PubMed Health⌕ Search

Biomedical subjects

Thomas Morrison

Publications and source records attributed to Thomas Morrison.

3 recordsLinked to original sources
PubMed2006

Safety and efficacy of C2 pedicle screws placed with anatomic and lateral C-arm guidance.

STUDY DESIGN: This is a retrospective review of 150 C2 pedicle screw placements. Candidates had their C2 pedicle morphology assessed through three-dimensional imaging, including preoperative image guidance. After surgery, the patients were serially CT scanned. Follow-up, with fusion assessment, ranged from 1 to 12 years. OBJECTIVE: We will show that an open technique combined with lateral C-arm guidance provides rapid placement of C2 pedicle screws. SUMMARY OF BACKGROUND DATA: C2 pedicle screws can be successful anchors for a variety of cervical problems. Standard intraoperative image guidance, biplane fluoroscopy, or free hand techniques all have their drawbacks. METHODS: After adequate C2 exposure, the C2 pedicle is palpated. The dissector remains stationary to provide coronal orientation while a lateral C-arm radiograph is obtained for sagittal orientation. The drill trajectory is set, the C2 pedicle cannulated, and a cancellous screw placed. RESULTS: A total of 71 patients had bilateral screws placed and 8 patients had unilateral screws placed. The overall complication rate was 2.7%. CONCLUSIONS: In our series, we have found a consistent way to cannulate the C2 pedicle. C2 fixation serves as an integral part of cervical reconstruction. Preoperative planning, anatomic knowledge, and lateral C-arm orientation create a low morbidity method for C2 screw placement.

Adolescent↗
PubMed2004

Metformin (Glucophage) inhibits tyrosine phosphatase activity to stimulate the insulin receptor tyrosine kinase.

Metformin is a commonly used anti-diabetic but whether its mechanism involves action on the insulin receptor or on downstream events is still controversial. With a time course that was slow compared with insulin action, metformin increased tyrosine phosphorylation of the regulatory domain of the insulin receptor (specifically, tyrosine residues 1150 and 1151). In a direct action, therapeutic levels of metformin stimulated the tyrosine kinase activity of the soluble intracellular portion of the beta subunit of the human insulin receptor toward a substrate derived from the insulin receptor regulatory domain. However, metformin did not alter the order of substrate phosphorylation by the insulin receptor kinase. Using a Xenopus oocyte preparation, we simultaneously recorded tyrosine kinase and phosphatase activities that regulate the insulin receptor by measuring the tyrosine phosphorylation and dephosphorylation of peptides derived from the regulatory domain of the human insulin receptor. In an indirect stimulation of the insulin receptor, metformin inhibited endogenous tyrosine phosphatases and purified human protein tyrosine phosphatase 1B that dephosphorylate and inhibit the insulin receptor kinase. Thus, there was evidence that metformin acted directly upon the insulin receptor and indirectly through inhibition of tyrosine phosphatases.

Animals↗