Phobic anxiety in 11 nations. Part I: Dimensional constancy of the five-factor model.

The Fear Survey Schedule-III (FSS-III) was administered to a total of 5491 students in Australia, East Germany, Great Britain, Greece, Guatemala, Hungary, Italy, Japan, Spain, Sweden, and Venezuela, and submitted to the multiple group method of confirmatory analysis (MGM) in order to determine the cross-national dimensional constancy of the five-factor model of self-assessed fears originally established in Dutch, British, and Canadian samples. The model comprises fears of bodily injury-illness-death, agoraphobic fears, social fears, fears of sexual and aggressive scenes, and harmless animals fears. Close correspondence between the factors was demonstrated across national samples. In each country, the corresponding scales were internally consistent, were intercorrelated at magnitudes comparable to those yielded in the original samples, and yielded (in 93% of the total number of 55 comparisons) sex differences in line with the usual finding (higher scores for females). In each country, the relatively largest sex differences were obtained on harmless animals fears. The organization of self-assessed fears is sufficiently similar across nations to warrant the use of the same weight matrix (scoring key) for the FSS-III in the different countries and to make cross-national comparisons feasible. This opens the way to further studies that attempt to predict (on an a priori basis) cross-national variations in fear levels with dimensions of national cultures.

The use of hydrogen peroxide to enhance the efficacy of doxorubicin hydrochloride in a murine bladder tumor cell line.

PURPOSE: We determined whether the cytotoxicity of doxorubicin hydrochloride would be enhanced by adding hydrogen peroxide as a source of oxygen free radicals. MATERIALS AND METHODS: Mouse bladder tumor cells (MBT-2) were grown in RPMI 1640 medium and treated with various concentrations of doxorubicin hydrochloride for 2 hours. Protein content was assayed as a measure of cell growth. A similar set of experiments was done with cells exposed to hydrogen peroxide only and combined doxorubicin and hydrogen peroxide. Protein content was again assayed as a measure of cell growth. Cells were also assayed for glutathione peroxidase and malonyl dialdehyde, a product of lipid peroxidation, to determine the mechanism of cell damage. Furthermore, MBT-2 cells were incubated with 100 M. alpha-tocopherol, a free radical scavenger, before exposure to hydrogen peroxide to determine whether the effects of hydrogen peroxide could be reversed. RESULTS: We observed a dose dependent inhibition of MBT-2 cell growth after exposure to doxorubicin hydrochloride. Exposure to doxorubicin and hydrogen peroxide resulted in greater cell growth inhibition than exposure to either agent alone. The effects of hydrogen peroxide on cell proliferation were reversed by pre-incubation with alpha-tocopherol. CONCLUSIONS: As a source of oxygen free radicals, hydrogen peroxide enhances the antiproliferative effect of doxorubicin hydrochloride on a mouse bladder tumor cell line. Thus, hydrogen peroxide may be a relatively inexpensive, nontoxic method of augmenting the cytotoxicity of doxorubicin hydrochloride. Further studies are warranted to determine whether these observations may have clinical application.

Normative studies with the Scale for Interpersonal Behaviour (SIB): II. US students. A cross-cultural comparison with Dutch data.

The Scale for Interpersonal Behaviour (SIB), a multidimensional, self-report measure of state assertiveness, was administered to a nationwide sample of 2375 undergraduates enrolled at 11 colleges and universities across the USA. The SIB was developed in the Netherlands for the independent assessment of both distress associated with self-assertion in a variety of social situations and the likelihood of engaging in a specific assertive response. This is done with four factorially-derived, first-order dimensions: (i) Display of negative feelings (Negative assertion); (ii) Expression of and dealing with personal limitations; (iii) Initiating assertiveness; and (iv) Praising others and the ability to deal with compliments/praise of others (Positive assertion). The present study was designed to determine the cross-national invariance of the original Dutch factors and the construct validity of the corresponding dimensions. It also set out to develop norms for a nationwide sample of US students. The results provide further support for the reliability, factorial and construct validity of the SIB. Compared to their Dutch equivalents, US students had meaningfully higher distress in assertiveness scores on all SIB scales (medium to large effect sizes), whereas differences on the performance scales reflected small effect sizes. The cross-national differences in distress scores were hypothesized to have originated from the American culture being more socially demanding with respect to interpersonal competence than the Dutch, and from the perceived threats and related cognitive appraisals that are associated with such demands.

Chloramphenicol-induced mitochondrial dysfunction is associated with decreased transferrin receptor expression and ferritin synthesis in K562 cells and is unrelated to IRE-IRP interactions.

Chloramphenicol is an antibiotic that consistently suppresses the bone marrow and induces sideroblastic anemia. It is also a rare cause of aplastic anemia. These toxicities are thought to be related to mitochondrial dysfunction, since chloramphenicol inhibits mitochondrial protein synthesis. We hypothesized that chloramphenicol-induced mitochondrial impairment alters the synthesis of ferritin and the transferrin receptor. After treating K562 erythroleukemia cells with a therapeutic dose of chloramphenicol (10 microg/ml) for 4 days, there was a marked decrease in cell surface transferrin receptor expression and de novo ferritin synthesis associated with significant decreases in cytochrome c oxidase activity, ATP levels, respiratory activity, and cell growth. Decreases in the transferrin receptor and ferritin were associated with reduced and unchanged message levels, respectively. The mechanism by which mitochondrial dysfunction alters these important proteins in iron homeostasis is not clear. A global decrease in synthetic processes seems unlikely, since the expression of the cellular adhesion proteins VLA4 and CD58 was not significantly decreased by chloramphenicol, nor were the message levels of beta-actin or ferritin. The alterations were not accompanied by changes in binding of the iron response protein (IRP) to the iron-responsive element (IRE), although cytosolic aconitase activity was reduced by 27% in chloramphenicol-treated cells. A disturbance in iron homeostasis due to alterations in the transferrin receptor and ferritin may explain the hypochromic-microcytic anemia and the accumulation of nonferritin iron in the mitochondria in some individuals after chloramphenicol therapy. Also, these studies provide evidence of a link between mitochondrial impairment and iron metabolism in K562 cells.

Hypoxia alters iron-regulatory protein-1 binding capacity and modulates cellular iron homeostasis in human hepatoma and erythroleukemia cells.

Ferritin and transferrin receptor expression is post-transcriptionally regulated by a conserved mRNA sequence termed the iron-responsive element (IRE), to which a transacting protein called the iron-regulatory protein (IRP) is bound. Our data demonstrate that hypoxia powerfully enhances IRE/IRP-1 binding in human cell lines. Using the human hepatoma cell line Hep3B as a model, we found that 16 h in a 1% oxygen atmosphere markedly increases IRE/IRP-1 binding as assessed by electromobility shift assay. Hypoxia also decreased cytosolic aconitase activity. The hypoxia-enhanced IRE/IRP-1 binding stabilized the transferrin receptor message, increased the cellular mRNA content by over 10-fold, and doubled surface receptor expression. Simultaneously, hypoxia suppressed ferritin message translation. Hypoxia's effect was most strikingly depicted by the absence of ferritin synthesis in cells challenged with inorganic iron. Our results contrast with previously reported data (Hanson, E. S., and Leibold, E. A. (1998) J. Biol. Chem. 273, 7588-7593) in which a 3% oxygen atmosphere reduced IRE/IRP-1 binding in rat hepatoma cells. We discuss some possible reasons for the differences. In aggregate with other investigations involving responses to hypoxia, iron, or nitric oxide, our data indicate that cellular iron metabolic responses are complex and that IRE/IRP-1 interactions vary between cell lines and perhaps between species.

Low concentrations of nitric oxide increase oxygen affinity of sickle erythrocytes in vitro and in vivo.

The hallmark of sickle cell disease (SCD) is the polymerization of deoxygenated sickle hemoglobin (HbS). In SCD patients, one strategy to reduce red blood cell (RBC) sickling is to increase HbS oxygen affinity. Our objective was to determine if low concentrations of nitric oxide (NO) gas would augment the oxygen affinity of RBCs containing homozygous HbS (SS). Blood containing normal adult hemoglobin (AA) or SS RBCs was incubated in vitro in the presence of varying concentrations of NO up to 80 ppm, and oxygen dissociation curves (ODCs) were measured. In addition, blood was obtained from three AA and nine SS volunteers, before and after breathing 80 ppm NO in air for 45 min, and the ODCs were measured. Exposure of SS RBCs to 80 ppm NO in vitro for 5 min or longer decreased the partial pressure of oxygen at which hemoglobin is 50% saturated with oxygen (P50), an average of 15% (4.8+/-1.7 mmHg mean+/-SE; P < 0.001). The increase in SS RBC oxygen affinity correlated with the NO concentration. The P50 of AA RBCs was unchanged (P > 0.1) by 80 ppm NO. In SS volunteers breathing 80 ppm NO for 45 min, the P50 decreased (P < 0.001) by 4.6+/-2.0 mmHg. 60 min after NO breathing was discontinued, the RBC P50 remained decreased in five of seven volunteers in whom the ODC was measured. There was no RBC P50 change (P > 0.1) in AA volunteers breathing NO. Methemoglobin (Mhb) remained low in all subjects breathing NO (SS Mhb 1.4+/-0.5%), and there was no correlation (r = 0.02) between the reduction in P50 and the change in Mhb. Thus, low concentrations of NO augment the oxygen affinity of sickle erythrocytes in vitro and in vivo without significant Mhb production. These results suggest that low concentrations of NO gas may offer an attractive new therapeutic model for the treatment of SCD.

A multiparameter analysis of sickle erythrocytes in patients undergoing hydroxyurea therapy.

During 24 weeks of hydroxyurea treatment, we monitored red blood cell (RBC) parameters in three patients with sickle cell disease, including F-cell and F-reticulocyte profiles, distributions of delay times for intracellular polymerization, sickle erythrocyte adherence to human umbilical vein endothelial cells in a laminar flow chamber, RBC phthalate density profiles, mean corpuscular hemoglobin concentration and cation content, reticulocyte mean corpuscular hemoglobin concentration, 1H-nuclear magnetic resonance transverse relaxation rates of packed RBCs, and plasma membrane lateral and rotational mobilities of band 3 and glycophorins. Hydroxyurea increases the fraction of cells with sufficiently long delay times to escape the microcirculation before polymerization begins. Furthermore, high pretreatment adherence to human umbilical vein endothelial cells of sickle RBCs decreased to normal after only 2 weeks of hydroxyurea treatment, preceding the increase in fetal hemoglobin levels. The lower adhesion of sickle RBCs to endothelium would facilitate escape from the microcirculation before polymerization begins. Hydroxyurea shifted several biochemical and biophysical parameters of sickle erythrocytes toward values observed with hemoglobin SC disease, suggesting that hydroxyurea moderates sickle cell disease toward the milder, but still clinically significant, hemoglobin SC disease. The 50% reduction in sickle crises documented in the Multicenter Study of Hydroxyurea in Sickle Cell Disease is consistent with this degree of erythrocyte improvement.

ATP depletion causes translational immobilization of cell surface transferrin receptors in K562 cells.

We have used quantitative fluorescence microscopy and fluorescence photobleaching recovery to examine the role of metabolic energy in the translational movement of transferrin receptors in the plasma membrane of K562 erythroleukemia cells. Cellular ATP depletion caused a significant decrease in the translational mobility of cell surface transferrin receptors and a significant increase in the number of receptors on the cell surface. ATP repletion restored receptor translational mobility and cell surface expression to control values. Inhibition of ATP hydrolases by orthovanadate also immobilized cell surface transferrin receptors and altered cell surface receptor expression, in a concentration-dependent manner. Vanadate-induced changes in receptor mobility and cell surface expression were reversible upon washing out the drug. Cellular ATP depletion did not affect the translational mobility of plasma membrane glycophorins or a fluorescent phospholipid analogue. We conclude that the translational movement of cell surface transferrin receptors specifically requires metabolic energy and ATP hydrolysis.

Adhesion of sickle neutrophils and erythrocytes to fibronectin.

The pathophysiology of vaso-occlusive crisis in sickle cell disease involves interactions among blood cells, plasma proteins, and vessel wall components. The initial goal of this work was to quantify the adhesion of sickle red blood cells (RBCs) to fibronectin immobilized on glass under both static and dynamic shear stress conditions. High-power microscopic inspection of static assay plates showed striking numbers of adherent neutrophils as well as RBCs. Sickle neutrophils and RBCs were significantly more adherent to fibronectin than the corresponding normal cells in static adhesion assays. Adhesion of both sickle neutrophils and sickle RBCs in dynamic adhesion assays was promoted by a period of static incubation preceding initiation of shear stress conditions. Adherent neutrophils remained attached at shear stresses up to 51 dyne/cm2; most adherent RBCs were attached at shear stresses up to 13 dyne/cm2, but detached at a shear stress of 20 dyne/cm2. Sickle neutrophil adhesion was enhanced significantly by autologous plasma. Elevated levels of plasma interleukin-6 (IL-6; but not IL-1 or IL-8) were found in 6 of 9 sickle cell disease samples examined, and elevated levels of tumor necrosis factor were found in 2 of 9 samples. Plasma IL-6 levels correlated positively with both the number of sickle neutrophils adherent to fibronectin and the ability of sickle plasma to enhance adhesion of normal neutrophils to fibronectin. These data suggest possible roles for neutrophil activation and for fibronectin in mediating sickle neutrophil and RBC adhesion.

Ascorbic acid enhances ferritin mRNA translation by an IRP/aconitase switch.

Replenishment of ascorbate in cultured cells, which are almost uniformly vitamin-deficient, increases ferritin mRNA translation in response to iron by 20-fold (Toth, I., Rogers, J. T., McPhee, J. A., Elliott, S. M., Abramson, S. L., and Bridges, K. R. (1995) J. Biol. Chem. 270, 2846-2852). We now demonstrate that ascorbate increases cytosolic aconitase activity. The iron-responsive element-binding protein (IRP-1) exists in three states: bound to mRNA without aconitase activity, free in the cytosol without aconitase activity, and free in the cytosol with aconitase activity. Ascorbate converts free IRP-1 to the enzymatically active form. Enhanced ferritin synthesis with subsequent iron stimulation is due to the altered equilibrium of the free IRP-1. The cellular biology of iron is closely intertwined with that of ascorbate.

Ascorbic acid enhances iron-induced ferritin translation in human leukemia and hepatoma cells.

Ascorbate is an important cofactor in many cellular metabolic reactions and is intimately linked to iron homeostasis. Continuously cultured cells are ascorbate deficient due to the lability of the vitamin in solution and to the fact that daily supplementation of media with ascorbate is unusual. We found that ascorbate repletion alone did not alter ferritin synthesis. However, ascorbate-replete human hepatoma cells, Hep3B and HepG2, as well as K562 human leukemia cells achieved a substantially higher cellular ferritin content in response to a challenge with iron than did their ascorbate-deficient counterparts grown under standard culture conditions. Most of the elevation in ferritin content was due to an increase in de novo ferritin synthesis of greater than 50-fold, as shown by in vivo labeling with [35S]methionine and immunoprecipitation. RNA-blot analysis showed only minor changes in steady state levels of ferritin mRNA, suggesting that ascorbate enhances iron-induced ferritin synthesis primarily by post-transcriptional events. Transient gene expression experiments using chloramphenicol acetyltransferase reporter gene constructs showed that the ascorbate effect on ferritin translation is not mediated through the stem-loop near the translational start site that transduces ferritin synthesis in response to cytokines. The data suggest that ascorbate possibly modifies the action of the iron-responsive element on ferritin translation, although more precise structure-function studies are needed to clarify this issue. These data demonstrate a novel role of ascorbate as a signaling molecule in post-transcriptional gene regulation. The mechanism by which ascorbate modulates cellular iron metabolism is complex and requires additional detailed investigation.

Microtubule inhibitors differentially affect translational movement, cell surface expression, and endocytosis of transferrin receptors in K562 cells.

We used quantitative fluorescence microscopy and fluorescence photobleaching recovery techniques to investigate the translational movement, cell surface expression, and endocytosis of transferrin receptors in K562 human erythroleukemia cells. Receptors were labeled with fluorescein-conjugated transferrin (FITC-Tf). Coordinated decreases in surface fluorescence counts, the photobleaching parameter K, and transferrin receptor fractional mobility were observed as FITC-Tf was cleared from the cell surface by receptor-mediated endocytosis. Based on the kinetics of decrease in these parameters, first order rate constants for FITC-Tf uptake at 37 degrees C and 21 degrees C were calculated to be 0.10-0.15 min-1 and 0.02-0.03 min, respectively. K562 cells were treated with colchicine or vinblastine to investigate the role of microtubules in transferrin receptor movement and endocytosis. Treatment of cells for 1 hr with a microtubule inhibitor prevented transferrin receptor endocytosis but had no effect on the translational mobility of cell surface receptors. In contrast, drug treatment for 3 hr caused translational immobilization of cell surface receptors as well as inhibition of endocytosis. These effects were not produced by beta-lumicolchicine, an inactive colchicine analog, or by cytochalasin, a microfilament inhibitor. The effect of microtubule inhibitors on transferrin receptor mobility was reversed by pretreating cells with taxol, a microtubule-stabilizing agent. Microtubule inhibitors had no effect on the translational mobility of cell surface glycophorins or phospholipids, indicating that intact microtubules were not required for translational movement of these molecules. We conclude that the translational movement of cell surface transferrin receptors is directed by a subpopulation of relatively drug-resistant microtubules. In contrast, transferrin receptor endocytosis depends on a subpopulation of microtubules that is relatively sensitive to the action of inhibitors. These results appear to demonstrate at least two functional roles for microtubules in receptor-mediated transferrin uptake in K562 cells.

Translational enhancement of H-ferritin mRNA by interleukin-1 beta acts through 5' leader sequences distinct from the iron responsive element.

Interleukin-1 beta (Il-1 beta), a key cytokine in the acute phase response, elevates hepatic expression of both the heavy (H) and light (L) ferritin subunits without influencing the steady-state levels of either ferritin transcript. Transfection experiments with human hepatoma cells reveal that sequences within the 5' untranslated region (5'UTR) of H-ferritin mRNA confer translational regulation to chimaeric chloramphenicol acetyl transferase (CAT) mRNAs in response to Il-1 beta in the absence of marked changes in CAT mRNA levels. Il-1 beta dependent translational enhancement is mediated by a distinct G + C rich RNA sequence within 70 nucleotides (nt) of the start codon. The upstream Iron Responsive Element RNA stemloop does not confer increased expression to CAT mRNA in Il-1 beta stimulated hepatoma transfectants. A 38 nucleotide consensus sequence within the 5'UTRs of the mRNAs encoding the hepatic acute phase proteins alpha 1-antitrypsin (alpha 1AT), alpha 1-acid glycoprotein (AGP) and haptoglobin (Dente et al., 1985) is similar to sequences in the G + C rich H-ferritin mRNA translational regulatory element. Deletion of three nucleotides from this region of the 61 nt G + C rich element in the H-ferritin mRNA 5' leader eliminates Il-1 beta translational enhancement of the CAT reporter transcripts.

Ascorbic acid and iron metabolism: alterations in lysosomal function.

Iron is essential to cell metabolism but promotes free radical damage to membranes and lipids. Therefore, excess intracellular iron is stored within the shell of hollow ferritin molecules until needed for metabolic use. Ascorbate retards ferritin degradation and increases iron bioavailability. The vitamin stabilizes the iron cores of ferritin in cells prelabeled with 59Fe. [35S]Methionine labeling demonstrates that this enhanced stability of the iron cores results from delayed degradation of the ferritin shells. Subcellular fractionation of 59Fe-labeled cells by use of a Sepharose CL-6B column shows that ascorbate significantly delays the shift of ferritin label from the cytosolic to the lysosomal compartment. Monomeric ferritin shells in the cytoplasm gradually form clusters that bind to lysosomes. Single ferritin shells do not. Ascorbate does not affect the conversion of cytoplasmic ferritin monomers to clusters but greatly retards the autophagic uptake of ferritin clusters into lysosomes.

Translational control during the acute phase response. Ferritin synthesis in response to interleukin-1.

Interleukin-1 (IL-1 beta) increases the synthesis of both heavy and light (L)-ferritin subunits when added to human hepatoma cells (HepG2) grown in culture. RNase protection and Northern blot analysis with L-ferritin probes revealed that no changes in L-ferritin mRNA levels occur after cytokine stimulation. However, the induction coincides with an increased association of the L-subunit mRNA with polyribosomes. Since the recruitment of stored ferritin mRNA onto polyribosomes is seen when iron enters the cell, the effect of IL-1 beta on iron uptake was tested and was found to be unaffected by the lymphokine. Neither transferrin receptor mRNA levels nor the number of receptors displayed on the cell surface was affected by IL-1 beta. However, the action of the cytokine on ferritin translation is inhibited by the action of the intracellular iron chelator deferoxamine. These data indicate that IL-1 beta induces ferritin gene expression by translational control of its mRNA. The pathway of induction is different from iron-dependent ferritin gene expression whereas regulation requires the background presence of cellular iron.

Ascorbic acid inhibits lysosomal autophagy of ferritin.

Ascorbic acid retards ferritin degradation in K562 erythroleukemia cells leading to an increase in the availability of cellular iron (Bridges, K. R., and Hoffman, K. E. (1986) J. Biol. Chem. 261, 14273-14277). To explore the mechanism of this effect, the influence of ascorbate on subcellular ferritin distribution was examined. Cellular ferritin was pulse-labeled with 59Fe for 2 h, after which the cells were hypotonically lysed and fractionated on an 8% Percoll density gradient. Immediately after the labeling, all of the ferritin was in the cytoplasmic fractions at the top of the gradient. When the labeling was followed by a 24-h period of growth, a portion of the ferritin shifted to the lysosome-associated fractions at the bottom of the gradient, consistent with lysosomal autophagy of cytoplasmic ferritin. When ascorbate was added to the culture medium during the 24-h incubation, the magnitude of the shift was reduced. This process was also examined by size-fractionation of the contents of labeled cells using a Sepharose CL-6B column. Immediately after labeling, ferritin emerged from the column in two peaks, indicating the existence of both ferritin monomer and aggregates within the cytoplasm. After a 24-h period of growth, the monomer peak disappeared, while a new ferritin peak coincident with lysosomes emerged again, indicative of lysosomal autophagy of ferritin. In cells cultured with ascorbate for 24-h, there was a marked attenuation of the shift of ferritin to the lysosomal fractions. The monomer peak disappeared, as in the controls, but there was instead, an accumulation of ferritin as cytoplasmic aggregates. The total ferritin content of the ascorbate-treated cells was increased by 4-fold over that of the control. These experiments indicate that ascorbate blocks the degradation of cytoplasmic ferritin by reducing lysosomal autophagy of the protein. The access to the cell of the potentially toxic iron stored within the ferritin molecule is thereby increased.

The effects of ascorbic acid on the intracellular metabolism of iron and ferritin.

An important property of ascorbic acid is its ability to increase the availability of storage iron to chelators. To examine the mechanism of this effect, K562 cells were incubated with ascorbate, attaining an intracellular level of 1 nmol/10(7) cells. In contrast to the reductive mobilization of iron seen with isolated ferritin, ascorbate stabilized iron preincorporated into cellular ferritin. Biosynthetic labeling with [35S]methionine demonstrated that ascorbate also retarded the degradation of the ferritin protein shell. Ferritin is normally degraded in lysosomes. The lysosomal protease inhibitors leupeptin and chloroquine produced a qualitatively similar stabilization of ferritin. Ascorbate did not act as a general inhibitor of proteolysis, however, since it did not effect hemoglobin degradation in these cells. The stabilization of cellular ferritin by ascorbate was accompanied by an expansion of the pool of chelatable iron.

The influence of both drinking and familial risk statuses on cognitive functioning of social drinkers.

Problem and nonproblem drinking, college student sons of alcoholics were compared to problem and nonproblem drinking college student sons of nonalcoholic fathers with respect to cognitive functioning. Problem drinkers performed more poorly on two of the four cognitive tasks, Group Embedded Figures and Symbol-Digit Paired Associates Learning Task, thus supporting earlier findings of cognitive deficits in problem drinking nonalcoholics. Additionally, sons of alcoholics tended to perform more poorly than sons of nonalcoholics on the Group Embedded Figures Test. Cognitive performance was not predicted by any of four measures of impulsive/antisocial personality and behavior-preadult antisocial behavior, childhood behavior problems, sensation seeking, and the MacAndrew Alcoholism Scale. The findings of the research pointed to the importance of considering both drinking and familial alcoholism risk statuses in studies of the cognitive performance of nonalcoholics. Further implications and limitations of the findings are discussed.