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Biomedical subjects

A Leblanc

Publications and source records attributed to A Leblanc.

At least 19 recordsLinked to original sources
PubMed2005

[Post lumbar puncture headache in general pediatrics: a prospective multicenter study].

PURPOSE: To investigate the frequency of post lumbar puncture headaches (PLPH) after diagnostic lumbar puncture (LP) and to search for influence factors. PATIENTS AND METHODS: Conducted over 6 months into 8 paediatric services, the study concerned 2 to 15 years old children. The LP technic (cannula gauge, bevel orientation, child position, reinsertion of the stylet) was standardised. For each child questionnaires were filled with the parents 3 and 8 days after LP for inquiring headaches, postural characteristics, length and clinical consequences. RESULTS: Among 84 charts, 71 were exploitable. PLPH were observed in 25% of children. The mean duration was 5.9 days, mean bed rest was 1.4 day and mean antalgic treatment 1.7 day. The frequency of PLPH was not significantly influenced by age and sex, neither by the qualification of the physician performing the LP. The frequency was significantly lower when LP execution was easy (19.6 vs. 46.7%; P < 0.05), and when the child had viral meningitis (8 vs. 34.8%; P < 0.05). CONCLUSION: We have found a more important frequency of PLPH than in previous paediatric studies. Clinical consequences justify other researches to precise influence factors and reduce the frequency of this complication.

Adolescent↗
PubMed2002

[Methadone poisoning in a 1-year-old child treated by continuous infusion of naloxone].

UNLABELLED: Methadone is a synthetic narcotic used in opioid dependent situations. Child intoxications are harmful, sometimes responsible for death. CASE REPORT: An one-year-old infant was seen in the emergency room, two hours after accidental methadone ingestion. He presented with coma, myosis and respiratory depression. After intubation, symptoms disappeared with naloxone injection. For maintaining this child safe, naloxone was given by continuous infusion during 48 hours. CONCLUSION: Patients, families and professionals should be informed of the risks of methadone intoxication. Owing to methadone long duration of action, initial injection of naloxone, the specific opioid antagonist, must be followed by continuous infusion.

Accidents↗
PubMed2001

Kinetic studies of guinea pig liver transglutaminase reveal a general-base-catalyzed deacylation mechanism.

Guinea pig liver transglutaminase (TGase) reacts with 0.1 mM N-Cbz-L-Glu(gamma-p-nitrophenyl ester)Gly (5, prepared herein, K(M) = 0.02 mM) to undergo rapid acylation that can be followed spectrophotometrically at 400 nm (pH 7.0, 25 degrees C). Deacylation of the transiently formed thiolester acyl enzyme intermediate via catalytic aminolysis was studied in the presence of six primary amines of widely varying basicity (pK(NH+) = 5.6-10.5). Steady-state kinetic studies were performed to measure k(cat) and K(M) values for each amine substrate. A Brønsted plot constructed through the correlation of log(k(cat)/K(M)) and pK(NH+) for each amine substrate displays a linear free-energy relationship with a slope beta(nuc) = -0.37 +/- 0.08. The shallow negative slope is consistent with a general-base-catalyzed deacylation mechanism in which a proton is removed from the amine substrate during its rate-limiting nucleophilic attack on the thiolester carbonyl. Kinetic isotope effects were measured for four acceptor substrates (water, kie = 1.1 +/- 0.1; aminoacetonitrile, kie = 5.9 +/- 1.2; glycine methyl ester, kie = 3.4 +/- 0.7; N-Ac-L-lysine methyl ester, kie = 1.1 +/- 0.1) and are consistent with a proton in flight at the rate-limiting transition state. The active site general-base implicated by these kinetic results is believed to be His-334, of the highly conserved TGase Cys-His-Asp catalytic triad.

Acylation↗
PubMed2001

Mechanisms of insulin resistance in cystic fibrosis.

Cystic fibrosis (CF) is associated with a high incidence of diabetes. Studies evaluating causes of CF-related diabetes (CFRD) have consistently documented decreased insulin secretion. In patients with CFRD, insulin sensitivity has been documented to be decreased, but controversy exists in patients with normal or impaired glucose tolerance (IGT). We undertook this study 1) to reexplore insulin sensitivity in patients with IGT and 2) to evaluate potential mechanisms of insulin resistance in CF, including GLUT-4 translocation, elevation of serum cytokines, and free fatty acid (FFA) levels. We recruited nine CF subjects with impaired glucose tolerance (IGTCF) and nine age-, gender-, and body mass index-matched control volunteers. Each underwent a hyperinsulinemic euglycemic clamp (200 mU. m(-2). min(-1)) to measure insulin sensitivity. A muscle biopsy was obtained at maximal insulin stimulation for measure of GLUT-4 translocation with sucrose gradients. An oral glucose tolerance test and National Institutes of Health (NIH) clinical status scores were measured in all volunteers. We also measured tumor necrosis factor (TNF)-alpha levels and FFA in all subjects. Additionally, we report the results of TNF-alpha and FFA in 32 CF patients previously studied by our group. Results were that glucose disposal rate (GDR) was significantly lower in the CFIGT subjects than in controls, indicative of impaired insulin action. GLUT-4 translocation was impaired in CF and correlated with GDR. TNF-alpha levels were higher in all CF subjects than in controls and correlated with GDR. There was no difference in FFA between CF and control subjects. Modified NIH clinical status scores were inversely correlated with GDR and TNF-alpha levels. We conclude that IGTCF patients have decreased peripheral insulin sensitivity. Mechanisms include elevation of TNF-alpha and impaired translocation of GLUT-4.

Adult↗
PubMed2001

Effects of long-duration bed rest on structural compartments of m. soleus in man.

Magnetic resonance imaging (MRI), histomorphometry and electron microscopy of muscle demonstrate that long-term exposure to actual or simulated weightlessness (including head down bed rest) leads to decreased volume of antigravity muscles in mammals. In muscles interbundle space is occupied by the connective tissue. Rat studies show that hindlimb unloading induces muscle fiber atrophy along with increase in muscle non-fiber connective tissue compartment. Beside that, usually 20% of the muscle fiber volume is comprised by non-contractile (non-myofibrillar) compartment. The aim of the present study was to compare changes in muscle volume, and in muscle fiber size with alterations in myofibrillar apparatus, and in connective tissue compartment in human m. soleus under conditions of 120 day long head down bed rest (HDBR).

Adult↗
PubMed1999

Guinea pig liver transglutaminase: A modified purification procedure affording enzyme with superior activity in greater yield.

Tissue transglutaminase purified from guinea pig livers has a very broad substrate specificity in comparison with other members of the transglutaminase family and therefore is useful for substrate analogue kinetic studies. Modifications made in our laboratory to the standard purification protocol (J. E. Folk and S. I. Chung, 1985, Methods Enzymol. 113, 358-364) have yielded a 28% increase in specific activity and 55% increase in overall yield, while reducing the number of steps to the purification. Herein we report some of the highest yields and specific activities for guinea pig liver transglutaminase found in the literature, as well as the use of lyophilization as a solution to the long-standing problem of enzyme stability during storage.

Animals↗
PubMed1999

Acute unilateral visual loss due to a single intranasal methamphetamine abuse.

An otherwise healthy 35 year old male with insulin-dependent diabetes mellitus (IDDM) presented himself three days after a single intranasal methamphetamine abusus. Directly upon awakening the day after the recreational use of this drug, he discovered an acute and severe visual loss of his right eye. This unilateral loss of vision was permanent and eventually lead to a pale and atrophic optic nerve head. The characteristics of this visual loss, together with the aspect of the optic nerve head was very similar to the classical non-arteritic ischemic optic neuropathy (NAION). We suggest a direct ischemic episode to the short posterior ciliary arteries due to this single intranasal abuse of methamphetamine as the underlying pathogenesis of this acute and permanent visual loss.

Administration, Inhalation↗
PubMed1998

Collagen cross-link excretion during space flight and bed rest.

Extended exposure to weightlessness results in bone loss. However, little information exists as to the precise nature or time course of this bone loss. Bone resorption results in the release of collagen breakdown products, including N-telopeptide and the pyridinium (PYD) cross-links, pyridinoline and deoxypyridinoline. Urinary pyridinoline and deoxypyridinoline are known to increase during bed rest. We assessed excretion of PYD cross-links and N-telopeptide before, during, and after long (28-day, 59-day, and 84-day) Skylab missions, as well as during short (14-day) and long (119-day) bed-rest studies. During space flight, the urinary cross-link excretion level was twice those observed before flight. Urinary excretion levels of the collagen breakdown products were also 40-50% higher, during short and long bed rest, than before. These results clearly show that the changes in bone metabolism associated with space flight involve increased resorption. The rate of response (i.e. within days to weeks) suggests that alterations in bone metabolism are an early effect of weightlessness. These studies are important for a better understanding of bone metabolism in space crews and in those who are bedridden.

Adult↗
PubMed1997

Regional variation in vertebral bone density and trabecular architecture are influenced by osteoarthritic change and osteoporosis.

STUDY DESIGN: The effects of age-related osteoarthritic disease and bone loss on cortical and trabecular bone density in the human spine were analyzed. Changes were quantified by a new method of computed quantitative radiography. Using this method, the relative losses of bone mineral from specific areas and the specific redistribution of bone within vertebrae as a function of age-related bone loss and osteoarthritic change were determined. OBJECTIVES: To quantify the effects of age-related bone loss and osteoarthritic disease on cortical and trabecular density in the human spine by the use of a new method of computed quantitative radiography. SUMMARY OF BACKGROUND DATA: To the authors' knowledge, osteoarthritic and age-related changes resulting in the relative loss of bone mineral from specific areas within vertebrae have never been quantitatively studied. METHODS: Seventy-four vertebrae were obtained from 23 normal, human subjects at autopsy. Vertebral bodies were measured by dual-energy x-ray absorption, and then sectioned for analysis by computerized quantitative radiography. Attention was focused on overall bone density, regional cancellous bone density, and cortical bone density (anterior cortex, superior, and inferior endplates) for both mid-sagittal and para-sagittal sections. One hundred forty sections were so analyzed. RESULTS: Quantitative radiography demonstrated previously undescribed, well defined patterns of cortical and trabecular architecture and bone density within vertebral bodies that were uniform among vertebrae, but strongly influenced by osteoarthritic change and bone loss. These changes were neither detected nor documented by dual-energy x-ray absorption. CONCLUSIONS: Understanding the patterns of bone lose, and knowing how osteoarthritic change affects normal bone loss yields insight into the pathophysiology of the aging process and osteoarthritic disorders. Knowledge of the variations in density and microanatomy within vertebrae may improve techniques of internal fixation and designs of spinal implants, and may help to clarify the pathogenesis of clinical problems such as fractures.

Absorptiometry, Photon↗
PubMed1996

Increased blood manganese in cirrhotic patients: relationship to pallidal magnetic resonance signal hyperintensity and neurological symptoms.

Increasing evidence suggests that manganese deposition is responsible for the T1-weighted magnetic resonance imaging (MRI) signal hyperintensity consistently observed in pallidum of cirrhotic patients. However, the relationship between blood manganese and the etiology or severity of liver disease, as well as the neurological symptomatology in these patients, has not been well established. In the present study, blood manganese concentrations were measured by atomic absorption spectrometry together with MRI and neurological evaluation in 57 cirrhotic patients with various etiologies and severity of liver disease. Blood manganese concentrations were elevated in 67% of cirrhotic patients and were significantly higher in patients with previous portacaval anastomoses or transjugular intrahepatic portosystemic shunt (TIPS). Pallidal signal hyperintensity was observed in 88% of patients, and significant correlations were demonstrated between blood manganese and pallidal index (PI) (a measure of pallidal signal hyperintensity), as well as Child-Pugh score. Assessment of extrapyramidal symptoms using the Columbia rating scale revealed a significant incidence of tremor, rigidity, or akinesia in up to 89% of cirrhotic patients. However, there was no significant correlation between blood manganese and extrapyramidal symptoms, although severity of akinesia was significantly greater in Child-Pugh C patients. Extrapyramidal symptoms could result from a toxic effect of manganese on basal ganglia dopaminergic function. These findings further support a role for manganese in the etiology of pallidal MRI signal hyperintensity in patients with chronic liver disease.

Adult↗
PubMed1996

Effects of spaceflight on bone mineralization in the rhesus monkey.

We combined dual-photon absorptiometry, iliac crest histomorphometry, and backscattered electrons analysis to characterize bone mineralization effects of a spaceflight on young monkeys. Two 4- to 5-kg male rhesus monkeys (Macaca mulatta) were flown during a 11.5-day spaceflight that took place onboard Cosmos 2229 biosatellite (Bion 10). Vivarium (n = 4) and Earth-based chair (n = 4) control situations were studied for comparison. Flight monkeys exhibited lower values of iliac cancellous bone volume, associated with nonsignificantly thinner trabeculae. Bone mineralization rate and the proportion of trabecular bone surface involved in mineralization processes were found markedly reduced after spaceflight. Analysis of embedded sections by backscattered electrons imaging showed a nonsignificant shift to lower mineralization in the flight biopsies vs. postflight mock-up biopsies. These results were in accordance with dual-photon absorptiometry evaluations showing a tendency for decreased bone mineral content during flight and recovery thereafter. The ground simulation experiment performed on the same monkeys more than 1 mo after landing suggests that the observed effects were specifically related to spaceflight and that the animals had only partially recovered. Additional animals on future flights will be required to confirm these findings.

Absorptiometry, Photon↗
PubMed1994

Ultrasound diagnosis of thymic hemorrhage in an infant with late-onset hemorrhagic disease.

Thymic hemorrhage related to coagulopathy by vitamin K deficiency is a rare condition. We report a case in a 4-week-old boy presenting with acute onset of respiratory distress and anemia. Ultrasound examination of a compressive anterior mediastinal mass established the diagnosis of thymic hemorrhage and allowed us to follow resolution under medical treatment.

Acute Disease↗
PubMed1993

Reliability and feasibility of pregnancy home-use tests: laboratory validation and diagnostic evaluation by 638 volunteers.

All 27 home-use tests sold in France in 1989 for the self-diagnosis of pregnancy were evaluated. The kits were first tested by qualified clinical chemistry technologists. Eleven kits with 100% specificity and 100% sensitivity were retained for the diagnostic study. Each of 638 laywomen was given a kit and asked to perform the assay with a coded urine specimen containing either no human chorionic gonadotropin (hCG) or an hCG concentration adjusted to the claimed detection limit (1 DL) or twice the detection limit (2 DL). After testing, each participant filled out a detailed questionnaire. The results showed a diagnostic specificity of 86-100% for 10 kits but a diagnostic sensitivity of 85-100% for only 5 kits at 2 DL and for only 2 at 1 DL. Among the 478 positive urine samples distributed, 230 were falsely interpreted as negative. The main explanation for such a high percentage of false-negative results was difficulty in understanding the explanatory leaflets accompanying the kits and hence in reading the results, regardless of the socioeconomic situation of the participant. We conclude that pregnancy home-use tests should be subjected to rigorous analytical controls and evaluated by a panel of potential users before being released on the market.

Adolescent↗
PubMed1991

Ten years of external quality assessment in France.

Since 1979, a national external quality assessment (EQA) scheme has been conducted in France by the Laboratoire National de la Santé. At present, as many as 4990 laboratories participate in the EQA. The general organization and strategies of this national scheme are briefly described in this paper and a few examples are given to illustrate its impact on laboratory performance.

Chemistry, Clinical↗