Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Haversian System”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources
PubMed1980

Age changes in bone mineralization, cortical thickness, and haversian canal area.

Age-related changes in femoral cortical bone were quantified in an age-graded series of human cadavers. Variables included in this study were cortical thickness, bone mineral content, cortical bone density, summed Haversian canal area, Haversian canal number, and mean Haversian canal area. Females showed significant (P less than 0.05) decreases in cortical thickness, bone mineral content, and cortical bone density when plotted against age. Males exhibited slight nonsignificant declines for cortical thickness, bone mineral content, and cortical bone density. Both males and females exhibited significant (P less than 0.05) age-related increases in summed Haversian canal area values and Haversian canal number. Females as a group were found to exhibit significantly (P less than 0.05) larger mean Haversian canal area values compared with males, but the male group exhibited more Haversian canals per unit area of cortical bone compared with females. Intercorrelations between the bone mineral index and summed Haversian canal area and between cortical bone density and summed Haversian canal area define the role of increasing Haversian canal number and mean canal size per unit area of cortical bone as a factor in the reduction of bone mass as a function of age. Partial correlations between the bone mass variables and the variables assessing Haversian canal size and number further support this argument.

Adult↗
PubMed1982

Relationship between porosity and mineralization in the Haversian osteon.

Cortical bone, at the osteonal level, consists of three phases: mineral, organic, and pore or void phases. In osteonal segments excised from mature human cortical bone, organic volume percent is a constant. Determination of the mineral and organic phase densities present in these segments has led to defining a simple relationship between percent mineralization and void volume. Studies of a group of osteonal segments from 5 human tibias suggest that porosity of up to 22.7% may exist. This is much more than is suggested by histological examination, leading to the conclusion that the majority of the void phase is present as a dispersed porosity.

Bone and Bones↗
PubMed1979

Differences in intracortical bone remodeling in three aboriginal American populations: possible dietary factors.

Cross sections of intracortical bone revealed differences among three early American populations--Eskimo, Arikara, and Pueblo--in the frequency of a form of remodeling called, here, type II. This remodeling appears to occur exclusively within the walls of haversian canals of well-mineralized osteons. The populations are known to have differed in their nutrition. The Eskimo, with a high-protein diet, exhibited the most frequent type II remodeling, whereas the Pueblo, with a low-protein diet, showed the least. Type II remodeling probably reflects the physiological state of the group. Variation in frequency of classic intracortical bone remodeling was not apparent.

Adult↗
PubMed1979

Acute effects of Solanum malacoxylon on bone formation rates in growing rats.

The plant Solanum malacoxylon is responsible for a syndrome of hypercalcemia, soft tissue mineralization, and progressive wasting in South American cattle known as enteque seco or espichamento. There is evidence that a glycoside of 1,25-dihydroxycholecalciferol is the active principle in the plant. The basis for the hyperostosis seen in the disease is unclear. To study the acute effects on bone formation rates, 8-week-old rats were given an aqueous extract equivalent to 250 or 1000 mg of Solanum daily per os for 7 days. Bones were labeled by injection of fluochrome 2 days before the start of treatment and 2 days prior to sacrifice. Morphometric evaluation of undecalcified sections of caudal vertebrae revealed an increased amount of trabecular bone in both Solanum treated groups with no difference due to dose level. This was associated with an increase in the bone apposition rate on trabecular surfaces. No differences were found in the amount of osteoid seam width. Periosteal apposition rate and endochondral bone formation were also measured and no significant differences found. The findings indicate that acute stimulation of cell level bone formation on trabecular surfaces may play a role in the hyperostosis seen in the naturally occurring condition.

Animals↗
PubMed1975

Aging effects on osteon remodeling.

Analysis of partial cross sections of 101 human tibiae indicated that osteon remodeling in the outer cortex is affected by age. The frequency of resorption spaces remained constant throughout life suggesting no loss of osteoclast function with age. However, the frequency of both forming osteons and osteons which were structurally complete but not completely mineralized increased with age. This suggests that protein matrix synthesis by osteoblasts slows with age and that initial mineralization, possibly mediated by osteroblasts, and final mineralization, possibly mediated by osteocytes, becomes increasingly deficient with increasing age. The frequency of osteons which have dense (sclerotic) inner lamellae decreases with age. This supports a hypothesis that such lamellae are functional, perhaps representing a specialized, labile, mineral phase and that osteons having this feature become less frequent as part of the general degenerative changes associated with aging.

Aging↗
PubMed1975

A precision microdissection procedure for undecalcified bone thin sections.

A procedure is described for removing osteons from undecalcified, thin sections of bone. The method involves the use of a microdrilling machine in combination with a micromanipulator. The procedure allows a substantial reduction in the time required for microdissection over previously described methods while permitting the irregular contours of osteons to be followed with precision.

Bone and Bones↗
PubMed1976

Bone in dermatosparaxis. II. Chemical analysis.

Physical and chemical analysis of the organic matrix of dermatosparactic (D-) bone was performed to evaluate the implication of an alteration in the mechanical properties of procollagen fibers in the process of calcification. The D-diaphyseal bone contained less collagen and more hydroxyapatite than normal (N-) calf bone. Fractionated by centrifugation in a density gradient, D-bone was found to be composed of more than 80% weight of a highly calcified fraction while N-bone of the same age contained only 37% of this fraction. As compared to N-bone, the amount of organic matrix per unit volume of D-bone was increased in the least calcified fractions and reduced in the most mineralized ones. The newly formed matrix of D-bone contained an amount of collagen similar to the N-bone while the concentration of other glycoproteins was higher. Calcification was accompanied, in both types of bone, by a progressive reduction of glycoproteins and collagen; the diminution of collagen was higher in D- than in N-bone. The presence in D-bone of procollagen fibers with altered mechanical properties might be responsible for an excess of glycoproteins in the newly formed matrix. Calcium salt deposition in this matrix and progressive distension of the fibrous framework are two possible mechanisms by which hypercalcification of D-bone occurs.

Amino Acids↗
PubMed1976

Histomorphometric determination of formation rates of archaeological bone.

Archaeological rib samples were subjected to quantitative histologic analysis to determine rates of cortical bone formation. Histologic features are usually well enough preserved to permit the determination of mean annual Haversian bone formation rate averaged over the life span of the individual. Moreover, gross estimates of aging archaeological bone correlate well with histologic parameters expected for particular ages. Age-associated changes in bone histomorphology in extinct populations have remained essentially unchanged for at least 1,600 years. Bone formation rates determined for these populations agree with age-matched values determined for extant Homo sapiens. A relatively high frequency of pathologic conditions reported by others for the Ledders population may be reflected by the wide range of histomorphometric parameters present in the ribs of these individuals. On the basis of morphophysiologic relationships in extant populations, it can be assumed that mean annual osteonal creation frequency, and mean annual Haversian bone formation rate can be reliably determined in extinct populations. To our knowledge, this is the first time a dynamic physiologic parameter has been measured in an extinct population of H. sapiens.

Adolescent↗
PubMed1985

A low-angle X-ray diffraction analysis of osteonic inorganic phase using synchrotron radiation.

Using synchrotron radiation the low-angle X-ray diffraction method has been applied to single osteon samples to yield new data on the texture of the inorganic bone fraction. Two sample types--cylindrically shaped osteonic samples and osteonic radial hemisections--were prepared from longitudinal and alternate osteons at both the initial and final stages of calcification. The results indicate that the diffraction pattern is due to the inorganic phase, which reveals the same axial periodicity as native collagen fibrils and fits into the main band. No change is appreciable as osteons pass from the initial to the final stage of calcification. This means that when crystallites covering much more than a collagen axial period are observed under the electron microscope, they do not appreciably affect the calcified banding of collagen fibrils. The osteonic axis corresponds to the main direction of collagen orientation both in longitudinal and alternate osteons. The degree of orientation, however, is lower in alternate osteons than in longitudinal ones, where only few thin, incomplete transversal lamellae are found.

Adult↗
PubMedDate not supplied

Electrical signal transmission and gap junction regulation in a bone cell network: a cable model for an osteon.

A cable model is formulated to estimate the spatial distribution of intracellular electric potential and current, from the cement line to the lumen of an osteon, as the frequency of the loading and the conductance of the gap junction are altered. The model predicts that the characteristic diffusion time for the spread of current along the membrane of the osteocytic processes, 0.03 sec, is nearly the same as the predicted pore pressure relaxation time in Zeng et al. (Annals of Biomedical Engineering. 1994) for the draining of the bone fluid into the osteonal canal. This approximate equality of characteristic times causes the cable to behave as a high-pass, low-pass filter cascade with a maximum in the spectral response for the intracellular potential at approximately 30 Hz. This behavior could be related to the experiments of Rubin and McLeod (Osteoporosis, Academic Press, 1996) which show that live bone appears to be selectively responsive to mechanical loading in a specific frequency range (15-30 Hz) for several species.

Action Potentials↗
PubMed1999

Intracapsular hip fracture: increased cortical remodeling in the thinned and porous anterior region of the femoral neck.

It has been shown previously that the antero-inferior cortex is subjected to maximal tensile stress during a fall onto the greater trochanter. We have recently shown that in cases of femoral neck fracture, cortical thinning and porosity is greatest in the anterior and antero-inferior region of the femoral neck. To investigate whether this is due to increased remodeling, we have quantified surface-based parameters associated with Haversian remodeling in femoral neck biopsies from women with intracapsular hip fracture and post-mortem controls. Cryostat sections of chilled biopsies were reacted for either tartrate-resistant acid phosphatase (TRAP) or alkaline phosphatase (ALP) activity. Proportions of active canals were determined in each quadrant (inferior, anterior, superior, posterior) of the femoral neck. The biopsies were then embedded in methacrylate to permit histomorphometry using Goldner's and Solochrome sections. In the cases there was no significant increase in the proportion of canals undergoing remodeling in the cortex as a whole (p = 0.846), but the regional distribution of remodeling was markedly different from that in the controls. In the anterior cortex, the proportion of canals undergoing remodeling was increased by 56% (p = 0.0087); in contrast there was a relative decrease of 35% in the superior region (p = 0.0047). In the anterior cortex of cases there were 76% and 42% increases in the proportions of eroded (p = 0.019) and osteoid-bearing (p = 0.041) canals, respectively. In the superior region, the decrease in the proportion of remodeling sites was due to a marked decrease in canals with an osteoid surface (51%; p = 0.0031). Covariance analysis with cortical porosity as the dependent variable showed that porosity was significantly dependent on the regional distribution of eroded (p = 0.033) but not on the distribution of forming (p = 0.153) canals (R(2)adj = 0.51). Cellular levels of TRAP and ALP were significantly elevated in the anterior region of cases compared with the controls (TRAP 55%, p = 0.006; ALP 36%, p = 0.003). For the posterior and inferior regions there were no marked differences in cellular TRAP and ALP levels compared with control values. These data show that the increased cortical thinning and increased porosity we have previously observed in the anterior cortex in cases of hip fracture are associated with increased indices of Haversian remodeling. These findings are consistent with the hypothesis that, in cases of hip fracture, remodeling imbalance in the anterior cortex is a continuing process up to the time of fracture and is due to increased osteoclastic cellular activity associated with an osteoblastic response that is inadequate to prevent bone loss.

Acid Phosphatase↗
PubMed2003

Osteon remodeling dynamics in Macaca mulatta: normal variation with regard to age, sex, and skeletal maturity.

As research into bone maintenance and turnover is accelerated and expanded due to public health concerns about osteoporosis and other age-related changes and pathologies of bone, nonhuman animal models are becoming increasingly important as they allow for enhanced experimental manipulation and environmental control relative to humans. Old World Monkeys, such as the rhesus macaque, share physiological and developmental characteristics that make these primates particularly well suited to such studies. The purpose of this study was to characterize normal age and sex variation in osteon remodeling dynamics in skeletally immature and mature rhesus macaques. Femoral cross-sections from 75 Macaca mulatta were examined to evaluate the effect of age, sex, and skeletal maturity on osteon remodeling dynamics in this popular research primate. Results indicate that sex has a significant effect on osteon area (On.Ar), but generally is not an important contributor to normal variation in intracortical remodeling dynamics. Age and skeletal maturity, however, contribute significantly to variation in osteon population density (OPD), activation frequency (Ac.f), and bone formation rate (BFR), as is the case in humans. This study is the first to characterize normal age and sex variation in osteon remodeling in growing and adult rhesus macaques and its results support the use of this animal as a model for age-related changes and pathologies in the human skeleton.

Age Factors↗
PubMed2005

A histomorphometric study of cortical bone of the iliac crest in patients treated with glucocorticoids.

The effects of glucocorticoids on cancellous bone remodeling and structure are well documented but there are no reported histomorphometric studies in human cortical bone in glucocorticoid-treated patients. We have performed a histomorphometric analysis of iliac crest cortical bone in 14 patients treated with glucocorticoids, 9 females and 5 males, aged 18 to 48 years (34.1 +/- 7 years) (mean +/- standard deviation [SD]). The underlying disease was cystic fibrosis in 8 patients; asthma 3; and nephrotic syndrome; Crohn disease and inflammatory pseudotumor of the liver in one patient each. Results were compared with an age-matched control group of 10 premenopausal women and 4 men aged 22 to 38 years (30.1 +/- 4.8 years) who were not, however matched for underlying disease. Cortical bone indices were assessed by image analysis. Cortical width and area were similar in the two groups. However, cortical porosity, Haversian canal number, and density were higher in patients treated with glucocorticoids compared with controls (8.4 +/- 8.9% vs. 5.1 +/- 3.9%; P = 0.03) (45.9 +/- 23.2 vs. 31.9 +/- 24.4; P =0.003) (13.7 +/- 9.4 vs. 6.7 +/- 3.3/mm2; P = 0.00005). Haversian canal area did not differ significantly between groups. The mean wall width of the osteons, bone formation rate (microm2/microm/day) and mineral apposition rate (microm/day) were lower in treated patients compared to controls (48.8 +/- 7.1 microm vs. 59.8 +/- 12.9 microm; P = 0.01) (0.056 +/- 0.040 vs. 0.095 +/- 0.058; P = 0.05) and (0.59 +/- 0.12 vs. 0.75 +/- 0.11; P = 0.002). The proportion of canals with an eroded surface was lower in the treated compared with the control group, although this difference was not statistically significant. These results demonstrate that cortical porosity is increased in patients treated with long-term glucocorticoid therapy, due mainly to an increase in the number rather than size of Haversian canals. This may be because of increased bone resorption during the early stages of glucocorticoid therapy, in combination with long-term impairment of bone formation. Effects of the underlying disease on bone remodeling may also contributed to these changes and could not be excluded in the present study; since control subjects were not matched in terms of disease status.

Adolescent↗
PubMed2006

Indentation properties of young and old osteons.

The purpose of this study was to quantify differences in indentation modulus and microhardness between labeled osteons identified by epifluorescent microscopy and neighboring unlabeled osteons. In microradiographs and backscattered images, newly formed osteons appear more radiolucent (darker) than older osteons. This is ascribed to incomplete mineralization of the osteon. However, the mechanical properties of these young osteons are unknown. Nine femoral cross-sectional specimens were obtained from five skeletally mature dogs. Prior to death, the dogs received a pair of calcein bone labels. Labeled osteons were identified under an epiflourescent microscope. Bone specimens were transferred to a nanoindenter specimen holder, and the previous identified labeled osteons were located. Labeled (n = 102) and unlabeled (n = 101) osteons were examined by instrumented indentation testing. Indents were made to a depth of 500 nm at a loading rate of 10 nm/second. There were significant differences in the indentation modulus (P < 0.001) of labeled (10.02 +/- 3.61 gigapascal (GPa), mean +/- standard deviation) and unlabeled (15.11 +/- 3.72 GPa) osteons. Similar differences existed in microhardness measurements. Newly formed osteons had lower modulus (34%) and hardness (41%) than older osteons found in femoral cross sections. These data provide information on the indentation moduli of osteons during an early phase of mineralization compared to osteons that have completed mineralization.

Aging↗
PubMed2001

Prediction of cortical bone porosity in vitro by microcomputed tomography.

The high importance of intracortical porosity for mechanical strength of cortical bone has been established. The contribution of other parameters of microstructure such as osteon dimensions for strength is in discussion. The aim of this study was to evaluate the predictive value of microcomputed tomography (mCT) for porosity and other microstructural parameters of cortical bone in cortical bone biopsies. Femoral cortical bone specimens from the middiaphysis of 24 patients were harvested during the procedure of total hip replacement at the location where normally one hole (Ø 4.5 mm) for the relief of the intramedullary pressure is placed. In vitro intracortical porosity and bone mineral density (BMD) measurements by mCT were compared with structural parameters assessed in histological sections of the same specimens. A strong correlation was found between intracortical porosity measured by mCT and histological porosity (r = 0.95, P <0.0001). Porosity measured by mCT was also a strong predictor for other parameters describing dimensions of porous structures. BMD?1 was associated with osteonal area (r = -0.76, P <0.0001). We consider the measurement of porosity by mCT as a very potent procedure for assessing intracortical porosity and parameters related to porous structures of cortical bone nondestructively in vitro.

Aged↗