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Biomedical subjects

P Gillet

Publications and source records attributed to P Gillet.

At least 19 recordsLinked to original sources
PubMed2000

Raman spectroscopy of iron to 152 gigapascals: implications for Earth's inner core

Raman spectra of hexagonal close-packed iron (varepsilon-Fe) have been measured from 15 to 152 gigapascals by using diamond-anvil cells with ultrapure synthetic diamond anvils. The results give a Gruneisen parameter gamma(0) = 1.68 (+/-0.20) and q = 0.7 (+/-0.5). Phenomenological modeling shows that the Raman-active mode can be approximately correlated with an acoustic phonon and thus provides direct information about the high-pressure elastic properties of iron, which have been controversial. In particular, the C(44) elastic modulus is found to be lower than previous determinations. This leads to changes of about 35% at core pressures for shear wave anisotropies.

Journal Article↗
PubMed2000

40K-(40)Ar constraints on recycling continental crust into the mantle

Extraction of potassium into magmas and outgassing of argon during melting constrain the relative amounts of potassium in the crust with respect to those of argon in the atmosphere. No more than 30% of the modern mass of the continents was subducted back into the mantle during Earth's history. It is estimated that 50 to 70% of the subducted sediments are reincorporated into the deep continental crust. A consequence of the limited exchange between the continental crust and the upper mantle is that the chemistry of the upper mantle is driven by exchange of material with the deep mantle.

Journal Article↗
PubMed2000

Natural NaAlSi(3)O(8)-hollandite in the shocked sixiangkou meteorite

The hollandite high-pressure polymorph of plagioclase has been identified in shock-induced melt veins of the Sixiangkou L6 chondrite. It is intimately intergrown with feldspathic glass within grains previously thought to be "maskelynite." The crystallographic nature of the mineral was established by laser micro-Raman spectroscopy and x-ray diffraction. The mineral is tetragonal with the unit cell parameters a = 9.263 +/- 0.003 angstroms and c = 2.706 +/- 0.003 angstroms. Its occurrence with the liquidus pair majorite-pyrope solid solution plus magnesiowustite sets constraints on the peak pressures that prevailed in the shock-induced melt veins. The absence of a calcium ferrite-structured phase sets an upper bound for the crystallization of the hollandite polymorph near 23 gigapascals.

Journal Article↗
PubMed2000

Pefloxacin-induced achilles tendon toxicity in rodents: biochemical changes in proteoglycan synthesis and oxidative damage to collagen.

Despite a relatively low incidence of serious side effects, fluoroquinolones and the fluoroquinolone pefloxacin have been reported to occasionally promote tendinopathy that might result in the complication of spontaneous rupture of tendons. In the present study, we investigated in rodents the intrinsic deleterious effect of pefloxacin (400 mg/kg of body weight) on Achilles tendon proteoglycans and collagen. Proteoglycan synthesis was determined by measurement of in vivo and ex vivo radiosulfate incorporation in mice. Collagen oxidative modifications were measured by carbonyl derivative detection by Western blotting. An experimental model of tendinous ischemia (2 h) and reperfusion (3 days) was achieved in rats. Biphasic changes in proteoglycan synthesis were observed after a single administration of pefloxacin, consisting of an early inhibition followed by a repair-like phase. The depletion phase was accompanied by a marked decrease in the endogenous serum sulfate level and a concomitant increase in the level of sulfate excretion in urine. Studies of ex vivo proteoglycan synthesis confirmed the in vivo results that were obtained. The decrease in proteoglycan anabolism seemed to be a direct effect of pefloxacin on tissue metabolism rather than a consequence of the low concentration of sulfate. Pefloxacin treatment for several days induced oxidative damage of type I collagen, with the alterations being identical to those observed in the experimental tendinous ischemia and reperfusion model. Oxidative damage was prevented by coadministration of N-acetylcysteine (150 mg/kg) to the mice. These results provide the first experimental evidence of a pefloxacin-induced oxidative stress in the Achilles tendon that altered proteoglycan anabolism and oxidized collagen.

Acetylcysteine↗
PubMed2000

[Information by authorities on hospital performance].

Information gathered in hospitals in Belgium by the authorities or their intermediaries is of three types: financial, medico-administrative, and quality of care assessment. From these computerized date bases, the public authorities can now measure socalled hospital "productivity". The aim announced by the authorities is to simultaneously combine increased economic effectiveness with improved quality of care. The use of this new bank of knowledge aims to enforce a sense of responsability to medical care. Regulation of the medical system by "medical management" can apply at various level depending on whether it works "a priori" or "a posteriori" and which or without financial incentives. There is however the risk of creating inaccuracies which must be taken into account when adjusting costs to each particular patient group. The use of all these tools should enable distinguishing between economic and qualitative objectives.

Belgium↗
PubMed2000

Continuous spikes and waves during slow sleep (CSWS): outcome in adulthood.

We report a longitudinal, electroencephalographic and neuropsychological analysis of epilepsy with continuous spikes and waves during slow sleep (CSWS) in a 19 year-old boy. The clinical course fluctuated, with temporary worsening or improvement of the paroxysmal abnormalities, epilepsy and cognitive functions. At the end of the follow-up period, seizures persisted. Evaluation of the boy's behaviour, language and cognitive function suggested a dysexecutive syndrome. We discuss the relationship between paroxysmal abnormalities and neuropsychological disorders.

Adult↗
PubMed1999

Direct repair of spondylolysis without spondylolisthesis, using a rod-screw construct and bone grafting of the pars defect.

STUDY DESIGN: A retrospective study of patient outcome after pars repair using an original technique in patients with spondylolysis without spondylolisthesis and degenerative disk disease. OBJECTIVES: To assess the results of a new technique of internal fixation that avoids penetration of the spinal canal, temporary fixation of the lumbosacral junction, and postoperative bracing owing to stable instrumentation consisting of pedicle screws and a V-shaped rod resting against the inferior aspect on the spinous process and the posterior aspects of the laminas. SUMMARY OF BACKGROUND DATA: Previously described techniques for direct repair of a pars defect often require postoperative bracing and can require intracanal penetration of wires or hooks; screws passing directly through the defect, thereby lessening the bone surface available for bone grafting; and temporary fixation of the lumbosacral junction with a plate that must be removed. METHODS: Patients with painful pars defect not responding to conservative therapy and interfering with everyday life, sports, or work were considered to be eligible for direct repair of the spondylolysis rather than lumbosacral fusion, if there was no associated degenerative disk disease or spondylolisthesis. The surgical technique involves placement of screws on the pedicles of the involved vertebra and the fixation of the loose posterior arch with a solid rod bent in a V shape, taking purchase on the spinous process and laminas. A bone graft is placed under compression in the pars defect before the rod-screw construct is tightened. RESULTS: The first 10 patients who underwent this technique had an average follow-up of 35 months (range, 7 months to 5.3 years); mean age at operation was 26 years (range, 16-48 years). Six patients had an excellent result, returned to normal everyday life and work, and participated in sports when desired. The outcome in one patient was rated good and in one, fair. The procedure in one was considered a failure, although bone fusion seemed to have been obtained. Seven patients would recommend the operation, one would hesitate. No complications were encountered because of the specific design of the construct. CONCLUSIONS: This new technique offers the advantage of being easy and fast, it can be performed using a great number of available spinal instrumentations using rods and pedicle screws. There is no violation of the neural canal except in the case of a misplacement of pedicle screws. No postoperative brace was used, return to everyday life avoiding low back stress was immediate, and return to work or sports was possible 3 to 6 months after the procedure. This technique seems safe and effective but needs careful selection of patients, as do all other techniques for direct repair of pars interarticularis.

Adolescent↗
PubMed1999

Evidence for neurogenic transmission inducing degenerative cartilage damage distant from local inflammation.

OBJECTIVE: To investigate involvement of the nervous system in ipsilateral and contralateral joint inflammation. METHODS: Freund's complete adjuvant (CFA; 1 mg or 1 microg) was injected unilaterally and the messages (a) from the hind paw to the ipsilateral and contralateral knees and (b) from one knee to the contralateral knee were analyzed. The degenerative impact of the local injury on distant cartilage was assessed using patellar proteoglycan synthesis as an indicator. Neurogenic mechanisms were blocked either by spinal cord compression or by injection of neurokinin 1 (NK-1) antagonist, or they were mimicked by intraarticular injection of substance P. The data were compared with those gathered in a model of systemic inflammation, characterized by fever and serum interleukin-6 production. RESULTS: After unilateral subcutaneous injection of CFA, proteoglycan anabolism decreased bilaterally. Spinal cord compression and administration of the NK-1 antagonist inhibited the response in the contralateral limb. Following 1 mg CFA subcutaneous injection, the ipsilateral response implicated both neurogenic and systemic mechanisms, whereas the nervous system alone was implicated after 1 microg subcutaneous CFA injection. The 1 microg CFA intraarticular injection induced a degenerative contralateral signal, which was abolished by spinal cord compression and by pretreatment with the NK-1 antagonist. Intraarticular injection of 1 microg CFA also induced an ipsilateral increase of anabolism, which was enhanced by spinal cord compression. Similar results were obtained after intraarticular injections of substance P. These effects were not reproduced with turpentine treatment, a systemic model, in which spinal cord compression had no effect. CONCLUSION: A unilateral inflammation can induce, by neurogenic mechanisms, distal bilateral degeneration of articular cartilage, implicating involvement of neuropeptides.

Animals↗
PubMed1999

Biotelemetry: an original approach to experimental models of inflammation.

Biotelemetry is a new biological technology which evaluates continuous spontaneous locomotor activity and body temperature in rodents. The telemetry system comprises a transmitter implanted in the peritoneal cavity of the rodent, and a receiver placed beneath the animal's cage. The receiver detects the radio waves and the activity of the rodents as counts which are registered in the computer system, and the adapter detects the calibrated body temperature. First, we showed that biotelemetric studies of different species (rats, guinea pigs, mice and gerbils) provide substantial information about their circadian rhythms. Second, using the most common examples employed in pharmacology of inflammation (hyperthermia, arthritis, ischemia-reperfusion and so on) biotelemetry has helped us to clarify the pathophysiological significance of the parameters of temperature and mobility in several experimental models in rodents.

Animals↗
PubMed1999

Refinement of the chromosome 5p locus for familial calcium pyrophosphate dihydrate deposition disease.

Familial calcium pyrophosphate dihydrate deposition disease (CPPDD) is a disease of articular cartilage that is radiographically characterized by chondrocalcinosis due to the deposition of calcium-containing crystals in affected joints. We have documented the disease in an Argentinean kindred of northern Italian ancestry and in a French kindred from the Alsace region. Both families presented with a common phenotype including early age at onset and deposition of crystals of calcium pyrophosphate dihydrate in a similar pattern of affected joints. Affected family members were karyotypically normal. Linkage to the short arm of chromosome 5 was observed, consistent with a previous report of linkage of the CPPDD phenotype in a large British kindred to the 5p15 region. However, recombinants in the Argentinean kindred have enabled us to designate a region<1 cM in length between the markers D5S416 and D5S2114 as the CPPDD locus.

Calcium Pyrophosphate↗
PubMed1999

Proteoglycan and collagen biochemical variations during fluoroquinolone-induced chondrotoxicity in mice.

Although fluoroquinolone antibacterials have a broad therapeutic use, with a relatively low incidence of severe side effects, they have been reported to induce lesions in the cartilage of growing animals by a mechanism that remains unclear. This study was undertaken to determine the potentially deleterious effect of a high dose of pefloxacin (400 mg/kg of body weight) on two main constituents of cartilage in mice, i.e., proteoglycans and collagen. Variations in levels of proteoglycan anabolism measured by in vivo [(35)S]sulfate incorporation into cartilage and oxidative modifications of collagen assessed by detection of carbonyl derivatives were monitored after administration of pefloxacin. Treatment of mice with 1 day of pefloxacin treatment significantly decreased the rate of biosynthesis of proteoglycan for the first 24 h. However, no difference was observed after 48 h. The decrease in proteoglycan synthesis was accompanied by a marked drop in serum sulfate concentration and a concomitant increase in urinary sulfate excretion. The decrease in proteoglycan synthesis, also observed ex vivo, may suggest a direct effect of pefloxacin on this process, rather than it being a consequence of a low concentration of sulfate. On the other hand, treatment with pefloxacin for 10 days induced oxidative damage to collagen. In conclusion, this study demonstrates, for the first time, that pefloxacin administration to mice leads to modifications in the metabolism and integrity of extracellular proteins, such as collagen and proteoglycans, which may account for the side effects observed. These results offer new insights to explain quinolone-induced disorders in growing articular cartilage.

Animals↗
PubMed1999

Neuropsychologic and adaptive functioning in adolescents and young adults shunted for congenital hydrocephalus.

The major aim of this study was to assess whether the syndrome of nonverbal learning disabilities described in hydrocephalic children is observed in adulthood. Eleven adults shunted for congenital hydrocephalus related to spina bifida and eight adults shunted for hydrocephalus related to aqueductal stenosis were administered an extensive neuropsychologic battery to investigate discrepancies between verbal and visuospatial cognition, verbal and visuospatial long-term memory, and psycho-social adaptive abilities. The results showed no discrepancies between Wechsler Performance IQ or Verbal IQ in either hydrocephalic group. Nevertheless, the subjects with spina bifida appeared more cognitively impaired than the subjects with aqueductal stenosis, who performed normally on the Wechsler Adult Intelligence Scale-Revised. Memory assessment using Signoret's Memory Battery revealed no discrepancy between verbal and visuospatial memory in the hydrocephalic group. Nevertheless, the subjects with spina bifida had poorer verbal and visuospatial memory performance than the subjects with aqueductal stenosis. There were no differences on the Vineland Adaptive Behavioral Scale between subjects with spina bifida and those with aqueductal stenosis in autonomy, socialization, and daily living skills. These results suggest that shunted congenital hydrocephalus is not characterized by nonverbal learning disabilities syndrome in adolescence or in adulthood.

Adaptation, Psychological↗
PubMed1999

Direct costs of hip fractures in patients over 60 years of age in Belgium.

OBJECTIVE: Osteoporosis-related costs are now considered a major burden for health authorities in most developed countries. An accurate and exhaustive evaluation of these costs would be a major contribution to health economic studies evaluating the efficiency of screening and prevention strategies. Osteoporosis is the most frequent underlying cause of femoral neck fractures in the elderly; these fractures weigh heavily on healthcare budgets. However, in Belgium, very few data on the financial burden of hip fractures are available and no updated estimates have been made. The goal of this paper is to estimate the direct medical expenditures associated with hip fractures in Belgium in 1996. DESIGN AND SETTING: This 1-year population-based cross-sectional study is conducted from the social security perspective. The target population in this study are men and women aged 60 years and over. PATIENTS AND PARTICIPANTS: We selected patients who had been hospitalised for a hip fracture during the year 1996 who were also affiliated with a registered social security organisation (covering 25% of the Belgian population). The sample constituted 2374 patients. INTERVENTIONS: For each of these patients, we collected an exhaustive and detailed list of healthcare resource use as well as nursing home admissions following the hip fracture event. Cost items investigated in the analysis were inpatient hospital costs and outpatient costs. Mean annual costs per case recorded in the sample were then extrapolated to the whole country on the basis of an exhaustive list of diagnoses having lead to all countrywide hospitalisations (1,700,000 hospital stays/year). MAIN OUTCOME MEASURES AND RESULTS: The mean hospital inpatient costs for hip fracture were evaluated at 332,148 Belgian francs (BeF) [$US8977] per case and BeF4,367,746,200 ($US118,047,194) for the whole country (10 million inhabitants). Patients with a hip fracture experienced an annual BeF27,825 ($US752) extra outpatient cost during the year following this fracture event, after correcting for costs related to additional comorbidity already present before the hip fracture. Finally, after a proximal femoral neck fracture, the rate of nursing home admission was higher, both for men and women at any age compared with age- and gender-matched population. CONCLUSIONS: With a total cost (acute hospital and outpatient costs) of BeF4,667,894,950 ($US126,159,323) per year in Belgium, proximal femoral neck fracture should be considered a major health economic problem and appropriate measures to prevent this disease should be rapidly undertaken.

Aged↗