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Compartment syndrome is well documented in the literature. Neoplasia as a cause is a rare. We report a patient with known metastatic malignant melanoma presenting with a compartment syndrome of the arm caused by a relatively slow growing, non-invasive metastatic deposit. This was excised and the patient made an uneventful recovery., (Copyright 2000 The British Association of Plastic Surgeons.)

Undifferentiated or differentiated human trabecular bone cells with osteogenic capacity in primary culture express oxytocin receptors (OTRs). OTR expression then persists upon differentiation to an osteoblast phenotype. A human epithelial osteosarcoma cell line, Saos-2, also expresses OTRs. Expression was determined both at mRNA and protein levels. Functional OTRs are evidenced by an increase in intracellular calcium concentration, [Ca2+]i, in response to 10 nM oxytocin (OT). An oxytocin antagonist (OTA) blocked this effect, demonstrating specificity for OT. OT also stimulated prostaglandin E2 (PGE2) synthesis in both confluent undifferentiated and differentiated human trabecular bone cells. This is the first report of OTR mRNA and protein expression and of prescribed OT signal pathways in osteoblastic cells. Since PGE2 has been shown to increase bone turnover in favor of bone formation, OT may be a new class of a bone anabolic agent.

The present study was performed to compare vascularized and nonvascularized onlay bone grafts to investigate the potential effect of graft-to-recipient bed orientation on long-term bone remodeling and changes in thickness and microarchitectural patterns of remodeling within the bone grafts. In two groups of 10 rabbits each, bone grafts were raised bilaterally from the supraorbital processes and placed subperiosteally on the zygomatic arch. The bone grafts were oriented parallel to the zygomatic arch on one side and perpendicular to the arch on the contralateral side. In the first group, vascularized bone grafts were transferred based on the auricularis anterior muscle, and in the second group nonvascularized bone grafts were transferred. Fluorochrome markers were injected during the last 3 months of animal survival, and animals were killed either 6 or 12 months postoperatively. The nonvascularized augmented zygoma showed no significant change in thickness 6 months after bone graft placement and a significant decrease in thickness 1 year after graft placement (p < 0.01). The vascularized augmented zygoma showed a slight but statistically significant decrease in thickness 6 months after graft placement (p < 0.003), with no significant difference relative to its initial thickness 1 year after graft placement. In animals killed 6 months after bone graft placement, both the rate of remodeling and the bone deposition rate measured during the last 3 months of survival were significantly higher in the vascularized bone grafts compared with their nonvascularized counterparts (p < 0.02). By 1 year postoperatively, there were no significant differences in thickness, mineral apposition rate, or osteon density between bone grafts oriented perpendicular and parallel to the zygomatic arch. These findings indicate that the vascularity of a bone graft has a significant effect on long-term thickness and histomorphometric parameters of bone remodeling, whereas the direction of placement of a subperiosteal graft relative to the recipient bed has minimal effect on these parameters. In vascularized bone grafts, both bone remodeling and deposition are accelerated during the initial period following graft placement. Continued bone deposition renders vascularized grafts better suited for the long-term maintenance of thickness and contour relative to nonvascularized grafts.

Torsional injuries may be a precursor to intervertebral disc degeneration, but published rabbit models indicate a latent time of 6 months. We describe a rabbit model in which instability and disc degeneration appear within 3 months. Sixty-five male New Zealand rabbits underwent presurgical irradiation to inhibit heterotopic bone formation. Control animals then underwent either a soft-tissue release or facetectomy and capsulotomy, whereas experimental animals received surgery and an acute 30 degrees torsional lumbar injury. Capsulotomy, as well as facetectomy without torsion, failed to effect disc degeneration. However, the rabbits that received torsion exhibited clear indications of degenerative disc changes (thinning, increased PLA2 levels, and decreased nucleus pulposus volume) within 60-90 days. The observations associate disc degeneration with a destabilizing acute torsional injury.

The mechanism mediating the chronic pain associated with lumbar disc degeneration may involve neurotransmitters elaborated by dorsal root ganglion (DRG). This hypothesis has been tested in an applicable rabbit model of disc degeneration. Twenty control male rabbits underwent a soft-tissue release; 20 experimental rabbits sustained a facetectomy and capsulotomy and received an acute torsional lumbar injury. The levels of calcitonin gene-related peptide, vasoactive intestinal peptide, and substance P were measured in the DRG, spinal cord, and disc at 10, 30, 60, and 90 days postoperatively. Torsional injury was associated with a statistically significant increase in most DRG and spinal cord neurotransmitter values after 60-90 days. These points in time marked the periods of maximum biomechanical instability and disc narrowing. Such data support concepts about the association between chronic lumbar spinal instability, disc degeneration, and pain.

Because exposure to positively charged dextran resin (PCDR) inhibits the growth of cultured rat and human bone cells, we tested the hypothesis that PCDR might inhibit bone repair in vivo. Central physeal defects were created by drilling 3.0-mm holes from the proximal tibial plateau into the metaphysis. The defects in left tibiae were packed with neutral resin (control); those in right tibiae were filled with PCDR. At the end of the 1st, 2nd, 3rd, and 10th postoperative weeks, the outcomes were quantitated by documenting the percent trabecular bone volume within the defect. The PCDR-filled defects showed a significant decrease in trabecular bone formation as early as the 2nd week. By the 10th postoperative week, formation of trabeculae had been reduced by nearly 40%. The inhibition conferred by PCDR suggests that the resin could be used as a suppressive interpositional material.

We assessed the possible association between an aggressive intercondylar notchplasty and histopathologic, radiographic, and gait changes to the knee. Three groups of six adult greyhounds were observed for 6 months. Group I dogs had a sham operation. Group II dogs had a 4-mm notchplasty of the lateral femoral condyle where it articulates with the lateral tibial spine. Group III dogs had a 7- to 8-mm notchplasty of the lateral femoral condyle to simulate the long-term effects of an overly aggressive notchplasty. Force plate gait analyses were not significantly different for any dogs at 3 and 6 months. Histopathologic studies (hematoxylin and eosin and safranin O stains) revealed notchplasty area remodeling with a thin layer of lamellar bone covered by fibrous connective tissue. Both Group II and III dogs had significant loss of lateral femoral condyle and trochlear groove articular surface proteoglycans. The radiographic notch width index remained unchanged throughout the study for Group I; the indexes increased immediately after surgery in Groups II and III because of the notchplasty, but after 6 months these values returned to near-preoperative measurements. An aggressive intercondylar notchplasty caused articular cartilage histopathologic changes at 6 months consistent with those found in knees with early degenerative arthritis. Significant refilling of a non-impinged notchplasty occurred by 6 months after surgery. Our results raise concern about the effects of aggressive intercondylar notch widening in humans.

The putitive bone-sparing effect of alendronate was tested in two animal models of osteopenia: estrogen-deficient female rats and glucocorticoid-treated male rats. In the first study, 18 female Sprague-Dawley rats, 4 months of age, were ovariectomized (OVX), and an additional 6 rats were sham-operated. The OVX rats were treated with either vehicle, 17beta-estradiol (E2) (100 microg/rat/week, s.c.), or alendronate (1 mg/kg/day, on alternate days, orally). In the second study, 24 8-month-old male Wistar rats were treated with either vehicle, methyl prednisolone (7 mg/kg once a week, s.c.), prednisolone plus testosterone (16 mg/kg once every 3 weeks, i.m.), or prednisolone plus alendronate (20 microg/kg twice a week, s.c.). Prior to treatment and at the end of the 6-week treatment period, bone mineral density (BMD) of the lumbar spine was measured by dual energy x-ray absorptiometry, and mean femur weights were calculated. The OVX rats had subnormal BMD (-3.91 +/- 1.0% vs control +5.19 +/- 3.92%, P < 0.05) and femur weights (720 +/- 6 mg vs %; 746 +/- 11 mg, P < 0.05). OVX-induced bone loss was completely abolished by the administration of E2 (7.01 +/- 2.32%, P < 0.005; 748 +/- 6 mg, P < 0.01), or alendronate (24.2 +/- 2.73%, P < 0.0001; 779 +/- 11 mg, P < 0.001). In the second study in older male rats, glucocorticoids significantly decreased BMD (-9.70 +/- 3.44% vs -1.10 +/- 1.75%, P < 0.05), and femur weight (1070 +/- 14 mg vs 1180 +/- 24 mg, P < 0.01). Concomitant administration of testosterone (BMD 4.23 +/- 1.84%, P < 0.005; femur weight 1260 +/- 56 mg, P < 0.02), or alendronate (BMD 8.18 +/- 1.36%, P < 0.001; femur weight 1360 +/- 50 mg) with prednisolone, abolished the corticosteroid-induced bone loss. Bone histomorphometry showed a 34% loss of trabecular bone volume in glucocorticoid-treated rats (P < 0.05), which was prevented with both testosterone and alendronate therapies. However, at the doses used in both models, alendronate was more efficacious than either E2 or testosterone in increasing BMD and femur weight. In summary, this study demonstrated that alendronate therapy is highly effective in counteracting the osteopenia of OVX and glucocorticoid therapy.

Purpose: This study tested the hypothesis that a significant amount of the new bone produced by heterotopic periosteal autografts is derived osteoinductively because proliferating periosteal cells express the bone morphogenetic protein (BMP)., Materials and Methods: Rabbit ulnar and radial periosteum were autografted as free grafts (FGs) to the forelimb musculature, and as millipore diffusion chambers grafts (MDCGs) to the rectus abdominus muscle. The grafts were recovered at 3, 5, 7, 14, and 28 days postoperation, fixed in 4% paraformaldehyde, demineralized in 0.6N HCL, and 4.0 microns paraffin-embedded sections were immunostained with monoclonal antibody against recombinant human (rh) BMP-2., Results: Sections from FGs recovered 5 to 28 days postoperatively exhibited cartilage and bone; fibrous tissue, cartilage, bone, and osteochondroid differentiated within MDCGs. Although BMP-2 was expressed by mesenchymal cells, osteoblasts, osteocytes, and osteoclasts, none of the MDCGs produced the osteoinductive signature of transmembrane bone formation., Conclusions: These observations indicated that the larger fraction of the new bone produced by heterotopic periosteal autografts is derived from the graft cells.

Following the signal observation that contact with positively charged dextran resin (PCDR) inhibited the growth of cultured mammary (Hs578T and MDA-MB-231), pancreatic (H2T), and myeloma (RR-658) tumor cell lines, studies were developed in the hamster cheek pouch model using hamster H2T pancreatic tumor cells to determine if the antiproliferative effect of PCDR could inhibit tumorigenesis. In these studies, the control population represented groups injected with H2T cells alone or in combination with either neutral or negatively charged resin. When cells (5 x 10(2) to 1 x 10(5)) and PCDR were administered simultaneously, the tumor incidence (percent engraftment) and growth of tumors that already had been established were significantly reduced. When PCDR was injected into already established 1-35-mm2 H2T tumors (engraftment for 21 days = 96%), the resin suppressed the growth of the smallest tumors (< 10 mm2). In none of these trials was the somatic growth of the host hamsters affected. PCDR contact with H2T cells in vitro for 4 days or used to treat growing solid tumors for 72 days significantly reduced cellular ornithine decarboxylase activity. While the mechanism of PCDR action has not been established, the observations have implications for in vivo tumor therapeutic models.

To determine the role of immobilization in the pathogenesis of burn-associated bone disease, we selected the sheep as a model to study the effects of burn injury compared with a sham-burned control group. Seven of the sheep were subjected to controlled 40% flame burn, and seven underwent anesthesia with arterial and venous cannulation but without burn. After labeling newly formed bone with tetracycline and calcein, the sheep were killed 2 weeks after burn or sham burn, and the iliac crest and lumbar vertebrae were analyzed for histomorphometry. Analysis failed to demonstrate a significant reduction of bone formation rate in the burned sheep. Osteoid area and surface and osteoblast surface, which correlated significantly with bone formation rate (r = 0.49, p < 0.025), were reduced in the burned sheep. Results suggest that immobilization may play a primary role in the pathogenesis of burn-associated bone disease, but the presence of differences in other histomorphometric features indicates the bone disease is multifactorial.

Previous studies have shown the osteogenic potential of negatively charged Sephadex beads when used to heal osseous defects in an animal model. The present study examined the effect of adding the growth factors transforming growth factor-beta1 and basic fibroblast growth factor to negatively charged Sephadex beads and neutral (non-osteogenic) Sephadex beads in a critical size calvarial defect in rabbits. New Zealand White rabbits were divided into six groups of five rabbits; 15 mm parietal defects were created and filled with either negatively charged Sephadex beads (three groups) or neutral Sephadex beads (three groups). Each group received either 2 microg of transforming growth factor-beta1, 1 microg of basic fibroblast growth factor, or buffer (control). Animals were killed at 5 weeks, and their calvaria were submitted to plain radiographic and histomorphometric analyses. Defects treated with negatively charged Sephadex beads produced significantly more new trabecular bone than neutral Sephadex beads (p < 0.01), whereas the neutral beads treated with transforming growth factor-beta1 formed significantly more bone than controls. The addition of transforming growth factor-beta1 to negatively charged beads resulted in near closure of the craniotomy defect. The application of transforming growth factor-beta1 to this model resulted in significantly more ectopic bone (p < 0.01) outside the defect on the dural and periosteal surfaces. Basic fibroblast growth factor, in the dose used, appeared to have an inhibitory effect on new bone formation fostered by negatively charged Sephadex beads. This study suggests that the addition of transforming growth factor-beta1 to the known osteoconductive matrix of negatively charged Sephadex beads may be therapeutically useful in nonhealing bony defects.

In 13 New Zealand White rabbits with a mean age of 6 months, vascularized bone transfers incorporated as paired auricular anterior myo-osseous flaps were harvested; they were placed in either an inlay or an onlay position relative to the zygomatic arch. The onlay bone transfers were placed either in full contact or in partial contact with the zygomatic arch. The animals were sacrificed 1 year after transfer. At 1 year, the inlay transfer simulated the adjacent zygoma in width and thickness. Onlay full contact transfers maintained significant aug mentation in thickness of the zygoma, while the onlay partial contact transfers did not; the thickness of the augmented zygoma in the onlay full contact subgroup was significantly greater than that in the onlay partial contact transfers. The onlay partial contact grafts had remodeled into the zygoma in bone contact, where the orientation of mismatched osteons within the bone transfers had transformed to match that of the native zygoma. In areas of bone contact between the onlay and the host bone, full-thickness conversion from a cortical to a trabecular architecture had occurred in both the transfer and host bones. These findings have numerous implications regarding mechanisms that could be exploited clinically to optimize the survival of a bone transfer; they also raise questions regarding alteration of the recipient bed after placement of an onlay bone transfer.

We previously reported that bone marrow stromal cells produce insulin-like growth factors (IGF-I and -II), and that medium conditioned by marrow stromal cells stimulates osteoblast proliferation in vitro. The present study employed the rat tail-suspension model to unload the hindlimbs. It was designed to test the hypothesis that the development of osteopenia or osteoporosis could be due to a deficit in the osteogenic function of marrow stromal cells. Although tail suspension suppressed body weight during the first 3 days of an 11-day pair-fed study, the overall weight gain recorded by these animals was normal. Nevertheless, bone growth was inhibited by suspension. Similarly, the total adherent marrow stromal cell population harvested from the femurs and tibias was decreased by tail suspension, and only half the normal number of fibroblastic stromal cell colonies grew when they were cultured. The proliferation of alkaline-phosphatase-positive cells in the stroma was also inhibited. Northern hybridization revealed that the messenger RNA level for transforming growth factor-beta 2 and IGF-II in stromal cell was reduced by tail suspension. The production of IGF-II by marrow stromal cells was also decreased. The steady-state level of five different transcript sizes of IGF-I mRNA was altered differentially by tail suspension. Osteopontin mRNA was also reduced in marrow stromal cells from tail-suspended rats compared with the normal rats. These data suggest that skeletal unloading not only alters the mRNA level for growth factors and peptide production, but also affects the proliferation and osteogenic differentiation of marrow stromal cells. These changes may be responsible for the reduced bone formation in osteopenia and osteoporosis.

A C-terminal analog of parathyroid hormone-related peptide (PTHrP), PTHrP(107-139), was found to stimulate cAMP production in three osteoblast cell preparations. The effect was studied most extensively in ROS 17/2.8 cells. The effect was dose-related and comparable in magnitude to that produced by PTHrP(1-34), but potency was lower. The functional significance of the cAMP effect is unknown, but preliminary findings indicated that PTHrP(107-139) also inhibited osteopontin mRNA levels in ROS 17/2.8 cells treated with peptide for 48 h. The results suggest that the carboxy-terminal region of PTHrP may play a role in bone metabolism by influencing osteoblast activity.

The osteogenic response to subperiosteal injection of negatively charged ion exchange resins was compared in the tibiae of one-month and 16- to 22-month-old rats. The resins were administered either in the form of beads (CM Sephadex) or as particles (CM cellulose, carboxymethylcellulose), and the animals were killed at two weeks and at one month after injection. Histologically, the resins did not produce an inflammatory response. Periosteal bone formation was observed wherever resin was in contact with bone, and in the resin bed the connective tissues that invested the charged materials ossified within the first month. Marrow spaces commonly formed where periosteal growth was most rapid. The osteogenic effect was independent of resin conformation, and it was more pronounced in the younger rats.

The adjunctive role of demineralized bone matrix (DBM) in enhancing the incorporation of segmental freeze dried (FD)-allogeneic bone grafts has been studied in the rabbit ulna and fibula. The studies compared the healing patterns of fresh segmental autografts, FD-allografts, DBM-allografts, and FD-allografts supplemented at the graft-host junctions with FD- or DBM-allografts as particulates (ulna) or as segmental struts (fibula). The outcome was evaluated at five and ten weeks by a radiologic score, by biomechanical properties (breaking strength, energy to failure, stiffness), and histology. The ulnar autografts healed most rapidly (ten weeks = 100%), followed by DBM allografts (60%). By all criteria, FD-allografts were poorly incorporated (20-40%), and the process was not improved by supplements of FD- or DBM-particulate/strut bone. Histologically, the DBM component of composite fibular strut grafts was osteoinductive and united with host tissues within 35 days. The contiguous FD-allograft struts were not incorporated, showing fibrocartilaginous nonunions and resorptive foci. While the addition of DBM does not protect FD-allograft integrity in the rabbit, segmental mineralized FD-allografts could provide mechanical support for some intervals until, in such composite grafts, osteoinductive processes produced biomechanically competent new bone.

The anatomical relationships between the fiber tracts and bone lining cells within the rat calvarial periosteum have been studied by electron microscopy. Classical Sharpey's fibers were not observed in this location. Rather, thin unmineralized fibers originating from the periosteum traversed the cambial layer and passed to the bone surface between individual osteoblasts or groups of osteoblasts. The organizational relationship suggests that the osteogenic calvarial cell populations are compartmentalized into domains that might be particularly sensitive and responsive to the biomechanical forces of masticatory muscles.

Decreased muscular activity results in weakness and muscular atrophy. Coincident with this protein catabolic state is glucose intolerance and hyperinsulinemia. Rats were tail suspended for 7 to 14 days to accomplish unloading of the hindlimbs. Insulin resistance was documented in these animals by a 14 day tail suspension-related 26% increase in serum glucose in spite of a 253% increase in serum insulin concentration. Microsomal membranes were prepared from hindlimb muscles and specific binding of insulin and insulin-like growth factor I (IGF-I) were determined in these membranes. Insulin binding was decreased by 27% at 7 days and by 21% at 14 days. In contrast, IGF-I binding was unchanged at 7 days and was increased by 24% at 14 days. Liver membrane insulin receptors also had declined by 14 days of suspension, suggesting that the change in insulin receptors was a generalized, humorally-mediated phenomenon. These data suggest that tail suspension in rats results in insulin resistance, hyperinsulinemia, a decline in insulin receptors in liver and muscle, and a relative increase in muscle membrane IGF-I receptors. These data are consistent with the hypothesis that resistance to insulin's effects on protein metabolism in skeletal muscle may contribute to the protein catabolism associated with decreased muscular activity.

The pathogenesis of nutritional rickets is not well-understood. While the etiologies include deficiencies of vitamin D, calcium (Ca) or phosphate (PO4), and perhaps aluminium toxicity, the role these nutrients play in the development of tissue level anomalies characteristic of rachitic cartilage and bone has yet to be defined. Reported alterations in the biochemistry of rachitic bone and cartilaginous matrix which could adversely affect mineralization and endochondral ossification are of questionable significance since the tissues mineralize rapidly when exposed to Ca and PO4 salts in vivo and in vitro. The low Ca and PO4 concentrations of the extracellular fluid (ECF) bathing rachitic cartilage and bone matrix suggest that local mechanisms operate to impair mineralization. In healing rickets, the Ca and PO4 content of these tissue fluids increases in the same time-frame it takes to experimentally remineralize the matrices. However, it is not certain what determines the Ca and PO4 content of the ECF. Cytokines which may play a role in the cellular regulation of Ca and PO4 and maintain processes which contribute to normal patterns of endochondral ossification could provide a mechanism common to the pathogenesis of rickets from a variety of causes.

A large animal model to assess fetal fracture repair and the ability to close excisional bony defects is presented. Incisional and excisional ulnar fractures were made in 14 midgestation fetal lambs, harvested at serial time points, and subjected to high-resolution low-kilovolt magnification radiographs, magnetic resonance imaging scans, and histologic analysis. Fetal fracture healing was characterized by early closure of excisional defects and rapid fracture healing with minimal or no soft-tissue inflammation or callus formation. Magnetic resonance imaging scans of the fractures revealed a characteristic pattern compatible with the histologic findings, namely, minimal inflammation in soft tissue adjacent to the fracture site. Histologic and magnification radiographic findings indicated that complete bony repair occurred within 21 days in incisional defects and within 40 days in excisional defects. In both cases, healed fetal bone resembled normal bone matrix. Excisional defects, including periosteum, of greater than three times the width of the bony cortex closed rapidly with virtually normal-appearing bony matrix and with minimal or no callus formation.

Previous studies led us to demonstrate in pathological situations that the fibroblast, not the macrophage, was the terminal maturation step of the HLA-DR monocyte and that the entire process came under T-lymphocyte control. Fibrosis which developed under immunosuppressive treatment (cyclosporin) after organ transplantation is an illustration of these in vitro observations. The present in vitro study was undertaken in order to investigate whether or not this transformation process takes place under physiological conditions and if so, the nature of the T-lymphocyte control. We report that normal HLA-DR monocytes/macrophages are able to secrete type 1 collagen and to differentiate into neo-fibroblasts. However, contrarily to what happened in pathology, only a few neo-fibroblasts developed transiently. The addition of conditioned medium (CM) from activated T-lymphocytes greatly enhanced the transformation process. Counteracting this CM effect, cell-to-cell contact between neo-fibroblasts and T-cells resulted in the loss of fibroblastic shape. The 'end-result' macrophage engulfed numerous lymphocytes giving rise to a multinucleated cell. This giant cell no longer adhered to the slide and died. The question is raised as to whether the process observed in vitro is involved in vivo in tissue repair. We also report that HLA-DR monocytes and the neo-fibroblasts which derive from them are able to secrete, in addition to type 1 collagen, a variety of proteins such as uromodulin, amyloid-beta peptide, alpha-fetoprotein and carcinoembryonic antigen. In cystic fibrosis we previously reported a high level of uromodulin production by HLA-DR monocytes differentiating towards the fibroblastic phenotype. Pathologies characterized by excessive production of either alpha-feto-protein, carcinoembryonic antigen, beta-amyloid protein (Alzheimer's disease) should be investigated, taking into account the involvement of HLA-DR monocytes and their possible uncontrolled differentiation into neo-fibroblasts.

Fibroblast-like marrow stromal cells are believed to play a role in the maintenance of osteoblast populations at the marrow-bone interface. We now report that this interaction may be very specific. Stromal cell conditioned medium (SC-CM) stimulated DNA synthesis and proliferation in culture of neonatal rat calvarial osteoblasts at low concentrations (1.25-5%), but was inhibitory at 10%. At growth promoting effective concentrations, the activity of osteoblast alkaline phosphatase was decreased. This action was selective since SC-CM failed to promote the growth of rat calvarial fibroblasts. Characterization of the SC-CM indicated the cells produced IGF-I and -II and a wide range of molecular weight fractions with putative stimulatory action (FPLC analysis using Superose 12 and 6 gel permeation columns). HPAE-PAD analysis showed that some elements were glycosylated, and the composition suggested the presence of N- and O-linked oligosaccharide chains. Because rat marrow stromal fibroblast-like cells produce a number of osteotropic factors which affect calvarial osteoblast growth, these interactions may be important to considerations about the etiology of the osteoporoses.

We describe here two pathological situations, osteomyelosclerosis and Engelmann's disease, in which HLA-DR blood monocytes modulate to the fibroblastic class, in long-term culture. Monocytes/macrophages were identified by immunofluorescence, using monoclonal antibodies against surface markers (Leu M3, CD 68, and HLA-DR) and the neo-fibroblasts by electron microscopy and immunofluorescence using monoclonal antibodies against a cytoplasmic enzyme specifically involved in the synthesis of collagen (5B5). Macrophages makers were found on the neo-fibroblasts, whereas HLA-DR macrophages expressed the cytoplasmic marker 5B5. Since osteoblasts are classically derived from fibroblasts, the significance of the in vitro differentiation of monocytes/macrophages into fibroblasts to the in vivo mechanism leading to excessive osteoblastic proliferation in both osteomyelosclerosis and Engelmann's disease, is discussed. The possible involvement of this pathway leading from monocytes to fibroblasts and osteoblasts in the normal process of bone modeling and remodeling in questioned.

Experiments were carried out to determine the ability of female rats with poorly mineralized skeletons to increase bone mineralization in response to increased dietary Ca consumption. We specifically addressed this question with regard to two different periods of the life cycle: the period of sexual maturation (6-9 weeks of age), and in animals that had attained adult rates of skeletal mineralization (100 days of age). We found that at both stages, increased dietary Ca consumption resulted in increased trabecular bone volume and total bone Ca. In the younger animals, it was found that dietary history influenced the disposition of bone mineral. Animals that were initially Ca-deprived exhibited increased trabecular bone and decreased cortical thickness compared to animals continuously fed 0.5% Ca. Ovariectomy of mature animals reduced but did not eliminate the response to increased Ca intake.

This study tested the capacity of fluoride (F) to prevent the disuse-associated reduction in bone formation/growth. Suspending young male Wistar rats by the tail for 2-2.5 weeks reduced femoral cortical (P less than 0.05) and trabecular (P less than 0.01) bone areas. Tetracycline labelling showed that the decrement in cortical area was largely due to a reduction in the percent periosteal mineralizing surface (PsMS). Periosteal mineral apposition rate (PsMAR) was not affected. Endosteal mineralizing surface (EsMS) and mineral apposition rate (EsMAR) were significantly stimulated spontaneously during the second week of suspension. F treatment (5 mg/kg/day i.p.) prevented the loss in bone area, and established a trend toward increased PsMS without affecting EsMS and EsMAR. None of these changes are associated with alterations in serum Ca, P or osteocalcin. F treatment in hypokinetic animals caused a decrease in serum PTH (-21% compared to control; P = 0.001). We conclude that F prevents the development of hypokinetic osteopenia in rats.

Progressive tissue expansion induces significant gross, histologic, and bony changes in skulls and long bones of neonatal miniature swine. These bony changes consist of erosion underlying tissue expanders, with bony lipping and bone deposition at the periphery of the expander. Cranial suture lines underneath expanders appear effaced and convoluted. Serial CT scans reveal decreased bone thickness and volume (p less than 0.02) but identical bone density (p = 0.60) beneath expanders. Increased bone volume and thickness occur at the periphery of expanders (p less than 0.02). Bone density (CT number) is unaffected by tissue expansion in both cranial and long bones. These findings have histomorphometric correlates: Osteoclastic bone resorption occurs underneath expanders with periosteal reaction at the periphery of expanders. Cranial sutures are similarly affected, but no cranial synostosis results. No changes to the inner table of the skull or stigmata of increased intracranial pressure were observed either in CT scans or in behavioral changes in long-term animals. The pathophysiology of bony changes is a remodeling effect, not one of simple pressure deformation. Increased bone resorption and complete inhibition of bone formation occur until the pressure is removed. Cranial bone is significantly more affected than long bone. After removal of the expanders, reparative bone remodeling begins within 5 days and nearly complete healing of the cranial defects occurs within 2 months (p less than 0.02). No plagiocephaly results despite early coronal suture changes. On the basis of this study, we conclude that tissue expansion causes significant but reversible effects, readily monitored by high-resolution CT scans, on neonatal and infant cranial and long bones.

This chronotherapeutic study has revealed no clear evidence to support the concept that calcitonin promotes bone formation in intact or OVX'd rats. Rather, the efficacy of CT-impaired bone resorption appeared to be optimal in OVX'd rats treated during the daytime, and least effective during the first half of the environmental dark span. These findings indicate a benefit for calcitonin chronotherapy in this animal model where the cellular kinetics resemble those documented in early development of postmenopausal osteoporosis.

The bones of adult rats became progressively osteopenic 1 to 5 weeks following jejunoileal bypass or resection. These changes were accompanied by increased levels of metaphyseal enzyme activities as well as by loss of histochemically identifiable osteoid. Osteoid tissue and the ability to mineralize skeletal collagen were recovered more rapidly and fully in the resection group than in the bypass group. Metaphyseal alkaline phosphatase concentrations increased in both groups coincident with the elevated lysosomal enzymes levels, and the skeletons showed a calcium deficit (low Ca/HOPr ratio) within the first 3 weeks. In resected rats the osteopenia and bone blood chemistry were consistent with hyperparathyroidism secondary to impared Ca absorption. In bypassed rats the results suggest that the osteopenia might be related to the release of a "resorptive factor" from the excluded intestinal segment.

Quantitative studies of blood flow (hydrogen washout technique) and bone mineralization rate (tetracycline labeling) were performed in the ilium of 23 immature dogs before and after Salter innominate osteotomy. The vascular anatomy, blood flow rate, and mineralization rate (appositional bone growth) on the roof of the acetabulum were disturbed after operation. Radiographic healing and normal patterns of circulation to the ilium were partially restored within two weeks and completely restored after six weeks. The data suggest that a single iliac osteotomy is without long-term consequence to the viability of acetabular bone.

Treatment of mice (some bearing Lewis Lung tumors), with penicillin (PEN) at 500 mg/l drinking water for one week prior to treatment with misonidazole (MIS), resulted in: the elimination of their anaerobic cecal flora; a decrease in MIS-induced neurotoxicity; an increase in pharmacological exposure to MIS; a decrease in MIS chemopotentiation; a probable increase in MIS radiosensitization; an increase in MIS induced hypothermia. Assuming no chemical interaction between PEN and MIS, these observations indicate that the intestinal microflora can influence the activity of MIS in vivo. Therefore their influence should be considered in all sensitizer-related studies in vivo. The observed reduction in the neurotoxic but not the radiosensitizing potential of MIS following PEN treatment indicates a therapeutic benefit.

Meal timing protocols were used to probe the circadian regulation of DNA and protein synthesis in the rat tibia. Two groups of 4-week-old rats were entrained to 12-h light, 12-h dark cycles (light, 0800-2000 h; darkness, 2000-0800 h) for 4 weeks. One group was fed for 4 h at the onset of the light span (EL). The other group was fed for 4 h at the onset of the dark span (ED). Forty-eight hours before death, the rats were injected ip with 0.015 microCi/g BW [14C]proline [collagen and noncollagen protein (NCP) synthesis], and they received 0.25 microCi/g BW [3H] thymidine (DNA synthesis) 1 h before death. Groups of 10-12 rats were bled from the abdominal aorta at 4-h intervals under light ether anesthesia (1-2 min/rat) during 2 consecutive 24-h periods, and the tibias were then biopsied and frozen in liquid N2. Serum samples were analyzed for calcium, inorganic phosphorus, and immunoassayable levels of corticosterone (CS), PTH, and calcitonin. Epiphyseal cartilage and metaphyseal and diaphyseal bone were analyzed for DNA and acidic pepsin-digestible collagen. Chronograms indicated that DNA synthesis in cartilage and bone, along with serum CS, showed two approximately equal and positively correlated peaks, with the cycles for rats fed EL vs. ED being in approximate antiphase. The fit of a 12-h cosine curve was statistically significant in all cases (P less than 0.01). The acrophase peaks were: EL, 0800 and 2000 h; and ED, 1600 and 0400 h. These patterns were unrelated to those for NCP and collagen synthesis. EL and ED relationships for NCP synthesis were also antiphasal. A statistically significant circadian rhythm of collagen synthesis was detected in cartilage and bone of ED-fed rats (peak, 0800 h; nadir, 2400 h). In EL-fed rats, the 0800 h peak alone was muted. No consistent correlations were observed between serum calcium and phosphorus chronograms and those of cartilage and bone collagen and DNA synthesis. The results suggest that physiological alterations of CS in vivo serve to modulate cartilage and bone cell proliferation, but they do not seem to regulate the phasing of the net collagen synthetic rhythm.

Microradiographs of 5-micron sections of methyl methacrylate embedded undemineralized bone show poor resolution, but prestaining with silver nitrate increases the radioopacity of the calcified tissues to soft x-rays without masking regional differences in microscopic mineralization. Identical results are achieved using aqueous (pH 5.8 and 7.5) or ammoniacal solutions (pH 7.9). Atomic absorption spectrometry detected no loss of calcium from the sections during staining. Osteoid in plastic-embedded bone is not rendered radiopaque by this technique even after prolonged staining times (5 min-2 hr).

This study tested the feasibility of using the hydrogen washout technique for measuring regional bone and bone marrow blood flow. Washout curves in cancellous and cortical bone were mono-exponential, indicating homogeneous perfusion of these tissues. Epiphyseal cancellous bone blood flow (0.129 +/- 0.015 ml/min/ml) and metaphyseal cancellous bone blood flow (0.170 +/- 0.014 ml/min/ml) were approximately twice as rapid as that of cortical bone (0.069 +/- 0.002 ml/min/ml). Washout of hydrogen from bone marrow was variable and usually formed a bi-exponential pattern, indicating non-homogeneous perfusion. Blood flow rate determined by analyzing the rapid components was 1.04 +/- 0.10 ml/min/ml, and that from the slow components was 0.27 +/- 0.02 ml/min/ml. Our blood flow rates are within the range of values reported by investigators using different methods, and the hydrogen washout technique offers specificity and ease of repetitive determinations not available with other methods.

The effects of injections of a synthetic adrenocorticotropin (ACTH 1-17, Synchrodyn) on the rate of DNA labeling in the metaphyseal bone of CD2F1 mice were tested on a chronopharmacological dosing schedule. Groups of mice that had been conditioned to a 12-hr light/12-hr dark schedule were injected at one of six different timepoints, 4 hr apart, during a single 24-hr span with either a low (0.02 I.U./kg) or a high (20 I.U./kg) dose of ACTH 1-17. Control groups received injections of a placebo at corresponding timepoints. Subgroups of mice were injected with [3H]thymidine ([3H]Tdr) to follow the changes in DNA labeling in the proximal tibial metaphysis at 15 min and 2, 4, 8, 12 and 24 hr after ACTH 1-17 or placebo treatment. All mice were injected with the isotope 30 min before killing, except for those killed 15 min after Rx administration where the isotope had been injected 14 min before killing. The data were analyzed both by analysis of variance and by the cosinor method, the latter of which tests the fit of a 24-hr cosine curve to the data. The effect of ACTH 1-17 on the target cell population was dependent not only upon the dose but upon the time of administration. Both doses exerted time-dependent action, ranging from stimulation to inhibition of DNA labeling. Inhibition was noted when the ACTH 1-17 was administered at 2 hr after the beginning of the daily dark span when nocturnal animals become active. When administered at this circadian stage, the larger dose in particular was associated with an inhibition of DNA labeling lasting for 24 hr. The inhibitory effect was much shorter when the same dose was injected 4 hr earlier. Moreover, the large ACTH 1-17 dose had a stimulatory effect lasting for 24 hr when it was administered 2 hr after the onset of the daily light span, with a much shorter stimulation following administration of the large dose at 6 hr after the beginning of the daily dark span. A circadian stage-dependent stimulation or inhibition of DNA labeling at 2 or 14 hr after light onset, respectively, was thus complemented by an initial inhibition followed by stimulation and vice versa at 10 and 18 hr after light onset respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

We have demonstrated via marrow stromal cell cultures and the osteoinductive response to demineralized bone grafts (DBM) that the cortical bone deficit in the ovariectomized (OVX) rat (6 weeks postop) is primarily due to impaired osteoprogenitor cell proliferation, and that dihydrotachysterol (DHT) treatment can be protective. In cultured marrow stromal cells from OVX rats, short-term DHT-Rx exaggerated the already subnormal pattern of marrow stromal cell proliferation. However, in DBM grafts, DHT treatment benefited the time-course of mesenchymal cell DNA synthesis as measured by tritiated thymidine incorporation and osteogenic cell maturation as measured by alkaline phosphatase concentration, and established a suggestive trend toward normalization of bone formation/mineralization (24 h 45Ca incorporation). The data from this animal model infer that DHT could moderate the bone loss normally seen in ovariectomized rats via an activation of the osteoprogenitor cell population.

Unicompartmental osteoarthritis was produced by applying varus stress to moving rabbit knee joints. Degenerative changes were confined to the medial tibial and the medial femoral articular surfaces. Within the range of varus stress used, duration appears to be more important than magnitude of varus stress in determining the severity of cartilage damage. The calcified zone remained histologically unchanged despite advanced changes in the noncalcified zone superficial to the tidemark. Intrachondral degenerative cysts were frequently found in the basilar layers of the noncalcified cartilage adjacent to the tidemark where shear stresses were likely to be highest and diffusible nutrients least available. Highly cellular cartilaginous tissue was noted in the subchondral marrow spaces in the specimens with advanced cartilage degeneration. These areas appeared to be continuous with the overlying degenerated cartilage through gaps in the calcified cartilage. Subchondral bone did not show remarkable trabecular thickening despite advanced degenerative changes in the articular cartilage.

Changes in radiostrontium clearance (SrC) and bone formation (tetracycline labeling) were observed in the femurs of skeletally mature dogs following the various operative steps involved in bone screw fixation. Drilling, but not periosteal stripping, produced a small but statistically significant increase in SrC and endosteal bone formation in the distal third of the bone. Strontium clearance values equivalent to those produced by drilling alone were recorded after screw fixation at low or high torque (5 versus 20 inch pounds), as well as by the insertion of loosely fitting stainless steel implants. Bone formation (equals the percentage tetracycline-labeled trabecular bone surfaces) was increased by 30% when SrC values exceeded 3.5 ml/100 g bone/min, and the relationship was linear when SrC values ranged between 1.0 and 7.0 ml/100 g bone/min. The changes in SrC and bone formation one-week after bone screw application are primarily those associated with a response to local trauma caused by drilling.

Based on reports of electrically induced bone formation and findings that some materials used to promote bone ingrowth are stimulatory in bead form, the osteogenic potential of beads with different surface charges was examined. In this preliminary study, three types of Sephadex beads were injected into chick femora: type I, DEAE beads, positively charged; type II, CM beads, negatively charged; type III, G-25, uncharged. Beads were injected into the femoral midshaft, and after 3 days, 4 days, and 1 week, birds were sacrificed and femora were processed for histology. Type I beads: at 3 days, were surrounded by multinucleated giant cells; by 4 days, patches of bead-associated new bone were present along with giant cells; after 1 week, occasional bead-associated multinucleated cells were seen, but now most beads were surrounded by new intramedullary bone, forming an extensive bead-bone lattice. With bead types II and III, bead-associated new bone was seen at 3 days and 4 days only when beads lodged near the endosteum or in the metaphysis. At 7 days, no bone was seen with either of these two bead types. The response to the type I beads may be likened to a remodeling phenomenon with large numbers of giant cells at 3 days, new bone and giant cells at 4 days, and evidence only of bone formation at 7 days.

The role of MRI in identifying the tissue level changes in the femoral head was investigated in five patients diagnosed as having avascular necrosis by radiology, scintigraphy, and MRI (0.35 Telsa). Radiographic scoring by the Ficat and Arlet system showed one hip with stage I, one stage II, two stage III, and one stage IV changes. The histologic features of core biopsy specimens obtained during decompression of the femoral heads were compared to the preoperative T1 and mixed T1/T2-weighted MR images. The cores varied with respect to their distance from the subchondral bone (7-23 mm) and length (19-45 mm). At the subchondral end of the core tract, low T1-weighted images corresponded to marrow fibrosis (5 cases) and in three of five cases to increased trabecular bone volume (TBV = 44-50%). Subjacent areas of diffusely decreased MR signal corresponded to marrow fibrosis and necrosis, with a relatively normal TBV (17-28%). The distal ends of the core tracts showed normal fatty marrow and a normal MR signal. The observations affirm that the MR signal intensity is largely reduced as a function of marrow degeneration and loss of fat content, but the signal is not predictive of particular histotypic morphologic patterns.

The maturation profiles of calcium, phosphorus, magnesium and hydroxyproline in the femoral trabecular and cortical bone and in the thoracic vertebrae from male rats flown on the 7-day 'Spacelab-3 Mission' were measured by density gradient analysis. In rats exposed to a spaceflight environment, profiles of the matrix and mineral moieties were shifted toward both the lower (vertebrae) and higher density fractions (femurs and vertebrae), patterns indicating a decrease in bone growth/turnover. X-Ray diffraction of vertebrae indicated that spaceflight is associated with a decrease in apatite crystal size/perfection.

The lower incisors of Male Wistar rats flown for 18.5 days on the Soviet Cosmos-1129 Biosatellite were sectioned and chemically analyzed with an electron microprobe in order to determine whether there were specific effects of spaceflight on dentin formation/mineralization. Control tissues were obtained from rats housed under identical conditions in a land-based mock-up of the Biosatellite. The profiles of calcium (Ca), phosphorus (P), and sulfur (S) concentrations in dentin were measured in continuous traverses (1.0 micron intervals) from the pulp to the dentinoenamel junction. The incisor dentin formed during spaceflight had higher than normal (at 1G) concentrations of Ca (+ 10-15%) and P (+ 20-30%), particularly in the temporally youngest tissues within 80 micron of the pulp which had been least affected by secondary mineralization. The S-concentration profiles tended to decrease with tissue age. Fourier analysis (to determine the growth rhythms) revealed abnormal distributional patterns of S in the recently formed dentin from the Flight rats. The sulfur fluctuations in Flight animals alone periodically peaked above the irregular background fluctuations. These observations indicate that spaceflight has measureable effects on dentinogenesis, and they may also bear on the problem of the regulatory role of proteoglycans in mineralization and in the maturation of mineral and matrix moieties in skeletal tissue.

To establish whether there are single or multiple pools of osteoblasts in rabbit bone, animals were injected with tetracycline on various schedules for 1-3 days. Metabolic restraints predicted that a multiple pool model would be feasible only if the percent labeled surfaces of trabecular bone (tibia) doubled when animals were injected on days 1 and 2, 1 and 3, or on days 1, 2, and 3. A single population would be indicated if the extent of labeled surfaces failed to double. Herein, 41.9 +2- 8.1% of bone surfaces labeled after a single injection, and only 60-68% of surfaces labeled after injections on the other schedules. The data inferred tht serial pulse tetracycline injections at 24h intervals caused a shift in the activities of a single population of osteoblasts and their progenitor cells.

This study reports the effects of simulation of certain aspects of hypogravity (via partial skeletal unloading) on the growth and maturation of the non-weight bearing mandibles of 41-d and 1-yr-old rats. Partial skeletal unloading was effected by elevating the hindquarters (PULEH), and this simulation was controlled with normally loaded animals fed either ad libitum or the average amount of food consumed by the the experimental group (group-mean fed). The chemical status of the mandibles after 10 d or 14 d PULEH closely resembled that of control rats. The younger PULEH rats and their group-mean fed controls demonstrated a trend toward impaired maturation of mineral and matrix moieties; yet the concentrations of calcium (Ca) and phosphorus (P) expressed as a ratio to collagen hydroxyproline content were normally distributed within a density gradient profile which separates the mineral and matrix moieties into various age-dependent fractions. These data demonstrate that 10 d or 14 d PULEH in young or old rats, respectively, is not sufficient to elicit the maturation deficit observed in the mandibles of rats flown for 18.5 d in the Soviet Biosatellite Cosmos-1129. Unless the duration of PULEH is critical, the cephalad fluid shift which is common to PULEH and spaceflight animals cannot be solely responsible for the flight-induced maturation deficit. Because the mandibles of the PULEH rats remain antigravity-postured, the results emphasize the importance of gravity unloading to the impairment of mandibular bone matrix/mineral maturation during spaceflight. Decreased gravity and, hence, gravity unloading cannot be mimicked in ground-based models of hypokinesia.

Male Wistar rats prelabeled with tetracycline to mark surfaces of bone and tooth formation-mineralization were placed into orbit for 18.5 days aboard the Soviet COSMOS-1129 Biosatellite. They were injected with tetracycline for a second and third time on the 6th and 27th days, respectively, after recovery of the Biosatellite. Spaceflight did not alter the rate of periosteal bone formation in the non-weight-bearing ribs and regions of the mandibles, which were covered by masticatory muscles. Bone formation-calcification rates were impaired at those sites in the jaw that had no contiguous muscle (molar region). The remodeling activity on the alveolar bone around the buccal roots of the molar teeth was significantly reduced but without creating a negative balance between formative and resorptive activities. Total Ca, P, and hydroxyproline concentrations in the jaws, incisors, and ribs were normal after spaceflight, but gravity density fractionation studies indicated that in the jaws alone, O-G conditions caused a delay in the maturation of bone mineral and matrix. A 29-day postflight recovery period at earth's gravity was sufficient to fully correct these anomalies. Relative to tooth formation, relatively normal circadian and infradian biorhythmic periodicities of Ca and P in dentin and enamel were maintained during spaceflight. We conclude that most of the non-weight-bearing bones of the rat skeleton are at risk to the effects of hypogravity.