On the change in bacterial size and magnetosome features for Magnetospirillum magnetotacticum (MS-1) under high concentrations of zinc and nickel.

The characteristic size, shape and specific alignment of magnetite crystals synthesized by magnetotactic bacteria is a highly coordinated process with precise control over magnetosome vesicle formation, uptake and transport of Fe, and magnetite biomineralization. Magnetosome membranes along with some specific membrane proteins regulate crystal nucleation and morphology of magnetite. Several previous works have indicated that the morphology of mature magnetite crystals is largely unaffected by environmental conditions, though some recent studies have shown the possibility of manipulation of the biomineralization process. In this study we have examined the effects of high concentrations of Zinc and Nickel on the growth of Magnetospirillum magnetotacticum (MS-1) and the corresponding magnetosome formation. Using various characterizations it is shown that the growth of the bacterial cells, as well as the size, shape and magnetosome chain alignment is significantly influenced in the presence of high concentrations of Zn or Ni.

Environment-Responsive Polymers for Coating of Pharmaceutical Nanocarriers(,).

Polyethylene glycol derivatives, such as block copolymers of polyethylene glycol and diacyllipids (for example, phosphatidylethanolamine) are widely used for surface modification of various pharmaceutical carriers in order to impart them longevity in the body. To make polyethylene glycol detachable from the surface of pharmaceutical carrier and facilitate the interaction of the carrier with target cells when in pathological zone, we have prepared a set of polyethylene glycol-phosphatidylethanolamine block copolymers with the pH sensitive hydrazone bond between polyethylene glycol and phosphatidylethanolamine, which destabilizes at lowered pH values typical for tumors and inflammation zones. We have demonstrated that the stability of the hydrazone bond at normal physiological pH (7.4) as well as the rate of its hydrolysis at pH 6 and below strongly depend on the type of substitutions at this bond. Using aliphatic and aromatic aldehydes and ketones, polyethylene glycol-phosphatidylethanolamine block copolymers were prepared with different stabilities and degradation rates, which can be useful in constructing stimuli-sensitive pharmaceutical carriers.

Hip arthroplasty with a collared straight cobalt-chrome femoral stem using second-generation cementing technique: a 10-year-average follow-up study.

Clinical and radiographic results of 116 patients who had undergone 132 hip arthroplasties at our institution from 1983 to 1988 with a collared cemented straight cobalt-chrome femoral stem using second-generation cementing technique were reviewed. Twenty hips in 20 patients who were part of the original cohort were lost to follow-up. Mean age at the time of surgery was 68.2 years. Mean radiographic follow-up was 9.6 years with a minimum follow-up of 5 years. Ten-year survivorship of the component was 96.5% with revision considered as an endpoint and 94.2% with either revision or radiographic loosening considered the endpoint. Three implants (2.3%) were revised for aseptic loosening at a mean of 8.1 years after implantation. One implant (0.8%) was revised for septic loosening at 10.5 years after surgery. Of the implants not revised, 1 showed evidence of circumferential bone-cement radiolucencies, and 1 had radiolucencies at the implant-cement interface. Five of the surviving femoral components (5.0%) showed focal areas of cystic osteolysis, and proximal femoral bone resorption under the collar was seen in 32 patients (31.7%). There were no cases of cement fracture or stem subsidence. The biomechanical and material properties of this stem combined with second-generation cementing technique look promising for long-term survivorship.

Technical pitfalls of meniscal surgery.

Meniscal surgery is one of the most common orthopedic procedures performed today. Orthopedic surgeons must be familiar with the indications for meniscal excision versus repair and comfortable with the diverse instrumentation used for both techniques. Numerous pitfalls exist in diagnosis, indication, and technical aspects of surgery but can be minimized or avoided by careful preoperative planning and attention to detail during the surgical procedure.

Effect of demineralized bone matrix on polymorphonuclear leukocyte degranulation.

The potential use of allogenic demineralized bone matrix to augment or treat bone defects or nonunions in animals and humans is currently being investigated. Demineralized bone matrix induces osteogenesis by a multistep cascade of endochondral ossification that is mediated by bone-induction factors. The migration and activation of polymorphonuclear leukocytes appear to be critical in the initiation of the cascade of osteogenesis induced by demineralized bone matrix. This study examined the effects of demineralized bone matrix on the degranulation of polymorphonuclear leukocytes. Demineralized bone matrix stimulated the release of polymorphonuclear leukocyte-specific, but not azurophilic, granules in a time and dose-dependent manner. The ability of the bone matrix to induce this degranulation was independent of its size and species. The mechanism by which this degranulation occurs is not completely understood; however, it is known that it does not occur by means of a receptor that requires guanidine triphosphate-dependent regulatory proteins as does polymorphonuclear-leukocyte degranulation induced by N-formyl peptide. The factor that stimulates degranulation is not type-I collagen but rather appears to be a cytokine that has a heparin-binding domain and a molar mass of 10-70 kDa. Loss of the ability of demineralized bone matrix to induce degranulation of polymorphonuclear leukocytes correlated positively with the loss of its ability to induce bone formation.

Up-regulation of inducible nitric oxide synthase and production of nitric oxide by the Swarm rat and human chondrosarcoma.

Production of nitric oxide by solid tumors may have important ramifications regarding tumor growth and potential metastasis. This study demonstrated that the chondrosarcoma of the Swarm rat has upregulated mRNA for inducible nitric oxide synthase and produces nitric oxide. These results were confirmed by (a) the presence of a 4.4-kb band of mRNA detected by Northern blot using a probe for inducible nitric oxide synthase, (b) a 133-kDa band of protein that was detected with either a polyclonal or monoclonal antibody to the inducible nitric oxide synthase of the murine macrophage, and (c) the detection of nitrites from the culture medium of freshly cultured, isolated chondrosarcoma cells. This study showed that the expression of inducible nitric oxide synthase and the production of nitric oxide by the tumor can be increased by stimulation with endotoxin lipopolysaccharide and can be inhibited by inducible nitric oxide synthase inhibitors (L-N(g)-monomethyl arginine and aminoguanidine). Immunostaining confirmed the presence of inducible nitric oxide synthase within the tumor cells and appeared to localize the enzyme to the cytoplasm of the cells. A human chondrosarcoma was also shown to have an upregulated inducible nitric oxide synthase by both the detection of mRNA for inducible nitric oxide synthase and the presence of nitrites from the culture medium of the tumor in organ culture. Because the chondrosarcoma of the Swarm rat is a well differentiated solid tumor that rarely metastasizes, nitric oxide may be produced by the tumor to promote local growth by effects on vascular supply.

Results of cemented metal-backed acetabular components: a 10-year-average follow-up study.

The clinical and radiographic results of 86 primary total hip arthroplasties performed in 74 patients from 1983 to 1987 with a cemented metal-backed acetabular component and a cemented collared straight femoral stem with a 32-mm head were reviewed at a mean follow-up of 10.1 years. Seven patients (9.2%) underwent acetabular component revision at a mean of 9.0 years after implantation; an additional 24 components (31.6%) demonstrated evidence of radiographic loosening, resulting in a total failure rate of 40.8%. Periacetabular radiolucencies were noted in Charnley zones at the following rates: 34.2% in zone I, 18.4% in zone II, and 27.6% in zone III. In addition, 18.4% and 38.2% of implants demonstrated evidence of migration and excessive polyethylene wear. Excessively vertical cup placement (>49 degrees inclination) at the time of initial arthroplasty was statistically correlated with polyethylene wear, implant migration, and fixation failure. A trend of increasing implant failure was also noted with decreasing polyethylene liner thickness. Periacetabular cement mantle thickness was not statistically correlated with subsequent component loosening or failure. Results of Kaplan-Meier survivorship analysis using revision as an endpoint showed 93.6% survivorship at 10 years and 88.4% at 12 years. The mean modified Harris hip scores were 46.9 preoperatively and 81.8 at final follow-up. The significant overall rates of radiographic loosening, migration, polyethylene wear, and implant revision confirm the suspected trend of increasing failure rates of cemented metal-backed acetabular components over time.

Osteoinductive agents. Basic science and clinical applications.

Demineralized bone matrix (DBM) is well characterized as an osteoinductive agent. This article reviews the historical perspectives and current body of knowledge on the mechanisms of induced osteogenesis and the factors contained within DBM, which can induce bone formation. The use of DBM and osteoinductive agents to treat bone defects and nonunions in both animal models and human conditions in orthopedic and reconstructive surgery are discussed.

Tendon extracellular matrix contains pentameric thrombospondin-4 (TSP-4).

In preparations of cartilage oligomeric matrix protein (COMP) from bovine tendon two contaminating polypeptides of 120 and 135 kDa were detected. N-terminal protein sequencing of these polypeptides showed homology to the N-terminus and to an internal sequence in TSP-4, respectively. TSP-4 was further enriched by heparin affinity chromatography. Electron microscopy of this sample shows primarily five armed particles with globular domains at the periphery connected to a central assembly domain in which smaller N-terminal globular domains can be resolved tightly packed at the center of the particle. We can thereby confirm the pentameric model for TSP-4 proposed by Lawler et al. [(1995) J. Biol. Chem. 270, 2809-2814], on the basis of recombinantly expressed protein. We further show that TSP-4 is abundant in tendon.