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Biomedical subjects

M E Cooke

Publications and source records attributed to M E Cooke.

9 recordsLinked to original sources
PubMed1996

Effect of antisense oligonucleotides on cytokine release from human keratinocytes in an in vitro model of skin.

ISIS 1082, a phosphorothioate oligonucleotide 21 nucleotides in length targeted to the translation initiation codon of herpes simplex virus (HSV) type 1 and 2 virion capsid protein, has been shown to inhibit HSV-1 replication in vitro. The effects of ISIS 1082, its phosphodiester congener, ISIS 1049, and analogs consisting of 2' methoxy and 2' propoxy phosphodiesters and phosphorothioates on IL-1 alpha release and viability were evaluated in a three-dimensional in vitro skin model consisting of neonatal keratinocytes and fibroblasts. This in vitro system displays many of the functional and metabolic properties of a differentiated epidermis and can be induced to specifically release IL-1 alpha in response to a mixture of lipopolysaccharide and phorbol myristate acetate. Incubation of the skin model with 250 to 1000 microM concentrations of ISIS 1082 and its 2' methoxy and propoxy phosphorothioate analogs resulted in a concentration-dependent increase of cytokine release with minimal effects on cellular viability, as measured by the Neutral Red assay. This response was confirmed in primary keratinocytes, which were also shown to secrete IL-1 alpha into media supernatants after incubation with phosphorothioate oligomers. These data suggest that the IL-1 alpha released from keratinocytes in response to ISIS 1082 may contribute to the inflammatory and immune cell response seen in vivo.

Antiviral Agents↗
PubMed1995

In vitro pharmacokinetics of phosphorothioate antisense oligonucleotides.

ISIS 2105 (Afovirsen), a 20-mer phosphorothioate oligonucleotide that inhibits the production of a gene product essential to the growth of human papillomavirus, is in phase II clinical trials for the treatment of genital warts induced by human papillomavirus-6 and human papillomavirus-11. The uptake, subcellular distribution and metabolism of ISIS 2105 and three other similar length phosphorothioates have been studied in a variety of cell lines. Our experiments indicated that ISIS 2105 and other phosphorothioates are internalized and distributed in a time-, temperature-, concentration-, sequence- and cell line-dependent manner. Cell association was also influenced by the tissue culture medium. Several different analytical techniques revealed that phosphorothioates were more rapidly degraded in vitro than previously reported. These data suggest that phosphorothioate oligonucleotide uptake and stability observed in tissue culture can vary as a function of cellular assay conditions and analytical methods used. Comparison of these results with those obtained in vivo suggests that the pharmacokinetic behavior of this class of compounds cannot necessarily be predicted from in vitro studies.

Animals↗
PubMed1994

Anterior cervical discectomy and fusion using a porous hydroxyapatite bone graft substitute.

OBJECTIVES: This study analyzed the use of a coral hydroxyapatite bone substitute for use in ACDF both with and without an anterior cervical plate. STUDY DESIGN: The healing of multilevel anterior cervical fusions was tested using a goat model. Comparisons were drawn with histologic, radiographic, and biomechanical test data. METHODS: Forty-nine mature alpine goats had three-level anterior discectomies performed. Seven treatment groups of seven goats each were used; Group I with no fusion, Group IIa having tricortical iliac crest autograft, Group IIb having autograft plus an anterior plate, Group IIIa having tricortical iliac crest fresh-frozen allograft, Group IIIb having allograft plus an anterior plate, Group IVa having rectangular-shaped implants of porous hydroxyapatite, and Group IVb having ProOsteon 500 implants with an anterior cervical plate. RESULTS: Histologically, at 12 weeks 48% of the ProOsteon (Interpore, Irvine, CA) implants were rated as incorporated, 10% as possessing a fibrous gap, 29% as collapsed, and 14% as extruded. Anterior cervical plating improved the results with 71% of the implants showing good incorporation, 24% with collapse, and 5% with a fibrous gap. These histologic results compare favorably with autogenous bone and are improved over allograft bone. Fluorochrome analysis showed that none of the implants had complete turnover with host bone, but that all possessed peripheral creeping substitution with cutting cones of new bone formation at 12 weeks. Biomechanically, the spines using the ProOsteon implant were less stiff in torsion than autograft, but equal in stiffness to allograft. Flexion-extension neutral zone stiffness was lower in the ProOsteon implant group than either allograft or autograft. CONCLUSIONS: The use of a coral-based hydroxyapatite bone graft substitute for anterior cervical fusions led to significant rates of implant collapse at 12 weeks but showed excellent biologic compatibility with good early creeping substitution of the implant by host bone. The concomitant use of an anterior cervical plate with the implant prevents extrusion.

Animals↗
PubMed1993

Anterior cervical discectomy, fusion, and plating. A comparative animal study.

Thirty-five goats were used as animal models for three-level anterior cervical discectomy and fusion. The goats were divided equally into five experimental groups: Group I, three-level anterior cervical discectomy without fusion; Group IIa, three-level discectomy with autogenous bone (Smith-Robinson technique); Group IIb, autogenous bone grafting plus anterior plate application; Group III, three-level discectomy and fusions with fresh frozen allograft bone; Group IIIa, graft only; and Group IIIb, anterior plating. The goats were killed, and spines were removed and analyzed for evidence of fusion. Radiographic union was judged to have occurred in 0% of Group I disc spaces, 48% of Group IIa, 52% of Group IIb, and 38% of Groups IIIa and IIIb. Histologic fusion was judged to have occurred in 0% of Group I specimens, 38% of Group IIa, 45% of Group IIb, 0% of Group IIIa, and 19% of Group IIIb. The histologic fusion rate was significantly higher in Groups IIa and IIb than in Groups I and IIIa. There was no statistically significant increase in the histologic fusion rate between goats with anterior cervical plating and goats without plating. Biomechanically, the spines in Groups IIb and IIIb, ie, those with anterior plates applied, were stiffer in axial load, torsion, and flexion/extension. Peri-end-plate vascularity was significantly diminished in those groups that had anterior plates applied. Qualitative analysis of fluorochrome labels showed that autografts revascularized more rapidly than did allografts in both the nonplated and plated groups. Histomorphometric analysis failed to reveal any significant device-related osteopenia in those vertebrae spanned by the anterior plate. We found that although autograft bone led to a significantly higher rate of union than did allograft bone, the addition of anterior plate fixation did not significantly increase union rate. Biomechanical rigidity was significantly increased in all modes of testing by the use of an anterior plate. The decreased vascular response seen in spines that underwent plating may be responsible for the lack of increased union. The increased rigidity found with anterior plating supports its use in traumatic conditions. The failure, however, to increase significantly the union rate in this model fails to lend support to the use of anterior cervical plating for degenerative discectomy and fusion procedures.

Animals↗
PubMed1993

Pedicle screw pullout strength. Correlation with insertional torque.

This study was designed to correlate several parameters regarding pedicle screw bone/metal interface strength. The insertional torque measured during tapping and placement of pedicle screws was correlated with the bone mineral density of the vertebral body, the dimensions of the pedicle, the method of preparation of the pedicle, and the amount of load and number of cycles to failure of the bone/metal interface. Thirty human cadaveric lumbar vertebrae were instrumented with 6.5-mm pedicle screws. The maximum torque achieved during insertion was digitally recorded. A cyclic pedicle screw pullout test was performed. A linear correlation existed between both the insertional torque when tapping or when inserting a screw and the number of cycles to ultimate pedicle screw pullout. An inverse linear relationship was found between the pedicle width and cycles to failure. There was no linear correlation found when comparing the number of cycles to failure to bone mineral density. These findings suggest that insertional torque is a good predictor of bone-metal interface failure. Bone mineral density of the vertebral body was less effective as a predictor of failure. Smaller pedicle width correlated with increased insertional torque and cycles to failure. This may explain why patients with osteoporosis on radiography may still obtain stable fixation with pedicle screws. Other factors, such as pedicle dimensions and shape, affect screw purchase as much as vertebral body bone density. Insertional torque less than 4.0 inch-pounds led to early pedicle screw pullout. This study forms the basis for the authors' clinical use of an instrumented torque screwdriver to measure insertional torque in the operating room.

Aged↗
PubMed1993

Spinal instrumentation for metastatic disease: in vitro biomechanical analysis.

A calf spine corpectomy model was employed to compare the ability of various spinal instrumentation techniques to restore stability after destruction of the anterior and middle columns. The constructs tested were an intact specimen, a Harms titanium cage, a cross-linked rectangular anterior Texas Scottish Rite Hospital construct, posterior segmental Luque rods combined with a cross-linked rectangular anterior TSRH construct, posterior Luque rods alone, cross-linked posterior Luque rods, and posterior Luque rods embedded in polymethyl-methacrylate (PMMA). When compared to the intact state, only the combined anterior/posterior construct and the anterior TSRH construct were able to restore axial, sagittal, and torsional stiffnesses to levels equal to or higher than control levels. Embedding Luque rods in PMMA provided greater stiffness than either Luque rods alone or cross-linked Luque rods. If the anterior and middle columns of the spine are incompetent, as frequently occurs with metastatic disease, the goal of surgical treatment is to restore spinal stability while decompressing the neural elements. Either anterior or posterior techniques may be used. The findings of this study imply that commonly used spinal instrumentation constructs differ in their ability to restore axial, sagittal, and torsional stiffnesses to normal levels.

Animals↗
PubMed1992

Citrate is a major component of snake venoms.

Citrate has been identified as a major component of snake venoms by gas liquid chromatography and mass spectrometry. The venoms of Bothrops asper, Crotalus atrox, Crotalus viridis viridis, Crotalus adamanteus, Sistrurus miliarius barbouri, Crotalus horridus horridus, Agkistrodon contortrix mokasen, Agkistrodon contortrix contortrix and Agkistrodon piscivorus piscivorus contain citrate at concentration levels which can serve as effective buffers. Calcium, magnesium, zinc, iron, sodium and potassium salts of citrate would be constituents of venom.

Animals↗
PubMed1992

Anterior cervical discectomy and fusion. A comparison of techniques in an animal model.

An animal model for three-level anterior cervical discectomy and fusion was established in the goat. Twenty-one goats underwent surgery, with seven goats in each of three experimental groups. In Group I, all seven goats underwent three-level anterior cervical discectomy without fusion. In Group II, each of the seven goats had a three-level discectomy with autogenous bone performed according to the Smith-Robinson technique. In Group III, fresh-frozen allograft bone was used for each of the three-level discectomy and fusion. Each goat was then killed after 12 weeks. Analysis consisted of radiographic review, fluorochrome labeling, biomechanical rigidity and flexion and extension, axial compressive load, and torsion. Histologic analysis was also performed for evidence of fusion and vertebral body histomorphometric analysis. The analysis of results showed that radiographic union was judged to have occurred in 0 of 21 Group I disc spaces, 10 of 21 Group II disc spaces, and 8 of 21 Group III disc spaces. Histologic fusion was judged to have occurred in 0 of 21 Group I goats, 10 of 21 Group II goats, and 0 of 21 Group III goats. The histologic fusion rate was significantly higher in Group II than either Group I or Group III. Biomechanically, the spines that had autogenous bone grafting (Group II) were significantly stiffer in compressive axial load and in extension. Both Group II and Group III were stiffer in flexion than Group I. An evaluation of the peri-endplate vascularity showed that the vascularity measured 10.4% in Group I, 16.7% in Group II, and 8.5% in Group III.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗