diagnosis, Differential↗
PubMed1998

Proteic composition of corpora amylacea in the bovine mammary gland.

Histochemical studies of mammary gland sections obtained from healthy lactating Prim' Holstein cows contained numerous corpora amylacea, mainly located in active alveoli. Observations by electron microscopy revealed a cauliflower shape, with a fibrillar or multilayered organization. Mineral studies confirmed the presence of high calcium levels (12.3% of dry matter) and phosphorus (7.4%) in the corpora amylacea composition. These bodies stained positive to Von Kossa silver nitrate and to Periodic acid-Schiff. However, depending on the gland of origin, corpora amylacea stained positive or negative to Congo red. Histochemical studies seemed, therefore, insufficient to determine the presence or absence of amyloid. The amount of total protein varied by approximately 25%. Immunoblotting and analysis of the amino acid sequence of a peptidic fragment obtained from corpora amylacea gave clear evidence of the occurrence of caseins, beta-lactoglobulin and alpha-lactalbumin. However, the comparison between the amino acid composition of corpora amylacea and those of the main milk proteins indicated the presence of other proteins. Electrophoretic analysis also gave evidence of the presence of several other proteins, i.e. glycoproteins. Therefore, it is probable that corpora amylacea composition is much more complex than previously reported.

Animals↗
PubMed1998

A validation of a flow quantification by MR phase mapping software.

AIM: We evaluated a Siemens software of flow quantification (FQ) by MR phase mapping, in the framework of a common practical use. METHODS: Experiments with a laminar flow phantom and in vivo pulsatile flow were performed. In particular, FQ in ascending aorta was investigated in healthy volunteers. RESULTS AND CONCLUSION: Flow phantom experiments reveal that the FQ slightly underestimates (8% on the average) actual velocities (mean velocities over a vessel area), and also that velocity uncertainties are related to the encoding velocity value, whatever the measured velocity. Furthermore, using well characterized working criteria, we found low intraobserver variability and negligible interobserver variability in ascending aorta FQs. The role played by the choice of reference area in FQ accuracy is emphasized. When recording several cardiac cycles during the same acquisition, it is shown that the FQ software may provide erroneous results. Several comments for FQ software use in the ascending aorta are added.

Adult↗