Biomedical subjects

C Bergot

Publications and source records attributed to C Bergot.

29 records · Page 2Linked to original sources

PubMed1987

Different schedules of administration of (3 amino-1-hydroxypropylidene)-1, 1 bisphosphonate induce different changes in pig bone remodeling.

Intermittent administration of antiosteoclastic agents has been proposed in order to increase trabecular bone volume (TBV). We evaluated the effect of two different intermittent schedules of administration of (3 amino-1-hydroxypropylidene)-1, 1 bisphosphonate (AHPrBP) on pig bone remodeling for a period of 60 days. AHPrBP (1.6 mumol/kg/injection) was given subcutaneously daily (group A1), or 5 consecutive days out of 21 days (group A2), or 1 out of every fourth day (group A3). Compared to control animals, group A1 significantly increased trabecular bone volume (TBV) (+62%) with a marked decrease in bone resorption assessed by interstitial bone thickness. Bone formation assessed by mean wall thickness (MWT) was also decreased due to a decrease in the number and activity of osteoblasts. There was not a delay in the coupling mechanism as assessed by the reversal surfaces. The two groups receiving intermittent schedules had markedly different results. Group A2 had very similar changes to group A1 despite receiving four time less drug. Compared to group A1 and A2, group A3 had smaller decrease in resorption and higher bone formation rate with identical MWT. These differences between group A2 and A3 were associated with similar levels of parathyroid hormone and vitamin D metabolites. Different bone concentrations induced by the two different schedules of AHPrBP may explain the greater effect on bone resorption and osteoblast recruitment in group A2 and thus a milder effect of the AHPrBP administration once every fourth day.

Animals↗

PubMed1986

Influence of vertebral fat content on quantitative CT density.

Single- and dual-energy (85 and 130 kVp) computed tomographic (CT) measurements of bone density were made in 74 lumbar (L-3) vertebral specimens. Single-energy CT densities at 130 kVp consistently underestimated actual ash density by about 25 mg/cm3 in men and 40 mg/cm3 in women. CT densities overestimated age changes by 73% in women and 26% in men. These errors of the single-energy CT approach seemed due to increased marrow fat caused by age. At 130 kVp, there was a large decrease in apparent bone density (13 mg/cm3) for each increase of 100 mg/cm3 in fat content, but the decrease was lower at 85 kVp (11 mg/cm3), suggesting the use of lower energies for quantitative CT. In the vertebrae from the younger subjects (up to age 69), the relative error was 20%-31%, but in the oldest group it amounted to 31%-45%. The 95% confidence interval for an individual determination was +/- 38 mg/cm3. Dual-energy CT greatly reduced the above errors. Ash density was predicted with only a small accuracy error (7 mg/cm3) using a postprocessing dual-energy calculation, but the prediction error was 19 mg/cm3 for determinations at 130 kVp. The large uncertainty in the fat content of marrow (+/- 110 mg/cm3) and the variability in distribution of fat make dual-energy approaches necessary for accurate determinations of vertebral mineral density.

Absorptiometry, Photon↗

PubMed1985

Automatic quantification of vertebral cancellous bone remodeling during aging.

Anatomical transformation changes in vertebral spongy bone were quantified by automatic image analysis of microradiographs of 1 mm-thick sagittal slices from autopsied normal lumbar vertebrae (24 men and 28 women, age 35 to 96). Over a period of four decades, aging bone loss is 60% in women and 45% in men in the center of the vertebral body. With age, there is a new distribution of trabeculae: weight-bearing ones are twice (in young people) to six times (in old people) more numerous than transverse ones (measured on a sagittal slice). In the elderly, intertrabecular spaces enlarge while the proportion of the thinnest trabeculae increases.

Adult↗

PubMed1983

Cortical bone senescence and mineral bone density of the humerus.

Study of the humeral cortex of 89 acute cadavers showed that an important factor contributing to the physiologic bone loss of aging is increasing bone porosity. Mean cortical porosity increases in both sexes with age, from 4.6% in men and 4% in women at 40 years of age to 10% and more at age 80. In the population studied, no significant difference of porosity was observed between men and women. Apparent mineral density is linked to porosity, and decreases markedly with age in women. Changes in men are lesser in magnitude and show a larger difference of density values. Correction of the apparent mineral density, by a factor reflecting the proportion of vascular and resorption spaces in the cortical bone, produces a true mineral density which does not vary significantly with age in either sex. The density values obtained for the proximal humerus differ from those in the literature which represent the femur. However, they are more readily compared with the results of clinical densitometry and may have greater clinical applications.

Adult↗

PubMed1981

[Comparison of radiodensitometry and histomorphometry in normal and abnormal bone (author's transl)].

85 adults of both sexes, suffering from variety of bone disorders were studied by means of humeral radiodensitometry and histomorphometric analysis of iliac bone biopsies. Trabecular bone volume (TBV) was not related to cortical thickness. Bone mineral density was related to iliac TBV only in female subjects. The value of these measures is limited in osteoporosis because of measurement errors and skeletal inhomogeneity. In osteoporosis, variable histomorphometric features were observed. However, radiodensitometry proved a good measure of the state of mineralization in osteomalacia.

Absorptiometry, Photon↗

PubMed1978

[Critical study of variations in bone mass measurement by iliac biopsy].

Measurement of the bone trabicular volume (BTV) of 60 iliac crests obtained at necropsy, was done by morphometry on decalcified bone preparation. Changes in the site and the techniques of biopsy introduce variations which may reach 50% for sites which are one or two centimeters apart. The iliac bone is not especially imprecise and should be replaced by the transfixing horizontal biopsy. For a given zone, one observes a good correlation between the BTV and the ash weight per cubic centimeter of psongious bone, a point which justifies the interest in morphometry for the evaluation of the body bone mass.

Adult↗

PubMed1975

[Morphogenesis and structure of teleost teeth (Salmo fario L.)].

Tooth formation has been studied in the fry and adult trout (Salmo fario L.) in order to describe their structure and investigate the links between histogenetic and architectural features. Odontoblasts show typical polarized kinetics during their activity; they shrink back from the tooth wall they have elaborated, without leaving any cytoplasmic process (Tomes' fibres); so the dentine in a characteristic way lacks any cellular or canalicular inclusion, at any stage of its development. The tooth as a whole grows from an apical to basal direction; its organic matrix is formed of coarse fibres from the pulp, and fine collagenous fibres formed by the odontoblastic layer. These various fibrillar systems assume definite orientations. Mineralization was studied by fluorescent markers and microradiography. The external apical part of the tooth is hypermineralized, but its structure and pattern of deposition would make it closer to a dentinal differentiation (enameloid) than to an ectodermal enamel. The ameloblasts of the inner epithelium are high, very polarized and active cells, but their participation in tooth tissue formation has not been definitely demonstrated.

Ameloblasts↗

PubMedDate not supplied

A method of radio-frequency inhomogeneity correction for brain tissue segmentation in MRI.

An automatic method of correcting radio-frequency (RF) inhomogeneity in magnetic resonance images is presented. The method considers that image intensity variation due to radio-frequency inhomogeneity contains not only low frequency components, but also high frequency components. The variation is regarded as a multiplication of low frequency (capacity variation of coil) and the frequency of object (true image). The efficiency of the proposed method is illustrated with the aid of both phantom and physical images. The impact of the inhomogeneity correction on brain tissue segmentation is studied in detail. The results show significant improvement of the tissue segmentation after inhomogeneity correction.

Brain↗

PubMedDate not supplied

Effect of particle size on the tissue distribution of iodized emulsified fat following intravenous administration.

Three iodinated fat emulsions were tested by intravenous injection to rats: coarse with a mean size of particles of 7 micrometers, fine with a mean size of 1.3 micrometers, and ultrafine with a mean size of 0.7 micrometers. Iodine content analysis and scintigraphy of radioactive iodinated emulsions show important differences. Coarse emulsion is almost entirely fixed in the liver and the lungs; fine emulsion has a higher relative liver fixation; and ultrafine emulsion has a hepatosplenic fixation of short duration. Degradation of contrast medium is slow with coarse emulsion and very fast with ultrafine emulsion which is responsible for the rising iodine concentration in blood. Fine emulsion is a good compromise between excessive pulmonary fixation of coarse emulsion and high iodine peak in the blood after injections of ultrafine emulsion. The dose of 0.2 ml/kg of fine emulsion gives persistent enhancement of hepatic parenchyma without significant toxicity.

Animals↗

PubMedDate not supplied

[Quantitative vertebral x-ray computed tomography. Results in 105 women consulting for osteoporosis].

Quantitative vertebral CT scan imaging is a method developed to provide direct measurements of mineralization of vertebral body spongy tissue, and is presently the most precise procedure for the early detection of spinal osteoporosis. A fracture threshold has been defined below which are found 95% of patients with a crushed vertebra: it is situated at 70% of the value for mineralization normal for the age of patients. Patients with marked reductions in their level of mineralization can be kept under surveillance before the onset of fracture. In patients with vertebral collapses the density is correlated significantly with the number of crush fractures. In addition, measurement of vertebral spongy bone density has allowed the importance of the vertebral lesion to be determined in various osteoporotic disorders, including those with only cortical fractures, and in this way to differentiate them.

Adult↗

PubMedDate not supplied

[Contribution of medical imaging. What examinations for what indications?].

Osteoporosis is an obvious diagnosis in patients with fractures due to decreased bone mass. However, in many cases, major bone loss is infraclinical and requires quantification. Two methods are available to achieve this, i.e., dual energy X ray absorptiometry (DXA) and quantitative computerized tomography (QCT). QCT, which measures the central trabeculae in the lumbar vertebra, is a sensitive technique and has demonstrated a mean bone loss of 1.1 p. cent per year in cancellous bone. However, use of QCT is limited by the high radiation exposure and costs involved. Dual energy X ray absorptiometry is a highly reproducible method which ensures satisfactory correction of soft tissue effects and entails only low exposures to radiation. However, errors occur in patients with aortic calcifications, posteriorly located osteophytes or scoliosis. The optimal frequency of quantitative evaluations of bone varies with the type of disease; in patients with osteoporosis, it is unnecessary to perform evaluations more than once every three years to monitor the course of the disease.

Absorptiometry, Photon↗