Enzymatic phosphorylation of muscle glycogen synthase: a mechanism for maintenance of metabolic homeostasis

We recently analyzed experimental studies of mammalian muscle glycogen synthesis using metabolic control analysis and concluded that glycogen synthase (GSase) does not control the glycogenic flux but rather adapts to the flux which is controlled bv the activity of the proximal glucose transport and hexokinase steps. This model did not provide a role for the well established relationship between GSase fractional activity, determined by covalent phosphorylation, and the rate of glycogen synthesis. Here we propose that the phosphorylation of GSase, which alters the sensitivity to allosteric activation by glucose 6-phosphate (G6P), is a mechanism for controlling the concentration of G6P instead of controlling the flux. When the muscle cell is exposed to conditions which favor glycogen synthesis such as high plasma insulin and glucose concentrations the fractional activity of GSase is increased in coordination with increases in the activity of glucose transport and hexokinase. This increase in GSase fractional activity helps to maintain G6P homeostasis by reducing the G6P concentration required to activate GSase allosterically to match the flux determined by the proximal reactions. This role for covalent phosphorylation also provides a novel solution to the Kacser and Acarenza paradigm which requires coordinated activity changes of the enzymes proximal and distal to a shared intermediate, to avoid unwanted flux changes.     

Incidence of pulmonary embolism after total knee arthroplasty with low-dose coumadin prophylaxis

The incidence of pulmonary embolism (PE) in osteoarthritic patients prophylaxed with low-dose coumadin after cemented total knee arthroplasty (TKA) was investigated prospectively. Each patient had a preoperative perfusion scan and a ventilation-perfusion scan on the seventh postoperative day. Pulmonary embolism was diagnosed by a high probability ventilation-perfusion scan or positive arteriogram. Patients with a moderate probability scan had an arteriogram to rule out PE. Pulmonary embolus was identified in 48 (5.6%) of 852 TKAs in 755 patients. Of these, six (0.7%) were symptomatic, and no fatal PE was identified. Age, gender, and weight did not show statistical differences comparing the PE and non-PE groups, nor did the incidences of previous PE, contralateral phlebitis, malignancy, and diabetes. A history of ipsilateral phlebitis increased the risk of PE from 5.2% to 13%, and a history of cardiac disease decreased the risk from 7.8% to 4.2%. Type of anesthesia, blood loss, tourniquet time, and prosthesis type were not significant factors. With the exception of previous contralateral phlebitis, traditional risk factors for PE were not found to increase risk of PE with low-dose coumadin prophylaxis. Spinal anesthesia that has been shown to be protective in total hip surgery was not a significant factor in this study.     

The effects of message framing on mammography utilization.

This experiment compared the effectiveness of gain- versus loss-framed messages to persuade women to obtain mammography screening. One hundred and thirty-three women 40 years and older and not adhering to current guidelines for obtaining mammography screening were assigned randomly to view either gain-framed (emphasizing the benefits of obtaining mammography) or loss-framed (emphasizing the risks of not obtaining mammography) persuasive videos that were factually equivalent. Attitudes and beliefs were measured before and immediately following the intervention. Mammography utilization was assessed 6 and 12 months later. Consistent with predictions based on prospect theory, women who viewed the loss-framed message were more likely to have obtained a mammogram within 12 months of the intervention. These findings suggest that loss-framed messages may have an advantage in the promotion of detection behaviors such as mammography. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An environmental sample chamber for X-ray microscopy

The manufacture, construction and performance of a special specimen holder for biological samples suspended in aqueous solution is described. The holder was designed for use in a scanning transmission X-ray microscope. Using it, we have successfully obtained high-resolution images of fresh cellular and subcellular specimens in suspension and have been able to vary the sample environment during viewing in the microscope.     

Computer Evaluation of Overhead Equipment for Electric Railroad Traction

The mathematical models and associated computer programs for analyzing a number of designs of overhead equipment such as simple catenary, compound catenary, stitched catenary, tunel equipment, and single-wire system, together with many possible variations are described. The programs are able to deal with up to four pantographs, and the initial conditions assumed are that the wires have their static equilibrium configurations and that the front pantograph is at the beginning of the first span touching the contact wire (or trolley wire) and moving tangentially to it. Any subsequent pantographs reach the beginning of the equipment after the start of the run and are then dealt with appropriately. The output of the programs list the input data, the total percentage contact loss between the panhead and contact wire in each span and the pantograph heights and contact forces at appropriate intervals of time. Graph plots of the pantograph heights and contact forces are also produced. The results of these programs are shown to give satisfactory agreement with previously published results obtained on a scaled model.     

Can the Randomized Controlled Trial Literature Generalize to Nonrandomized Patients?

To determine the extent to which published randomized controlled trials (RCTs) of psychotherapy can be generalized to a sample of outpatients, the authors matched information obtained from charts of patients who had been screened out of RCTs to inclusion and exclusion criteria from published RCT studies. Most of the patients in the sample who had primary diagnoses represented in the RCT literature were judged eligible for at least 1 RCT. However, many patients in the sample with substance use disorders or social anxiety disorder were not eligible for at least 2 RCTs. Common reasons that patients did not match with at least 2 published RCTs for psychotherapy included (a) patients were in partial remission, (b) patients failed to meet minimum severity or duration criteria, (c) patients were being treated with antidepressant medication, and (d) the disorder being studied was not primary (mostly for social anxiety patients). The implications of these findings for future research and clinical practice are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)