Effect of calcium chloride on the conformation of proteins. Thermodynamic studies of some model compounds

Partial molar heat capacities (CP2 degrees) and volumes (V2 degrees) for some amino acids and peptides were measured in 1 M aqueous calcium chloride solutions at 298.15 degrees K using a Picker flow microcalorimeter and an oscillating-tube digital density meter. Using the data for these amino acids and peptides in water, the corresponding partial molar heat capacities of transfer (CP2,tr degree) and volumes (V2,tr degree) from water to 1 M aqueous calcium chloride were deduced. These thermodynamic parameters are significantly positive, indicating that strong interactions occur between the ions of calcium chloride and the charged centres of these amino acids and peptides. A comparison has been made with a similar transfer of these compounds to sodium chloride solutions. The thermodynamic parameters of the transfer of peptide group (-CONH) are much more positive in calcium chloride than in sodium chloride solutions. The implication of this result for the ability of calcium chloride to act as a stronger destabilizer of protein conformation is discussed.     

Additive Interactions of Maternal Prepregnancy BMI and Breast‐feeding on Childhood Overweight

Objective: To examine the interactions of maternal prepregnancy BMI and breast‐feeding on the risk of overweight among children 2 to 14 years of age. Research Methods and Procedures: The 1996 National Longitudinal Survey of Youth, Child and Young Adult data in the United States were analyzed (n = 2636). The weighted sample represented 51.3% boys, 78.0% whites, 15.0% blacks, and 7.0% Hispanics. Childhood overweight was defined as BMI ≥95th percentile for age and sex. Maternal prepregnancy obesity was determined as BMI ≥30 kg/m². The duration of breast‐feeding was measured as the weeks of age from birth when breast‐feeding ended. Results: After adjusting for potential confounders, children whose mothers were obese before pregnancy were at a greater risk of becoming overweight [adjusted odds ratio (OR), 4.1; 95% confidence interval (CI), 2.6, 6.4] than children whose mothers had normal BMI (<25 kg/m²; p < 0.001 for linear trend). Breast‐feeding for ≥4 months was associated with a lower risk of childhood overweight (OR, 0.6; 95% CI, 0.4, 1.0; p = 0.06 for linear trend). The additive interaction between maternal prepregnancy obesity and lack of breast‐feeding was detected (p < 0.05), such that children whose mothers were obese and who were never breast‐fed had the greatest risk of becoming overweight (OR, 6.1; 95% CI, 2.9, 13.1). Discussion: The combination of maternal prepregnancy obesity and lack of breast‐feeding may be associated with a greater risk of childhood overweight. Special attention may be needed for children with obese mothers and lack of breast‐feeding in developing childhood obesity intervention programs.     

Development of a Culturally Relevant Body Image Instrument among Urban African Americans

Objective: To validate a culturally relevant body image instrument among urban African Americans through three distinct studies. Research Methods and Procedures: In Study 1, 38 medical practitioners performed content validity tests on the instrument. In Study 2, three research staff rated the body image of 283 African‐American public housing residents (75% women, mean age = 44 years), with the residents completing body image, BMI, and percentage body fat measures. In Study 3, 35 African Americans (57% men, mean age = 42) completed body image measures and evaluated their cultural relevance. Results: In Study 1, 97% to 100% of practitioners sorted the jumbled figures into the correct ascending order. The correlation between the body image figures and the practitioners’ weight classifications of the figures was high (r = 0.91). In Study 2, observers arrived at similar ratings of body size with excellent consistency (α = 0.95). Ratings of body image were strongly correlated with participant BMI (r = 0.89 to 0.93 across observers and 0.81 for all participants) and percentage of body fat (r = 0.77 to 0.89 across observers and 0.76 for all participants). In Study 3, body image ratings with the new scale were positively correlated with other validated figural scales. The majority of participants reported that figures in the new body image scale looked most like themselves and other African Americans and were easiest to identify themselves with. Discussion: The instrument displayed strong psychometric performance and cultural relevance, suggesting that the scale is a promising tool for examining body image and obesity among African Americans.     

Heat capacity of folding of proteins corrected for disulfide cross-links

The heat capacities (DeltaC(p,f)) for the temperature-induced folding of proteins: barnase, lysozyme T4, papain, trypsin, ribonuclease T1, chymotrypsin, lysozyme and ribonuclease A have been calculated from the change in solvent accessible surface area between the native state and extended polypeptide chain. To visualize the effect of disulfide cross-links on molar heat capacity, loops of varying number of alanine residues and extended alanine chains with terminal cystein are modeled. The difference in DeltaC(p) values between the extended state and the loop conformation of proteins is linearly related to the number of residues in the loop. Corrections to the heat capacity of folding (DeltaC(p,f)) are applied for proteins with cross-links based on this observation. There is good correlation between corrected values of DeltaC(p,f) and experimental values.     

Effect of estradiol on estrogen receptor expression in rat uterine cell types

In rodent uterus, both up- and down-regulation of estrogen receptor alpha (ERalpha) messenger ribonucleic acid (mRNA) and protein levels by estradiol has been demonstrated; however, it is not known which of the uterine compartments (endometrial epithelium, stroma, myometrium) respond to estradiol with autoregulation of ERalpha. The purpose of the present study was to investigate and compare the kinetics and cell type-specific effects of estradiol on uterine ERalpha expression in immature and adult rats. Ovariectomized female rats were injected s.c. with sesame oil or estradiol-17beta. Uteri were collected and analyzed for changes in ERalpha mRNA using RNase protection assays (RPA) and in situ hybridization using radiolabeled probes specific for ERalpha. Immunohistochemical analysis was performed with a polyclonal antibody specific to ERalpha. Expression of ERalpha in the uterine epithelial cells decreased at 3 and 6 h after estradiol administration to immature and adult rats, respectively. At 24 h, ERalpha mRNA levels in the immature and mature rat uterus were higher than pretreatment levels but returned to baseline by 72 h. Pretreatment with cycloheximide did not block the 3-h repressive effect of estradiol, suggesting that the estradiol-induced decrease in ERalpha mRNA occurs independent of new protein synthesis. A decrease in ERalpha mRNA and protein was also observed in uterine epithelia at 3 and 6 h after an estradiol injection to immature and adult rats, and intensity of both the in situ hybridization signal and the immunostaining in the epithelium increased at 24 and 72 h. However, the periluminal stromal cells in the adult uterus and the majority of stromal cells of the immature uterus appeared to have increased ERalpha expression. The results indicate that down-regulation of ERalpha in the epithelia and up-regulation of stromal ERalpha play a role in early events associated with estradiol-induced cell proliferation of the uterine epithelia.     

Inhibited aortic aneurysm formation in BLT1-deficient mice

Leukotriene B(4) is a proinflammatory lipid mediator generated by the enzymes 5-lipoxygenase and leukotriene A(4) hydrolase. Leukotriene B(4) signals primarily through its high-affinity G protein-coupled receptor, BLT1, which is highly expressed on specific leukocyte subsets. Recent genetic studies in humans as well as knockout studies in mice have implicated the leukotriene synthesis pathway in several vascular pathologies. In this study, we tested the hypothesis that BLT1 is necessary for abdominal aortic aneurysm (AAA) formation, a major complication of atherosclerotic vascular disease. Chow-fed Apoe(-/-) and Apoe(-/-)/Blt1(-/-) mice were treated with a 4-wk infusion of angiotensin II (1000 ng/min/kg) beginning at 20 wk of age, in a well-established murine AAA model. We found a reduced incidence of AAA formation as well as concordant reductions in the maximum suprarenal/infrarenal diameter and total suprarenal/infrarenal area in the angiotensin II-treated Apoe(-/-)/Blt1(-/-) mice as compared with the Apoe(-/-) controls. Diminished AAA formation in BLT1-deficient mice was associated with significant reductions in mononuclear cell chemoattractants and leukocyte accumulation in the vessel wall, as well as striking reductions in the production of matrix metalloproteinases-2 and -9. Thus, we have shown that BLT1 contributes to the frequency and size of abdominal aortic aneurysms in mice and that BLT1 deletion in turn inhibits proinflammatory circuits and enzymes that modulate vessel wall integrity. These findings extend the role of BLT1 to a critical complication of vascular disease and underscore its potential as a target for intervention in modulating multiple pathologies related to atherosclerosis.     

Developmental trajectories of overweight during childhood: role of early life factors

Objective: Our goal was to identify developmental trajectories of overweight in children and to assess early life influences on these trajectories. Research Methods and Procedures: Participants consisted of 1739 white, black, and Hispanic children who were younger than 2 years at the first survey and were followed up to 12 years of age. Repeated measures of overweight, defined as BMI ≥95th percentile, were used to identify overweight trajectories with a latent growth mixture modeling approach. Results: Three distinct overweight trajectories were identified: 1) early onset overweight (10.9%), 2) late onset overweight (5.2%), and 3) never overweight (83.9%). After adjustment for multiple potential risk factors, male gender [odds ratio (OR), 1.5; 95% confidence interval (CI), 1.0 to 2.2], black ethnicity (OR, 1.7; 95% CI, 1.1 to 2.6), maternal 25 ≤ BMI <30 kg/m² (OR, 2.2; 95% CI, 1.3 to 3.7) or ≥30 kg/m² (OR, 5.1; 95% CI, 2.9 to 9.1), maternal weight gain during pregnancy ≥20.43 kg (OR, 1.7; 95% CI, 1.0 to 2.9), and birth weight ≥4000 g (OR, 2.0; 95% CI, 1.2 to 3.4) were associated with an increased risk of early onset overweight. These risk factors, except maternal weight gain, exerted similar effects on late onset overweight. In addition, maternal smoking (OR, 1.6; 95% CI, 0.8 to 3.1) and birth order ≥3 (OR, 2.3; 95% CI, 1.0 to 5.2) were associated with an increased risk of late onset overweight only. Breastfeeding ≥4 months was associated with a decreased risk of both early (OR, 0.7; 95% CI, 0.3 to 1.3) and late onset overweight (OR, 0.7; 95% CI, 0.3 to 1.7). Discussion: Two trajectories of overweight and one never overweight group were identified. Early life predictors may have a significant influence on the developmental trajectories of overweight in children.