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 1,099 records · Page 61Linked to original sources
PubMed1996

Environmental tobacco smoke exposure in inner-city children.

Exposure to environmental tobacco smoke (ETS) was assessed as part of a pilot study aimed at determining the extent of multiple toxicant exposures in children from inner-city areas of Baltimore, MD. Questionnaire data on sources of ETS and urinary cotinine were obtained in children considered at high risk for urban exposures because of previous or current overexposure to one inner-city environmental hazard, lead. Fifty-three (67.1%) of the 79 participants were exposed to ETS in the preceding 48 h as assessed by questionnaire. Cotinine was present in 77 (98.7%) of the 78 samples assayed with a mean of 79.2 ng/mg creatinine (54.7 ng/ml). Eighty % of children had cotinine values > or = 30 ng/mg creatinine, a level commonly associated with household ETS exposure. Levels in children without reported ETS exposure in their homes were also elevated (mean = 45.0 ng/mg creatinine). As expected, blood lead levels were elevated with a mean of 23.6 micrograms/dl. We conclude that these inner-city children have substantial exposures to both ETS and lead. Furthermore, the presence of elevated cotinine levels in children without known household exposure suggests that ETS should be considered an urban toxicant as well as an individual residential exposure.

Baltimore↗
PubMed1983

Organic chemicals and malignant melanoma.

Chemists with cancer were interviewed to generate hypotheses that might explain an apparent excess of malignant melanoma in chemists in Los Angeles County (LAC). The chemists were identified by the LAC Cancer Surveillance Program, a population-based cancer registry. Interviews that included information on work history and exposure to specific chemicals were conducted by telephone. Chemists with melanoma were found to be better educated than chemists with other cancers and they reported more work with organic chemicals. They also cited more exposure to multiple chemicals, solvents, plastics, pesticides, benzoyl peroxide, and ionizing radiation. Although differences in educational level may account for the differences in exposure reported by cases and controls, the hypotheses that specific chemical exposures are related to melanoma occurrence are plausible and deserve further study. We also suggest that this method of generating hypotheses about cancer causes using cases identified from registries could be used more extensively.

Adult↗
PubMed1999

High resolution confocal laser scanning microscopy analysis of DNA excision repair capability in small volume marrow samples exposed to DNA directed treatment moieties.

BACKGROUND: Assessment of resistance to drug moieties in tissue culture is complicated by limited sample, clonal selection and alteration of cycling fraction and cycle duration in clonally mixed lesions. DNA damage assessment by single cell gel electrophoresis (SCGE) of excised DNA is limited by non-linear analysis in fluorescent light microscopy. Confocal Laser Scanning Microscopy (CLSM) with high N.A. magnification allows for quantitation of total excised DNA fragment size distribution but is still limited by the large volume required for labour intensive SCGE, precluding multi-exposure clinical testing. AIMS: To optimise sample requirement for SCGE and CLS. METHODS: Standard slide mounted bed gels were punched with multiple coded 6 mm wells and filled with suspensions of cells subjected to drug/concentration variations. After SCGE, 30 microns frozen sections were prepared of each well and mounted in ethidium bromide solution on multi-well hydrophilic slides to allow for short working distance of high resolution CLSM in a Zeiss Axiovert L410 SM. Testing for feasibility, reproducibility and consistency used both cultured standard leukaemic cell lines, normal human control marrow and clinical samples. RESULTS AND CONCLUSION: Multiple well SCGE followed by frozen section, high resolution CLSM allows for rapid analysis of high numbers of multiple drug exposure permutations clinically required.

Bone Marrow Cells↗
PubMedDate not supplied

Biological effects of marine PCB contamination on black guillemot nestlings at Saglek, Labrador: liver biomarkers.

Black guillemots (Cepphus grylle) in Saglek Bay, Labrador have elevated polychlorinated biphenyl (PCB) concentrations due to marine sediment contamination around a former military site. We measured liver biomarkers and sigmaPCB concentrations in 31 nestlings from three PCB-exposure groups: Reference group (range: 15-46 ng/g liver, wet wt.), moderately exposed Islands group (24-150 ng/g), and highly exposed Beach group (170-6200 ng/g). Biomarker responses were dose-dependent and in some cases sex-dependent. Livers of female Beach nestlings were enlarged 36% relative to Reference females. In both sexes, Beach nestlings had liver ethoxyresorufin-O-deethylase (EROD) activities elevated 79% and liver retinol concentrations reduced 47%. Retinyl palmitate concentrations were reduced 50% but only among female nestlings. Island nestlings also exhibited EROD induction (57%) and reductions in retinol and retinyl palmitate concentrations (28 and 58%, respectively). Liver lipid content increased with sigmaPCBs in both sexes, and correlated with liver mass in males. Malic enzyme activity and porphyrin concentrations showed little association with sigmaPCBs. Although similar associations between liver biomarkers and organochlorine exposure in fish-eating birds are well documented, typically exposures involve multiple contaminants and there is uncertainty about specific PCB effects. Our findings indicate that liver biomarkers respond to relatively low PCB exposures (approximately 73 ng/g liver) in guillemots.

Animals↗
PubMed2003

Effect of inhaled ultrafine carbon particles on the allergic airway response in ragweed-sensitized dogs.

Episodic increases in air pollution have been associated with the exacerbation of asthma symptoms. Ultrafine particles are a component of air pollution and may be involved in causing the adverse health effects associated with high air pollution. We evaluated the effects of ultrafine particle inhalation on immune and airway responses in a beagle dog model of allergic asthma. Six allergic (ragweed sensitive) and six nonallergic dogs were exposed to ultrafine carbon particles (232.3 +/- 2.5 microg/m(3), 35.2 +/- 0.3 nm) for 1 h, followed by a challenge with vehicle (water) as a negative control. Airway resistance was measured during particle exposure and after vehicle challenge. Immune responses 3 days before and after (1 h and 1, 4, 7, and 11 days) particle exposure were assessed by measuring total immunoglobulin E (IgE) and ragweed-specific IgE and IgG in serum and bronchoalveolar lavage fluid (BALF), and cell differentials in BALF. Each dog was exposed a second time to ultrafine carbon particles (251.4 +/- 5.3 microg/m(3), 34.9 +/- 0.5 nm) for 1 h followed by a challenge with ragweed and the same measurements. Airway resistance did not change during particle exposure in any of the dogs, and ragweed-induced airway reactivity was not altered by particle exposure. Total and ragweed-specific serum IgE and total IgE in BALF were higher in allergic dogs at all time points. Particle exposure did not affect antibody levels in serum or BALF in allergic dogs. Nonallergic dogs developed specific IgG in response to multiple inhalation exposures to ragweed, but this was not associated with particle exposure. Neutrophils were elevated in BALF for all groups 1 day after particle exposure. In conclusion, despite the induction of low level inflammation in the lungs of allergic and nonallergic dogs, exposure to ultrafine carbon particles did not alter airway reactivity or immune responses.

Ambrosia↗
PubMed1996

Introduction of a donor exposure reduction programme for multiple-transfused very-low-birth-weight infants.

OBJECTIVE: To conduct an audit of the frequency of red cell concentrate transfusions (RCCTs) in infants of different weight categories, the donor exposure rate (DER), in these transfused infants and the volume of blood wasted during each transfusion, and to identify from this baseline information specific categories of infants who would benefit from the introduction of a limited donor exposure programme (LDEP). STUDY SETTING: Neonatal wards and neonatal intensive care unit (NICU), Tygerberg Hospital, Western Cape. STUDY DESIGN: A prospective descriptive study and comparison with a historic control group. SUBJECTS: Information on the birth weight, age at the time of each RCCT and number of blood donors to whom an infant was exposed were collected post factum for all infants admitted to the neonatal wards and NICU between May 1993 and May 1994. During this time, the red blood cell concentrate was supplied as single paediatric bags (180 ml) transfused within 14 days of donation. An LDEP was introduced in February 1995. With this system, red blood cells were supplied as triple packs: a main unit of 250 ml with three empty satellite packs allowing up to three separate transfusions. These were assigned to a specific infant and were to be transfused within 21 days of donation. A second system where one adult blood bag was divided into two 180 ml bags and assigned to one infant to be transfused within 35 days of donation was also assessed. RESULTS: Of the 7854 infants admitted during the first 12-month audit period, 387 (4.9%) received 977 RCCTs. Of these, 183 (47.3%) received one transfusion, 72 (18.6%) two transfusions, 51 (13.2%) three transfusions, 27 (7.0%) four transfusions and 54 (13.9%) five or more transfusions. Infants (N = 188) with a birth weight below 1500 g admitted to the NICU were identified as the group with the highest prevalence of RCCTs (68.6%), and it was therefore decided that in the prospective study such infants would qualify for the LDEP. A total of 81 infants was transfused with either the double (N = 47) or the triple bags (N = 34) over a 5-month period. The decrease in the mean DER (+/-SD) was clinically significant when the triple (1.9 +/- 0.8) (P = 0.0001) and the double bags (1.6 +/- 0.8) (P = 0.0001) were compared with the previous single-bag system (4.4 +/- 3.5). Of concern was the large mean volume of concentrated red cells (118.5 +/- 12.5 ml) wasted per transfusion with the single-bag system. CONCLUSIONS: This survey confirmed a high RCCT rate as well as a very high DER in very-low-birth-weight (VLBW) infants treated at a tertiary centre. By assigning a triple or double bag of red cells from one blood donor and extending the storage of blood for small-volume RCCTs in infants from 14 days to 35 days, donor exposure was reduced significantly. We urge the introduction of the multibag blood transfusion system and extended storage period of blood for small-volume RCCT for VLBW infants in South Africa.

Adult↗
PubMed2004

Assessment of the magnetic field exposure due to the battery current of digital mobile phones.

Hand-held digital mobile phones generate pulsed magnetic fields associated with the battery current. The peak value and the waveform of the battery current were measured for seven different models of digital mobile phones, and the results were applied to compute approximately the magnetic flux density and induced currents in the phone-user's head. A simple circular loop model was used for the magnetic field source and a homogeneous sphere consisting of average brain tissue equivalent material simulated the head. The broadband magnetic flux density and the maximal induced current density were compared with the guidelines of ICNIRP using two various approaches. In the first approach the relative exposure was determined separately at each frequency and the exposure ratios were summed to obtain the total exposure (multiple-frequency rule). In the second approach the waveform was weighted in the time domain with a simple low-pass RC filter and the peak value was divided by a peak limit, both derived from the guidelines (weighted peak approach). With the maximum transmitting power (2 W) the measured peak current varied from 1 to 2.7 A. The ICNIRP exposure ratio based on the current density varied from 0.04 to 0.14 for the weighted peak approach and from 0.08 to 0.27 for the multiple-frequency rule. The latter values are considerably greater than the corresponding exposure ratios 0.005 (min) to 0.013 (max) obtained by applying the evaluation based on frequency components presented by the new IEEE standard. Hence, the exposure does not seem to exceed the guidelines. The computed peak magnetic flux density exceeded substantially the derived peak reference level of ICNIRP, but it should be noted that in a near-field exposure the external field strengths are not valid indicators of exposure. Currently, no biological data exist to give a reason for concern about the health effects of magnetic field pulses from mobile phones.

Brain↗
PubMed1994

Fetal alcohol syndrome: the vulnerability of the developing brain and possible mechanisms of damage.

Fetal alcohol exposure has multiple deleterious effects on brain development, and represents a leading known cause of mental retardation. This review of the effects of alcohol exposure on the developing brain evaluates results from human, animal and in vitro studies, but focuses on key research issues, including possible mechanisms of damage. Factors that affect the risk and severity of fetal alcohol damage also are considered.

Animals↗
PubMed2006

Preventing sensitization with mycophenolate mofetil in a pediatric kidney recipient.

Sensitization, as measured by panel reactive antibodies (PRAs), occurs as a result of previous organ transplantation, blood transfusions, or pregnancy. The high-PRA levels increase the risk of complications during transplantation and may result in long time duration for future transplants. Mycophenolate mofetil (MMF) has been shown to decrease lymphocyte proliferation and antibody formation. We report the use of prophylactic MMF in preventing the formation of PRAs in a pediatric renal transplant recipient with multiple donor exposures. A four-yr-old girl received an unsuccessful living-related renal transplant in February 2003 and was subject to multiple blood transfusions in the perioperative period. MMF, 500 mg/m2/day in two divided doses, achieved suppression of PRAs to less than 20% and allowed successful renal transplantation within nine months. No side effects occurred. This approach may reduce the risk of sensitization in future potential organ donor recipients in similar situations.

Cell Proliferation↗
PubMed2006

Urban adolescent mothers exposed to community, family, and partner violence: is cumulative violence exposure a barrier to school performance and participation?

Using a risk and resilience perspective, the authors assessed urban adolescent mothers' exposure to community, family, and partner violence and analyzed the relationships between cumulative violence exposure and multiple school outcomes, within the context of welfare reforms. Positive attitude toward school and social support were examined as moderators of violence exposure on school outcomes. The authors pilot tested the questionnaire with 10 participants, then surveyed 120 adolescent mothers regarding their violence exposure, school performance and participation, positive attitude toward school, and social support. Results indicate very high rates of lifetime exposure to violence; intercorrelations and regression analyses indicate that as violence exposure increases, school outcomes tend to worsen, with positive attitude toward school found to be a significant moderator of the effects of exposure to community violence on behavior problems in school. Implications for researchers, practitioners, school policies and programs, and welfare policies and programs conclude the article.

Achievement↗
PubMed1966

Multiplicity reactivation of reovirus particles after exposure to ultraviolet light.

McClain, Mary E. (California State Department of Public Health, Berkeley), and Rex S. Spendlove. Multiplicity reactivation of reovirus particles after exposure to ultraviolet light. J. Bacteriol. 92:1422-1429. 1966.-Exposure of reovirus suspensions to moderate doses of ultraviolet light results in essentially exponential inactivation of infectivity to survivals of 10(-2) to 10(-3). With suspensions of sufficiently high particle concentration, larger doses of ultraviolet light (6 to 12 min) are associated with multiplicity reactivation (MR) which is demonstrable both by immunofluorescent-cell count and by plaque assay in FL human amnion cells. Similar effects are produced by photodynamic inactivation in the presence of proflavine, but not by thermal inactivation at 50 C. All three reovirus types exhibit MR under appropriate conditions, and all three interact in mixed ultraviolet suspensions with high efficiency. Progeny from FL cells infected under conditions of MR were as infectious as those of unirradiated inocula, with yields per cell ranging from 10(4) to 4 x 10(4) infective units.

Amnion↗
PubMed2005

Prenatal exposure to fluconazole: an identifiable dysmorphic phenotype.

BACKGROUND: Fluconazole is a triazole antifungal used to treat mycotic infections. Fluconazole is reported to act as a teratogen when used continuously at a dosage of 400-800 mg daily. Fluconazole embryopathy was previously reported in 4 cases. The common features that were also seen in the current case include multiple synostosis (including craniosynostosis and digital synostosis), congenital heart defects, skeletal anomalies, and recognizable dysmorphic facial features. CASE: We report the case of a 9-month-old male born to a 30-year-old woman following a 37-week pregnancy. The pregnancy was complicated by maternal human immunodeficiency virus (HIV) infection and multiple drug exposures, including fluconazole (400 mg/day) until the fifth month and then from 6 months to term, efavirenz, nevirapine, methadone, dapsone, pentamidine, and trimethoprim-sulfamethoxazole. At birth the infant had seizures related to neonatal abstinence syndrome and was noted to have multiple congenital anomalies. On examination at age 9 months, he had craniosynostosis secondary to coronal and lambdoidal suture closures, shallow orbital region, hypoplastic supraorbital ridges, hypertelorism, and mild ptosis. He had radioulnar synostosis and metacarpophalangeal-proximal interphalangeal symphalangism of D2-D5 bilaterally. CONCLUSIONS: The findings of cranial synostosis, multiple symphalangism, and long-bone abnormalities in our case are typical of other reported cases of fluconazole embryopathy. Our patient showed no evidence of embryopathy due to efavirenz, and he did not have the features of Antley-Bixler or other craniosynostosis syndromes. We review the literature regarding the teratogenic effects of prenatal exposure to fluconazole and provide additional evidence that prenatal fluconazole exposure has a clearly identifiable phenotype.

Abnormalities, Drug-Induced↗
PubMed2002

A prospective analysis of trauma exposure: the mediating role of PTSD symptomatology.

Trauma exposure has been associated with increased risk of exposure to additional traumatic events. Reactions to trauma exposure, specifically PTSD symptomatology, may mediate the link between trauma exposure and later traumatic events. Data from a longitudinal sample of Gulf War veterans (N = 2,949) were analyzed using a series of regression models. Higher levels of combat exposure were related to increased reports of PTSD symptomatology immediately upon return as well as increased reports of traumatic events in the 2 years following the Gulf War. PTSD symptomatology partially mediated the link between combat exposure and later trauma. Symptom clusters were also analyzed separately as potential mediators. Implications for the treatment of PTSD and prevention of exposure to multiple traumas are discussed.

Adult↗
PubMed2000

[Irritating effect and dermal toxicity of virkon, a disinfectant widely used in Poland].

The aim of the study was to define the threshold irritating effect of Virkon, a disinfectant widely used in Poland, on the rabbit's skin and eye, and its dermal toxicity in single exposure. The studies were carried out according to the OECD guidelines, modified by Krysiak. A 10% aqueous solution of Virkon in the conditions of multiple open exposure was defined as the threshold concentration evoking small inflammatory reaction. After a single administration of Virkon in aqueous solutions into the rabbit's eye, the value of sensitising effect index was 1.5 for 1% solution of the disinfectant in question which indicates weak inflammatory reaction. The study of dermal toxicity in a single exposure revealed neither animal death nor morphological changes in internal organs which suggests non-cutaneous absorption of Virkon. The present study may provide the basis for assessing dermatological changes in people exposed to disinfectants.

Animals↗
PubMed2001

Diazepam during prior ethanol withdrawals does not alter seizure susceptibility during a subsequent withdrawal.

The number of cycles of alcohol detoxification is suggested to be an important variable in the predisposition to severe withdrawal seizures in alcohol-dependent individuals. Several clinical studies have suggested that exposure to repeated alcohol withdrawals may lead to increased severity of subsequent withdrawal episodes. Consistent with these observations, exposure to multiple cycles of ethanol withdrawal in our previous study significantly increased sensitivity to the convulsive effects of the GABA(A) receptor inverse agonist, Ro15-4513, in comparison to continuous ethanol exposure with no intermittent withdrawals. There was also a selective increase in the occurrence of spontaneous spike and sharp wave (SSW) activity in the EEG recorded from hippocampal area CA(3) in proportion to the number of withdrawal episodes experienced. It is hypothesized that during such repeated episodes of ethanol intoxication and withdrawal, changes in neuronal excitation during prior withdrawals could serve as initially subconvulsive kindling stimuli that might eventually result in the increased severity of the withdrawal syndrome. There is some evidence of the successful suppression of such neuronal excitation during acute ethanol withdrawal by positive modulators of the GABA(A) receptor. In the present study, the benzodiazepine agonist, diazepam, at a dose (4.0 mg/kg) that suppresses acute withdrawal symptoms, when administered during intermittent withdrawals, did not alter seizure sensitivity during a subsequent nonmedicated withdrawal. Diazepam treatment during prior withdrawals also did not have any effect on the multiple withdrawal-associated increase in SSW activity in hippocampal area CA(3) during an untreated withdrawal. This finding suggests that suppression of acute withdrawal symptoms by diazepam does not prevent long-lasting changes in CNS function resulting from repeated exposures to ethanol withdrawal.

Affinity Labels↗
PubMed1973

Schedule-induced mirror responding in the pigeon.

Two pigeons that were previously exposed to a multiple schedule of reinforcement in the presence of a stuffed and a live pigeon, and two of three naive pigeons, responded on a mirror during exposure to multiple fixed-ratio, fixed-ratio schedules of reinforcement for key pecking. Both the topography and temporal pattern of mirror responding were comparable to schedule-induced "attack" on live and stuffed targets. Rate of target responding was reduced when either the mirror was covered with paper or when the multiple schedule was removed. A reversal in the relationship between reinforcement schedules and discriminative stimuli demonstrated that mirror responding was controlled by the stimulus correlated with the higher fixed-ratio schedule. With one component of the multiple schedule held constant at fixed ratio 25 and the ratio requirement of the other component varying from 25 to 150, there was an inverted U-shaped relationship between rate of mirror responding and fixed-ratio schedule in the varied component. As in Flory's study (1969b) there was an inverted U-shaped relationship between target responding and inter-food intervals. The combined results of these studies suggest that the relationship between rate of target responding and reinforcement schedules is controlled primarily by the inter-food intervals resulting from the schedules.

Journal Article↗
PubMed2000

[Pre- and post-natal corticosteroids: side effects].

It is well known that prenatal steroid therapy (ST) reduces the mortality rate and the incidence of respiratory distress syndrome and intraventricular haemorrhage in premature infants. The benefits and safety of repeated courses of antenatal ST are doubtful due to possible side effects in the mother and baby. Experimental studies in animals have shown that multiple courses of antenatal ST have deleterious effects on lung growth and organisation, brain myelination, hypothalamic-pituitary-adrenal function and retina development. In humans, exposure to multiple courses of antenatal ST is associated with small head circumference at birth and increased incidence of maternal endometritis and early-onset neonatal sepsis. When administered soon after birth, ST may enable a reduction in ventilator settings and facilitate weaning from mechanical ventilation, but although associated with rapid improvement in lung function, it does not modify mortality or long-term outcome and has many acute side effects. Deleterious effects on lung maturation and neuro-developmental outcome, including cerebral palsy, have also been reported. The paucity of follow-up data is a major problem, and further prospective trials are needed.

Adrenal Cortex Hormones↗
PubMed2005

[Concept of cerebral mechanisms underlying prolonged adaptation to environmental hazards, according to I.M. Sechenov's scientific heritage].

Occupational medicine is based on scientific ideas of Ivan Mikhailovitch Sechenov, the first Russian researcher of bioelectric activity of brain. Contemporary neurophysiologic methods of formalized quantitative evaluation of homeostasis in higher brain structures enable to optimize early etiologic diagnosis and prevention of central nervous and cardiovascular systems stress under exposure to multiple occupational hazards.

Adaptation, Physiological↗