Physiological deactivation after two contrasting tasks at a video display terminal: learning vs repetitive data entry

Two contrasting 90 min VDT work situations were simulated in the laboratory: (1) a machine-paced, repetitive data entry task; and (2) a stimulating, self-paced learning task with successive feedback. Thirty non-smoking male students (20-34 years), without previous experience of VDT work, participated individually in each condition on two consecutive days (balanced order) and in a task-free baseline condition. Self-reports and successive measurements (ambulatory recordings) of systolic and diastolic blood pressure and heart rate were obtained during work and during a subsequent 60 min period of deactivation. Urine samples were obtained after each period for the determination of catecholamines and cortisol. In the baseline condition, measurements were obtained at corresponding times of the day. As expected, the data entry task was associated with self-reports of boredom, irritation, and unpleasantness; the learning task wtih alertness, interest, and ability to concentrate. Similar elevations of physiological measurements occurred in both work situations. However, differences between conditions were found after work. Following data entry, deactivation was slower in five of the six variables (significant for epinephrine).

Co-existing structures of an mRNA stability determinant. The 5' region of the Escherichia coli and Serratia marcescens ompA mRNA

The structure of untranslated regions of mRNA is thought to play a key role in the degradation of mRNAs by specific RNases. As a model system, in vitro transcripts of the stability determining 5' non-coding region of bacterial ompA mRNA were investigated by calculation of secondary structure models and by experiments applying the temperature-gradient gel electrophoresis (TGGE). For the theoretical prediction of secondary structures an algorithm was used, which yields the structure of lowest free energy as well as a large set of suboptimal structures. Three structures were predicted to co-exist in similar concentrations under native conditions. They denature in a low temperature transition leading to a unique structure which denatures in a high temperature transition. The prediction of three structures and two transitions could be confirmed experimentally by TGGE. Due to the use of transcripts of different length the conformational transitions could be attributed to distinct parts of the molecules. A pseudoknot structural motif was predicted theoretically, but could not be confirmed experimentally. Comparing ompA transcripts of E. coli and S. marcescens, a conservation of structural features could be shown in spite of a sequence homology of only 63%. Regarding the sequential folding of the transcript after synthesis, a metastable structure is formed first and is converted slowly into structures of lower free energy. The biological implications for in vivo degradation are discussed.

Functional interaction of heat shock protein GroEL with an RNase E-like activity in Escherichia coli

The highly specific endoribonuclease activities of RNase E (which processes ribosomal 9S RNA into p5S RNA) and RNase K (which initiates decay of the ompA mRNA) are inferred to play a central role in RNA processing and mRNA decay in Escherichia coli. In vivo both activities are affected by a conditional mutation of the ams/rne gene that seems to be complemented at nonpermissive temperatures by a fragment of the groEL gene. Analysis of the relationship between the two nucleases and the heat shock protein revealed that GroEL interacts functionally with an RNase E-like activity but not with an RNase K activity, a groEL mutation affected 9S RNA processing but not ompA mRNA cleavage, RNase E activity could be precipitated with an antibody against GroEL, and a highly purified GroEL preparation contained RNase E activity but not RNase K activity. When purifying RNase E activity, we obtained a preparation containing two major proteins of 60 and 17 kDa. The size and the N-terminal sequence identified the 60-kDa protein as GroEL.

Physiological reactivity and Type A behavior in preschool children: a longitudinal study

Measurements of Type A behavior were related to cardiovascular (systolic and diastolic blood pressure, heart rate) and neuroendocrine (urinary catecholamines and cortisol) reactivity in 30 male and 30 female preschool children during various active conditions at their mean ages of 3.5, 4.5, 5.5, and 6.5. Significant elevations of physiological arousal occurred in most active conditions and for all physiological variables except cortisol. Playgroup leaders in daycare centers filled out a Swedish version of the scale measuring Type A behavior, and boys obtained significantly higher scores than girls. Whereas Type A scores were relatively consistent over time, however, physiological reactivity was not a stable individual characteristic, and correlations between Type A scores and cardiovascular reactivity reached significance in only 4 of 33 tests for the boys (one negative correlation) and in 1 case for the girls. Correlations between Type A scores and catecholamine reactivity did not reach significance. In summary, the data do not support the assumption of a consistent relationship between Type A behavior and physiological reactivity in preschool children. A significant correlation (r = .57, p less than .01) found for boys during a computer game suggests that an association may exist during "Type A-relevant" challenge.

Comparison of neuroendocrine measurements under laboratory and naturalistic conditions

Urinary catecholamines and cortisol were measured in healthy nonsmoking white collar workers (14 male and 15 female managers, 15 male and 14 female clerical workers), aged 30-50 years, during a one-hour period of laboratory-induced stress comprising five tests and a Type A interview, and during a subsequent period of rest in the laboratory. Values were compared with data obtained four months earlier from the same subjects during a normal day at work (4 values) and during a work-free day at home (4 values). No significant group differences were found during rest in the laboratory. However, during laboratory-induced stress, female managers had the highest norepinephrine values, which contributed to significantly (p less than 0.01) higher values in women than in men. Correlations between absolute measurements from laboratory and naturalistic conditions were generally positive and reached significance in most cases. Correlations between reactivity measurements in the laboratory and at work (change from rest to stress and from home to work, respectively) were generally low, whereas correlations between reactivity at different times of the day were relatively high. The data suggest that generalizability of neuroendocrine reactivity from laboratory stress to real-life stress is low. However, in agreement with earlier experimental findings, absolute levels of catecholamine and cortisol excretion were consistent over conditions and time.

Steroid sex hormones and cardiovascular function in healthy males and females: a correlational study

The relationship of serum estradiol and testosterone levels to systolic (SBP) and diastolic blood pressure (DBP) and heart rate (HR) was examined in healthy nonsmoking males (n = 30) and females (n = 22), 30-50 years of age (mean age for men = 41.2, women = 39.9). Postmenopausal women and women taking oral contraceptives had been excluded. Testosterone levels in women were positively correlated with SBP, DBP and HR, after removing the effects of age and body mass. Positive correlations were also found between estradiol and SBP and HR in women. No systematic relationships were found between steroid sex hormones and cardiovascular measurements in men. The findings suggest a role of steroid sex hormones in cardiovascular function of women, whereas the relationship in men is less clear.

Cleavages in the 5′ region of the ompA and bla mRNA control stability: studies with an E. coli mutant altering mRNA stability and a novel endoribonuclease

We describe here the partial purification of a novel Escherichia coli endoribonuclease, RNase K. This protein catalyses site-specific cleavages in the 5' region of in vitro transcribed ompA and bla transcripts. Some of the resulting cleavage products are also found in cellular ompA mRNA, defining the in vivo activity of RNase K. The following evidence suggests that RNase K initiates mRNA degradation. First, RNase K cleavages are suppressed in the ams mutant, which has a generally prolonged mRNA half-life. Secondly, RNase K cleavage products seem to have very short half-lives in vivo, indicating that they are decay intermediates rather than processing products. Thirdly, the differences in in vivo half-life between the ompA and bla mRNAs are mimicked in in vitro decay reactions with purified RNase K. The relationship between RNase K and the ams locus might point to a more general role of RNase K in mRNA degradation. We discuss the influence of mRNA secondary structure on RNase K cleavage specificity.

The loads on the lumbar spine during work at an assembly line. The risks for fatigue injuries of vertebral bodies

This study was performed in an attempt to determine the total spinal compressive load during assembly line work to find a possible association with the many complaints of back pain. A flexion analyzer was used to register trunk movements, and analysis of postures and lifted weights was done from video recordings. The load on the spine at the L3 level was calculated through a biomechanical model, meant for analysis of static, sagittally symmetric postures and lifting tasks. Maximum lift tests were performed before and after a full work day. The peak load on the L3-L4 level when lifting corresponded to an average 22% of the load at the lift test. The mean load during a work cycle was 818 N. It was concluded that the many complaints of back pain could not be attributed to high peak loads, repetitivity of the lifts, or large load doses. Monotony, stress, and low job satisfaction are more likely factors of greater importance.

Type A behaviour in pre-school children: interrater reliability, stability over six months and subcomponents

Type A behaviour was measured in 250 boys and 245 girls (ages 3-7) using a Swedish version of Matthews' Youth Test for Health (MYTH). In addition, speech and voice characteristics (speed, loudness, response latency) were measured. Each child was independently rated by two play group leaders and measurements were repeated after a six month interval. Interrater reliability (first session) was 0.76 for both sexes and did not change with the age of the child. Boys obtained significantly (p less than 0.0001) higher scores than girls. Correlations over the six month period were 0.64 and 0.60 (p less than 0.001) for the two possible combinations of different raters and slightly higher (0.75 and 0.68, p less than 0.001) when the same rater was used. Two components of Type A behaviour were identified from a factor analysis of the data: impatience and competitiveness, and they accounted for 57% of the total variance. As for the total scale, boys obtained significantly higher scores than girls on both subscales. Scores on the competitiveness scale increased systematically with age. Speech and voice characteristics correlated significantly with Type A scores (total Type A behaviour: r = 0.50, using different raters, and 0.71, using the same raters, p less than 0.001) and, once again, boys obtained significantly (p less than 0.001) higher scores than girls. The results are in close agreement with the American findings from the original scale. It was concluded that the scale provides a reliable and valid instrument for measuring Type A or Type A-like behaviours in pre-school children.

Familial similarity in Type A behaviour and physiological measurements as related to sex

Thirty-one families with pre-school children were examined with regard to Type A behaviour and cardiovascular and neuroendocrine measurements. Type A scores (MYTH) of the children from the ages of three to six were positively correlated with independent Type A measurements (Jenkins Activity Survey, Bortner Type A scale) of the parents (significant for fathers but not for mothers). The children's resting systolic blood pressures were significantly correlated with maternal and paternal values, while no significant familial aggregation was found for diastolic blood pressure, heart rate, catecholamine or cortisol excretion. The children's systolic and diastolic blood pressures and adrenaline excretion were significantly correlated between ages three and six. The results are consistent with the assumption that genetic as well as environmental factors contribute to the development of Type A behaviour. No significant association was found between Type A scores and physiological measurements during routine activities in the children or the adults.

Blood pressure in healthy men and women under laboratory and naturalistic conditions

Thirty healthy nonsmoking men and 30 women underwent a laboratory reactivity assessment with systolic (SBP) and diastolic blood pressure (DBP), and heart rate (HR) recorded at rest and during behavioral (mirror image tracing, mental arithmetic, color word conflict task and a semistructured Type A interview), and physical tasks (isometric exercise and the cold pressor test). Causal SBP and DBP were measured in a physician's clinic. Four months earlier SBP, DBP and HR had been monitored during a day at work and a day at home. Readings obtained in the clinic, at rest and during stress in the laboratory were related to real-life levels, reactivity (work-home difference) and variability. For men level of cardiovascular activation at rest and during all stressors in the laboratory correlated with levels at work and at home. The best laboratory/real-life relation was observed for SBP. Systolic blood pressure levels during stress correlated with the work-home difference. Systolic blood pressure reactivity (laboratory stress levels - rest levels) to most behavioral tasks correlated with SBP levels at work and home. Daily variability and reactivity correlated with SBP reactivity to mental arithmetic and the color word conflict task. For women, levels of SBP and HR at rest and during all stressors correlated with SBP and HR at work and at home. The best laboratory/real-life relation for women was observed for HR reactivity. Casual BP in the clinic correlated with work blood pressure but generally not with daily reactivity or variability. We conclude that BP and HR levels measured in the laboratory generalizes to real life BP and HR in both men and women and also to real life SBP reactivity in men. Laboratory induced SBP reactivity also shows a weak relation to real life SBP levels, variability and reactivity in men.

Cardiovascular reactivity to the cold pressor test as a predictor of hypertension

Cardiovascular reactivity to stress is hypothesized to be a marker for subsequent neurogenic cardiovascular disease, but few prospective studies of this hypothesis are available. We studied 910 white male medical students who had their blood pressure and pulse rate measured before and during a cold pressor test in the years 1948-1964. Hypertensive status (requiring drug treatment) was ascertained by annual questionnaires in the 20- to 36-year follow-up period. An association was observed between maximum change in systolic blood pressure and later hypertension, with a cumulative incidence of hypertension by age 44 of 6.7%, 3.0%, and 2.4% for a change in systolic blood pressure in the upper, middle two, and lowest quartiles, respectively (Kaplan-Meier, p less than 0.02). After adjustment for study entry age, Quetelet Index, cigarette smoking, pretest systolic blood pressure, and paternal or maternal history of hypertension in a Cox model, the association persisted. The excess risk associated with systolic blood pressure reactivity was not apparent until the population aged some 20 years and was most apparent among those in whom hypertension developed before age 45 (relative risk = 2.5, 95% confidence intervals = 1.47, 4.71 for a 20 mm Hg change). Diastolic blood pressure and heart rate changes were not associated with later hypertension. These data suggest that persons prone to later hypertension manifest an altered physiology at a young age.

Catecholamine measurements in urine by high-performance liquid chromatography with amperometric detection--comparison with an autoanalyser fluorescence method

In order to validate different methods of measuring urinary catecholamines (norepinephrine, epinephrine and dopamine) in humans, methods based on separation of catecholamines using reversed-phase or cation-exchange high-performance liquid chromatography with electrochemical detection were compared with an autoanalyser-based fluorescence method. Different methods for pre-chromatography sample purification were also studied. For measurements of urinary catecholamines, the reversed-phase-based chromatographic techniques studied were found to give less reliable results than cation-exchange chromatography, even if one of them (Clin Rep Urine Catecholamine Kit) gave almost as precise estimates. The autoanalyser technique yielded good results. It is concluded that cation-exchange chromatography with an appropriate sample work-up procedure (a combination of organic solvent extraction and alumina adsorption) is a reliable and accurate method for analyses of urinary catecholamines.

Blood lipids as related to cardiovascular and neuroendocrine functions under different conditions in healthy males and females

Correlations were calculated between, on the one hand, total serum cholesterol, low-density (LDL) and high-density (HDL) lipoprotein cholesterol, and triglycerides, and, on the other hand, systolic (SBP) and diastolic blood pressure (DBP), heart rate (HR), urinary epinephrine, norepinephrine, and cortisol in 30 healthy males and 30 healthy females, aged 30-50. The cardiovascular and neuroendocrine measurements were obtained under different real-life and laboratory conditions. The most striking finding was that, in men, but not in women, total serum cholesterol was significantly positively correlated with SBP in all conditions (LDL and HDL cholesterol followed the same pattern). In women, but not in men, epinephrine and norepinephrine during laboratory-induced mental stress were significantly positively correlated with total cholesterol, LDL and triglycerides.

Type A behavior in healthy males and females as related to physiological reactivity and blood lipids

Type A behavior was assessed in 30 men and 30 women (ages 30-50) by a Videotaped Structured Interview (VSI). Scores for total Type A behavior as well as subcomponents (competitiveness, time urgency, hostility) were examined in relation to cardiovascular and neuroendocrine reactivity during a work day (change from a work-free day) and during laboratory-induced stress (change from resting condition). In addition, Type A and Type B males and females were compared with regard to total serum cholesterol, LDL and HDL cholesterol, and triglycerides. The results showed relationships between 1) competitiveness/hostility and physiological reactivity at work in men, 2) total Type A behavior (and hostility) and serum cholesterol in men, and 3) hostility and serum cholesterol in women. As expected, the association between Type A behavior and physiological measurements was more pronounced for "extreme" Type A and B men and women (upper and lower 10 subjects, respectively) than for the total groups of each sex.

The differential stability of the Escherichia coli ompA and bla mRNA at various growth rates is not correlated to the efficiency of translation

Using two monocistronic gene transcripts, bla and ompA, we have studied the relationship between mRNA stability and translational efficiency. It was found that changes in the ompA mRNA stability are not correlated with an alteration in translational efficiency. In addition, at slow bacterial growth rates, the ompA transcript is translated ten times more efficiently than the bla messenger although the stability of the two transcripts is about equal. At rapid bacterial growth rate, chloramphenicol slightly stabilises both the bla and ompA transcripts without affecting their characteristic difference in half-life. Thus, control of mRNA stability seems not necessarily to be mediated either by the efficiency of loading ribosomes on a transcript, or by the arrest or slowing down of translating ribosomes.

Urinary catecholamines: comparison between HPLC with electrochemical detection and fluorophotometric assay

Comparisons between catecholamines determined by HPLC (with electrochemical detection) and fluorometry in urine samples from healthy adults and children, respectively, showed high correlations. In agreement with greater specificity for HPLC, mean values were higher for the fluorometric assay. However, it was concluded that fluorometric assays provide as valid and sensitive indices of stress-induced changes in catecholamine excretion in humans as HPLC.

In vivo and in vitro identity of site specific cleavages in the 5′ non-coding region of ompA and bla mRNA in Escherichia coli

The bla and ompA gene transcripts were used as substrates to probe Escherichia coli extracts for ribonucleolytic activities. A site specific endoribonucleolytic activity was identified that cleaves ompA and bla mRNA. The cleavages occur in vitro and in vivo. For both the bla and ompA mRNA most of the cleavage sites which were identified map in the 5' non-coding region. The cleavages of the ompA transcript have been previously suggested to regulate the growth rate dependent stability of this mRNA. Thus we propose that the identified endoribonucleolytic activity may be involved in the degradation of mRNA. Analysis of mutants revealed that the cleavages are mediated by endonucleases which do not seem to be identical to RNase III, RNase E or RNase P.

Effects of cadmium on canine renal cortical adenylate cyclase

The present studies examine the effects of cadmium (Cd2+) on adenylate cyclase activity in basolateral renal cortical membranes from normal dogs. Cd2+, in the dose range of 1 to 200 microM caused a dose-dependent inhibition of adenylate cyclase activity due to competitive inhibition with respect to the allosteric activator Mg2+ (increase in the Kact for Mg2+ from 13.8 to 37.2 mM). In addition, increasing Cd2+ concentrations from 0 to 25 microM resulted in a purely competitive inhibition with respect to ATP. The Km for ATP increased from 61 to 128 microM. When Mn2+ at a concentration of 20 mM was substituted for Mg2+, Cd2+ maintained its inhibitory effect at concentrations lower than 25 microM. At higher concentrations it stimulated enzyme activity in a dose-dependent fashion. In the absence of other divalent cations Cd2+ was a potent stimulator of basal adenylate cyclase activity, far more potent than the physiological activator of the system Mg2+. Kact for Cd2+ was 1.0 mM (Kact for Mg2+ 20 mM), whereas the Vmax showed a fourfold increase compared with the Mg2+-stimulated membranes. However, under these conditions, synthetic bovine parathyroid hormone (1-34) or 5'-guanylylimidodiphosphate did not stimulate adenylate cyclase. It is concluded that Cd2+ behaves as a partial agonist in this system, due to its ability to form a new enzymatic substrate complex: Cd-ATP, which competes with the physiological substrate Mg-ATP at the catalytic site of the enzyme. In addition, Cd2+ in the absence of other divalent cation stimulates basal enzyme activity, presumably through interaction at an additional site, closely related to the allosteric metal regulatory site of this enzyme system.

Urinary monoamine metabolites as indices of mental stress in healthy males and females

Concentrations of the serotonin metabolite 5-hydroxyindole acetic acid (5-HIAA), the dopamine metabolite homovanillic acid (HVA) and the noradrenaline metabolite 4-hydroxy-3-methoxyphenyl glycol (HMPG) were determined in urine samples from healthy male and female students by mass fragmentography. Urine samples were obtained after a demanding examination (mental stress) and a day of ordinary school work (control condition). Self-ratings were obtained of feelings induced by the examination, and of habitual psychosomatic symptoms. The results for both sexes showed that the examination stress induced a significant increase of HVA and HMPG excretion, but not of 5-HIAA. The males excreted significantly more of each of the metabolites than the females. The pattern of correlations between metabolite levels and psychological and psychosomatic variables were strikingly different for the two sexes.

Appearance of an arachidonic acid 15-lipoxygenase pathway upon differentiation of the human promyelocytic cell-line HL-60

The metabolism of arachidonic acid and 15-HPETE was studied in a human promyelocytic cell line (HL-60). Upon exposure to DMSO, HL-60 cells undergo differentiation and acquire a 15-lipoxygenase activity while undifferentiated cells challenged with either arachidonic acid or 15-HPETE did not enzymatically transform these precursors. Products of the arachidonic acid 15-lipoxygenase pathway were identified by HPLC. UV-absorption and gas chromatography-mass spectrometry. Results indicate that upon differentiation HL-60 cells express a 15-lipoxygenase activity as well as the ability to transform 15-HPETE to 8,15-DHETEs and 14,15-DHETE. Moreover, these findings suggest that products of the 15-lipoxygenase cascade may be generated by a single cell system.

Stereochemistry, total synthesis, and biological activity of 14,15-dihydroxy-5,8,10,12-eicosatetraenoic acid

The stereochemistry of the major isomer of 14,15-dihydroxy-5,8,10,12-eicosatetraenoic acid formed from 15-hydroperoxyeicosatetraenoic acid in human leukocytes was determined. The structure (erythro-14(R),15(S]-14,15-dihydroxy-5,8-cis-10,12-trans-eicosatetraenoi c acid) was assigned based on sodium arsenite thin-layer chromatography, NMR spectroscopy, and comparison with material prepared by total synthesis. This compound was found to inhibit leukotriene B4-induced superoxide anion generation in human neutrophils (IC50 = 10(-8)-10(-7) M). Superoxide anion generation induced by either formylmethionyl-leucyl-phenylalanine or arachidonic acid was not affected.

Inhibition of human natural killer cell activity by (14R,15S)-14,15-dihydroxy-5Z,8Z,10E,12E- icosatetraenoic acid

The interactions between products of the 15-lipoxygenase cascade and human natural killer (NK) cell activity have been studied. Addition of human leukocyte-derived (14R,15S)-14,15-dihydroxy-5Z,8Z,10E,12E-ic osatetraenoic acid (14,15-DiHETE) to the NK cytotoxicity assay against K562 target cells resulted in inhibition of NK cell activity, whereas addition of other 15-lipoxygenase-associated metabolites [i.e., (15S)-15-hydroperoxy-5Z,8Z,11Z,13E-icosatetra eno ic acid, (15S)-15-hydroxy-5Z,8Z,11Z,13E-icosatetraenoic acid, and (8R,15S)- and (8S,15S)-8,15-dihydroxy-5Z,9E,-11E,13E-icosat etr aenoic acid isomers] resulted in little or no inhibition of NK function. Dose-response studies indicate that leukocyte-derived 14,15-DiHETE and 14,15-DiHETE methyl ester, at micromolar concentrations, inhibit NK function even in the presence of 2.5% fetal calf serum. Synthetic 14,15-DiHETE prepared by total organic synthesis displayed similar biological activities over identical dose ranges. These icosanoids do not inhibit NK target cell binding and they exert only a variable effect in either antibody-dependent cytotoxicity or cytotoxic T-lymphocyte assays. These results demonstrate that the 14,15-DiHETE inhibits NK cell function in vitro. Moreover, they suggest that activation of the 15-lipoxygenase cascade and formation of 14,15-DiHETE in vivo may provide a mode of immune regulation.