[Bone metabolism during pregnancy and breast feeding. Osteoporosis in pregnancy].
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Bone and Bones↗
Biomedical subjects
M Audran
Publications and source records attributed to M Audran.
Comparison of a direct and indirect population pharmacodynamic model: application to recombinant human erythropoietin in athletes.
Basic physiologic indirect response models have been proposed to account for the pharmacodynamics of drugs that act by way of inhibition or stimulation of the production or loss of endogenous substances or mediators. In this work, these models were applied to account for the effects of recombinant human erythropoietin (rHuEpo) in man. Indeed, rHuEpo induces a delayed increase of serum soluble transferrin receptors (sTfr) and a delayed decrease in ferritin (fr) concentrations. The purpose of the present study was to compare two pharmacodynamic approaches to relate serum erythropoietin (Epo) concentrations to the effect of rHuEpo on sTfr, and fr, the "indirect effect" and the "effect compartment" models. However, due to the average lag time of about 50 hr between the first intake of rHuEpo and the onset of the measurable effects, a delay function was incorporated into the "indirect response models" to describe the relationship between the Epo plasma concentrations and the endogenous receptors or mediators affected by the drug and responsible for the effects on sTfr and fr. There are no real differences in the descriptive features of the two models used. For these reasons, the indirect model seems more appropriate because it supplies a possible mechanistic interpretation of the physiological process.
Adult↗
Silica-associated systemic erythematosus lupus or mineral dust lupus?
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Adult↗
Progression in length and width of pagetic lesions, and estimation of age at disease onset.
The mean annual rate of increase in the length of pagetic lesions was 8.5 mm for the skull and tibia and 9.4 mm for the femur, after a follow-up of nine to 16 years according to the bone. The fastest rate of progression was seen at the femur and was 24 mm per year. Thirty years were required for lesions to spread to the entire pelvis and 13 years to all the bones surrounding the obturator foramen. Saber shin deformity of the tibia without involvement of the distal fourth of the bone indicated a disease duration of 25 years, as did involvement of the entire skull. The annual rate of increase in the width of lesions varied widely across patients and was not influenced by gender. Thickening of the skull occurred at a rate of about 4 to 5 mm per decade after pagetization of the bone, although faster rates were seen in some patients; a sandwich-like appearance with a thickness exceeding 32 mm was seen in six of the 29 skulls studied. At the femur and tibia, the increase in width was 10% to 30% per decade after pagetization of the bone; faster thickening was seen in some tibias with saber shin deformity. The thickness of the ischial tuberosity increased by 3 to 4 mm per decade after pagetization. Determination of the degree of hypertrophy is useful for estimating the duration of pagetic lesions when the entire bone is involved at first presentation. Involvement of the entire pelvis indicates a disease duration of 30 to 40 years according to whether the bone is hypertrophied or not. An estimation of age at disease onset in 70 patients suggested that the first bone lesions probably appeared before the age of 30 years in 45 patients (64%), whereas the diagnosis was established before 30 years in only three patients. These data suggest that Paget's disease may be a disease of teenagers and young adults.
Adult↗
Polyostotic Paget's disease. A search for lesions of different durations and for new lesions.
We conducted a medical record-based study of 169 patients with polyostotic involvement identified among 200 Paget's disease patients. Follow-up was 15 to 41 years in 31 cases. The pelvis was the only bone that was more likely than not to be involved bilaterally. All the other paired bones were more likely to be involved unilaterally and when both sides were involved the two lesions were very often frankly asymmetric. In a given patient, the duration of the various pagetic lesions, estimated from their size and from data provided by an earlier study on the rate of progression of pagetic lesions, was similar in some cases and showed marked differences in others. Aggregation of the lesions into two or three disease duration groups was seen in some patients, suggesting that Paget's disease may occur in two or three waves. When we reviewed the radiographs from 30 patients with a mean follow-up of 23 years, we found new lesions in ten patients. However, a review of bone scans from 18 patients with a mean follow-up of 11 years failed to uncover any firm evidence of new lesion development, perhaps because all these patients received bisphosphonate therapy (etidronate, tiludronate, pamidronate). We also found data suggesting that the disease process spread across a joint in some patients, even in the absence of degenerative joint disease. In particular, in several cases an extensive pagetic lesion was seen on one side of a joint and a considerably smaller lesion on the other side.
Adult↗
Epidural involvement in nontuberculous disk space infections. Incidence by magnetic resonance imaging, impact and prognosis.
Eleven of 25 patients admitted for nontuberculous disk space infections had magnetic resonance imaging evidence of epidural infection. No differences were found between the 11 patients with and the 14 patients without epidural infection regarding time to diagnosis, height of fever, presence of nerve root pain, presence of prespinal and/or paraspinal abscesses and proportion of cases due to Staphylococcus aureus. Antimicrobial therapy alone ensured a full recovery with no neurological sequelae in most cases, suggesting that presence of epidural sepsis does not affect the prognosis of nontuberculous disk space infections.
Abscess↗
Cyclodextrins and enantiomeric separations of drugs by liquid chromatography and capillary electrophoresis: basic principles and new developments.
Investigation of individual drug enantiomers is required in pharmacokinetic and pharmacodynamic studies of drugs with a chiral centre. Cyclodextrins (CDs) are extensively used in high-performance liquid chromatography as stationary phases bonded to a solid support or as mobile phase additives in HPLC and capillary electrophoresis (CE) for the separation of chiral compounds. We describe here the basis for the liquid chromatographic and capillary electrophoretic resolution of drug enantiomers and the factors affecting their enantiomeric separation. This review covers the use of CDs and some of their derivatives in studies of compounds of pharmacological interest.
Chemistry, Pharmaceutical↗
Validation of liquid chromatographic and gas chromatographic methods. Applications to pharmacokinetics.
Validations of analytical methods are important for the generation of data for bioavailability, bioequivalence and pharmacokinetic studies. It is essential to use well defined and fully validated analytical methods to obtain reliable results that can be satisfactorily interpreted. This manuscript is intended to provide guiding principles for the evaluation of a method's overall performance. For this purpose, all of the variables of the method are considered, including sampling procedure, sample preparation, chromatographic separation, detection and data evaluation. The criteria considered are as follows: stability, selectivity, limits of quantification and of detection, accuracy, precision, linearity, recovery and ruggedness. Models used for analytical calibration curves are explained in term of validity and limitations, along with a presentation of the most common statistical considerations used to validate the model. Appropriate means of testing precision and accuracy, the most important factors in assessing method quality, are presented. Other issues, such as re-validation, cross-validation, partial sample volume, endogenous drugs and biological matrix of limited availability, are also discussed.
Calibration↗
[Current options for the treatment of Paget's disease of bone].
From 10 to 20% of patients with Paget's disease of bone, including those without patent clinical signs, risk severe neurological, orthopedic or cardiovascular complications. Calcitonin and etidronate were the first drugs allowing a certain degree of control over excessive bone remodeling subsequent to Paget's disease. Further progress has been made with a family of new bisphosphonates (clodronate, pamidronate, tiludronate, alendronate, risedronate, and others). Ideally, treatment should eliminate bone pain, normalize markers, restore normal bone structure, and prevent recurrence and complications. The new generation of bisphosphonates have powerful anti-osteoclasic activity. These easy-to-administer well-tolerated drugs may be indicated in certain asymptomatic patients in the 50-year age range who have active disease and lesions involving the skull (neurological risk) or lower limbs (orthopedic risk). Although there are no data on the cost effectiveness comparing medical or surgical treatment in these forms having reached the stage of complications, the result in terms of pain relief and improved quality of life is real. Further assessment of wider indications for certain non-symptomatic, but threatening forms of the disease, is needed. Prospective studies should focus on medical improvement, quality of life, and cost-effectiveness.
Diphosphonates↗
High-performance liquid chromatographic determination of tazobactam and piperacillin in human plasma and urine.
A high-performance liquid chromatographic (HPLC) method with ultraviolet (UV) absorbance was developed for the analysis of piperacillin-tazobactam (tazocillin), in plasma and urine. The detection was performed at 218 nm for tazobactam and 222 nm for piperacillin. The procedure for assay of these two compounds in plasma and of piperacillin in urine involves the addition of an internal standard (ceftazidime for tazobactam and benzylpenicillin for piperacillin) followed by a treatment of the samples with acetonitrile and chloroform. To quantify tazobactam in urine, diluted samples were analysed using a column-switching technique without internal standard. The HPLC column, LiChrosorb RP-select B, was equilibrated with an eluent mixture composed of acetonitrile-ammonium acetate (pH 5). The proposed technique is reproducible, selective, and reliable. The method has been validated, and stability tests under various conditions have been performed. Linear detector responses were observed for the calibration curve standards in the ranges 5-60 micrograms/ml for tazobactam, and 1-100 micrograms/ml for piperacillin and spans what is currently though to be the clinically relevant range for tazocillin concentrations in body fluids. The limit of quantification was 3 micrograms/ml for tazobactam and 0.5 microgram/ml for piperacillin in plasma and urine. Extraction recoveries from plasma proved to be more than 85%. Precision, expressed as C.V., was in the range 0.4-18%.
Chromatography, High Pressure Liquid↗
Erythropoietin abuse in athletes.
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Adult↗
Pharmacokinetics and haematological parameters of recombinant human erythropoietin after subcutaneous administrations in horses.
The pharmacokinetics of recombinant human Epo (rHuEpo) were investigated after subcutaneous administration to horses. Four horses received a single 30IU kg-1 dose of rHuEpo. One horse received three repeated doses of 120 IU kg-1 at 48 h intervals. Plasma erythropoietin (Epo) was measured by radioimmunoassay. In both cases pharmacokinetic parameters were evaluated using a one-compartment open model and first-order input and output rates. The mean values (+/-SD) for elimination half-life, CL/F, and Vd/F after a single dose were 12.9 +/- 3.34 h, 11.8 +/- 4.96 L h-1, and 233 +/- 126 L, respectively. After repeated doses, elimination half-life, CL/F, and Vdss/F were 11.3 h, 8.94 L h-1, and 145.6 L, respectively. No significant differences were observed between the haematological parameters after a single 30 IU kg-1 administration compared to baseline values. Multiple and high doses of rHuEpo modified red blood cells, haemoglobin, and hematocrit. According to our results, plasma Epo assay can help, during an antidoping control procedure, to support a positive result only up to 72 h after the last rHuEpo.
Animals↗
Altered trabecular architecture induced by corticosteroids: a bone histomorphometric study.
Prolonged corticosteroid (CS) therapy induces osteoporosis and fractures. Osteoporosis is characterized at the histomorphometric level by reduced bone volume (BV/TV) and disruption of the three-dimensional (3D) trabecular architecture. Several stereological methods have been proposed to characterize these alterations: measurements of trabecular thickness and trabecular number, star volumes, interconnectivity index (ICI) of the bone marrow spaces, and trabecular bone pattern factor (TBP(f)). These methods were computerized with a single program running on an image analyzer to evaluate the bone changes in a series of iliac biopsies performed on 31 male patients. All of them were asthmatic and had received CS for a long period of time. BV/TV was reduced when compared with age-matched controls. In the CS-treated population, exponential relationships were obtained between bone volume and the different connectivity parameters. The various methods used to measure connectivity were well correlated. When the population was divided into two groups (BV/TV greater or less than an 11% threshold), the architectural disturbances were found to imply two mechanisms. A progressive decline in trabecular thickness was noted in both groups versus controls. Trabecular perforations were not established in the group with BV/TV> 11% with the star volume or ICI, although some alterations were detected by trabecular bone pattern factor measurement. However, perforations were revealed in the group with BV/TV < 11% by all the different methods. Perforations seemed to occur when the trabecular thickness was below 70 mu m. This strongly suggests that bone histomorphometry should take into consideration bone volume in combination with detailed 3D descriptors of the trabecular architecture. Several histological methods need to be used in combination to appreciate the 3D architecture of trabecular bone.
Adrenal Cortex Hormones↗
Spontaneous multiple vertebral fractures revealed primary haemochromatosis.
The association of haemochromatosis and bone disease is well established, but osteoporotic fracture is an unusual presentation of the disease. We describe a male patient with osteoporotic fractures as a presenting feature of haemochromatosis. The bone histomorphometry showed a dramatic decrease in trabecular bone volume associated with a decrease in cortical bone thickness. Osteoblastic and osteoclastic activities were reduced without any sign of osteomalacia. Staining for iron with Perl's stain showed focal localization at the interface between mineralized trabecular bone and bone marrow. This observation leads us to review the possible mechanisms of osteoporosis.
Hemochromatosis↗
Recommendations for the registration of agents used in the prevention and treatment of glucocorticoid-induced osteoporosis.
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Animals↗
Osteoclast cytomorphometry in patients with femoral neck fracture.
In patients with femoral neck fracture, nutritional deficiencies have been shown to be common. A low calcium diet and/or a reduced vitamin D intake have been suspected to cause secondary hyperparathyroidism responsible for increased bone turn over and bone loss. Parathyroid hormone (PTH) levels are increased in these patients, data which are in accordance with the pronounced changes observed on bone biopsies reflecting a true hyperparathyroidism. We have used a cytomorphometrical approach to characterize PTH-induced changes on the osteoclastic population. Osteoclasts were detected histochemically (by tartrate resistant acid phosphatase staining) on bone biopsies from 10 control subjects, 8 patients with primary hyperparathyroidism and 10 patients with a femoral neck fracture of osteoporotic origin. The maximum Feret's diameter of each osteoclast (Oc.Le) was determined with a semiautomatic image analyzer. In all groups, the frequency distribution of Oc.Le appeared positively skewed. In both hip fractured patients and primary hyperparathyroid patients, the mode of the distribution was higher (25-30 microns) than in controls (20-25 microns). When graphically converted on a probability graph, the osteoclastic populations appeared homogeneous and well described by a lognormal distribution in the three groups. However, osteoclasts appeared similarly enlarged in the groups of patients with primary hyperparathyroidism and with femoral neck fracture. PTH has been shown to increase both the recruitment of mononucleated precursors and their fusion into larger osteoclasts than controls. In the present study, a cytomorphometric method appeared able to identify the border line hyperparathyroidism in the hip fractured patients.
Adult↗
Pharmacokinetics and pharmacodynamics of recombinant human erythropoietin in athletes. Blood sampling and doping control.
1. The pharmacokinetics of recombinant human erythropoietin (rHuEpo) were initially determined in two healthy volunteers after a single subcutaneous dose (50 u kg-1). Twenty subjects then received repeated subcutaneous administrations of high dose (200 u kg-1) rHuEpo and 10 subjects received placebo. An immunoradiometric assay was used to measure the concentrations of erythropoietin (Epo) in serum and urine. 2. Serum Epo concentration-time profiles were best described by a one-compartment open model with zero-order input. The mean elimination half-life (+/- s.d.) was 42.0 +/- 34.2 h. Clearance, uncorrected for bioavailability, was 0.05 +/- 0.011 h-1 kg-1. Erythropoietin concentrations returned to normal values in serum and urine, 7 and 4 days after the last administration, respectively. 3. The recombinant hormone was well tolerated. Significant changes in reticulocytes and red blood cells, haemoglobin concentrations and haematocrit were observed after administration of rHuEpo. In the control group, these parameters remained unchanged. 4. The change in reticulocytes was used as an index of the therapeutic effect of rHuEpo. The concentration-effect relationship was best described by an exponential model. 5. These data show the limitations of the measurement of Epo concentrations in blood and urine samples, collected in athletes during competition, for antidoping control. Epo doping can be detected only during or within 4 to 7 days of ending a course of rHuEpo.
Adult↗
Bacterial endocarditis revealed by infectious discitis.
A study of 30 patients admitted for infectious discitis identified four cases with concomitant bacterial endocarditis. All four patients were male and had concomitant streptococcal septicemia. Two patients had known aortic valve disease. The vertebral infection was located to the thoracic or lumbar spine. Ultrasonography disclosed aortic lesions in all four patients and mitral lesions in two. Management consisted of intravenous antimicrobial therapy for four weeks followed by a three-month course of oral antimicrobial therapy. The outcome of the discitis was favorable within the usual period of time. However, the endocardial lesions continued to progress, and three patients rapidly required valve replacement. Analysis of available data in the 30 patients with discitis showed that half the patients with streptococcal discitis also had bacterial endocarditis and that the latter condition developed in all the patients with streptococcal discitis and a history of valve disease. A number of risk factors were identified. An echocardiogram should be done routinely in patients with infectious discitis and risk factors for bacterial endocarditis.
Adult↗