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At least 235 records · Page 13Linked to original sources
PubMed1992

Development of alloplastic materials for temporomandibular joint prosthesis: a historical perspective with clinical illustrations.

This paper gives the history of the development of alloplastic materials presently used in the temporomandibular joint (TMJ). It discusses the evaluation of TMJ implants, from those being used primarily for ankylosis to the more varied and sophisticated implant designs used today. There is a discussion on the treatment of osteoarthritis with implants and also a discussion on the use of TMJ implants to repair skeletal and dental malrelationships, primarily anterior open bites. Included is a presentation of the latest research by Schellhas et al., which establishes that previously undiagnosed organic disease in the joint proper is a common cause of skeletal and dental malrelationships and that TMJ disease can cause malocclusion.

Adult↗
PubMed1997

The plant defense response to cucumber mosaic virus in cowpea is elicited by the viral polymerase gene and affects virus accumulation in single cells.

Resistance to infection in cowpea by strains of cucumber mosaic virus (CMV) involves a local, hypersensitive response (HR) and a localization of infection. These responses can be separated by mutation at two sites (nucleotides 1978 and 2007, in codons 631 and 641) in the CMV 2a polymerase gene. Changes to both sites of a restricted strain allow systemic infection without an HR and increase the accumulation of both the 2a protein and viral RNA in protoplasts, while changing position 1978 alone results in a systemic infection, a systemic HR, and an increase in viral RNA accumulation in protoplasts. It is suggested that the inhibition response observed in protoplasts, where an HR does not occur, leads to localization of infection in whole plants and that different plant genes are involved in eliciting the HR and the localization response.

Amino Acid Sequence↗
PubMed2001

Role of the putative membrane-bound endo-1,4-beta-glucanase KORRIGAN in cell elongation and cellulose synthesis in Arabidopsis thaliana.

A temperature-sensitive, elongation-deficient mutant of Arabidopsis thaliana was isolated. At the non-permissive temperature of 31 degrees C, the mutation impaired tissue elongation; otherwise, tissue development was normal. Hypocotyl cells that had established cell walls at 21 degrees C under light-dark cycles ceased elongation and swelled when the mutant was shifted to 31 degrees C and darkness, indicating that the affected gene is essential for cell elongation. Analysis of the cell walls of mutant plants grown at 31 degrees C revealed that the cellulose content was reduced to 40% and the pectin content was increased to 162% of the corresponding values for the wild type grown at the same temperature. The increased amounts of pectin in the mutant were bound tightly to cellulose microfibrils. No change in the content of hemicellulose was apparent in the 31 degrees C-adapted mutant. Field emission-scanning electron microscopy suggested that the structure of cellulose bundles was affected by the mutation; X-ray diffraction, however, revealed no change in the crystallite size of cellulose microfibrils. The regeneration of cellulose microfibrils from naked mutant protoplasts was substantially delayed at 31 degrees C. The recessive mutation was mapped to chromosome V, and map-based cloning identified it as a single G-->A transition (resulting in a Gly(429)-->Arg substitution) in KORRIGAN, which encodes a putative membrane-bound endo-1,4-beta-glucanase. These results demonstrate that the product of this gene is required for cellulose synthesis.

Arabidopsis↗
PubMed1990

Healing of maxillary and mandibular bone defects using a membrane technique. An experimental study in monkeys.

Cyst-like cavities in the jaw bone often heal incompletely owing to ingrowth of connective tissue, thus preventing osteogenesis from occurring. In the present study, a new membrane technique has been utilized in an attempt to improve bone healing. By means of an inert, porous membrane, placed in close contact with the bone surface, a secluded space is created which can only be repopulated by cells from the adjacent bone. Thus, osteogenesis is able to occur without interference from other tissue types. Through-and-through bone defects were produced bilaterally (1) in edentulous areas of monkey (n = 5) mandibles, and (2) in conjunction with apicectomy of the lateral maxillary incisors, also in monkeys (n = 7). On one side, the defects were covered buccally as well as lingually/palatally with expanded PTFE membranes, whereas the defects on the other side served as controls (no membrane). In the mandible, complete bone healing was seen at all test sites after a healing period of 3 months. On the control side, 3 experimental sites showed bone discontinuity with a transosseous core of connective tissue, whereas some bone healing had occurred lingually at 2 sites, but with massive soft tissue ingrowth from the buccal side. In the maxillary periapical defects, all the membrane-covered defects had healed with bone closure after 3 months but with a minute portion of connective tissue, probably derived from the periodontal ligament, around the tooth apices. None of the control defects (no membrane) healed spontaneously, but all were filled with connective tissue to varying degrees.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Femoral endoprosthesis fixation with a soft, flexible low modulus stem coating. Four to six year clinical results.

Fifty-nine patients received 62 femoral endoprostheses exhibiting a 2 mm thick, low modulus (soft), porous stem coating in a total hip arthroplasty. Follow up ranged from 36 to 69 months (average 60 months). There were 26 male and 33 female patients whose ages ranged from 29 to 75 and 39 to 72 years, respectively (average 57 years). All patients were operated on without trochanteric osteotomy. Initial stabilization was obtained by uniform press-fit and collar/neck osteotomy contact at implantation; secondary stabilization derived from soft tissue ingrowth into the stem coating. Four implants in four patients were deleted from the scored population because of unrelated deaths or loss to follow up. By the Harris scoring system, 48 of the 58 implants (82.7%) were rated excellent or good, 58.6% and 24.1% respectively. Seven were rated poor (12.1%), of which six (10.3%) have been revised. Other revisions included one hip for secondary sepsis (1.7%), one post-traumatic fracture (1.7%), and one intraoperative technical error (1.7%).

Adult↗
PubMed1992

[Experimental study using porous, vascularizable polytetrafluoroethylene in preformed free flaps].

Following radical tumor resections or severe trauma, particularly in the head and neck region, cartilage or bone grafts serve as frame work in defect reconstruction. As an alternative, porous plastic material was used for preformed free flaps in an experimental study with 28 New Zealand rabbits. Due to ingrowth of fibrous tissue and capillaries, it was possible to obtain prefabricated flaps consisting of vascularized porous plastic, a thin layer of fatty gliding tissue and full thickness skin graft. The blood supply of all three layers of the transplant was confirmed by microangiography, Tc 99 m labeled red blood cells and histological examination.

Aluminum Oxide↗
PubMed1989

Biocompatible implants in tympanoplasty.

The history of implants in otology is reviewed. Currently available biocompatible ossicular implants are described, and a survey of their use by members of the American Otological Society and the American Neurotology Society is reported.

Biocompatible Materials↗
PubMed1988

Porous polymers for biological fixation.

Porous polymers are recommended as coatings for femoral stems on the basis of their low modulus, which allows uniform distribution of stress to surrounding bone and the fabrication of more flexible stems by reducing the metallic cross section. Application of the porous polymer coating to the metallic substrate reduces metal ion release; the polymer coating does not affect the mechanical properties of the device. Porous polytetrafluoroethylene-carbon fiber composite, (PCFC), porous polyethylene, and porous polysulfone are undergoing investigation for this application. However, the low strength of the PCFC makes its use for this application questionable. Recently reported unfavorable clinical results (i.e., a high incidence of pain) have led to the discontinuation of one trial of porous polyethylene. Clinical investigation of porous polysulfone-coated titanium alloy devices are in progress. Animal studies have shown bone ingrowth into porous polyethylene and porous polysulfone implants in cortical and cancellous bone and in canine femoral stems coated with these materials. Pull-out testing of porous polysulfone implants revealed that the strength of the porous material was higher than the strength of surrounding bone. Less cortical bone loss was found around porous polysulfone-coated canine stems than was reported for fully coated porous metallic prostheses, presumably because of the lower stiffness.

Animals↗
PubMed1987

Synthetic ligaments. Current status.

Many techniques for ligamentous reconstruction have been developed in recent years. In the United States, injuries of the knee have been increasingly treated with innovative methods of surgical reconstruction, most of which have used normal structures. There are obvious theoretic advantages in using synthetic materials that might simplify surgery, spare normal tissues, and possibly facilitate stronger repairs. To these ends, several synthetic substances have been used experimentally and clinically. This is a brief summary of eight of the materials that have been or are being investigated in the United States. Some are no longer in use, others are currently being used in clinical trials. As of this writing, only the Gortex ligament has received a general device release from the Food and Drug Administration (FDA).

Aluminum Oxide↗