Biomedical subjects

F Laurent

Publications and source records attributed to F Laurent.

At least 163 records · Page 9Linked to original sources

PubMed1992

[Non-invasive imaging in aortic dissection].

Previously with a drastic prognosis, aortic dissection has extensively benefitted from advances in medical and surgical treatment, as well as progress in methods of investigation. While aortography is classically the reference special investigation, non-invasive methods now have a place of choice both during the acute phase (transthoracic and transesophageal echocardiography) and the chronic phase or for the purpose of post-operative monitoring (CT scan, magnetic resonance imaging). In an emergency context, the most important point is to diagnose a type A dissection, involving the ascending aorta, the treatment of which is surgical. In the majority of cases the diagnosis can now be made on the basis of transthoracic and transesophageal echocardiographic findings, which also enable identification of the site of the portal of entry, extension and concomitant lesions, all important features to be taken into consideration regarding surgical tactics.

Aortic Dissection↗

PubMed1992

[Biological and developmental aspects of macronodular adrenal hyperplasia in Cushing's disease].

The pathophysiology of macronodular adrenocortical hyperplasia (MNH) associated with Cushing's diseases remains debatable. Some authors have claimed that MNH represents an autonomous condition that has to be treated by surgical adrenalectomy while others advocate the use of pituitary surgery. We have compared the biochemical features, before and after pituitary surgery, between 7 cases of MHN and 22 cases of diffuse hyperplasia (DH) associated with Cushing's disease. In addition, the diameter of the adrenal nodules after surgery was evaluated in 6 cases. The mean ACTH level in MNH and DH subjects was similar. Dexamethasone suppressibility and the stimulatory effect of metyrapone on ACTH secretion were less in MNH than in DH subjects, suggesting a greater degree of adrenal autonomy in the former. The cortisol responses to metyrapone and CRF tests suggested an increased responsiveness of the adrenals to endogenous ACTH in the MNH group. Only one MNH patient had biochemical features suggesting a primary adrenal disease. The use of a sensitive ACTH assay and the results of inferior petrosal sinus sampling identified the ACTH-dependency of the disease. A short to medium term remission of the disease was obtained in all cases of MNH and in 87% of cases of DH after surgery. The diameter of the adrenal nodules significantly decreased in only 43% of cases. Our results suggest that the adrenal autonomy in MNH is incomplete and that, despite the persistence of the adrenocortical nodules, the disease can be cured with pituitary microsurgery in most cases.

Adrenal Glands↗

PubMed1992

[How can intrathoracic lymphatic involvement be assessed: does tomography have a role? What is the contribution of computed tomography and MRI?].

The authors report their analysis of the literature on the evaluation of intrathoracic extension of non-small-cell bronchial cancers to lymph nodes, using tomography, computed tomography and magnetic resonance imaging. The criteria used to assess the metastatic character of a lymph node, the characteristics of the populations studied and the methods of comparison with the clinicopathological "truth" account for the variations of the results published. Tomographs are useless today. The performances of CT and MRI are equivalent, and it is not necessary to associate both techniques. Although its performances are mediocre, CT allows mapping the mediastinal lymph nodes, which is useful to continue the assessment of extension and to make decisions.

Carcinoma, Non-Small-Cell Lung↗

PubMed1992

Selective detection of human hepatitis B virus surface and core antigens in some peripheral blood mononuclear cell subsets by flow cytometry.

The presence of HBs and HBc antigens was investigated, by flow cytometry, on the surface of peripheral mononuclear cells (PBMC) from the following phenotype: CD3 (T lymphocytes), CD4 (T helper/inducer), CD8 (T cytotoxic/suppressor), CD19 (B lymphocytes) and CD56 (NK cells) among 8 patients suffering from chronic hepatitis B and 5 healthy HBV-negative subjects. This study demonstrated the presence of HBsAg and HBcAg on the lymphocyte surface for most of the patients. The mean percentage of labelled cells was 17% for HBsAg and 15% for HBcAg. Among the different lymphocyte subsets only B lymphocytes and the NK cells expressed HBsAg for 57% and 26% of cells, respectively. Similarly HBcAg was also detected among CD19 and CD56 cells only. PCR was used to search for the presence of HBV DNA and RNA in PBMC, using primers located in the S gene. HBV DNA was detected with variable intensity in the CD3, CD4, CD19 and CD56 subsets following their separation with a cell sorter. For HBV RNA the signal obtained after PCR and Southern blotting was higher for CD56 and CD19 cells than for CD3 cells and undetectable for CD4 cells. This study demonstrates that replication and transcription can occur in CD19 and CD56 cells. Positive signals in CD3 cells may possibly be due to contamination of this subpopulation by NK cells.

Antigens, CD↗

PubMed1991

Oxidative metabolism of polymorphonuclear leukocytes: modulation by adhesive stimuli.

Different agents such as phorbol myristate acetate (PMA), N-formyl-methionyl-leucylphenylalanine (fMet-Leu-Phe), or opsonized zymosan induced an oxidative burst in rat peritoneal polymorphonuclear leukocytes (PMNs) elicited by casein. Plastic adhesion of PMNs down-regulated superoxide (O2) release stimulated by PMA or fMet-Leu-Phe but had no effect on zymosan-induced O2 generation, indicating that the O2 forming enzyme, the NADPH oxidase, was not affected by modulation and that a common step of the transductional events induced by PMA or fMet-Leu-Phe might be involved in this regulation. We demonstrated that a differential translocation of protein kinase C (PKC) was not responsible for that modulation. PMA-induced secretion of granule content (vitamin B12-binding protein) was not susceptible to modulation, suggesting that the transductional pathways leading to O2 generation and granule secretion are partly separated. The adhesion of PMNs to different substrates (glass, plastic, albumin-, laminin-, fibronectin-, poly-lysine-, or concanavalin A-coated plastic) down-regulated to different extent superoxide release. Whether the nature of the biochemical signal induced by the diverse adhesive stimuli or a physical parameter such as binding strength was involved in this differential behavior remains to be elucidated. Since adhesiveness was dependent on the state of the cytoskeleton and O2 inducers were reported to stimulate actin polymerization, we studied the F-actin content and distribution of PMNs by using the specific fluorescent probe NBD-phallacidin and an original methodology allowing a quantitative analysis of fluorescence on both adherent and suspended cells. PMA induced a polarization of F-actin on suspended PMNs but had no effect on the intracellular distribution of F-actin in adherent PMNs. Thus, we suggest that the adhesion of PMNs induced an immobilization of F-actin, possibly correlated to the down-regulation of one of the transductional pathways involved in the NADPH oxidase activation.

Actins↗

PubMed1991

Diagnosis and categorization of small bowel neoplasms: role of computed tomography.

A retrospective study of 35 patients with small bowel neoplasms studied by computed tomography (CT) was performed. The tumor detection rate was 80%. Using the findings reported in the literature, an adequate histological diagnosis could be performed in 69% of the cases by CT. Lipomas, leiomyomas, leiomyosarcomas, and carcinoid tumors were well-recognized, but adenocarcinomas and lymphomas were often mistaken one for the other. An accurate preoperative staging was performed in 61% of the cases. CT failed to detect 75% of the invaded lymph nodes, 25% of the liver metastases, and 25% of the tumoral growth beyond the bowel wall. Despite major limitations in preoperative staging, a good detection rate and some features allowing a specific diagnosis advocate using CT along with the barium examination when clinical history suggests a small bowel tumor.

Adenocarcinoma↗

PubMed1990

[Myocardial mass index in the diagnosis of acute rejection of allogeneic heart transplants].

Changes in an index of left ventricular mass were evaluated in the diagnosis of acute cardiac transplant rejection in a prospective study involving 28 transplant patients by comparison with the histology of endomyocardial biopsy. The surface of a ring of left ventricular myocardium obtained from a 2D echocardiographic examination was used as an index of mass. Eighty-three pairs of results--biopsy and index of mass--recorded within a 12 hour interval were obtained between the first day and 10th month of transplantation over a period of 12 consecutive months. Echocardiographic diagnosis of acute rejection was made when the index of myocardial mass increased by over 7 per cent compared with baseline values recorded during the first 3 days of transplantation or during a new period of equilibrium after an episode of rejection. Two groups of patients were identified from the results of biopsy, taken as the reference: in 16 patients with mild or moderate histological signs of rejection the variation of the index of mass was 18.3 +/- 9.1%; endomyocardial biopsy was negative in the 12 other patients and the change in index of mass was -1.5 +/- 5.2% (p less than 0.001). The overall concordance in the 83 successive results was good with a Kappa coefficient of 0.71. The other parameters which have been reported to be useful in diagnosing rejection (relaxation, antegrade diastolic mitral flow, acoustic density of myocardium) present a number of problems in routine practice related either to difficulties with the recording of the data or to its interpretation.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗

PubMed1990

[Imaging of malignant lymphoma of muscular sites].

Seventeen cases of muscular lymphoma are reported (5 primary non-Hodgkin lymphoma, 11 secondary NHL, 1 secondary Hodgkin's disease). The psoas or gluteus muscle was involved in 10 cases, and the lower limb was affected in the remaining 7 cases. Nine cases of muscular extension of bone NHL are also reported. On sonograms these lesions were always large and less echogenic than adjacent structures, with no signs of necrosis before treatment. US and CT patterns were comparable for both primary and secondary lesions, regardless of the type of lymphoma or whether or not there was any previous bone lesion. Associated lymphomatous lesions were observed in 14 cases. On angiograms, muscular lymphomatous involvement presented a hypovascular pattern. While ultrasonography is an excellent monitoring technique for soft tissue lymphomas (specially for the lower limbs), a major contribution of CT is the detection and the follow-up of deep or thoracic wall lesions.

Adolescent↗

PubMed1990

[Tomodensitometric aspects of brain lymphomas: apropos of 19 cases. Brain lymphoma].

The authors present the results of CT studies for 19 patients with cerebral lymphoma (including 12 primary tumors). CT appearances varied considerably, because 5 of the 12 primary lymphomas presented as multifocal lesions, and lesion sites included the corpus callosum (3 cases), the central caudate nucleus (4 cases), the posterior fossa (3 cases), and the cerebral hemispheres (6 cases). These findings are in agreement with literature data. Although a solitary, hyperdense and homogeneous lesion in the corpus callosum or the central caudate nucleus is indicative of cerebral lymphoma, numerous other aspects are possible and owing to the increasing frequency of this pathology should suggest this diagnosis. There is no specific appearance for secondary lymphomas, but diagnosis is often facilitated by concomitant systemic involvement.

Adult↗

PubMed1990

[Contribution of x-ray computed tomography and MRI to the surgical diagnosis of bronchial cancers. Comparative evaluation of x-ray computed tomography, MRI and thoracotomy in 111 cases].

Computed tomography and magnetic resonance imaging have respectively decreased the incidence of exploratory thoracotomy by 11.6% to 5.7% then 5.3% after their successive inclusion in the assessment of the operability of lung cancers. Based on a systematic comparison of CT and MRI with exploratory thoracotomy in 111 patients, the yield, sensitivity and positive predictive value of these examinations was assessed in relation to tumour extension to various sites: to the chest wall, for which the sensitivity was poor (38% for CT, 54% for MRI) with a moderate predictive value (71% for CT, 77% for MRI); to the mediastinum with improved sensitivity (69% and 72%) but an uncertain predictive value (61% and 72%). The sensitivity and predictive value were then measured for lymph node involvement: N1: moderate sensitivity (69% and 76%) but a good predictive value (95% and 92%); N2 and N3: good sensitivity (79% and 93%) but a poor predictive value (70% and 66%). Apart from a few particular indications specific to MRI, especially in the apex, left hilum and in contact with the atrium, the efficacy of these two investigations is very similar. However, their lack of specificity means that certain exploratory thoracotomies are still justified in order to assess the operability of the tumour. A surgical or mediastinoscopic anatomical assessment is still necessary for a good classification of lymph node extension of lung tumours.

Carcinoma, Bronchogenic↗

PubMed1989

Distribution and morphometric characteristics of oxytocin- and vasopressin-immunoreactive neurons in the rabbit hypothalamus.

The distribution, morphological features, and morphometric characteristics of cell bodies producing oxytocin (OT) and vasopressin (AVP) were studied in the rabbit hypothalamus by means of a conventional immunoperoxidase method. The aim of the present study was to determine the existence or not of a species-specific OT-cell group that might be involved in the dense OT innervation of the intermediate lobe in the leporidae. No OT-cell group clearly distinct from the hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei was found, even in colchicine-treated animals. Most immunoreactive perikarya were found within these nuclei. In addition, small AVP neurons occurred in the suprachiasmatic nucleus. In the SON, the predominant, tightly packed AVP cells occupied the ventral part of the nucleus, whereas OT neurons were dorsolaterally located. The PVN presented a loose organization without any obvious subdivision. OT cells, which predominated, occupied the medial part of the nucleus. The PVN had a prominent rostral anterobasal extension composed mainly of OT cells. Laterally to the nucleus, numerous large AVP neurons, with few and smaller OT cells, dispersed along the neurosecretory tract without forming definite cell clusters. AVP cell bodies had a rough granular aspect contrasting with the smooth and fine one of OT cells. Spinelike processes were rarely observed on the perikarya, except on large scattered AVP neurons, but frequently covered the proximal dendrites of both types of neurons. Throughout the hypothalamus, OT neurons had definitely smaller mean somal areas and were more homogeneous in size than AVP cells.

Animals↗

PubMed1989

Growth hormone and somatostatin in the plasma of transiently diabetic ducks: basal variation and response to glucose.

In the duck, subtotal pancreatectomy induces a transient diabetes, with decreased insulin and glucagon basal levels as well as responses to glucose. At the same time, a transient increase in basal peripheral somatostatin occurs, followed by an increase in growth hormone in the postdiabetic state. Intravenous glucose induces a slight decrease in somatostatin secretion in normal, but not in diabetic animals, and no significant variation in growth hormone secretion at any state. An obvious role of growth hormone or somatostatin in the development of this transient diabetes in the duck could not be detected in this study.

Animals↗

PubMed1989

Pharmacokinetics of Ro 03-8799 in mice bearing melanosarcoma: comparison with tumors without melanin.

The pharmacokinetics of Ro 03-8799 has been studied in melanic and non-melanic tumor bearing mice after iv administration of 150 mg/kg. The peak concentration in B16 melanosarcoma tumor reached 152 micrograms/g, that is 7.6-fold higher than the plasma concentration at the same time. This concentration is 3-times greater than that obtained in the tumor of mice bearing non melanic sarcoma (DB16) or Lewis lung carcinoma (3LL). The exposure of B16 tumor (AUC) is respectively 15-times and 11-times higher than the 3LL and the DB16 ones. These experimental data confirm that this 2-nitro-imidazol compound has an important affinity for melanin and suggest that it might be used as a radiosensitizer for the treatment of malignant melanoma.

Animals↗

PubMed1989

Combined heart and kidney transplantation using the same donor.

A 45-year-old man received a combined heart and kidney transplant provided by the same donor. The patient was in the terminal stage of renal failure and was submitted to 3 sessions of haemodialysis per week for 2 years before transplantation. A dilated cardiomyopathy with severe impairment of left ventricular (LV) function was discovered, precluding renal transplantation alone. In the postoperative course, a cardiac rejection episode was detected by echocardiography and documented by endomyocardial biopsy; no simultaneous rejection of the kidney could be detected. The patient was discharged after 2 months, and he resumed a normal and active life. The specific problems raised by the management of such multi-organ transplantation are briefly reviewed.

Cardiomyopathy, Dilated↗

PubMed1989

[Delayed duodenal perforation caused by transhepatic biliary endoprosthesis].

Three cases of duodenal perforation which occurred after the placement of a biliary endoprosthesis, are reported. One intraperitoneal perforation required an immediate surgical intervention. The two other cases have been treated endoscopically and by transhepatic drainage, respectively. The mechanism of this delayed complication is discussed and the impact caused by the shape of the Carey-Coons endoprosthesis (Porges-Roche) analysed.

Aged↗

PubMed1988

Autoradiographic distribution of [14C]-labelled pimonidazole in rhabdomyosarcoma-bearing rats and pigmented mice.

The hypoxic cell radiosensitizer [2-14C] pimonidazole (2-nitro-alpha-(piperidinomethyl)-l-imidazole ethanol) was injected i.p. into pigmented mice and rats bearing transplanted rhabdomyosarcoma. The injected dose level was 200 mg/kg, and the delivered activity was 96 microCi/kg. Whole-body autoradiography was carried out on all animals. We noted an extensive whole-body distribution of radioactivity. At short intervals, the autoradiograms were characterized by an accumulation of radioactivity in the metabolic and excretory organs (liver, kidney, urinary tract, and intestinal content) as well as in lymphomyeloid tissues (thyroid gland, suprarenal gland, and hypophysis) and salivary glands. In pigmented mice, the uveal and biliary tracts were the highest labelled. The liver and particularly the renal medulla were identified as sites of retention of radioactivity. In the tumor the radioactivity was detected only in peripheral regions, with higher uptake in viable zones than in necrotic islets.

Animals↗

PubMed1988

Extraretroperitoneal abdominal malignant fibrous histiocytoma.

Seven cases of extraretroperitoneal abdominal malignant fibrous histiocytoma (MFH) are reported. The anatomic distribution was as follows: liver (2 cases), spleen with gastric and pancreatic involvement (1 case), mesentery (1 case), right mesocolon (1 case), left mesocolon (1 case), and urachus (1 case). These bulky lesions were often extensively necrotic; calcifications were seen in 2 cases. All 7 cases were investigated by ultrasonography (US) and computed tomography (CT). Barium studies were performed in 4 cases, and angiography in 3 cases.

Abdominal Neoplasms↗

PubMed1988

Bronchogenic carcinoma staging: CT versus MR imaging. Assessment with surgery.

One hundred and twenty patients with bronchogenic carcinoma were prospectively studied by both computed tomography (CT) and magnetic resonance imaging (MRI) during the 2 weeks preceding thoracotomy or mediastinoscopy. MRI scans included contiguous axial and coronal slices. Results of CT and MRI studies were compared with the surgical and pathological findings on the basis of the TNM classification. Although no significant difference was found between the two imaging methods for the evaluation of tumour extent, MRI appears to be a valuable imaging technique for left upper lobe and apical neoplasms. Comparison between the two techniques for mediastinal node evaluation showed that sensitivity of MRI is superior to CT in the left paratracheal, aortopulmonary and subcarinal node areas.

Adult↗