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PubMed1992

Inhibition by methylprednisolone acetate suggests an indirect mechanism for TGF-B induced angiogenesis.

Angiogenesis induced by transforming growth factor beta (TGFB) implanted in the rabbit cornea is accompanied by an influx of inflammatory cells. To determine if the inflammatory cells are the mediators of the neovascularization, they were depleted by local administration of methylprednisolone acetate (MPA). Subconjunctival injections of 16 mg of MPA immediately following implantation of 50 ng of TGFB in the cornea prevented the inflammation and subsequent formation of capillaries. If the injections of MPA were delayed by 48 hr and the inflammatory cells were allowed to enter the cornea, angiogenesis occurred, demonstrating that MPA had no adverse effects on the ability of endothelial cells to form capillaries. These results confirm the hypothesis that TGFB induces angiogenesis indirectly by recruiting inflammatory cells capable of stimulating direct angiogenesis.

Animals↗
PubMed1990

Cell adhesion to the surfaces of polymeric beads.

The main goal of this study is to determine the relationship between the surface properties of polymeric materials and fibroblastic cell adhesion. Therefore, two series of polymeric beads, PHEMA and PS, were tested in microcarrier-facilitated cell culture systems. The crosslinked PHEMA beads were prepared by suspension polymerization of HEMA monomer in the presence of various acrylic monomers (i.e. MMA, EGDMA, DMAEMA). The hydrophobic PS beads were used after coated with different alkylamine monomers (i.e. EDA, ALAM, TEA) by plasma polymerization process. The cell culturing studies were performed with BHK cells in stationary culture conditions and the cell adhesion characteristics were determined by the common methods. Attachment of the BHK cells on these microcarriers were satisfactorily modeled by surface saturation type of mathematical expression. The results demonstrated that, there were finite number of sites on the microcarrier surfaces available for adhesion. Number of these sites depends on the surface charge density which was supplied by amine groups and surface wettability. It is possible to achieve desired cell adhesion and also growth, by changing the chemical structure of beads with suitable modification methods.

Allylamine↗
PubMed1991

Enlargement of basilar artery aneurysms following balloon occlusion--"water-hammer effect". Report of two cases.

Two patients with distal basilar aneurysms were treated with intra-aneurysmal balloon occlusion. After apparently successful therapy, follow-up angiograms demonstrated aneurysm enlargement with balloon migration distally in the sac. Geometric mismatch between the base of the balloons and the aneurysm neck together with transmitted pulsation through the 2-hydroxyl-ethylmethacrylate (HEMA)-filled balloon directly contributed to aneurysm enlargement. In this report, the authors discuss the problems of progressive aneurysm enlargement due to a "water-hammer effect" and the possibility of hemorrhage following subtotal occlusion.

Adult↗
PubMed1995

A synthetic dural prosthesis constructed from hydroxyethylmethacrylate hydrogels.

Hydroxyethylmethacrylate (HEMA) hydrogels were investigated for their suitability as a dural prosthesis. Poly-HEMA has many characteristics required for an artificial dural substitute: it is durable, flexible, easily prepared, inexpensive, easily sterilized and handled, easily shaped, and known to be chemically inert and nontoxic. Sheets made of plain HEMA were evaluated as dural substitutes in rats and rabbits after either craniotomy or laminectomy with durectomy. Histological evaluations of the prostheses and the underlying tissues were undertaken at various time points from 2 to 9 weeks postoperatively. There was minimal tissue response to the implanted HEMA gel in contrast to marked thickening of the overlying leptomeninges and cortical herniation in the control animals. It is concluded that HEMA gels fulfill the essential criteria for an effective dural substitute.

Animals↗
PubMed2004

Mechanically engineered hydrogel scaffolds for axonal growth and angiogenesis after transplantation in spinal cord injury.

OBJECT: Spinal cord injury (SCI) is a complex pathological entity, the treatment of which requires a multipronged approach. One way to integrate different therapeutic strategies for SCI is to develop implantable scaffolds that can deliver therapies in a synergistic manner. Many investigators have developed implantable "bridges," but an important property of such scaffolds--that is, mechanical compatibility with host tissues--has been neglected. In this study, the authors evaluated the results of implanting a mechanically matched hydrogel-based scaffold to treat SCI. METHODS: A nonbiodegradable hydrogel, poly(2-hydroxyethylmethacrylate) (PHEMA), was engineered using thermally initiated free radical solution polymerization. Two groups of 12 adult Sprague-Dawley rats underwent partial cervical hemisection injury followed by implantation of either PHEMA or PHEMA soaked in 1 microg of brain-derived neurotrophic factor (BDNF). Four rats from each group were killed 1, 2, or 4 weeks after induction of the injury. Immunofluorescence staining was performed to determine the presence of scarring, cellular inflammatory responses, gliosis, angiogenesis, and axonal growth in and around the implanted scaffolds. CONCLUSIONS: The implanted PHEMA with 85% water content had a compressive modulus of 3 to 4 kPa, which matched the spinal cord. Implanted PHEMA elicited modest cellular inflammatory responses that disappeared by 4 weeks and minimal scarring was noted around the matrix. Considerable angiogenesis was observed in PHEMA, and PHEMA soaked in BDNF promoted axonal penetration into the gel. The authors conclude that mechanically engineered PHEMA is well accepted by host tissues and might be used as a platform for sustained drug delivery to promote axonal growth and functional recovery after SCI.

Animals↗
PubMed1990

Angiogenic activity in damaged skeletal muscle.

After a muscle is damaged, blood vessels spontaneously grow into the injured region as the muscle fibers regenerate. The stimulus for this vascular ingrowth is currently unknown. We hypothesized that the damaged muscle releases a factor(s) capable of stimulating this revascularization. To test this theory, extracts were prepared from rabbit hind limb muscles and incorporated into Hydron, a slow-release polymer. Pellets of the extract containing Hydron were implanted between the layers of the rabbit corneal stroma as an assay for angiogenic activity. The normally avascular corneas were examined 7 days after surgery for the presence of new blood vessels. Skeletal muscle-derived extract from rabbits elicited positive angiogenic responses in a dose-dependent manner. Four hundred to 500 micrograms of the skeletal muscle-derived extract were required to produce maximum vessel ingrowth. The control, Dulbecco's phosphate-buffered saline in Hydron, failed to stimulate neovascularization.

Angiogenesis Inducing Agents↗
PubMed1991

An angiogenic extract from skeletal muscle stimulates monocyte and endothelial cell chemotaxis in vitro.

The purpose of this study was to determine whether the extraction of skeletal muscle with a combination of ethanol and hydrochloric acid yields a product capable of stimulating angiogenesis. The resulting extract stimulated inflammation in the rabbit corneal assay, which was followed by capillary formation. In order to determine whether the observed angiogenesis was stimulated by a factor(s) acting directly on the endothelial cells versus a factor(s) recruiting macrophages that in turn release factors acting on endothelial cells, the muscle extract was tested for endothelial cell and monocyte chemotaxis activity in vitro. The muscle extract stimulated significant endothelial cell chemotaxis at concentrations between 94 and 750 micrograms of protein/ml and significant monocyte chemotaxis at concentrations between 8 and 75 micrograms of protein/ml. Polyacrylamide gel electrophoresis suggests that basic fibroblast growth factor and transforming growth factor-beta may be present in this acid/ethanol extract of skeletal muscle.

Animals↗
PubMed2004

Diplopia and periorbital mass associated with Miragel buckling explant.

A 28-year-old female presented with a palpable mass lesion on the superonasal aspect of her right globe and she had a progressive diplopia. She had a scleral encircling surgery with a Miragel explant (MIRA, Waltham, Mass, USA) for the tractional retinal detachment associated with pars planitis 9 years previously. On examination, she revealed restricted eye movements of her right eye. The magnetic resonance imaging documented a swelling of the Miragel explant that mimicked a periorbital mass lesion. The Miragel explant was removed and fragmentation of the explant was found intraoperatively. The removed Miragel explant was examined by a scanning electron microscopy, and this demonstrated a disintergrated and swollen structural composition of the Miragel explant. Postoperatively, her extraocular movement was almost restored and the retina remained well attached. Alterations in the structural composition of the Miragel explant results in an excessive swelling that causes a restriction of the extraocular movement, and this can mimick a periorbital mass lesion.

Adult↗
PubMed1991

Long-term compatibility of intraocular lens implant materials.

This paper provides a general review of the long-term compatibility of intraocular lenses (IOLs), with specific reference to the compatibility of synthetic polymers used to fabricate IOLs. The first IOL was implanted in 1949. It was composed of polymethylmethacrylate (PMMA) and placed in the posterior chamber of the eye. In 1990, approximately 1.4 million IOLs were implanted in the U.S., nearly all composed of PMMA and nearly all implanted in the posterior chamber of the eye. However, many changes have taken place in the past 40 years to improve the compatibility of IOLs and to make cataract surgery and IOL implantation among the safest and most effective major surgical procedures.

Biocompatible Materials↗
PubMed1992

HTR polymer and sinus elevation: a human histologic evaluation.

HTR (hard tissue replacement) polymer was used in a second session to perform 26 sinus floor elevations in 16 patients with dental implantation (Flexiroot, U.S.A.). A period of 6, 8, 10, or 12 months elapsed between the two operations, making it impossible to examine the tissular integration of HTR from both clinical and human histologic aspects. Following the sinus elevation, neither prolonged wound healing nor a rejection reaction was observed in any of the cases. During an 8 to 10 month period, sufficient new bone and fibrous connective tissue had grown between the HTR granules to ensure appropriate supporting tissue for the implantation. Subsequently (12 months), the HTR and the new bone became clinically increasingly harder, forming a union that was difficult to shape. HTR may be stated to be a material suitable for purposes of sinus elevation. In three cases in which the alveolar bone was originally very thin (2 to 3 mm), the resorption of this bone was observed, as a consequence of this the implantation was not performed. The resorption is explained by the inadequate blood supply that developed for surgical-technical reasons, and is not connected with the nature of the material used for the sinus elevation.

Alveolar Bone Loss↗
PubMed1999

[Progressive deterioration of episcleral Miragel explants].

Miragel (TM) episcleral explants undergo deterioration with the passing years, so that their ablation becomes necessary in a growing number of cases because of progressive discomfort and/or diplopia. The present study deals with 13 eyes undergoing the removal of an episcleral Miragel explant between 10/1/96 and 10/15/98. The Miragel explant ablation, which is tedious because of the material alterations, gives excellent functional and cosmetic results. The risk of retinal detachment recurrence seems low.

Biocompatible Materials↗
PubMed1999

[Dural arteriovenous fistula of the transverse sigmoid sinus after transvenous embolization of the carotid cavernous fistula].

We report a case of dural arteriovenous fistula of the transverse-sigmoid sinus after transvenous embolization of the carotid cavernous fistula. A 72-year-old woman presented with left exophthalmos, chemosis, bruit and left abducens nerve palsy in June 1996. Bilateral external and internal carotid angiograms revealed the dural arteriovenous fistula of the cavernous sinus. We embolized the dural arteriovenous fistula using a transvenous approach via the left inferior petrosal sinus. Angiograms demonstrated the complete disappearance of the dural arteriovenous fistula. Two years and six months later, she complained of tinnitus at the retroauricular region. Left external carotid angiograms showed a dural arteriovenous fistula of the transverse-sigmoid sinus fed by occipital, posterior auricular, middle meningeal and superficial temporal arteries. We embolized the dural arteriovenous fistula using a transarterial approach. Her symptoms disappeared but the dural arteriovenous fistula did not disappear completely. We discussed the clinical features and etiology of this case.

Aged↗
PubMedDate not supplied

Synthetic bone grafts in peri-implant bone dehiscences: histological results in humans.

This study describes the histological results found in three patients treated with osseointegrated implants and Bioplant HTR (Hard Tissue Replacement) synthetic bone graft in peri-implant dehiscences adjacent to implants. This therapy was carried out without the use of barrier membranes. Bioplant HTR is reported to act as its own barrier and prevent gingival soft tissue migration ingrowth. The histologic picture demonstrated that Bioplant HTR is osteoconductive and biocompatible, and can be used both as bone substitute and as a barrier for guided bone regeneration in implant therapy.

Adult↗
PubMed2000

Stabilization of the Ras oncoprotein by the insulin-like growth factor 1 receptor during anchorage-independent growth.

R- cells are 3T3 cells derived from mouse embryos with a targeted disruption of the type 1 insulin-like growth factor receptor (IGF-IR) genes. R- cells are refractory to transformation by a variety of viral and cellular oncogenes, including an activated Ras. R- cells stably transfected with an activated Ha-Ras (R-Ras cells) fail to form colonies in soft agar. An IGF-IR truncated at residue 1245 cannot transform R- cells, even when strongly overexpressed. However, the combination of the truncated IGF-IR and an activated Ras induces transformation of R- cells. We show here that the Ras oncoprotein is rapidly degraded when R-Ras cells are grown under anchorage-independent conditions and that signaling from the truncated IGF-IR stabilizes Ras. In monolayer cultures, Ras levels remain constant regardless of the presence or absence of IGF-IR signaling. These results directly explain why Ras cannot transform mouse embryo fibroblasts devoid of IGF-IR. They also suggest a more generalized, alternative mechanism for transformation by Ras and, implicitly, another possible way for targeting Ras in tumor cells.

3T3 Cells↗
PubMed2000

Comparative study of the hydration of hydrophilic contact lenses by refractive index and gravimetry.

PURPOSE: To compare the percent hydration by wet weight of hydrogel contact lenses given by the manufacturers with the values obtained using the refractive index and the gravimetry methods. METHODS: We used a Valentine refractometer to determine the refractive index of new hydrogel contact lenses at equilibrium swelling in the original solution and container. From the refractive indexes we then obtained the percent hydration of the lenses using a previously prepared graph of refractive index vs percent hydration of saccharose in a phosphate buffer solution (pH 7.0). We used an electronic analytical balance of 0.01 mg resolution to obtain the weights of new lenses when dry and at equilibrium swelling dry, and calculated the percent hydration of the lenses from the difference of the wet and dry weights. RESULTS: The hydration values of the contact lenses obtained from the index of refraction differed more than those obtained by gravimetry from the values given by the manufacturers. Acuvue lenses were an exception-the difference for them was negligible. CONCLUSION: Gravimetry is more accurate, but more cumbersome and time-consuming than the index of refraction for the determination of the hydration of the hydrogel contact lenses. However, when a fast and easy method is required to obtain the approximate hydration of hydrogel contact lenses, the use of the refractive index method can give acceptable results for most applications.

Contact Lenses, Hydrophilic↗