Perception versus Reality: The Relationship between Subjective and Objective Measures of Sleep When On-call under Simulated Laboratory Conditions

BACKGROUND

On-call working arrangements have been shown to negatively impact sleep. However, workers may perceive their sleep to be worse than it actually is. The aim of this study was to compare participants' pre- and post-sleep estimates of sleep duration and sleep quality with objectively measured sleep when on-call under laboratory conditions.

PARTICIPANTS

72 healthy, adult males.

METHODS

Analyses were performed on three interrelated studies, all of which consisted of four nights in a sleep laboratory. Following adaptation and baseline nights were two on-call nights (sleep opportunity 23:00 h - 07:00 h). Before and after each sleep opportunity, participants provided subjective estimates of sleep. Sleep was objectively measured using polysomnography.

RESULTS

Estimated sleep duration (6.74 ± 1.13 h) and sleep onset latency (20.55 ± 14.85 min) were significantly poorer than objectively measured sleep outcomes (sleep duration 7.21 ± 1.25 h; sleep latency 13.20 ± 10.06 min). Of the variance in post-sleep estimated sleep duration, 14% was associated with objectively measured minutes of N3 (R²Δ = 0.55) and REM (R²Δ = 0.75). Additionally, 14% of post-sleep sleep quality estimation variance was associated with minutes of N2 (R²Δ = 0.60) and N3 (R²Δ = 0.79), measured by polysomnography.

CONCLUSIONS

Some objective measures of sleep were associated with subjective estimates of sleep duration and sleep quality. However, individuals may overestimate sleep onset latency and underestimate sleep duration during on-call periods. It may be beneficial for on-call workers to actively reflect on feelings of fatigue/alertness for workplace fatigue management, rather than relying solely on estimates of sleep.

Development of the sexually dimorphic nucleus of the preoptic area and the influence of estrogen-like compounds

One of the well-defined sexually dimorphic structures in the brain is the sexually dimorphic nucleus, a cluster of cells located in the preoptic area of the hypothalamus. The rodent sexually dimorphic nucleus of the preoptic area can be delineated histologically using conventional Nissl staining or immunohistochemically using calbindin D28K immunoreactivity. There is increasing use of the bindin D28K-delineated neural cluster to define the sexually dimorphic nucleus of the preoptic area in rodents. Several mechanisms are proposed to underlie the processes that contribute to the sexual dimorphism (size difference) of the sexually dimorphic nucleus of the preoptic area. Recent evidence indicates that stem cell activity, including proliferation and migration presumably from the 3^rd ventricle stem cell niche, may play a critical role in the postnatal development of the sexually dimorphic nucleus of the preoptic area and its distinguishing sexually dimorphic feature: a signifi-cantly larger volume in males. Sex hormones and estrogen-like compounds can affect the size of the sexually dimorphic nucleus of the preoptic area. Despite considerable research, it remains un-clear whether estrogen-like compounds and/or sex hormones increase size of the sexually dimor-phic nucleus of the preoptic area via an increase in stem cell activity originating from the 3^rd ventricle stem cell niche.

"Awake, smoky, and hot": providing an evidence-base for managing the risks associated with occupational stressors encountered by wildland firefighters

To curtail the spread of wildfire, firefighters are often required to work long hours in hot, smoky conditions with little rest between consecutive shifts. In isolation, heat, smoke, and sleep disruption can have a detrimental impact on cognitive and physical abilities. Far less is known, however, about the combined impact that heat, smoke, and sleep disruption can have on firefighters' performance during wildfire suppression or on human performance in general. The available literature, though scant, suggests that audio and visual tracking may be degraded after sustained heat exposure following one night of sleep deprivation. Exposure to heat and carbon monoxide, in contrast, appears to have only limited impact on cognitive performance, even after physical exercise. Heat and carbon monoxide exposure does, however, increase physiological exertion to a given work or exercise bout. To the authors' knowledge, there are no published studies that have explored the impacts of heat exposure following sleep disruption on physical work performance, sleep disruption and smoke exposure on physical or cognitive work, or the combined impacts of sleep disruption, smoke and heat exposure on cognitive or physical work. While more integrative research is needed, the current review provides a summary of the available evidence and an indication of the degree of confidence agencies can have in the research. This will allow both the scientific community and agencies to make informed recommendations regarding the management of wildland firefighters' health and safety on the fireground.

Changes in structural aspects of mood during 39-66 h of sleep loss using matched controls

A number of studies have described mood change during sleep loss in the laboratory, however, an understanding of fluctuations in structural aspects of mood under such conditions is lacking. Sixty-two healthy young adults completed one of three possible conditions: one (n = 20) or two (n = 23) nights of sleep loss or the control condition which consisted of one (n = 9) or two (n = 10) nights of 9 h time in bed. The Mood Scale II was completed every two waking hours and data were analysed in terms of the frequency and intensity of mood reports. Overall, sleep loss conditions were associated with significantly less frequent happiness and activation and more frequent fatigue reports (p < 0.001). Intensity was also significantly reduced for activation and happiness, and increased for depression, anger and fatigue (p < 0.05). Interestingly, there were no significant differences in anger following two nights in the laboratory with or without sleep. Further, two nights in the lab with normal sleep was associated with significant increases in depression intensity (p < 0.05). Findings support the hypothesis of a mood regulatory function of sleep and highlight the relative independence of frequency and intensity and of positive and negative mood dimensions. Findings also suggest that the laboratory environment, in the absence of sleep loss, may have a significant negative impact on mood.

Serum levels of albumin, triglycerides, total protein and glucose in rats are altered after oral treatment with low doses of 13-cis-retinoic acid or all-trans-retinoic acid

Currently used to treat severe acne, 13-cis-retinoic acid (13-cis-RA) is under investigation for its anticancer effects as is the isomer, all-trans-retinoic acid (all-trans-RA). Here, the effects of oral 13-cis-RA or all-trans-RA treatment on serum chemistry, leptin and adiponectin levels were evaluated. Adult Sprague-Dawley rats were gavaged once daily for 7 consecutive days with 13-cis-RA (7.5 or 15 mg kg(-1)), all-trans-RA (10 or 15 mg kg(-1)) (n=24/sex/dose), or soy oil (n=16/sex) and blood was sampled 30-480 min after the last gavage. The body weight was unaffected; however, the liver/body weight ratios were increased by both doses of all-trans-RA. Sex differences were noted for levels of cholesterol, creatine, triglycerides, albumin, alanine aminotransferase and total protein. Both doses of all-trans-RA reduced albumin levels to approximately 90% of the control and total protein levels to approximately 93% of the control while substantially elevating triglyceride levels to approximately 66%-99% above the control. Additionally, triglyceride levels of the 15 mg kg(-1) 13-cis RA group were approximately 62% higher than the controls and total protein levels were approximately 5% less. Glucose levels were affected by sex and RA treatment in that males treated with 15 mg kg(-1) of 13-cis-RA or 10 mg kg(-1) all-trans-RA had lower (13%-19%) levels than the same-sex controls; however, females were not similarly affected. Neither 13-cis-RA nor all-trans-RA treatment had significant effects on the levels of blood urea nitrogen, aspartate amino transferase, leptin or adiponectin. On a mg kg(-1) basis, all-trans-RA was more potent than 13-cis-RA. These results replicate previous findings of RA-induced increased triglyceride levels. Additionally, several new findings indicate there may be sex-specific effects of RA treatment. Finally, neither treatment appeared to alter the typical diurnal cycles of these endpoints.

Long term dietary methoxychlor exposure in rats increases sodium solution consumption but has few effects on other sexually dimorphic behaviors

Methoxychlor is an insecticide with estrogen-like activity, thus exposure during development might cause sexually dimorphic behavioral alterations. To evaluate this, pregnant rats consumed diets containing 0, 10, 100 or 1000 ppm methoxychlor from gestational day 7, and offspring continued on these diets until postnatal day (PND) 77. Assessments of sexually dimorphic behaviors in offspring indicated that intake of a 3.0% sodium chloride solution was significantly increased (41%) in males and females of the 1000 ppm group. No treatment group differed from controls in open field nor running wheel activity, play behavior, nor 0.3% saccharin solution intake. Offspring of the 1000 ppm group showed significantly decreased body weight, reaching 17% less than controls at PND 77, but not clearly related to their salt solution intake. During pregnancy, 1000 ppm dams consumed 23% less food and weighed 10% less than controls, but this did not affect litter outcomes. These results indicate that in rodents, developmental and chronic exposure to dietary methoxychlor alters the sexually dimorphic behavior of salt-solution intake in young adults of both sexes. Similar behavioral alterations with other xenoestrogens, and the potential for interactions among xenoestrogens, suggest that this report may minimize the true effects of dietary methoxychlor exposure.

Validity and reliability of sincerity test for dynamic trunk motions

PURPOSE

Marras et al. developed a technique to evaluate sincerity of effort during dynamic trunk motion performance. The validity and reliability of the technique have not been evaluated. Therefore, the objective of this study was to first determine whether or not a sincerity of effort measure correctly identified those giving a sincere effort in a blinded randomized control trial and second to quantify inter-rater and test-retest reliability.

METHODS

This article reports the findings of a two phase study. In phase one, the blinded evaluation, participants were randomly assigned to either a sincere or insincere performance condition. An examiner tested participants without knowledge of the participant's group membership. In the second phase, two examiners evaluated each participant twice to quantify inter-rater and test-retest reliability.

RESULTS

In the blinded phase the specificity was 100% and sensitivity was 90% for identifying sincere and insincere effort, respectively. Phase two results showed no significant difference in probability of sincere effort between raters or between testing sessions.

CONCLUSION

A performance criterion that accurately identifies sincere vs insincere group membership during functional evaluations was identified. There were no significant differences between raters or between testing sessions. These findings indicate that this test is reliable and possesses good predictive validity in assessing sincerity of effort.

The impact of roster changes on absenteeism and incident frequency in an Australian coal mine

BACKGROUND

The occupational health and safety implications associated with compressed and extended work periods have not been fully explored in the mining sector.

AIMS

To examine the impact on employee health and safety of changes to the roster system in an Australian coal mine.

METHODS

Absenteeism and incident frequency rate data were collected over a 33 month period that covered three different roster schedules. Period 1 covered the original 8-hour/7-day roster. Period 2 covered a 12-month period under a 12-hour/7-day schedule, and period 3 covered a 12-month period during which a roster that scheduled shifts only on weekdays, with uncapped overtime on weekends and days off (12-hour/5-day) was in place. Data were collected and analysed from the maintenance, mining, and coal preparation plant (CPP) sectors.

RESULTS

The only significant change in absenteeism rates was an increase in the maintenance sector in the third data collection period. Absenteeism rates in the mining and CPP sectors were not different between data collection periods. The increase in the maintenance sector may be owing to: (1) a greater requirement for maintenance employees to perform overtime as a result of the roster change compared to other employee groups; or (2) greater monotony associated with extended work periods for maintenance employees compared to others. After the first roster change, accident incident frequency decreased in the CPP sector but not in the other sectors. There was no effect on incident frequency after the second roster change in any sector.

CONCLUSIONS

The current study did not find significant negative effects of a 12-hour pattern, when compared to an 8-hour system. However, when unregulated and excessive overtime was introduced as part of the 12-hour/5-day roster, absenteeism rates were increased in the maintenance sector. The combination of excessive work hours and lack of consultation with employees regarding the second change may have contributed to the overall negative effects.

Rationale for graduated licensing and the risks it should address

The increased crash risk of young, beginning drivers has long been cause for concern. Graduated licensing systems, which seek to phase in driving experience gradually over time, have recently been adopted by many states in an effort to reduce these risks. In an attempt to define the basic rationale for graduated licensing, relevant research evidence that describes the conditions under which risk is known to be increased for young drivers was reviewed. Potential changes in licensing laws that best address these known risk factors are described. It was found that certain situations contribute to even greater crash risk, most notably nighttime driving and driving with passengers in the peer group. The underlying premise for graduated licensing is that while crash risk of young drivers is heightened under all situations, some situations are more or less risky than others. If experience can be gained initially under lower risk conditions, both in the learning stage and when first licensed, crash risk will be reduced.

Older driver involvements in police reported crashes and fatal crashes: trends and projections

OBJECTIVES

Older drivers have become a larger part of the driving population and will continue to do so as the baby boomers reach retirement age. The purpose of this study was to identify the potential effects of this population increase on highway safety.

METHODS

Driver involvement rates for all police reported crashes were calculated per capita, per licensed driver, and per vehicle-mile of travel for 1990 and 1995. Also, driver involvement rates for fatal crashes were calculated for 1983, 1990, and 1995. Based on current crash rates per licensed driver and estimates of the future number of licensed drivers, projections of crashes involving drivers aged 65 and older were made for years 2010, 2020, and 2030.

RESULTS

Driver crash involvement rates per capita decreased with age, but fatal involvement rates per capita increased starting at age 70. The same pattern existed for involvement rates per licensed driver. For both all crashes and fatal crashes, involvement rates per mile driven increased appreciably at age 70. Using projections of population growth, it was estimated that for all ages there will be a 34% increase in the number of drivers involved in police reported crashes and a 39% increase in the number involved in fatal crashes between 1999 and 2030. In contrast, among older drivers, police reported crash involvements are expected to increase by 178% and fatal involvements may increase by 155% by 2030. Drivers aged 65 and older will account for more than half of the total increase in fatal crashes and about 40% of the expected increase in all crash involvements; they are expected to account for as much as 25% of total driver fatalities in 2030, compared with 14% presently.

CONCLUSIONS

By most measures, older drivers are at less risk of being involved in police reported crashes but at higher risk of being in fatal crashes. Although any projections of future crash counts have inherent uncertainty, there is strong evidence that older drivers will make up a substantially larger proportion of drivers involved in fatal crashes by 2030 because of future increases in the proportion of the population aged 65 and older, and trends toward increased licensure rates and higher annual mileage among older persons. Countermeasures to reduce the anticipated death toll among older drivers should address the increased susceptibility to injury of older vehicle occupants in crashes.

Spinal loading when lifting from industrial storage bins

The study documented three-dimensional spinal loading during lifting from an industrial bin. Two lifting styles and two bin design factors were examined in Phase I. The lifting style measures in Phase I were one hand versus two hand and standing on one foot versus two feet. The bin design variables were region of load in the bin and bin height. The Phase II study examined one-handed lifting styles with and without supporting body weight with the free hand on the bin as well as region and the number of feet. Twelve male and 12 female subjects lifted an 11.3 kg box from the bin. Spinal compression, lateral shear and anterior - posterior shear forces were estimated using a validated EMG-assisted biomechanical model. Phase I results indicated that the bin design factor of region had the greatest impact on spinal loading. The upper front region minimized spinal loading for all lifting styles. Furthermore, the lifting style of two hands and two feet minimized spinal loading. However, comparing Phase I two-handed lifting with Phase II one-handed supported lifting, the one-handed supported lifting techniques had lower compressive and anterior - posterior shear loads in the lower regions as well as the upper back region of the bin. A bin design that facilitates lifting from the upper front region of the bin reduces spinal loading more effectively than specific lifting styles. Furthermore, a bin design with a hand hold may facilitate workers using a supported lifting style that reduces spinal loading.

Minimal effects from developmental exposure to St. John's wort (Hypericum perforatum) in Sprague-Dawley rats

Increasing widespread use of St. John's Wort (SJW, Hypericum perforatum) has led to concerns about its use in pregnant women. Behavioral and physiological alterations resulting from developmental treatment were investigated in Sprague-Dawley rats exposed to diets containing 0, 180, 900, 1800 or 4500ppm SJW beginning on gestational day 3 and ending at offspring weaning on postnatal day (PND) 21. These dietary doses span 1-25 times the recommended human dose. Post-weaning behavioral assessments of male and female offspring included: open field activity, acoustic startle, performance of complex and Morris water mazes, and activity in an elevated plus-maze. There were no SJW effects on maternal weight gain or duration of gestation; offspring body weights were similar to controls from PND 2 through PND 56 after which, some treated groups weighed significantly less than the controls. There were no SJW-related behavioral alterations on any measure. Whole and regional brain weights of offspring at adulthood indicated no significant effects of SJW. These results indicate that there are few neurobehavioral alterations resulting from developmental SJW treatment in rats.

L-ephedrine-induced neurodegeneration in the parietal cortex and thalamus of the rat is dependent on hyperthermia and can be altered by the process of in vivo brain microdialysis

Multiple doses of the dietary supplement L-ephedrine can cause severe hyperthermia and modest dopamine depletions in the rat brain. Since D-amphetamine treatment can result in neurodegeneration, the potential of L-ephedrine to produce similar types of degeneration was investigated. Adult male rats, some implanted in the caudate/putamen (CPu) for microdialysis, were given four doses of 25 mg/kg L-ephedrine or 5 mg/kg D-amphetamine (2 h between doses) at an ambient temperature of 23 degrees C. L-ephedrine-induced degeneration in the forebrain was dependent on the degree of hyperthermia. Layer IV of the parietal cortex was the most sensitive to L-ephedrine treatment with peak body temperatures of at most 40.0 degrees C necessary to produce degeneration. Extensive neurodegeneration in the parietal cortex after L-ephedrine treatment was as pronounced as that previously described for D-amphetamine treatment and also occurred in the intralaminar, ventromedial and ventrolateral thalamic nuclei in rats with severe hyperthermia (peak body temperatures>41.0 degrees C). The neurodegeneration induced by L-ephedrine may have resulted in part from excitotoxic mechanisms involving the indirect pathways of the basal ganglia and related areas. No differences were observed between microdialysis and non-implanted rats with respect to degree of tyrosine hydroxylase (TH) loss in the CPu after either D-amphetamine or L-ephedrine treatment. However, neurodegeneration resulting from D-amphetamine and L-ephedrine was reduced in the microdialysis animals in the hemisphere ipsilateral to the probe, which raises concerns when using the technique of in vivo microdialysis to evaluate neurodegeneration. The results of this study, in conjunction with human clinical evaluation of ephedrine neurotoxicity, indicate that regionally specific damage may occur in the cortex of some humans exposed to ephedrine in the absence of stroke or hemorrhage.

Spine loading characteristics of patients with low back pain compared with asymptomatic individuals

STUDY DESIGN

Patients with low back pain and asymptomatic individuals were evaluated while performing controlled and free-dynamic lifting tasks in a laboratory setting.

OBJECTIVE

To evaluate how low back pain influences spine loading during lifting tasks.

SUMMARY OF BACKGROUND DATA

An important, yet unresolved, issue associated with low back pain is whether patients with low back pain experience spine loading that differs from that of individuals who are asymptomatic for low back pain. This is important to understand because excessive spine loading is suspected of accelerating disc degeneration in those whose spines are damaged already.

METHODS

In this study, 22 patients with low back pain and 22 asymptomatic individuals performed controlled and free-dynamic exertions. Trunk muscle activity, trunk kinematics, and trunk kinetics were used to evaluate three- dimensional spine loading using an electromyography- assisted model in conjunction with a new electromyographic calibration procedure.

RESULTS

Patients with low back pain experienced 26% greater spine compression and 75% greater lateral shear (normalized to moment) than the asymptomatic group during the controlled exertions. The increased spine loading resulted from muscle coactivation. When permitted to move freely, the patients with low back pain compensated kinematically in an attempt to minimize external moment exposure. Increased muscle coactivation and greater body mass resulted in significantly increased absolute spine loading for the patients with low back pain, especially when lifting from low vertical heights.

CONCLUSIONS

The findings suggest a significant mechanical spine loading cost is associated with low back pain resulting from trunk muscle coactivation. This loading is further exacerbated by the increases in body weight that often accompany low back pain. Patient weight control and proper workplace design can minimize the additional spine loading associated with low back pain.

The effects of a roster schedule change from 8- to 12-hour shifts on health and safety in a mining operation

The current study examined the impact on employee health and safety of changes to the roster system of an Australian coal mine. Absenteeism and incident frequency rate data were collected over a 33-month period that covered three different roster schedules, an 8-hour system, a 12-hour system and a 12-hour system incorporating unregulated overtime. The first change was implemented after consultation with the employee population, whereas the second was not. There were no significant negative effects of the 12-hour pattern, when compared to the 8-hour system. However, when unregulated and excessive overtime was introduced as part of the second round of changes, absenteeism rates were increased in one sector of the mine. The maintenance sector was subject to a significant increase in absenteeism rates, which may have been attributable to the excessive overtime required of the workers in that area. It is important that overtime be strictly monitored and that the employee population are involved in the process of roster change.

No alterations in the performance of two interval timing operant tasks after alpha-difluoromethylornithine (DFMO)-induced cerebellar stunting

The cerebellum is critically involved in temporal processes in the millisecond range and may be involved in longer time estimations (i.e. in the seconds range). Estimates in the millisecond range are impaired after developmentally induced cerebellar alterations, however, little is known about the effects of similar alterations on longer timing performance. Appropriately timed DFMO treatment reliably causes cerebellar stunting in rats, however, its effects on temporal estimation performance are unknown. Here, male and female Sprague-Dawley rats were treated with subcutaneous injections of 500 mg/kg DFMO on postnatal days 5-12, causing a 10% cerebellar weight reduction at adulthood. As adults, subjects were tested under one of two paradigms - a differential reinforcement of low response rate (DRL) task requiring that subjects withhold a lever press response for 10-14 s or a temporal response differentiation (TRD) task requiring that subjects maintain a lever press response for 10-14 s. Training and steady-state performance of the DRL and TRD tasks were not significantly altered by DFMO treatment. Performance after acute challenges with two dopaminergic agonists (2.00-7.50 mg/kg methylphenidate and 0.10-1.00 mg/kg d-amphetamine) was measured after which all subjects underwent behavioral extinction. Generally, performance after methylphenidate and d-amphetamine was similar in control and DFMO-treated rats and DFMO treatment had no differential effects on performance during extinction. These results support findings from an earlier study [Ferguson SA, Paule MG, Holson RR. Neonatal dexamethasoneon day 7 in rats causes behavioral alterations reflective of hippocampal, but not cerebellar, deficits. Neurotoxicol Teratol, 2001; 23:57-69] indicating that developmental cerebellar stunting has few effects on time estimation within the range of seconds.

Perceptions of labour pain by mothers and their attending midwives

AIMS

The aim of the current study was to examine the perception of pain by labouring women and their attendant midwife, from the onset of labour to delivery.

RATIONALE

Accurate measurement and appropriate management of pain is a significant problem for attendant medical and nursing personnel. Both the experience and perception of pain are regarded as subjective and are therefore difficult to measure objectively. Indeed, much of the literature reports that pain is often under- or over-estimated by nursing staff who as a consequence consistently fail to administer adequate analgesia. Few studies have specifically examined the ability of midwives to assess the pain of labouring women.

DESIGN

The short form McGill Pain Questionnaire (SF-MPQ), routinely used to assess pain in obstetric environments, was used to determine pain perception. Thirteen labouring women and nine midwives completed the SF-MPQ every 15 minutes beginning at the time of admittance to the delivery suite. Peak pain ratings for the preceding 15 minutes were obtained without reference to prior ratings or each other's scores. Further, midwives in the maternity unit of The Queen Elizabeth Hospital (TQEH), Adelaide, South Australia completed a survey investigating the cues they use to assess pain during labour.

RESULTS

On each measure of pain on the SF-MPQ, the midwives scores correlated with the mothers' scores across the entire pain range. Further analysis showed that mothers' and midwives' pain scores were similar at mild-moderate pain levels, but midwives significantly underestimated pain intensity at levels that mothers described as severe. The survey responses indicated that midwives rely on both verbal and nonverbal cues to assess pain levels.

CONCLUSIONS

The cues used by midwives to differentiate pain intensities and qualities are similar to those used in other clinical settings, but may have limited discriminatory value as pain levels become severe.

Gender-based differences in rats after chronic dietary exposure to genistein

Gender-based differences can be observed from pharmacokinetic, behavioral, or anatomical assessments. No single assessment tool will provide a complete answer, but the use of a variety of indices, each with known gender-related outcome differences, can reveal agent-induced gender-based alterations. In a series of initial range-finding studies in rats conducted at the National Center for Toxicological Research (NCTR), the effects of dietary exposure to the weak estrogen, genistein, have been assessed using a number of techniques with validated gender-related outcome measures. The findings indicated that (1) the internal dose of genistein was higher in females than males after equivalent dietary exposure and this was consistent with the faster rate of genistein elimination in males; (2) in behavioral assessments, males and females in the high-dose dietary genistein group consumed more of a sodium-flavored solution; however, no genistein-related changes were observed in open field or running wheel activity, play behavior, or intake of a saccharin-flavored solution; and (3) dose-related alterations of the volume of the sexually dimorphic nucleus of the medial preoptic area were observed in genistein-exposed male rats but not females. These observations describe the utility of a variety of gender-based assessment tools and indicate that dose-related effects of developmental and chronic dietary exposure to genistein can be observed in the rodent. Additional studies, perhaps in nonhuman primates, are necessary to further predict the effect(s) of genistein on human gender-based development.

Localized oxygen use of healthy and low back pain individuals during controlled trunk movements

Individuals who have low back pain (LBP) have significantly different motion characteristics than healthy individuals. However, the cause of these differences is unknown. Oxygen use of the erector spinae muscle was examined while simultaneously monitoring motion characteristics to determine whether oxygen use differed between healthy and LBP individuals. Thirty volunteers were classified as healthy, structural, or muscular-based LBP. A near-infrared spectrometer monitored oxygen use and blood volume in the lumbar region. Results showed significant differences in oxygen use but not blood volume between healthy and LBP subjects with muscular-based disorders. Inability of the muscular group to use oxygen in a manner similar to the healthy group indicates different processes at the tissue level, indicating that differences in oxygen use may provide insight into why motion patterns differ between healthy and LBP groups.

Prenatal fumonisin (FB1) treatment in rats results in minimal maternal or offspring toxicity

To investigate the neurobehavioral and developmental effects of the mycotoxin, FB1, Sprague-Dawley rats were treated with FB1 on gestational days 13-20. In Experiment 1, FB1 was obtained from culture material and pregnant rats were gavaged with 0, 0.8 or 1.6 mg/kg. In Experiment 2, pregnant rats were gavaged with purified FB1 at doses of 0, 1.6 or 9.6 mg/kg. Offspring were evaluated on a battery of behavioral tests as well as measures of whole and regional brain weight. There were no effects on maternal weight gain, reproductive outcomes, or offspring body weight through adulthood in either experiment. Complex maze performance, open field and running wheel activity were not altered by prenatal FB1 treatment. In Experiment 2, acoustic startle response was depressed at two ages during the first or second block of 9 trials in males treated with purified FB1. Females exhibited no such alterations. Play behavior at PND 33, but not PND 26, was increased in males prenatally treated with 9.6 mg/kg relative to those treated with 1.6 mg/kg. There were no substantive treatment effects on regional brain weight. These results suggest that doses of < or = 9.6 mg purified FB1/kg and/or < or = 1.6 mg FB1/kg obtained from culture material cause minimal maternal toxicity and produce few development functional alterations. In addition, potential FB1-related functional alterations were evident only in males providing further support for a mild sex-specific effect for fumonisin.

Behavioral responses of rats exposed to long-term dietary vinclozolin

Vinclozolin is a fungicide used on food crops with human exposure estimated at approximately 2 microg/kg/day from ingestion; occupational exposure, however, may be greater. The metabolites of vinclozolin have been reported to act as antiandrogens and have adverse effects on reproductive physiology and behavior in animals. Here, pregnant rats were fed soy-free diets containing 0, 10, 150, or 750 ppm of vinclozolin (approximately 0, 0.8, 12, and 60 mg/kg/day for an adult) beginning on gestational day 7, and offspring were continued on these diets through sacrifice at postnatal day 77. Male and female offspring were assessed for changes in several nonreproductive sexually dimorphic behaviors: open field and running wheel locomotor activity, play behavior, and consumption of saccharin- and sodium chloride-flavored solutions. There was a significant interaction of sex with vinclozolin exposure on running wheel activity, which indicated that females in the high-dose exposure group were hypoactive compared to same-sex controls. There was a significant overall effect of vinclozolin exposure on fluid consumption, and high-dose animals showed increased intake of the saccharin solution and decreased intake of plain water while saccharin was available. Effects were more pronounced in females, which drank 40.8% more saccharin than control females, whereas males drank 6.2% more than control males. There were no effects of vinclozolin treatment on play behavior or sodium solution intake. Gestational duration, total and live pups per litter, litter sex ratios, and birth weight were also not significantly affected, nor were body weight and food intake for dams and offspring. These results indicate that long-term dietary exposure to vinclozolin does not have severe toxicological consequences on the nonreproductive behaviors measured here. However, exposure may cause subtle alterations in locomotor activity and consumption of saccharin-flavored solution.

Relationship of parent driving records to the driving records of their children

Many studies have shown that young driver crash rates can be influenced by such factors as lifestyle characteristics and licensing systems. However, the influence of parents on their teenage children's crash and violation rates has not received much attention. The present study used data from the North Carolina driver history file to match the crash and violation records of young drivers between the ages of 18 and 21 with those of their parents. Results indicate that children's driving records in the first few years of licensure are related to the driving records of their parents. Children whose parents had three or more crashes on their record were 22% more likely to have had at least one crash compared with children whose parents had no crashes. Likewise, children whose parents had three or more violations were 38% more likely to have had a violation compared with children whose parents had none. Logistic regression models showed that these relationships held when controlling for household type and child gender.

Neonatal dexamethasone on day 7 in rats causes behavioral alterations reflective of hippocampal, but not cerebellar, deficits

Developmental glucocorticoid treatment in rats has been shown to cause body and brain weight decrements concurrent with behavioral alterations. Here, Sprague-Dawley rats were treated with the synthetic glucocorticoid, dexamethasone (DEX), on postnatal day (PND) 7 (1.5 mg/kg, sc, injected in the morning and afternoon). Behavioral assessments of negative geotaxis, locomotor activity (open field, maze exploration, residential running wheel, residential figure 8 maze), open-field activity response to amphetamine, acoustic startle, prepulse inhibition (PPI) of acoustic startle, juvenile play behavior, anxiety (emergence tests), motor coordination (rotarod performance), spatial learning (Morris water maze and food-reinforced complex maze), and operant performance (time estimation and response inhibition) were assessed in male rats. Body weight was decreased beginning at PND 43 until sacrifice on PND 127. Whole and regional brain weights were less, especially hippocampus, cerebellum, brainstem, and cortical remnant. Indications of delayed development were apparent; specifically, DEX-treated rats took significantly longer to turn on PND 8, but not PND 9, in the negative geotaxis test. DEX treatment induced deficits in the Morris water maze that were similar to hippocampal deficits. Open-field activity changes were inconsistent; however, DEX-treated rats were hyperactive during the dark period in running wheel tests. There were no indications of changes in reactivity or emotionality.

Predicting recovery using continuous low back pain outcome measures

BACKGROUND CONTEXT

There is a lack of research evaluating multiple follow-up visits, specifically when using continuous outcome measures. Continuous outcome measures with several follow-up assessments would allow us to evaluate rate of recovery.

PURPOSE

To predict low back pain outcomes based on the quantification of initial conditions.

STUDY DESIGN/SETTING

This was a prospective study where patients were enrolled within the first month of low back pain symptoms and evaluated for 3 months. Patients were recruited from several primary care facilities.

PATIENT SAMPLE

Thirty-two patients with local low back pain symptoms were recruited for the study.

OUTCOME MEASURES

There were four major outcome measures, including functional performance probability, symptom intensity, impairment of activities of daily living, and a summary outcome measure.

METHODS

Regression models were constructed using the initial conditions, including psychological, psychosocial, physical workplace, and personal factors, to predict the rate of recovery for each outcome measure.

RESULTS

Twenty-eight patients completed the study. The r2 value for the rate of recovery regression models were 0.77 symptom intensity prediction, 0.85 activities of daily living prediction, 0.87 functional performance probability prediction, and 0.96 summary outcome measure prediction. Two functional performance patterns of recovery were found, including a steady improvement and a large jump in improvement. A discriminant function model identified the pattern of recovery in 91% of cases given initial conditions.

CONCLUSIONS

Continuous outcome measures can be accurately predicted given the initial conditions.

Neonatal polyamine depletion by alpha-difluoromethylornithine: effects on adenylyl cyclase cell signaling are separable from effects on brain region growth

Ornithine decarboxylase (ODC) and the polyamines play an essential role in brain cell replication and differentiation. We administered alpha-difluoromethylornithine (DFMO), an irreversible inhibitor of ODC, to neonatal rats on postnatal days 5-12, during the mitotic peak of the cerebellum, a treatment regimen that leads to selective growth inhibition and dysmorphology. In adulthood, cell signaling responses mediated through the adenylyl cyclase pathway were evaluated in order to determine if synaptic dysfunction extends to regions that appear to be otherwise unaffected by DFMO. Total adenylyl cyclase catalytic activity, evaluated with the direct enzymatic stimulant, Mn(2+), was significantly elevated in male rats both in the cerebellum and in brain regions showing no growth retardation (cerebral cortex, brainstem); there were no significant effects in females. In contrast, signaling mediated through the G proteins that couple neurotransmitter receptors to adenylyl cyclase showed a deficit in the DFMO group, as evaluated with the response to fluoride; in males, there was no corresponding increase in activity as would have been expected solely from the enhancement of adenylyl cyclase, and in females, there was actually a significant decrease in the response to fluoride. Again, the deficits were not restricted to the cerebellum. Stimulation of adenylyl cyclase by isoproterenol, a beta-adrenergic receptor agonist that acts through G(s), likewise displayed deficits in both males and females, and without distinction by brain region. These results indicate that the ODC/polyamine pathway plays a role in the development of cell signaling, and hence in neurotransmission, above and beyond its role in cell replication and differentiation. Given the fact that numerous drugs and environmental contaminants have been shown to alter ODC and the polyamines in the developing brain, our findings suggest that changes in brain region growth or structure are inadequate to predict the targeting of specific neurotransmitter or signaling pathways, and that gender-selective functional defects may be present despite the absence of morphological differences.

Multigenerational exposure to dietary genistein has no severe effects on nursing behavior in rats

The phytoestrogen and principal isoflavone in soy, genistein, has adverse effects on reproductive physiology in rodents. Since physiology and behavior are both sensitive to perturbations by estrogens, genistein may produce behavioral alterations as well. This paper reports one aspect of a study in which several adult rodent behaviors will be assessed following long term multigenerational dietary exposure to genistein. Since maternal care may affect offspring behaviors in adulthood, it is important to determine the potential for genistein to affect maternal behavior. Here, rats (F0 generation) were fed soy-free diets containing 0, 5, 100, or 500 ppm genistein (approx. 0, 0.4, 8, and 40 mg/kg/day for an adult) beginning on postnatal day (PND) 42. Two generations of offspring (F1 and F2) were continued on these diets and all treatment groups of the F3 generation were returned to 0 ppm at weaning (PND 22). In the first 3 weeks after parturition (for each generation), dams were assessed on 6 occasions for the presence of the arched back posture with at least one pup nursing. Data were analyzed by 3 way repeated measures analysis of variance (ANOVA) with generation, treatment, and postnatal day as factors, and p<0.05 required for significance. There were no significant interactions among treatment, generation, or day, and no overall effects of treatment or generation. As expected, there was a significant overall effect of day, with animals nursing less on later days (p<0.0001). As assessed here, these results suggest that lifelong and multigenerational exposure to dietary genistein has no severe effects on nursing behavior in rodents.

Developmental neurotoxicity of endocrine disrupters: focus on estrogens

A number of different environmental compounds are proposed to interact with the endocrine system (i.e., endocrine disrupters). Many of these have estrogenic effects in vitro and/or in vivo. Recent reviews have focused attention on the need for assessing the neurotoxicity of these compounds following developmental exposure. This attention comes in part from the literature on the effects of developmental exposure to exogenous estrogen on later behavioral and neuropathological alterations. A review of the ongoing neurobehavioral and neuropathological studies at the National Center for Toxicological Research on four such estrogen mimics (genistein, methoxychlor, nonylphenol, and ethinyl estradiol) is presented with results indicating that intake of a sodium solution is sensitive to these estrogen mimics. Developmental dietary exposure in male and female rats resulted in increased consumption of the sodium solution. Volume of the sexually dimorphic nucleus of the medial preoptic area was reduced by genistein, nonylphenol, and ethinyl estradiol exposure in males. The regulatory impact of these data and the directions for future research are discussed.

Attention deficit/hyperactivity disorder: characteristics, interventions and models

An epidemiological study of Attention Deficit/Hyperactivity Disorder (ADHD) suggests that the prevalence may be two to three times higher than the figure of 3-5% often cited. In addition, the data suggest that both underdiagnosis and overdiagnosis occur frequently. Rodent animal models of ADHD, like the Spontaneously Hypertensive Rat (SHR) and other rat models such as those with chemical and radiation-induced brain lesions and cerebellar stunting, and the Coloboma mouse model exhibit clear similarities with several aspects of the human disorder and should prove useful in studying specific traits. Operant behavioral tasks that model learning, short-term memory and simple discriminations are sensitive to ADHD and methylphenidate has been shown to normalize ADHD performance in a short-term memory task. Recent findings challenge not only the current postulate that response inhibition is a unique deficit in ADHD, but also the concepts of ADHD and its treatment, which presume intact perceptual abilities. Time perception deficits may account, in part, for the excessive variability in motor response times on speeded reaction time tasks, motor control problems and motor clumsiness associated with ADHD. The Multimodality Treatment Study of ADHD (MTA) provided data suggesting that pharmacological interventions that included systematic and frequent follow-up with parents and teachers, with or without psychosocial interventions, are superior to psychosocial interventions or standard community care alone. Additionally, the MTA was one of the first studies to demonstrate benefits of multimodal and pharmacological interventions lasting longer than 1 year. Imaging studies have demonstrated differences in brain areas in children with ADHD: anterior corpus callosum, right anterior white matter, and cerebellar volumes are all decreased in children with ADHD and there is less brain asymmetry in ADHD subjects. Additionally, functional imaging studies, coupled with pharmacological manipulations, suggest decreased blood flow and energy utilization in prefrontal cortex and striatum and the dysregulation of catecholamine systems in persons with ADHD.

Variations in teenage activities with and without a driver's license

High school students were surveyed every 6 months from their freshman through senior years concerning licensing, driving, and transportation to and from their various activities. Students in Delaware (learner's permit can be issued at age 15 years, 10 months; driver's license at age 16) were compared with students in Connecticut and New York (permit at age 16; license at age 16) and in New Jersey (license at age 17). During the junior year, most Delaware students, some New York and Connecticut students, and few New Jersey students were licensed. However, even during the junior year, students in the respective states did not differ significantly with respect to time spent at activities such as a paying job, homework, watching television, dating, parties, being with friends, talking on the phone, or participating in sports or school activities. Graduated licensing systems can delay full-privilege teenage licensure and reduce teenage crash rates. These systems also can increase the number of times parents and others must drive. However, the present study's results indicate that licensing delays of as much as 1 year have minimal effects on the nondriving activities of high school students.

Longitudinal quantitative measures of the natural course of low back pain recovery

STUDY DESIGN

A prospective study was developed to quantify acute low back pain recovery.

OBJECTIVE

To compare traditional self-report measures of low back pain recovery with a quantitative measure of recovery.

SUMMARY OF BACKGROUND DATA

The magnitude of low back disorders in society continues to be a problem. To prevent secondary injuries, an understanding of recovery must be gained by comparing the natural course of recovery using several outcome measures.

METHODS

For this study, 16 occupational and 16 nonoccupational patients with low back pain were recruited. Recovery was monitored prospectively every 2 weeks for 3 to 6 months, using subjective work status, pain symptoms, activities of daily living, and objective functional performance probability (trunk kinematics).

RESULTS

Return to work underestimated the percentage of subjects impaired, as compared with all other outcome measures. Symptoms, activities of daily living, and functional performance probability all showed similar patterns of recovery for 0 to 12 weeks. At 14 weeks, there was a lag in functional performance recovery. Both symptoms and activities of daily living indicated that 80% of the population was recovered, whereas functional performance indicated the figure to be 68%.

CONCLUSION

This prospective study demonstrates the natural course of recovery using several outcome measures. The objective kinematic functional performance measure of recovery quantifies a different aspect of impairment not evaluated by traditional subjective measures. Use of several outcome measures may lead to a better understanding of low back pain recovery or residual impairment, which may minimize the risk of recurrent injury.

Retinoic acid exposure on gestational days 11 to 13 impairs swallowing in rat offspring

We have previously reported that exposure to 10 mg/kg of all-trans-retinoic acid (RA) daily on the 11th, 12th, and 13th days of rat gestation is lethal to all fetuses so exposed, due to an inability to suckle [R.R. Holson et al., Neurotoxicol Teratol 19 (1997) 347-353]. Because this lethal RA effect could be due to any of a variety of causes, from olfactory problems in locating the nipple to a motor problem in sucking or swallowing, we performed the following experiment. Albino dams were exposed to 10-mg/kg RA or vehicle daily over gestational days (GDs) 11 to 13. On the afternoon of GD 21 all pups were delivered by c-section. Tongue cannulae were inserted into the oral cavity of these offspring, and used to infuse a solution of condensed milk directly into the mouth. During and after each of four infusions, the behavioral response to the infusion (typically rolling and curling) was recorded. Controls responded well to this procedure, typically swallowing all milk so infused. In contrast, almost no RA-exposed neonates were able to swallow milk infused into the oral cavity. In such cases the milk simply dribbled out of the mouth, while the stomach was found to be empty at autopsy. However, the RA-treated animals did seem aware that milk was entering their mouths, because they showed a normal behavioral response to milk infusion. We conclude that GD 11-13 retinoid lethality is due to motor not sensory problems in the control of swallowing.

Effect of Florida's graduated licensing program on the crash rate of teenage drivers

On 1 July 1996, Florida instituted a graduated licensing program for drivers younger than age 18. For the first 3 months, holders of learner's licenses are not allowed to drive at all between 19:00 and 06:00 h; thereafter, they may drive until 22:00 h. Learner's licenses must be held for 6 months prior to eligibility for the intermediate license. Sixteen-year-old intermediate license holders are not permitted to drive unsupervised from 23:00 to 06:00 h, 17 year-olds from 01:00 to 06:00 h. All drivers younger than 18 have strict limits on the number of traffic violations they can accumulate and, effective 1 January 1997, all drivers younger than 21 are subject to a zero tolerance law for drinking and driving. Florida crash data for 1995-1997 were obtained and compared with similar data from Alabama, a state that borders Florida but does not have graduated licensing. For 15, 16, and 17 year-olds combined, there was a 9% reduction in the fatal and injury crash involvement rate in Florida during 1997, the first full year of graduated licensing, compared with 1995. On a percentage basis, crashes declined most among 15 year-olds, followed by 16 year-olds and then 17 year-olds. Reductions were not seen among Alabama teenagers nor among 18 year-olds in Florida.

Maternal and offspring toxicity but few sexually dimorphic behavioral alterations result from nonylphenol exposure

Nonylphenol ethoxylates are used in the production of surfactants and are found in numerous manufactured substances. para-Nonylphenol (NP) is a suspected endocrine disruptor, exhibiting estrogen-like activity and might cause alterations with developmental exposure. To evaluate such effects, pregnant Sprague-Dawley rats consumed diets containing 0 (n = 11), 25 (n = 10), 500 (n = 10), or 2,000 (n = 9) ppm NP beginning on gestational day (GD) 7. At postnatal day (PND) 21, offspring continued on the same maternal diets until PND 77 and were evaluated for behavioral alterations (open-field activity at PNDs 22-24, 43-45, 64-66, play behavior at PND 35, running wheel activity at PND 63-77, flavored solution intake at PND 69-75). During pregnancy and lactation, dams in the 25-, 500-, and 2,000-ppm groups consumed 9 to 25% less food, which was associated with a 17% less weight gain during GDs 1 to 21 in dams of the 2,000-ppm group, although this effect was not statistically significant. Gestation duration, birth weight, sex ratio of live pups, and number of live or dead pups per litter did not differ between treatment groups. Offspring body weight and food consumption were decreased in the 2, 000-ppm group beginning at PND 28; however, an effect of feed aversion could not be eliminated. Behavioral assessments of offspring indicated no consistent NP-related effects in open-field activity at PNDs 22-24, 43-45, and 65-67 nor in running wheel activity at PNDs 63-75. Play behavior at PND 35 and intake of a 0.3% saccharin-flavored solution at PNDs 69-71 did not differ with respect to treatment groups. However, intake of a 3% sodium-flavored solution at PNDs 73-75 was significantly increased in offspring of the 2,000-ppm group and intake of regular water during this same time was also significantly increased. These results indicate that developmental NP treatment results in maternal and offspring toxicity as evidenced by decreased food intake and weight gain. However, behavioral alterations were evident only in increased intake of a sodium solution.

The ontogeny of induction of c-fos in the rat SCN by a 5-HT(2A/2C) agonist

The induction of c-fos in the suprachiasmatic nucleus (SCN) by the 5-HT(2A/2C) agonist, DOI was studied at mid-dark in neonatal rats. The number of cells expressing c-FOS immunoreactivity following DOI was low 3 days after birth, but increased rapidly over the next 3 days. By contrast, light exposure stimulated cells throughout this period. These results are consistent with the arrival of serotonergic afferents at the SCN and their role in the entrainment of rhythms.

Effects of genistein exposure on sexually dimorphic behaviors in rats

The phytoestrogen genistein, the principal isoflavone in soybeans, has adverse effects on animal reproduction. As adult physiology and behavior are sensitive to perturbation by developmental estrogens, exposure to genistein during development may produce behavioral alterations as well. Pregnant rats were fed soy-free diets containing 0, 25, 250, or 1250 ppm genistein (approximately 0, 2, 20, or 100 mg/kg/day) beginning on gestational day 7, and offspring continued on these diets through postnatal day (PND) 77. Male and female offspring were assessed for levels of sexually dimorphic behaviors: open field activity, play behavior, running wheel activity, and consumption of saccharin- and sodium chloride-flavored solutions. Consumption of the salt solution was affected by genistein, with animals in the 1250-ppm group drinking significantly more than controls; consumption of plain water was unaffected. Genistein treatment also significantly affected play behavior; although no treated group was significantly different from controls, and the effect was not sexually dimorphic. Running wheel activity and saccharin solution consumption showed significant sex differences, but no effects of genistein treatment. Gestational duration, total and live pups per litter, and total and live litter sex ratios were not significantly affected by genistein. However, average weight per live pup at birth and offspring body weights from PND 42-77 were significantly decreased in the 1250-ppm group. Body weight and food intake for the dams were also significantly decreased in the 1250-ppm group. These results indicate that developmental genistein treatment, at levels that decrease maternal and offspring body weight, causes subtle alterations in some sexually dimorphic behaviors.

Prenatal exposure to SKF-38393 alters the response to light of adult rats

The current study examined the consequences of prenatal SKF-38393 exposure on the cellular response in the adult suprachiasmatic nuclei to light. Pregnant rats were injected with the dopamine agonist SKF-38393 or vehicle daily from gestational day 15 to 21. Adult offspring received a light pulse (1 min/2 lux) 4 or 8 h after lights off (ZT16 or ZT20 where ZT=zeitgeber time). Brains were processed for c-FOS-like immunoreactivity in the SCN. At ZT20 the number of cells expressing c-FOS protein after a light pulse was the same in both groups. At ZT16 the number of cells in the SCN of SKF-38393-exposed animals was 58% lower than the vehicle-treated group. The data suggest that prenatal SKF-38393 treatment may have long-term consequences for SCN function.

Minimal behavioral effects from developmental cerebellar stunting in young rats induced by postnatal treatment with alpha-difluoromethylornithine

Postnatal treatment with alpha-difluoromethylornithine (DFMO), a potent inhibitor of ornithine decarboxylase, reduces polyamine levels in rats. Because polyamines are critically involved in growth and development, body and/or brain weights are often decreased by DFMO treatment. Here, rats were injected subcutaneously with 0, 250, 500, or 750 mg/kg of DFMO on postnatal days (PNDs) 5-10. Behavioral assessments included righting reflex, negative geotaxis, forelimb hanging, open field activity, and rotarod performance. Additionally, day of eye opening was recorded and on PND 28, whole and regional brain weights were measured. Cerebellar/whole-brain ratio was decreased in a dose-dependent manner whereas frontal cortex/whole-brain ratio was increased. Eye opening was delayed to a similar extent in all treated groups whereas body weight was unaffected. alpha-difluoromethylornithine treatment had no significant effects on the assessed behaviors. These results indicate that 6 days of DFMO treatment can substantially impact cerebellar development, but this appears to have few effects on these early assessed behaviors. However, potential behavioral alterations may not be apparent until adulthood. Published by Elsevier Science Inc.

An evaluation of l-ephedrine neurotoxicity with respect to hyperthermia and caudate/putamen microdialysate levels of ephedrine, dopamine, serotonin, and glutamate

l-Ephedrine is an active ingredient in several herbal formulations with a mechanism of action similar to amphetamine and methamphetamine. However, its potential to damage dopaminergic terminals in the caudate/putamen (CPu) has yet to be fully evaluated. The studies here used in vivo brain microdialysis experiments to determine the systemic doses and extracellular brain levels of l-ephedrine necessary to produce similar increases in CPu extracellular dopamine and marked hyperthermia that were previously shown necessary for amphetamine-induced neurotoxicity in male Sprague-Dawley rats. At an environmental temperature of 23 degrees C, a single 40 mg/kg intraperitoneal (ip) dose of l-ephedrine produced marked hyperthermia (>/= 40 degrees C), peak microdialysate ephedrine levels of 7.3 +/- 1.2 microM, and a 20-fold increase in microdialysate dopamine levels. Twenty-five mg/kg produced a lesser degree of hyperthermia, peak microdialysate ephedrine levels of 2.6 +/- 0.4 microM, and a 10-fold increase in dopamine levels. Three doses of 40 mg/kg given at 3-h intervals or 4 doses of 25 mg/kg l-ephedrine given at 2-h intervals were compared with 4 doses of 5 mg/kg d-amphetamine given at 2-h intervals. Multiple doses of either ephedrine or amphetamine caused severe hyperthermia (>/= 41.3 degrees C) but striatal tissue levels of dopamine 7 days after dosing were reduced only 25% or less by ephedrine compared to the 75% reductions produced by amphetamine. The increases in CPu microdialysate levels of serotonin produced by either 4 x 25 mg/kg l-ephedrine or 4 x 5 mg/kg d-amphetamine did not significantly differ, but elevation of dopamine levels by d-amphetamine were over 2-fold times the level caused by l-ephedrine. Microdialysate glutamate levels were elevated to the same extent by either 25 mg/kg l-ephedrine or 4 x 5 mg/kg d-amphetamine. l-Ephedrine may not be as neurotoxic to dopaminergic terminals as d-amphetamine, because non-lethal doses of l-ephedrine do not sufficiently increase the CPu dopamine levels within nerve terminals or the extracellular space to those necessary for a more pronounced long-term dopamine depletion.

Acute effects of cocaine on play behaviour of rats

Play behaviours are exhibited by many mammalian species. The similarity of such behaviour across children, non-human primates and rats makes it an especially appropriate target for the investigation of drug- or toxicant-induced disruption. In this study the acute effects of cocaine on play behaviour in male and female Sprague-Dawley rats was assessed. Same-sex dyads of rats (postnatal day 35-36) were separated 24 h prior to testing. On the following day, one or both rats of the dyad were injected with the same dose of cocaine (0, 2.5, 5.0 or 20.00 mg/kg). Thirty minutes later the rats were placed together and, after 5 min of habituation, the frequency of pins and crawl-overs were measured for each subject. In dyads in which both rats were treated, crawl-overs and pinning behaviour were decreased by 20 mg/kg cocaine. In dyads in which only one rat was treated, there was marginal effect of cocaine treatment on pinning frequency, while crawl-overs were unaffected. Pinning frequency was not sexually dimorphic in either type of dyad; however, crawl-overs were more frequently exhibited by females in dyads in which only one rat was treated. Thus, pinning behaviour in juvenile rats appears somewhat more sensitive to cocaine-induced disruption than crawl-over behaviours. Additionally, the presence of an untreated rat appears to attenuate the play-disrupting effects of cocaine on pinning frequency.

Prenatal exposure to the dopamine agonist SKF-38393 disrupts the timing of the initial response of the suprachiasmatic nucleus to light

The abuse of social drugs such as cocaine during pregnancy represents enormous risks to the offspring. Recent studies showed that drugs administered to the pregnant rat can activate cell populations in the fetal brain, possibly altering the timing of key neuronal developmental events. The current study examined the ontogeny of light-responsiveness of the neonatal rat suprachiasmatic nucleus using c-FOS protein in SCN nuclei as a marker. The effect of acute administration of the dopamine D1 agonist, SKF-38393, on the development of light responsiveness was also examined. Pregnant dams received either SKF-38393 (10 mg/kg) or vehicle 7 h after dawn on gestational day 20. Litters were then assigned to one of seven experimental time points from 4 h after subjective dark onset on the day of birth (P0-CT16) at 4-h intervals until CT16 on the day after birth (P1-CT16). Half of the pups in each litter were exposed to a 200 lux/2 h light pulse and the other half remained in darkness. Three time points (P1-CT0, P1-CT8 and P1-CT16) were used to examine the prenatal drug effects on light-responsiveness. Light exposure at the time of subjective lights on, the day after birth (P1-CT0), resulted in a significant increase in c-FOS-positive cells. The number of positive cells recorded in the SCN after a light pulse at P1-CT0 and P1-CT8 was significantly less in SKF-38393 pretreated pups compared to vehicle treated animals. The exposure to dopaminergic stimulation during gestation may have altered the timing of development of afferent connections to the fetal SCN, resulting in alteration of the initial response of the circadian timing system to light.

Neck pain and head restraint position relative to the driver's head in rear-end collisions

This two-year investigation was designed to estimate the incidence of driver neck pain in rear-struck vehicles involved in two-vehicle collisions and to determine the relationship between neck pain and specific vehicle, human, and environmental factors. Neck pain percentages were significantly higher for female (45%) than for male (28%) drivers. For female and male drivers, neck pain likelihood increased as head restraint height decreased below the head's center of gravity, although this effect was significant only for females. Head restraint backset, the horizontal distance measured from the back of the driver's head to the front of the head restraint, was not found to be related to neck pain for female drivers. Backset trends for male drivers could not be evaluated because few male drivers had head restraints that were high enough for backset to be relevant. Reported neck pain decreased for older drivers (females only), drivers in less severe crashes, and drivers in heavier cars (females only); all head restraint analyses were adjusted for these characteristics. Women, and most likely men, in the United States would benefit greatly from international harmonization to European head restraint standards. Until then, both women and men should be encouraged to adjust their adjustable head restraints, if possible, behind their heads' centers of gravity and to sit with the backs of their heads as close as possible to their head restraints.

Child seating position and restraint use in three states

OBJECTIVE

Because of risks from deploying airbags to children in front seats, extensive publicity has been aimed at getting them restrained and in rear seats. The objective of this study was to assess restraint use and seating positions among children in vehicles with and without airbags.

METHOD

Surveys were conducted in cities in Michigan, North Carolina, and Texas 1998. Restraint use and seating position were noted for all children, as well as their estimated age, driver belt use, airbag presence, and vehicle license plate number.

RESULTS

Fewer children were observed in the front seats of vehicles with passenger airbags (24%) than in vehicles without them (36%). Most of the children seated in front were ages 7-12 (44%-61%), followed by 3-6 year olds (29%-35%). Very few children ages 0-2 were seated in front (5%-12%). The overwhelming majority of children ages 0-2 were restrained. However, children ages 3-6 seated in the front were least likely to be restrained and most likely to be improperly restrained. Restraint use was higher when the driver was belted, but about 30% of 3-6 year olds were unrestrained even with a belted driver.

CONCLUSIONS

Efforts should continue to educate parents about the importance of correct restraint use and rear seating for children, particularly once children move from child safety seats into adult belts. Efforts also should be made to enforce the seat belt laws that exist in every state.

Impairment magnification during dynamic trunk motions

STUDY DESIGN

An examination of a group of patients with low back disorder and a group of healthy (asymptomatic) individuals asked to produce trunk motions under sincere and insincere experimental conditions. Trunk motion components were examined to determine which combination of motion components could best distinguish between sincere and insincere efforts.

OBJECTIVE

To determine whether examination of trunk motion components could be used to identify impairment magnification during unresisted repeated bending tasks.

SUMMARY OF BACKGROUND DATA

Trunk motion measures can be used to assess and "benchmark" the status of the low back. However, these measures typically are clinically useful only if the individual is producing an effort that does not magnify the impairment during the functional evaluation. This study addressed the issue of impairment magnification during the production of free dynamic trunk motion.

METHODS

The trunk motion characteristics of 100 healthy individuals and 100 patients with chronic low back disorders were documented. All participants were asked to produce the trunk motions in two different types of conditions. In the one experimental condition, they were asked to produce sincere trunk motions. In the other experimental condition they were asked to pretend either that they were experiencing low back pain (the asymptomatic group) or that their pain was worse than it actually was (group with low back pain).

RESULTS

A combination of trunk motion measures was able to distinguish well between the conditions. Sensitivity and specificity for the asymptomatic group were 92%, whereas they were 75% for the group with low back pain. Overall, sensitivity and specificity were 81.5% for all the participants combined.

CONCLUSIONS

These results indicate that motion measures can be used to help assess impairment magnification during functional trunk motion testing. These measures can provide a means by which to scrutinize the quality of quantitative measures indicating the extent of a low back disorder. These objective motion measures also can be used to complement other subjective observational methods for the assessment of impairment.

The quantification of low back disorder using motion measures. Methodology and validation

STUDY DESIGN

Trunk angular motion features were used as a means to quantify the extent of a low back disorder in healthy people and patients with chronic low back disorders.

OBJECTIVE

To refine and validate a previously reported means of quantifying the extent of a low back disorder.

SUMMARY AND BACKGROUND

Many assessment tools of low back disorder are subjective. A quantitative assessment tool would facilitate the tracking of the recovery and help document the appropriateness of treatments.

METHODS

The trunk motion characteristics of 374 healthy people and 335 patients with chronic low back disorders of varying severity were documented as they flexed and extended their trunks in five different planes of motion. The trunk motion features were normalized as a function of age and gender. Four classification techniques were used to assess the ability of the quantitative motion measure to identify those with and without low back disorders. In addition, 31 patients were observed longitudinally to determine whether the motion measures agreed with observed changes in back pain symptoms.

RESULTS

The quantitative trunk motion measure distinguished between people with low back disorders and healthy people between 88% and 94% of the time, depending on which classification system was used. Sensitivity and specificity varied between 83% and 97%. The quantitative measure also showed promise as a means to distinguish between muscle-based and structure-based low back disorders. Prospective findings indicated that the quantification system agreed well with clinical observations of progress.

CONCLUSIONS

The quantification of trunk motion can serve as a measure of the extent of a low back disorder. When considered along with other clinical information, the ability to assess and treat low back disorders is enhanced.

Emergence of altered circadian timing in a cholinergically supersensitive rat line

Mammalian circadian rhythms are controlled by the suprachiasmatic nuclei (SCN) in concert with light information. Several neurotransmitters and neural pathways modulate light effects on SCN timing. This study used a line of rat with an upregulated cholinergic system to investigate the role of acetylcholine in rhythmicity. With the use of a selective breeding program based on the thermic response to a cholinergic agonist, we developed a supersensitive (S(ox)) and subsensitive (R(ox)) rat line. The S(ox) rats showed an earlier onset time of melatonin rhythm under a 12:12-h light-dark photoperiod from generation 3 (3 +/- 0.5 h after dark) compared with R(ox) rats (4.5 +/- 0.1 h) and an earlier morning decline in temperature (0.9 +/- 0.3 h before lights on) compared with R(ox) animals (0.1 +/- 0.1 h). Furthermore, the S(ox) animals displayed a significantly shorter free-running period of temperature rhythm than R(ox) rats (23.9 +/- 0.04 and 24.3 +/- 0.1 h, respectively, P < 0.05). The results suggest that the altered circadian timing of the S(ox) rats may be related to the cholinergic supersensitivity, intimating a role for acetylcholine in the circadian timing system.

Gestational stage-specific effects of retinoic acid exposure in the rat

Although, or perhaps because, retinoids are among the earliest known behavioral teratogens, there is still little agreement about the behavioral effects of stage-specific exposure to these compounds. In these studies, pregnant albino rats were gavaged once daily with retinoic acid (RA) for 3 consecutive gestational days (GD), GD 8-10), GD 11-13, or GD 14-16. Dose levels were maximal levels compatible with survival (10, 2.5, or 12.5 mg/kg RA, over GD 8-10, 11-13, and 14-16, respectively). Two studies were conducted. The first assessed the effects of RA exposure on GD 8-10 or 14-16 on regional brain weight and on a large behavioral test battery. The second study assessed the effects of RA exposure on GD 11-13 or GD 14-16 on many of the same variables. Taken together with an earlier study of the behavioral effects of GD 11-13 RA exposure, these studies permit the following conclusions. 1) RA exposure at the above doses at any of the three exposure periods produced an apparent reduction in amphetamine-induced open field activity. 2) RA exposure on GD 14-16 but not earlier produced a robust, replicable rotarod deficit in exposed offspring. 3) RA exposure on GD 11-13, but not earlier or later, increased daytime activity in residential running wheels. 4) RA exposure on GD 11-13 or GD 14-16 but not GD 8-10 reduced weight of cerebellum. 5) No RA effect at any exposure period was seen on maze learning, activity in novel open fields, or on auditory startle.

Nicotine phase shifts the 6-sulphatoxymelatonin rhythm and induces c-Fos in the SCN of rats

The neurotransmitter acetylcholine is not found in the major suprachiasmatic nuclei afferents reported to mediate light effects on entrainment and phase shifts in mammals; however it clearly has some role in the control of circadian rhythmicity. This study examined the effect of the cholinergic agonists nicotine and oxotremorine on (1) the rhythmic production of melatonin using the metabolite, 6-sulphatoxymelatonin as a marker, and (2) the expression of c-Fos protein in the suprachiasmatic nuclei (SCN) of the rat. Nicotine administration (1 mg/kg, s.c.) caused phase delays in the timing of the onset of 6-sulphatoxymelatonin excretion (compared to the pre-treatment night), when administered at circadian time (CT)16 (1.7+/-0.3 h delay) and CT18 (1.7+/-0.2 h delay) but not at CT14 (0.8+/-0.3 h delay), whereas oxotremorine and saline administration had no effect on the timing of the melatonin rhythm. Nicotine administration also caused the induction of c-Fos-like immunoreactivity in the SCN in a dose- and time-dependent manner. Further, pre-treatment with the nicotinic antagonist mecamylamine reduced the number of nicotine-induced c-Fos-positive cells in the SCN by 65%. These data indicate that cholinergic neurons may alter the timing of the onset of melatonin excretion by a direct or indirect effect on the SCN possibly mediated by the nicotinic receptor.