Analysis of swimming performance from physical, physiological, and biomechanical parameters in young swimmers

The purpose of this study was to examine the influence of the energy cost of swimming, body composition, and technical parameters on swimming performance in young swimmers. Twenty-nine swimmers, 15 prepubertal (11.9 +/- 0.3 years; Tanner Stages 1-2) and 14 pubertal (14.3 +/- 1.4 years; Tanner Stages 3-4) boys participated in the study. The energy cost of swimming (Cs) and stroking parameters were assessed over maximal 400-m front-crawl swimming in a 25-m swimming pool. The backward extrapolation technique was used to evaluate peak oxygen consumption (VO2peak). A stroke index (SI; m2 . s(-1) . cycles(-1)) was calculated by multiplying the swimming speed by the stroke length. VO2peak results were compared with VO2peak test in the laboratory (bicycle, 2.86 +/- 0.74 L/min, vs. in water, 2.53 +/- 0.50 L/min; R2 = .713; p = .0001). Stepwise-regression analyses revealed that SI (R2 = .898), in-water VO2peak (R2 = .358), and arm span (R2 = .454) were the best predictors of swimming performance. The backward-extrapolation method could be used to assess VO2peak in young swimmers. SI, arm span, and VO2peak appear to be the major determinants of front-crawl swimming performance in young swimmers.     

Re-irradiation of head and neck carcinoma

To determine the efficacy of re-irradiation of patients with head and neck carcinoma we reviewed the pertinent literature. Depending on the location and extent of the tumor, re-irradiation may be accomplished with external beam radiotherapy (RT), brachytherapy, intraoperative RT, and/or radiosurgery. The likelihood of cure is impacted by the interval between the initial course of RT and re-irradiation, whether the carcinoma is a recurrence or a second primary tumor, initial T-stage, and recurrent T-stage (rT-stage), whether the gross disease is isolated or local-regional, and histology. Patients with T1-T2 N0 second primary tumors have a relatively high likelihood of cure, whereas those with recurrent T3-T4 cancers, a short disease-free interval, and/or associated with a regional recurrence have a very low probability of cure. The likelihood of severe late complications is relatively high and is related to prior RT dose, primary site, retreatment RT dose, treatment volume, and technique. Previously irradiated patients with T1-T2 N0 carcinomas who are not surgical candidates may benefit from re-irradiation, albeit with an elevated risk of late complications. Those with advanced recurrences are unlikely to benefit from re-irradiation and should be considered for either a prospective clinical trial or for palliative chemotherapy or supportive care.     

A non-docking intraoperative electron beam applicator system

A non-docking intraoperative radiation therapy electron beam applicator system for a linear accelerator has been designed to minimize the mechanical, electrical, and tumor visualization problems associated with a docking system. A number of technical innovations have been used in the design of this system. These include: (a) a new intraoperative radiation therapy cone design that gives a better dose uniformity in the treatment volume at all depths; (b) a collimation system which reduces the leakage radiation dose to tissues outside the intraoperative radiation therapy cone; (c) a non-docking system with a translational accuracy of 2 mm and a rotational accuracy of 0.5 degrees; and (d) a rigid clamping system for the cones. A comprehensive set of dosimetric characteristics of the intraoperative radiation therapy applicator system is presented.     

Multivariate assessment of traditional risk factors for chronic lung disease in very low birth weight neonates. The Newborn Lung Project

All neonates (n = 581) with birth weights less than 1501 gm admitted to seven neonatal intensive care units in Wisconsin and Iowa were candidates for a study aimed at the multivariate assessment of risk factors for chronic lung disease while controlling for baseline severity of respiratory disease. Data from 361 neonates were analyzed for all risk factors except fluids; only neonates weighing less than 1200 gm were included (n = 220). Information on traditional risk factors for chronic lung disease was abstracted. A total of 110 (30%) of the analyzed neonates were oxygen dependent on day 30 of life. The following baseline factors were associated with increased risk of oxygen dependence in a joint multivariate model: lower birth weight (odds ratio 1.4/100 gm), higher baseline severity score (odds ratio 2.7/doubling at 32 weeks gestational age), lower gestational age (odds ratio 2.4/week at severity 0), Apgar score at 1 minute (odds ratio 1.6/2 points), male gender (odds ratio 1.9), and nonblack race (odds ratio 2.2). After adjustment for all baseline factors, patent ductus arteriosus, ventilator pressure at 96 hours, oxygen at 96 hours, and fluid intake were associated with oxygen dependence. Neonates with a low baseline severity score who remained oxygen dependent had a higher intake of fluid relative to output, whereas neonates with a higher baseline severity score had higher fluid intake and output. Lack of weight loss was associated with increased severity but not with oxygen dependence. The results of this study generally confirm the significance of previously reported risk factors for chronic lung disease in a multivariate setting but show that risk factors may not have the same impact in neonates with different baseline severity.     

Causes, Problems and Benefits of Different Between and Within Effects in the Analysis of Clustered Data

In analyzing longitudinal (panel), multicenter or otherwise clustered data, one often discovers that between and within individual or cluster regression coefficients are not equal. Clearly, this creates difficulties for interpretation and casts doubt on any causal interpretation of the coefficients. To help interpretation, it is useful to note that several types of model misspecification leading to this phenomenon can be reformulated as problems of omitted covariates. We consider models where the relationship between the outcome and the covariates is known, as long as all covariates are correctly measured and included. However, when there are unknown confounders, selection bias or measurement error, this is structurally equivalent to covariates being omitted. We first derive the correct form of the mean structure conditionally on the observed covariates, and then examine the consequences of fitting models which do not take into account the possibility of omitted covariates. We give examples of constraints, which allow estimation of the original parameters of interest. The models are used to help interpret analyses of data from the Asset and Health Dynamics of the Oldest Old (AHEAD), a panel survey of individuals age 70 and above.     

Inhibition of phospholipase D by lysophosphatidylethanolamine, a lipid-derived senescence retardant

Phospholipid signaling mediated by lipid-derived second messengers or biologically active lipids is still new and is not well established in plants. We recently have found that lysophosphatidylethanolamine (LPE), a naturally occurring lipid, retards senescence of leaves, flowers, and postharvest fruits. Phospholipase D (PLD) has been suggested as a key enzyme in mediating the degradation of membrane phospholipids during the early stages of plant senescence. Here we report that LPE inhibited the activity of partially purified cabbage PLD in a cell-free system in a highly specific manner. Inhibition of PLD by LPE was dose-dependent and increased with the length and unsaturation of the LPE acyl chain whereas individual molecular components of LPE such as ethanolamine and free fatty acid had no effect on PLD activity. Enzyme-kinetic analysis suggested noncompetitive inhibition of PLD by LPE. In comparison, the related lysophospholipids such as lysophosphatidylcholine, lysophosphatidylglycerol, and lysophosphotidylserine had no significant effect on PLD activity whereas PLD was stimulated by lysophosphatidic acid and inhibited by lysophosphatidylinositol. Membrane-associated and soluble PLD, extracted from cabbage and castor bean leaf tissues, also was inhibited by LPE. Consistent with acyl-specific inhibition of PLD by LPE, senescence of cranberry fruits as measured by ethylene production was more effectively inhibited according to the increasing acyl chain length and unsaturation of LPE. There are no known specific inhibitors of PLD in plants and animals. We demonstrate specific inhibitory regulation of PLD by a lysophospholipid.     

Multiple imputation of cognitive performance as a repeatedly measured outcome

Longitudinal studies of cognitive performance are sensitive to dropout, as participants experiencing cognitive deficits are less likely to attend study visits, which may bias estimated associations between exposures of interest and cognitive decline. Multiple imputation is a powerful tool for handling missing data, however its use for missing cognitive outcome measures in longitudinal analyses remains limited. We use multiple imputation by chained equations (MICE) to impute cognitive performance scores of participants who did not attend the 2011–2013 exam of the Atherosclerosis Risk in Communities Study. We examined the validity of imputed scores using observed and simulated data under varying assumptions. We examined differences in the estimated association between diabetes at baseline and 20-year cognitive decline with and without imputed values. Lastly, we discuss how different analytic methods (mixed models and models fit using generalized estimate equations) and choice of for whom to impute result in different estimands. Validation using observed data showed MICE produced unbiased imputations. Simulations showed a substantial reduction in the bias of the 20-year association between diabetes and cognitive decline comparing MICE (3–4 % bias) to analyses of available data only (16–23 % bias) in a construct where missingness was strongly informative but realistic. Associations between diabetes and 20-year cognitive decline were substantially stronger with MICE than in available-case analyses. Our study suggests when informative data are available for non-examined participants, MICE can be an effective tool for imputing cognitive performance and improving assessment of cognitive decline, though careful thought should be given to target imputation population and analytic model chosen, as they may yield different estimands.     

Short term high density systemic therapy for metastatic breast cancer

Summary Twenty-three patients with metastatic breast carcinoma were induced with a complex systemic therapy regimen in an attempt to ascertain if a complete remission rate >50% could be obtained with intensive drug exposure. The durability of the remissions was observed by discontinuing therapy after 3 cycles in complete remission or after 6 cycles of treatment, whichever was longer. In 13 patients consolidation radiation therapy to the pre-treatment sites of disease was administered after discontinuing systemic therapy. Each 28 day cycle of the drug regimen consisted of pulses of adriamycin, vincristine, dibromodulcitol, prednisone, methotrexate with leukovorin rescue, hexamethylmelamine, bleomycin (discontinued after entry #17), fluoxymesterone, and tamoxifen. Eighteen of the 23 patients achieved complete remissions (78%) and 3 had partial remissions. The median times to treatment failure and survival were, respectively, 12.3 and 19.4 mos. The times for complete remission patients were, respectively, 13.5 and 23.9 mos. Consolidation radiotherapy at 40 Gy to drug induced pre-study sites of complete remission was associated with first relapses at prestudy sites in 5/30 (17%) instances, compared to 21/35 (60%) in sites not receiving radiotherapy. Side-effects were commensurate with the intensity of the treatment program and are detailed in the text. Although the achievement of a high complete remission rate is promising, the failure to extend their duration beyond that of historical data suggests that additional conceptual and therapeutic approaches need to be explored.Supported in part by NIH Grants PO1-CA 20432 and P30-CA 14520 awarded to the Wisconsin Clinical Cancer Center.This data was presented in part at the American Society of Clinical Oncology Meeting in 1981.     

Reliability and validity of PROMIS® pediatric family relationships short form in children 8–17 years of age with chronic disease

Quality of Life Research - Families play a key role in managing pediatric chronic illness. The PROMIS® pediatric family relationships measure was developed primarily within the general...