Apparent coactivation due to interference of expression constructs with nuclear receptor expression

Transient cotransfection in COS-7 cells, a standard approach to demonstrate coactivation, was used to study the coactivation properties of NuRIP183, a new nuclear receptor interacting protein of 183 kDa, isolated by a yeast two-hybrid screening. Transfection with a NuRIP183 expression construct strongly increased the ligand-dependent response of reporter constructs for several nuclear receptors when compared to transfection with the empty expression vector. A more detailed study, however, revealed major changes in the expression level of the nuclear receptors in cotransfection experiments, indicating that the observed changes in receptor activity were not due to coactivation but to differences in receptor concentration caused by interference from the cotransfected expression constructs with the expression of the receptor. Such interference, which is inversely related to the length of the insert, was observed, not only in COS-7 cells but also in CV-1 and MCF-7 cells, using different transfection techniques (FuGENE-6 and calcium phosphate) and different expression vectors (pSG5, pcDNA1.1 and pIRESneo). These data cast some doubt on coactivation of nuclear receptors based on similar cotransfection experiments without measurement of receptor concentration. Moreover, it is recommended to limit the amounts of (co)transfected expression plasmid and to avoid the use of empty expression plasmid as a control. Finally, one should be aware of similar misleading results in other experimental set-ups based on cotransfection.     

Relation between cardiovascular risk factors at adult age,and physical activity during youth and adulthood: the Leuven Longitudinal Study on Lifestyle,Fitness and Health

This study investigated the relationship between sports participation/physical activity during youth (13 - 18 years of age) and adulthood (30 - 40 years of age), and cardiovascular risk factors (body fat and fat distribution, blood pressure, lipoprotein levels and cardiorespiratory fitness) at 40 years of age. Subjects were 166 Flemish males from "The Leuven Longitudinal Study on Lifestyle, Fitness and Health". Physical activity was assessed by means of a sports participation inventory and the Tecumseh community Health Study Questionnaire. In addition to correlation and multiple stepwise regression analyses, different groups (at risk, not at risk) were contrasted on sports participation/physical activity parameters using ANOVA. Long-term exposure during adulthood to daily physical activity was slightly related to a low/high risk profile for waist circumference, percent body fatness, triglycerides and peak VO(2). Sports participation during adolescence was not related to levels of cardiovascular risk factors at 40 years of age.     

Adolescent growth spurts in female gymnasts

OBJECTIVES: Three questions were addressed: (1) Do female gymnasts have adolescent growth spurts in height, sitting height, and leg length? (2) Are the sequence and magnitude of spurts comparable with female adolescent non-athletes? (3) How do the data compare with other female gymnasts and with short girls? STUDY DESIGN: Height and sitting height were measured annually on 15 Belgian gymnasts from 8.7 +/- 1.5 to 15.5 +/- 1.5 years. The gymnasts trained, on average, approximately 15 h/wk. Leg length was estimated as height minus sitting height. The Preece-Baines Model I was fitted to individual growth records to estimate ages at peak velocity and peak velocities for the three dimensions. Age at menarche and skeletal age were also assessed. RESULTS: Gymnasts have clearly defined adolescent spurts in height, estimated leg length, and sitting height that occur approximately 1 year later and are slightly less intense than in nonathletic adolescent girls. Age at menarche and skeletal age are consistent with later somatic maturation. The pattern of adolescent growth and maturation is similar to that of other gymnasts, short normal late-maturing girls, and late-maturing girls with short parents. CONCLUSIONS: The results emphasize a primary role for constitutional factors in the selection process of female gymnasts at relatively young ages.     

The effects of load on systolic mitral annular velocity by tissue Doppler imaging

Tissue Doppler Imaging (TDI) provides information on systolic function through its systolic mitral annulus velocity wave (Sm), reflecting the peak velocity of shortening of the myocardial fibers oriented in the longitudinal direction. In this study, we evaluated the effect of load changes on Sm. Forty-two cardiac surgical patients with left ventricular ejection fraction >60% were consecutively evaluated. In 24 patients, load was changed with an IV bolus of phenylephrine (50-100 microg) or nitroglycerine (300-500 microg); in 18 patients, preload was changed with a rapid infusion of 500 mL of a gelatin solution. The sample volume of TDI was placed at the lateral side of the mitral annulus in the mid-esophageal 4-chamber view. Changing loading conditions with phenylephrine or nitroglycerine had no effect on Sm; the increase of preload in 18 patients resulted in a statistically significant increase of Sm (baseline, 8.4 +/- 2.6 cm/s; after increase of preload, 9.6 +/- 2.5 cm/s; P = 0.001). We conclude that Sm is dependent on changes in preload obtained by volume loading and cannot be recommended as an index of ventricular contractile performance in critically ill patients where significant changes in ventricular filling occur.