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At least 937 records · Page 52Linked to original sources
PubMed2002

Influence of a monetary incentive upon attentional modification of short-lead prepulse inhibition and long-lead prepulse facilitation of acoustic startle.

Short-lead prepulse inhibition and long-lead prepulse facilitation of startle are greater during attended than ignored prestimuli. The present work examined whether this attentional modification is influenced by monetary incentive. Participants (43 college students) were randomly assigned to receive a small performance-based monetary incentive or were instructed to try their best. The task was to judge the duration of tones of one of two pitches during a series of 48 tones. Prepulse inhibition of startle eyeblink EMG was assessed at 60, 120, and 240 ms, and prepulse facilitation was assessed at 4,500 ms following tone onset. Short-lead percent prepulse inhibition was greater during attended than ignored prestimuli only at 120 ms among paid participants. Long-lead prepulse facilitation was greater for attended than ignored tones, but this effect did not vary with incentive condition. This study demonstrates that attentional modification of short-lead prepulse inhibition is sensitive to a monetary incentive and provides a basis for further examination of motivational effects on early attentional processing.

Acoustic Stimulation↗
PubMed1992

[Removal of infected pacemaker leads using lead removal kit (Cook Pacemaker Corporation)].

A new technique for effective removal of chronic transvenous pacemaker lead was developed to address the need for explantation of eroded and infected lead (Lead Removal Kit, Cook Pacemaker Corporation). This Kit consists of a stylet for locking at the distal tip of the lead and a sheath for separating adhering fibrous tissue. Successful removal of 3 leads in 2 patients using this kit was reported.

Aged↗
PubMedDate not supplied

[Resolver unit for recovery of 12 conventional leads from 3 corrected orthogonal leads].

The progress in automatic ECG analysis raised the task to reduce the number of parameters or ECG-leads. Three corrected orthogonal ECG-leads are important. They are unusual for clinicists and lack the verified criteria for diagnosis with their help. The resolver unit proposed is designed to transform the three orthogonal leads into 12 conventional ones. The resolver allows only 3 leads to be recorded, transferred through communication lines and introduced into computer, while, when necessary, one can anlyse data from all 12 conventional leads, and give a conclusion in a form usual for clinicists. This cuts time and costs. The resolver presents also a theoretical interest--as it permits studying the non-dipole components of cardiac vector.

Electrocardiography↗
PubMedDate not supplied

Implications of lead binding proteins for risk assessment of lead exposure.

Lead-binding proteins have previously been isolated from rat and human target tissues. These molecules have shown to possess molecular masses in the general range of 10,000-30,000 daltons. The proteins are acidic in nature and rich in aspartic and glutamic amino acid residues. The molecules in rodents appear to play several important roles in mediating the low dose toxicity of lead in the kidney and brain. Preliminary studies presented in this report indicate that monkeys also possess similar proteins in the kidney and brain, thus providing a biochemical "bridge" in a non-human primate between rodent models and humans. Further, the excretion of these molecules into the urine of rodents increases with lead exposure, suggesting that may also prove useful as biomarkers of lead exposure in humans and monkeys once the dose-range and mechanism(s) of this phenomenon are further defined. Such studies should provide valuable risk assessment information for determining why individuals vary in their susceptibility to lead toxicity.

Animals↗
PubMed1985

Experimental lead neuropathy: inorganic lead inhibits proliferation but not differentiation of Schwann cells.

Schwann cells were prepared from the sciatic nerves of newborn rats and cultured in a monolayer. Addition of lead acetate at concentrations between 0.4 and 10.0 micrograms/ml, levels comparable to those occurring in neural tissues and physiological fluids of lead-intoxicated rats, diminished both the baseline rate of proliferation of the Schwann cells and their response to the mitogens, axolemmal fragments, glial growth factor, and the adenosine 3':5'-cyclic monophosphate (cAMP) analogues 8-bromo-cAMP and dibutyryl-cAMP. This demonstrates a direct toxic effect of inorganic lead on Schwann cells. Lead acetate in this concentration range did not, however, inhibit the cAMP analogue-induced appearance of the "myelin marker" lipid galactocerebroside on the surfaces of the cultured Schwann cells.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1993

Relations between lead exposure and peripheral neuromuscular functions of lead-exposed workers--results of tapping test.

In this study, four experiments using the tapping test were conducted to evaluate the possible subclinical effects of lead exposure on the neuromuscular systems of lead workers at some transfer printing factories in Japan. Decreases in the tapping ability appeared coincidentally with higher blood lead levels. The recovery of the tapping ability after 30 sec rest in the groups of 30-45 micrograms/dl and above 45 micrograms/dl PbB was worse than that in the group with less than 29 micrograms/dl PbB. The recovery of the decreased tapping ability after 60 sec rest was better even in the group with 30-45 micrograms/dl PbB. The tapping ability for 0-10 sec at the first tapping test was sustained after 30 or 60 sec rest in the group with the PbB below 29 micrograms/dl; however, the tapping ability at the second and third tapping test decreased in the two groups with the PbB level above 30 micrograms/dl. The decreased finger tapping speed may be functional evidence of low-grade motor neuropathy among the workers with higher levels of lead absorption.

Adult↗
PubMed1999

Lead in plasma and whole blood from lead-exposed children.

In 31 children exposed to lead and 13 considerably less exposed children ("unexposed"), the plasma (Pb-P) concentrations ranged from 0.46 to 18.4 (median, 2.4) and from 0.14 to 0.38 (median, 0.21) microg/L, respectively. Corresponding whole-blood concentrations (Pb-B) were 99-920 (median, 370) and 39-120 (median, 66) microg/L, respectively. The relation between Pb-B and Pb-P was nonlinear; when Pb-P rose, the Pb-B increased relatively less. There was a close association between Pb-B and log Pb-P (r=0.95; P=0.0001). When these data were compared to previous data on adults, there was no major difference between children and adults in the Pb-B/Pb-P relation. Free erythrocyte protoporphyrins in blood were associated with Pb-P (r=0.75; P=0.0001) and Pb-B (r=0.90; P=0.0001). Also, there was an association between blood-hemoglobin concentration and Pb-P in both exposed (r=-0.67; P=0.0001) and unexposed (r=-0.67; P=0.01) children; the corresponding figures for Pb-B were r=-0.42; P=0.02, and r=-0.80; P=0.001, respectively. Thus, at least with regard to toxicity on hematopoiesis at high lead levels, Pb-P may be a more relevant indicator of exposure and risk than Pb-B. Because the curved Pb-B/Pb-P relation indicates a saturation of binding sites for lead in red cells, exposure and risk at high lead levels may easily be underestimated from Pb-B data.

Adolescent↗
PubMed1991

An inverse lead air to lead blood relation: the impact of air-stream helmets.

At a secondary smelter (24 smelting workers, 13 refinery workers), data on exposure to lead were collected by systematic observation of hygienic behaviour, a questionnaire, personal sampling of lead dust in ambient air (PbA) and determination of lead in the blood level (PbB). The smelting workers showed a negative relation between PbA and PbB. The 53% variance in PbB levels in the smelting workers can be explained by the combination of PbA, the percentage of time an air-stream helmet is worn, the frequency of cigarette smoking at the workplace and the amount of spitting. Air-stream helmets and spitting contribute to a lower PbB, whereas smoking contributes to a higher PbB. Moreover, expected PbB levels were computed by using several regression equations for the relation between PbA and PbB, as suggested in the Final OSHA Standard for Occupational Exposure to Lead (OSHA 1978). As the percentage of time an air-stream helmet is worn increases, the deviation from the expected PbB falls substantially. The refinery workers showed the expected weak positive correlation coefficient between PbA and PbB. No direct relation between the PbB level and the observed hygienic behaviour could be established. However, there was a positive relation between the level of education and the level of PbB. Moreover, the level of education was related to the frequency of eating at the workplace and negative as far as the percentage of time gloves are worn is concerned. Our conclusion is that hygienic behaviour is a major factor that modifies the relation between PbA and PbB in groups of workers.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1998

Urinary excretion of lead and delta-aminolevulinic acid in workers occupationally exposed to tetraethyl lead.

Forty-nine refinery workers and 50 motor mechanics were selected and examined for total lead (PbT), inorganic lead (PbI), and delta-aminolevulinic acid (ALA) in urine. The worker groups were exposed to tetraethyl lead (TEL) mainly by inhalation, but motor mechanics received additional exposure by skin because of hand cleansing with gasoline. The levels of urinary ALA (ALA-U) and urinary PbT (PbT-U) in refinery workers and motor mechanics were found to be significantly higher than the control group (p<0.05). The correlation between the ALA-U and PbT-U was found significant in both worker groups (p<0.001); however, relatively higher positive correlation was found between ALA-U and urinary inorganic lead (PbI-U) in TEL-exposed workers.

Aminolevulinic Acid↗
PubMed1995

Adverse health effects of lead at low exposure levels: trends in the management of childhood lead poisoning.

An extensive database has provided a direct link between low-level lead exposure during early development and deficits in neurobehavioral-cognitive performance evident late in childhood through adolescence. These consistent studies have demonstrated the presence of a constellation of neurotoxic and other adverse effects of lead at blood lead (BPb) levels at least as low as 10 micrograms/dl). Federal agencies and advisory groups have redefined childhood lead poisoning as a BPb level of 10 micrograms/dl. Before discussing some of these studies in greater detail, the pervasiveness of this entirely preventable disease today in millions of American children must be recognized.

Child↗
PubMed1981

Lead exposure and renal failure: does renal insufficiency influence lead kinetics?

Blood and urine lead concentrations have been measured in 40 subjects with normal and impaired renal function. Derived renal lead clearance varied widely, but was not influenced by the degree of renal impairment. Lead, however, appeared to reduce its own clearance. These findings provide additional evidence of nephrotoxicity from sub-clinical lead exposure.

Adolescent↗
PubMed1997

Identification of historical lead sources in roof dusts and recent lake sediments from an industrialized area: indications from lead isotopes.

X-ray fluorescence and stable lead (Pb) isotopic analyses have been undertaken on dusts, known from microscopic investigation to contain significant quantities of industrially- and urban-derived particulate matter, present in the roof cavities of houses in the Illawarra region (N.S.W., Australia), with the objective of examining the historic record of Pb pollution. All investigated houses contained in excess of 250 micrograms g-1 Pb, with dwellings close to a copper smelter, in a large industrial complex including a major steelworks, containing higher (> 2500 micrograms g-1) Pb concentrations. The isotopic composition in the dusts, expressed here as 206Pb/204Pb, is relatively constant at 17.0, irrespective of dwelling age or distance from the industrial complex. Contamination of the dusts by Pb sourced from paint cannot explain the isotopic uniformity of the dust samples. Isotopic modelling indicates that the dusts contain Pb derived from the copper smelter, gasoline-air Pb and a minor contribution from coal-utilising sources. Lead loading was also investigated in the adjacent lagoon, which acts as a natural sink for particulate matter in the Illawarra region. Isotopic data and modelling indicate that one natural and four anthropogenic sources contribute to the Pb burden of this lagoon. The natural source consists of Permian rocks cropping out in the catchment area which have a 206Pb/204Pb of approximately 18.7. The suggested anthropogenic sources are an old disbanded base-metal (Pb) smelter (206Pb/204Pb approximately 16.2-16.3), the copper smelter (206Pb/204Pb approximately 17.9), gasoline-air derived Pb (206Pb/204Pb approximately 16.4-16.5) and industries utilising coal, for example the recently closed thermal coal-fired power station (206Pb/204Pb approximately 18.9). The relative contributions of the base-metal (mainly lead) smelter and gasoline-air Pb in the sediment can only be partly assessed due to the isotopic similarity of these sources. Likewise the natural background and coal source (e.g. power station) contributions can only be estimated from historical data. Age estimations for sediment cores, using 137Cs, provide some control on these assessments. Near surface sediments in the lagoon have a relatively constant 206Pb/204Pb of 17.6-17.7, irrespective of sample location. Isotopic calculations, together with records of particulate matter pollution emissions, indicate a link between the Pb in roof dusts (206Pb/204Pb approximately 17.0) and Pb contamination of the near surface (upper 20 cm) lagoonal sediments via a homogeneous, non-unique source of lead whose isotopic composition closely matches that of the dusts. Over the last 5 decades, atmospheric fallout of Pb-bearing particulate matter appears to have been the dominant pathway for addition of Pb to the lagoon and dwellings in the Illawarra region.

Australia↗
PubMed2003

Causal inference in lead research: introduction to the special section on the neurobehavioral effects of environmental lead.

This Special Section on the Neurobehavioral Effects of Environmental Lead includes empirical reports from three major longitudinal prospective studies and a review of animal research modeling effects of lead on human cognition. This Introductory article addresses a fundamental controversy in lead and other epidemiologic research. It is argued that, contrary to conventional wisdom, valid causal inferences can be made from correlational research. Justification for this is to be found in contemporary frameworks drawn from the field of the philosophy of science; an essential, but often neglected perspective for such metatheoretical issues as causal inference. It is concluded that the nonexperimental methods described in the articles comprising this Special Section can, indeed, contribute to causal formulations of lead effects on human development, and that such inferences are not exclusive to experimental evidence.

Causality↗
PubMedDate not supplied

Lead in feed incident--multi-element analysis of cattle feed and tissues by inductively coupled plasma-mass spectrometry and co-operative quality assurance scheme for lead analysis of milk.

Contaminated cattle feed was imported into the UK in 1989 and resulted in lead toxicity in some animals. Rapid analyses for lead and several other possible contaminating elements were required for feed and cattle tissues. Microwave dissolution of samples with measurement by ICP-MS was used for multi-element determinations. Lead was found to be the major contaminant. Lead levels in milk samples were measured by several laboratories during the crisis and an analytical quality assurance scheme was devised to monitor the quality of the data. The scheme allowed any poorly performing laboratories to be rapidly identified and excluded from the survey.

Animal Feed↗
PubMed1981

Lead encephalopathy in infants in Kuwait. A study of 20 infants with particular reference to clinical presentation and source of lead poisoning.

Twenty patients aged between one and eighteen months (mean six months) were found to have lead encephalopathy. They were seen in one 30-bed ward during a four year period from 1977 to 1980. Blood lead was determined in 19 children and ranged between 2.9 and 12.4 mumol/l (60 and 257 micrograms/dl) mean 5.42 mumol/l (113 micrograms/dl). Two patients died before starting treatment. Of the 18 patients treated with B.A.L. (2.3 dimercaptopropanol) and EDTA (ethylenediaminetetra-acetic acid), three died. Eleven patients made an apparently complete recovery and four had neurological sequelae. The source of lead was traced in 18 patients: in 11 it was due to the liberal use of Kohl (also known as surma) commonly used as an eye cosmetic in the Arabian peninsula. Other local sources of lead poisoning are discussed.

Brain Diseases↗
PubMedDate not supplied

Rapid, sensitive micro blood lead analysis: a mass screening technique for lead poisoning.

A rapid micro blood lead method is described. Analyses were performed on 20-microL blood samples spotted on filter paper, collected in graduated heparinized capillary glass tubes following finger pricks. The samples were air dried on filter paper and mailed to the laboratory in glassine envelopes. These samples stored on filter paper are stable for at least six months. The blood spots were punched out with a 1/4-in. diameter hole punch and placed in Delves cups for insertion into the flame atomic absorption spectrometer. The innovation of this method is that an ashing step precedes sample introduction into the flame. In phase 1, the Delves cup with the blood sample is pushed 1 cm from the flame. The heat is sufficient for the filter paper to ignite and burn to completion in seconds. After the smoke dissipates, the samples are introduced into the flame for lead analysis, reading the signal at 283.3 nm. The entire analysis time is 15 s per sample. The limit of quantitation is 4 micrograms/dL of lead. Standard curves were linear from 4-42 micrograms/dL. The average CV for this range is 8.2%. The comparative study between the MIBK extraction method and this method yielded a correlation coefficient r = .99 (n = 55). The method is fast, practical, economical, and easily adaptable to screen large numbers of micro lead samples.

Humans↗
PubMed2003

Changing trends in the epidemiology of pediatric lead exposure: interrelationship of blood lead and ZPP concentrations and a comparison to the US population.

OBJECTIVES: To determine blood lead and zinc protoporphyrin (ZPP) concentrations in a pediatric population, confirm their interrelationship at low blood lead concentrations, and assess changing trends through comparison of these data with those found in a similar population 10 years earlier and to US national values. STUDY DESIGN AND METHODS: The study was conducted in a large pediatric hospital in the Washington DC area (CNMC) on patient whole blood specimens (n = 4908) (0-17 years) accrued from January 2001 to June 2002. Pediatric blood lead concentrations were determined by atomic absorption spectrophotometry, and ZPP by hematofluorometry. The data were analyzed using a computer adaptation of the Hoffmann approach. RESULTS AND CONCLUSIONS: Blood lead level (BLL) means ranged between 2.2 and 3.3 micro g/dL, and the median BLL was 3 micro g/dL throughout. Mean ZPP concentrations ranged between 21.1 and 26.6 micro g/dL and the median concentrations between 21 and 27 micro g/dL. In comparison to data obtained from a similar pediatric population at CNMC between 1991 and 1992, pediatric BLLs have significantly declined in the Washington DC area. The current data are also compared with data obtained from the National Health and Nutrition Examination Survey (NHANES III) of the US population. The interrelationship between ZPP and BLLs is examined.

Adolescent↗
PubMed1997

Leaded gasoline abuse: the role of tetraethyl lead.

Volatile substance abuse is practised worldwide however reports of the abuse of leaded gasoline have been limited to northern Canada, southwestern USA and the Australian Outback. Chronic, heavy abuse of leaded gasoline results in an encephalopathy, cerebellar and corticospinal symptoms and signs, dementia, mental status alterations, and persistent organic psychosis. Much of this is due to the hydrocarbons of gasoline while the tetraethyl lead contributes to the altered mental status and is responsible for the persistent psychosis. Lead chelation therapy is not rational and has not been shown to benefit these patients.

Administration, Inhalation↗