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Biomedical subjects

O Louis

Publications and source records attributed to O Louis.

At least 19 recordsLinked to original sources
PubMed2001

[Cardiovascular rehabilitation].

In industrialized countries, coronary artery disease is the leading cause of mortality. Cardiovascular rehabilitation is one of the most important components of secondary prevention and is mainly prescribed after acute myocardial infarction or coronary artery revascularization. The aims of rehabilitation are not only the improvement of functional capacity but also the correction of risk factors and assistance to social and professional reintegration. There are numerous indications, including not only patients with coronary artery disease but also patients with heart failure and those who underwent cardiac surgery or heart transplantation. Cardiac rehabilitation consists in 3 successive stages. The first is performed during hospital stay. The two others take place in an approved center of multidisciplinary cardiac rehabilitation. The intensity of exercise is determined for each individual patient from the results of stress testing. The beneficial effects are well established: reduction in morbidity and mortality, improvement of quality of life and of pulmonary, cardiac, muscular and metabolic parameters. Its efficacy is only maximal when patients continue performing exercise regularly.

Coronary Disease↗
PubMed2000

Quantitative ultrasound of the calcaneus with parametric imaging: correlation with bone mineral density at different sites and with anthropometric data in menopausal women.

OBJECTIVE: To prospectively study the relationship of quantitative ultrasound of the calcaneus with anthromopometric variables and with bone mineral density (BMD) assessed at the level of the calcaneus as well as at other sites. METHOD: Osteosonography of the non-dominant calcaneus was performed in 135 menopausal women, using a DTU-one device with parametric imaging. Broadband ultrasound attenuation (BUA) and speed of sound (SOS) were assessed. BMD of the calcaneus (BMDcal) was measured using dual energy X-ray absorptiometry (DXA), in a subregion matched with the region of interest for osteosonography. BMD of the lumbar trabecular bone was measured using quantitative computed tomography (BMD QCT) while the non-dominant hip was studied using DXA, which provided the total bone mineral density (BMDhip) and that of the Ward triangle (BMDWard). RESULTS: The Pearson correlation coefficients between BUA, SOS and the various measurements of BMD ranged from 0.305 (SOS versus BMDhip) to 0.717 (BUA versus BMDcal). BMD QCT and BMDWard were found to depend on age, but not on weight or height, while BUA, SOS, BMDcal, BMDhip were unrelated to age, but correlated with weight (SOS, BMDhip) or with weight and height (BUA, BMDcal). In a multiple stepwise regression analysis, age was a significant predictor for BMD QCT, BMD hip and BMDWard; BMD QCT, BMDWard and BMDhip admitted BUA as sole predictor, while BMDcal was significantly related to both BUA and SOS. CONCLUSION: BUA and SOS of the calcaneus, assessed in 135 menopausal women using a parametric imaging device, reflected BMDcal, measured with DXA at a matched region of interest, and did not decline significantly with age.

Absorptiometry, Photon↗
PubMed2000

MR phase imaging to quantify bone volume fraction: computer simulations and in vivo measurements.

Magnetic resonance phase images can be used to assess trabecular bone by measuring the standard deviation of the phases in a region of interest. The standard deviation of regional phase measurements reflects the degree of magnetic field inhomogeneity caused by susceptibility differences between bone and marrow. A 3D computer model of trabecular bone was developed and then used to explore the influence of bone volume fraction and imaging parameters such as pixel size and slice width on the standard deviation of regional phase measurements. The results from these tests show that with appropriate selection of these parameters, phase spread strongly reflects variations in trabecular bone density (a correlation of R(2) = 0.98 with bone volume fraction between 0 and 10%). The technique was then applied in vivo on the radius of 25 patients who already had a bone density scan with peripheral quantitative tomography and a correlation between phase standard deviation and trabecular bone density was found (R(2) = 0.46).

Bone Density↗
PubMed2000

Quantitative ultrasound of the calcaneus: an in vivo comparison with dual-energy X-ray absorptiometry and magnetic resonance imaging.

The current study was performed in a clinical setting and aimed to evaluate the relationship between quantitative ultrasound (QUS) of the calcaneus with bone mineral density (BMD) assessed with dual-energy X-ray absorptiometry (DXA) and with variables derived from magnetic resonance imaging (MRI). Thirty-two postmenopausal women (mean age 61 years) were studied at the level of the nondominant calcaneus. QUS was performed using a DTU-one device including parametric imaging and yielded speed of sound (SOS) and broadband ultrasound attenuation (BUA) data. DXA was performed at a matched region of interest (ROI) in the calcaneus, using a Hologic QDR 4500 device. MRI, also performed at a matched ROI, yielded, using a Siemens Magnetom Vision device, the inverse of the transverse relaxation time (1/T(2)(*)) and the phase standard deviation (PSD). The strongest relationship between QUS and the other variables involved BUA and BMD (r &equals: 0.677, p < 0.001); 1/T(2)(*) showed a trend to correlation with SOS (r = 0.359, p = 0. 044) and with BMD (r = 0.364, p = 0.040), while the relationship between 1/T(2)(*) and BUA, PSD and BUA, PSD and SOS, PSD and BMD remained far from significance. Regression analysis of QUS, DXA, and MRI variables against age showed a trend to significant decline only for 1/T(2)(*) (r = -0.409, p = 0.020). In conclusion, this study shows that BUA of the calcaneus has the best correlation with BMD, and that, at least in a clinical setting, the ability of QUS to give information about bone structure is limited.

Absorptiometry, Photon↗
PubMed1999

Bone density reduction in various measurement sites in men and women with osteoporotic fractures of spine and hip: the European quantitation of osteoporosis study.

We have measured bone mineral density (BMD) using dual X-ray absorptiometry (DXA) of the spine and hip, spinal quantitative computed tomography (QCTspi), and peripheral radial quantitative computed tomography (pQCTrad) in 334 spine and 51 hip fracture patients. The standardized hip and spine BMD for each patient was calculated and compared with the combined reference ranges published previously, each densitometer having been cross-calibrated with the prototype European Spine Phantom (ESPp) or the European Forearm Phantom (EFP). Male and female fracture cases had similar BMD values after adjusting for body size, where appropriate. This suggests that the relationship between bone density (mass per unit volume) and fracture risk is similar between men and women. However, compared with age-matched controls, mean decreases in BMD ranged from 0.78 SD units (women with hip fracture, DXAspi) to 2.57 SD units (men with spine fractures, QCTspi). The proportion of spine and hip fracture patients falling below the cutoff for osteoporosis (T-score <-2.5 SD) proposed by the World Health Organization (WHO) study group varied according to different BMD measurement procedures (range 18-94%). This finding suggests that the WHO definition requires different thresholds when used with non-DXA BMD measurement techniques. Receiver operator characteristic (ROC) analysis was used to compare measurement techniques for their ability to discriminate between cases and controls. Among DXA sites, the proximal femur was preferred when evaluating generalized bone loss, particularly in elderly people. An additional spinal BMD measurement may add clinical value if spine fracture risk assessment has a high priority. Both axial and peripheral QCT techniques performed comparably to DXA in spinal osteoporosis, so investigators and clinicians may use any of the three technologies with similar degrees of confidence for the diagnosis of generalized or site-specific bone loss providing straightforward clinical guidelines are followed.

Absorptiometry, Photon↗
PubMed1998

Vertebral morphometric X-ray absorptiometry (MXA): relationship with bone mineral density in perimenopausal women.

OBJECTIVE: To evaluate the relationship between vertebral morphometry and vertebral bone mineral density (BMD) in a population of perimenopausal women. METHOD: We studied 120 healthy women (mean age (S.D.) 53.4 (8.3) years) referred for baseline bone densitometry around the menopause. Morphometric X-ray absorptiometry (MXA) was performed using a Hologic QDR 4500 A apparatus and assessed the anterior, mid and posterior heights of the third lumbar vertebra (L3). The anterior to posterior height ratio (AH/PH index) and the mid to posterior height ratio (MH/PH index) were calculated. Simultaneously, BMD of L3 was measured as antero-posterior dual energy X-ray BMD (AP-BMD DXA) and as lateral DXA BMD (L-BMD DXA). Subsequently, BMD of L3 was measured using single energy quantitative computed tomography, with a Siemens Somatom device (BMD QCT). RESULTS: The AH/PH index ranged from 0.840 to 1.150, with a mean of 0.995, the MH/PH index 0.880-0.980, with a mean of 0.937. The AH/PH index showed significant correlation with either L-BMD DXA (r = 0.54, P < 0.001) or BMD-QCT (r = 0.50, P < 0.001) but not with AP-BMD DXA (r = 0.05). Using an AH/PH index threshold of 0.97 we categorized the subjects into 42 women (group A) with an AH/PH index < 0.97 and 78 women (group B) with an AH/PH index greater than or equal to 0.97. BMD values were found to be lower in group A than in group B. The difference was not significant with AP-BMD DXA (1011.5 (155.7)) versus 988.5 (193.5) mg/cm2, P = 0.47) but reached high significance (P < 0.0001) with L-BMD DXA (797.2 (166.8) versus 462.9 (131.1) mg/cm2) and with BMD QCT (135.5 (24.8) versus 83.6 (18.3) mg/cm3). CONCLUSIONS: These results suggest that the AH/PH index of L3, assessed using MXA, shows some degree of correlation with BMD in perimenopausal women.

Absorptiometry, Photon↗
PubMed1998

Reproducibility of phalanx osteosonography and relation with forearm peripheral quantitative computed tomography: single finger versus average measurement on the last four fingers.

The aim of this study was to evaluate the in vivo short-term reproducibility of amplitude-dependent speed of sound (AD-SOS) measured at the proximal phalanx, using an Igea DBM Sonic 1200 device, as well as its relationship with bone mineral density of the ultradistal radius, assessed using peripheral quantitative computed tomography (pQCT). In particular, the authors wished to evaluate whether average measurements on the last four fingers, as recommended by the manufacturer, yielded or not more information than measurements on one single finger. For the precision study, the authors carried out phalanx osteosonography ten times once every other day in ten healthy young women. To compare with pQCT of the radius, 37 women referred for screening of osteoporosis (mean age 60 years) were studied. AD-SOS was reported for each finger separately, as well as an average; pQCT (XCT 960 Stratec) yielded trabecular (BMDt); cortical (BMDc); and total (BMDtot) bone mineral densities, as well as the cortical area (Ac). The reproducibility of AD-SOS was significantly higher for the middle finger (mean coefficient of variation (CV) 1.1%) and the index than for the ring and small (mean CV 2.7%) finger. The middle finger consistently showed the best correlations with pQCT variables; the relationships involving BMDc (r = 0.54), BMDtot (r = 0.62) and Ac (r = 0.61) were stronger than that with BMDt (r = 0.34). The authors conclude that phalanx AD-SOS is moderately correlated with BMD of the ultradistal radius--at least when it includes the cortical component--and that reporting AD-SOS for the middle finger--instead of an average value--improves the reproducibility and possibly the relevance of phalanx osteosonography.

Adult↗
PubMed1998

Cafeteria diet-induced obesity is associated with a low spontaneous growth hormone secretion and normal plasma insulin-like growth factor-I concentrations.

Pituitary growth hormone (GH) secretion has been shown to be blunted in human and animal obesity. With respect to human obesity, cafeteria diet-induced obesity might be an appropriate model to study spontaneous GH secretion. In 6 cafeteria diet-overfed obese male Wistar rats and 6 control rats with chronically implanted catheters, GH levels were measured every 15 min over 6 h by standard RIA. A significantly lower GH secretion, reflected by the integrated GH concentration, was found in the obese rats (median 16.46, [range 10.55-19.13] ng/ml x 6 h vs 35.63 [range 21.90-41.50] ng/ml x 6 h, P < 0.05). The GH secretion in the obese rats was significantly negatively correlated with the body fat percentage, assessed by dual X-ray absorptiometry (Rho = -0.95, P < 0.05). Median plasma insulin-like growth factor-I (IGF-I) concentration was comparable between the two groups, while the median insulin concentration was significantly higher in the obese group (1.95 [range 1.76-3.55] ng/ml vs 1.21 [range 0.86-2.13] ng/ml, P < 0.05). No significant correlation existed between GH secretion and the plasma insulin concentration. In conclusion, cafeteria diet-induced obesity is associated with a low spontaneous GH secretion and normal plasma IGF-I concentration. The hyperinsulinemia present in this model probably explains the normal IGF-I concentrations, but not the GH hyposecretion.

Animals↗
PubMed1998

Lumbar spine bone mineral density in diabetic children with recent onset.

To detect early abnormalities in bone mineralization, the lumbar spine bone mineral density (BMD) of diabetic children with a diabetes onset of less than 5 years and treated with a similar insulin treatment scheme was measured at the level of the lumbar spine by dual-energy X-ray absorptiometry (DEXA), a most sensitive technique for detecting osteopenia in children. Fifteen male and 8 female children and adolescents (mean age +/- SD: 12.5+/-3.7 years), 1-5 years after the clinical onset of their diabetes, were studied. Measurements of the lumbar spine (L1-L4) BMD, expressed in gHA/cm2 and as a z-score for age, were performed with a commercial DEXA apparatus (Hologic QDR 1000 W, Hologic Inc., Waltham, USA). Calcium-phosphorus metabolism was studied by measuring the circulating levels of calcium, phosphorus, alkaline phosphatase, osteocalcin, 25-OH-vitamin D and parathyroid hormone and the urinary excretion of calcium and phosphorus. The mean BMD of the studied group was 0.75 (0.16) gHA/cm2 giving a mean z-score of -0.31+/-0.95. Only 1 of the patients had a BMD lower than -2 SD. No sex difference in BMD z-score existed. BMD SD was positively correlated with height SD (R = 0.56, p < 0.005), but not with the age of the patients, the duration of the disease, the degree of metabolic control or the studied parameters of the calcium-phosphorus metabolism. In conclusion, diabetic children have a normal lumbar spine BMD during the first years of the disease, when a good metabolic control and no abnormalities in the calcium-phosphorus metabolism are present. As in normal children, areal BMD by DEXA is highly dependent on the body height, necessitating corrections if abnormalities in skeletal growth or pubertal development exist.

Absorptiometry, Photon↗
PubMed1998

Study of serum leptin in cafeteria-diet-overfed rats. Influence of diet, insulin and corticosterone.

In a group of 15 male Wistar rats overfed with cafeteria foods (delivering a mean fat percentage of 60%) during 5 months from the age of 8 weeks and in a control group of 15 rats fed with a standard chow for the same period, serum leptin, insulin and corticosterone were measured by RIA and body composition was determined by dual-energy X-ray absorptiometry. Significantly higher fasting serum concentrations of leptin, insulin and corticosterone were found in the cafeteria-diet group. Fasting leptin concentrations were significantly higher in rats with a body fat percentage of more than 25% compared to the others, irrespective of the type of feeding. The log serum leptin correlated positively with body fat percentage and fasting insulin concentration but not with corticosterone concentration. Leptin concentration corrected for body fat mass was, however, comparable between the two diet groups, while the leptin/insulin ratio was lower in the cafeteria-diet group. In conclusion, chronic overfeeding resulting in an increased body fat percentage in rats is associated with hyperleptinemia, hyperinsulinemia and hypercorticism. Serum leptin levels appear to primarily track total body fat percentage and are unaffected by dietary fat manipulation in cafeteria-diet-induced obese rats.

Absorptiometry, Photon↗
PubMed1997

The weight gain and ultimate adiposity in cafeteria diet-induced obesity is unrelated to the central serotoninergic tonus.

Early detection of subjects with a propensity to obesity might be of great help for setting up preventive intervention studies. In this study we tested whether the development of obesity in Wistar rats, given ad libitum cafeteria foods, could be predicted by a low prolactin (PRL) response to 5-hydroxytryptophan (5HTP), as an index of low hypothalamic serotoninergic tonus. Basal and 5HTP-stimulated (50 mg/kg body weight i.p.) PRL were measured by RIA in 15 young male Wistar rats, whose pelleted diet was afterwards supplemented with cafeteria foods. In the tested animals an increase of PRL between 4 and 56 times the basal value was observed 60 min after the 5HTP injection. After 2 months of feeding, marked inter-individual differences in weight gain between the cafeteria fed animals were observed. After 10 months of feeding, median body fat percentage, assessed by dual X-ray absorptiometry, of the overfed rats was significantly higher than that of control animals: median (range): 41.2% (28.9 - 51.5%) vs 25.1 (18.0 - 32.2%) (p < 0.0001). The PRL response at the start of the experiment was neither correlated with the monthly weight increases, nor with the fat mass percentage at the end of the experiment, suggesting that a pre-existing low hypothalamic serotoninergic tonus is probably not involved in the overeating and ultimate overweight of cafeteria diet fed animals.

Adipose Tissue↗
PubMed1996

Cortical and total bone mineral content of the radius: accuracy of peripheral computed tomography.

The aim of the study was to evaluate the accuracy of an XCT 960 Stratec peripheral quantitative computed tomography (pQCT) device in assessing bone mineral content of the radius. We scanned 27 left forearm specimens excised from cadavers and focused on cortical bone mineral content (BMCc) at the junction of the middle and distal third and on total bone mineral content (BMCtot) at the distal end of the radius. Cylindrical specimens matched with those two sites were cut using a diamond circular saw, embedded in a polyester resin and subsequently submitted to two reference methods, nondestructive neutron activation analysis and flame atomic absorption spectrometry. Mineral contents measured by pQCT were closely correlated with those assessed by using the two reference methods, with correlation coefficients ranging from 0.862 to 0.960. The standard error of the estimate amounted 7-10% for the BMCc (junction of the middle and distal third), and 17-18% for the BMCtot (distal end). We conclude that pQCT is able to measure either cortical or total mineral content of the radius with a high degree of accuracy.

Aged↗
PubMed1995

Cortical thickness assessed by peripheral quantitative computed tomography: accuracy evaluated on radius specimens.

The purpose of the present study was to evaluate the accuracy of peripheral quantitative computed tomography (pQCT) in measuring the thickness of the radial cortex. Thirty left forearm specimens were scanned on an XCT 960 Stratec pQCT device using a 2.5 mm thick slice at the junction of the middle and the distal third of the radius. Cortical and trabecular areas were assessed using a threshold procedure; cortical thickness was subsequently calculated assuming a circular ring model for the radius. Cortical thickness was also measured on the true shape of bone using an iterative contour detection procedure. Subsequently 2.5 mm thick resin-embedded cylindrical radial specimens, matched with the site of pQCT examination, were obtained and contact radiographs were performed. After tenfold magnification, the cortical and trabecular areas of the specimens were measured using computerized planimetry and cortical thickness was calculated assuming a circular ring model. The cortical thickness could be assessed by pQCT in all cases using the threshold algorithm (mean (SD) 2.51 (0.58) mm) and in 21 cases could be directly measured on the true shape of bone (2.62 (0.32) mm). The cortical thickness of the specimens showed good correlation and high proportionality with that measured using pQCT with either the threshold algorithm (r = 0.941, slope = 0.976) or the iterative contour detection procedure (r = 0.883, slope = 0.987). In conclusion, pQCT is able to assess the thickness of the radial cortex, at the junction of the middle and the distal third, with high accuracy.

Aged↗
PubMed1995

Cortical mineral content of the radius assessed by peripheral QCT predicts compressive strength on biomechanical testing.

Our aim was to evaluate the role of cortical bone in resistance to compression in the human radius. Thirty-three left cadaver forearms were scanned on an XCT 960 Stratec CT scanner. Cortical density and cortical thickness were measured at the junction of the middle and distal third of the radius. Subsequently, 2-cm-high cylindrical specimens, centrated on the level of the CT slice, were cut. After removal of the endosteal trabecular bone, the specimens were submitted to compressive testing, using an Instron machine, and load deformation curves were obtained. Maximal stress (load corrected for cross-sectional area) showed a significant relationship with the density (r = 0.78) as well as with the thickness (r = 0.74) of the cortex. The closest correlation involved the maximal load and the mineral content of the cortex specimens (r = 0.87). We conclude that the mineral content of these radius cortex specimens, measured using peripheral QCT, predicts their compressive strength on biomechanical testing.

Aged↗
PubMed1995

Effect of treatment with 1.25 and 1.75 mmol/l calcium dialysate on bone mineral density in haemodialysis patients.

The effect of two different dialysate solutions with a calcium concentration of 1.25 and 1.75 mmol/l was evaluated in 14 patients, using a cross-over design. Patients were treated with each solution during a period of 6 months. Treatment with calcium supplements, vitamin D and aluminium hydroxide was adapted weekly, according to the results of blood chemistry. PTH, SAP, and ionized calcium were determined monthly, bone density with DXA and QCT before and after 6 months of treatment. During treatment with both 1.25 and 1.75 calcium dialysate (cad), the control of serum calcium and phosphate was similar. PTH did not change during either treatment. SAP decreased during treatment with 1.75, but remained stable with 1.25 mmol/l cad. Bone density evaluated with DXA remained unchanged during both treatments. QCT measured bone density increased from 101.29 +/- 13.50 to 106.79 +/- 13.14 mg/ml in the 1.75 cad group, while it did not vary in the 1.25 cad group, (107.75 +/- 13.48 versus 108.97 +/- 13.40 mg/ml). It is concluded that lowering the calcium content of the dialysate does not negatively influence the control of serum calcium and phosphate, nor does it aggravate hyperparathyroidism when vitamin D is administered simultaneously. Under the present conditions, osteopenia and possibly bone mineralization improve only in the group dialysed with 1.75 Ca.

Adult↗
PubMed1995

[Spontaneous rupture of an unscarred uterus during labor and epidural anesthesia].

We report a case of spontaneous rupture of unscarred uterus, during labour and under epidural analgesia in a 43 year-old patient at her third pregnancy and third delivery. The tear was vertical and took place on the left postero-lateral side of the uterus, occurring in the whole height of the lower segment and overlapping towards the uterine corpus and cervix. Analysis of medical, surgical, gynaecological and obstetrical past history has displayed no predisposing factors explaining this rare occurrence. This clinical case reminds us that spontaneous rupture is always possible even on an unscarred uterus.

Adult↗