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Biomedical subjects

Michael Lasarev

Publications and source records attributed to Michael Lasarev.

15 recordsLinked to original sources
PubMed2006

Neurobehavioral performance of adult and adolescent agricultural workers.

There are many occupational hazards associated with working in agriculture including risk of injury and exposure to pesticides. Research examining neurobehavioral effects of pesticide exposure have focused primarily on the acute effects in adults working in agriculture. Organophosphate poisoned populations have shown a consistent pattern of deficits when compared to a non-exposed or non-poisoned population on measures of motor speed and coordination, sustained attention, and information processing speed. Fewer studies have examined the effect of long-term low-level exposure on nervous system functioning in agricultural workers. Pesticides are thought to pose a considerably higher risk to children than to adults, yet little is known about the extent or magnitude of health problems related to occupational exposure to pesticides in children and adolescents. The present study compared the neurobehavioral performance of adolescents and adults working in agriculture and examined the impact of years working in agriculture on neurobehavioral performance. One hundred seventy-five Hispanic adolescent and adults completed a neurobehavioral test battery consisting of 10 computer-based tests measuring attention, response speed, coordination and memory. Age, gender, school experience, and years working in agriculture all impacted performance on the neurobehavioral tests. Comparison of adult and adolescents did not reveal decreased neurobehavioral performance in adolescents. On several tests the adolescents performed better than adult counterparts. The adolescents and adults were engaged in comparable agricultural working environments at the time of the neurobehavioral testing. These findings suggest that, at the time of exposure to pesticides, adolescents are not more vulnerable to the effects of working in agriculture. Evidence from this study suggests that cumulative exposure to low levels of pesticides over many years of agricultural work is associated with neurological impairment as measured by the Selective Attention, Symbol-Digit, Reaction Time tests. Experience handling pesticides was also associated with deficits in neurobehavioral performance.

Adolescent↗
PubMed2006

Organophosphate pesticide exposure and neurobehavioral performance in agricultural and non-agricultural Hispanic workers.

Our understanding of the health risks of farmworkers exposed to pesticides in their work and home environments is rapidly increasing, although studies designed to examine the possible neurobehavioral effects of low-level chronic pesticide exposure are limited. We measured dialkyl phosphate urinary metabolite levels, collected environmental dust samples from a subset of homes, obtained information on work practices, and conducted neurobehavioral tests on a sample of farmworkers in Oregon. Significant correlations between urinary methyl metabolite levels and total methyl organophosphate (azinphos-methyl, phosmet, malathion) house dust levels were observed. We found the neurobehavioral performance of Hispanic immigrant farmworkers to be lower than that observed in a nonagricultural Hispanic immigrant population, and within the sample of agricultural workers there was a positive correlation between urinary organophosphate metabolite levels and poorer performance on some neurobehavioral tests. These findings add to an increasing body of evidence of the association between low levels of pesticide exposure and deficits in neurobehavioral performance.

Agriculture↗
PubMed2006

Effectiveness of cleaning practices in removing pesticides from home environments.

The deposition of agricultural pesticides in the homes of agricultural workers and residents of agricultural communities is a major environmental health concern. The effectiveness of home cleaning activities in removing pesticides from home surfaces has not been tested. An intervention study was conducted to assess the effectiveness of cleaning windowsills, floors and carpets in a sample of 10 farmworker homes. Baseline measures of organophosphorus (OP) pesticide residues were obtained, a standardized cleaning intervention was applied and follow-up measures of pesticide residues were obtained within 24-48 hours after the cleaning and 12 months later. House dust was analyzed for six OP pesticides. All homes had detectable baseline levels of OP pesticides on floors and windowsills. Cleaning of linoleum floors was ineffective in removing total pesticide residues and cleaning effectiveness varied among the pesticides. The cleaning of total OP pesticides on the windowsills was effective (median decrease was 0.0029 microg/cm(2), 1-sided p-value = 0.01). Steam cleaning carpets essentially reduced the amounts to non-detectable levels. In 12 months the levels in carpets had accumulated to one-third of the baseline levels. These results provide evidence that cleaning practices can reduce the amount of pesticides in agricultural homes; however the type of surface being cleaned and the pesticides present in the home may influence results.

Environmental Exposure↗
PubMed2006

Atm haploinsufficiency does not affect ionizing radiation mutagenesis in solid mouse tissues.

Ataxia telangiectasia (AT) is a hereditary disease with autosomal recessive inheritance of ATM (ataxia telangiectasia mutation) alleles. AT is associated with severe sensitivity to ionizing radiation and a strong predisposition to develop cancer. A modest increase in cancer, particularly for the breast, has been shown for ATM carriers (i.e. heterozygotes), and a modest increase in radiation sensitivity has also been shown for those patients and their cells. However, the extent of these effects is unclear. Based on the well-established relationship between cancer and mutation, we used a mouse model for Atm haploinsufficiency to ask whether partial loss of Atm function could lead to an increased mutagenic response for solid tissues of mice exposed to radiation. The autosomal mouse Aprt gene was used as the mutational target and kidney and ear as the target tissues in B6D2F1 hybrids. Although induction of autosomal mutations was readily demonstrated in both tissues, a comparison of these data with those from an identical study performed with B6D2F1 mice that were wild-type for Atm (Cancer Res. 62, 1518-1523, 2002) revealed that Atm haploinsufficiency did not alter the radiation mutagenic response for the cells of either tissue. Moreover, no effect of Atm haploinsufficiency on reduced cellular viability due to radiation exposure was observed. The results demonstrate that Atm haploinsufficiency does not alter the radiation mutagenic response or decrease viability for normally quiescent cells in solid tissues of the mouse.

Animals↗
PubMed2005

High frequency induction of mitotic recombination by ionizing radiation in Mlh1 null mouse cells.

Mitotic recombination in somatic cells involves crossover events between homologous autosomal chromosomes. This process can convert a cell with a heterozygous deficiency to one with a homozygous deficiency if a mutant allele is present on one of the two homologous autosomes. Thus mitotic recombination often represents the second mutational step in tumor suppressor gene inactivation. In this study we examined the frequency and spectrum of ionizing radiation (IR)-induced autosomal mutations affecting Aprt expression in a mouse kidney cell line null for the Mlh1 mismatch repair (MMR) gene. The mutant frequency results demonstrated high frequency induction of mutations by IR exposure and the spectral analysis revealed that most of this response was due to the induction of mitotic recombinational events. High frequency induction of mitotic recombination was not observed in a DNA repair-proficient cell line or in a cell line with an MMR-independent mutator phenotype. These results demonstrate that IR exposure can initiate a process leading to mitotic recombinational events and that MMR function suppresses these events from occurring.

Adaptor Proteins, Signal Transducing↗
PubMed2005

Neurobehavioral performance in preschool children from agricultural and non-agricultural communities in Oregon and North Carolina.

Organophosphate (OP) pesticides produce acute toxic effects but little is known about low-level chronic exposures. Latino children of agricultural workers have a high risk of exposure to pesticides because of the close proximity of their homes to fields where pesticides are applied and from take-home exposure. Neurobehavioral performance of preschool children from agricultural (AG) communities was compared to performance of those from non-agricultural (Non-AG) communities in Oregon and North Carolina. Seventy-eight children aged 48-71 months completed a battery of neurobehavioral tests two times, approximately 1 month apart. Multiple regression revealed that the AG children performed poorer on measures of response speed (Finger Tapping) and latency (Match-to-Sample) compared to the Non-AG children. These results demonstrate modest differences in AG children compared to Non-AG children that are consistent with functional effects seen in adults exposed to low concentrations of OP pesticides. Just as was the case following early research on adults poisoned by pesticides, this study points to the need for additional investigations to test the hypothesis that low-concentration OP exposures affect acquisition of test performance, response speed and latency in children of agricultural workers.

Age Factors↗
PubMed2005

Career risk of hepatitis C virus infection among U.S. emergency medical and public safety workers.

OBJECTIVE: A probabilistic model was used to analyze the cumulative risk of occupational hepatitis C virus (HCV) infection among U.S. public safety workers. METHODS: A model for the career risk of HCV was developed using the frequency of parenteral exposures to blood, the population seroprevalence of HCV, and the risk of seroconversion after exposure. Estimates of key input variables were obtained from published studies. RESULTS: Calculated estimates of the 30-year risk of infection ranged from <0.1% for police, firefighters, and corrections officers to 1.9% among paramedics and emergency department personnel in high-risk communities. Infrequent exposure to high-risk blood seems to present a greater risk of infection than more frequent contact to low-risk populations. CONCLUSIONS: Use of a probabilistic risk assessment model using published data can assist in policy decisions designed to protect the health and safety of workers. Further efforts to document the frequency of occupationally acquired HCV are needed.

Emergency Medical Technicians↗
PubMed2005

Variation in organophosphate pesticide metabolites in urine of children living in agricultural communities.

Children of migrant farmworkers are at increased risk of exposure to organophosphate pesticides because of "carry-home" transport processes and residential location. Although this at-risk status is generally recognized, few available reports describe the extent of this exposure among agricultural communities. We quantified dialkyl phosphate (DAP) levels in serial samples of urine from 176 children, 2-6 years of age, in three Oregon communities hosting differing agricultural industries: pears, cherries, and fruit berries. Up to three spot samples of urine were collected from children at the beginning, mid-point, and end of their parents' work seasons. The median levels of dimethylthiophosphate (DMTP), the most commonly detected metabolite, was significantly higher in urine samples from children in each of the three agricultural communities (17.5, 19.0, and 41.0 ng/mL) relative to a reference group of children who lived in an urban community and whose parents did not work in agriculture (6.5 ng/mL; Kruskal-Wallis, p < 0.001). After controlling for age, sex, and weight, the median level of DMTP in children in the pear community was 1.92 times higher than the level in children of the berry community [95% confidence interval (CI), 1.14-3.23] and 1.75 times higher than the level in children of the cherry community (95% CI, 0.95-3.23). We observed increasing levels of DMTP across the work season only within the berry community. Levels decreased in the cherry community and remained constant in the pear community. Substantial temporal variation within the children followed demonstrates the need for multiple urine samples to most accurately characterize longer term and/or cumulative exposure. The observed variability in urinary DAP levels, between communities and over time, could be attributed to the types and amounts of organophosphate pesticides used, the timing of applications and degradation of residues in the environment, work operations and hygiene practices, the proximity of housing to orchards and fields, or the movement of these working families. Additional studies of variation in pesticide exposure across agricultural regions are needed.

Agriculture↗
PubMed2004

Persistence of chromatid aberrations in the cells of solid mouse tissues exposed to 137Cs gamma radiation.

Primary mouse ear and kidney cultures were established for determination of cytogenetic aberrations at short (3 days to 1 month) and long (12-23 months) times after exposure of their right sides to 7.5 Gy of (137)Cs gamma radiation. In every case, higher levels of aberrations were observed in primary cultures established from the irradiated tissues than in those established from the contralateral tissues. The most common aberrations in the contralateral tissues and those from nonirradiated mice were chromatid and isochromatid breaks and small chromatid fragments. Primary cells from irradiated tissues removed from animals within a month of exposure displayed a variety of unstable chromosome-type aberrations characteristic of recent exposure to ionizing radiation including rings, dicentrics, double minutes, and large acentric fragments. The percentages of cells exhibiting chromatid breaks and small chromatid fragments were also markedly elevated. Although the levels of chromosome-type aberrations found in primary cells from irradiated tissues dropped to near background levels a year or more after exposure, chromatid-type aberrations remained elevated. These results are consistent with long-term persistence of damage in the genomes of ionizing radiation-exposed cells in solid tissues and the induction of genomic instability in vivo.

Animals↗
PubMed2003

Pesticide exposure and self reported home hygiene: practices in agricultural families.

Little is known about environmental exposure to pesticides and the extent to which exposure is affected by drift from agricultural applications and take home exposure from agricultural workers. The study focused on 24 agricultural families in the northwestern United States and measured levels of organophosphate pesticides (OP) in house dust. Pesticide residues were significantly associated with the number of individuals in the home whose work included high exposure pesticide activities. Mean levels of pesticides were higher in the homes of workers who reported waiting more than 2 hours before changing out of their work clothes compared with homes where workers change within 2 hours after returning from work (p < .01). The results of this study provide evidence that workers can inadvertently carry agricultural chemicals from their work into their homes, thereby increasing the risk of pesticide exposure to other family members inside the home.

Agriculture↗
PubMed2002

Tissue-specific deletion and discontinuous loss of heterozygosity are signatures for the mutagenic effects of ionizing radiation in solid tissues.

The mouse Aprt locus on chromosome 8 was used as the selectable target for the study of spontaneous and ionizing radiation-induced mutations in kidney epithelia and ear fibroblasts. Fifty-two Aprt heterozygous mice were exposed to 7.5 Gy of (137)Cs-gamma radiation on their right sides, and Aprt-deficient clones were isolated from enzymatically digested tissues at times ranging from 1 day to 14 months after irradiation. A statistically significant increase in the mutant frequencies for the irradiated tissues was observed when compared with the spontaneous mutant frequencies for the nonirradiated tissues. A molecular analysis of spontaneous mutations observed for the nonirradiated tissues revealed tissue-specific differences; apparent chromosome loss was common in kidney mutants but infrequent in the ear mutants, whereas apparent deletions were common in the ear mutants but not detected in the kidney mutants. For the irradiated kidneys, apparent deletions were observed commonly demonstrating that these events are markers for ionizing radiation mutagenesis in this tissue. All of the loss of heterozygosity (LOH) tracts observed in the spontaneous mutants were continuous, but discontinuous LOH patterns were observed in 6--8% of ionizing radiation-induced ear and kidney cell mutants. Work with kidney-derived cell lines showed that discontinuous LOH is a novel signature for delayed ionizing radiation mutagenesis. Considered together, these results suggest that ionizing radiation-induced mutations in vivo can result from both direct and delayed mutagenic effects.

Animals↗
PubMed2002

Illness experience of Gulf War veterans possibly exposed to chemical warfare agents.

BACKGROUND: During the 1991 Gulf War, some Allied troops were potentially exposed to chemical warfare agents as the result of the detonation of Iraqi munitions at Khamisiyah. METHODS: In 1999, we conducted a computer-assisted telephone survey of 2918 Gulf War veterans from Oregon, Washington, California, North Carolina, and Georgia to evaluate the prevalence of self-reported medical diagnoses and hospitalizations among this potentially exposed population and among comparison groups of veterans deployed and nondeployed to the Southwest Asia theater of operations. RESULTS: Troops reported to be within 50 kilometers of the Khamisiyah site did not differ from other deployed troops on reports of any medical conditions or hospitalizations in the 9 years following the Gulf War. Hospitalization rates among deployed and nondeployed troops did not differ. Deployed troops were significantly more likely to report diagnoses of high blood pressure (odds ratio [OR]=1.7); heart disease (OR=2.5); slipped disk or pinched nerve (OR=1.5); post-traumatic stress disorder (OR=14.9); hospitalization for depression (OR=5.1); and periodontal disease (OR=1.8) when compared to nondeployed troops. There was a trend for deployed veterans to report more diagnoses of any cancer (OR=3.0). CONCLUSIONS: These findings do not provide evidence of any long-term health effect associated with exposure to the detonation of chemical warfare agents, but support findings from other investigations of increased morbidity among deployed troops. The prevalence of cancer among this population of deployed troops merits ongoing attention.

Chemical Warfare Agents↗
PubMed2002

Un lugar seguro para sus ninos: development and evaluation of a pesticide education video.

The need exists for culturally appropriate and effective educational interventions to reduce pesticide exposure in migrant and seasonal farm-worker (MSFW) communities. The development of one such intervention was part of a community-based research project which partnered the Oregon Health Sciences University and the Oregon Child Development Coalition (Migrant Head Start). The process involved identifying an optimal educational method and content, evaluating existing educational materials on pesticides, developing the selected educational tool (a video), and assessing the effectiveness of the video as an intervention. Focus groups were conducted with MSFWs to elicit their perceived need for education and desired content, method, and delivery. Four currently used educational tools were evaluated for satisfaction, preference, recall ability and knowledge change. Based on these findings, a pesticide exposure video directed at the protection of children was produced. To determine the effectiveness of the video, knowledge, satisfaction and self-reported behaviors were assessed with MSFWs. A sizeable increase in overall pesticide knowledge was measured after seeing the video (p < 0.0001). MSFWs overall were satisfied with the video and reported increased protective behaviors after seeing the video.

Journal Article↗
PubMed2002

Hepatitis C in urban and rural public safety workers.

A sample of 719 Oregon public safety personnel (police officers, firefighters, and corrections officers) was tested for hepatitis C virus (HCV) antibody after completing a risk questionnaire. Seven of nine positive enzyme immunoassay tests (78%) were confirmed with recombinant immunoblot assay, yielding confirmed prevalence estimates of 1.2% (95% confidence interval, 0.4 to 2.8%) among the 406 firefighters and emergency medical technicians, and 0.7% (95% confidence interval, 0.1 to 2.6%) in 274 corrections personnel. No cases were observed in the 29 participating police officers. Self-reports of the number of workplace exposures to blood were not associated with HCV positivity, and the number of years of public safety employment seemed to be slightly less for HCV-positive subjects. Two of the seven (28.6%) HCV-positive individuals reported having at least one nonoccupational risk factor (odds ratio, 4.3; 95% confidence interval, 0.4 to 27.1), suggesting the greater relative importance of nonoccupational exposures.

Adolescent↗