Sources of variability in birth defects prevalence rates.

BACKGROUND: The characteristics and methodologies of state-based birth defect surveillance systems might influence reported prevalence rates, making comparisons among states difficult. Standardizing methods to minimize variability beyond true differences in prevalence will aid national surveillance efforts and birth defects prevention programs. METHODS: Using data provided in the January 2000 Congenital Malformations Surveillance Report from the National Birth Defects Prevention Network, we characterized the surveillance methodologies among all sites. We then identified prevalence rates that are highly varied among systems that use each of our specified methodologies. We also examined the standards used by other collective health registries that exist across geographical boundaries. RESULTS: Large differences in prevalence rates across case ascertainment methods (active, passive, or combination of both) were observed for some conditions, but not for others. We identified additional factors which may influence prevalence rates, including case ascertainment sources, case inclusion criteria, and inclusion of elective terminations and stillbirths. The impact of each of these factors on prevalence rates may be defect-specific. CONCLUSIONS: We conclude that while some variability is expected due to differences in the true prevalence of birth defects, extreme differences among states are more likely due to differences in surveillance practices. The Birth Defects Prevention Act prompted new initiatives to develop birth defect surveillance systems, but there are no nationally agreed upon standards in existence to guide the process. This study was performed in support of developing standards that will influence new and existing state surveillance systems.

The ST3Gal-I sialyltransferase controls CD8+ T lymphocyte homeostasis by modulating O-glycan biosynthesis.

T lymphocyte activation evokes distinct changes in cell surface O-glycans. CD8+ T cells undergo an elimination of sialic acid on core 1 O-glycans and an induction of core 2 O-glycans until either apoptotic death or differentiation into memory cells. We find that the ST3Gal-I sialyltransferase is required for core 1 O-glycan sialylation and its deficiency induces core 2 O-glycan biosynthesis. Apoptosis ensues with the loss of peripheral CD8+ T cells in the absence of immune stimulation. Cell surface ligation of the ST3Gal-I substrate CD43 recapitulates this phenotype by a caspase 3-independent mechanism. Control of core 1 O-glycan sialylation in T lymphocytes by ST3Gal-I comprises a homeostatic mechanism that eliminates CD8+ T cells by apoptosis while facilitating the production of viable CD8+ memory T cells.

Monitoring of PPAR alpha protein expression in human tissue by the use of PPAR alpha-specific MAbs.

We report the production and characterization of two PPAR alpha subtype-specific monoclonal antibodies raised against the N-terminal domain of PPAR alpha. P alpha b 11.80A is a Western-reactive antibody, whereas P alpha b 32.51 is useful for immunohistochemistry. Both antibodies exhibited high affinity against the immunogen based on BIAcore analysis, recognized full-length PPAR alpha protein in PPAR alpha-transfected CV-1 cells, and displayed no cross-reactivity against the N-terminal domains of PPAR gamma or PPAR delta proteins as demonstrated by various immunoassays. The application of these antibodies to a panel of normal human tissues revealed that PPAR alpha protein expression is highest in skeletal muscle, liver, and kidney, consistent with previously reported mRNA expression data. These antibodies provide us with valuable tools to further explore the function of PPAR alpha.

RoBo-1, a novel member of the urokinase plasminogen activator receptor/CD59/Ly-6/snake toxin family selectively expressed in rat bone and growth plate cartilage.

Using differential display polymerase chain reaction, we cloned a novel cDNA named RoBo-1 from rat tibia. RoBo-1 is abundantly expressed in bone, including the hypertrophic chondrocytes of the growth plate where cartilage is remodeled into bone. RoBo-1 mRNA expression increased in response to two modulators of bone metabolism, estradiol and intermittent mechanical loading, suggesting a role in bone homeostasis. The 1.6-kilobase cDNA encodes a 240-amino acid protein with a cysteine spacing pattern, suggesting that RoBo-1 is a novel member of the urokinase plasminogen activator receptor/CD59/Ly-6/snake toxin family. Furthermore, the C-terminal contains a glycosyl-phosphatidylinositol attachment site, suggesting that it is a cell surface protein similar to other mammalian members of this family. The strongest homology of RoBo-1 is to the snake serum-derived phospholipase A2 inhibitors, which uniquely contain two of the cysteine domains but are secreted proteins. Interestingly, RoBo-1 is likely the first membrane-anchored member of this family containing two cysteine domains. Thus, the tissue specificity, responsiveness to bone protective mediators, along with its relationship to the multifunctional urokinase plasminogen activator receptor/CD59/Ly-6/snake toxin family suggests that RoBo-1 may play a novel role in the growth or remodeling of bone.

Identification of Rad's effector-binding domain, intracellular localization, and analysis of expression in Pima Indians.

In order to characterize the endogenous gene product for rad (ras-related protein associated with diabetes), we prepared antibodies to synthetic peptides that correspond to amino acids (109-121, 178-195, 254-271) within the protein. These antibodies were used to analyze the expression, structure, and function of rad. Western analysis with these antibodies revealed that rad was a 46 kDa protein which was expressed during myotube formation. Further, immunolocalization studies showed that rad localized to thin filamentous regions in skeletal muscle. Interestingly, when muscle biopsies from diabetic and control Pima Indians were compared, no differences in rad protein or mRNA expression were observed. Similarly, no differences were observed in protein expression in diabetic and control Zucker diabetic fatty (ZDF) rats. Functional analysis of muscle rad revealed that its GTP-binding activity was inhibited by the addition of N-ethylmaliemide, GTP, GTP gamma S, and GDP beta S but not ATP or dithiothreitol. Moreover, cytosol-dependent rad-GTPase activity was stimulated by the peptide corresponding to amino acids 109-121. Antibodies corresponding to this epitope inhibited cytosol-dependent rad-GTPase activity. Taken together, the results indicate that 1) rad is a 46 kDa GTP-binding protein localized to thin filaments in muscle and its expression increases during myoblast fusion, 2) expression of rad in Pima Indians and ZDF rats does not correlate with diabetes, and 3) the amino acids (109-121) may be involved in regulating rad-GTPase activity, perhaps by interacting with a cytosolic factor(s) regulating nucleotide exchange and/or hydrolysis.

Paracetamol overdose in man: relationship between pattern of urinary metabolites and severity of liver damage.

The urinary excretion of paracetamol and its conjugates was studied, using a two dimensional thin layer chromatography system, in three volunteers after therapeutic (6-5-26-6 mmoles) doses of the drug, and in 30 patients admitted early after overdoses taken in suicidal attempts. In both volunteers and patients 85-100 per cent of the drug was excreted into the urine--almost entirely as conjugates--in the first 24 hours, which was before biochemical signs of liver damage had appeared. Higher quantities of paracetamol conjugates were recovered from patients who developed moderate of severe liver damage than those less severely affected, although correlations in individuals between quantity excreted and clinical outcome was poor. The pattern of individual paracetamol conjugates changed markedly the higher the ingested dose of the drug. Thus, the excretion of paracetamol sulphate reached a plateau as the administered dose was increased from 20-26-5 mmoles in the volunteers, whilst in patients who developed liver damage after overdose there was also a plateau in the excretion of the glucuronide conjugate. In the latter group, there was a greatly increased production of the cysteine and mercapturic acid conjugates of the drug. These are formed via a highly chemically reactive metabolite of the drug, which binds to glutathione, and if hepatic stores of the latter become depleted, binding will occur instead to hepatocyte macromolecules with ensuing liver damage.

Urinary D-glucaric acid excretion and plasma antipyrine kinetics during enzyme induction.

1 Changes in urinary D-glucaric acid excretion following a 14 day course of antipyrine to produce enzyme induction have been compared in normal volunteers with changes in plasma half lives and steady state levels of antipyrine. 2 Urinary D-glucaric acid excretion for the group rose significantly with induction, while there was a significant fall in the mean plasma antipyrine half life and steady state levels. The extent of the increase in urinary D-glucaric acid excretion was inversely related to the pre-induction level, and this also applied to the change in antipyrine half lives. 3 Although in individuals, urinary D-glucaric acid excretion and plasma levels of antipyrine changed in parallel, there was no numerical correlation in the group as a whole between these two tests either before or after enzyme induction. 4 These findings are consistent with other recently reported evidence that plasma drug kinetics and other microsomal enzyme functions are not necessarily affected to the same degree by agents with enzyme inducing properties.