College athletes' perceptions of social support provided by their coach before injury and after it.

AIM: The aim of this study was to evaluate athletes' perceptions of social support provided by their coach before injury and after it. METHODS: Participants were 29 high school athletes with minor to severe injuries, who were forced to sit out practice or competition for at least 3 days due to their injury. Male (n=17) and female (n=12) team sport and individual sport athletes ranged in age from 18 to 25 years (mean: 21.18; standard deviation: 1.26). Eight subjects (28%) had major injuries, 12 (41%) had moderate injuries, and 9 (29%) had minor injuries. Twenty-nine high school athletes completed a modified version of the Social Support Survey. Data were collected on who provides each of 6 types of social support, how satisfied the high school athletes are with the amount and type of support they received, and the perceived effect of support on their well-being. RESULTS: With two exceptions, results indicated no differences between preinjury and postinjury satisfaction with the support provided by coaches. The exceptions were for task challenge support and emotional challenge support. Results indicated no differences in the perceived importance to their well-being of support provided by coaches before injury and after it. The exceptions were for listening support and emotional support. CONCLUSION: These findings confirm the possible positive effects of coaches' listening and emotional support on injured high school athletes' recovery efforts.

Low job control and myocardial infarction risk in the occupational categories of Kaunas men, Lithuania.

STUDY OBJECTIVE: To determine the association between adverse psychosocial characteristics at work and risk of first myocardial infarction in the occupational categories of Kaunas men, Lithuania. DESIGN: The analysis was based upon a case-control study among full time working men in the general population of Kaunas. OUTCOME MEASURE: First non-fatal myocardial infarction diagnosed in 2001-2002. The Swedish version of the demand-control questionnaire was used to examine the effect of job control and demands. SETTING: Kaunas, the second largest city in Lithuania, a former socialist country in a transition market economy. PARTICIPANTS: Cases were 203 men 25-64 years of age with a first non-fatal myocardial infarction and controls were 287 men group randomly selected from the study base. MAIN RESULTS: Low job control had a significant effect on myocardial infarction risk in the general 25-64 year old Kaunas male population (OR = 2.68; 95% CI 1.68 to 4.28) after adjustment for age and socioeconomic status. Low job control was a risk factor in the occupational categories of the increased myocardial infarction risk (1st occupational category--legislators, senior officials and managers and the 8th--plant and machine operators and assemblers; OR = 2.78; 95% CI 1.31 to 5.93 and 2.72; 95% CI 1.56 to 4.89, respectively, after adjustment for age and socioeconomic status). Though the adjusted odds ratio estimates were significantly high for the rest of the occupational categories (2nd--professionals, 3rd--technicians and associate professionals, and 7th--craft and related trades workers). CONCLUSIONS: The association between low job control and first myocardial infarction risk was significant for all occupational categories of Kaunas men.

Association between secondary flow in models of the aorto-celiac junction and subendothelial macrophages in the normal rabbit.

In order to examine the association between arterial fluid dynamics and the distribution of subendothelial macrophages in the normal rabbit aorta, steady and pulsatile particle flow visualization was performed in a geometrically realistic model of the rabbit aorto-celiac junction region. Over a range of aorto-celiac steady flow ratios, particle pathlines along the upstream lateral aortic walls curved to enter the celiac orifice, while two asymmetric regions of reversing spiral secondary flow originated along the downstream lateral portions of the orifice flow divider. These regions increased in size as either the Reynolds number or flow into the celiac artery increased. In pulsatile flow studies, particles along the lateral aortic walls near the celiac orifice began to spiral into the branch during peak systole. During systolic deceleration, the size of this spiral flow region increased as particles reversed direction to enter the celiac orifice. This contrasted with flow patterns directly upstream and downstream of the orifice, which remained unidirectional throughout this period even along the distal lip of the orifice. The highest frequency of subendothelial white blood cells in the normal rabbit aorta was associated with regions where secondary flow patterns occurred, and where the orientation of endothelial cell nuclei deviated from the major direction of aortic flow. Secondary flow patterns may aid the accumulation of monocytes and macrophages about the lateral regions of the celiac artery flow divider by transporting monocytes to the walls, allowing them time to attach to the endothelial cells, or by stimulating the endothelial cells to express leukocyte adhesion molecules. These same regions are associated with increased endothelial permeability to low density lipoprotein and, under hypercholesterolemic conditions, lesion origination.

Effect of orifice-area reduction on flow characteristics during injection through spinal needles.

A reduction in hole size for certain side-port spinal needles has been advocated in recent reports. While the influence of orifice-area reduction on the aspiration capability of the needle has been studied, the influence on the anaesthetic delivery properties is relatively unknown. As a first step in understanding the effects of hole-size reduction on anaesthetic distribution within the subarachnoid space, we studied flows emanating from isolated needles using computer simulations. Following validation of the numerical model using experimental particle visualisation, trajectories of anaesthetic particles injected through 25 G Whitacre needles of various orifice areas were computed and used to determine the orientation and rate of spread of the anaesthetic jet exiting the needle. Two factors impacting the concentration distribution were observed: the rate of spread of the anaesthetic jet increases markedly with decreasing orifice area and the jet alignment shifts toward perpendicular to the needle axis.

Plasma hemoglobin measurement techniques for the in vitro evaluation of blood damage caused by medical devices.

A sensitive measure of the in vitro blood damage potential of a medical device is the rate at which hemoglobin is released into the plasma from red blood cells flowing through the device. Presently there is no one widely accepted method for measuring the plasma hemoglobin concentration. Nine currently used assays, classified as either direct optical or added chemical techniques, were evaluated for accuracy, reproducibility, sensitivity, interference effects, and ease of use by adding hemoglobin (1-200 mg/dl) to saline, lipid, and bilirubin solutions and to normal cow plasma. Most of the assays displayed good linearity, accuracy, and reproducibility down to 1 mg/dl when interferents were absent. However, representative of the effects caused by interferents, the endogenous hemoglobin concentration of a typical cow plasma sample measured by the 9 techniques ranged from -2 to 39 mg/dl. Although used by fewer organizations, some of the direct optical spectrophotometric methods (e.g., the Cripps and Harboe baseline correction methods) are safer, easier, and more precise and accurate than the chemical addition methods used to measure plasma hemoglobin concentration from in vitro blood damage testing of medical devices.

The distribution of intimal white blood cells in the normal rabbit aorta.

Macrophages play an important role in atherogenesis and have been reported within the intima at lesion-prone sites in normocholesterolemic animals as well as infants and children. The objective of this study was to determine the spatial distribution of intimal white blood cells (WBC) in the normal rabbit aorta and the association of intimal WBC with replicating endothelial cells and sites of increased 125I-LDL permeability. Intimal WBC and macrophages were identified en face on whole aortic tissue and on Häutchen preparations based on their morphology, ingestion of exogenous horseradish peroxidase, non-specific esterase activity, and labeling with a monoclonal antibody for rabbit macrophages (RAM11). WBC were primarily located in the lesion-prone flow divider regions of the large abdominal branch arteries. Using [3H]thymidine autoradiography to determine cell proliferation, 4.4% of the WBC and 0.12% of the endothelial cells were labeled on the Häutchen preparations. The distribution of replicating endothelial cells was not localized to the arterial orifices and was not correlated with the distribution of intimal WBC. Intimal WBC were, however, spatially correlated with the distribution of 125I-LDL permeable sites about the celiac artery orifice and were directly associated with 31% of the LDL permeable spots. Moreover, mitotic endothelial cells accounted for only 8% of the total number of LDL permeable sites. The presence of intimal WBC at lesion-prone sites in the normocholesterolemic rabbit suggests that these cells may be important in the initiation of atherosclerotic lesions.

Characterization of sites with elevated LDL permeability at intercostal, celiac, and iliac branches of the normal rabbit aorta.

En face autoradiography of the endothelium was used to quantify the distribution, area, and permeability of sites with enhanced permeability to 125I-low-density lipoprotein (125I-LDL) around the intercostal and celiac arteries and at the iliac bifurcation of normal rabbit aortas. The density of such sites was highest in the upper thoracic aorta and around the celiac and superior mesenteric branches and was lowest in the lower abdominal aorta. Permeable sites occurred more frequently distal to the intercostal branch orifices and both lateral and distal to the orifice at the celiac branch. At the intercostal branch orifices, these sites were larger, with a lower permeability and higher frequency than those away from the branch. At the celiac flow divider, sites of elevated autoradiographic grain density were more permeable and larger than at other locations in the abdominal aorta. Mean regional permeabilities were obtained by weighted area averages of low- and high-permeability sites. Mean regional permeabilities around the intercostal branches were 1.5 times higher than values away from the intercostal branches. Within 0.25 and 1 mm away from the celiac flow divider, mean regional permeability was 3.1 and 1.3 times higher, respectively, than those away from the flow divider. Few sites of elevated permeability were found distal to the aortoiliac bifurcation, and the permeabilities at the medial and lateral walls of the iliac arteries were not different. Mitotic cells were associated with 13 +/- 8% of all sites with elevated permeability to 125I-LDL. The frequency of mitotic endothelial cells was not increased at branch sites, suggesting that mechanisms other than cell replication were responsible for increased LDL permeability in the rabbit. These results suggest that the permeability and frequency of occurrence of sites with elevated permeability around the celiac and intercostal branches may influence the distribution and severity of early lesions in rabbits fed a hypercholesterolemic diet.

Measurement of endothelial permeability to 125I-low density lipoproteins in rabbit arteries by use of en face preparations.

A procedure of en face quantitative autoradiography of the endothelium (Hautchen preparations) was developed to examine regional variations in 125I-low density lipoprotein (125I-LDL) permeability in the arterial wall in vivo. Endothelial preparations from fixed arterial tissue and calibration standards consisting of known concentrations of 125I-albumin were dipped in nuclear emulsion, exposed for 1-3 months, developed, and stained with hematoxylin. Digital image analysis was used to analyze dark-field images of autoradiographs. Background grain densities on cold endothelial preparations were 30-100% higher than on glass, but the variability in grain densities on the two different surfaces was similar. Regression slopes of grain density versus concentration for calibration standards were the same for sections placed on cold tissue or glass. For 1-5-microns-thick calibration standards of the same concentration, the grain density was proportional to the total amount of radioactivity per unit area. The results indicated that errors arising from nonuniformities in preparation thickness were minimal, and permeabilities and intimal concentrations could be determined. Rabbits were killed 10 minutes after injection of 125I-LDL, and endothelial preparations were made. For regions of uniformly low grain density in the rabbit aorta, the 125I-LDL permeability was 1.9 +/- 0.8 x 10(-8) cm/sec, and the effective diffusion coefficient was 5.4 +/- 3.1 x 10(-10) cm2/sec. Errors in the estimated permeability arising from nonuniformities in tissue thickness were the same as the reported experimental variability. Analysis of elevated regions of permeability suggested that 125I-LDL was binding to the extracellular matrix. Approximately 25% of the sites of elevated grain density were associated with mitotic endothelial cells, and such regions had higher permeabilities than sites associated with nonmitotic cells. Around intercostal arteries, sites of highest permeability were distal and lateral to the vessels and occurred where lesions first develop in hypercholesterolemic rabbits.