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Biomedical subjects

I Leichter

Publications and source records attributed to I Leichter.

At least 37 records · Page 2Linked to original sources
PubMed1989

The effect of swimming activity on bone architecture in growing rats.

The effect of non-habitual physical activity on bone architecture in the rat humeral shaft was examined. Two groups of rats were trained to swim for 1 h a day, for 20 weeks, at two training levels. The control group consisted of sedentary rats. Parameters of cross-sectional bone morphology (cross-section areas, principal area moments of inertia and their ratio) were used to evaluate the response of bone architecture to mechanical loading. The strength of bone was assessed by measuring the ultimate compressive force and stress. The cortical cross-section area and principal moments of inertia were found to be significantly higher in the swimming groups than in the controls. Examination of the ratio between the major and minor moments of inertia revealed a pronounced change in the shape of the bone cross-section which became more rounded following swimming training. The ultimate compressive force was significantly higher in the swimming rats while the changes in ultimate stress were not significant. Our results indicate a gain of bone strength due to increased periosteal apposition and modified bone tissue distribution. The marked changes in bone morphology are attributed to the different nature of the forces and moments exerted on the humerus during swimming compared to those prevailing during normal locomotion.

Adaptation, Physiological↗
PubMed1989

Effect of swimming on bone growth and development in young rats.

The effect of chronic swimming on bone modelling was studied. Forty female Sabra rats (5 weeks old) were randomly assigned to the following experimental groups: 30 rats were trained to swim (water bath 35 +/- 1 degree C, one h daily, five times a week) for 20 weeks--20 of them loaded with lead weights (1% body weight) while the rest (10 animals) swam load free. Ten sedentary rats matched for age and weight served as controls. At the end of the twenty-week swimming period, all rats were sacrificed, both humeri bones were dissected and prepared for the following examinations: morphometric, bone density (BD), bone mineral content (BMC), compression tests and cross-sectional geometrical parameters, histomorphometry and biochemical analysis of minerals (Ca, Pi, Mg, Zn). All measured parameters were found to be significantly higher (P less than 0.05) in the swimming rats irrespective of load, as compared with the controls. Bone weight was higher by 19%, bone volume by 11%, bone length by 2.8%, cortical area by 16%, BD by 7% and BMC by 15%. The compression breaking force at the distal shaft of the humerus was higher by 24% in the trained group, while the ultimate compressive stress was not significantly different. Maximal and minimal moment of inertia at the distal diaphysis were 33.4 and 40% higher, respectively, for the swimming groups than the controls. Ca, Pi, Mg and Zn levels per total humeral bone were significantly higher in the exercising rats. The histomorphometry and cross-sectional data emphasize longitudinal and transversal growth. These data indicate that swimming exercise exerts a positive effect on bone growth and development in young rats.

Animals↗
PubMed1989

Combined effect of foot arch structure and an orthotic device on stress fractures.

In a prospective study, quantitative measures of the structure of the longitudinal arch of the foot were established and related to the incidence of stress fractures in the bones of the lower limbs of military recruits. In addition, the role of a semirigid orthotic device (Langer military stress orthotic) in preventing stress fractures was evaluated as a function of the structure of the longitudinal arch. Femoral and tibial stress fractures were found to be more prevalent in the presence of feet with high arches, whereas the incidence of metatarsal fractures was higher in feet with low arches. The use of an orthotic device reduced the incidence of femoral stress fractures only in the presence of feet with high arches and the incidence of metatarsal fractures only among feet with low arches. The findings suggest that the normal foot with a low arch acts as a better shock absorber than the normal foot with a high arch, and that an orthotic device may improve the shock absorbing capacity of the arch.

Adult↗
PubMed1989

Structural and compositional changes in aging bone: osteopenia in lumbar vertebrae of Wistar female rats.

Changes in vertebral bone mineral content and density during aging were quantified in female Wistar rats. This study represents a longitudinal follow up utilizing single photon absorptiometry for the measurement of bone mineral content (BMC), quantitative computed tomography (QCT) for the measurement of bone mineral density (BMD), and image analysis histomorphometry for the measurement of trabecular bone volume (TBV) and bone cortical area (BCA). The above measurements were accompanied by biochemical assays of calcium concentrations in the respective bones. All aging animals experienced significant decreases in BMC, BMD, TBV, BCA and in the calcium content of their bones. The above features have been further emphasized through the use of scanning electron micrographs showing the age-related structural changes in a three-dimensional fashion. New, advanced technologies will enable the quantitation of 3-dimensional images that are currently obtained from the scanning electron micrograph; thus will provide new consideration as related to trabecular bone compactness (density). Energy dispersive x-ray spectroscopy indicated that the nature of crystals in aging bones does not differ markedly from that encountered in young specimens. Data are also provided with regard to the health of the animals, and it became apparent that aging rats undergo changes in their kidneys yet do not show any significant change in renal functional parameters as measured in both the serum and the urine. Hence, new noninvasive methodologies are currently available for longitudinal studies related to the skeleton in laboratory animals enabling reliable monitoring of age-related and hormonally induced changes in bones (spine and hip) of well defined experimental models.

Absorptiometry, Photon↗
PubMed1988

Ability of different techniques of measuring bone mass to determine vertebral bone loss in aging female rats.

Changes in vertebral trabecular bone were quantified in female Wistar rats. This study utilized single photon absorptiometry for the measurement of bone mineral content (BMC), quantitative computed tomography (QCT) for the measurement of bone mineral density (BMD), and image analysis histomorphometry for the measurement of trabecular bone volume (TBV). The above measurements were accompanied by biochemical assays of protein and calcium concentrations in the tissues. Also, the activity of bone alkaline and acid phosphatases was measured. Lumbar vertebrae (L4, L5) in old rats 27 months old, compared with those of young rats 7 months old, showed significant decreases in BMC, BMD, TBV, protein and calcium, and enzyme activity. A high degree of correlation was recorded between the above changes. The various changes were accompanied by a marked reduction in the overall wet weight of the vertebrae. Hence, new noninvasive methods to quantitate bone mass can be applied in vivo to small laboratory animals such as the rat. These methods are much more accurate than standard radiographs in quantitating bone loss and are, therefore, recommended for experimental longitudinal studies related to aging of the skeleton.

Acid Phosphatase↗
PubMed1987

Increased trabecular bone density due to bone-loading exercises in postmenopausal osteoporotic women.

A program of diverse and dynamic loading exercises of the distal forearm, a common site of osteoporotic fractures, was applied three times a week for 5 months to 14 postmenopausal osteoporotic women. Two parameters were used to assess the effect of the exercises on bone mass. The mass density of bone (g/cm3) was measured by the Compton scattering technique. The bone mineral content (g/cm2) was measured by single photon absorptiometry. Both measurements were taken at the same location in the distal radius 1 year prior to the exercise period, at its beginning, and at its end, in both the exercised group and a matched control group of 26 osteoporotic women. During the exercise period the mean bone density decreased by 1.9% in the control group whereas it increased by 3.8% in the exercise group. The bone mineral content results did not demonstrate any significant trend over the whole period of the study. It is concluded that the trabecular bone tissue in the distal radius of postmenopausal osteoporotic women responds favorably to dynamic and diverse bone stressing exercises even in the seventh decade of life.

Adipose Tissue↗
PubMed1987

The relative significance of trabecular and cortical bone density as a diagnostic index for osteoporosis.

The density of the distal radius in the non-dominant forearm was measured non-invasively by Compton spectrometry in 234 post-menopausal women. The density of the trabecular tissue was determined almost independently from that of cortical tissue by horizontal and vertical scanning of the bone. It was found that the lower the density of the trabecular bone, the greater the difference between the density of the cortical and trabecular bone. As osteoporosis progresses, trabecular bone density in the distal radius seems to decrease faster than that of compact bone. Hence the severity of the disease is best determined by measuring the density of trabecular bone.

Adult↗
PubMed1987

Dynamic bone loading exercises for postmenopausal women: effect on the density of the distal radius.

A set of dynamic bone loading exercises for the distal forearm, designed for high rates of loading, within physiologic range, and diversity of strain regime, was applied to a group of postmenopausal osteoporotic women. The effect of five months of three weekly sessions, 50 minutes each, on the bone status was studied by measuring the bone density at the distal radius by the Compton scattering technique. A group of 14 women who participated in the program and an inactive group of 26 women were examined one year prior to the study, at its beginning and at its end. During the year preceding the exercise program the mean bone density in both groups decreased significantly. During the exercise period the bone density of the exercise group increased by 3.8% while that of the control group continued to decline. This study demonstrates that an appropriate physical activity regime may be effective as a prophylactic treatment for postmenopausal bone loss.

Absorptiometry, Photon↗
PubMed1986

A correlative assessment of photon interaction and histomorphometric measurements of bone density.

Thirty-four femoral necks from human cadavers were measured by techniques assessing bone density and bone mineral density, and by the Singh index. These methods are based on photon interaction with biological components and can be applied noninvasively for clinical evaluation of changes in skeletal status. Trabecular bone volume, mineralized bone volume, and relative osteoid volume were evaluated histomorphometrically using undecalcified histologic sections obtained from the same samples. The trabecular and mineralized bone volumes showed significant correlations with the bone density and mineral density. These results enhance the validity of recently developed photon-interaction techniques for evaluating bone properties.

Adult↗
PubMed1986

Trabecular bone mineral density measurement in vivo: use of the ratio of coherent to Compton-scattered photons in the calcaneus.

Trabecular bone mineral density (TBMD) was measured in vivo in the calcaneus by a new method that uses the ratio of coherent to Compton-scattered photons arising from irradiation of a small volume of trabecular bone by a gamma ray source with highly collimated geometry. TBMD values for healthy men (22-77 years) were in the range of 180-357 mg/ml, and values for healthy women (18-73 years) were in the range of 160-321 mg/ml. In contrast, values in a small group of paraplegics were in the range of 90-199 mg/ml.

Adult↗
PubMed1986

Effect of intense physical activity on the bone-mineral content in the lower limbs of young adults.

The effect of intense physical training on the bone-mineral content of young adults who are unaccustomed to physical activity has not yet been established. In this study, 268 male recruits, eighteen to twenty-one years old, were evaluated before and after fourteen weeks of strenuous physical training. The bone-mineral content of both legs at the level of the distal third of the tibia in each individual was measured using single-beam photon absorptiometry. The subjects started their training with equal values for bone-mineral content in both legs. During the training period, the average bone-mineral content of the left leg increased by 11.1 per cent and that of the right leg, by 5.2 per cent. In the group of subjects who did not complete the training course, mainly because they incurred stress fractures, the increase in bone-mineral content was significantly less than the increase in those who completed the program. This study indicated that in young adults a high level of loading of bone results in either a stress fracture or a rapid increase in bone-mineral content.

Adolescent↗
PubMed1984

Fracture of the human femoral neck: effect of density of the cancellous core.

Thirty three fresh femora from 18 cadavera were loaded to fracture at a deformation rate of 5 mm/min to study the effect of density of the cancellous core in fracture initiation of the femoral neck. The neck of the femur was modelled as a composite beam subjected to bending and the ultimate strength of the bone at the superior aspect of the neck was calculated from the model, which was fed by the mechanical tests and geometry measurements. The area porosity of the cancellous core was introduced into the beam model after measuring the apparent density of dry fat-free bone for each specimen. The results showed a strong dependence between the ultimate strength obtained and the cancellous bone density, the latter previously measured for each specimen by the non-invasive Compton scattering technique. Area porosity of the femoral neck was found to have little effect on the results obtained, permitting the use of an average value for this parameter in calculating the ultimate strength of the neck of the femur.

Adult↗
PubMed1983

A new method of measuring bone density in the lower tibia of normal and postinjury limbs. A quantitative and comparative study.

In osteoporosis, a pathologic state of diminution of bone mass, radiography is the most widely used diagnostic method, but it is only descriptive and mainly depicts changes in the compacta. Based on the Compton photon-scattering phenomenon, a noninvasive yet quantitative measuring method for analyzing bone density was developed. The values of repeated measurements taken at identical locations did not vary by more than 2%. Using this technique, bone density of the lower tibia was measured in 39 men and 36 women; 14 had been affected by an injury to a knee or calf and immobilized five to eight years prior to this investigation. The measured values demonstrated an impressive equality between the tibiae of each individual and between the two sexes up to 50 years of age. However, these values correlated poorly with the bone density of the distal radius. In women older than 50 years of age, bone density decreased. Bone density was also low in all postinjury limbs. When compared with radiographic and bone mineral content (BMC) measurements of the same limb at the same location, the bone density measurements were useful and reduced the range of uncertainty of diagnosing osteoporosis by radiography only. Little or no correlation was found between bone density values and BMC measurements. The Compton scattering technique may become a precise and sensitive method for the clinical diagnosis of postinjury osteoporosis and quantitation of the long-term effects of limb injuries.

Adolescent↗
PubMed1982

The relationship between bone density, mineral content, and mechanical strength in the femoral neck.

The bone density, mineral content and average shear stress in bending at failure were measured in vitro in 33 femoral necks of women and men of different ages. The correlations between these three parameters as well as their correlation with the Singh index were carefully analyzed and found to show that the Singh index is of no clinical value. The best correlation exists between bone density and shear stress at failure. Practically no correlation is found between the breaking stress and Singh index. The breaking stress decreases with age much faster than the bone density or bone mineral content. The correlation between the work to fracture and the bone density or its mineral content is only moderate. The bone density is best indicator for the compressive bone strength. The changes of bone strength are apparently influenced by factors other than the bone density and mineral content, although the possibility that small changes in bone density or mineral content cause large changes in bone strength cannot be excluded.

Absorptiometry, Photon↗