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At least 703 records · Page 39Linked to original sources
PubMed2003

ECM-induced gap junctional communication enhances mammary epithelial cell differentiation.

The relationship between gap junctional intercellular communication (GJIC) and mammary cell (CID-9) differentiation in vitro was explored. CID-9 cells differentiate and express beta-casein in an extracellular matrix (ECM)- and hormone-dependent manner. In response to interaction with the ECM, cells in culture modulated the expression of their gap junction proteins at the transcriptional and post-translational levels. In the presence of EHS-matrix, connexins (Cx)26, 32 and 43 localized predominantly to the plasma membrane, and enhanced GJIC [as measured by Lucifer Yellow (LY) dye transfer assays] was noted. Inhibition of GJIC of cells on EHS-matrix with 18 alpha glycyrrhetinic acid (GA) resulted in reversible downregulation of beta-casein expression. In the presence of cAMP, cells cultured on plastic expressed beta-casein, upregulated Cx43 and Cx26 protein levels and enhanced GJIC. This was reversed in the presence of 18 alpha GA. cAMP-treated cells plated either on a non-adhesive PolyHEMA substratum or on plastic supplemented with function-blocking anti-beta 1 integrin antibodies, maintained beta-casein expression. These studies suggest that cell-ECM interaction alone may induce differentiation through changes in cAMP levels and formation of functional gap junctions. That these events are downstream of ECM signalling was underscored by the fact that enhanced GJIC induced partial differentiation in mammary epithelial cells in the absence of an exogenously provided basement membrane and in a beta 1-integrin- and adhesion-independent manner.

Animals↗
PubMed1987

Effect of cell shape on proteinase secretion by epithelial cells.

Cell proliferation has been found to correlate with increased secretion of proteinases, such as plasminogen activator, in several different cell populations. In addition, the shape of the cell may also play a role in regulating proteinase secretion. However, the relationship between cell proliferation, cell shape and proteinase secretion has not been studied in diploid epithelial (E) cells cultured from porcine periodontal ligament (PL). We have modified PLE cell shape by physical means, such as growth on less-adhesive substrata and mechanical stretching, and by exposure to cholera toxin and 12-O-tetradecanoylphorbol-13-acetate (TPA). Neutral proteinase and plasminogen activator secretion were found to correlate with cell shape, the more round the cells, the greater the amount of proteinase secreted. PLE cells, stimulated to proliferate by cholera toxin or dibutyryl cyclic AMP, were more spread than control cells, but secreted less neutral proteinase and plasminogen activator. TPA stimulated cell proliferation slightly but, in contrast to cholera toxin, increased cell rounding and the secretion of neutral proteinase and plasminogen activator. Thus proteinase secretion was related more to cell shape than to cell proliferation.

Animals↗
PubMed1998

Composite hydrogels for implants.

Hydrophilic composite structures are designed to mimic the transport and mechanical properties of natural soft tissue such as tendons, ligaments and intervertebral discs. Mechanical and viscoelastic behaviour of a soft composite material based on a hydrogel matrix reinforced with bundles of polyethylene therephthalate (PET) fibres is analysed. The typical J-shaped stress-strain behaviour, displayed by natural tendons and ligaments, is reproduced. The mechanical characteristics, such as the extent of the 'toe-in region' and the elastic modulus in the linear region, can be controlled by varying the winding angle of the fibres and the matrix composition. Dynamic mechanical analysis showed the dual behaviour of the composite systems due to the progressive contribution of the PET fibres. Different poly(2-hydroxyethylmethacrylate)/polycaprolactone (PHEMA/PCL) semi-interpenetrating polymer networks (IPNs) hydrogel composite systems reinforced with PET fibres have been investigated for potential use as intervertebral disc prostheses. Compression properties have been evaluated by static and dynamic tests. Uniaxial compression tests on the swollen samples showed an increase of the modulus and maximum stress with increasing content of PCL and PET fibres. Creep behaviour is also dependent on the hydrogel composition. The composite PHEMA/PCL hydrogels showed compression properties similar to those expressed by canine intervertebral discs in different spinal locations.

Animals↗
PubMed2000

Effect of polymer excipients on the enzyme activity of lyophilized bilirubin oxidase and beta-galactosidase formulations.

The effects of excipients on the protein stability during lyophilization as well as the storage stability of lyophilized bilirubin oxidase (BO) and beta-galactosidase (GA) formulations were studied using four polymer excipients: dextran, polyvinylalcohol (PVA), poly(acrylic acid) (PAA), and alpha, beta-poly(N-hydroxyethyl)-L-aspartamide (PHEA). Denaturation of BO and GA during lyophilization largely depended on the excipient used. Dextran appeared to cause severe damage to proteins, whereas PHEA protected proteins effectively from denaturation. Storage stability of BO and GA formulations also depended on the excipients, such that the formulations containing dextran and PAA were relatively unstable. Storage stability was improved by absorption of a small amount of water for all the formulations studied. Absorption of a larger amount of water, however, decreased the storage stability of the formulations containing PVA, PAA or PHEA. In contrast, the storage stability of formulations containing dextran did not decrease noticeably with increasing water. This may be because formulations containing dextran have a higher glass transition temperature than formulations containing PVA, PAA or PHEA when a large amount of water is absorbed.

Acrylic Resins↗
PubMed1990

Regenerating bone in clinical periodontics.

Bone autografts and allografts, various alloplastic materials, and guided tissue regeneration are used to reconstruct lost periodontal tissues. This paper focuses on controversies related to these therapeutic modalities as well as their role in periodontal regeneration.

Alveolar Bone Loss↗
PubMed1996

Ridge preservation: why not?

Ridge preservation should be a commonly used dental procedure. However, it is not. Simple ridge preservation techniques, using materials such as HTR, provide undeniable esthetic and functional benefits to patients and dentists.

Alveolar Bone Loss↗
PubMed2003

Use of HTR synthetic bone as an augmentation material in conjunction with immediate implant placement: a case report.

Immediate placement of dental implants (DI) in fresh extraction sockets is associated with remaining voids around the DI and often a partial dehiscence or thin facial alveolar plate. Bioplant HTR synthetic bone (HTR) was used as a ridge preservation/augmentation material in conjunction with this method of DI placement. A 61-year-old white woman requiring extraction of tooth 12 opted for immediate DI placement. HTR was used to fill the remaining socket void and enhance the facial ridge width, and primary closure was attempted with sutures. DI uncovering was performed at about 6 months. Measurements were taken to the nearest 0.5 mm of the internal socket width and total site width at DI placement and uncovering. The internal socket width was essentially maintained (6.8 vs 6.6 mm), and the total ridge width showed a change from 8.7 to 9.1 mm. The results of this case suggest that HTR is a useful adjunct in the placement of immediate DIs for the preservation of ridge width.

Alveolar Ridge Augmentation↗
PubMed2005

A model system to assess key vascular responses to biomaterials.

PURPOSE: To establish a reproducible laboratory test to evaluate prospective vascular biomaterials with respect to their thromboinflammatory properties by examining fibrinogen, platelet, and monocyte binding. Endothelial migration onto these surfaces was used as an index of vascular healing. METHODS: To evaluate biomaterials for potential thrombogenicity and inflammation, binding assays of radiolabeled human fibrinogen, platelets, and monocytes were performed on standard pieces of vascular biomaterials, including metals and polymeric and ceramic-coated materials. Using an established in vitro endothelial cell migration model, the relative migration rate of cultured human aortic endothelial cells onto these vascular biomaterials was measured and compared. The fibrinogen, platelet, and monocyte binding results were combined along with the migration results to create an overall score of biocompatibility. RESULTS: A significant direct relation of platelet and monocyte binding to the amount of adsorbed fibrinogen was observed. In contrast, migration rates of cultured human aortic endothelial cells onto the same biomaterial surfaces were found to be inversely related the amount of bound fibrinogen. Among the materials tested, stainless steel received the highest score of biocompatibility, while turbostratic carbon scored the lowest. CONCLUSIONS: Fibrinogen, platelet, and monocyte binding levels, as well as endothelial migration rates onto vascular material surfaces, provide a basis for evaluating thrombogenicity, inflammatory potential, and endothelialization in the laboratory prior to in vivo testing.

Alloys↗
PubMed2001

Extracellular matrix regulates ovine granulosa cell survival, proliferation and steroidogenesis: relationships between cell shape and function.

The extracellular matrix (ECM), constituting the follicular basal lamina and present also between follicular cells and in the follicular fluid, is believed to regulate granulosa cell (GC) function during follicular development. Ovine GCs isolated from small (1-3 mm in diameter) or large (4-7 mm in diameter) antral follicles were cultured on various pure ECM components (type I collagen, fibronectin, laminin), synthetic substrata enhancing (RGD peptides) or impairing (poly 2-hydroxyethylmethacrylate (poly-hema)) cell adhesion, or in the presence of heparin. The effects of these factors, used alone or in combination with IGF-I and/or FSH, were evaluated in terms of GC spread, survival, proliferation and steroidogenesis. When grown on type I collagen (CI) gel, poly-hema or heparin, GCs from both large and small follicles exhibited a round shape and a low proliferation rate. Compared with non-coated plastic substratum as a control, these ECM or synthetic compounds enhanced estradiol secretion and reduced progesterone secretion by large-follicle GCs. In contrast, GCs from both large and small follicles spread extensively on CI coating, fibronectin, laminin and RGD peptides. Fibronectin and laminin dramatically increased the proliferation rate and enhanced survival of GCs from both origins. Moreover, fibronectin, laminin and RGD peptides reduced estradiol secretion by large-follicle GCs. Unexpectedly, CI coating increased estradiol secretion and reduced progesterone secretion by large-follicle GCs, suggesting that type I collagen was able to maintain estradiol secretion independently of GC shape. Finally, GC responsiveness to IGF-I and FSH, in terms of proliferation and steroidogenesis, was generally maintained when cells were grown on ECM components, RGD peptides and in the presence of heparin. However, when large-follicle GCs were grown as non-adherent clusters (as observed on poly-hema) basal and IGF-I- and/or FSH-stimulated progesterone secretions were totally abolished. Overall, this study shows that GC shape, survival, proliferation and steroidogenesis can be modulated in vitro by pure ECM components in a specific and coordinated manner. It is suggested that, in vivo, fibronectin and laminin would sustain follicular development by enhancing the survival and proliferation of GCs, whereas type I collagen might participate in the maintenance of estradiol secretion in large antral follicles.

Analysis of Variance↗
PubMed1990

HTR polymer grafts in human periodontal osseous defects. I. 6-month clinical results.

HTR polymer was evaluated as a grafting material in periodontal osseous defects in 21 adult patients. Following initial preparation and pre-surgical documentation with standardized measurements, radiographs, and photographs, vertical osseous defects were treated with surgical open flap debridement alone (DEBR) or with DEBR plus placement of HTR polymer graft material. Patients were followed with frequent recalls until surgical re-entry at about 6 months for documentation and any needed remedial therapy. Re-entry data show that use of HTR polymer grafts resulted in significantly better mean defect fill of 2.2 mm (60.8%) compared to 1.0 mm (32.2%) with DEBR alone (P less than .001). Other hard tissue findings such as residual defect depth, crestal resorption, and percent defect resolution showed similar clinically superior results with the use of HTR polymer. Soft tissue findings showed significant differences in favor of HTR for decrease in probing depth and gain in clinical attachment. These results are similar to those reported with other graft materials. Over a 6-month period, HTR polymer was found to show promise for the repair of periodontal osseous defects.

Adult↗
PubMed1990

Human clinical and histologic responses to the placement of HTR polymer particles in 11 intrabony lesions.

Eleven intrabony periodontal lesions in five volunteer patients received surgical debridement followed by site implantation of a porous particulate polymeric composite (HTR polymer). These patients were observed over time periods varying from 4 weeks to 26 weeks. At the end of the individual observation periods, treated sites were surgically removed in block for histologic analysis. Clinical observations indicated a reduction in pocket depth following treatment which consisted of both gingival recession and gain in clinical closure. No untoward effects were observed clinically in any treated patient during the observation periods. Histologic responses varied from gain in closure by epithelial adhesion to new attachment of varying magnitude. Such varied responses were seen within the same patient and between patients. Graft particles were present at sites from 4 weeks to 26 weeks after implantation and were surrounded by connective tissue capsules. At the periphery of some particles, limited bone formation was present. The alveolar bed was remodeling, at times surrounding specific particles. In our sample, HTR polymer, therefore, appeared to be a well tolerated synthetic graft material when implanted in human intrabony lesions.

Adult↗
PubMed2000

Foreign body granuloma following placement of hard tissue replacement material: a case report.

The placement of grafting material in extraction sites for ridge preservation is an increasingly common practice among clinicians. This is a case report of a patient presenting with a symptomatic, foreign body granuloma following the placement of hard tissue replacement (HTR) in extraction sockets. The surgical specimen revealed numerous histiocytes and foreign body type giant cells. The grafting material was surgically removed and the patient's symptoms were alleviated. Although biocompatibility of HTR has previously been shown, specific applications may be contraindicated or some patients may exhibit sensitivity to this material.

Alveolar Ridge Augmentation↗
PubMed1998

Application of biomedical engineering to neurosurgery.

Biomedical engineering is increasingly becoming very important also in neurosurgery. This article describes some examples of neurosurgical applications of biomaterials which play a central role in biomedical engineering. Since a large number of biomaterials are currently used in neurosurgery, only the biomaterials that have been developed in our laboratories in collaboration with neurosurgeons are briefly presented here. The biomaterials developed include devices used for interventional neurosurgery and bioabsorbable scaffolds for regeneration of dura mater and skull bone. We developed an immediately electrically detachable coil using a poly(vinyl alcohol) junction between the coil and the delivery wire. This is the first detachable coil developed in Japan and is currently under clinical trial. In addition to the coil used for interventional neurosurgery, the development of an embolic liquid is presented. As an alternative to allografts such as Lyodura, we developed a dural substitute from synthetic bioabsorbable polymers which are completely free from potential risk of latent virus infection. Finally, our experience in tissue engineering for skull bone regeneration using growth factors coupled with polymeric carriers is presented to demonstrate the promise of tissue engineering in the future.

Aneurysm↗
PubMed1993

The use of preformed HTR polymer implants for chin augmentation. A preliminary report.

Ten patients with microgenia had their chins augmented with HTR polymer implants. The implants were inserted intraorally and fixed rigidly with a titanium screw. The postoperative course was uneventful except in one patient who had wound dehiscence and was resutured. This patient and all the others were clinically and radiographically stable at one year follow up.

Adult↗