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Biomedical subjects

F Laurent

Publications and source records attributed to F Laurent.

At least 109 records · Page 6Linked to original sources
PubMed1998

Comparative evaluation of conventional and dynamic magnetic resonance imaging of the pituitary gland for the diagnosis of Cushing's disease.

OBJECTIVES: The ability of MRI to detect pituitary ACTH-secreting adenomas in patients with Cushing's disease is limited. Owing to different dynamics of contrast enhancement between adenomas and normal pituitary tissue, it has been suggested that obtaining images within seconds after gadolinium (Gad) injection using dynamic procedures increases the sensitivity of MRI in the detection of pituitary microadenomas. The objective of this study was to compare the ability of conventional magnetic resonance imaging (CMRI) and dynamic MRI (DMRI) to detect ACTH-secreting pituitary adenomas. DESIGN: Twenty-six consecutive patients with ACTH-dependent Cushing's syndrome and 10 normal subjects were investigated. According to the results of inferior petrosal sinus sampling, 21 patients had Cushing's disease and five had ectopic ACTH syndrome. Patients with Cushing's disease were operated regardless of the results of imaging studies. All underwent identical MRI and DMRI procedures using a 1.0 T magnet. Image sampling time during DMRI was 19 sec. Scans were randomly mixed and analysed blind, retrospectively and independently by two experienced radiologists. The clarity of the images was assessed by the analysis of agreement among radiologists. MRI findings were compared to surgical and histopathological findings. RESULTS: Surgical exploration identified three macrodenomas and 14 microadenomas. One microadenoma was found at pathological examination after subtotal hypophysectomy and no tumour was found in three cases. According to the combined opinion of radiologists, the three macroadenomas were identified equally well with CMRI and DMRI. Eight ACTH-secreting microadenomas were detected with CMRI and 11 with DMRI. The three microadenomas detected with DMRI only were visualized within 60 sec following Gad injection. No false positives occurred with CMRI. Three false positives were obtained with DMRI: one in a patient with ectopic ACTH syndrome while a silent microprolactinoma and normal tissue were found at the site of the radiological abnormality in two patients with Cushing's disease. In our study, the sensitivity of DMRI is greater than that of CMRI (0.67 vs. 0.52) but is associated with a loss in specificity (0.80 vs. 1.00). False positives may result from the increased sensitivity of DMRI which detects incidental pituitary lesions, technical artefacts or lowest clarity of images, as suggested by a lower observer agreement of DMRI (Kappa statistic 0.66 vs. 0.83). Overall, the two MR procedures had equivalent diagnostic power (0.72). CONCLUSIONS: In our hands, dynamic procedures did not improve the usefulness of MRI in Cushing's syndrome.

ACTH Syndrome, Ectopic↗
PubMed1998

Human intestinal epithelial cells respond to Cryptosporidium parvum infection with increased prostaglandin H synthase 2 expression and prostaglandin E2 and F2alpha production.

Cryptosporidium parvum is an important cause of diarrhea in humans and several animal species. Prostaglandins play a central role in regulating intestinal fluid secretion in animal models of cryptosporidiosis, but their cellular sources and mechanisms of induction are unclear. Here, we show that C. parvum infection directly activates prostaglandin H synthase 2 expression and prostaglandin E2 and F2alpha production in human intestinal epithelial cells.

Animals↗
PubMed1998

Alteration of milk fat by variation in the source and amount of starch in a total mixed diet fed to dairy cows.

The effect on milk yield and composition of the supplementation of the diets of dairy cows with wheat or potato peelings was studied at three different starch intakes (< 5, 6, and > 7.5 kg/d) for dry matter intakes around 20 kg/d. Starch supply was varied using different dietary concentrations of corn silage. Trials were conducted using Latin square designs, and all cows were fed a total mixed diet composed of corn silage, grass silage, or both; soybean meal; a mixed meal with formaldehyde treatment; minerals; and one of the following energy concentrates: potato peelings or wheat. Dry matter and energy intakes varied significantly only at the low starch concentration; higher intakes were observed when the potato peelings were fed. Body weight, milk yield, true protein content, lactose content, and protein yield were not affected by treatment. Milk fat content was higher (+3.3 g/kg) when potato peelings were fed at the high starch concentration but was unaffected at the low and medium starch concentration. Slow degradation of starch from the potato peelings in the rumen could enhance a higher delivery of precursors of milk fat synthesis in the udder. The effect on fat yield differed among starch concentrations. Milk fat content appeared to decrease for cows fed diets containing quickly degradable starch at a starch intake > 7 kg/d.

Animal Nutritional Physiological Phenomena↗
PubMed1998

[Comparison of echocardiographic automatic border detection and magnetic resonance imaging. Measurements of the left ventricle in normal subjects].

Echocardiographic automatic border detection (ABD) has been the object of several studies with diverging results. The aim of this study was to verify the validity of ABD measurements by comparison with magnetic resonance imaging (MRI). Twenty healthy subjects underwent measurement of end systolic surface (ESA) and end diastolic surface areas (EDA) and fraction of surface variation (FSV), end systolic volume (ESV), end diastolic volume (EDV and ejection fraction (EF). These results were compared with the same parameters measured by cine MRI and a study of the variability of interpretation was performed on the echocardiographic parameters. An ABD analysis was possible in 80% of the study population. The correlations were satisfactory between the EDA and EDV (EDA; r = 0.84; SD = 1.9 cm2; EDV; r = 0.90; SD = 12 ml) with acceptable confidence intervals (CI) (EDA; [-4.02; 1.19 cm2]/EDV; [26; +7.9 ml]) and an underestimation of ABD values (EDA; -9%/EDV: -10%). With regards to the end systolic measurements, the correlations were not as good (ESA: r = 0.68; SD = 1.5 cm2/EDV: r = 0.59; +12 ml) with a more important measurement error (ESA: -2.05; +3.45 cm2)/EDA: (-9; +27 ml) and an overestimation of the ABD values (ESA; +10%; ESV; +18%). No correlation was observed between the FSV and EF. The intra and inter-observer errors were compared with those of conventional echocardiography (intra-observer error; 10.7-16.9%/inter-observer error; 10.8-16.6%). The authors conclude that ABD has a non-negligeable measurement error which limits its application in clinical practice. New transducers, automatisation of gain adjustment and new technologies should improve ABD measurements.

Adult↗
PubMed1998

[SCA 40 and derivatives: new bronchodilators in an imidazo(1,2-a)pyrazine series].

Asthma is a complex disease characterised by bronchoconstriction and airways inflammation. Recent advances in medicinal chemistry will surely lead to a better reappraisal of therapeutic strategies. 8-(Methylamino)imidazo(1,2-a)pyrazines with substitution either on position 2 or 3 powerful relaxing agents in vitro as well as in vivo in animals. 6-Bromo-8-(methylamino)imidazo[1,2-a]pyrazine- 2-carbonitrile, SCA40, is a new and potent bronchodilator. Chemical synthesis of such a series of derivatives involves a condensation reaction with formation of the imidazole ring and/or diverse electrophilic substitutions. Chemical reactivity of the heterocycle can be modulated by introduction on position 8 of electrodonating groups that highly favor electrophilic substitution on position 3. Interestingly, lithiation studies on the heterocycle exhibit regioselectivity, leading either to an halogen exchange when position 3 is occupied by a bromine atom or an ortho-directed metalation in accord with the presence of an halogen on position 6.

Bronchodilator Agents↗
PubMed1997

[Diagnosis of Conn's adenoma. Comparative study of x-ray computed tomography and scintigraphy using 19-noriodocholesterol].

OBJECTIVE: In order to differentiate an aldosterone producing adenoma (APA) and a bilateral adrenal hyperplasia (BAH) in case of primary hyperaldosteronism, an adrenal CT-scan is usually used as first line exploration. The contribution of adrenal 19-noriodocholesterol (NP59)-scintigraphy is controversial. PATIENTS AND METHODS: We describe 17 cases of primary hyperaldosteronism referred to surgery for suspected APA. The value of abdominal CT-scan and of adrenal scintigraphy was studied. RESULTS: After unilateral adrenalectomy, 15 cases with confirmed APA were cured and 2 cases with an unilateral hyperplastic macro nodule showed persistence of the disease. The pathologic findings were concordant with CT-scan in 76% (13/17) and with scintigraphy in 88% (15/17). Similar sensitivity was found for CT-scan and scintigraphy (86% and 88%) with 2 false negative results with both techniques. False positive results were observed only with CT-scan (2 cases) suggesting that scintigraphy has a better specificity. No case was misdiagnosed by both techniques. CONCLUSION: These results suggest that NP59-scintigraphy is complementary to adrenal CT-scan for the recognition of APA and is particularly useful in case of a unilateral hyperplastic macro nodule mimicking an APA.

19-Iodocholesterol↗
PubMed1997

Effects of SCA40 on bovine trachealis muscle and on cyclic nucleotide phosphodiesterases.

While UK-93,928 (1-[[3-(6,9-dihydro-6-oxo-9-propyl-1H-purin-2-yl)-4-ethoxyphenyl] sulfonyl]-4-methylpiperazine; 5 nM-5 microM) was devoid of relaxant activity, benzafentrine, isoprenaline, levcromakalim and SCA40 (6-bromo-8-methylaminoimidazo[1,2-a]pyrazine-2-carbonitrile) each relaxed histamine (460 microM)-precontracted bovine isolated trachealis. Each of these relaxants was antagonised by a K+-rich (80 mM) medium. Except in the case of levcromakalim, nifedipine (1 microM) offset this antagonism. Charybdotoxin (100 nM) antagonised isoprenaline in a nifedipine-sensitive manner but did not antagonise SCA40 or benzafentrine. Iberiotoxin (100 nM) did not antagonise SCA40. Acting on tissue precontracted with carbachol, SCA40 potentiated isoprenaline but did not potentiate sodium nitroprusside. While levcromakalim (1 and 10 microM) induced hyperpolarisation, SCA40 (1 and 10 microM) induced little change in the membrane potential of bovine trachealis. In trachealis preloaded with 86Rb+, levcromakalim (1 and 10 microM) promoted efflux of the radiotracer while SCA40 (1 and 10 microM) had no effect. Tested as an inhibitor of isoenzymes of cyclic nucleotide phosphodiesterase, SCA40 was most potent against the type III, less potent against the type IV and least potent against the type I isoenzyme. It is concluded that neither inhibition of phosphodiesterase type V nor the promotion of BKCa channel opening explains the tracheal smooth muscle relaxant activity of SCA40. This compound relaxes bovine tracheal smooth muscle mainly by inhibiting phosphodiesterase isoenzyme types III and IV.

Animals↗
PubMed1997

Influence of several extracellular matrix components in primary cultures of bovine mammary epithelial cells.

Mammary epithelial cells, obtained from lactating cows, were cultured onto inserts coated with several components of extracellular matrix. The influence of these components upon the maintenance of differentiation has been determinated. Every day, alpha S1-casein secretion was measured by radioimmunoassay (RIA) in apical and basal compartments. Reorganization of functional tight junctions was evaluated by measurement of transepithelial electrical resistance (TER). On EHS matrix, cells underwent alveolar structures and never established TER. alpha S1-casein secretion strongly fluctuated with the day of culture. When plated onto fibronectin, cells reorganized a typical pavement and established TER. Nevertheless, TER and casein secretion highly fluctuated. On laminin-coated inserts, a few cells bound to the substratum, dedifferentiated, and proliferated to confluency within 9 days. TER progressively increased to a stable level after 15 days. Casein was not recovered after 6 days. Cells on type I collagen-coated inserts reorganized an epithelial pavement within 2 days and quickly established a stable TER. They secreted apically high levels of casein during 2 weeks. As cells maintained their biochemical differentiation, the culture on type I collagen-coated inserts seems an efficient model for primary culture of bovine mammary epithelial cells and allows studies of polarized alpha S1-casein secretion.

Animals↗
PubMed1997

15N enrichments of casein and plasma protein amino acids in cows ingesting 15N-labelled ammonium sulphate.

The aim of this work was to determine by ion-exchange liquid chromatography and isotope ratio mass spectrometry the specific 15N enrichment of amino acids in casein and plasma proteins in cows receiving three successive daily oral doses (300, 150 and 150 g) of (15NH4)2SO4 (10 atom per cent isotopic enrichment) and to examine the 15N enrichments obtained with regard to nitrogen transport and metabolism in the lactating cow. To investigate the 15N distribution in amino acids in casein and in plasma proteins, samples of 15N-labelled casein and plasma proteins were extracted either from a pool of several milkings (36-96 h after starting to administer the tracer) or from pooled venous blood (removed on the fourth day after the start of administration) from the four lactating cows. 15N enrichments of the proteins studied, expressed as atoms percent excess, were 0.2509 for casein and 0.0577 for plasma protein. Chromatographic fractionation of the amino acid mixture (protein hydrolysates) resulted in nine groups containing between one and four amino acids: Asp, Ser and Thr; Glu; Pro; Gly; Ala; Val and Met; Ileu and Leu; Tyr; Phe; His and Lys; and Arg. High 15N incorporation was demonstrated in all individual or groups of amino acids studied. In both proteins, Glu appeared to be the most enriched amino acid, Phe and Arg the least enriched. Most aliphatic molecules with a single amino group were highly enriched. The much lower (3.5-7.7-fold) enrichments in plasma protein compared with casein suggest considerable intracellular dilution at the site of liver protein synthesis. Finally, the amino acid separation methods are discussed and suggestions for improving them considered.

Amino Acids↗
PubMed1997

Transmission of nocardiosis and molecular typing of Nocardia species: a short review.

Nocardia species are ubiquitous in the environment and may be found in the soil. They are generally responsible for sporadic pulmonary diseases acquired by inhalation of spores, with secondary localizations in the central nervous system and subcutaneous tissues. There is no absolute evidence for person to person transmission. Presumptive outbreaks of nocardiosis were observed in immunocompromised patients, more frequently in kidney transplant patients than in cardiac transplant patients. Nocardia spp., being present in dust particles, closure and disinfection of the transplantation unit with formaldehyde arrested the sequence of cases of nocardiosis. The original sources of the Nocardia sp. remain doubtful. Other possible sources of contamination are other patients, medical staff and the hospital environment. The first studies of Nocardia spp. typing were based on the detection of extracellular antigens, on the susceptibility of actinomycete strains to killer yeasts, and on the biochemical profiles with fluorogenic substrate. The use of molecular typing techniques have given very promising results. Analysis of plasmid profiles is an interesting way to compare the identity of isolates, although the reliability of this method depends of the presence of plasmids in the isolates. Other typing methods, including analysis of restriction length fragment polymorphism of total DNA, ribosomal DNA fingerprinting, require further investigations to evaluate their discriminating power or to be easily interpretable, whereas a random amplified polymorphic DNA (RAPD) assay was successful for epidemiological purposes. Progress in epidemiological analysis of cases of nocardiosis will be consistent when an improved diagnosis of this infection (molecular and serological diagnosis) will be available, when the genetic diversity of Nocardia spp. isolates will be better known, and when molecular typing, that hold promise in complementing investigations of outbreak of these infections, will be systematically performed when an abnormal increase of cases of nocardiosis in a population with risk factors is observed.

Disease Outbreaks↗
PubMed1997

Cryptosporidium parvum infection of human intestinal epithelial cells induces the polarized secretion of C-X-C chemokines.

Cryptosporidium parvum infects intestinal epithelial cells and does not invade deeper layers of the intestinal mucosa. Nonetheless, an inflammatory cell infiltrate that consists of neutrophils and mononuclear cells is often present in the lamina propria, which underlies the epithelium. This study investigated the host epithelial cell response to C. parvum by assessing in vitro and in vivo the expression and production of proinflammatory cytokines by intestinal epithelial cells after infection. The human colon epithelial cell lines HCT-8 and Caco-2 and human intestinal xenografts in SCID mice were infected with C. parvum. The expression and secretion of the C-X-C chemokines interleukin-8 (IL-8) and GROalpha were determined by reverse transcription-PCR analysis and enzyme-linked immunosorbent assay. Our results demonstrate that upregulated expression and secretion of IL-8 and GROalpha after C. parvum infection of intestinal epithelial cells first occurred 16 to 24 h after infection and increased over the ensuing 1 to 2 days. The kinetics of C-X-C chemokine production by C. parvum-infected epithelial cells contrast markedly with the rapid but transient expression of C-X-C chemokines by epithelial cells infected with invasive enteric bacteria. C-X-C chemokine secretion in C. parvum-infected epithelial cells occurred predominantly from the basolateral surface in polarized monolayers of Caco-2 cells grown in Transwell cultures, whereas cell lysis occurred at the apical surface. The basolateral secretion of IL-8 and GROalpha from C. parvum-infected epithelial cells suggests that C-X-C chemokines produced by those cells contribute to the mucosal inflammatory cell infiltrate in the underlying intestinal mucosa.

Animals↗
PubMed1997

Molecular study of persistence of Nocardia asteroides and Nocardia otitidiscaviarum strains in patients with long-term nocardiosis.

Three Nocardia asteroides and five Nocardia otitidiscaviarum isolates recovered from three patients with long-term nocardiosis were compared by random amplification of polymorphic DNA fingerprinting, antibiotic susceptibility testing, and enzymatic characterization. Results obtained with primer DKU49 (P. Palittapongarnpim, S. Chomyc, A. Fanning, and D. Kunimoto, J. Infect. Dis. 167:975-978, 1993) provide evidence that patient A was infected by two N. asteroides strains during a single episode of nocardiosis and that patients B and C remained infected by the same strain, respectively. Resistance to minocycline that was present in the first isolate recovered from patient B reverted to intermediate resistance in the second isolate and reverted to susceptibility in the third isolate. Resistance to penicillin G and beta-lactams was acquired by the second isolate obtained from patient C.

DNA Fingerprinting↗
PubMed1997

[Venous endoprosthesis. Palliative treatment of superior caval syndrome of neoplastic origin].

Twenty-three patients with SVC syndrome were evaluated with CT and venography. The superior vena cava or its tributaries were either stenosed or thrombosed. The etiology was malignant in all cases: non small cell carcinoma (16 cases), mediastinal nodal metastasis (3 cases), lymphomas (2 cases), pleural mesothelioma (1 case), small cell carcinoma (1 case). The length of the stenosis ranged from 20 to 70 mm. The stents were placed via a femoral, jugular or brachial approach. Stenting was achieved in 22/23 patients (96%). Clinical symptoms subsided in 20/22 patients (87%). Mean follow-up was 15 weeks. Stents remained patent in 17/20 patients (78%). Stenting is a safe and effective treatment of SVC syndrome in patients with malignant conditions.

Adolescent↗
PubMed1997

[Techniques of MRI cholangiopancreatography. History, current status and future prospects].

Magnetic resonance cholangiopancreatography (MRCP) is a recent, non invasive, diagnostic modality capable of producing high quality images of biliary and pancreatic ducts. On the basis of the literature and our experience, we report the history and the current status of this new technology, including 2D, 3D and single shot fast spin echo sequences. As perspectives echo-planar imaging and functional imaging are discussed.

Bile Ducts↗
PubMed1996

Radiological findings in nine AIDS patients with Rhodococcus equi pneumonia.

Rhodococcus equi (R. equi) infections have been incidentally reported as a cause of pulmonary infection in severely immunocompromised hosts, including AIDS patients. Our purpose is to describe the radiological findings in nine AIDS patients with R. equi pneumonia assessed by bronchoalveolar lavage (BAL), biopsies, cultures of sputum, and hemocultures. All patients were examined by chest radiographs and contrast-medium-enhanced chest CT. Dense pulmonary consolidations with or without cavitations accounted for the most striking radiological patterns. Chest CT also revealed six mediastinal involvements, strongly mimicking a lymphoma. Two of them had multiple bilateral pulmonary nodular opacities. Pleural effusion was not identified. Although intensive therapies were administered, seven among nine patients died within few months. In an AIDS patient living in a rural area or exposed to horses and presenting these radiological patterns, the possibility of R. equi pneumonia should be considered in the differential diagnosis along with other infectious diseases or lymphomas.

AIDS-Related Opportunistic Infections↗
PubMed1996

Smooth muscle relaxant activity of A1- and A2-selective adenosine receptor agonists in guinea pig trachea: involvement of potassium channels.

The relaxant activities of N6-cyclopentyladenosine (CPA), an A1-selective agonist, and of 5'-(N-cyclopropyl)-carboxamidoadenosine (CPCA), a potent A2-receptor agonist, in the carbachol-contracted guinea pig isolated trachea have been evaluated. Both CPA and CPCA induced concentration-dependent relaxations of the guinea pig trachea, CPCA demonstrating a more potent but less efficient activity. 8-Cyclopentyl-1,3-dimethylxanthine (CPT) and 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) (10 microM), both selective and potent A1-adenosine receptor antagonists, induced only a weak inhibition of CPA while 3,7-dimethyl-1-propargylxanthine (DMPX) (10 microM), a selective A2-adenosine receptor antagonist, failed to antagonize the relaxant activity of CPA. These results indicate that a major component of the tracheal relaxant activity of CPA occurred by a mechanism which is insensitive to the antagonist potency of A1- and A1-xanthine adenosine antagonists and therefore was not mediated by A1- or A1-adenosine receptors activation. The relaxant activity of CPCA was inhibited by DMPX, which supported the involvement of A2-adenosine receptors. Glibenclamide (10 microM), an inhibitor of KATP-channels, inhibited the relaxant activity of CPCA, whereas it was without effect on CPA. Iberiotoxin (180 nM), an inhibitor of the large-conductance CA2(+)-activated K+ channel, inhibited the relaxant action of CPA and CPCA. However, verapamil can offset the inhibition of CPA provided by iberiotoxin which suggests that such an antagonism does not represent an interaction between the toxin and CPA at the level of the large-conductance CA2(+)-activated K(+)-channel gating but rather functional antagonism attributable to the promotion of CA2+ influx by the toxin. In contrast, verapamil only partially reversed the inhibition of CPCA relaxant activity provided by iberiotoxin. Taken together, these results suggest that A2-adenosine receptor subtypes are coupled to KATP-channels and large-conductance CA2(+)-activated K(+)-channels in the guinea pig trachea whereas the unidentified adenosine receptor subtype, involved in CPA relaxant activity, is not.

Adenosine↗