Impact of a cleaner-burning cookstove intervention on blood pressure in Nicaraguan women.

Few studies have evaluated the cardiovascular-related effects of indoor biomass burning or the role of characteristics such as age and obesity status, in this relationship. We examined the impact of a cleaner-burning cookstove intervention on blood pressure among Nicaraguan women using an open fire at baseline; we also evaluated heterogeneity of the impact by subgroups of the population. We evaluated changes in systolic and diastolic blood pressure from baseline to post-intervention (range: 273-383 days) among 74 female cooks. We measured indoor fine particulate matter (PM(2.5); N = 25), indoor carbon monoxide (CO; N = 32), and personal CO (N = 30) concentrations. Large mean reductions in pollutant concentrations were observed for all pollutants; for example, indoor PM(2.5) was reduced 77% following the intervention. However, pollution distributions (baseline and post-intervention) were wide and overlapping. Although substantial reductions in blood pressure were not observed among the entire population, a 5.9 mmHg reduction [95% confidence interval (CI): -11.3, -0.4] in systolic blood pressure was observed among women aged 40 or more years and a 4.6 mmHg reduction (95% CI: -10.0, 0.8) was observed among obese women. Results from this study provide an indication that certain subgroups may be more likely to experience improvements in blood pressure following a cookstove intervention.

School environmental conditions and links to academic performance and absenteeism in urban, mid-Atlantic public schools.

School facility conditions, environment, and perceptions of safety and learning have been investigated for their impact on child development. However, it is important to consider how the environment separately influences academic performance and attendance after controlling for school and community factors. Using results from the Maryland School Assessment, we considered outcomes of school-level proficiency in reading and math plus attendance and chronic absences, defined as missing 20 or more days, for grades 3-5 and 6-8 at 158 urban schools. Characteristics of the environment included school facility conditions, density of nearby roads, and an index industrial air pollution. Perceptions of school safety, learning, and institutional environment were acquired from a School Climate Survey. Also considered were neighborhood factors at the community statistical area, including demographics, crime, and poverty based on school location. Poisson regression adjusted for over-dispersion was used to model academic achievement and multiple linear models were used for attendance. Each 10-unit change in facility condition index, denoting worse quality buildings, was associated with a decrease in reading (1.0% (95% CI: 0.1-1.9%) and math scores (0.21% (95% CI: 0.20-0.40), while chronic absences increased by 0.75% (95% CI: 0.30-1.39). Each log increase the EPA's Risk Screening Environmental Indicator (RSEI) value for industrial hazards, resulted in a marginally significant trend of increasing absenteeism (p < 0.06), but no association was observed with academic achievement. All results were robust to school-level measures of racial composition, free and reduced meals eligibility, and community poverty and crime. These findings provide empirical evidence for the importance of the community and school environment, including building conditions and neighborhood toxic substance risk, on academic achievement and attendance.

Tryptophan exposure in various conformational isomers of bovine prothrombin fragment 1. An acrylamide quenching study.

In order to assess the importance of a variety of environmental factors on the structure of bovine prothrombin fragment 1, we have examined acrylamide quenching of fragment 1 intrinsic fluorescence. Tryptophan exposure, determined from Stern-Volmer plots, is heterogeneous with one or more of the three fragment 1 tryptophans being exposed to solvent. In the presence of Ca2+ or Mg2+ even the most accessible tryptophan(s) are relatively buried. Only small differences in tryptophan exposure may exist between fragment 1-Ca2+ and fragment 1-Mg2+ complexes. Lowering pH, on the other hand, results in increased tryptophan exposure. Finally, structural isomers of fragment 1 which exist in the absence of metal ions have identical tryptophan exposure as determined by acrylamide quenching and fluorescence intensity.

Interaction of fluorinated ether anesthetics with artificial membranes.

Fluorine-19 nuclear magnetic resonance spectroscopy is applied to the study of the environment of dipalmitoyl phosphatidylcholine-bound fluorinated ether anesthetics (enflurane, fluoroxene and methoxyflurane) both below and above the lipid gel to liquid crystal phase transition temperature. Line widths and spin-lattice relaxation time (T1) measurements are consistent with substantial immobilization of the lipid-bound anesethetic molecules. Heating anesthetic/lipid mixtures above the lipid transition temperature leads to narrowing of the lipid-bound anesthetic fluorine resonances accompanied by little or no change in anesthetic fluorine-19 chemical shifts, suggesting that although the mobility of the bound anesthetic increases at the higher temperature, the nature of the anesthetic-lipid interaction changes little as a result of this phase change. Differential scanning calorimetric studies of the effects of these anesthetics on the phase transition behavior of the phospholipid indicate that the regions of the bilayer in which volatile anesthetics partition at lower concentrations are different from the regions in which they partition at higher concentrations.

Dye binding probes of lipid-binding structures. An investigation of 2-p-toluidinylnaphthylene-6-sulfonate binding to human and bovine prothrombin and fragment 1 in the presence and absence of calcium and magnesium ions.

TNS (2-p-toluidinylnaphthylene-6-sulfonate) binds to human and bovine prothrombin and Fragment 1 in the absence and presence of added Ca2+. The stoichiometry of TNS binding is 1:1 for human and bovine prothrombin and Fragment 1. The Ca2+-dependence of the fluorescence of TNS bound to bovine prothrombin Fragment 1 yields a modified Hill plot slope of 2.7, which is consistent with the slope obtained by monitoring the Ca2+ dependence of protein fluorescence quenching, CD changes and phospholipid binding. Mg2+ has have no effect on the fluorescence of TNS-prothrombin fluorescence. TNS binding to the amino-terminal region of prothrombin is the first relatively simple probe of the subtle and complex relationship which exists between protein structure and phospholipid binding.

Physical studies on isolated human prothrombin fragment-2. Comparisons with human prothrombin fragment-1.

Variation of pH strongly affects the fluorescence intensity of human prothrombin fragment-1 in a manner suggesting contributions from a number of protropic equilibria including groups with apparent pKa values near 3.0. These results suggest a structural role for pK1a of gamma-carboxyglutamic acid noieties. Added calcium ions (9 mM calcium chloride) quench the fluorescence titration curve uniformly above pH 4. Below pH 4, however, the titration curve in the presence of calcium ions suggests that calcium-ion-dependent processes leading to fluorescence quenching are pH-dependent. Upon back titration of human fragment-1, from pH 9, hysteresis is observed. Human prothrombin fragment-2 fluorescence titration curves are relatively broad at low pH suggesting the titration of normal carboxyl groups. The titration curves of fragment-2 are not affected by the presence of calcium ions, and hysteresis occurs upon back titration from low pH values. Circular dichroism (CD) Cotton effects appear at 232 nm and 280 nm and a trough appears at 203 nm in the CD spectrum of human prothrombin fragment-2. The Cotton effects in the region from 230 nm to 300 nm are sensitive to pH, ellipticity values at 232 nm increasing from approximately 300 at pH 2.5 to 1300 (degree-cm/decimole) at neutral pH and finally become negative at high pH values. In contrast to fragment-1, at neutral pH the fragment-2 Cotton effect at 232 nm is insensitive to the presence of 8 mM calcium chloride.

A kinetic model describing the interaction of bovine prothrombin fragment 1 with calcium ions.

A kinetic model is derived for the interaction of bovine prothrombin fragment 1 with calcium ions. The model requires binding of a minimum of two calcium ions for induction of the observed biphasic fluorescence decrease as a function of time. The model is shown to be consistent with experimental kinetic and equilibrium data by fitting theoretical curves for the biphasic fluorescence change to the data through exact solution of the nonlinear differential rate equations derived from the model. The rate constants for the binding of these two required calcium ions are calculated from the solutions as best fit parameters. The thermodynamic equilibrium constants, K1 and K2, for the binding of these two calcium ions are calculated from ratios of the forward and reverse rate constants as 0.6 X 10(4) and 5.4 X 10(4), respectively. Thus, the model correctly predicts positively cooperative calcium ion binding for at least the two calcium ions required to induce fluorescence quenching.

Comparison of the membrane-related effects of cytarabine and other agents on model membranes.

UNLABELLED: The membrane-associated effects of a series of chemotherapeutic and other drugs were examined via differential scanning calorimetry and by their modulation of the action of porcine phospholipase A2 (PLA2) on bilayer substrates. The drugs examined included: cytarabine, amino-glycoside antibiotics, adriamycin, dibucaine, butacaine, and VP-16. The bilayers employed were phase-separated ternary lipid mixtures containing dimyristoylphosphatidylcholine: palmitoyllysolecithin: and either hexadecanoic acid (fatty acid ternary mixture) or hexadecanol (alcohol ternary mixture). Effects of the more hydrophilic drugs (cytarabine and aminoglycoside antibiotics) on the calorimetric profiles of the negatively charged (fatty acid-containing) and the neutral (hexadecanol-containing) ternary lipid mixtures indicate that the interaction of these drugs with biomembranes is likely to be dominated by electrostatic interactions. All of the drugs investigated, including the more hydrophobic adriamycin, dibucaine, butacaine, and VP-16, affected the phase equilibrium in the membrane and exhibited apparent noncompetitive inhibition of the action of PLA2 on bilayers composed of ternary lipid substrates. In addition, cytarabine inhibited fusion of fatty acid-containing ternary mixtures. CONCLUSIONS: These drug:membrane interactions leading to a shift in the phase equilibria were apparently regiospecific. Hydrophilic drug:membrane interactions included an important electrostatic component. The effects of all of the drugs employed in this study on the action of PLA2 on a bilayer substrate (fatty acid-containing ternary lipid mixture) are hypothesized to be a result of the drug-mediated shift in phase equilibria away from the optimally active phase distribution. As a result, PLA2 binds with normal affinity to the membrane, but its membrane substrate is not catalytically turned over. It is evident that these drugs can directly affect cellular homeostasis in a manner that can show a dependence on the nature of the membrane surface.

Misinterpretation of body sensations in panic disorder.

Cognitive accounts of panic predict that panic disorder patients will be particularly prone to misinterpret autonomic sensations. Several studies have produced results consistent with this prediction, but each is open to alternative interpretation. To clarify matters, 2 studies administered the Body Sensations Interpretation Questionnaire (BSIQ) to panic patients and controls. Panic patients were more likely to interpret ambiguous autonomic sensations as signs of immediately impending physical or mental disaster and were more likely than other anxiety disorder patients and nonpatients to believe these interpretations. In a 3rd study, a brief version of the BSIQ was shown to have satisfactory test-retest reliability, to change with treatment, and to discriminate treatments that varied in their effects on panic.

Photofrin photosensitization. Correlation of Photofrin:erythrocyte binding processes with photolysis.

Unilamellar suspensions of dimyristoylphosphatidylcholine (DMPC) can be utilized to remove Photofrin from the erythrocyte. This enables correlation of the Photofrin membrane-binding processes with Photofrin-sensitized photolysis. The observed rates of erythrocyte biding as well as the observed rates of removal of PHotofrin from the erythrocyte membrane suggest the existence of two Photofrin species that differ in their rates of exchange between the erythrocyte and buffer phases. Selective depletion and readdition of these Photofrin species to the erythrocyte membrane permits evaluation of their separate and joint photolytic efficiencies. These rapidly and slowly exchanging membrane-bound Photofrin species are separately much less efficient photosensitizers than the two species together. The two Photofrin species exhibit essentially identical fluorescence emission spectra in the presence of DMPC. Nevertheless, models consistent with the results involve partitioning by chemically distinct Photofrin components or partitioning of chemically similar Photofrin components into distinct membrane environments, or a combination of these.

Estimation of apparent quadrupolar coupling constants for complexes of magnesium ions with mono- and dicarboxylic acid ligands. Applications to magnesium ion: protein interactions.

25Mg+2 ion NMR studies of complexes of magnesium ions with acetate and malonate ligands have yielded apparent quadrupolar coupling constants, chi, of approximately 1.5 MHz. The aquo magnesium ion yields a smaller chi value of 0.12 MHz, consistent with its expected higher symmetry. chi values for magnesium ion: acetate and magnesium ion: malonate complexes are utilized to calculate observed linewidths for magnesium ion: bovine prothrombin fragment 1 and magnesium ion: human Factor XII interactions. These calculated values are compared with observed values and implications of the agreement are discussed.

The pH-dependence of the equilibrium between the fast- and slow-folding forms of bovine prothrombin fragment 1: a role for pH-induced self-association?

Examination of the pH- and ionic strength (mu)-dependence of the equilibrium between fast- and slow-folding forms of bovine prothrombin fragment 1 reveals a sharp dependence of Keq ([% fast-folding form]/[% slow-folding form]) and % fluorescence quenching (%Q) on pH at low mu, and the absence of a pH-dependence of Keq at high mu (0.1 M NaCl) and much reduced pH-dependence of %Q, suggesting that the ionization process is coupled to other processes, such as self-association. The observed low mu pH effect on Keq amounts to a 10% increase in the % of the fast-folding form of prothrombin at low pH. We hypothesize the existence of a pH-dependent self-association of bovine prothrombin fragment 1. This process is associated with a conformation change involving an ionizing group with pKa in the neighborhood of 6.5 and a change in Keq from 0.27 to 0.45.

The effects of calcium ions and pH on bovine prothrombin fragment 1. Intrinsic fluroescence studies.

The effects of pH and Ca2+ on the intrinsic fluorescence of bovine prothrombin fragment 1 were investigated to deduce the nature of protein functional groups involved in Ca2+ binding to fragment 1. From pH values of 9 to 3, increasing the H3O+ concentration results in quenching of the fluorescence of fragment 1. Reversible pH-titration curves are obtained which appear to consist of two regions. From pH 4 to pH6.5 a broad titration curve is obtained, whereas from pH6.5 to 9 a more pronounced titration behaviour is evidenced by a group or groups on fragment 1 with an apparent pKa of approx. 7.5. In contrast, the apparent association constant for Ca2+ and fragment 1 shows a sharp pH-dependence in the region between pH7 and 8 with tighter Ca2+ binding at higher pH values. A PKa of approx. 7.5 can be estimated for the group or groups on fragment 1 linked to the tight binding of Ca2+. Both H3O+ and Ca2+ result in blue-shifts in the wave-lengths of fragment-1 emission. These results are interpreted in terms of H+ - and Ca2+ - induced changes in the conformation of fragment 1 as a result of surface-charge neutralization.

Calcium and magnesium binding to gamma-carboxyglutamic acid-containing peptides via metal ion nuclear magnetic resonance.

The determination of binding constants of metal ions to biomolecules is approachable via many techniques. Metal ion NMR spectroscopy is an alternative to more traditional techniques and is complementary to them, particularly in investigations of the interactions of metal ions with relatively small peptides containing multiple ionizing groups. The method requires relatively small amounts of material, is fairly fast, and is carried out at equilibrium. Our study has been of calcium and magnesium ion binding to gamma-carboxyglutamic acid (Gla)-containing peptides. Dissociation constants of approximately 0.6 mM for the binding of either metal ion to Z-D-Gla-D-Gla-OMe have been obtained. The procedure for determination of these constants via metal ion NMR is discussed.

Cooperativity in the calcium ion-induced quenching of the intrinsic fluorescence of a series of normal and GLA-deficient bovine prothrombin fragment 1 molecules.

Ca2+ titrations of the intrinsic fluorescence of a series of gamma-carboxyglutamic acid (GLA)-deficient bovine prothrombin fragments 1 yield response Hill plot parameters useful for characterization of the metal ion-binding process. 11-, 10-, and 9-GLA fragments 1 exhibit Tm (the (Ca2+)total concentration at which ln (B/F) = 0 in the response Hill plot) values between 0.2 and 0.3 mM. A 22-fold increase in Tm to 5.4 mM is observed for 8-GLA fragment 1. Tm decreases to 3.8 mM for the 7- and 6-GLA proteins. The value of h, about 2.8 +/- 0.2 for 11-, 10-, and 9-GLA fragments 1, abruptly decreases to 1.2-1.3 for 8-, 7-, and 6-GLA fragments 1. The observed degree of quenching induced by saturating levels of calcium ions is affected by both changes in the intrinsic fluorescence of the metal ion-free proteins and in the maximum possible degree of quenching in the presence of calcium. The kinetic characteristics of the calcium ion-induced quenching of the intrinsic fluorescence of 6-GLA fragment 1 are identical to those observed in 10-GLA fragment 1, suggesting that the fluorescence quenching observed in the 6- and 10-GLA fragments 1, while different in magnitude, involves similar processes. Observation of an abrupt change in the relative electrophoretic mobilities of 11- to 9-GLA fragments 1 compared to 8- to 6-GLA fragments 1, in the absence or presence of Ca2+, suggests the existence of a major protein conformation change which occurs concomitantly with the noted changes in Tm and h response Hill plot parameters. Molecular mechanics calculations suggest a structural hypothesis unifying these observations. Central to this model is the presumption of the existence of hydrogen bond-mediated interactions between metal ion-binding sites.

Interleukin-2 self-association.

The self-association of human recombinant interleukin-2 (IL-2) from E. coli was explored. Self-association, with an apparent Kd of 0.6 micromolar, has pronounced effects on (1) the surface exposure of Trp-121, deduced from quenching studies employing potassium iodide and acrylamide, (2) the apparent quantum yield of Trp-121, the fluorescence of Trp-121 in IL-2 aggregates is 4-fold lower than in IL-2 "monomers", and (3) IL-2-mediated phospholipid vesicle fusion/aggregation.