Dominique Ducassou

Experimental Evaluation of a Collagen-coated Vicryl Mesh as a Dural Substitute

Dural substitutes must provide immediate restitution of a membranous covering for the brain without inducing any adverse reaction in the host or provoking adhesions to underlying nervous tissues. Ideally, the material should disappear completely and be replaced by tissues similar to the dura mater. In this study, parietal dural defects were created in 12 beagle dogs and closed with a vicryl mesh prosthesis made watertight by a film of bovine collagen. Clinical and biological tolerances were satisfactory. There was one case of early local infection. Gross and microscopic examinations performed between 7 days and 9 months after implantation showed degradation of the prosthetic mesh and connective tissue growth into the implant mimicking dura mater as early as 15 days after implantation. There was no attendant inflammatory reaction or cortical adhesions or other adverse reactions. The authors conclude that collagen-embedded vicryl mesh provides satisfactory biological function and compatibility when used as a substitute for dura mater in the dog.

“Luxury perfusion” with99mTc-HMPAO and123I-IMP SPECT imaging during the subacute phase of stroke

To compare the merits of123I-isopropyl-iodoam-phetamine (123I-IMP) and99mTc-HMPAO in showing abnormal brain uptake distribution during cerebral ischemia, we studied ten patients during the subacute phase of their stroke, a period where metabolism and blood flow are frequently uncoupled. SPECT imaging was performed using both radiopharmaceuticals in the 10 patients from 48 h to 4 weeks after onset of symptoms. Two patients out of the 10 had similar defects with123I-IMP and99mTc-HMPAO SPECT, the location of the defects corresponding to the area of infarction observed on CT. Six patients had normal99mTc-HMPAO SPECT and abnormal123I-IMP SPECT with defects in the area of infarction shown by CT. The remaining 2 patients had hyperactive abnormalities on99mTc-HMPAO in areas corresponding to defects on the123I-IMP images. Two of the patients with SPECT mismatches were studied again more than 1 month after onset. On reexamination,99mTc-HMPAO SPECT which was previously normal or hyperactive became hypoactive with a focal area of decreased activity corresponding to the defect on123I-IMP. Crossed cerebellar diaschisis was found in 7 patients with99mTc-HMPAO and was absent for both123I-IMP and99mTc-HMPAO in 3. We suggest that SPECT with99mTc-HMPAO could show transient hyperemia not demonstrated by123I-IMP whereas in some cases cerebral infarction would be more difficult to demonstrate with99mTc-HMPAO than with123I-IMP. SPECT with both tracers is recommended to follow the evolution of strokes in terms of regional cerebral blood flow and tissue metabolism.

Effects of S-adenosylmethionine on human articular chondrocyte differentiation: An in vitro study

The effect of S-adenosyl-L-methionine (SAMe) on human articular osteoarthritic chondrocytes was studied using a thick-layer culture model. Three SAMe concentrations were tested (1, 10, and 100 micrograms/ml). For 10 micrograms/ml, the most efficient dose, a significant rise in the incorporation levels of 35S-sulfate and 3H-serine was observed, as was as an increase in the hexuronic acid content. All the parameters seem to express a more active protein synthesis, particularly for proteoglycans. Under the same conditions, the proliferation rate of chondrocytes does not undergo important variations. These results point to a direct action on the cell metabolism but little is known concerning the mechanism involved.

Lessons from an unpleasant surprise: a biochemical strategy for the diagnosis of pheochromocytoma.

Objective To audit the performances of the analytes used in the diagnosis of pheochromocytoma and to present a graphical guideline to help the diagnosis. Design A 5 year retrospective study. Settings Laboratory and departments of a university hospital. Participants In-patients, suspected of bearing a pheochromocytoma, were investigated for urinary metanephrines and catecholamines (photometric method) and vanillylmandelic acid, fractionated catecholamines and metanephrines [high pressure liquid chromatography (HPLC) coupled to electrochemical detection (ED)] urinary excretion. Main outcome Patients with a pheochromocytoma (24 out of 2003 patients) were diagnosed by the combination of normetanephrine and metanephrine determination. Results All analytes but dopamine were significantly elevated in patients with a pheochromocytoma. The area under the receiver operating characteristics (ROC) curves were the highest for total metanephrines, normetanephrine and metanephrine determinations. Because of analytical interferences in the metanephrines determination, the normetanephrine and metanephrine performed better. It is noteworthy that all pheochromocytomas had either normetanephrine or metanephrine levels above their respective optimal threshold (sensitivity 100%). The best optimal threshold performance was reached by the mean of three daily samples. Total or fractionated catecholamines or vanillylmandelic acid were less accurate tools. Conclusion Amongst urinary tests, the combined use of HPLC/ED determination of normetanephrine and metanephrine seems the most effective screening strategy for the diagnosis of pheochromocytoma. The older total metanephrine photometric assay is grieved by analytical interferences.

Feasibility of aortic pulse pressure and pressure wave velocity MRI measurement in young adults.

To investigate the feasibility of assessing, noninvasively, aortic pulse pressure (APP) and pulse wave velocity (PWV) in the ascending aorta of young adults by means of velocity‐encoded magnetic resonance (MR) imaging.

Overnight urinary free cortisol determination: A screening test for the diagnosis of Cushing's syndrome

The collection of urine over 24 h to measure free cortisol (UFC) is used to diagnose Cushings syndrome. However, a complete collection of urine is not easy to achieve and the sampling is frequently inaccurate, so a 24 h collection for the determination of UFC excretion is used as a confirmatory rather than a screening test for Cushings syndrome. Our objective was to evaluate a more convenient urine collection for screening patients suspected of Cushings syndrome.

Assessment of dual-time-point 18F-FDG-PET imaging for pulmonary lesions.

ObjectiveThe objective of this study was to assess suitability of dual-time-point 18F-FDG [(18F)-fluoro-2-deoxyglucose]-PET imaging for differentiating between malignant and benign pulmonary lesions, whose size and maximal standardized uptake values (SUVs) are greater than 10 mm and 2.5, respectively. MethodsA total of 38 patients, 27 with malignant lesions (n = 30), and 11 with benign lesions (n = 22), were investigated by performing two static acquisitions started at mean times t = 79 and t = 158 min after the tracer injection. A model analysis involving tissue 18F-FDG uptake and release has been developed and applied. ResultsMalignant lesions showed a SUV increase between the two acquisitions for 27 of 30 lesions, and a SUV decrease or constancy for the other three. Benign lesions showed a SUV increase in 19 of 22 lesions, and a SUV decrease in three (both increase and decrease were observed for multiple benign lesions in two patients). ConclusionIt is recommended that dual-time-point 18F-FDG-PET imaging is not indicated to differentiate between malignant and benign pulmonary lesions, whose size and maximal SUV are greater than 10 mm and 2.5, respectively. Furthermore, a model analysis suggests that the variation in SUV observed between early and delayed scans may be explained by different values of the 18F-FDG release/uptake ratio.

Plasma concentration of neuropeptide Y in patients with adrenal hypertension

The mechanisms of hypertension during primary hyperaldosteronism and Cushings syndrome are not completely understood. An enhanced vascular sensitivity to noradrenaline has been described in both situations. Neuropeptide Y (NPY) induces direct vasoconstriction and potentiates the action of noradrenaline. Sodium retention and dexamethasone have been shown to increase circulating NPY levels in animals and the expression of NPY in neuroendocrine cells. In order to determine if NPY could be involved in the enhanced vascular sensitivity to noradrenaline associated with adrenocortical hyperactivity, we measured plasma NPY in patients with Cushings syndrome (n = 26) and primary hyperaldosteronism (n = 15) and compared it with that of hypertensive patients with pheochromocytomas (n = 13) or essential hypertension (n = 51) and with normotensive controls (n = 47). The concentration of NPY-Like immunoreactivity (NPY-Li) (mean +/- S.E.) in controls was 39.6 +/- 3.0 pg/ml. Elevated concentrations were found in 77% of the samples collected from pheochromocytoma patients (1180.4 +/- 394.0 pg/ml). NPY-Li levels in patients with essential hypertension (35.0 +/- 2.6 pg/ml), primary hyperaldosteronism (31.3 +/- 3.9 pg/ml) and Cushings syndrome (33.1 +/- 4.8 pg/ml) were not different from that of controls. NPY-Li levels in hypertensive and normotensive patients with Cushings syndrome were similar (38.5 +/- 7.5 vs 24.2 +/- 3.7 pg/ml). No correlation was found between the NPY-Li level and the mean blood pressure at the time of sampling. Our results suggest that NPY is unlikely to be involved in the pathogenesis of hypertension associated with primary hyperaldosteronism and Cushings syndrome.

In vitro evaluation of an epoxy resin's cytocompatibility using cell lines and human differentiated cells

The cytocompatibility of a polyepoxy resin (Elf Aquitaine) has been studied using both cell lines and human differentiated cell cultures. The human models were gingival fibroblasts and bone osteoblasts, while the cell lines were Hela cells and 3T3 Balb/c cells. Basal cytocompatibility was assessed by estimation of the cell proliferation, total cell protein content, cell membrane sub-lysis, and cell attachment and spreading. Specific cytocompatibility concerning human osteoblasts, from both alveolar and trabecular bone, was determined by measuring the intracellular alkaline phosphatase activity. Resin colonization by the cells was studied by both TEM and SEM. The behaviour of the two cell lines reveals a significant level of discrepancy, whereas the behaviour of human cells, whatever the model, is comparable; however, osteoblasts look more sensitive. Moreover, the results show that this epoxy resin exhibits a moderate cytocompatibility which could be the result of the cytotoxicity of early released products, associated with the considerable surface roughness.

The Effect of Renal Failure on 18F-FDG Uptake: A Theoretic Assessment

This work addresses the issue of using 18F-FDG PET in patients with renal failure. Methods: A model analysis has been developed to compare tissue 18F-FDG uptake in a patient who has normal renal function with uptake in a theoretic limiting case that assumes tracer plasma decay is tracer physical decay and is trapped irreversibly. Results: This comparison has allowed us to propose, in the limiting case, that the usually injected activity be lowered by a factor of 3. We also proposed that the PET static acquisition be obtained at about 160 min after tracer injection. These 2 proposals were aimed at obtaining a similar patient radiation dose and similar tissue 18F-FDG uptake. Conclusion: In patients with arbitrary renal failure (i.e., between the 2 extremes of normal function and the theoretic limiting case), we propose that the injected activity be lowered (without exceeding a factor of 3) and that the acquisition be started between 45 and 160 min after tracer injection, depending on the severity of renal failure. Furthermore, the model also shows that the more severe the renal failure is, the more overestimated is the standardized uptake value, unless the renal failure indirectly impairs tissue sensitivity to insulin and hence glucose metabolism.