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Biomedical subjects

C Alexandre

Publications and source records attributed to C Alexandre.

At least 91 records · Page 5Linked to original sources
PubMed1995

Atypical osteomalacia after 2 year etidronate intermittent cyclic administration in osteoporosis.

A 68-year-old postmenopausal woman with osteoporosis received intermittent cyclic etidronate therapy (400 mg/day). No concomitant diseases were noted. A baseline transiliac bone biopsy showed a high bone turnover without impairment due to mineralization. After 2 years of treatment, she had increased osteoid volume, and mineralization lag time corresponded to a variant form of osteomalacia called atypical osteomalacia. No clinical consequence was observed. This is the first case report of such a mineralization defect due to 2 year intermittent cyclic etidronate therapy.

Aged↗
PubMed1994

Adverse effects of strenuous exercise: a densitometric and histomorphometric study in the rat.

To investigate the manner in which cancellous bone in different skeletal sites and within a bone site adapts to strenuous training, 5-wk-old male rats were subjected to intensive treadmill running [80% of maximal O2 consumption (VO2max)] for 11 wk. VO2max, tibia length, and bone mineral density were measured. Histomorphometric analysis was performed in the epiphysis, primary spongiosa (1 zero sp) and secondary spongiosa (2 zero sp) of the contralateral proximal tibia, and the 2 zero sp of thoracic and lumbar vertebrae. VO2max was increased by 39%. No changes were observed in vertebrae. Tibia length, 1 zero sp bone volume, and number of trabeculae were significantly decreased, indicating a retarded longitudinal bone growth. Bone mineral density in the proximal tibia was significantly decreased. In the epiphysis, a trabecular thinning and an increase of trabecular number were shown. In the 2 zero sp, bone volume and number of trabeculae were significantly decreased. The increased total eroded surfaces could indicate an early but transient increase in bone resorption activity. Osteoid thickness was reduced, whereas osteoclast number and osteoid surfaces were unchanged, suggesting that the observed bone loss was mostly due to an impaired osteoblastic activity. In conclusion, 1) strenuous training in young rats reduces longitudinal bone growth and induces bone loss, 2) the cancellous bone adaptation is site specific, and 3) the bone loss is mainly due to decreased osteoblastic activity rather than a global adaptation of bone remodeling.

Animals↗
PubMed1994

Colorimetric evaluation of cultured osteoblast-like cells (ROS 17/2.8).

We have developed a colorimetric method for evaluating the number of osteoblastic cells in culture without destroying the cells. This assay is based on the staining of basophilic cellular compounds with methylene blue. The dye bound by the cells is released at low pH and measured in a spectrophotometer at 662 nm. Linear correlations exist between the absorbance measured by the methylene blue assay and the number of cells seeded, the total cellular protein content, and thymidine labeling. This colorimetric method has the advantage of preserving cell integrity. After destaining, scanning electron microscopy can be performed on well preserved cell morphology.

Animals↗
PubMed1994

[Functional ability and quality of life in rheumatoid arthritis: use of the Functional Independence Measure and the Reintegration to Normal Living Index].

Functional disability and quality of life were evaluated using the Functional Independence Measure and the Reintegration to Normal Living Index, respectively, in 57 subjects (15 men and 42 women) with a mean disease duration of 15 years. Scores on both these nonspecific scales correlated with those obtained using instruments specifically designed for rheumatoid arthritis (ARA index, Lee index) and with a number of clinical parameters including patient age, disease duration and number of affected joints. Functional ability was correlated with quality of life in this study and in others performed using other evaluation tools. Nonspecific assessment scales are useful for comparing function and quality of life in various diseases.

Activities of Daily Living↗
PubMed1994

[Integrins].

Explore the source record for details and available documents.

Bone Remodeling↗
PubMed1993

Possible nonlinear effects of exercise on bone in male subjects over age 60 years.

We investigated the relationships among bone mass, bone cell activities, and exercise level in 20 healthy 61-77 year old male volunteers divided into three groups according to the time they physically trained per week: nine subjects training less than 3 hr/week, five subjects between 3 and 6 hr/week and six subjects more than 6 hr/week. Physical performance was evaluated by VO2 max (ml min-1 kg-1). After tetracycline double labeling, iliac crest biopsy was obtained from each subject. The longer the physical activity, the higher the VO2 max. Subjects exercising between 3 and 6 hr/week revealed higher adjusted appositional and bone formation rates than all the others; mass and structural parameters also showed higher (nonsignificant) values. For the whole population VO2 max appeared negatively related to cortical thickness, cancellous bone volume, and trabecular thickness. These alterations were accompanied by increased cancellous bone turnover; this was evidenced by an increase in activation frequency and in resorption and formation rates as VO2 max increased. The bone remodeling periods tended to decrease also. Whatever the bone turnover rate, subjects were in steady state as far as their bone balance was concerned. Relationships between VO2 max and mineral apposition rate on the one hand and VO2 max and resorption surface on the other hand were best fitted by a quadratic model, suggesting a possible nonlinear effect of physical training on bone mass. We hypothesize that there is a threshold (6 hr/week) determining different effects. Adjustment of bone mass and trabecular arrangement were completed at time of biopsy and reflected probably past and transient bone imbalance.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

[Thrombotic thrombocytopenic purpura and ankylosing spondylarthritis. Apropos of a case].

The authors report a case of thrombotic thrombocytopenic purpura (TTP) which revealed a hitherto unrecognized ankylosing spondylitis. After a 4-year follow-up, the spondylitis is still progressing in its axial and/or peripheral form, and TTP has not relapsed. TTP is usually primary, but numerous forms consecutive to various diseases, and notably autoimmune diseases, have been reported. The TTP-ankylosing spondylitis association is extremely rare: analysis of the literature yielded only one case. The authors discuss the hypothesis of a common triggering factor.

Adult↗
PubMed1993

Histomorphometric analyses of cancellous bone from COSMOS 2044 rats.

The influence of 14 days of spaceflight on cancellous bone of male Wistar rats was assessed by histomorphometric analysis. In proximal tibia, no difference was found between flight, synchronous, vivarium, and basal groups for epiphyseal bone volume or trabecular arrangement. In metaphysis, primary spongiosa width was reduced in flight rats, suggesting an alteration in bone longitudinal growth. In flight rats, secondary spongiosa evidenced a trend toward decreased bone mass, trabecular number and thickness, and osteoid surfaces, whereas there was a tendency toward increased osteoclast number compared with vivarium control but not with synchronous rats. In femoral fossa trochanteri, an area facing deep muscular insertions, no changes in bone volume or structure were noted among the different groups. However, a reduction of osteoid surfaces was seen in flight and synchronous groups compared with the other groups. Resorption activity was increased in flight rats compared with control rats. In thoracic vertebral body, osteoblastic surfaces decreased similarly in flight and synchronous rats. In lumbar vertebral body, decreased osteoblastic surfaces and increased osteoclastic parameters were observed in flight and synchronous rats. The more striking effects of spaceflight were the decrease in tibial primary spongiosa width and the increase in resorption activity of the femoral fossa trochanteri. In all other sites, cellular alterations appeared similar in flight and synchronous rats, suggesting a role for physiological stress. The time course of events would depend on initial growth and turnover rates of bone, its weight-bearing function on earth, and the presence of muscular insertions.

Animals↗
PubMed1993

[Tobacco as risk factor of osteoporosis, myth or reality?].

To evaluate smoking as a risk factor for osteoporosis, we performed a qualitative analysis of 40 international studies investigating statistical associations between smoking and osteoporosis related endpoints. Using standardized causality assessment criteria, we failed to demonstrate a relationship between smoking and osteoporosis. Because such a relationship is biologically plausible, we then undertook a quantitative metaanalysis of 8 epidemiological hip fracture studies. Relative risk, estimated as the "combined odds ratio", was 1.33 (95% confidence interval 1.14-1.54) in the case-control studies and 1.63 (95% confidence interval 1.27-2.09) in the prospective studies. These data suggest that smoking is a modest risk factor for osteoporosis. However, studies of effects of smoking on peak bone mass would be of interest in view of the prevalence shift of smoking towards increasingly young age groups. Early exposure to smoke may decrease peak bone mass. Furthermore, Kiel recently found evidence that replacement hormone therapy may be ineffective in preventing hip fractures in postmenopausal women who smoke. Reducing smoking is an important goal for the primary and secondary prevention of osteoporosis in teenagers and postmenopausal women, respectively.

Adolescent↗
PubMed1992

Human and Drosophila homeodomain proteins that enhance the DNA-binding activity of serum response factor.

Cells with distinct developmental histories can respond differentially to identical signals, suggesting that signals are interpreted in a fashion that reflects a cell's identity. How this might occur is suggested by the observation that proteins of the homeodomain family, including a newly identified human protein, enhance the DNA-binding activity of serum response factor, a protein required for the induction of genes by growth and differentiation factors. Interaction with proteins of the serum response factor family may allow homeodomain proteins to specify the transcriptional response to inductive signals. Moreover, because the ability to enhance the binding of serum response factor to DNA residues within the homeodomain but is independent of homeodomain DNA-binding activity, this additional activity of the homeodomain may account for some of specificity of action of homeodomain proteins in development.

Amino Acid Sequence↗
PubMed1992

Microgravity and bone adaptation at the tissue level.

Our knowledge of the adaptation of human bone microgravity remains poor despite long-term Russian spaceflights and the recent use of accurate techniques for bone mass measurements. The extent of bone deficits in the adaptation of the whole skeleton is not clear. At the tissue level, bone resorption and formation activities have been studied only in bones from rats after spaceflights lasting a few days to 3 weeks. In these animals, architectural features consistent with osteoporosis have been found in the proximal tibia. In pregnant animals the osteoclast population is increased at other skeletal sites. In areas of weight-bearing bones that are not protected by muscular insertions, bone resorption is not markedly altered after 7 days of spaceflight and bone formation is reduced. In areas of weight-bearing bones with muscular insertions and in non-weight-bearing bones, similar changes in bone cell activity are delayed. The severity of the response seems to vary with the location of the bone in the skeleton and its initial level of bone turnover. After 12.5 days the acute bone changes are less and no additional changes are observed after 21 days in space. We conclude that generalized bone deficits do not appear to be a consequence of microgravity but occur in localized areas according to the level of modeling and remodeling and of the support function of each bone at 1 g.

Adaptation, Physiological↗
PubMed1992

Bone mass and bone cellular variations after five months of physical training in rhesus monkeys: histomorphometric study.

Five Rhesus Monkeys (Macaca mulatta), a suitable nonhuman model, performed 5 months of rope-climbing exercise. Duration of the training sessions was progressively increased to reach 1 hour/day after 1 month of training and was maintained until the end of the experiment. Bone mass parameters, bone resorption, and bone formation activity were measured by histomorphometric analysis on iliac crest bone biopsies before and after the experiment. Mineral apposition rate was measured in cortices and trabecular bone after double calcein labeling. Five months of rope-climbing exercise had determined a significant decrease of bone volume with a slight decrease of the number and thickness of trabeculae. This might induce an alteration of biomechanical properties of bone. These architectural modifications were associated with a nonsignificant decrease of bone resorption activity. But the main effect of training was an important decrease of bone formation activity without change of the mineral apposition rate. Endurance exercise at low intensity has determined a decreased bone turnover with osteoblastic depression. This animal experiment points out that exercise modalities might be important in the bone response to training and should be carefully defined for preventive use in humans.

Animals↗