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At least 1,189 records · Page 66Linked to original sources
PubMed1991

Effects of exogenous porcine somatotropin (pST) administration on growth performance, carcass traits, and pork meat quality of Meishan, Pietrain, and crossbred gilts.

Seventeen to twenty-three females of lean (Pietrain, PI), fat (Meishan, MS), or intermediate genotype (PI x [3/4 Large White x 1/4 MS]), referred to as crossbred (CR), were injected between 60 and 100 kg live weight with 6 mg/d of porcine somatotropin (pST) and compared to similar numbers of control females receiving the vehicle only. Average daily gain increased similarly in the three genotypes (125 g/d). Feed conversion ratio tended to decrease to a higher extent in MS (-2.0 kg of feed/kg of gain) than in the other two genotypes (-1.1 and -.9 kg of feed/kg of gain for CR and PI, respectively). A significant genotype x treatment interaction was also observed for backfat thickness (BF) and fat, muscle, and bone development. Effects of pST in PI, CR, and MS pigs were, respectively, -6.2, -9.6, and -16.1 mm for BF and 3.0, 6.8, and 11.8% carcass muscle. The influence of pST on physical measurements of meat quality was rather low, although desirable effects (P less than .05) were obtained on the reflectance and water-holding capacity of PI and CR. Intramuscular fat content was reduced by approximately 1% in MS and CR but not in PI. The metatarsals of pST-treated animals had a higher water content (except in PI), a lower mineralization, and a lower breaking strength (except in MS). The existence of breed variations in the response to pST might result in changes of the relative merit of crossbreeding schemes.

Adipose Tissue↗
PubMed1995

Mutations in collagen genes resulting in metaphyseal and epiphyseal dysplasias.

Genetic mapping and positional cloning of genes, in which mutations lead to osteochondrodysplasias in humans and mice, combined with studies of transgenic mice with mutations in cloned genes, is providing novel and exciting insights into the molecular mechanisms of cartilage and bone development and growth as well as the basis for a variety of osteochondrodysplasias. Studies of mice with targeted disruption of c-src and c-fos have shown that these two genes have essential roles in the function and differentiation of osteoclasts. Combined mouse and human studies demonstrate that a unique extracellular matrix molecule (collagen X) in the mineralizing hypertrophic zone of growth plates is essential for normal growth plate function. Mutations in this molecule cause metaphyseal chondrodysplasia type Schmid (MCDS) in humans. Identification of the gene causing autosomal recessive chondrodysplasia in mice demonstrates that the quantitatively minor fibrillar collagen XI is essential for the cohesive properties of cartilage and the normal differentiation and spatial organization of chondrocytes in growth plates. Finally, mutations in all three collagen components of cartilage fibrils, collagens II, IX, and XI, have been found to cause a spectrum of clinical disorders, ranging from severe, perinatal lethal, osteochondrodysplasias to extremely mild conditions presenting themselves as a genetic predisposition to osteoarthritis.

Animals↗
PubMed1990

Effects of spaceflight on rat humerus geometry, biomechanics, and biochemistry.

The effects of a 12.5-day spaceflight (Cosmos 1887 biosatellite) on the geometric, biomechanical, and biochemical characteristics of humeri of male specific pathogen-free rats were examined. Humeri of age-matched basal control, synchronous control, and vivarium control rats were contrasted with the flight bones to examine the influence of growth and space environment on bone development. Lack of humerus longitudinal growth occurred during the 12.5 days in spaceflight. In addition, the normal mid-diaphysial periosteal appositional growth was affected; compared with their controls, the spaceflight humeri had less cortical cross-sectional area, smaller periosteal circumferences, smaller anterior-posterior periosteal diameters, and smaller second moments of area with respect to the bending and nonbending axes. The flexural rigidity of the flight humeri was comparable to that of the younger basal control rats and significantly less than that of the synchronous and vivarium controls; the elastic moduli of all four groups, nonetheless, were not significantly different. Generally, the matrix biochemistry of the mid-diaphysial cross sections showed no differences among groups. Thus, the spaceflight differences in humeral mechanical strength and flexural rigidity were probably a result of the differences in humeral geometry rather than material properties.

Animals↗
PubMed1987

Prolonging survival in vascularized bone allograft transplantation: developing specific immune unresponsiveness.

Vascularized bone allografts (VBAs) could be useful adjuncts to the clinical reconstructive surgeon's arsenal. These grafts are known experimentally to be subject to host rejection. One way to control the rejection problem would be to develop specific immune unresponsiveness via host conditioning. Using a proven reliable model in inbred rats for studying heterotopic VBA transplantation, recipient animals were conditioned preoperatively with third-party unrelated blood, donor-specific blood (DSB) alone and with cyclosporine, and ultraviolet irradiated donor-specific blood. The combination of DSB plus cyclosporine delayed rejection of grafts across a strong histocompatibility barrier for three to four weeks. However, rejection was delayed across a weak histocompatibility barrier for five to six weeks using this same host pretreatment. The implications are that specific immunosuppression, although possible, is difficult to achieve in VBA transplantation, and that such techniques will rely on tissue-matching to minimize the genetic disparity between graft and host.

Animals↗
PubMed1987

Growth of bone marrow cells on porous ceramics in vitro.

Following the transplantation of bone marrow cells to extra-osseous sites, bone formation occurs in those sites. This osteogenic potential of bone marrow cells might be utilized for filling defects in bone if they could be transported on porous ceramic materials. Before such an approach becomes feasible, it is important to know what happens to the cells in the presence of the ceramics that might be used. In order to investigate the interaction between bone marrow cells and ceramics, in vitro, a system for culturing bone marrow cells on ceramic materials has been developed. Bone marrow cells adhered well to the surface of calcium hydroxyapatite and tricalcium phosphate ceramics, and this was followed by the formation of fibrous tissue on and within the ceramics. These ceramics were compatible with bone marrow cells even in culture conditions in which there was a large surface area of ceramic interfacing with cells. The results support the proposal that calcium hydroxyapatite and tricalcium phosphate are appropriate as bone replacement materials. In contrast, calcium aluminate had an adverse effect on bone marrow cells when there was a high proportion of ceramic to culture medium. However, this effect was not present if the proportion of ceramic to culture medium was low. Therefore, a large amount of biodegradable porous calcium aluminate ceramic should not be used as an alternative to autogeneous bone grafting.

Aluminum↗
PubMed1995

Bone cell function, regulation, and communication: a role for nitric oxide.

A large array of factors serve as vital communication links between cells and the characterization, regulation, and mechanisms of action of such factors are topics of intense research efforts. Most intercellular messenger molecules which have been described over the years are represented by proteins, small peptides, amino acids or their derivatives, ions, lipid metabolites, or steroids. However, a small uncharged free radical, nitric oxide, has recently garnered much attention as a potent multifunctional signal molecule with widespread actions within and between diverse tissues. Biochemical, molecular, and regulatory studies of the family of enzymes responsible for nitric oxide synthesis, nitric oxide synthases, have established that there are at least three distinct isoforms of this enzyme which are differentially expressed and regulated in various cells or tissues. Modulation of these isoenzyme levels or activities by diverse signals is mediated via transcriptional, translational, and/or post-translational mechanisms, and consequently, alterations in such control may influence normal or pathological processes. Nitric oxide appears to exert pronounced effects on skeletal physiology and its production by various bone cells, elicited target cell responses, modulation by other signalling molecules (e.g., cytokines, hormones, fatty acid derivatives), and chemical interactions with other free radicals (e.g., superoxide anions, hydroxyl radicals) may form one important facet of the many complicated communication pathways controlling bone cell physiology and remodeling. Further cell and molecular studies are needed to address the precise roles that nitric oxide plays in bone development and in the formation and degradation of bone during ordinary bone metabolism. In addition, alterations in the regulation and action of the bone nitric oxide system as a function of certain bone disorders may be manifested by perturbations in bone integrity or mineral homeostasis. In this article, we review the current evidence implicating nitric oxide as an important messenger molecule in bone intercellular communication, speculate on potential roles for this radical in bone biology, and discuss possible future directions for advanced research into the function of nitric oxide in skeletal physiology.

Amino Acid Oxidoreductases↗
PubMed1997

The cervical spine in the skeletal dysplasias and associated disorders.

The cervical spine is an especially important area, not only for the diagnosis of the skeletal dysplasias, but also for the management of the patient. By the "cervical spine" I refer not only to the vertebral bodies and posterior elements of this region, but also to the neural elements contained within, especially the cervical cord. The spine is supported by a group of ligaments both anteriorly and posteriorly, with special fixation of the odontoid and C2 by a ligament which normally affixes it firmly to C1. Multiple things may go wrong with the development of the cervical spine. There may be abnormal development of the "vertebrae" in this region, ranging from hypoplasia to developmental failure and/or abnormal ossification of the cervical vertebrae; associated or unassociated odontoid hypoplasia; poor ligamental fixation of C2 resulting in C1-2 subluxation; abnormal development of the posterior processes; abnormal ligamental development or laxity with abnormal cervical kyphosis or lordosis; and, in the case of more fragile/brittle bone development (osteoporosis or increased bone density), fractures can lead to cervical spine problems. The skeletal dysplasias that involve cervical spine problems constitute about 35 of the 150 well-described disorders. These include certain families of disorders like the type II collagenopathies, as well as many individual disorders. It is very important for the clinician to be able to pilot patients through the various appropriate imaging modalities - conventional radiographs of the cervical spine; lateral flexion/extension views; CT; MRI - so that proper management and therapy will result.

Bone Diseases, Developmental↗
PubMed1999

Exposure to altered gravity affects all stages of endochondral cartilage differentiation.

Chondrogenesis has a number of well-defined steps: (1) condensation, which involves cell aggregation, adhesion and communication; (2) activation of cartilage genes, which is accompanied by rounding up of the cells and intracellular differentiation; and (3) production and secretion of cartilage specific matrix molecules. Our studies show that each of these steps is affected by exposure to gravitational changes. Clinorotation and centrifugation affected initial aggregation and condensation. In the CELLS experiment, where cells were exposed to microgravity after some condensation occurred preflight, intracellular differentiation and matrix production were delayed relative to controls. Once cartilage has developed, in rats, further differentiation (hypertrophy, matrix production) was also affected by spaceflight and hind limb suspension. For the process of chondrogenesis to proceed as we know it, loading and other factors present at 1g are required at each step of the process. This requirement means that not only will skeletal development and bone healing, processes involving chondrogenesis, be altered by long term exposure to microgravity, but that continuous intervention will be necessary to correct any defects produced by altered gravity environments.

Animals↗
PubMed2006

Biochemical bone markers in breast cancer.

Bone metastases, the most common metastatic manifestation of many cancers, including breast cancer and prostate cancer, contribute significantly to the pain and disability often associated with later stages of malignant disease. Although bisphosphonates have demonstrated efficacy in the treatment of metastatic bone disease (MBD), identifying patients most likely to develop bone metastases (and thus to benefit from treatment) is a challenge. In recent years, advances in understanding the pathophysiologic underpinnings of bone metastases have led to the discovery of several potential markers for dysregulation of bone coupling. Trials have been conducted to validate these biochemical markers and to explore their possible role in measuring efficacy of bisphosphonate treatment and of other metastatic bone therapies. In no area is this research more important than in the management of breast cancer. Although the value of these bone turnover markers is still unclear, and further research is necessary, results from these recent trials indicate some correlation.

Antineoplastic Agents↗
PubMed1997

Neutral lipids facilitate transfer of bone morphogenetic proteins and other noncollagenous proteins.

In the process of separation of bone morphogenetic proteins from bone matrix, lipids were found in unexpected amounts closely associated with noncollagenous proteins soluble in guanidine hydrochloride. Lipids representing 33.7-49.9% by weight were recovered with various solvents. Composites of noncollagenous proteins and lipids soluble in either chloroform- methanol or acetone implanted in the hindquarter muscles of mice induced the formation of large deposits of heterotopic bone. The protein-lipid aggregates formed microspherules which were stained by Sudan Black B. Implants of bone morphogenetic proteins and noncollagenous proteins-lipid microspherules stained with Sudan Black B induced bone development in the same manner as unstained delipidized bone morphogenetic proteins associated with noncollagenous proteins. Lipid-free osteocalcein, osteonectin, albumin and other bone matrix proteins did not induce bone formation or bind Sudan Black B. The more highly purified the noncollagenous proteins, with or without activity of bone morphogenetic proteins, the lower the level of binding with Sudan Black B. Acetone-soluble bone matrix lipids consisted chiefly of triglycerides, cholesterol and saturated short chain fatty acids, and included little or no phospholipids or monounsaturated fatty acids. Composites of recombinant bone morphogenetic proteins-2 and acetone-soluble lipids induced larger deposits of bone than implants of recombinant bone morphogenetic proteins-2 without acetone-soluble lipids. The hypothesis that an association of bone lipids with protein facilitates the local transport of bone morphogenetic proteins warrants further investigation.

Animals↗
PubMed2002

Upregulation of basal TGFbeta1 levels by EMF coincident with chondrogenesis--implications for skeletal repair and tissue engineering.

Members of the TGFbeta/BMP gene family regulate cartilage and bone development. These genes are re-expressed in bone repair and are thought to mediate chondro- and osteoprogenitor cell differentiation. These observations have led to a therapeutic strategy of introducing these growth factors into experimental cartilage and bone defects. Therapeutic efficacy, however, has been limited by diffusion or inactivation of these growth factors from the desired site and by the inability to deliver sustained concentrations of growth factors. This study demonstrates an increase in basal TGFbeta mRNA and protein levels in association with chondrogenic differentiation in endochondral ossification. mRNA is increased by 158%; protein by 23%, and cells immunopositive for TGFbeta by 343% at maximal TGFbeta expression. Importantly, the pattern of TGFbeta expression is preserved throughout the developmental sequence. Our data suggest that the exposure to a specific electromagnetic field (EMF) enhances, but does not disorganize, chondrogenesis and endochondral calcification as well as the normal physiologic expression of TGFbeta. The ability to increase TGFbeta at a moderately low dose for sustained periods of time without disorganizing its physiology suggests the ability to establish temporal concentration gradients of growth factors for the purpose of stimulating skeletal repair.

Animals↗
PubMed2003

Large cystic fibrous dysplasia of the temporal bone: case report and review of literature.

Fibrous dysplasia is an uncommon benign disorder of unknown aetiology. It most likely represents a disorder of normal bone development. As it may occasionally involve the temporal bone, and encroach on the middle cranial fossa, it is of interest to the neurosurgeon. Fibrous dysplasia of the cystic variety is very uncommon. We report a case of a large cystic fibrous dysplasia involving predominantly the squamous temporal bone. The radiology and histology are discussed, and its differentiation from other lesions.

Craniotomy↗
PubMed1999

Both AP-1 and Cbfa1-like factors are required for the induction of interstitial collagenase by parathyroid hormone.

PTH is a major regulator of calcium homeostasis by mobilizing calcium through bone resorption. We show that the expression of collagenase-3 (MMP-13), a member of the family of matrix metalloproteinases, required for the cleavage of collagens in the bone, is increased upon PTH injection in mice. A cis-acting element in the collagenase-3 promoter was identified which, together with AP-1, is required for induction by PTH. This element contains CCACA motifs which are required for binding of the 65 kDa osteoblast-specific splice variant of Cbfal. Introduction of mutations in this binding site that interfere with protein interaction also eliminates PTH inducibility and transactivation by Cbfa/ Runt proteins. While DNA binding activity of AP-1 is increased upon PTH treatment, high basal level of Cbfa/Runt binding activity is detectable in untreated cells which is not further increased by PTH, suggesting that AP-1 and Cbfal contribute to transcriptional activation through different mechanisms. In agreement with the critical role of both proteins defined in tissue culture cells, expression of collagenase-3 is reduced in mice lacking c-fos and is completely absent in cbfa1-/-embryos. These data provide the first evidence for a critical role of Cbfal, a major regulator of bone development, in PTH-dependent processes such as bone resorption.

Animals↗
PubMed1999

Experimental study of bone formation from autogenous periosteal graft following insulin-like growth factor I administration.

The present study evaluates the effect of insulin-like growth factor I (IGF-I) administration on bone formation following grafted periosteum. Twenty-four Japanese white rabbits were randomly assigned into one IGF-I administered group (1 mg for 14 days) and a second control group. Grafted periosteum taken from the tibia was placed under the submandibular muscles. At 14, 21, and 28 days following the operation, the grafted periosteum was extirpated and examined. Throughout all stages of the experiment, active bone formation was confirmed histologically and radiographically in both control and experimental groups. In addition, a micro-CT scan was used to observe three-dimensional micro structures in newly formed bone and to measure the trabecular bone thickness as a marker of bone development. As a result, a significant increase in bone formation in the IGF-I group was observed when compared with the findings in the control group. Trabecular bone thickness in the IGF-I group was significantly greater when compared with the control group at 14 days and 21 days following grafting (P < 0.01). At 28 days following grafting, there were no significant differences, suggesting that administration of IGF-I may play an important role in inducing bone formation from grafted periosteum in the early stages.

Animals↗
PubMed1983

The effect of prenatal protein-energy malnutrition on the development of mandibles and long bones in newborn rats.

To evaluate the role of gestational protein-energy malnutrition on fetal hard-tissue growth and metabolism, we measured several variables in the growth centres of mandibles and long bones of newborn rats. Control pups and pups of malnourished dams had approximately the same extent of reduction in body-weight, mandibular weight and long-bone weight. The malnourished group had more cells in the mandible although cell size was the same as that of controls. In contrast, in the long bones, the malnourished group had fewer cells than did controls whereas cell size was unchanged. Calcium content was the same in long bones of both groups, but was less in the mandibles of pups from malnourished dams. Ca metabolism as measured by 45Ca uptake was unchanged in the long bones, but was increased in the mandibles of the malnourished group shortly after birth. Calcification patterns at birth in these bones correlated well with alkaline phosphatase (EC 3.1.3.1) activity. These findings indicate that the mandibles and long bones of offspring are affected differently by protein-energy malnutrition during the mother's gestation. Prenatal nutritional stress resulted in a disturbance of the pituitary-adrenal system. Increased adrenal corticosterone could possibly be related to the different observed changes in bone metabolism.

Animals↗