Combined screening for autoantibodies to IA-2 and antibodies to glutamic acid decarboxylase in first degree relatives of patients with IDDM. The DENIS Study Group. Deutsche Nikotinamid Interventions-Studie

To determine the value of antibodies to the intracytoplasmic domain of the tyrosine phosphatase IA-2 (anti-IA-2ic) and glutamic acid decarboxylase (GADA) for identification of subjects at risk for insulin-dependent diabetes mellitus (IDDM) we investigated 1238 first degree relatives of patients with IDDM for the presence of anti-IA-2ic and GADA and compared the results with cytoplasmic islet cell antibodies (ICA). Anti-IA-2ic were observed in 54 (4.4%) first degree relatives, in 51 of 86 (59.3%) ICA positive relatives and in 3 of 4 individuals who developed overt IDDM within a follow-up period of 1 to 28 months. GADA were found in 78 of 1238 (6.3%) first degree relatives. They were detected in 22 of 35 (62.9%) sera with ICA alone and in 1 of 3 subjects with anti-IA-2ic in the absence of ICA. Of the 1238 subjects 37 (3.0%) sera were positive for all three antibodies. Both anti-IA-2ic and GADA were positively correlated with high levels of ICA. Anti-IA-2ic and GADA were detected in 39.1 and 47.8% of subjects with ICA of less than 20 Juvenile Diabetes Foundation units (JDF-U) but in 66.7 and 76.2% of individuals with ICA of 20 JDF-U or more, respectively (p < 0.05). The levels of ICA and GADA in first degree relatives with at least one additional marker were significantly higher than in subjects with ICA alone (p < 0.005) or GADA alone (p < 0.03). The combination of anti-IA-2ic and GADA identified 84.9% of all ICA positive subjects and 93.7% of individuals with high level ICA (> or = 20 IDF-U). All 4 individuals who progressed to IDDM had either IA-2ic or GADA. Our data indicate that primary screening for anti-IA-2ic and GADA provides a powerful approach with which to identify subjects at risk for IDDM in large-scale population studies which may represent the basis for the design of new intervention strategies.

Determinants of bone and blood lead levels among community-exposed middle-aged to elderly men. The normative aging study

Levels of lead in bone serve as a dosimeter for cumulative exposure to lead; moreover, lead in bone may serve as an internal source of circulating lead many years after environmental exposure has ceased. The authors measured lead in blood and used a K-x-ray fluorescence instrument to measure lead in the tibia (cortical) and patella (trabecular) bones in a cross-sectional survey of 719 middle-aged to elderly male participants in the Normative Aging Study who were without unusual occupational exposures to lead and who were healthy when enrolled in 1962-1965. Blood lead levels ranged from < 1 to 27.9 micrograms/dl, with a geometric mean of 5.7 micrograms/dl. Tibia and patella lead level ranges (geometric means) were < 1-51 (20.8) micrograms/g and 3-77 (29.8) micrograms/g, respectively. In backwards elimination multivariate regression models that considered age, race, education, retirement status, measures of both current and cumulative smoking, and alcohol consumption, the factors that remained significantly related to higher levels of both tibia and patella lead were higher age and measures of cumulative smoking, and lower levels of education. In the final model predicting blood lead that began with these same covariates and also included tibia and patella lead, the factor that accounted for the dominant portion of the variance in blood lead was patella lead. After adjustment for measurement error, a rise in patella lead from the median of the lowest to the median of the highest quintiles (13-56 micrograms/g) corresponded to a rise in blood lead of 4.3 micrograms/dl. The authors conclude that bone lead levels are substantial and comprise the major source of circulating lead in these men.

Co-expression of the neurokinin NK2 receptor and G-protein components in the fission yeast Schizosaccharomyces pombe

The fission yeast Schizosaccharomyces pombe has proven useful for studying molecular interactions between a range of signal transduction components. We now report the first co-expression of a mammalian seven-transmembrane receptor and G-protein components in S. pombe. We selected the human neurokinin NK2 receptor together with its G-protein-signalling partner Gq for this study. Yeast membrane fractions showed high levels of NK2 receptor-binding activity (1159 +/- 534 (n = 3) fmol/mg protein) although initial experiments with intact cells revealed an absence of receptors at the cell surface. Using a construct comprising the NK2 coding sequence fused with the signal sequence from an endogenous phosphatase (phoI), we detected approximately 400 NK2 receptors/cell in unbroken yeast. Successful co-expression of the NK2 receptor with the G-protein subunits G alpha q, beta 1 or beta 2 and gamma 3 failed to modulate agonist binding, suggesting the absence of functional interaction between these components. As an alternative test of G alpha q function, we next expressed its downstream effector target phospholipase C-beta 1 (PLC beta 1) in S. pombe. Although PLC beta 1 undergoes powerful in vitro activation by G alpha q derived from baculovirus-infected Sf9 cells and mammalian cells, G alpha q expressed in S. pombe is totally ineffective. Similar results were also achieved with the G-protein subunit G alpha 16. Together, these data suggest that seven-transmembrane receptors can be expressed in S. pombe at high levels and directed to the cell surface although their interaction with co-expressed G-proteins in undetectable. Production of inactive G alpha-chains in S. pombe may account for these observations.

Activation of phospholipase C gamma in Schizosaccharomyces pombe by coexpression of receptor or nonreceptor tyrosine kinases

The fission yeast Schizosaccharomyces pombe has no detectable endogenous receptor tyrosine kinases or associated signalling apparatus, and we have used this cell system to reconstitute mammalian platelet-derived growth factor beta (PDGF beta) receptor-linked activation of phospholipase C gamma 2 (PLC gamma 2). The PDGF beta receptor migrates as a glycosylated protein of 165 kDa associated exclusively with membrane fractions. No tyrosine autophosphorylation was detected when PDGF beta was expressed alone. PLC gamma 2 appears as a 140-kDa protein distributed between particulate and soluble fractions which exhibits characteristic selectivity for phosphatidylinositol 4,5-bisphosphate and is sensitive to powerful activation by Ca2+. When coexpressed, both PDGF beta and PLC gamma 2 undergo tyrosine phosphorylation, and this is accompanied by a > 26-fold increase in [3H]inositol 4,5-biphosphate ([3H]IP2) and [3H]inositol 1,4,5-triphosphate [3H]IP3 production. Treatment with the tyrosine phosphatase inhibitor pervanadate further increased PLC gamma 2 tyrosine phosphorylation as well as [3H]IP2 and [3H]IP3 generation. Phosphorylated PLC gamma 2 was found predominantly in membrane fractions. To test a nonreceptor tyrosine kinase, we then expressed the human proto-oncogene c-src together with its negative regulator Csk. These were immunodetectable as bands at 60 kDa (c-Src) and 50 kDa (Csk) and distributed between membrane and cytosolic fractions. When yeast coexpressing c-Src, Csk, and PLC gamma 2 was incubated with pervanadate, PLC gamma 2 was tyrosine phosphorylated and [3H]IP2 and [3H]IP3 production increased 11.0- and 7.0-fold, respectively. Csk expressed alone with PLC gamma 2 was ineffective. Similar PLC gamma 2 activation was observed upon in vitro mixing with the extracts expressing either c-Src or the PDGF beta receptor. In summary, this is the first report of a reconstitution of mammalian tyrosine kinase-linked effector activation in yeast cells and also the first demonstration of direct PLC gamma 2 activation by the proto-oncogene c-src. These observations indicate that S. pombe provides a powerful cell system in which to study critical molecular interactions and activities underlying receptor and nonreceptor tyrosine kinase-dependent cell signaling.

Low-level lead exposure and renal function in the Normative Aging Study

Occupational and environmental lead exposure has been associated with significant impairment in renal function. The authors studied the cross-sectional relation between creatinine clearance and blood lead concentration in a population of 744 men participating in the Normative Aging Study of the Department of Veterans Affairs between July 1988 and April 1991. These men, aged 43-90 years, were recruited from communities in the Greater Boston, Massachusetts, area and were selected without regard to lead exposure. The mean values for blood lead concentration and creatinine clearance rate were 8.1 micrograms/dl (standard deviation, 3.9 micrograms/dl) and 88.2 ml/minute (standard deviation, 22.0 ml/minute), respectively. Independent relations of creatinine clearance to blood lead were assessed by multivariate linear regression analysis, with adjustment for various potential confounders. In multivariate linear regression models, the rate of creatinine clearance was significantly and negatively associated with increasing levels of blood lead, even after adjustment for age, body mass index, and use of diuretic and analgesic medications (the beta-coefficient for ln blood lead measured in microgram[microgram/dl]-1 was -0.030; standard error = 0.014, p = 0.037). A rise in ln blood lead of 10.0 micrograms/dl was associated with a decrease in the ln creatinine clearance rate of 10.4 ml/minute. These results support the hypothesis that exposure to low-level environmental lead correlates with a significant decrement in renal function.

Relation between blood lead and urinary biogenic amines in community-exposed men

The cross-sectional relation between levels of urinary biogenic amines (dopamine, epinephrine, norepinephrine, and serotonin) and levels of blood lead was examined in a study of 645 male participants from a longitudinal study of aging. This stable population of men had initially been recruited from communities in and around Boston, Massachusetts, and had not been selected with regard to lead exposure. Blood lead samples and 24-hour and 2-hour urine specimens were collected during regularly scheduled clinic visits. In multivariate linear regression step-forward models, 24-hour epinephrine excretion was significantly and positively associated with blood lead (beta = 0.101 microgram(microgram/dl)-1 blood lead, SE (standard error) (beta) = 0.045, p = 0.026). Twenty-four-hour norepinephrine excretion was positively associated with blood lead (beta = 0.023 microgram(microgram/dl)-1 blood lead, SE(beta) = 0.029, p = 0.425), and both 24-hour dopamine (beta = -4.35 microgram(microgram/dl)-1 blood lead, SE(beta) = 6.90, p = 0.529) and 2-hour serotonin (beta = -0.348 microgram(microgram/dl)-1 blood lead, SE(beta) = 0.277, p = 0.210) excretion were negatively associated with blood lead; however, these relations did not achieve statistical significance. An increase of 10 micrograms/dl in blood lead was associated with an increase in epinephrine excretion of 11 micrograms/24 hours. These results support the hypothesis that epinephrine metabolism is influenced by low levels of lead exposure.

An investigation of a workplace cluster of Bell's palsy

We undertook a study to confirm the existence of an apparent cluster of Bell's palsy in an industrial plant ("W4"), and to test etiologic hypotheses regarding chemical exposures, immune suppression, and infectious etiologies. Cases were enumerated by questionnaire. Employees with a history of Bell's palsy ("cases") were invited to participate in a study that included medical history, T cell studies, viral and Lyme disease serologies, and blink reflex studies. Thirty-three unaffected volunteers from W4 and 32 from a comparison building were also tested. Extensive environmental studies were carried out in W4, evaluating infectious, chemical, and radiation exposures. The lifetime incidence of self-reported Bell's palsy was 11.6/10,000 person-years (P-Y) in W4 and 2.4 cases/10,000 P-Y in the comparison building (RR = 4.8, P < .05); the comparison rate was similar to that reported in previous population studies. When restricted to cases occurring after the onset of work, the W4 incidence was 29.2 cases/10,000 P-Y, compared to 4.8 cases/10,000 P-Y in the comparison building (RR = 6.1, P < .05). The cases and noncases did not differ with respect to clinical histories or infectious disease titers. The W4 noncases had small but significant decreases in T lymphocyte (1974 +/- 86 vs 2291 +/- 103) and CD4 (1083 +/- 318 vs 1459 +/- 494) counts compared to the remote noncases. The cases had significantly prolonged RR1, LR1, and LFC values compared to both groups of noncases. No medical or environmental factors were identified that could explain an excess of disease.

Yeast alpha-mating factor receptor and G-protein-linked adenylyl cyclase inhibition requires RAS2 and GPA2 activities

Saccharomyces cerevisiae expresses two RAS gene products (RAS1 and RAS2) highly homologous to mammalian p21ras which mediate glucose-stimulated cyclic-AMP formation. Mating pheromone inhibits RAS-linked adenylyl cyclase activation and this is dependent upon the alpha-factor receptor (STE2) and its associated G-protein beta-subunit (STE4). We now show that this pheromone effect is independent of mating pathway signalling components "downstream" of STE4 but displays an absolute requirement for an additional G-protein alpha-subunit encoded by GPA2. alpha-mating factor effects also involve a specific suppression of normal RAS2 activity as the constitutively activated mutant RAS2vall9 as well as wild type. RAS1 are insensitive to inhibition. Interaction between GPA2, STE4-STE18, RAS2 and adenylyl cyclase in yeast could give important insight into signalling pathways controlling normal and oncogenic p21ras activity in man.

Purification and characterization of the DNA-binding protein Ner of bacteriophage Mu

The construction is described of a plasmid (pL-ner) which directs the high-level production of the bacteriophage Mu Ner protein in Escherichia coli. The protein, recovered in the soluble cellular fraction, was susceptible to in vivo proteolytic processing, in many host strains, but not in E. coli B, a natural lon- prototroph. A simple purification method is described which takes advantage of the basic nature of the protein. The purified protein was shown to be physically and chemically homogeneous and to have an amino acid sequence identical to that predicted for the authentic protein. The protein was also shown to have in vitro biological activity, as measured by specific binding to a DNA fragment containing the consensus Ner-binding sequence, and in vivo biological activity as the protein produced by the pL-ner plasmid allowed lysogenic-like maintenance of a Mu prophage c mutant unable to synthesise a functional Mu repressor.

Purification and characterization of human interleukin-1 alpha produced in Escherichia coli

The production of human interleukin-1 alpha (IL-1 alpha) in Escherichia coli is described together with a method for its purification. The isolated protein was shown to be pure and physically homogeneous. The in vitro biological activity of IL-1 alpha was tested with the mononuclear-cell factor and the lymphocyte-activating factor assays. The specific activity determined with both assays was about 3 X 10(7) units mg-1 and is similar to that observed with recombinant human IL-1 beta. The purified protein was resolved by chromatofocusing into two species of isoelectric points 5.45 and 5.20 (75% and 25%, respectively, of the total protein). Both species had similar chemical properties and biological activities to the unfractionated protein. The charge difference between the species was attributed to the deamidation of a single Asn or Gln residue.

Purification and characterization of human interleukin-1 beta expressed in recombinant Escherichia coli

The high-level expression of human interleukin-1 beta in Escherichia coli is described. The protein contributes about 12% of the total cell protein and is associated with the soluble cytoplasmic fraction of the cell. A method for the purification of the protein is given which is based on anion- and cation-exchange chromatographies. The isolated protein, shown to be homogeneous by several analytical methods, has been characterized by amino acid analysis, N- and C-terminal sequence analysis and analytical centrifugation. The protein is biologically active as demonstrated by two different in vitro assays, namely, the mononuclear cell factor (IL-1/MCF) assay and lymphocyte activating factor (IL-1/LAF) assay. The specific activities determined with the IL-1/MCF and IL-1/LAF assays, are 2 X 10(7) and 4 X 10(7) units mg-1, respectively.