Biomedical subjects

M Olmstead

Publications and source records attributed to M Olmstead.

6 recordsLinked to original sources

PubMed2003

Osteochondral repair of primate knee femoral and patellar articular surfaces: implications for preventing post-traumatic osteoarthritis.

The risk of post-traumatic osteoarthritis following an intra-articular fracture is determined to large extent by the success or failure of osteochondral repair. To measure the efficacy of osteochondral repair in a primate and determine if osteochondral repair differs in the patella (PA) and the medial femoral condyle (FC) and if passive motion treatment affects osteochondral repair, we created 3.2 mm diameter 4.0 mm deep osteochondral defects of the articular surfaces of the PA and FC in both knees of twelve skeletally mature cynomolgus monkeys. Defects were treated with intermittent passive motion (IPM) or cast-immobilization (CI) for two weeks, followed by six weeks of ad libitum cage activity. We measured restoration of the articular surface, and the volume, composition, type II collagen concentration and in situ material properties of the repair tissue. The osteochondral repair response restored a mean of 56% of the FC and 34% of the PA articular surfaces and filled a mean of 68% of the chondral and 92% of the osseous defect volumes respectively. FC defect repair produced higher concentrations of hyaline cartilage (FC 83% vs. PA 52% in chondral defects and FC 26% vs. PA 14% in osseous defects) and type II collagen (FC 84% vs. PA 71% in chondral defects and FC 37% vs. PA 9% in osseous defects) than PA repair. IPM did not increase the volume of chondral or osseous repair tissue in PA or FC defects. In both PA and FC defects, IPM stimulated slightly greater expression of type II collagen in chondral repair tissue (IPM 81% vs. CI 74%); and, produced a higher concentration of hyaline repair tissue (IPM 62% vs. CI 42%), but IPM produced poorer restoration of PA articular surfaces (IPM 23% vs. CI 45%). Normal articular cartilage was stiffer, and had a larger Poisson's ratio and less permeability than repair cartilage. Overall Cl treated repair tissue was stiffer and less permeable than IPM treated repair tissue. The stiffness, Poisson's ratio and permeability of femoral condyle cast immobilized (FC CI) treated repair tissue most closely approached the normal values. The differences in osteochondral repair between FC and PA articular surfaces suggest that the mechanical environment strongly influences the quality of articular surface repair. Decreasing the risk of post-traumatic osteoarthritis following intra-articular fractures will depend on finding methods of promoting the osteochondral repair response including modifying the intra-articular biological and mechanical environments.

Animals↗

PubMed2001

Syntheses, structures, and reactivity of low spin iron(III) complexes containing a single carboxamido nitrogen in a [FeN5L] chromophore.

A new pentacoordinate ligand based on TPA (tris-(2-pyridylmethyl)amine), namely, N,N-bis(2-pyridylmethyl)amine-N-ethyl-2-pyridine-2-carboxamide (PaPy(3)H), has been synthesized. The iron(III) complexes of this ligand, namely, [Fe(PaPy(3))(CH(3)CN)](ClO(4))(2) (1), [Fe(PaPy(3))(Cl)]ClO(4) (2), [Fe(PaPy(3))(CN)]ClO(4) (3), and [Fe(PaPy(3))(N(3))]ClO(4) (4), have been isolated and complexes 1-3 have been structurally characterized. These complexes are the first examples of monomeric iron(III) complexes with one carboxamido nitrogen in the first coordination sphere. All four complexes are low spin and exhibit rhombic EPR signals around g = 2. The solvent bound species [Fe(PaPy(3))(CH(3)CN)](ClO(4))(2) reacts with H(2)O(2) in acetonitrile at low temperature to afford [Fe(PaPy(3))(OOH)](+) (g = 2.24, 2.14, 1.96). When cyclohexene is allowed to react with 1/H(2)O(2) at room temperature, a significant amount of cyclohexene oxide is produced along with the allylic oxidation products. Analysis of the oxidation products indicates that the allylic oxidation products arise from a radical-driven autoxidation process while the epoxidation is carried out by a distinctly different oxidant. No epoxidation of cyclohexene is observed with 1/TBHP.

Amides↗

PubMed2000

Diffusion of Ge below the Si(100) surface: theory and experiment

We have studied diffusion of Ge into subsurface layers of Si(100). Auger electron diffraction measurements show Ge in the fourth layer after submonolayer growth at temperatures as low as 500 degrees C. Density functional theory predictions of equilibrium Ge subsurface distributions are consistent with the measurements. We identify a surprisingly low energy pathway resulting from low interstitial formation energy in the third and fourth layers. Doping significantly affects the formation energy, suggesting that n-type doping may lead to sharper Si/Ge interfaces.

Journal Article↗

PubMed1998

Expression of proteoglycan epitopes in articular cartilage repair tissue.

To determine if expression of specific proteoglycan epitopes distinguishes articular cartilage repair tissue from normal articular cartilage, we used seven monoclonal antibodies to examine normal articular cartilage and cartilage repair tissue from osteochondral defects 3.2 mm in diameter and 4.0 mm deep in the medial femoral condyles of 27 New Zealand white rabbits and seven cynomolgus monkeys. Following creation of the osteochondral defects, one limb of each animal was treated with cast immobilization while the other limb was treated with passive motion for two weeks. Rabbit knees were examined at eight (13 animals, 26 knees) and 36 weeks (14 animals, 28 knees) and monkey knees at eight weeks (seven animals, 14 knees) following surgery. Staining for six of the antibodies did not differ between repair cartilage and normal articular cartilage, but an antibody that recognizes atypical glycosaminoglycan structures in developing tissues (MAb 7D4) consistently distinguished repair cartilage from normal cartilage in rabbits and monkeys. Repair tissue consisting of hyaline toluidine blue-staining matrix containing chondrocytic cells uniformly showed strong 7D4 staining. In contrast, normal articular cartilage and fibrous repair tissue showed inconsistent weak 7D4 staining. At eight weeks following surgery, rabbit cartilage repair tissue stained more intensely for 7D4 than monkey cartilage repair tissue; in rabbits, cartilage repair tissue stained more intensely for 7D4 at eight weeks than at 36 weeks following surgery. Repair tissue staining for 7D4 did not differ between osteochondral defects treated with passive motion and those treated with immobilization in rabbits and monkeys. These results indicate that expression of a high level of proteoglycan epitope 7D4 distinguishes hyaline articular cartilage repair tissue from normal articular cartilage and fibrous cartilage repair tissue in the early stages of osteochondral healing, and that as hyaline articular cartilage repair tissue matures expression of 7D4 decreases. The ability to characterize repair cartilage proteoglycans with monoclonal antibodies may aid in the evaluation of the quality and maturity of cartilage repair tissue and thereby facilitate improvements in procedures for resurfacing joints.

Animals↗

PubMed1997

Open reduction and bone plate stabilization, compared with closed reduction and external fixation, for treatment of comminuted tibial fractures: 47 cases (1980-1995) in dogs.

OBJECTIVE: To compare open reduction and bone plate fixation with closed reduction and external skeletal fixation as treatment for severely comminuted fractures of the tibia. Limb alignment, fracture reduction, operating time, hospitalization time, postoperative care, time to unrestricted activity, bone healing, complications, and number of surgical procedures were considered. DESIGN: Retrospective case series. ANIMALS: 47 dogs with severely comminuted fractures of the tibia treated with open reduction and bone plate application (22 dogs) or closed reduction and external fixation (25 dogs). PROCEDURE: Medical records of all dogs included in this study were reviewed. Postoperative and follow-up radiographs were evaluated by 2 independent observers. RESULTS: Differences were not found in hospitalization time, time to unrestricted activity, or time to earliest radiographic evidence of bone healing between dogs with fractures treated with a bone plate and dogs with fractures treated with an external fixator. Fractures treated with an external fixator had more caudal malalignment, and fractures treated with a bone plate had more valgus malalignment. Malalignments were determined not to be related to clinical problems. Dogs with fractures treated with an external fixator had shorter surgery times and more recheck examinations. Dogs with fractures treated with a bone plate had more complications. CLINICAL IMPLICATIONS: Open reduction with bone plate fixation and closed reduction with external fixation were both effective for treatment of comminuted tibial fractures. External fixation was associated with shorter surgery time, but dogs required more extensive postoperative care. Bone plate fixation was associated with more complications.

Animals↗

PubMed1985

Junctional epidermolysis bullosa and pyloric atresia in two siblings.

Pyloric atresia is a rare disorder that has been seen in association with epidermolysis bullosa. Two male siblings with pyloric atresia and the junctional form of epidermolysis bullosa, confirmed by electron microscopy, are described herein. These cases strengthen the relationship between junctional epidermolysis bullosa and pyloric atresia, which are probably transmitted together in an autosomal-recessive pattern.

Epidermolysis Bullosa↗