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At least 127 records · Page 7Linked to original sources
PubMed2004

Low job control and myocardial infarction risk in the occupational categories of Kaunas men, Lithuania.

STUDY OBJECTIVE: To determine the association between adverse psychosocial characteristics at work and risk of first myocardial infarction in the occupational categories of Kaunas men, Lithuania. DESIGN: The analysis was based upon a case-control study among full time working men in the general population of Kaunas. OUTCOME MEASURE: First non-fatal myocardial infarction diagnosed in 2001-2002. The Swedish version of the demand-control questionnaire was used to examine the effect of job control and demands. SETTING: Kaunas, the second largest city in Lithuania, a former socialist country in a transition market economy. PARTICIPANTS: Cases were 203 men 25-64 years of age with a first non-fatal myocardial infarction and controls were 287 men group randomly selected from the study base. MAIN RESULTS: Low job control had a significant effect on myocardial infarction risk in the general 25-64 year old Kaunas male population (OR = 2.68; 95% CI 1.68 to 4.28) after adjustment for age and socioeconomic status. Low job control was a risk factor in the occupational categories of the increased myocardial infarction risk (1st occupational category--legislators, senior officials and managers and the 8th--plant and machine operators and assemblers; OR = 2.78; 95% CI 1.31 to 5.93 and 2.72; 95% CI 1.56 to 4.89, respectively, after adjustment for age and socioeconomic status). Though the adjusted odds ratio estimates were significantly high for the rest of the occupational categories (2nd--professionals, 3rd--technicians and associate professionals, and 7th--craft and related trades workers). CONCLUSIONS: The association between low job control and first myocardial infarction risk was significant for all occupational categories of Kaunas men.

Epidemiologic Factors↗
PubMed1985

Neural circuits in the flight system of the locust.

Circuitry in the flight system of the locust, Locusta migratoria, was investigated by use of intracellular recording and staining techniques. Neuronal connections were established by recording simultaneously from neuropile segments of pairs of identified interneurons. Brief depolarizing current pulses delivered to interneurons 301 and 501 reset the flight rhythm in a phase-dependent manner, thus establishing the importance of these neurons in rhythm generation. Interneuron 301 was found to make a strong delayed excitatory connection with 501 and to receive a short-latency inhibitory connection from 501. The circuit formed by 301 and 501 appears suited for promoting rhythmicity in the flight system. The delayed excitatory potential recorded in 501 following each spike of 301 was reversed by hyperpolarizing 501. This potential and short-latency inhibitory postsynaptic potentials from 301 to other interneurons were blocked with the application of picrotoxin. We conclude that the delayed excitation is produced via a disynaptic pathway from 301 to 501, with 301 inhibiting in a graded manner the tonic release of transmitter from one or more unidentified intercalated neurons. Interconnections between the 301-501 circuit and other identified interneurons were discovered. This circuitry can account for two features of the flight motor pattern recorded in deafferented preparations. These features are the constant-latency relationship between depolarizations in elevator and depressor motoneurons and the relatively constant duration of depressor motoneuron bursts. The locust flight system shares general features with other described rhythm-generating systems. These include the occurrence of graded interactions, the probability of multiple oscillatory mechanisms, and a predominance of inhibitory connections. Its uniqueness lies in the way that components and processes are assembled and operate.

Animals↗
PubMed1992

Respiratory-related neural assemblies in the brain stem midline.

1. The initial objective of this study was to determine whether respiratory-related neural assemblies exist in the brain stem midline. A second goal was to seek evidence for concurrent relationships among the neurons that could generate the detected synchrony. 2. Experiments were conducted on anesthetized, paralyzed, bilaterally vagotomized, artificially ventilated cats. Spike trains of four to nine simultaneously monitored neurons were recorded in the regions of n. raphe obscurus-n. raphe pallidus and n. raphe magnus. 3. Data were analyzed with cycle-triggered histograms, cross-correlograms, snowflakes, and the gravitational representation. A significance test for the gravity method was developed and tested with spike trains generated by simulated networks with defined connections. 4. Ninety-three groups of neurons from 24 cats were studied. Thirty-nine groups from 19 cats included neurons that discharged synchronously on a millisecond time scale; less than or equal to 19 pairs of synchronously discharging neurons were found in one group. Twenty-seven of these 39 groups included neurons that had respiratory-modulated firing rates and discharged synchronously with other group members. Synchronous assemblies included cells monitored at rostral or caudal locations, or both. 5. Six classes of relationships were inferred from groups of neurons with multiple correlations: divergence (n = 11); convergence (n = 7); connections with opposite actions between neurons (n = 5); projections of synchronous neurons to separate targets (n = 5); projections to one neuron in a synchronous group (n = 4); and projections between two synchronous groups with common elements (n = 6). 6. The results document the existence of assemblies of synchronously discharging respiratory-related neurons in midline regions of the brain stem and suggest that divergent excitatory and inhibitory connections within the midline participate in the generation of that synchrony. Links between assemblies may operate to stabilize their collective activity in a particular state.

Afferent Pathways↗
PubMed2006

Interfacing microchip capillary electrophoresis with electrospray ionization mass spectrometry.

Microfluidic devices are a unique enabling technology for chemical separations, modification, and synthesis that are ideally suited for the manipulation of low volume samples on the order of a few nanoliters in volume. Complex patterns of capillary-sized channels with zero dead volume connections are the distinguishing features of many microfluidic devices. Concurrently, mass spectrometry has undergone further development, and is now arguably the method of choice for structural characterization of mass- and volume-limited samples. The production of ions in the gas phase from the solution phase is critical for direct coupling of fluidic devices with the mass spectrometer, and the electrospray ionization (ESI) sources are well suited for this application. Micro- and nanoflow ESI interfaces are ideal for these applications as they cover flow rate ranges from the hundreds to a few nanoliters per minute, which are the same as the flow rates used by most microfluidic devices. Herein, the assembly and operation of a simple ESI interface for coupling a microfluidic device and mass spectrometer is described.

Electrophoresis, Microchip↗
PubMed2000

The effects of task complexity and experience on learning and forgetting: a field study.

This paper examines the effects of task complexity and experience on parameters of individual learning and forgetting. Three attributes of task complexity and experience are addressed: the method, machine, and material employed. The task involved a high-manual-dexterity skill taken from an operating textile assembly plant; there were 2853 individual participant learning/forgetting episodes. A parametric model of individual learning and forgetting that allows the evaluation of worker response to the attributes of task complexity and experience is discussed. Results indicate that both task complexity and experience significantly affect learning and forgetting rates. Potential applications of this research include the allocation of workers to tasks based on individual learning/forgetting characteristics.

Analysis of Variance↗
PubMed1998

Occupational injuries among older workers with disabilities: a prospective cohort study of the Health and Retirement Survey, 1992 to 1994.

OBJECTIVES: We tested the hypothesis that among older workers, disabilities in general, and hearing and visual impairments in particular, are risk factors for occupational injuries. METHODS: Using the first 2 interviews of the Health and Retirement Study, a nationally representative survey of Americans aged 51 to 61 years, we conducted a prospective cohort study of 5600 employed nonfarmers. RESULTS: Testing a logistic regression model developed in a previous cross-sectional study, we found that the following occupations and risk factors were associated with occupational injury as estimated by odds ratios: service personnel, odds ratio = 1.71 (95% confidence interval = 1.13, 2.57); mechanics and repairers, 3.47 (1.98, 6.10); operators and assemblers, 2.33 (1.51, 3.61); laborers, 3.16 (1.67, 5.98); jobs requiring heavy lifting, 2.05 (1.55, 2.70); self-employment, 0.50 (0.34, 0.73); and self-reported disability, 1.58 (1.14, 2.19). Replacing the general disability variable with specific hearing and visual impairment variables, we found that poor hearing (1.35 [0.95, 1.93]) and poor sight (1.45 [0.94, 2.22]) both had elevated odds ratios. CONCLUSIONS: Poor sight and poor hearing, as well as work disabilities in general, are associated with occupational injuries among older workers.

Accidents, Occupational↗
PubMed2006

Low-temperature inactivation of fecal coliforms in sludge digestion.

The goal of this research was to demonstrate the ability to achieve Class A pathogen standards in nonthermophilic acid digesters. It was proposed that the key mechanism responsible for fecal coliform inactivation was the presence of un-ionized volatile fatty acids. Lab-scale acid digesters were assembled and operated in a batch mode for 5 days at mesophilic (38 degrees C) and low-mesophilic (21 degrees C) temperatures and at different solids concentrations. The key factor recognized for successful pathogen inactivation was pH, which is also the main factor driving the shift in organic acids toward the un-ionized form. Compared to conventional mesophilic acid digestion, low-mesophilic acid digestion was effective in fecal coliform inactivation because the process maintained lower pH throughout the duration of the experiment, offered continuous release of organic acids, and showed higher concentrations of organic acids in un-ionized form, including acetate, propionate, butyrate, and valerate.

Acids↗
PubMed2002

Lifetime principal occupation and risk of cognitive impairment among the elderly.

We used a nested case-control design with study participants sampled from two cohorts, for a total of 2,198 elderly people 65 years or older and completed cognitive tests between 1993 and 1997, to assess the association between an individual's lifetime principal occupation and the subsequent risk of cognitive impairment. Cases consisted of 290 older adults with impaired cognitive functioning. For each case, two controls with comparable age (within 5 years) and sex frequencies were randomly sampled from the seniors free of cognitive impairment. Occupational data were collected through interviews. Individual's job content was coded into one of the occupational categories or the occupation-based social classes. Compared to those who were former legislators, government administrators, or business executives and managers, a significantly elevated risk of cognitive impairment was estimated for those who were employed as agriculture/animal husbandry/forestry/fishing workers (odds ratio (OR)=3.2), craft and related trades workers (OR=2.2), plant and machine operators and assemblers (OR=14.7), workers of elementary occupations (OR=3.2), or housekeepers (OR=2.6). We also observed health inequalities in the risk of cognitive impairment across social classes with a significant dose-response trend in which unskilled blue-collar workers had the highest risk. After adjustment for education, we still observed an inverse relationship between risk of cognitive impairment and occupational class. This may mean that lifetime longest-held occupation is more intimately involved in the causal pathways leading to cognitive impairment. Further studies that collect information on specific work hazards would help make specific interpretations of the observed effect of lifetime longest-held occupation in early adulthood on risk of cognitive decline in late life.

Aged↗
PubMed2002

A review of "chest tubes" during donor care and after transplantation.

Thoracostomy tubes, also called chest tubes, are commonly present after transplantation or during donor care. The function of the thoracostomy tube is to provide a conduit for transporting fluid, gas, or blood from the pleural cavity to an attached drainage unit. Malfunction of the tube or parts of the unit assembly may lead to serious consequences and jeopardize transplant recipient recovery or donor organs. This review discusses the components of the thoracostomy tube and drainage unit assembly, normal operation, routine evaluation, and common problems that the organ procurement or transplantation coordinator may need to anticipate or treat.

Chest Tubes↗
PubMedDate not supplied

[Features of the maintenance of automated developing machines].

Based on his long-term own experience the author gives recommendations on the assembly, adjustment, operation, and preventive maintenance of automatic developing machines. Procedures are presented for evaluating the quality of X-ray films and controlling the activity of operating qualities of a developer while machining photographic materials. Troubles and malfunction of equipment and procedures for their elimination are shown to affect the quality of development of films.

Automation↗
PubMed2001

Health problems among workers of iron welding machines: an effect of electromagnetic fields.

The possible effects of EMFs on 100 workers were studied by means of structured interview and rating of subjective symptoms. As control 41 sewing machine operators and assembly workers were chosen, interviewed and likewise tested. The present Indian ceiling value of 250 Tesla for the equivalent power density was exceeded in more than 50% of the machines. The highest leakage fields, for EMFs, were found near machines, which gave a high exposure to the hands. Eye irritation complaints were reported by 40% of the workers. The fertility outcome did not show any significant result.

Adult↗
PubMed1998

Overview of the Environmental Control and Life Support System (ECLSS) testing at MSFC.

Previously, almost all water used by the crew during space flight has been transported from earth or generated inflight as a by-product of fuel cells. Additionally, this water has been stored and used for relatively short periods. To achieve the United States' commitment to a permanent manned presence in space, more innovative techniques are demanded. Over 20,000 pounds of water and large quantities of air would have to be transported to the International Space Station (ISS) every 90 days with a corresponding amount of waste returned to earth, for an eight-person crew. This approach results in prohibitive logistics costs, and necessitates near complete recovery and recycling of water. The potential hazards associated with long-term reuse of reclaimed water and revitalized air resulted in the recognition that additional characterization of closed-loop systems and products is essential. Integrated physical/chemical systems have been designed, assembled, and operated to provide air and potable water meeting ISS quality specifications. The purpose of the Environmental Control and Life Support System (ECLSS) test program at NASA's Marshall Space Flight Center (MSFC) is to conduct testing related to the performance of the ISS and its Environmental Control components. The ECLSS Test Program encompasses the Water Recovery Test (WRT), the Integrated Air Revitalization Test (IART), and Life Testing, which permits ECLSS design evaluation. These subsystems revitalize air and reclaim waste waters representative of those to be generated on-orbit. This article provides an overview of MSFC's ECLSS testing. Specific tests include: the Stage 10 Water Recovery Test; the Contaminant Injection Test; the Four-Bed Molecular Sieve Performance Enhancement Test; and Life Testing.

Air Conditioning↗
PubMed1988

[Pathologic skin changes in workers at electric and thermoelectric power plants].

Dermatological examination was performed and epidermal tests using a routine set of allergens and metals (Cr, Co, Ni, Al, Cu, Ag, Zn, Hg, Fe) on 112 workers of power plants and thermal-electric power stations working at the stands characterized by a heavy dustiness (electro-filters operation, ash removal, deslagging, carburizing) and at the stands where dustiness was not so heavy but instead exposure to machine oils and greases (retors' operators, electromechanics, assemblers and welders) was remarkable. It was found that occupational exposure to chemicals resulted in skin inflammation in 7.1% of the examined persons. Machine oils and greases induced skin inflammation in 2.7% and occupational acne in 5.3% of workers. It was also observed that chromium compounds were the primary allergen in workers exposed to dusts (13.4% of sensitized persons) and in workers exposed to industrial greases and oils (8.0% of sensitized persons). Allergy to cobalt compounds prevailed among persons exposed to smears and oils. Single positive results of epidermal tests with the use of copper and silver were obtained. Moreover, data concerning the microelements content in fly-ashes are presented. Information on the frequency of the incidence of occupational skin diseases, sickness absenteeism due to dermatoses and on personal safety equipment which should be used by the workers of power industry plants are provided.

Adult↗
PubMed1995

Exposure to occupational and environmental factors in myelodysplastic syndromes. Preliminary results of a case-control study.

We performed a case-control study of occupational and environmental risk factors in myelodysplastic syndromes (MDS) diagnosed at our institution, using the method of Siemiatycki. A control for each MDS case, matched for age, sex, and residence area was chosen. The questionnaire asked demographic data, medical history, and information on life-time environmental and occupational exposures. Occupational exposures were first assessed by job titles, then by evaluating exposure to a list of 70 chemicals, and the level and duration of exposure to those chemicals (exposure index). In the first 100 cases and controls analyzed, a significantly higher incidence of smokers or ex-smokers was seen in MDS cases (odds ratio, OR = 1.83, P = 0.03). A significant excess of MDS was found in male patients with jobs (or previous jobs) generally exposing to chemical compounds, including plant and machine operators and assemblers (odds ratio, OR = 3.73, P = 0.014) whereas, on the contrary, technicians and associate professionals were more often seen in controls (OR = 0.17, P = 0.002). In males, there was also a trend for more skilled agricultural workers and coal miners in MDS cases. In females, there was a non-significant trend for more professionals in controls. After adjusting for sex, age and smoking habits, significantly more frequent exposure to stone dusts (OR = 3.06, P = 0.011), and cereal dusts (OR = 2.27, P = 0.04) was found. There was also a trend for higher incidence of exposure to exhaust gases and nitro-organic explosives. In addition, significantly higher exposure indices to petrol and diesel derivatives (P = 0.03) and to fertilizers (P = 0.003) were seen in MDS cases, as compared to controls. No significant difference in exposure to other chemicals was seen between MDS cases and controls. These preliminary results of our study, which is accruing more cases, suggest, as two previously published case-control studies of risk factors in MDS, that exposure to some chemicals may be involved in the pathogenesis of MDS.

Adult↗
PubMed1997

Molecular automata assembly: principles and simulation of bacterial membrane construction.

The motivation to understand the basic rules and principles governing molecular self-assembly may be relevant to explain in the context of molecular biology the self-organization and biological functions exhibited within cells. This paper presents a molecular automata model to simulate molecular self-assembly introducing the concept of molecular programming to simulate the biological function or operation performed by an assembled molecular state machine. The method is illustrated modelling Escherichia coli membrane construction including the assembly and operation of ATP synthase as well as the assembly of the bacterial flagellar motor. Flagellar motor operation was simulated using a different approach based on state machine definition used in virtual reality systems. The proposed methodology provides a modelling framework for simulation of biological functions performed by cellular components and other biological systems suitable to be modelled as molecular state machines.

Algorithms↗
PubMed1993

Assembly of the Arc repressor-operator complex: cooperative interactions between DNA-bound dimers.

Arc repressor, a member of the beta-ribbon family of DNA binding proteins, binds to its 21-base-pair operator as a tetramer. Here, the Arc dimer is shown to bind specifically to DNA fragments containing operator half-sites, and the equilibrium and kinetic constants for these reactions are determined. DNA-bound dimers are also shown to be transient intermediates in association experiments, indicating that assembly of the Arc tetramer-operator complex occurs by sequential addition of dimers to operator half-sites. When the left or right operator half-site is occupied by an Arc dimer, cooperative interactions increase the affinity of the second dimer by approximately 5900-fold [delta delta G = -5.1 (+/- 0.5) kcal/mol]. This increase in affinity is largely caused by an increase in the half-life of the complex; "non-cooperatively" bound dimers dissociate with a half-life of a few seconds while "cooperatively" bound dimers have half-lives of more than 1 h.

Base Sequence↗
PubMed1998

Coupling of site-specific DNA binding to protein dimerization in assembly of the biotin repressor-biotin operator complex.

The Escherichia coli repressor of biotin biosynthesis, BirA, binds site-specifically to the biotin operator, a 40 base pair imperfect inverted palindrome. Two repressor monomers have been shown to bind to the two operator half-sites. Analysis of results of quantitative DNase I footprint titrations performed on the wild-type biotin operator template indicate that binding is well described by a cooperative mechanism. The data obtained from these studies were, however, insufficient to independently resolve all of the energetic parameters associated with cooperative binding of the two repressor monomers to the operator site. In this work, to further dissect the energetics of assembly of the biotin repressor-biotin operator complex, measurements of binding of BirA to four bioO variants designed to reduce the valency of repressor binding from 2 to 1 have been performed. Results of these measurements indicate, as was found with the wild-type biotin operator template, that two repressor monomers bind simultaneously to the two half-sites of all variant operators. Protein dimerization and DNA binding are thus obligatorily coupled in the biotin repressor system. Furthermore, the results suggest that, in the context of a cooperative binding mechanism, the cooperative free energy associated with the biotin repressor-biotin operator interaction is significantly more favorable than the previously estimated -2 kcal/mol.

Bacterial Proteins↗
PubMed1997

Linkage between operator binding and dimer to octamer self-assembly of bacteriophage lambda cI repressor.

Cooperative binding of the bacteriophage lambda cI repressor dimer to specific sites of the phage operators OR and OL controls the developmental state of the phage. Cooperativity has long been thought to be mediated by self-assembly of repressor dimers to form tetramers which can bind simultaneously to adjacent operators. More recently, we demonstrated that when free repressor dimers self-associate in solution, tetramer is an intermediate in a concerted assembly reaction leading to octamer as the predominant higher order species [Senear, D. F., et al. (1993) Biochemistry 32, 6179-6189]. Even as a minority component in the assembly reaction, tetramer can account for pairwise cooperativity. In a similar manner, were it able to bind all three operators simultaneously, octamer could account for three-way cooperativity. In fact, based solely on repressor self-assembly, the naive prediction is that the repressor-OR interactions should be substantially more cooperative than they are. Evidently, there are unfavorable contributions to cooperativity from processes other than repressor self-assembly. Here, we focus on coupling between repressor self-association and operator binding as one possible unfavorable contribution to cooperativity. Sedimentation equilibrium analysis was used to compare the dimer-octamer association reactions of a repressor dimer-OR1 complex and free repressor dimer. Fluorescence anisotropy was used to investigate OR1 binding to free dimers and dimers assembled as higher order species. The results of these experiments indicate a significant and salt-dependent unfavorable contribution generated by such coupling. Since the oligonucleotides used in these experiments are the size of single operator sites, this coupling is mediated by the protein, not by the DNA. This mechanism does not account for an additional, salt-independent, unfavorable contribution which we presume is transmitted via the DNA. Thus, unfavorable contributions generated by structural transitions in both macromolecules serve to moderate the effect of self-association alone. We speculate that this is a general feature of cooperative protein-DNA interactions.

Bacteriophage lambda↗