Blood Lead Concentrations and Pregnancy Outcomes

In this study, the authors related blood lead concentrations to Apgar scores, birth weight, gestational age, small-for-gestational age, and hypertension in pregnancy (HIP)/toxemia. Data and blood were collected 4 times during pregnancy from 705 women, aged 12–34 yr. Blood lead concentrations, measured by atomic absorption spectrophotometry, were related to reproductive outcomes, abstracted from medical records. Average blood lead concentrations were 1.2 μg/dl (standard error = ± 0.03). Maternal blood lead concentrations were related significantly to HIP/toxemia—before and after adjusting for age, calcium intake, and race/ethnicity (p < .03). Longitudinal regression analyses revealed that blood lead concentrations in women with HIP/toxemia changed by 0.02 μg/dl for every 0.01 μg/dl change in women without HIP/toxemia. Maternal blood lead concentration and its change were not significantly associated with other reproductive outcomes. Low levels of maternal blood lead concentrations were significantly associated with HIP/toxemia.     

Joint influence of fat and lean body composition compartments on femoral bone mineral density in premenopausal women.

Body composition (fat and lean compartments) and bone mineral density were measured in 246 healthy premenopausal women, aged 20-40 years, residing in Tecumseh, Michigan. Body composition was measured using four-point bioelectrical impedance and values for fat and lean compartments categorized into tertiles. Additionally, each woman was classified into one of nine different cells based on her location within a 3 x 3 table which reflects the joint distribution of both fat and lean compartments. Bone mineral density of the proximal femur, including the femoral neck and trochanter, was measured using dual photon densitometry. The mean femoral neck bone mineral density values increased significantly and linearly for each tertile of muscle mass (0.90, 0.95, and 1.02 g/cm2, p less than 0.0002). Femoral bone mineral density increased significantly but not linearly as the fat compartment progressed from the lowest to the highest tertile (0.95, 0.93, and 0.99 g/cm2). Bone mineral density of the proximal femur was similar and significantly greater in the high muscle/low fat and high muscle/high fat body composition subgroups compared with bone mineral density in the seven other groups. However, women in the high muscle/low fat subgroup had substantially lower mean weight (67 vs. 91 kg, p less than 0.0001) and mean Quetelet index (22.1 vs. 33.7 kg/m2, p less than 0.0001) than women in the high muscle/high fat subgroup. Bone mineral density values were similar and significantly lower in the following body composition cells: low muscle/low fat, low muscle/medium fat, and low muscle/high fat. Similar findings were observed at the trochanteric site. Low muscle is a risk factor for low bone mineral density in young adult women while higher fat is protective only when associated with substantial muscle.     

Influence of local duplex stability and N6-methyladenine on uracil recognition by mismatch-specific uracil-DNA glycosylase (Mug)

To maintain genomic integrity, DNA repair enzymes continually remove damaged bases and lesions resulting from endogenous and exogenous processes. These repair enzymes must distinguish damaged bases from normal bases to prevent the inadvertent removal of normal bases, which would promote genomic instability. The mechanisms by which this high level of specificity is accomplished are as yet unresolved. One member of the uracil-DNA glycosylase family of repair enzymes, Escherichia coli mismatch-specific uracil-DNA glycosylase (Mug), is reported to distinguish U:G mispairs from U:A base pairs based upon specific contacts with the mispaired guanine after flipping the target uracil out of the duplex. However, recent studies suggest other mechanisms for base selection, including local duplex stability. In this study, we used the modified base N6-methyladenine to probe the effect of local helix perturbation on Mug recognition of uracil. N6-Methyladenine is found in E. coli as part of both the mismatch repair and restriction-modification systems. In its cis isomer, N6-methyladenine destabilizes hydrogen bonding by interfering with pseudo-Watson-Crick base pairing. It is observed that the selection of uracil by Mug is sequence dependent and that uracil residues in sequences of reduced thermostability are preferentially removed. The replacement of adenine by N6-methyladenine increases the frequency of removal of the uracil residue paired opposite the modified adenine. These results are in accord with suggestions that local helix stability is an important determinant of base recognition by some DNA repair enzymes and provide a potential strategy for identifying the sequence location of modified bases in DNA.     

Incidence and survival rates of children and young adults with osteogenic sarcoma

Gender-specific and race-specific incidence and survival rates of osteogenic sarcoma over a 14-year period are presented for persons aged 0 to 24 years from eight Surveillance, Epidemiology, and End Results (SEER) registries. They were no significant gender or racial differences in age at diagnosis. There was no significant gender difference in overall incidence. Although incidence rates were slightly higher in blacks compared with whites, the difference was not significant after controlling for multiple comparisons. Females (median, 74 months) survived longer than males (median, 29 months), although this difference weakened after controlling for stage. No racial differences in survival were observed. White females survived the longest (median, 94 months), followed by black females (median, 41 months), black males (median, 34 months), and white males (median, 29 months). This striking difference in survival should be explored more fully.     

Dopaminergic regulation of natriuretic response to acute volume expansion in dogs

Effects of carbidopa, a dopa (3,4-dihydroxyphenylamine) decarboxylase inhibitor, on the renal, haemodynamic and hormonal responses to acute volume expansion were examined in six healthy mongrel dogs which were infused intravenously with 0.9% sodium chloride solution (saline; 30 ml h-1 kg-1) over 2 h. Saline infusion studies were performed in the absence (control) and in the presence of carbidopa given by nasogastric tube in a dose of 1 mg/kg every 8 h beginning 24 h before the infusion. Saline infusion resulted in an increase in renal excretion of dopamine (3,4-dihydroxyphenylethylamine) and a decrease in renal excretion of noradrenaline. Carbidopa treatment decreased urinary sodium excretion and eliminated the increase in renal production of dopamine in response to saline infusion without affecting renal or haemodynamic response to acute vascular volume expansion with saline. Carbidopa treatment obliterated the suppression of aldosterone produced by saline infusion. Thus, dopamine appears to play a significant role in mediating both the natriuretic and aldosterone response to acute volume expansion.