Biomedical subjects
L E Weiss
Publications and source records attributed to L E Weiss.
Characterization of osteoblast-like behavior of cultured bone marrow stromal cells on various polymer surfaces.
The creation of novel bone substitutes requires a detailed understanding of the interaction between cells and materials. This study was designed to test certain polymers, specifically poly(caprolactone) (PCL), poly(D,L-lactic-CO-glycolic acid) (PLGA), and combinations of these polymers for their ability to support bone marrow stromal cell proliferation and differentiation. Bone marrow stromal cells were cultured from New Zealand White rabbits and were seeded onto glass slides coated with a thin layer of PCL, PLGA, and combinations of these two polymers in both a 40:60 and a 10:90 ratio. Growth curves were compared. At the end of 2 weeks, the cells were stained for both matrix mineralization and alkaline phosphatase activity. There was no statistically significant difference in growth rate of the cells on any polymer or polymer combination. However, there was a striking difference in Von Kossa staining and alkaline phosphatase staining. Cells on PCL did not show Von Kossa staining or alkaline phosphatase staining. However, in the 40:60 and 10:90 blends, there was both positive Von Kossa and alkaline phosphatase staining. These data indicate that PCL alone may not be a satisfactory material for the creation of a bone substitute. However, it may be used in combination with PLGA for the creation of a bone substitute material.
Stent-based gene therapy.
Delivery of gene therapy to inhibit intimal hyperplasia has been proposed to prevent postangioplasty restenosis. We sought to apply gene therapy by using a stent-based technique. There are several hurdles that must be overcome before gene-stent therapy can be applied successfully in clinical trials. These include increasing the efficiency of gene delivery through atherosclerotic plaque; increasing intramural retention times; preventing the inflammatory reaction that stents coated with biodegradable polymers can elicit; overcoming the risk of systemic gene delivery; and accessing the adventitia via percutaneous approach. We evaluated a gene-stent delivery mechanism based on microporous metal microneedles developed with nanotechnology in an attempt to overcome some of these problems. A novel approach to the transfection of genes by microfabricated technology was evaluated in smooth muscle cells in culture. We demonstrated that microneedles can deliver gene therapy to smooth muscle cells in culture and can produce controlled penetration of the IEL and intima. We conclude that taller microneedles need to be developed to reach the media in diseased human arteries and that this technology has the potential to be incorporated in a stent to deliver gene therapy in atherosclerotic plaque.
Lunotriquetral injuries in the athlete.
The athlete with an LT injury typically presents with ulnar-sided wrist pain after a high-energy impaction of the wrist. Reagan's LT ballottement test and Kleinman's shear test help the examiner identify these injuries. A thorough radiographic examination includes standard PA and lateral radiographs. Magnetic resonance imaging or arthrography can be performed, but the sensitivity of these imaging studies varies. The palmar portion of the LT interosseous ligament, dorsal radiocarpal ligament, and dorsal intercarpal ligament play the most significant roles in LT stability. Lunotriquetral injuries without instability respond well to immobilization. Arthroscopy is valuable in staging and determining treatment but requires a thorough radiocarpal and midcarpal examination. Acute LT injuries with instability are treated with arthroscopic-assisted reduction and pinning. If desired, this procedure can be incorporated with an open ligament repair through a volar approach. Chronic LT tears without instability can also be treated arthroscopically. Treatment of the chronic LT tear with instability depends on the degree of collapse. Treatment in the athlete includes ligament reconstruction with capsulodesis or, rarely, intercarpal LT arthrodesis.
In vitro analysis of biodegradable polymer blend/hydroxyapatite composites for bone tissue engineering.
Blends of biodegradable polymers, poly(caprolactone) and poly(D, L-lactic-co-glycolic acid), have been examined as scaffolds for applications in bone tissue engineering. Hydroxyapatite granules have been incorporated into the blends and porous discs were prepared. Mechanical properties and degradation rates in vitro of the composites were determined. The discs were seeded with rabbit bone marrow or cultured bone marrow stromal cells and incubated under physiological conditions. Polymer/ceramic scaffolds supported cell growth throughout the scaffold for 8 weeks. Scanning and transmission electron microscopy, and histological analyses were used to characterize the seeded composites. This study suggests the feasibility of using novel polymer/ceramic composites as scaffold in bone tissue engineering applications.
Percutaneous and arthroscopic screw fixation of scaphoid fractures in the athlete.
The authors prefer to treat nondisplaced acute scaphoid fractures in the athlete on an individualized basis. Percutaneous or arthroscopic-assisted fixation are valuable techniques to employ when prolonged immobilization is a concern. Return to athletic competition has been rapid using these methods. Morbidity has been minimal, and there have been no nonunions to date at the authors' institution.
Micromechanical devices for intravascular drug delivery.
Microfabrication technology, more commonly applied to the manufacture of integrated circuits, can be used to build devices useful for mechanical delivery of drugs and genes. Microprobes fabricated using silicon micromachining have been used to deliver DNA into cells as an alternative to bombardment and microinjection. This idea can be extended to intravascular stents with integrated microprobes capable of piercing compressed plaque and delivering anti-restenosis therapies into coronary arteries. Preliminary experiments using filleted rabbit arteries have demonstrated transection of the internal elastic lamina. New nonplanar microfabrication technologies are necessary for creating practical devices with cylindrical symmetry; a promising possibility is to use microfabricated structures of anodic metal oxides.
Workshop report on Hodgkin's disease and related diseases ('grey zone' lymphoma).
Despite advances in immunohistochemistry and molecular biology, the distinction between classical Hodgkin's lymphoma and related diseases such as nodular lymphocyte-predominant Hodgkin's disease, T-cell rich large B-cell lymphoma or anaplastic large cell lymphoma has remained difficult in rare cases. Lack of clear-cut diagnostic criteria represents a problem for both the pathologist and the clinician. To delineate this 'grey zone' between classical Hodgkin's lymphoma and non-Hodgkin's lymphoma (NHL) and to develop criteria for classification of such cases, 12 expert hematopathologists each submitted one to five borderline cases to a workshop. Cases were reviewed and classified at a multiheaded microscope and criteria were established for the diagnosis of questionable cases. Well established entities such as classical Hodgkin's lymphoma, anaplastic large-cell lymphoma and TCRBCL were defined more strictly and cases with unusual morphology or antigen expression could be identified. A distinctive subset of cases representing mediastinal large B-cell lymphomas with features of Hodgkin's lymphoma was identified.
Pseudarthrosis after postoperative wound infection in the lumbar spine.
This retrospective investigation attempts to define the incidence of fusion success after postoperative infection after a posterior lumbar fusion, as well as which risk factors may adversely affect arthrodesis after successful debridement. At an average follow-up of 37 months, 18 of 29 patients (62.1%) had a successful arthrodesis. Eighty-seven percent of patients whose fusion excluded the sacrum had a solid arthrodesis, compared with only 36% of those fusions including the sacrum. The fusion rate in female patients was 33.3%, compared with 82.4% in male patients. The rate of fusion with allograft bone was 17.2 versus 83.3% with autograft bone. Female sex, the use of allograft bone, and extension of the fusion mass to the sacrum significantly increase the incidence of nonunion after a postoperative deep spinal wound infection.
Developmental pattern of 3-hydroxy-3-methylglutaryl coenzyme A reductase in the rat.
The activity, protein concentration and catalytic efficiency of hepatic 3-hydroxy-3-methylglutaryl coenzyme A reductase was determined in rats aged 1 to 199 days. Microsomal enzyme total activity peaked on day 24, during weaning, and again on day 63, during the onset of puberty. Increased enzyme activity during weaning resulted primarily from an increase in the catalytic efficiency of the enzyme with a slight reduction in enzyme protein content. The rise in enzyme activity during the onset of puberty, however, was primarily the result of an increase in enzyme protein concentration. Thus, the activity of reductase in mammalian livers reflects, at different stages in development, the modulating influence of both the total number of reductase molecules and the catalytic efficiency of the enzyme.
Gallium-67 citrate in human tumors. Ultrastructural localization by autoradiography.
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