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Results for “BONE REGENERATION”

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At least 919 records · Page 51Linked to original sources
PubMed1996

Calcification of cross-linked collagen-elastin membrane implants in vivo and their proposed use in bone regeneration.

Factors influencing the in vivo calcification of porcine collagen membranes containing elastic fibres were investigated by light and confocal microscopy. Two glutaraldehyde (GA) cross-linking protocols were used: a new one involving microwaving (NEWGA), and a conventional method using GA treatment at room temperature (OLDGA). We observed that the physical and chemical properties of implanted membranes will influence the acute inflammatory response, which initially checks the calcification process. The NEWGA membranes are superior in cases where rapid calcification is desired. In this context, it is proposed that NEWGA membranes may serve as a useful delivery system for bone morphogenetic protein (BMP).

Animals↗
PubMed1986

Characterization of normal and regenerating bone marrow cells with a panel of monoclonal antibodies.

To obtain baseline data for the diagnosis of residual leukaemia or lymphoma in bone marrow (BM), BM samples of 12 normal adults, 6 patients treated with chemotherapy for solid tumours and 6 patients treated with chemotherapy for leukaemia or lymphoma during remission were assessed with a panel of monoclonal antibodies by fluorescence microscopy immediately following chemotherapy. A large variability between normal individuals was found concerning the percentages of T lymphocytes and T cell subsets, B lymphocytes, HLA-DR+ and OKT10+ cells, due to variation in BM composition and, presumably, peripheral blood contamination. The regenerating BM cells also showed a large variability and, in addition, sometimes very high percentages (up to 19%) of CALLA+, c mu + s mu-, c mu + kappa lambda- and TdT+ cells were found. The interpretation of data on individual BM samples of patients assessed for leukaemia or lymphoma should therefore be related to: the amount of contaminating peripheral blood cells; the cellular composition of the BM samples as determined by May-Grünwald Giemsa staining; baseline data of age-matched normal controls and of regenerating BM of patients without haematological diseases.

Adolescent↗
PubMed2004

Molecular cloning and characterization of Mustang, a novel nuclear protein expressed during skeletal development and regeneration.

Bone regeneration occurs as a series of events that requires temporal and spatial orchestration of numerous cell types guided by the transcriptional activity of thousands of genes, as recently demonstrated by our laboratory. Using the rat femoral fracture model, bioinformatics, cloning, expression assays, fusion proteins, and transfection, we report on the identification and characterization of one such differentially expressed gene, termed Mustang (musculoskeletal temporally activated novel gene). Mustang encodes for an 82 amino acid nuclear protein with no homology to any known protein family. However, other species homologues (mouse, human, cow) were identified within EST (expressed sequence tag) databases. Nuclear localization was confirmed using a GFP-Mustang fusion protein. Using in situ hybridization, Mustang expression was localized to differentiating periosteal osteogenic cells, proliferating chondrocytes, and osteoblasts of the fracture callus. Unlike adult tissues, developing embryos abundantly express Mustang, especially in mesenchymal condensations of limbs, vertebral perichondrium, and mesenchymal cells of the intervertebral discs. Although the precise function of Mustang is unknown, its unique pattern of expression during bone development and regeneration, absence in adult tissues (except skeletal muscle and tendon), and nuclear localization suggest that Mustang is involved in the development and regeneration of the mammalian musculoskeletal system.

Amino Acid Sequence↗
PubMed1996

Guided bone regeneration in the treatment of periimplantitis.

The objective of the present experiment was to study the soft and hard tissue healing following treatment of experimentally induced periimplantitis. 5 labrador dogs about 1-year old were used. The mandibular right and left 1st molars, 4th and 3rd premolars were removed, titanium fixtures (Brånemark System) were installed, and standard abutments were connected in a 2nd stage procedure. After 3 months experimental periimplantitis was induced by the placement of cotton floss ligatures in a submarginal position. 6 weeks later the ligatures were removed. 1 month after ligature removal, an antibiotic regimen was initiated. During a 3-week period, each dog was given tablets of amoxicillin and metronidazole. In the left side of the mandible, buccal and lingual mucoperiosteal flaps were elevated and granulation tissue within the bone craters curetted. The abutments were removed. The exposed outer surfaces and the internal part of the fixtures were carefully cleaned with a detergent (delmopinol HC1). An e-PTFE membrane was placed over each fixture and adjusted to cover the bone crater. New cover screws were fitted through the membranes to the cleaned fixtures. The implants were submerged and the flaps sutured. In the right side of the mandible no local treatment was performed. The dogs were sacrificed after 4 months and biopsies prepared for histological examination. The findings indicated that treatment of a periimplantitis lesion, including comprehensive systemic antimicrobial therapy and cleaning of submerged implants resulted in (i) the elimination of the inflammatory process in the periimplant tissues and (ii) the establishment of a dense connective tissue capsule in direct contact with the previously exposed surface of the implant system. It was also observed that (iii) new bone was frequently laid down on the pristine cover screws.

Animals↗
PubMed2000

Increased distraction rates influence precursor tissue composition without affecting bone regeneration.

The effect of increased distraction rate on bony tissue differentiation was studied using a paired bilateral model of rat femur lengthening. After a 6-day latency period, one randomly selected femur for each rat was distracted at 0.5 mm/day (normal rate) for 12 days, and the contralateral femur was distracted at 1.5 mm/day (increased rate) for 4 days. Femoral lengthening for each side was 6.0 mm, leaving the increased rate leg with an extra 8 days of consolidation compared with the normal rate limb. Group I rats (n = 9) were killed at day 18 postsurgery and analyzed for cartilage tissue composition and distribution. Group II rats (n = 7) were killed on day 36 postsurgery and analyzed by three-dimensional microcomputed tomography (MCT) for changes in new bone volume. Digital color analysis of slides stained with type II collagen antibody showed increases in cartilaginous tissue formation on the increased rate side (1.51 mm2 vs. 0.83 mm2; p = 0.10). No differences in new bone volume were detected between increased rate limbs and their contralateral controls (46.13 mm3 vs. 42.69 mm3; p = 0.63). These findings suggest that intermediate distraction rates may influence precursor tissue composition without affecting the final amount of new bone formed. Because damage to the tissue was not detected at either time point, these changes in chondrogenesis may reflect sensitivity of the pluripotential gap tissue to tension accumulation during lengthening. Future work with this in vivo model is focused on improving our understanding of the mechanisms behind this strain sensitivity.

Animals↗
PubMed2000

[Effect of glass ceramics on bone regeneration in calvarial defects. Experimental study].

INTRODUCTION: The purpose of this study was to investigate the influence of different compositions of resorbable porous glass ceramics on their performance in calvarial defects. MATERIAL AND METHODS: Full-thickness defects (8.1 mm diameter) were made in the calvaria of 75 adult Sprague-Dawley rats. Pellets of porous glass ceramics were inserted press-fit into 60 defects. Four different materials were implanted into each of 15 animals: (1) glass ceramic with a high relation of calcium to phosphate containing silicate; (2) glass ceramic with a high relation of calcium to phosphate without silicate; (3) glass ceramic with a low relation of calcium to phosphate without silicate; and (4) glass ceramic with a low relation of calcium to phosphate containing silicate. Five implants of each group were evaluated by fluorescence microscopy and light microscopy after 6, 13, and 26 weeks. RESULTS: Those glass ceramics with a high relation of calcium to phosphate showed formation of new bone entering the defect from the margins as soon as 6 weeks postoperatively. After 26 weeks, the formation of new bone reached the center of the defect. In the other glass ceramics, the formation of unmineralized osteoid was visible entering the defect from the margins. No mineralization was seen 26 weeks postoperatively. There was no significant difference between glass ceramics containing silicate and those free of silicate. CONCLUSIONS: Bioresorbable glass ceramics may be of benefit in the treatment of osseous defects without functional loading.

Animals↗
PubMed2005

Pulsed electromagnetic stimulation of regenerate bone in lengthening procedures.

Distraction osteogenesis for limb lengthening represents the treatment of choice in patients with small stature or limb length discrepancies. Bone lengthening and callus formation requires a long therapy. Pulsed electromagnetic fields (PEMF) are normally used to enhance osteogenesis in patients with non-unions. In this study we investigated whether pulsed electromagnetic fields could be used effectively to encourage callus formation and maturation during limb lengthening procedures. Thirty patients underwent bilateral bone lengthening of the humerus, femur or tibia. At day 10 after surgery, PEMF stimulation was started on one side, for 8 hours/day. Stimulated distraction sites exhibited earlier callus formation and progression, and a higher callus density compared to non-stimulated sites. External fixation could be removed on average one month earlier in PEMF stimulated bones. Our results show that the use of pulsed electromagnetic fields stimulation during limb lengthening allows shortening the time of use of the external fixation.

Body Height↗
PubMed2006

Concomitant aberrant overexpression of RUNX1 and NCAM in regenerating bone marrow of myeloid leukemia of Down's syndrome.

BACKGROUND AND OBJECTIVES: Myeloid leukemia of Down's syndrome (ML-DS) has characteristic biological features (e.g. expression of the truncated GATA1s), which are different from those of non-DS childhood acute myeloid leukemias (AML). The objective of this study was to investigate factors predisposing to the development of ML-DS. DESIGN AND METHODS: We analyzed 134 bone marrow specimens from 64 children with ML-DS and non-DS AML during chemotherapy and 7 specimens from DS children with- out leukemia,who did not receive any chemotherapy,The specimens were analyzed by multiparameter flow cytometry and quantitative reverse transcriptase polymerase chain reaction for transcription factors involved in hematopoiesis. RESULTS: Samples taken from children with ML-DS in complete remission during chemotherapy aberrantly expressed CD56 (NCAM) at the surface of monocytic and granulocytic cells. Compared to non-DS AML cases,children with ML-DS had a statistically significant higher proportion of CD56+ cells in the CD33+ fraction: 71%+/-6% vs. 4%+/-1% (p<0.00001). A significant decrease of the amount of CD33+/CD56+ cells was observed during and after maintenance therapy. An increased number of CD33+/CD56+ cells was also present (>85%) in children with DS who did not receive chemotherapy, but showed a left-shift (due to infection), compared with DS children without left-shift (<10% CD33+/CD56+ cells). Within the CD33+/CD56+ fraction, RUNX1 was overexpressed more than 5-fold (p<0.02) compared to CD33+/CD56- cells, whereas there were no differences regarding GATA1, SPI1, ERG or ETS-2 levels. INTERPRETATION AND CONCLUSIONS: The combined overexpression of RUNX1 and NCAM during stress hematopoiesis in children with DS might be a key factor in the development of overt leukemia and/or in the growth advantage of the malignant GATA1s clone in ML- DS.

Adolescent↗