Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “multiple exposures”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 451 records · Page 25Linked to original sources
PubMed1991

Modeling the interactions between noise exposure and other variables.

The interaction of noise exposure with other variables is reviewed. For the case of the interaction of noise with other variables that produce behavioral threshold shifts, the application of a newly developed model is described and demonstrated. This model, referred to as the modified power-law model, provides an accurate prediction of the combined effects of two threshold-elevating factors. The model accounts for the interaction of post-exposure a pre-existing pre-existing permanent loss or a pre-existing temporary loss. The model's application is demonstrated for multiple exposures to steady-state noise in which each exposure lasts as short as 12 min or as long as 6 h. Finally, implications of the model's application to the interaction long as 6 h. Finally, implications of the model's application to the interaction of noise with other ototraumatic agents are reviewed.

Auditory Fatigue↗
PubMed2001

RD114-pseudotyped oncoretroviral vectors. Biological and physical properties.

Limited functional expression of the viral envelope receptor is a recognized barrier to efficient oncoretroviral mediated gene transfer. To circumvent this barrier we evaluated a number of envelope proteins with respect to gene transfer efficiency into primitive human hematopoietic stem cell populations. We observed that oncoretroviral vectors pseudotyped with the envelope protein of feline endogenous virus (RD114) could efficiently transduce human repopulating cells capable of establishing multilineage hematopoiesis in immunodeficient mice after a single exposure to RD114-pseudotyped vector. Comparable rates of gene transfer with amphotropic and GALV-pseudotyped vectors have been reported, but only after multiple exposures to the viral supernatant. Oncoretroviral vectors pseudotyped with the RD114 or the amphotropic envelopes had similar stability in vitro, indicating that the increased efficiency in gene transfer is at the receptor level likely due to increased receptor expression or an increased receptor affinity for the RD114 envelope. We also found that RD114-pseudotype vectors can be efficiently concentrated, thereby removing any adverse effects of the conditioned media to the long-term repopulating potential of the target human hematopoietic stem cell. These studies demonstrate the potential of RD114-pseudotyped vectors for clinical use.

Animals↗
PubMedDate not supplied

[Health risk caused by exposure to low-dose chemical agents at research laboratories].

In literature there are many works on the exposure to organic solvents and its risk. In research laboratories the risk valuation is really problematic due to different variables such as low dose, multiple exposure to substances with different characteristic of hazardous. We analyzed the blood exams of workers of seven biomedical research laboratories for finding a correlation between exposition and the variability of some parameters.

Adult↗
PubMed2005

Allergen avoidance in asthma: what do we do now?

Although allergen exposure can clearly aggravate the condition of sensitized patients with asthma, there is uncertainty and controversy about exactly which allergen avoidance interventions should be recommended to patients with asthma. Interventions that appear logical may fail to be clinically efficacious for several reasons. Although narrow interventions, such as allergen-impermeable mattress covers to reduce exposure to dust mite allergens, may offer little benefit if used alone, recent evidence suggests that a multifaceted, home-based environmental intervention focusing on multiple exposures may provide clinical benefits to patients with asthma. The role of allergen avoidance in infancy in the primary prevention of asthma is a subject of active investigation, but data remain too preliminary to make public health recommendations in this regard.

Allergens↗
PubMed2003

Health and human development: understandings from life-course research.

It is now well understood that life-course factors affect a diverse range of outcomes, from general well-being to physical functioning and chronic diseases. Exposure to both beneficial and adverse circumstances over the life course will vary for each individual and will constitute a unique life exposure trajectory, which will manifest as different expressions of health and well-being. Here, we present a 3-fold model of life-course influences on health: latency, cumulative, and pathway. By latency we mean relationships between an exposure at one point in the life course and the probability of health expressions years or decades later, irrespective of intervening experience. Cumulative refers to multiple exposures over the life course whose effects on health combine. Finally, pathways represent dependent sequences of exposures in which exposure at 1 stage of the life course influences the probability of other exposures later in the life course, as well as associated expressions. Evidence demonstrating these relationships suggests that, without a consideration of early life as well as adult life experience, policies designed to improve health status tend to overlook root causes.

Animals↗
PubMed2004

Odor-taste interactions: effects of attentional strategies during exposure.

Through repeated pairings with a tastant such as sucrose, odors are able to take on the tastant's qualities, e.g. by becoming more sweet smelling. When such odors are subsequently experienced with a sweet tastant in solution, the mixture is often given a higher sweetness rating than the tastant alone. Odor-induced taste enhancement appears to be sensitive to whether an odor-taste combination is viewed analytically as a set of discrete qualities, or synthetically as a flavor. The present research attempted to determine if adoption of these different perceptual approaches during co-exposure with sucrose would influence the extent to which an odor would become sweet smelling and subsequently enhance sweetness intensity. In Experiment 1, subjects received multiple exposures to mixtures of sucrose with low sweetness, low familiarity odors or, as a control, the odors and sucrose solutions separately. Two groups that received mixtures made intensity ratings that promoted either synthesis or analysis of the individual elements in the mixtures. The odors became sweeter smelling irrespective of group. Only adopting a synthetic strategy produced odors that enhanced sweetness in solution. However, these effects were also shown with a 'non-exposed' control odor. This could be accounted for if the single co-exposure with sucrose that all odors received in the pre-test was able to produce sweeter odors. A second experiment confirmed this prediction. Thus, while even a single co-exposure with sucrose is sufficient to produce a sweeter odor, the adoption of a synthetic perceptual strategy during the co-exposure is necessary to produce an odor that will enhance sweetness. These data are consistent with associative leaning accounts of how odors take on taste qualities and also support the interpretation that these effects reflect the central integration of odors and tastes into flavors.

Adolescent↗
PubMed2006

Occupational exposure to organic solvent mixtures during pregnancy and the risk of non-syndromic oral clefts.

OBJECTIVES: To examine the association between maternal occupational exposure to mixtures of organic solvents during pregnancy and the risk of non-syndromic oral clefts. METHODS: A case-control study (164 cleft lip with/without cleft palate (CL/P), 76 cleft palate (CP), 236 controls) was conducted in France to investigate the role of maternal occupational exposure to organic solvents at the beginning of pregnancy in the risk of non-syndromic oral clefts. An expert chemist, guided by a detailed description of the women's occupational tasks, assessed exposure for each. Analysis of the findings used logistic regression. RESULTS: In the control group, 39% of the women who reported working during pregnancy were exposed to at least one type of organic solvent. The risk of oral clefts was associated with oxygenated (for CL/P: OR = 1.8, 95% CI 1.1 to 2.9; and for CP, OR = 1.4, 95% CI 0.7 to 2.7), chlorinated (OR = 9.4, 95% CI 2.5 to 35.3; OR = 3.8, 95% CI 0.7 to 20.7), and petroleum (OR = 3.6, 95% CI 1.5 to 8.8; OR = 1.2, 95% CI 0.3 to 4.9) solvents. The risk of oral clefts increased linearly with level of exposure within the three subgroups of oxygenated solvents we considered (aliphatic alcohols, glycol ethers, and other oxygenated solvents, including esters, ketones, and aliphatic aldehydes). CONCLUSIONS: Results suggest that maternal occupational exposure to organic solvents during pregnancy may play a role in the aetiology of oral clefts. The limited number of subjects and the problem of multiple exposures require that these results be interpreted cautiously.

Adult↗
PubMed1978

Jaundice after repeated exposure to halothane: a further analysis of reports to the Committee on Safety of Medicines.

Aanalysis of data derived from 170 reports of jaundice developing after anaesthesia with halothane received after January 1974 confirmed the relations between multiple exposure to halothane and jaundice and between the number of exposures and the rapidity with which jaundice develops after exposure. When these reports were combined with 130 received earlier complete anaesthetic histories were available for 251 patients, 205 (82%) of whom had been exposed to halothane more than once; of these patients, 154 (75%) had been exposed more than once within 28 days. Altogether 139 (46%) of the 300 patients died.

Anesthesia, Inhalation↗
PubMed1992

Numerical phase algorithm for decompression computers and application.

Present generation decompression computers employ a simplified algorithm, limiting dissolved gas build-up in tissue and blood according to a method proposed by Haldane 80 years ago. Such a model works well for single dives, but is usually liberal and theoretically incomplete for multiple exposures within 24 hr spans. Using the critical phase hypothesis in a bubble model, we have extended the classical model of Haldane to multi-exposures. This model is discussed, and a decomputer algorithm described for multi-diving. The focus is permissible bubble excess, not just dissolved gas per se, with phase constraints affecting all tissues, fast and slow, and requiring a systematic lowering of repetitive tissue tensions. Deep repetitive and shallow multi-day exposures are impacted most by the procedure. Within nucleation theory deeper-than-first dives are also treated. A set of multi-diving fractions, xi, accounting for micronuclei excitation and regeneration, reduced bubble elimination in repetitive activity, and coupled effects on tissue tension, are proposed, with xi representing a set of multiplicative factors (less than one) applied to critical tissue tensions for multi-exposures. These factors affect repetitive activity over short time spans, deeper-than-previous and continuous multi-day activities, compared to standard computer software, and are easily encoded into existing decompression meters, potentially extending their range and flexibility over exposure regimes.

Algorithms↗
PubMed1977

Influence of aliphatic alcohols on the hepatic response to halogenated olefins.

The role of alcohols in potentiating the toxicity of halogenated hydrocarbon solvents has been reviewed. The toxicity of carbon tetrachloride and chloroform can be markedly potentiated by prior treatment with ethanol or phenobarbital. Trichloroethylene toxicity may also be potentiated by ethanol ingestion. Prior ethanol ingestion acts by altering biochemical parameters that result in an increased response to subsequent solvent exposure. Simultaneous exposure to both ethanol and trichloroethylene allows for competitive substrate inhibition of metabolism since these compounds share several common enzymatic pathways. Thus the toxic response to multiple exposures varies depending upon the time sequence and the comparative levels of the individual components. Phenobarbital apparently potentiates solvent toxocity by induction of the microsomal mixed function oxidase system. Ethanol, either on a chronic or single dose basis, also has the ability to stimulate this enzyme system. Although alteration of the microsomal mixed function oxidase system by chronic ethanol ingestion may play an important role in potentiation of solvent toxicity, the potentiation seen following a single dose of ethanol cannot be fully accounted for by the known effects of ethanol on the mixed function oxidase system. In addition to ethanol a large number of other alcohols will markedly potentiate the hepatotoxic response to solvents such as carbon tetrachloride and chloroform. The mechanisms involved in such potentiation are not known at the present time.

Alcohols↗
PubMedDate not supplied

Sperm motility analysis using multi-exposure photography (MEP): validity of the method with normal and abnormal patterns.

Spermatozoon motility is an important semen parameter that can be correlated with fertilizing capacity. It can be evaluated by subjective or objective methods such as the multiple exposure photography technique (MEP). This technique was: (1) validated in terms of accuracy and sensitivity, and (2) used to investigate the possibility of differentiating patient subgroups on the basis of sperm motility. The method was shown to be accurate. The within and between assay variation coefficients were less than 6% and 17% respectively. Maximal sensitivity required 100 spermatozoa, since coefficients of variation were high when counting smaller numbers. A significant difference between fertile, normozoospermic and asthenozoospermic groups on the basis of the population pattern was found in a retrospective study. Moreover, the asthenozoospermic group could be divided into three subgroups, depending on whether one, two, or three motility variables were altered.

Humans↗
PubMed1997

[Age, work and spinal pain].

BACKGROUND: To examine whether the relationship between age and musculoskeletal disorders in the spine is specific to one localization (cervical, dorsal, lumbar) or due to the accumulation of lesions with age. METHODS: Data were gathered from the ESTEV study among a randomly selected sample of 21,378 French workers, followed by 390 occupational physicians during the year 1990. The subjects, males or females, were born in 1938, 1943, 1948, 1953. Participation rate (88%) did not depend on age and sex. Data were collected during annual medical examination for medical variables, and using standardized self questionnaires for occupational exposures and work constraints for actual or past jobs. RESULTS: Data on musculo-skeletal disorders, defined as pains during the last 6 months before examination, were recorded by occupational physician. Each painful localization was associated with the main factors described in the literature, particularly heavy physical work factors and psycho-social factors of work. There was no interaction between age and any of these. At the opposite, in male as female subjects, there was a statistically significant interaction between age, multiple exposures to heavy physical work factors and the frequency of multiple localizations of pain in the spine. CONCLUSION: Results suggest that accumulation of pain in the different localizations of the spine might account for accelerated aging process of the musculo-skeletal structure of the spine which can reflect effects of environmental work factors.

Adult↗
PubMed1984

Inhalation toxicity of dibutylhexamethylenediamine in rats.

Dibutylhexamethylenediamine (DBHMD), a polymer intermediate, is strongly alkaline and is corrosive to eyes and skin. Its inhalation toxicity was defined in rats in both acute and subchronic studies. A 4-hr LC50 of 0.22 mg/litre was obtained for DBHMD of either 80.6 or 98.25% purity. Clinical signs of irritation were apparent during and immediately following exposure and no delayed deaths occurred. The mortality dose-response line was relatively steep. Reduction of exposure times to 5 min produced an LC50 of 51 mg/litre, with similar clinical signs and a steep dose-response line. These data suggest that the product of concentration and time (Ct) is constant for exposure times ranging from 5 min to 4 hr. Repeated (ten) exposures to 0.0125 mg/litre caused no signs of adverse response in rats. A concentration of 0.0234 mg/litre caused some mortality, mucous-membrane irritation, changes in haematological parameters (including erythrocyte counts, haemoglobin, concentration and total and differential leucocyte counts) and an increased acidity and decreased volume of urine. Death at this exposure level was attributed to cardiac failure secondary to pulmonary oedema and congestion, with evidence of hepatic congestion, diffuse cardiac myocytolysis and oedema, and thymic atrophy and congestion. Changes in the heart and thymus were seen in one of two rats killed after the tenth exposure. Clinical and pathological changes observed after the ten exposures were absent after a 14-day recovery period. DBHMD is highly toxic following acute inhalation and produces a steep dose-response following either single or multiple exposures.

Animals↗
PubMed1991

Parental occupations of children with leukaemia in west Cumbria, north Humberside, and Gateshead.

OBJECTIVE: To determine whether parental occupations and chemical and other specific exposures are risk factors for childhood leukaemia. DESIGN: Case-control study. Information on parents was obtained by home interview. SETTING: Three areas in north England: Copeland and South Lakeland (west Cumbria); Kingston upon Hull, Beverley, East Yorkshire, and Holderness (north Humberside), and Gateshead. SUBJECTS: 109 children aged 0-14 born and diagnosed as having leukaemia or non-Hodgkin's lymphoma in study areas during 1974-88. Two controls matched for sex and date and district of birth were obtained for each child. MAIN OUTCOME MEASURES: Occupations of parents and specific exposure of parents before the children's conception, during gestation, and after birth. Other adults living with the children were included in the postnatal analysis. RESULTS: Few risk factors were identified for mothers, although preconceptional association with the food industry was significantly increased in case mothers (odds ratio 2.56; 95% confidence interval 1.32 to 5.00). Significant associations were found between childhood leukaemia and reported preconceptional exposure of fathers to wood dust (2.73, 1.44 to 5.16), radiation (3.23, 1.36 to 7.72), and benzene (5.81, 1.67 to 26.44); ionising radiation alone gave an odds ratio of 2.35 (0.92 to 6.22). Raised odds ratios were found for paternal exposure during gestation, but no independent postnatal effect was evident. CONCLUSION: These results should be interpreted cautiously because of the small numbers, overlap with another study, and multiple exposure of some parents. It is important to distinguish periods of parental exposures; identified risk factors were almost exclusively restricted to the time before the child's birth.

Adolescent↗
PubMed2005

Daily repeated magnetic field shielding induces analgesia in CD-1 mice.

We have recently observed that a single exposure of mice to a magnetically shielded environment can attenuate opioid induced analgesia. Here, we report the effect of repeated exposures to the same magnetically shielded environment. Adult male Swiss CD-1 mice were placed in a Mu-metal lined box or an opaque Plexiglas box (sham condition) for 1 h per day for 10 consecutive days. Nociception was measured as the latency time to a foot lift/lick in response to an aversive thermal stimulus (hotplate analgesiometer, 50 +/- 1 degrees C) before and immediately after exposure. Multiple experiments were conducted in which thermal latency was tested on each of the 10 days or on days 1, 5, and 10, with some utilizing post-exposure testing only. It was shown that mice can detect and will respond to the repeated absence of the ambient magnetic field, with a maximum analgesic response occurring over days 4-6 of exposure and returning to baseline thereafter. The effect was robust, independent of pre-exposure and intermittent testing, and seems to be opioid related, since the results obtained on day 5 were similar to those from a 5 mg/kg dose of morphine and were abolished with the opioid antagonist, naloxone.

Analgesia↗
PubMed2001

Prevalence of vaginal colonization by drug-resistant Candida species in college-age women with previous exposure to over-the-counter azole antifungals.

We enrolled 382 college-age women in a cross-sectional survey to investigate the relationship between use of over-the-counter (OTC) azole-based antifungal drugs and vaginal colonization by drug-resistant Candida. This study showed no correlation (P=.506) between previous OTC exposure and colonization of drug-resistant Candida in vaginal flora. However, a small number of resistant Candida species isolates were obtained from women with a history of multiple exposures to OTC antifungals; given the widespread use of these products, this may be an emerging concern.

Adult↗
PubMed1987

A comparison of the melanocyte response to narrow band UVA and UVB exposure in vivo.

The visible cutaneous pigmentary response to ultraviolet-A (UVA) is immediate and, following sufficient exposure, may persist, whereas ultraviolet-B (UVB)-induced pigmentation appears after a delay of several days. We compared the in vivo response of melanocytes to single and multiple exposures of narrow band UVA and UVB irradiation which produced visibly equal increases in pigmentation. Using a xenon-mercury source matched to a monochromator, human volunteers were exposed to 304 (+/- 5) and 365 (+/- 10) nm radiation. Biopsies were performed 1, 7, and 14 days after irradiation. For each biopsy, the number of melanocytes per square millimeter of epidermis was determined using L-3,4-dihydroxyphenylalanine (dopa)- and tyrosine-incubated split epidermal preparations. Vertical sections were also examined. At days 7 and 14, after both 304 and 365 nm radiation, melanocytes were more intensely dopa-positive than in unirradiated controls, and demonstrated enlarged perikarya and a greater number of enlarged dendrites. Following both 304 and 365 nm radiation the number of dopa-positive melanocytes was increased at days 7 and 14 by 44% and 58%, respectively. Tyrosine positivity, an indicator of enhanced tyrosinase activity and increased melanin formation, was absent in controls and at day 1, and became positive in all but one sample at day 7 and day 14. Therefore, one day after UVA exposure, visible pigmentation but not tyrosinase activity was increased. At day 7, the number of tyrosine-positive melanocytes approximately equaled the number of dopa-positive melanocytes. Although UVA and UVB induce different pigmentary responses, their effects on melanocyte number and function were indistinguishable.

Adult↗
PubMed2004

Occupations and exposures in the work environment as determinants for rheumatoid arthritis.

BACKGROUND AND AIMS: Several occupational categories have been associated with rheumatoid arthritis (RA); this study was conducted to further evaluate these associations. METHODS: Lifelong occupational history together with exposure experiences were collected through a postal questionnaire answered by 293 incident cases and 1346 population based referents. Occupational determinants were evaluated through stratified and multivariate analyses; pooled analyses with previously gathered data on 422 prevalent cases and 858 referents were also performed. RESULTS: In both materials, significantly increased logistic odds ratios (LORs) were seen for male conductors, freight and transport workers (LOR 17.8, 95% CI 1.5 to 207.8 and LOR 4.7, 95% CI 1.4 to 16.3, respectively), and farmers and farm workers (LOR 2.4, 95% CI 1.1 to 5.2, and LOR 2.2, 95% CI 1.3 to 3.5, respectively). Among women, increased LORs were seen in the separate and the pooled material for printmakers and process engravers (LOR 5.5, 95% CI 0.9 to 32.6, and LOR 3.0, 95% CI 0.9 to 10.3, respectively). Increased risks were seen in both materials for men exposed to asbestos (LOR 2.5, 95% CI 1.0 to 6.8, and LOR 1.6, 95% CI 0.8 to 3.3, respectively), and vibrations (LOR 2.0, 95% CI 0.9 to 4.4, and LOR 2.2, 95% CI 1.3 to 3.8, respectively). The risk for RA increased with increasing duration of exposure to vibrations and mineral dust, respectively. CONCLUSIONS: There was evidence of a causal relation between exposures to vibrations and mineral dust and development of RA among men. Occupational factors seem to be aetiologically more important for men, and most occupations at risk involve multiple exposures. Several exposures associated with an increased risk for RA are frequent among farmers, and some of the occupations at risk include exposure to organic dust.

Adolescent↗