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At least 19 recordsLinked to original sources
PubMed1978

Effect of chronic low-level cadmium intoxication on the Haversian remodeling system in dogs.

This experiment was carried out in order to determine whether the chronic administration of low doses of cadmium resulted in an alteration of the haversian bone remodeling system in dogs. Two pairs of littermate beagles were administered 25 ppm cadmium chloride in their drinking water for 6 months. Four beagles matched for age and sex from the same colony served as controls. By means of fluorescent labeling, we measured haversian bone remodeling parameters according to the techniques described by Frost. Statistical analysis of the results showed significant changes at the 0.01 level in: activation frequency, appositional rates, and number of osteoid seams. At the 0.05 level, significant differences were found in the number of resorption spaces and the bone formation rate. In the absence of other evidence indicative of an alteration in the internal milieu of the dogs, it is concluded that a direct toxic action of cadmium on the mechanisms of activation of cells responsible for the creation and formation of new haversian systems cannot be excluded.

Age Factors↗
PubMed1990

[An experimental study of the orthodontic force effect on internal remodeling of mandibular bone].

The role of mechanical stress in determining bone structure by influencing its cellular processes during remodeling has been discussed. But previous studies have not provided an adequate background of knowledge to explain the effect of orthodontic force in internal remodeling of the bones. This study was performed to determine the relationship between stress distribution induced by orthodontic force and alteration of internal remodeling in mandibular bone. Seven young adult mongrel dogs of unknown age were used as experimental animals. The bilateral lower 4th premolars were extracted. After 106 days, the 3rd premolars on the right side were moved distally by coil springs for 106 days. Twice pulse labels of tetracycline and calcein were performed to obtain histomorphometric parameters of cortical bones prior and posterior to tooth movement. With the use of microscopic plotting tool and minicomputer, the direction of haversian systems was reconstructed three-dimensionally. To make a comparison with the alteration of histomorphometric parameters and direction of Haversian systems, the principal stress distribution of mandibular bone caused by orthodontic force was obtained by means of 3-D finite element method analysis. Experimental results indicate as follows. 1. The osteoid seams number per unit area (OsAf) and the labeled surface per unit area (TcAf) increased significantly at both alveolar and basal bone region compared with control side. 2. The resorption cavities number per unit area, (Ar) increased significantly at alveolar bone region. But no significant changes were noted at basal bone region. 3. No significant differentiations were noted in mineral appositional rate (Mo) between any bone regions nor label timings. 4. There is large variance between the direction of Haversian systems and the maximal principal stress vector. But a significant alteration of the direction of Haversian systems was found in highly stressed and younger bone areas. From these findings, it can be speculated that, as a primary reaction of bone against stress, the optimum microscopic structural change took place in areas of bone which bore tension or pressure due to excess stress, at the same time the internal remodeling of bone was accelerated by increase of activation frequency (mu), accompanied with no increase of remodeling periods (sigma).

Animals↗
PubMed1975

Structural changes of cortical bone in secondary hyperparathyroidism: replacement of lamellar bone by woven bone.

In femoral cortical bone of 16 uremic patients with long standing renal insufficiency an increased fraction of woven bone was found both in Haversian and in interstitial bone. Either partly resorbed Haversian systems were replaced by non lamellar woven bone or single Haversian systems showed partly well organized lamellar bone and partly disorganized non lamellar texture without signs of antecedent resorption. The replacement of lamellar bone by woven bone was measured morphometrically in undecalcified ground sections. Woven bone was defined by its lack of structural birefringence under polarized light. In advanced cases of secondary hyperparathyroidism more than 60% of cortical bone were composed of woven bone. The substitution of immature less organized woven bone for mature well orfanized lamellar bone has important implications for the biomechanical properties of the skeleton.

Adult↗
PubMed1979

The effect of chronic administration of trisodium nitrilotriacetate (Na3NTA) on the haversian remodelling system in dogs.

Trisodium nitrilotriacetate from the environment is reported to accumulate in bone. Two skeletally mature male littermate beagles were administered Na3NTA in a concentration of 2.5 mg/kg body weight in their drinking water for a period of 7 months. Rib biopsies were obtained from the dogs after fluorescent labelling before and at the end of the experimental period. Blood levels of zinc were measured at the same times. Twenty-two similar dogs from the same colony acted as controls. We noticed a decrease in radial closure rates and percent osteoid seams labelled between the experimental and the control animals which was statistically significant at the 0.05 level. The serum levels of iPTH and the bone levels of zinc showed no statistically significant difference. Accepting the fact that the treatment population was small and that the changes observed--although statistically significant--were minimal, it cannot be discounted that the exposure of these animals to Na3NTA for a longer period of time would not have had a more adverse effect on haversian bone remodelling activity.

Acetates↗
PubMed1988

Morphologic comparison of healing patterns in ethylene oxide-sterilized cortical allografts and untreated cortical autografts in the dog.

Full-thickness canine cortical allografts were harvested cleanly, sterilized with ethylene oxide, and stored at 22 degrees C. The sterilized allografts were incorporated into segmental, femoral fracture repairs and evaluated for 6 months. Allografts were compared with untreated cortical autografts, which also were incorporated into segmental, femoral-fracture repairs for 6 months. Sequential fluorochrome labeling at 8, 11, 21, and 24 weeks after surgery made it possible to evaluate retrospectively the time of new bone formation. Morphometric evaluations were made of the numbers of labeled haversian systems, the percentage of labeled bone, and the porosity of the bone. The cortical allografts had bone formation in the proximal and distal portions of the graft, with the greatest activity at 5 to 6 months after surgery. Activity in the center of the allograft was minimal. Cortical autografts had bone formation throughout the graft, with the greatest number of haversian systems labeled at 3 months after surgery. We concluded that cortical allografts heal and remodel more slowly and in a different sequence of events than do cortical autografts.

Animals↗
PubMedDate not supplied

A topographic quantitative analysis of the post-natal bone formation in the auditory ossicles of the dog.

The amount and distribution of the post-natal bone deposition in the auditory ossicles and in the left tibia of dogs of varying ages were studied by means of alizarin labelling. The relative amount of fluorescent new-formed bone was expressed as a percentage ratio NB/(NB+PB) of new bone (NB) on the pre-existing bone (PB). The result was that the post-natal bone deposition (1) was larger in the tibia than in the incus, malleus and stapes; (2) significantly decreased with age both in the ossicles and in the tibia; (3) in the stapes it stopped at 3 months, while it was present in the tibia, incus and malleus even at 12 months. In the ossicles the post-natal bone deposition takes place both on the periosteal surfaces of the ossicles and on the internal surfaces of the haversian systems. The first process produces an appositional growth that stops in all three ossicles within the 1st month of post-natal life, the second one produces an internal growth that continues until the age of three months in the stapes, while in the incus and malleus it occurs in small amounts, even in the 12th month of life. In the ossicles all the new-formed bone tissue, periosteal and osteonic, is built up by primary bone (addition bone). In the tibia from 50 days of age the primary bone is gradually replaced by secondary haversian systems as a consequence of remodelling processes.

Age Factors↗
PubMed1979

Appositional bone formation rates in the Beagle.

Measurements of haversian appositional bone formation rates were carried out on 400 haversian systems in 28-month-old standardized research colony-raised Beagles, using the midshaft of the 11th rib. The appositional bone formation rate was gradual and regular when the circumference of the outer tetracycline ring was more than 0.35 mm, but the regularity of the measured rate disappeared when the outer tetracycline ring circumference was less than 0.35 mm. Erroneous conclusions could be drawn from measurements of appositional bone formation rate in these animals if this fact were not taken into consideration, and we concluded that in pre- and postexperimental biopsy sections in the ribs of these animals, haversian systems with tetracycline ring circumferences above 0.35 mm must be measured in both situations if the differences in appositional bone formation rate are to be construed as being truly significant.

Animals↗
PubMed1977

The effect of chronic low level lead intoxication on the Haversian remodeling system in dogs.

The greatest portion of lead ingested by human beings or experimental animals is stored in bone. Once in bone, lead is difficult to remove. It may have a half-life of 20 years or more and could interfere with bone metabolism. The effects of lead intoxication on the production of intercellular matrix have been reported previously but the effects of lead on bone turnovers rates were not reported. In this paper we reported the results of a study of the effects of lead on bone turnover in dogs. Differences between experimental and control dogs were found when measuring appositional rates, radial closure rates, activation frequencies, osteon formation times, and bone formation rates. We found that dogs subjected to a low dose (1.3 mg. per kg. per day) of lead over a long period of time (201 days) showed a statistically significant decrease in bone formation activity at the cell (90 per cent), tissue (85 per cent), and organ (78 per cent) levels when compared to controls. Although these observations were made on a small experimental and control sample (four dogs), they suggest that chronic low dose lead intoxication does alter normal bone physiology.

Animals↗
PubMed1979

Cortical circulation of long bones.

Intravascular injections of India ink in the femora of adult dogs revealed the existence of two distinct vascular systems in the cortex. One courses through the entire thickness of the cortex and is a regular, longitudinal network of uniform capillaries which is in continuity with the periosteal and endosteal networks. Once the haversian systems form a second network appears, radiating from the bone marrow. That system, primarily transverse, anastomoses in the haversian canals with the capillaries of the first system. Therefore, the merging of the two networks occurs primarily in the middle layer of the cortex. The direction of the arterial blood flow in the mature animal is predominantly centrifugal, while the venous drainage is centripetal. In the immature animal, the contribution of the periosteal network is much greater. Because the two cortical systems are profusely anastomosed with each other and with the periosteal and endosteal circulatory networks, the blood can flow in either direction, depending on physiological conditions.

Animals↗
PubMed1979

[Bone perfusion after plate osteosynthesis. A study of the intact rabbit tibia with disulfin blue vital staining].

After operative fracture treatment an interference with blood supply has to be expected. The fixation of a plate to an intact rabbit tibia lead to extended areas where circulation is disturbed. These disturbances were partially reversible within one week without structural changes visible in the recovering bone. Only the zones remaining without vascular supply after one week started to recover in the 4th week, when intracanalicular remodelling and the formation of new Haversian systems became visible at the borders of the avascular regions.

Animals↗
PubMed1992

Micromechanics modeling of Haversian cortical bone properties.

A finite-element micromechanics model for Haversian cortical bone tissue has been developed and studied. The model is an extension of two-dimensional micromechanics techniques for fiber-reinforced composite materials. Haversian systems, or secondary osteons, are considered to be the fiber component, and interstitial lamellar bone the matrix material. The cement line is included as an 'interphase' component along the fiber/matrix interface. The model assumes a regular repeatable spacing of the longitudinally aligned continuous fibers and is, therefore, restricted to approximating Haversian cortical bone in its present form. Haversian porosity is modeled explicitly by incorporating a hollow fiber to represent the Haversian canal. Solutions have been obtained by applying uniform macroscopic stresses to the boundaries of the repeating unit cell model. Macroscopic mechanical property predictions correspond reasonably well with the experimental data for cortical bone, but are necessarily dependent on the input properties for each constituent, which are not well established. The predicted variation in the elastic modulus with porosity is not as sensitive as that observed experimentally. Stresses within the constituents can also be modeled with this method and are demonstrated to deviate from the macroscopic applied stress levels.

Biomechanical Phenomena↗
PubMed1979

Gross and microscopic anatomical studies of palate structure and osteotomy site.

A normal 1-year-old infant palate and a newborn cleft palate were studied grossly, radiographically, and microscopically for histological structure in hard palate osteotomy sites. A correlated study of biopsies from an osteotomy site seven days postoperatively and another at twelve months following osteotomy was also made. The findings showed that successful osteotomy in infant cleft palate surgery translocates autogenous fibrous bone and osteogenic cells into a cleft-bridging position. Woven fibrous bone rapidly forms across the cleft, and then matures by lamellar bone replacement and haversian system remodeling. Both normal and cleft palates have a rich anastomosis of microscopic blood supply that is vitally important in the remodeling process. These factors may help to explain successful long-term results in early cleft palate osteotomy surgery.

Cartilage↗
PubMed1985

The structure of the trabeculae of cancellous bone. 1. The calcaneus.

87 either cylindroid or laminar trabeculae, isolated from the perpendicular or inferior bundles of the human calcaneus, were embedded in methylmatecrylate and serially cut along longitudinal and transversal planes with a rotatory-blade saw. The microscopical study of the sections showed that in 83% of the samples secondary osteons run along the longitudinal axis of the trabeculae and their lumina either form a continuous channel network throughout each trabecula (37% of cases) or are restricted to discrete segments (46% of cases). The trabeculae entirely devoid of osteons (17%) are the thinnest, never exceeding 400 microns in thickness. This value is not even exceeded by the segments devoid of osteons in the trabeculae in which the Haversian canals occur only intermittently; conversely, the segments containing Haversian canals can reach and exceed 600 microns in thickness. The maximum distance of the osteocytic lacunae from filtering surfaces--i.e. outer surface of the trabeculae or inner surface of the Haversian canals--was found to be almost the same in the segments of the trabeculae that enclose or not osteons, even though the average trabecular thickness is greater in the former than in the latter regions. On the basis of these findings the formation of endotrabecular osteons may be viewed as a device that indirectly favours the metabolic exchange of deep-seated osteocytes while increasing the free surface area available for bone tissue reconstruction. It remains doubtful whether the Haversian systems may also contribute to improve the mechanical properties of the trabeculae. The arrangement of the collagen fibrils, which differs between cylindroid and laminar trabeculae, is apparently well suited to ensure the resistance of the trabeculae to mechanical loading through the use of the least amount of building material, in accordance with Wolff's law.

Adult↗