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Biomedical subjects

S A Jackson

Publications and source records attributed to S A Jackson.

At least 55 records · Page 3Linked to original sources
PubMed1993

Coping strategies used by national champion figure skaters.

This investigation had two purposes: (a) to identify and describe the coping strategies used by national champion figure skaters and (b) to examine the relationship between coping strategies and particular stress sources. Participants were 17 of 20 (85%) Senior U.S. National Champion figure skaters who won titles between 1985 and 1990. All skaters were interviewed, and the interview transcripts were content analyzed. General coping dimensions reported by at least 40% of the skaters included (a) rational thinking and self-talk, (b) positive focus and orientation, (c) social support (e.g., receiving support from coach, talking with friends and family), (d) time management and prioritization, (e) precompetitive mental preparation and anxiety management (e.g., relaxation, visualization), (f) training hard and smart, (g) isolation and deflection (e.g., not letting things get to me, avoiding/screening media), and (h) ignoring the stressor(s). It was also found that the skaters implemented different coping strategies depending on the specific stressors encountered.

Adaptation, Psychological↗
PubMed1993

Coping strategies used by U.S. Olympic wrestlers.

Extensive in-depth interviews were conducted with all 20 members of the 1988 U.S. Olympic Wrestling Team regarding their efforts to cope with stress experienced during the Seoul Olympics. Qualitative analyses revealed that the wrestlers employed a variety of coping strategies including: (a) thought control strategies (blocking distractions, perspective taking, positive thinking, coping thoughts, and prayer), (b) task focus strategies (narrow, more immediate focus, concentrating on goals), (c) behavioral based strategies (changing or controlling the environment, following a set routine), and (d) emotional control strategies (arousal control, visualization). In accordance with the observations of Compas (1987) and Folkman and Lazarus (1985), the coping efforts of the Olympic wrestlers were not limited to particular strategies nor to single approaches to dealing with a particular stressor but, rather, reflected a dynamic complex process involving a number of strategies, often in combination. The results also suggested that the degree to which coping strategies are well learned or automatized is related to their perceived effectiveness.

Adaptation, Psychological↗
PubMed1993

High-resolution CT of the chest: radiation dose.

OBJECTIVE: The purpose of this study was to compare the skin radiation dose to the chest produced by high-resolution CT (HRCT) with the radiation dose produced by conventional CT. Previous studies have reported that radiation doses with HRCT are equal to or higher than those with conventional CT. These results, however, were based on the assumption that in HRCT, contiguous sections were scanned without the intersection gaps of 10 or 20 mm that are used clinically. SUBJECTS AND METHODS: We used radiotherapy verification film to measure the skin radiation dose in 56 patients who had chest CT scans. Twenty-two had 1.5-mm collimation HRCT scans at 10-mm intervals, 15 had 1.5-mm collimation HRCT scans at 20-mm intervals, and 19 had 10-mm collimation conventional CT scans at 10-mm intervals. Scan parameters were identical in all cases: 120 kVp, 200 mA, 2 sec. Step wedges were used to generate calibration films with identical beam quality on the CT scanner, and exposure was measured with an ionization chamber. Calibration films and patients' radiotherapy verification films were digitized, and the radiation dose was calculated. RESULTS: Mean skin radiation dose was 4.4 (standard error [SE], 0.2) mGy for 1.5-mm HRCT scans at 10-mm intervals, 2.1 (SE, 0.1) mGy at 20-mm intervals, and 36.3 (SE, 0.9) mGy for conventional 10-mm scans at 10-mm intervals. CONCLUSION: HRCT scanning at 10- and 20-mm intervals produced 12% and 6%, respectively, of the radiation dose associated with conventional CT. This is considerably less radiation than suggested in earlier studies. Combining HRCT scans at 20-mm intervals with low-dose scan (20 mA, 2-sec scans) would result in an average skin dose comparable with the dose administered with chest radiography.

Adult↗
PubMed1993

The effect of dopamine on graft function in patients undergoing renal transplantation.

We studied the effect of a low-dose dopamine infusion on graft function in 60 patients undergoing transplantation with cadaveric kidneys in a prospective controlled trial. Recipients were allocated to either a control or a dopamine group, the latter receiving a 3 micrograms.kg-1 x min-1 infusion of dopamine starting intraoperatively. Evaluation of dopamine's effect was undertaken in two stages, namely, (i) initial graft function 1 wk after transplantation and (ii) graft survival at 3 mo. Initial graft function was determined by the ability of the transplanted kidney to reduce serum creatinine, and the development of acute tubular necrosis as confirmed by renal biopsy. Of the dopamine group 33.3% developed acute tubular necrosis compared to 23.3% of the control group. The second-stage evaluation was based on plasma creatinine levels and the requirement for dialysis within 3 mo of transplantation. 92.8% of the dopamine group and 76.9% of the control group had good graft function. No statistically significant difference between the two groups was found. The perioperative infusion of dopamine at 3 micrograms.kg-1 x min-1 was not shown to have any beneficial effect on the transplanted kidney in patients who do not have serious vascular disease, or who do not receive kidneys subjected to prolonged hypotension or prolonged preservation or anastomotic times.

Adolescent↗
PubMed1992

Aerobic heat shock activates trehalose synthesis in embryos of Artemia franciscana.

Encysted embryos (cysts) of the brine shrimp, Artemia franciscana, contain large amounts of trehalose which they use as a major substrate for energy metabolism and biosynthesis for development under aerobic conditions at 25 degrees C. When cysts are placed at 42 degrees C (heat shock) these pathways stop, and the cysts re-synthesize the trehalose that was utilized during the previous incubation at 25 degrees C. Glycogen and glycerol, produced from trehalose at 25 degrees C, appear to be substrates for trehalose synthesis during heat shock. Anoxia prevents trehalose synthesis in cysts undergoing heat shock. These results are consistent with the view that trehalose may play a protective role in cells exposed to heat shock, and other environmental insults, in addition to being a storage form of energy and organic carbon for development.

Animals↗
PubMed1992

Identification of novel peptide antagonists for GPIIb/IIIa from a conformationally constrained phage peptide library.

Methods have recently been developed to present vast libraries of random peptides on the surface of filamentous phage. To introduce a degree of conformational constraint into random peptides, a library of hexapeptides flanked by cysteine residues (capable of forming cyclic disulfides) was constructed. This library was screened using the platelet glycoprotein, IIb/IIIa, which mediates the aggregation of platelets through binding of fibrinogen. A variety of peptides containing the sequence Arg-Gly-Asp or Lys-Gly-Asp were discovered and synthesized. The cyclic, disulfide-bonded forms of the peptides bound IIb/IIIa with dissociation constants in the nanomolar range, while reduced forms or an analogue in which Ser replaced the Cys residues bound considerably less tightly. These results demonstrate the feasibility for introducing conformational constraints into random peptide libraries and also demonstrates the potential for using phage peptide libraries to discover pharmacologically active lead compounds.

Amino Acid Sequence↗
PubMed1992

Regional observer performance variation in the evaluation of gated cardiac blood pool studies.

Receiver operating characteristic (ROC) analysis demonstrated that regional variations of sensitivity exist in the detection of wall motion abnormality in cardiac blood pool imaging studies. The observer response is significantly better in the apex than either the septum or posterolateral wall segments. The observer errors tend to be false-negative in the posterolateral wall segment and false-positive in the other two segments. Image presentation can make a significant difference to the overall sensitivity, and the monochrome cine-sequence performed best in this study.

Gated Blood-Pool Imaging↗
PubMed1992

Evaluation of a personal computer-based quantitative coronary analysis system for rapid assessment of coronary stenoses.

Quantitative coronary analysis (QCA) is a technique that is rarely used because of the complexity and expense of existing systems. We studied a new personal computer-based QCA system that is capable of both geometric and densitometric analysis and compared it to a previously validated QCA system. Both systems performed extremely well in phantom analysis with 11 phantoms filmed in both 5-inch and 7-inch magnifications (R greater than 0.97 and SEE less than 0.33 mm for all modes). In 28 abnormal coronary angiograms analyzed at end diastole, stenosis and reference diameter correlations between the two systems were excellent (R = 0.90 and 0.96 and SEE = 0.43 and 0.33 mm for densitometric and geometric modes, respectively). Intraobserver and interobserver correlation was also excellent for both analysis modes. The new QCA system was able to perform analysis in approximately one third the time required by previously validated system and was much less expensive. We conclude that personal computer-based coronary analysis is an accurate, quick, and relatively inexpensive means for performing QCA that may help to make this technique feasible for nonresearch settings.

Constriction, Pathologic↗
PubMed1992

Estimating radon potential from an aerial radiometric survey.

A radon screening survey of 719 residences in Nova Scotia was performed using liquid scintillation charcoal canisters. The readings have been correlated with an aerial radiometric survey map of the 1.76-MeV gamma emission of 214Bi, which is plotted in terms of uranium parts per million equivalent. A good correlation exists, suggesting that this particular map could be used to indicate the potential for radon problems in particular geographic areas.

Air Pollutants, Radioactive↗
PubMed1990

Glucose metabolism and the channeling of glycolytic intermediates in permeabilized L-929 cells.

L-929 cells (mouse fibroblasts) permeabilized with dextran sulfate (DSP cells) carry out vigorous and linear rates of glycolysis when supplied with a suitable incubation medium. Glycolysis in DSP cells is pH dependent, being strongly inhibited at pH 6.5. Compared to their nonpermeabilized counterparts, DSP cells exhibit faster glycolytic rates, but tend to convert a smaller proportion of the glucose utilized to lactate. [14C]Glucose is converted to lactate by DSP cells without dilution from endogenous substrates. When exogenous 12C-labeled glycolytic intermediates (12C-I) are added to glycolyzing DSP cells the [14C]lactate produced from [14C]glucose is diluted to varying extents, depending on the intermediate. However, the extent of that dilution (reduced specific activity) is not that expected from the complete mixing of exogenous 12C-I with their corresponding 14C-labeled intermediates coming from [14C]-glucose. DSP cells also respire and convert glucose to CO2. The amount of 14CO2 produced from [14C]glucose is also reduced by addition of most 12C-I, an interesting exception being pyruvate, which had no measurable effect on 14CO2 production and caused only a modest stimulation of respiration in glycolyzing DSP cells. These results suggest that channeling, or some other form of coupling, takes place between the glycolytic production of pyruvate and its further oxidation. These observations confirm previously published data and add further support to the proposition that channeling of glycolytic intermediates occurs in DSP cells but is of the "leaky" type. Although abundant evidence in the literature indicates that various glycolytic enzymes associate with F-actin, as well as other elements of the cytomatrix, we observed no effect of cytochalasin D on lactate production even at very high concentrations of this compound. Our results are compared with those from other laboratories and discussed in the context of metabolic organization.

Animals↗
PubMed1990

Glycolysis compared in intact, permeabilized and sonicated L-929 cells.

The effects of incubation time and cell density on glycolytic rate were examined in suspensions of intact, permeabilized and sonicated L-929 cells. Sonicates exhibited strong dependence on cell density and a distinct lag in glycolytic rate, while intact cells showed no cell density dependence and linear glycolytic rates. Permeabilized cells exhibited linear glycolytic rates, but sometimes showed dependence on cell density. Rates of lactate production (nmol at 30 min/10(6) cells) were highest in sonicates and lowest in intact cells. These results are interpreted as support for the previously proposed hypothesis that enzymes of the glycolytic pathway are highly organized in intact L-929 cells.

Animals↗
PubMed1990

Effects of reduced cell volume and water content on glycolysis in L-929 cells.

Mouse L-929 cells were subjected to increasing concentrations of sorbitol, which remove cell water and reduce volume osmotically. The rate of lactate production from glucose was significantly higher in osmotically perturbed cells than in controls, both in monolayers and in suspensions. L cells can apparently use sorbitol as a glycolytic substrate; however, studies using other solutes (trehalose and sucrose) and permeabilized cells showed that the major effect of sorbitol on glycolysis in intact cells is mediated through a reduction in cell water content and volume. It is possible to explain some of these results by an increase in the chemical potentials of dissolved components of the glycolytic pathway caused by water loss; however, the relationship between water loss and glycolytic rate increase in not a simple linear one, suggesting that the situation is more complex than would result merely from increased concentrations of pathway components. Whatever the complete explanation might be, these studies show that glycolysis continues in an orderly fashion in cells that have lost about 85% of their original water content, suggesting that the operation of this pathway is not unduly sensitive to events taking place in the bulk aqueous phase.

Animals↗
PubMed1990

A comparative study of the nephrotoxicity of iohexol, iopamidol and ioxaglate in peripheral angiography.

Iohexol (Omnipaque 350) and iopamidol (Isovue 370) are nonionic monomers; ioxaglate (Hexabrix 320) is an ionic dimer. We compared the nephrotoxicity of these three media by a prospective double-blind evaluation in 500 patients who underwent peripheral angiography during a 6-month period. Serum creatinine levels were determined before injection of the contrast medium and 72 hours after in 478 patients. In 308 (64%) patients there was an average increase in the serum creatinine level of 18.1 mumol/L after injection of an average volume of 123 ml of contrast medium. A subset of 80 patients who had an elevated baseline creatinine level (more than 110 mumol/L) had an average increase in the serum creatinine level of 40.45 mumol/L. Of patients who had arterial injections, 182 (72%) had an increase in serum creatinine level (20.7 mumol/L), but of those who had peripheral venous injections, only 43 (45%) had an elevated creatinine level (9.2 mumol/L), and of those who had central venous injections, 83 (63.8%) had an elevated level (17.0 mumol/L). In most patients elevation of the serum creatinine level was not of clinical importance. High-risk patients with an elevated serum creatinine level were found to be most vulnerable to contrast nephrotoxicity. Although mean differences were not statistically significant, there were consistent trends which suggested that ioxaglate was the least nephrotoxic of the three agents studied.

Acute Kidney Injury↗
PubMed1989

Evidence for intermediate channelling in the glycolytic pathway of permeabilized L-929 cells.

L-929 cells permeabilized by dextran sulfate (DSP cells) carry out vigorous and linear rates of glycolysis when supplied with a suitable incubation medium. Unlabeled 3-phosphoglycerate (PGA) added to DSP cells reduces the specific activity of lactate coming from [14C]glucose but the extent of this reduction can not be accounted for on the basis of free diffusion of PGA coming from [14C]glucose. Studies on other glycolytic intermediates, although preliminary, yield similar results. PGA also inhibits the production of lactate from glucose; however, this effect, like that of the reduction of lactate specific activity, becomes apparent only at concentrations of PGA well in excess of those considered to be physiological. We conclude that channelling of PGA, and probably other intermediates, occurs but is of the "leaky" type.

Animals↗