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PubMed1981

Histomorphometric evaluation of the effects of low dose parathyroid hormone administration on cortical bone remodeling in adult dogs.

The effects of low dose levels of parathyroid hormone (PTH) on cortical bone remodeling of adult dogs were evaluated under conditions of normal turnover and accelerated remodeling produced by periosteal elevation. Six female dogs were administered PTH (2.5 units per kg. per day) intravenously in equally divided doses 6 hours apart for 60 days. The level and dose schedule of PTH used in this study resulted in a significant elevation in blood calcium above baseline values only at experimental day 5, no change in serum phosphorus and magnesium, and a transient increase in urinary hydroxyproline excretion on day 10. Accelerated cortical bone remodeling was induced by surgical elevation of periosteum of the 9th rib prior to PTH administration. Static and dynamic bone changes were analyzed using histomorphometric methods following tetracycline and DCAF ((2,4 bis) N, N'-di-(Carboxymethyl) aminomethyl fluorescein) in vivo double labeling. The results of this study suggested that the response of cortical bone to PTH was dependent upon the existing remodeling rate. PTH increased the radial closure rate and decreased the osteon formation time in unaltered cortical bone. These findings suggested that the initial anabolic effect of PTH may be due to increased bone formation at the osteoblastic level in existing Haversian units. In ribs with periosteal elevation, PTH decreased the circumference and thickness of osteoid seams, and there was a trend toward prolonged osteon formation time. The number of bone resorption sites was greater than the number of formation sites. PTH administration did not significantly change activation frequency or remodeling in cortical bone of adult dogs under conditions of normal turnover or accelerated remodeling. The accelerated remodeling produced by periosteal elevation appeared to mask certain responses to cortical bone to low dose levels of PTH.

Age Factors↗
PubMed2001

[Effect of sequential application of calcitonin and parathyroid hormone on bone remodeling process, an experimental research].

OBJECTIVE: To investigate the effect of sequential application of calcitonin and parathyroid hormone (PTH) on bone remodeling process. METHODS: Twelve female rats were divided equally into 2 groups: experimental group and control group. 1 U/100 g of calcitonin was injected intramuscularly to 6 rats for two days, and rrPTH in dosage of 30 micrograms was injected intramuscularly in the fourth and fifth days. At the sixth day their lumbar vertebral bodies were resected. Undecalcified and decalcified bone sections were made to be observed by optical microscopy and electronic microscopy. Bone histomorphological parameters were measured. Normal saline and solvent of the same volume were injected intramuscularly to the controls. RESULTS: The OS/BS (%), O. Th (micron), N.Ob.S (cell/mm), and Vos/TV (%) were 19.9% +/- 6.2%, 3.4 microns +/- 0.4 micron, 37.6 cells/mm +/- 4.6 cells/mm, and 1.8% +/- 0.6% respectively in the experimental group, significantly higher than those in the control group (P < 0.05). After the PTH administration, more and plumper osteoblasts were observed. They were rich in rough endoplasmic reticulum, mitochondria, and Golgi apparatus. CONCLUSION: Sequential application of calcitonin and parathyroid hormone obviously promotes the bone formation process. Both sites of bone remodeling formation and sites of bone modeling formation, especially the latter, increase.

Animals↗
PubMedDate not supplied

A bone-remodelling scheme based on principal strains applied to a tooth during translation.

This paper investigates the role of principal strains within the periodontal ligament (PDL) during bone remodelling in orthodontics and particularly in the case of bodily motion (pure translation). Using analytical formulas of stress and strains within the PDL for the particular case of a paraboloidal central incisor during translation, the strains are directly related to the motion of the interface between the alveolar bone and the PDL, called bone surface. It is shown that both normal and shear strains within the PDL are of the same importance for bone surface motion. Moreover, both "mean average" and "geometrical average" of principal strains within the PDL play a significant role in the bone remodelling process, as they contribute with the same proportionality. In summary, the proposed formulas differ than previous ones that had been successfully applied to describe remodelling within long bones. The proposed theory is also sustained by a linear finite element analysis.

Algorithms↗
PubMed2006

CT analysis and histopathology of bone remodeling in patients with chronic rhinosinusitis.

OBJECTIVE: To evaluate the findings of computed tomography (CT) and histopathology of the bulla ethmoidalis as objective markers of bone remodeling in chronic rhinosinusitis (CRS). METHODS: Preoperative ostiomeatal unit (OMU) scans and histopathologic findings of the bulla ethmoidalis were performed on 23 patients (39 sides) undergoing endoscopic sinus surgery for CRS. Lund-Mackay scores and Hounsfield units (HU) of the bulla were checked in coronal CT scans. The pathologist graded the severities of the mucosal and bony changes in histopathology. Statistical analysis was performed using Mann-Whitney U test and Spearman correlation coefficient (r). RESULTS: The HU values of the bulla were significantly increased with higher Lund-Mackay scores in OMU CT (r = 0.405, P = 0.01). The bony grades in histopathology were significantly increased with higher mucosal grades (r = 0.821, P = 0.0001). These findings in CT scans and histopathology were well correlated with each other (r > 0.3, P < 0.05). CONCLUSION: HU may be a useful objective marker of bone remodeling in chronic rhinosinusitis.

Adolescent↗
PubMed1990

Role of transforming growth factor-beta in bone remodeling.

Transforming growth factor-beta (TGF-beta) plays a critical role in bone remodeling. TGF-beta stimulates matrix protein synthesis, has dramatic effects on the bone cells responsible for bone formation and resorption, and is abundant in bone and bone-conditioned media. Multiple sources of TGF-beta have been described. It was initially purified from platelets. Two distinct forms of TGF-beta have been purified from bone. The second form, TGF-beta II, was initially purified from bone but was then identified in platelets and also as the major TGF-beta in the monkey kidney BSC-1 cell line. The two bone-derived factors were called cartilage-inducing Factor A (CIF-A) and cartilage-inducing Factor B (CIF-B), based on their capacity to induce the formation of extracellular matrix proteins, which are characteristic of cartilage. CIF-A is identical to the TGF-beta purified from platelets, which is called TGF-beta I. CIG-B is the same as TGF-beta II, which was sequenced soon after CIF-B was discovered and characterized. There is 70% sequence homology between the two forms. The largest source of TGF-beta in the body is present in bone (200 micrograms/kg tissue), although the most concentrated source is in platelets. TGF-beta has multiple effects on bone cells depending on their phenotype and/or stage of differentiation. Osteoblasts, the cells responsible for formation of new bone and perhaps cellular control of bone remodeling, are directly affected by TGF-beta, which can induce differentiation or proliferation, depending on the osteoblastic cell type examined. TGF-beta inhibits the formation of osteoclast precursors and bone resorption and, in greater concentrations, has inhibitory effects on isolated osteoclasts, the cells responsible for bone resorption. TGF-beta may act as a bone-coupling factor linking bone resorption to bone formation.

Amino Acid Sequence↗
PubMed1995

Lack of evidence that cyclosporine treatment impairs calcium-phosphorus homeostasis and bone remodeling in normocalcemic long-term renal transplant recipients.

Since the effects of cyclosporine on mineral and bone metabolism are controversial, we studied calcium regulating hormones, calcium-phosphorus (Ca-P) metabolism, and bone remodeling, assessed by serum osteocalcin, in long-term renal transplant recipients (RT). Forty-seven normocalcemic patients with good renal function receiving cyclosporine (CT, n = 27) or not (NC, n = 20) were studied at baseline and after an oral Ca load. CT and NC had similar age, daily dose of steroids, GFR level, and duration of transplantation. Baseline evaluation included 24-hr urinary Ca, P, TRP, TmP/GFR, fasting serum intact PTH, 1,25-(OH)2D, 25OHD, osteocalcin, Ca, and P. Subjects of the two groups had excessive secretion of PTH, tubular P wasting, and high serum osteocalcin level, as is usual in RT. However, there was no difference between CT and NC regarding any baseline variable. Ten CT and ten NC, matched for duration of transplantation and serum PTH level, ingested 1g Ca to achieve an acute dynamic study of PTH secretion and Ca-P metabolism. In both CT and NC, this Ca load caused the same decreases in serum PTH (P < 0.001), NcAMP (P < 0.05), and urinary P (P < 0.001) and the same increases in serum and urinary Ca (P < 0.001), and in both TmP/GFR and TRP (P < 0.001). These results strongly suggest that cyclosporine treatment had no significant effect on calcium-regulating hormone secretion, P-Ca metabolism, and bone remodeling level. We therefore consider that cyclosporine is unlikely to have any prominent role in the abnormalities of bone endocrine and mineral metabolism that are common in long-term kidney recipients.

Administration, Oral↗
PubMed1995

Flavonoids alter bone-remodelling in auditory ossicle organ cultures.

The beneficial role of bioflavonoids in an otosclerosis-like bone-remodelling process can be implicated from its interference with bone resorption induced by prostaglandin E2 (PGE2) in cultured guinea pig ossicles. Ipriflavone (7-isopropoxy-isoflavon) and quercetin reduced PGE2-elevated collagenase-like peptidase (Cl-peptidase) activity and potentiated a PGE2-induced decrease in collagen synthesis. The fact that PGE2 effects are mediated through cyclic AMP in bone turnover and flavonoids act synergistically with PGE2 in collagen synthesis confirm a cyclic AMP phosphodiesterase inhibitory role of flavonoids. It has already been attempted to use Ipriflavone medical treatment of otosclerosis. Quercetin, which has a better than Ipriflavone water-solubility seems as promising as Ipriflavone in the control of the otosclerotic bone-remodelling disturbance.

Animals↗
PubMed2005

Bone remodeling of a femoral head after transtrochanteric rotational osteotomy for osteonecrosis associated with slipped capital femoral epiphysis: a case report.

A rare case of a 12-year-old boy on whom a joint-preserving operation for osteonecrosis after slipped capital femoral epiphysis (SCFE) was performed, is described. Firstly, in situ pinning was performed for acute-on-chronic SCFE. However, osteonecrosis and collapse of the femoral head occurred at 7 months after surgery. Secondly, transtrochanteric rotational osteotomy (TRO) was performed against progression of the collapse of the femoral head. Eight years of X-ray observation revealed bone remodeling at the osteonecrotic region. No documentation has been reported about the potential of bone remodeling of a femoral head with osteonecrosis after SCFE. This case indicates that a joint-preserving operation such as TRO is capable of promoting bone remodeling in such circumstances.

Bone Remodeling↗
PubMed1996

Radiograph processing for quantitative assessment of bone remodelling.

Video-densitometric analysis has proved useful in the study of bone remodelling, however, for more efficient results, an investigation procedure that enables the comparison of X-rays is needed. In the present research an automated method has been developed which considerably speeds up the entire procedure through the implementation of specially designed C++ software. At present, a sequence of six X-rays can be analyzed in about 1 h irrespective of the number of areas to be investigated, which can be arbitrarily increased (200 or more). Analysis is fast as well as more reliable and accurate. In clinical practice, the results offer an effective support to observation on the biomechanical behaviour of bone implant systems.

Absorptiometry, Photon↗
PubMed2005

Arachnoid cysts with orbital bone remodeling--two interesting cases.

PURPOSE: To describe two cases of arachnoid cyst that altered the bony orbit. METHODS: Case report. RESULTS: Cases of unilateral arachnoid cyst are described in two men, both over the age of 60. The patients were evaluated with computed tomography (CT) scans and in each, an arachnoid cyst in the middle cranial fossa caused bone remodeling with exophthalmos in one. These patients were followed clinically and radiographically over a number of years with no change. CONCLUSION: Arachnoid cysts in the middle cranial fossa have the potential to result in clinically significant proptosis due to bone remodeling of orbital walls. Patients with unexplained proptosis should be evaluated with CT scans to establish the presence of bone remodeling and an arachnoid cyst, which can be confirmed with T2-weighted magnetic resonance imaging (MRI).

Aged↗
PubMed1984

Effects of iron overload on bone remodeling in pigs.

For study of the effects of an iron overload on bone remodeling, 5 control pigs were compared with 5 pigs given a total dose of 10.8 g of parenteral iron in 36 days. Treated pigs developed an iron tissue overload demonstrated by a marked increase in bone and liver iron. Except for a modest increase in SGOT, there was no biochemical or histologic sign of liver damage. Serum levels of 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D were unchanged in the treated pigs. There was no accumulation of iron in the parathyroid glands and the serum immunoreactive parathyroid hormone level was unchanged in the treated animals. Bone histomorphometry after double tetracycline labeling showed that in the treated pigs osteoblast cell surfaces, double and total labeled surfaces, appositional rate, and formation at tissue level were significantly decreased, and reversal surfaces were increased. Mineralization was not impaired because the osteoid thickness was unchanged. From the morphometric measurements it was concluded that osteoblast recruitment and the collagen synthesis rate were decreased. Mean wall thickness, which indicates the amount of bone synthesized, was also lowered. In contrast, the osteoclastic resorption surfaces and the depth of lacunae resulting from osteoclast resorption were unchanged by treatment. Despite this imbalance between formation and resorption, trabecular bone mass estimated on trabecular bone volume and bone ash was unchanged after 36 days' treatment. Perls' stain revealed that iron deposits were present in osteoblast and osteoclast cells and also inside the bone matrix, because there was a linear deposit along the trabecular surfaces, cement line, and osteoid-mineralized bone interface. Therefore, because treatment induced no modification of the major humoral regulators of bone metabolism, it is suggested that iron, which was present in bone cells and matrix, could play a role in bone remodeling.

Alanine Transaminase↗
PubMed2003

Mandibular bone remodeling under a choline-deficient diet: a histomorphometric study in rats.

BACKGROUND: A deficiency of lipotropic factors in the rat induces renal, hepatic, and/or hematic damage. The aim of the present study was to evaluate the effect of a choline-deficient diet and refeeding on mandibular bone remodeling. METHODS: Fifty Wistar rats were divided into 5 groups: group 1 (G1): control diet for 15 days; group 2 (G2): choline-deficient diet for 15 days; group 3 (G3): control diet for 30 days; group 4 (G4): choline-deficient diet for 30 days; and group 5 (G5): choline-deficient diet for 15 days and control diet for 15 days. All animals were sacrificed by ether overdose. The mandibles were resected, radiographed, decalcified, processed, and embedded in paraffin. Bucco-lingually oriented sections were obtained at the level of the interradicular bone of the medial roots of the left first molar, and stained with hematoxylin and eosin (H & E). Bone tissue density and bone remodeling were determined histomorphometrically. Body weight, food intake, hematocrit, and hemoglobinemia were also recorded. RESULTS: Microscopic observation revealed that osteogenesis was lower in rats fed a choline-deficient diet, at both 15 and 30 days, and that this decrease did not revert with a control diet. Histomorphometric evaluation showed 37% and 27% reduction in bone tissue density at 15 and 30 days, respectively, and a 30% decrease in bone formation at 30 days, compared to controls. CONCLUSION: In this experimental model, a choline-deficient diet led to altered bone remodeling as observed by a marked reduction in osteogenesis.

Analysis of Variance↗
PubMed1995

[Observation of alveolar bone remodeling accompanied with tooth movement by in situ hybridization--expression of type I collagen and bone sialoprotein mRNAs].

The purpose of this study was to investigate expression of type I collagen and bone sialoprotein (BSP) mRNAs in the alveolar bone accompanied with tooth movement. The right side of the upper jaw of the rat was used for orthodontic tooth movement, and the left side was used for physiological tooth movement. After the proper number of days of movement, histological specimens were decalcified and sliced into paraffin sections. The expression of mRNAs was examined by the in situ hybridization method. In the samples of physiological tooth movement, a high level of expression in both mRNAs was observed in osteoblasts along the mineralization front and adjacent osteocytes in the interradicular septum (IRS). In contrast, a low level of mRNA expression was observed on the opposite side of the IRS. In the specimens of experimental tooth movement, a high level of expression was detected in the osteoblasts on the tension side of IRS, but negligible reaction in those on the compression side. These results suggest that BSP gene expression as well as that of collagen are related not only to mineralization in physiological bone remodeling but also to the process by activated osteoblasts induced by orthodontic force. In addition, response to the artificial force was observed in osteocytes in IRS.

Animals↗
PubMed1991

Experimental determination of "the law of bone remodeling" and effect of rat parathyroid hormone (1-34) infusion on derived parameters.

The dependence of bone remodeling probability on bone age was investigated by fitting a previously described mathematical model to data describing the decline of radioactivity in the femurs of growing rats prelabeled with [3H]tetracycline. The remodeling probability declined with increasing bone age, but because the data were obtained at the whole bone level, several explanations for this finding are possible, and the results cannot be extrapolated beyond the duration of the experiment. A simpler exponential model that assumes remodeling probability is constant can be used to calculate bone resorption rate within a limited time period. A significantly increased bone resorption rate in PTH-infused rats could readily be demonstrated using the exponential model. A more sophisticated statistical analysis was required to discriminate between control and PTH-infused rats using the more complex model in which resorption rate was not constant.

Animals↗
PubMed1988

Histologic evidence of an abnormal bone remodeling in B-cell malignancies other than multiple myeloma.

In a prospective study of the quantitative bone changes induced by B-cell cancers other than multiple myeloma (MM), but including chronic lymphocytic leukemia (CLL; n = 8), hairy cell leukemia (HCL; n = 3), and Waldenström disease (WD; n = 7), an abnormal bone remodeling close to malignant cells was found in 80% of the patients. This was observed more frequently in cases of diffuse, but not nodular, bone marrow involvement by tumor cells. More particularly, excessive bone resorption (a major feature of MM) associated with a normal to low bone formation (i.e., uncoupling bone disease) was the most frequent feature and in the same range of that observed in overt MM. However, as opposed to MM, this bone resorption was characteristically mediated by small mononucleated osteoclasts (i.e., microresorption). The same phenomena of abnormal bone remodeling, the uncoupling process, excessive bone resorption, and above all microresorption were confirmed by the detailed bone study of five cases of B-cell cancers other than MM presenting lytic bone lesions and hypercalcemia. The current findings are important for clarifying the biology of these B-cell malignant diseases, and also could be of diagnostic and prognostic value.

Adult↗
PubMedDate not supplied

ESB Research Award 1992. The mechanism of bone remodeling and resorption around press-fitted THA stems.

A major problem threatening the long-term integrity of total hip replacement is the loss of proximal bone often found around noncemented stems in the long term. It is generally accepted that 'stress shielding' is the cause for this problem: after implantation of the prosthesis the surrounding bone is partially 'shielding' from load carrying and starts to resorb. One of the proposed answers to this problem is the application of press-fitted stems. These smooth-surfaced implants are thought to provoke higher proximal bone loading, and, hence, less stress shielding than bonded implants, because they are wedged into the femur every time when loaded. However, in a two-year experiment in dogs, similar amounts of resorption of the proximal cortex were found around press-fitted and bonded implants. The question arises how similar resorption patterns can develop under completely different stress conditions, and whether this phenomenon can be explained by adaptive bone remodeling theories based on Wolff's law. In the present study an answer was sought for this question. An advanced iterative computer simulation model was used to analyze the remodeling process in the animal experiment. Three-dimensional finite element models were constructed from the animal experimental configuration, in which smooth, press-fitted stems were applied unilaterally in the canine. The FE model was integrated with iterative remodeling procedures, validated in earlier studies. In the model an appropriate non-linear representation of the loose bone-implant interface was realized, also capable of simulating the proximal interface gap that was found around the uncoated implants. The simulation models predicted similar amounts of proximal bone loss and distal bone densification as found in the animal model. Hence, the cortical bone loss could indeed be predicted by the strain-adaptive bone remodeling theory. By unraveling the simulation process, the question stated above could be answered. Densification of the distal bone bed during the initial remodeling process was found to cause reduced axial stem displacement (elastic subsidence), decreasing the wedging effect of the stem and, hence, decreasing the loading of the proximal bone, resulting in proximal bone loss. Hence, whereas in the case of bonded stems the proximal resorption process develops monotonously to a new equilibrium, the process around smooth, press-fitted stems develops nonmonotonously. This is due primarily to the unbonded interface conditions and the development of a proximal fibrous membrane. The remodeling process then gradually causes the stem to be jammed in the distal diaphyses (proximal 'stress bypass').

Alloys↗
PubMed1995

The application of scanning acoustic microscopy in a bone remodeling study.

Scanning acoustic microscopy (SAM) was used in the evaluation of bone remodeling around a cylindrical unicortical defect. SAM is a technique for the nondestructive evaluation of materials, and has only recently been employed as an orthopaedic research tool. The utility of SAM was demonstrated by using it to measure an elastic property known as acoustic impedance. Specifically, the acoustic impedance of bone formed by remodeling around a cylindrical defect was measured. The defects were filled with either a low modulus "void" or rigid inclusion to create various states of stress in the bone in the vicinity of the defect. After six months of implantation of the inclusions in the sheep metatarsal, new bone formation on periosteal and endosteal surfaces about the defect region was observed. These regions of new bone were less stiff and had 18.0 +/- 6.5% lower acoustic impedance than the pre-existing bone in the intracortical region of the metatarsal. There was no difference in the degree of new bone formation about void and rigid inclusions. Both underwent significant adaptational changes in response to the elevated stress about the defect. These changes affected the basic structure of the bone cross-section at the level of the defect and effectively reduced the stress levels about the defect. By using SAM to measure acoustic impedance, it was seen that little internal remodeling occurred in the intracortical region. Hence, the primary mechanism of strain-induced bone remodeling observed in this experimental model was surface remodeling.

Acoustics↗
PubMed1991

Histomorphometric study of trabecular bone remodeling during condylar process fracture healing in the growing period: experimental study.

Trabecular bone remodeling during condylar fracture healing in the growing period was analyzed by histomorphometry with a synchronous system. Data from the study showed displacement of the fractured condyle was compensated by the changes in remodeling ascribed to the pubertal spurt of growth, and that such remodeling still continued even after clinical healing. The regional acceleratory phenomenon, evolved to potentiate tissue healing, was observed 1 week after induction of the fracture. Mesenchymal cells were presumably modulated into chondroblasts that promoted endochondral ossification. It was concluded that trabecular bone remodeling plays an important role in healing of condylar fractures during the growth period.

Animals↗