Adult female rats' altered diurnal locomotor activity pattern following chronic methylphenidate treatment.

Methylphenidate (MPD) is one of the most prescribed pharmacological agents, which is also used for cognitive enhancement and recreational purposes. The objective of this study was to investigate the repetitive dose-response effects of MPD on circadian rhythm of locomotor activity pattern of female WKY rats. The hypothesis is that a change in the circadian activity pattern indicates a long-lasting effect of the drug. Four animal groups (saline control, 0.6, 2.5, and 10.0 mg/kg MPD dose groups) were housed in a sound-controlled room at 12:12 light/dark cycle. All received saline injections on experimental day 1 (ED 1). On EDs 2-7, the control group received saline injection; the other groups received 0.6, 2.5, or 10.0 mg/kg MPD, respectively. On ED 8-10, injections were withheld. On ED 11, each group received the same dose as EDs 2-7. Hourly histograms and cosine statistical analyses calculating the acrophase (ϕ), amplitude (A), and MESOR (M) were applied to assess the 24-h circadian activity pattern. The 0.6 and 2.5 mg/kg MPD groups exhibited significant (p < 0.05) change in their circadian activity pattern on ED 11. The 10.0 mg/kg MPD group exhibited tolerance on ED 11 and also a significant change in activity pattern on ED 8 compared to ED 1, consistent with withdrawal behavior (p < 0.007). In conclusion, chronic MPD administration alters circadian locomotor activity of adult female WKY rats and confirms that chronic MPD use elicits long-lasting effects.

Potential gains in life expectancy from reducing heart disease, cancer, Alzheimer's disease, kidney disease or HIV/AIDS as major causes of death in the USA.

OBJECTIVES: Potential gains in life expectancy (PGLEs) that give proper consideration to competing risks are an effective indicator for measuring the impact of multiple causes of death on a defined population. This study aimed to assess PGLE by hypothetically reducing the major causes of death in the USA from 2001 to 2008. STUDY DESIGN: PGLEs due to the reduction and elimination of heart disease, cancer, Alzheimer's disease, kidney disease or human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) were calculated by age, gender and race. METHODS: Age-specific mortality rates for the above diseases from the National Center for Health Statistics were used, and multiple decremental life tables were constructed to compute the corresponding PGLEs. RESULTS: PGLEs due to the elimination of heart disease, cancer or HIV/AIDS decreased from 2001 to 2008, but PGLEs due to the elimination of Alzheimer's disease or kidney disease increased over time. For heart disease, PGLE in 2001-2008 for all races was 2.78-2.15 for females vs 2.41-2.06 for males. For cancer, PGLE in 2001-2008 for all races was 2.97-2.81 for females vs 3.02-2.85 for males. HIV/AIDS has a greater impact on people of working age, whereas Alzheimer's disease has a greater impact on the elderly population. To compare the impacts of these diseases on life expectancy, partial multiple decremental life tables were constructed, and PGLEs were computed by a partial reduction or complete elimination of various causes of death for the entire life span as well as for certain working ages. CONCLUSION: This study outlined a picture of how each category of diseases could affect life expectancy in the US population by age, race or sex. The findings may assist in evaluating current public health improvements, and also provide useful information for directing future research and disease control programmes.

Adolescent rat circadian activity is modulated by psychostimulants.

Circadian pattern of activity regulates many aspects of mammalian physiology and behavior to particular times of the day by entraining the circadian clocks to external environmental signals. Since circadian rhythms are sensitive to many pharmacological agents, it is important to understand if the repetitive use of psychostimulants such as amphetamine will alter the circadian rhythm behavioral activity pattern. The present study uses male Sprague-Dawley rats to study the long-term effects of amphetamine on the locomotor circadian rhythm activity pattern. Rats were randomly assigned to a testing cage that recorded their locomotor activity nonstop for eleven days using the open field assay, as follows: one day of baseline activity was recorded and then the experimental group was injected with amphetamine (0.6mg/kg) for 6days, no treatment for 3days (i.e., washout days) and then re-challenged with amphetamine for one more day while the control group was treated similarly with saline. The Cosine Curve Statistical Analysis (CCSA) test was used to fit a 24-hour curve to activity pattern. Results indicate that repetitive daily amphetamine injections cause behavioral sensitization and a significant change of circadian rhythm of locomotor activity pattern, and elicit behavioral expectation to receive the drug or expression of withdrawal during the washout days. The results suggest that either changes in circadian rhythm caused sensitization and withdrawal or sensitization and withdrawal caused the change in circadian rhythm activity.

Organisational and occupational risk factors associated with work related injuries among public hospital employees in Costa Rica.

AIMS: To explore the relation between occupational and organisational factors and work related injuries (WRI) among public hospital employees in Costa Rica. METHODS: A cross-sectional survey was conducted among a stratified random sample of 1000 employees from 10 of the 29 public hospitals in Costa Rica. A previously validated, self-administered questionnaire which included occupational and organisational factors and sociodemographic variables was used. From the final eligible sample (n = 859), a total of 842 (response rate 98%) questionnaires were returned; 475 workers were analysed after excluding not-at-risk workers and incomplete questionnaires. WRI were computed for the past six months. RESULTS: Workers exposed to chemicals (RR = 1.36) and physical hazards (RR = 1.26) had higher WRI rate ratios than non-exposed workers. Employees reporting job tasks that interfered with safety practices (RR = 1.46), and a lack of safety training (RR = 1.41) had higher WRI rate ratios than their counterparts. Low levels of safety climate (RR = 1.51) and safety practices (RR = 1.27) were individually associated with an increased risk of WRI. Also, when evaluated jointly, low levels of both safety climate and safety practices showed the highest association with WRI (RR = 1.92). CONCLUSIONS: When evaluated independently, most of the occupational exposures and organisational factors investigated were significantly correlated with an increased injury risk. As expected, some of these associations disappeared when evaluated jointly. Exposure to chemical and physical hazards, lack of safety training, and low levels of safety climate and safety practices remained significant risk factors for WRI. These results will be important to consider in developing future prevention interventions in this setting.

Pesticide safety training and access to field sanitation among migrant farmworker mothers from Starr County, Texas.

Very little published research describes employer compliance with EPA-mandated Worker Protection Standard (WPS) pesticide safety training and the OSHA Field Sanitation Standard among farmworker women in general and mothers specifically. A goal of both standards is limiting farmworkers' exposure to potentially hazardous agricultural pesticides. Data from a NIOSH-supported cohort study ("Injury and Illness Surveillance in Migrant Farmworker Families") allowed for examining these issues. The cohort included 267 migrant farmworker families who usually reside along the Texas-Mexico border (Starr County, Texas). Data were collected in Starr County during in-home interviews. Of 102 mothers who participated in migrant farm work during summer 2001, 57 (55.9%) reported having ever received training/instruction in the safe use of pesticides, while 47 (46.1%) reported having received training within the previous five years, as required by WPS. Of trained mothers, 91.5% to 93.6% reported that their training covered key WPS areas: (1) entry into a recently treated field, (2) pesticide related injuries/illnesses, and (3) where to go and who to contact for emergency care following exposure. Regarding access to field sanitation, 67.5% to 84.2% of 77 mothers who worked outside Texas reported employer-provided decontamination supplies (e.g., soap, wash water, towels, and toilet facilities). However, a strikingly smaller proportion (12% to 28%) of 25 mothers who worked within Texas reported access to the same resources, suggesting discrepancies in compliance across the U.S. Due to the low level of employer compliance with both WPS and OSHA mandated standards, increased enforcement and an alternate delivery of pesticide training is recommended.

Changes in serum PBB and PCB levels over time among women of varying ages at exposure.

The identification of host factors that are predictors of changes in serum polyhalogenated biphenyl contaminants over time has been a difficult challenge in epidemiologic studies of exposed individuals. Of particular concern are age at exposure, reproductive and lactational histories, and changes in body mass index. Using both cross-sectional and longitudinal approaches, this study examined factors related to high initial serum PBB and PCB levels and changes in these levels over time among women of varying ages at exposure (n=1772; age range<1 to 45 years). In 1973, PBB exposure occurred through consumption of farm products contaminated with PBB added to cattle feed. Exposures to PCBs began in 1941 through PCB-contaminated silo sealant deteriorating into animal feed. The Michigan Department of Public Health began enrolling participants in 1977 and has continued to follow them through annual updates. At enrollment, questionnaires were administered to obtain demographic, lifestyle, and anthropometric measurements, medical/reproductive and occupational histories, and contaminated food consumption patterns. Blood samples were collected for PBB and PCB analysis at enrollment for all participants; additional serum tests were done on a subset of the population during follow-up. Median serum levels at enrollment were 2.0 ppb PBB and 5.0 ppb PCB. A decline in serum PBB level over an interval that ranged from 1 to 146 months (median=31) was observed for 44.6% of the women (median=1.0 ppb), while 12.2% showed an increase (median=1.0 ppb). PCB levels declined in 50.3% of the women (median=3.0 ppb) while 12.2% increased (median=2.0 ppb). Relative to women whose contaminant levels were stable, higher initial serum level was a predictor of decline for both PBB and PCB (OR=1.66, 95% CI 1.52-1.82; OR=3.26, 95% CI 2.58-4.12, respectively); a yearly increase in interval between tests was related to declining PCBs (OR=1.65, 95% CI 1.46-1.87). In addition, age< or =10 years at exposure (OR=1.72, 95% CI 1.03-2.86) and residence on a quarantined farm (OR=1.40, 95- CI 1.03-1.90) were predictors of a decrease in PBBs. Factors related to an increase in PBB levels were age< or =10 years at exposure (OR=0.30, 95% CI 0.10-0.96) and initial PBB level (OR=1.24, 95% CI 1.15-1.33); and for PCBs, high initial level (OR=1.34, 95% CI 1.17-1.53) and body mass index (OR=1.07, 95% CI 1.01-1.13). One or more live births during the interval between tests were not related to changing levels of either contaminant; breastfeeding data were not available for examination. Early age at exposure appears to be an important predictor of changes in serum PBB levels over time.

Survey of the Asp f 1 allergen in office environments.

Sick Building Syndrome remains a prevalent problem with patient complaints similar to typical allergy symptoms. Unlike household allergens typically found in domestic reservoirs, the allergen from a common fungus like Aspergillus fumigatus (i.e., Asp f 1) is conceivably widespread in the work environment. This project surveyed airborne levels of the Asp f 1 allergen in office and non-industrial occupational environments, as well as the dust reservoirs of A. fumigatus believed to be responsible for those levels. Airborne and bulk dust samples were collected, extracted, and assayed for Asp f 1. Concurrently, bulk dusts collected from the same locations were selectively cultured for A. fumigatus, and mesophilic fungi and bacteria. Samples were collected during both wet and dry climatological conditions from paired wet and dry building locations to examine the possibility of Asp f 1 increases due to fungal growth blooms. Very low levels of Asp f 1 were detected but only in the airborne samples (2/120 positive samples, with 3.6 ng/m3 and 1.8 ng/m3; LOD < 1.2 ng/m3). No dust samples showed even detectable traces of the allergen (LOD = 5 ng/g dust). Although A. fumigatus counts from dusts fluctuated significantly with exterior moisture events, analysis of wet versus dry period samples showed no differences in Asp f 1 levels. These results indicate that even in the presence of measurable fungal concentrations, background levels of Asp f 1 are low. Nonindustrial office buildings devoid of indoor air quality issues were not observed to have significant levels of the Asp f 1 allergen in the geographical region studied.

Safety climate and its association with injuries and safety practices in public hospitals in Costa Rica.

In response to growing concern for occupational health and safety in the public hospital system in Costa Rica, a cross-sectional survey of 1,000 hospital-based health care workers was conducted in 1997 to collect baseline data that are being used to develop worker training programs in occupational health in Costa Rica. The objectives of this survey were to: 1) describe the safety climate within the national hospital system, 2) identify factors associated with safety, and 3) evaluate the relationship between safety climate and workplace injuries and safety practices of employees. The safety climate was found to be very poor. The two most significant predictors of safety climate were training and administrative support for safety. Safety climate was a statistically significant predictor of workplace injuries and safety practices, respectively, and there was an underreporting rate of 71% of workplace injuries. These findings underscore the need for improvement of the safety climate in the public hospital system in Costa Rica.

Adolescent occupational injuries: Texas, 1990-1996.

BACKGROUND: A comprehensive surveillance system for occupational injuries to adolescents does not exist in Texas, as in most states. Therefore, the magnitude, severity, nature, and source of injuries to working adolescents have not been well described in Texas. METHODS: The investigators used three data sources to investigate work-related injuries and deaths in Texas: (1) Texas Workers' Compensation Commission (TWCC) claims data from 1991 through April 1996; (2) 1993 TWCC/Bureau of Labor Statistics (BLS) Annual Survey of Occupational Injuries and Illnesses; and (3) work-related fatalities identified from Texas death certificates from 1990-1995. RESULTS: There were 9,027 injuries reported to the TWCC for adolescents 14-17 years of age during slightly more than 5 years. Injuries for which indemnity payments were made (more than 7 days out of work) occurred among 21.7% of the adolescents. Based on BLS data in 1993, of 992 non-fatal injuries involving days away from work, 35% were caused by contact with objects, 27% by bodily reaction, and 24% by falls. Two-thirds of these injuries occurred while working in eating and drinking places and grocery stores. Three-quarters of the 30 deaths from 1990-1995 were accounted for equally by motor vehicle and homicide. CONCLUSIONS: In conclusion, a substantial number of adolescents are injured or killed in the workplace each year in Texas. Although improved population-based surveillance is needed, sufficient knowledge exists to begin prevention efforts now.

Cancer among a Michigan cohort exposed to polybrominated biphenyls in 1973.

The long-term health effects of human exposure to polybrominated biphenyls are not known. In this nested case-control study, we evaluated the association between site-specific cancer risk and serum polybrominated biphenyl levels among a Michigan cohort accidentally exposed to polybrominated biphenyls in 1973. The Michigan Department of Public Health has followed 3,899 people through 1993, among whom 195 primary cancers were identified in 187 persons. Controls were 696 randomly selected cancer-free individuals who were frequency matched to cases by sex and age (in 5-year strata). Baseline serum polybrominated biphenyl levels were measured using standard methods. We found an increasing dose-response relation for digestive system cancer risk with higher serum polybrominated biphenyl category [4-20 parts per billion (ppb), 21-50 ppb, and > 50 ppb] after adjustment for age, family cancer history, cigarette smoking, alcohol drinking, and baseline serum polychlorinated biphenyl level. Adjusted odds ratios (ORs) for each category were 8.23 [95% confidence interval (CI) = 1.27-53.3], 12.3 (95% CI = 0.80-191), and 22.9 (95% CI = 1.34-392), respectively. Univariate analysis for polybrominated biphenyl level and lymphoma risk also showed a dose-response relation, with corresponding ORs of 3.24 (95% CI = 0.24-95.9), 20.5 (95% CI = 1.51-608), and 32.6 (95% CI = 3.33-861).

A system linking occupation history questionnaire data and magnetic field monitoring data.

A method is presented which links on-site electromagnetic field monitoring data with pre-existing work history data. The linkage is used to estimate cumulative and average annualized magnetic field exposure for a case-control study. On-site electromagnetic field monitoring data for 1,966 volunteer utility employees, at 59 sites in the United States and three other countries, were obtained from a large project (the EMDEX project) designed to collect, analyze, and document 60-Hz electric and magnetic field exposures for a diverse population. These data represent 9 primary work environments, and 16 job classification categories, amounting to 144 unique job categories which were consolidated using the job-exposure matrix presented into 282 three-digit Dictionary of Occupational Title (DOT) codes. The DOT code categories were then linked to lifetime occupational histories from a case-control study of leukemia. The method may be extended to link additional job titles with monitoring information. Job titles linked with electromagnetic field monitoring information provide more specific estimates of exposure intensity than previous ordinal estimates of exposure. Therefore, estimates of cumulative electromagnetic field exposure are achievable, as well as high and low level exposure estimates.

Is there transplacental transfer of asbestos? A study of 40 stillborn infants.

An autopsy study was conducted to investigate whether there is transplacental transfer of asbestos in humans. The asbestos burden of lung, liver, skeletal muscle, and placenta digests of 40 stillborn infants was determined using a bleach digestion method. The fibers detected in the tissue digests were characterized as to the type of asbestos, using electron microscopy, energy-dispersive x-ray analysis, and selected-area diffraction analysis. Placental digests of 45 full-term, liveborn infants were similarly processed as controls. Low levels of small, thin, uncoated asbestos fibers were detected in the placentas and organs of 37.5% of the stillborn infants (15 of 40). The fiber sizes ranged from 0.05 to 5.0 microns in length and 0.03 to 0.3 micron in width, with a mean length of 1.15 microns and a mean width of 0.069 micron. Maximum numbers of fibers were found in the lungs (mean 235,400 fibers/g; n = 10), followed by liver (mean 212,833 fibers/g; n = 6), placenta (mean 164,500 fibers/g; n = 4), and skeletal muscle (80,000 fibers/g; n = 1). The fibers were detected at all stages of gestation and showed no association with gestational age. A significant association was found between fiber presence and working mothers, and positive but nonsignificant associations were found with maternal history of drug abuse, previous abortions, and fetal maceration. No association was found between premature rupture of membranes and fiber presence. No fibers were detected in the 45 placentas of the liveborn control infants. There was a highly significant difference in the asbestos fiber counts of the placentas of the stillborn and liveborn infants (P < .001). Our studies demonstrate the presence of short and thin asbestos fibers in stillborn infants and their positive association with working mothers.

Diurnal and gestational patterns of uterine activity in normal human pregnancy. The Uterine Activity in Pregnancy Working Group.

OBJECTIVES: To define the profile of 24-hour uterine activity in normal pregnancy and to correlate contraction frequency with physical activity and emotional stress diaries. METHODS: One hundred nine low-risk pregnant women who delivered at term recorded uterine contractions for 24 hours twice weekly from 20-40 weeks' gestation using an ambulatory monitor and kept a physical activity and emotional stress diary. Contractions per hour were calculated for each hour of the day and week of gestation, and related to physical activity and emotional stress. RESULTS: We analyzed 71,683 hours. No contractions were recorded in 73% of the hours, and fewer than four contractions per hour occurred in 96%. Significant inter-individual variability was noted. Contractions increased markedly with gestational age: The 95th percentile was 1.3 contractions per hour at 21-24 weeks, 2.9 at 28-32 weeks, and 4.9 at 38-40 weeks. A strong clustering of contractions occurred at night, which became pronounced after 24 weeks (night:day ratio 2:1 at 28-32 weeks). To adjust for the effects of gestational age and time of day, contractions per hour were converted to gestation- and hour-specific percentiles ("contraction percentiles"). Rest was associated with a fall in contraction percentile by 1.25, whereas coitus increased the contraction percentile by 5.52 (P < .05). No changes were noted with emotional stress. CONCLUSIONS: This study provides normative contraction data in uncomplicated pregnancy. A strong diurnal rhythm is present from 24 weeks onward, with 67% of contractions occurring at night. Contractions per hour increase with gestational age but rarely exceed three per hour before term. Rest and sexual activity have small but measurable effects on contraction frequency.

Decision latitude, psychologic demand, job strain, and coronary heart disease in the Western Electric Study.

The hypothesis that low decision latitude and high psychologic demand are associated with an increased risk of the incidence of and mortality from coronary heart disease was investigated in a 25-year follow-up study of 1,683 men aged 38-56 years who participated in the Chicago Western Electric Study (1957-1983). Scores for decision latitude and psychologic demand, which had been linked to the 1960 US Census occupation codes, were assigned to men in the Western Electric cohort based on job title at the initial examination (1957-1958). After adjustment for major coronary risk factors, the relative risk for 25-year coronary death was 0.76 (95% confidence interval (CI) 0.59-1.00) for a 20-point increase in the decision latitude score (approximate difference between tertiles) and was 0.78 (95% CI 0.48-1.26) for a 10-point increase in the psychologic demand score (approximate difference between three groups). For job strain (defined by low decision latitude and high psychologic demand), it was 1.40 (95% CI 0.92-2.14). Controlling for occupational class reduced the magnitude of the relative risks between job characteristics and coronary mortality. Analysis stratified by occupational class indicated that the effect of decision latitude was more pronounced for white-collar than for blue-collar workers. This study provided only limited evidence for associations between job characteristics and coronary heart disease mortality.

Microcomputer-assisted data management in a case-comparison study.

A system of programs which process data on a microcomputer for a case/comparison study is described. The procedures process the data from the abstracted case source records, to control selection, interview data management, and the selection of data subsets for analysis. The capabilities of various data processing modules are outlined, and cost estimates of an existing implementation are discussed. The microcomputer is presented as an alternative to mainframe data management.