Meconium and neurotoxicants: searching for a prenatal exposure timing.

BACKGROUND: Exposure to organochlorine compounds (OCs) has been a subject of interest in recent years, given their potential neurotoxicity. Meconium is easily available and accumulates neurotoxicants and/or metabolites from the 12th week of gestation. AIMS: To determine whether neurotoxicants, specifically OCs, could be detected in serially collected meconium, and to compare the results with those obtained in cord blood samples. METHODS: A sample of cord blood and three serial stool samples were analysed in 10 newborns. Pentachlorobenzene (PeCB), hexachlorobenzene (HCB), polychlorinated biphenyls (PCBs), dichlorodiphenyl trichloroethane (p,p'-DDT) and its metabolite dichlorodiphenyl dichloroethylene (p,p'-DDE), and hexachlorocyclohexane isomers (alpha-, beta-, gamma-, and delta-HCH) were analysed by gas chromatography. RESULTS: From serial stool collection and analysis in newborns, there was an increase in the concentrations of HCB, p,p'-DDE, PCBs, and beta-HCH between the first and last stools of the newborn. Levels of DDT diminished as pregnancy progressed. Concentrations in cord blood were positively associated with concentrations in meconium for p,p'-DDE and beta-HCH. CONCLUSIONS: Meconium is a very useful instrument for the investigation of fetal exposure to neurotoxicants; serial collection and analysis of meconium should estimate the timing and degree of in utero exposure of the fetus to neurotoxicants. Analysis and interpretation of neurotoxicants in meconium results is a complex process. Measurement in meconium of a wide range of neurotoxic substances should facilitate early identification of harmful exposures, and enable rehabilitation and instigation of preventive measures.     

Children's use of motor vehicle restraints: maternal psychological distress, maternal motor vehicle restraint practices, and sociodemographics.

OBJECTIVE: To determine the relative contribution of maternal psychological distress, maternal restraint use, and sociodemographic characteristics to the likelihood that a child would not be restrained in a motor vehicle. METHODS: We examined data on 6251 children aged 0-17 years from the 1998 National Health Interview Survey. The level of children's motor vehicle restraint use (low vs high) was examined by maternal psychological distress and motor vehicle restraint use. Multivariate regression analyses were used to model the odds of children's low use of motor vehicle restraints, controlling for potential confounders. RESULTS: According to maternal reports, more than 10% of children and nearly 13% of mothers reported low use of motor vehicle restraints. Multivariate analyses revealed that maternal use of restraints and psychological distress were both independently related to children's use of restraints, with maternal low use as the stronger correlate. Older children were more likely than younger children to be low users of motor vehicle restraints if the mother reported that she was a low user of restraints. Families with male children, black and Hispanic mothers, and 4 or more members reported lower use of restraints for their children. CONCLUSIONS: Children's low use of motor vehicle restraints was associated with low levels of maternal motor vehicle restraint use and maternal psychological distress. Moreover, maternal motor vehicle restraint practices become increasingly important as children age. Health care providers should consider maternal motor vehicle restraint use, maternal psychological distress, and child age in addition to sociodemographics when assessing children's motor vehicle safety.     

Muscle activation patterns during walking from transtibial amputees recorded within the residual limb-prosthetic interface

ABSTRACT: BACKGROUND: Powered lower limb prostheses could be more functional if they had access to feedforward control signals from the user's nervous system. Myoelectric signals are one potential control source. The purpose of this study was to determine if muscle activation signals could be recorded from residual lower limb muscles within the prosthetic socket-limb interface during walking. METHODS: We recorded surface electromyography from three lower leg muscles (tibilias anterior, gastrocnemius medial head, gastrocnemius lateral head) and four upper leg muscles (vastus lateralis, rectus femoris, biceps femoris, and gluteus medius) of 12 unilateral transtibial amputee subjects and 12 non-amputee subjects during treadmill walking at 0.7, 1.0, 1.3, and 1.6 m/s. Muscle signals were recorded from the amputated leg of amputee subjects and the right leg of control subjects. For amputee subjects, lower leg muscle signals were recorded from within the limb-socket interface and from muscles above the knee. We quantified differences in the muscle activation profile between amputee and control groups during treadmill walking using cross-correlation analyses. We also assessed the step-to-step intersubject variability of these profiles by calculating variance-to-signal ratios. RESULTS: We found that amputee subjects demonstrated reliable muscle recruitment signals from residual lower leg muscles recorded within the prosthetic socket during walking, which were locked to particular phases of the gait cycle. However, muscle activation profile variability was higher for amputee subjects than for control subjects. CONCLUSION: Robotic lower limb prostheses could use myoelectric signals recorded from surface electrodes within the socket-limb interface to derive feedforward commands from the amputee's nervous system.     

Runners' Injuries

It's easier to prevent running injuries than to treat them. This article helps the physician pinpoint the problem and treat runners without taking them off their feet.     

Temporal Pattern of Cocaine Intake Determines Tolerance vs Sensitization of Cocaine Effects at the Dopamine Transporter

The dopamine transporter (DAT) is responsible for terminating dopamine (DA) signaling and is the primary site of cocaine''s reinforcing actions. Cocaine self-administration has been shown previously to result in changes in cocaine potency at the DAT. To determine whether the DAT changes associated with self-administration are due to differences in intake levels or temporal patterns of cocaine-induced DAT inhibition, we manipulated cocaine access to produce either continuous or intermittent elevations in cocaine brain levels. Long-access (LgA, 6 h) and short-access (ShA, 2 h) continuous self-administration produced similar temporal profiles of cocaine intake that were sustained throughout the session; however, LgA had greater intake. ShA and intermittent-access (IntA, 6 h) produced the same intake, but different temporal profiles, with ‘spiking'' brain levels in IntA compared with constant levels in ShA. IntA consisted of 5-min access periods alternating with 25-min timeouts, which resulted in bursts of high responding followed by periods of no responding. DA release and uptake, as well as the potency of cocaine for DAT inhibition, were assessed by voltammetry in the nucleus accumbens slices following control, IntA, ShA, and LgA self-administration. Continuous-access protocols (LgA and ShA) did not change DA parameters, but the ‘spiking'' protocol (IntA) increased both release and uptake of DA. In addition, high continuous intake (LgA) produced tolerance to cocaine, while ‘spiking'' (IntA) produced sensitization, relative to ShA and naive controls. Thus, intake and pattern can both influence cocaine potency, and tolerance seems to be produced by high intake, while sensitization is produced by intermittent temporal patterns of intake.