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PubMed2002

Peroxynitrite generated in the rat spinal cord induces neuron death and neurological deficits.

We previously demonstrated that the concentration of peroxynitrite significantly increases following impact spinal cord injury (SCI). The aim of this study was to test whether the SCI-induced elevation of peroxynitrite induces neuronal death and consequent neurological deficits. Peroxynitrite was generated by administering 5 mM S-morpholinosydnonimine, a donor of peroxynitrite, through a microdialysis fiber into the gray matter of the rat spinal cord for 5 h. This mimics the concentration and duration of peroxynitrite elevation after SCI. Neuron death was assessed by counting the neurons along the fiber track in Cresyl Violet-stained sections removed at different times post-peroxynitrite exposure. Peroxynitrite induced significantly more neuron death than did the artificial cerebrospinal fluid (ACSF) control, with the percentage of neuronal loss being 17+/-2%, 28+/-2%, 39+/-3%, and 43+/-4% at 6, 12, 24 and 48 h post-peroxynitrite exposure (P=0.01-<0.001). The losses of total neurons or motoneurons immuno-stained with anti-neuron-specific enolase or anti-choline acetyltransferase antibodies was significantly higher in the peroxynitrate-exposed group than in ACSF controls at 24 h post-exposure, further confirming peroxynitrate damage to neurons. The susceptibility to oxidative damage in motoneurons was similar to that of other neurons characterized at 24 h post-peroxynitrite exposure. Peroxynitrite-induced neurological deficits were examined by the Basso-Beattie-Bresnahan test (BBB test), the inclined-plane test and footprint analysis. Peroxynitrite significantly (P<0.001) reduced the locomotor rating score (BBB test) and the maximum angle of inclined plane compared to sham and ACSF-exposed animals (repeated measures analysis of variance). The footprint analysis revealed that peroxynitrite significantly increased the distance between the feet and the angle of hindlimb rotation compared to sham (P=0.01 and P<0.001) or ACSF controls (P=0.01 and P=0.005) and significantly shortened the stride length compared to sham (P<0.001) and ACSF control (P=0.005) treatments. Therefore the SCI-produced level of peroxynitrite induced neuron loss and neurological dysfunction, strong evidence that peroxynitrite is a secondary damage agent in SCI.

Animals↗
PubMed1997

Chinese adults are less susceptible than whites to age-related endothelial dysfunction.

OBJECTIVES: We sought to assess the effects of aging on the endothelial physiology of a group of Chinese adults. BACKGROUND: Several studies have documented an association between aging and progressive arterial endothelial dysfunction in white subjects. We hypothesized that age-related endothelial dysfunction, an important event in atherosclerosis, might be less marked in southern Chinese subjects, in whom the prevalence of coronary heart disease is only approximately 20% of that in industrialized countries. METHODS: We studied endothelial function in 76 healthy adults aged 16 to 70 years: 38 Chinese from a village of 3,000 people in southern China and 38 white subjects from Sydney, Australia. In each ethnic group, there were 19 younger persons (16 to 40 years) and 19 older adults (55 to 70 years). None had evidence of diabetes, hypertension or clinical vascular disease or had ever been regular cigarette smokers. With the use of high resolution external vascular ultrasound, brachial artery diameter was measured at rest, after flow increase (causing endothelium-dependent dilation) and after sublingual nitroglycerin (an endothelium-independent dilator). RESULTS: Endothelium-dependent dilation was similar in young Chinese (mean +/- SD 8.3 +/- 2.5%), young whites (7.9 +/- 2.0%) and older Chinese (6.8 +/- 2.9%), but it was significantly impaired in older whites (1.8 +/- 2.5%, p < 0.001 by analysis of variance). On multivariate analysis, older age was associated with impaired endothelium-dependent dilation (p < 0.001) (independent of the effects of serum cholesterol, gender and vessel size) in the white but not in the Chinese subjects (p = 0.83). Nitroglycerin-induced dilation was not significantly different with aging in either ethnic group. CONCLUSIONS: Endothelium-dependent dilation is similar in the arteries of healthy young Chinese and white adults. With older age, however, Chinese subjects are less susceptible to impaired endothelial function.

Adolescent↗
PubMed2002

Effect of distance and infusion rate on operation of Medfusion 2010 infusion pump during magnetic resonance imaging.

STUDY OBJECTIVES: To determine the accuracy and reliability of intravenous infusion, as well as magnetic resonance image effect of the Medfusion 2010 infusion pump (Medex Medical Supplies, Inc., Duluth, GA) at distances of 2, 4, 8, 12, and 16 feet from a 1.5 Tesla MRI magnet over a four-week time interval, using infusion rates that would correspond to those of propofol administration. DESIGN: Prospective, open-label study. SETTING: Radiology department MRI in an American academic medical center. INTERVENTIONS: Five infusion pumps, including one outside the MRI suite as control, were tested. Pumps were evaluated at distances of 2, 4, 8, 12, and 16 feet from a 1.5 Tesla magnet. One pump at distances of 2 and 16 feet was tested during 30 and 90 hours of operation, respectively. Three pumps at distances of 4, 8, and 12 feet were tested during 120 hours of operation. Pump batteries were recharged for 18 hours outside the MRI suite between the 6-hour test periods. Distilled, deionized water was infused from a 30-mL or 60-mL syringe via a 36-inch Medex small-bore extension set into a graduated collection cylinder at rates of 5, 10.5, 21, or 42 mL/hr. Each rate was increased to the next infusion rate level at 30-hour weekly intervals. The collection cylinder with infused water was weighed on an electronic scale accurate to within +/-0.001 g. Analysis of variance and regression analysis were used to analyze data. A p < 0.05 value was considered statistically significant. MEASUREMENTS AND MAIN RESULTS: There was no significant difference comparing the grams weight of volume measured and the mL volume visualized within and between groups at varying distances from the magnet. Increasing infusion rates resulted in corresponding increases in volume delivered irrespective of the distance from the magnet. CONCLUSIONS: The Medfusion 2010 infusion pumps were found to be reliable and accurate, without causing failure or any significant degradation of MRI images compared to control at infusion rate of 42 mL/hr at a distance of 2 feet for 30 hours; and a rate of 5.0, 10.5, 21, and 42 mL/hr at 16 feet for 90 hours; and at 4, 8, and 12 feet for 120 hours of operation.

Anesthesiology↗
PubMed2000

Perceived parental monitoring and health risk behaviors among urban low-income African-American children and adolescents.

PURPOSE: To examine gender and age differences among urban, low-income, African-American children and adolescents in perceived monitoring by their parents, and the association of perceived parental monitoring with family characteristics, health risk behaviors, and risk perceptions. METHODS: Three cross-sectional surveys were conducted in 1992 (n = 455), 1994 (n = 355), and 1996 (n = 349). Respondents aged 9-17 years were recruited from low-income urban areas including public housing communities and associated recreation centers. Both multivariate analysis of variance and correlation analysis were performed. RESULTS: Low levels of perceived parental monitoring were associated with participation in several health risk behaviors, including sexual behavior, substance/drug use, drug trafficking, school truancy, and violent behaviors. Females perceived themselves to be more monitored than did males. In general, the perceived parental monitoring tended to decrease with advancing age of the youth. CONCLUSIONS: The strong inverse correlation between perceived parental monitoring and adolescent risk behavior suggests that parental monitoring initiatives may be an effective intervention tool. Longitudinal studies are needed to determine the long-term relationship between perceived parental monitoring and adolescent risk involvements.

Adolescent↗
PubMedDate not supplied

Development of a tool to assess psychosocial indicators of fruit and vegetable intake for 2 federal programs.

OBJECTIVE: Development of an evaluation tool of psychosocial constructs for use by participants in 2 federal programs, Food Stamp Nutrition Education and the Expanded Food and Nutrition Education Program. DESIGN: Cross-sectional data from a longitudinal study. PARTICIPANTS: Limited-resource women (n = 111) living in low-income communities. MEASURES: Test-retest reliability, internal consistency, ethnic differences, convergent validity. ANALYSIS: Spearman rank order correlation, analysis of variance, principal components analysis. RESULTS: Reliability coefficients ranged from a low of r = .18 (not significant) to r = .74 (P < .0001). Two items were deleted for not meeting criteria for reliability and 2 for redundancy. Ethnic differences at baseline were significant for 1 item. Domain constructs loaded on 4 to 5 factors for the biopsychosocial framework. Estimates of convergent validity of 9 constructs led to the deletion of 3 (ie, perceived barriers, social support, and perceived norms), with retention of perceived benefits, perceived control, self-efficacy, readiness to eat more fruit, readiness to eat more vegetables, and perceived diet quality. As an estimate of convergent validity, the final version of the tool with 6 constructs remaining showed significant correlations with indicators of diet quality: serum carotenoid values (r = .38, P < .001); hypothesized nutrients calculated from the mean of 3 24-hour dietary recalls (vitamin C, r = .47, P < .0001; vitamin A, r = .39, P < .0001; folate, r = .37, P < .0001; beta-carotene, r =.31, P < .001; and fiber, r = .46, P < .0001); fruit and vegetable servings (r = 0.55, P < .0001); Healthy Eating Index (r = .27, P < .05); and a fruit and vegetable behavioral scale (r = .60, P < .0001). CONCLUSION AND IMPLICATIONS: This systematic process yielded a fruit and vegetable evaluation tool useful for practitioners and researchers. This is the first validation study of this type to estimate convergent validity with 5 indicators of diet quality, including a biomarker.

Adult↗
PubMed2002

Validation of the SF-36 for the assessment of quality of life in adolescents and adults with cystic fibrosis.

BACKGROUND: Generic health-related quality of life measures are often applied to disease groups without assessment of their psychometric properties. The current work assesses the properties of the Short Form 36-item (SF-36) questionnaire in a British sample of adolescents and adults with cystic fibrosis (CF). METHODS: Two hundred and twenty-three adolescents and adults with CF completed the SF-36 with a further 185 approached and not responding by non-completion of the questionnaire. The structure and internal reliability of the instrument was assessed by principal components analysis, Cronbach alpha coefficients and item to domain correlations. Differences between disease severity groups were assessed by analysis of variance. RESULTS: Factor analysis of the SF-36 scores broadly confirmed domain structures for the SF-36. Cronbach alpha coefficients were high (range 0.82-0.91) and item-to-same domain correlations were stronger than item-to-unrelated domain correlations. Examination of differences between mild, moderate and severe disease states revealed four significant main effects for: physical functioning, role limitation due to physical functioning, general health perceptions and energy and vitality. The analysis also revealed the presence of numerous ceiling effects across domains. CONCLUSIONS: The domain structure of the SF-36 was demonstrated to be robust. However, the discriminatory ability of the measure was disappointing. The presence of ceiling effects and the low frequency of differences between intermediate disease severity groups indicated that the SF-36 was not discriminatory with respect to mild disease states or progression of illness.

Adolescent↗
PubMed2004

Genetic variability of grey snow mould (Typhula incarnata).

Randomly amplified polymorphic DNA (RAPD) markers were used to assess the genetic diversity of isolates of grey snow mould ('gray snow mold'), Typhula incarnata, taken from infected turfgrasses from 40 different locations in the northern USA. Data from 115 markers using 37 RAPD primers showed 48 % polymorphism. The distance coefficients between isolates indicate the wide genetic diversity of T. incarnata across the sample area. Dendrograms generated using neighbour-joining (NJ) bootstrap analyses showed three clades and suggest possible recent colonization from common founder groups. Partitioning of the genetic variance using analysis of molecular variance (AMOVA) of four groups based on geographic locations (Michigan, lower and upper peninsula; Minnesota; Wisconsin) showed that genetic variation attributable among groups and within groups was 12.67 and 87.33 %, respectively. No correlation was found between geographic distance and pairwise genetic distance of the groups. High outcrossing and sexual recombination of T. incarnata may well be key factors explaining the genetic variability as shown with the low Fixation index (FST) and high average of genetic diversity per locus within groups.

Basidiomycota↗
PubMed2005

Essential oil composition of Citrus meyerii Y. Tan. and Citrus medica L. cv. Diamante and their lemon hybrids.

In this paper we report the volatile fraction composition of Citrus meyerii Y. Tan. and Citrus medica L. cv. Diamante and two new lemon hybrids obtained by cross-breeding them with the tetraploid Citrus limon Burm. cv. Cavone. Both parent and hybrid oils were laboratory-extracted from the peel fruits and analyzed by HRGC-MS and HRGC-FID. Sixty-three components were fully characterized by mass spectra, linear retention indices, and injection of standards. The average composition as single components for all the oils analyzed is reported. Moreover, the data obtained were statistically analyzed. Since limonene is by far the main component of all the essential oils examined, analysis of variance and multivariate analysis gave interesting information on the similarities and differences between the oils analyzed. The new hybrid oils analyzed have potential commercial value because they could be an acceptable alternative to the valuable lemon oil.

Chromatography, Gas↗
PubMed2003

Random amplified polymorphic DNA diversity among surface and subterranean populations of Asellus aquaticus (Crustacea: Isopoda).

The ecological and evolutionary processes leading to isolation and adaptation of cave animals compared to their surface ancestors are not yet unequivocally understood. In this study the genetic relations of four cave and three surface population of the freshwater crustacean Asellus aquaticus in the Karst region of SW Slovenia and NE Italy were assessed using RAPDs as genetic markers. The results suggest that specialized populations from two caves invaded their subterranean habitat independently, and that their morphological similarity is a result of convergent evolution. Another, less specialized cave population seems to originate from a later colonization of a cave system already inhabited by a more specialized population, but the two populations do not interbreed. This series of temporally and spatially independent invasions has generated a diversity hotspot of non-interbreeding populations of a ubiquitous freshwater crustacean, which is uniform over most of its range. Genetic variability estimated by the percentage of polymorphic RAPD fragments was similar (86-91%) in most cave and surface populations. Substantially lower values (as low as 49%) were found in two cave populations affected by heavy pollution. Two a priori groupings of populations, traditional subspecies and hydrologically connected groups, were rejected as not significant by means of nested analysis of molecular variance (AMOVA). On the other hand, groupings revealed by UPGMA clustering displayed a significant component of among-group variance. An analysis of gene flow between populations using estimated migration rates confirmed these findings.

Animals↗
PubMed2002

Mechanism of lonidamine inhibition of the CFTR chloride channel.

1. The cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel is blocked by a broad range of organic anionic compounds. Here we investigate the effects of the indazole compound lonidamine on CFTR channels expressed in mammalian cell lines using patch clamp recording. 2. Application of lonidamine to the intracellular face of excised membrane patches caused a voltage-dependent block of CFTR currents, with an apparent K(d) of 58 micro M at -100 mV. 3. Block by lonidamine was apparently independent of channel gating but weakly sensitive to the extracellular Cl(-) concentration. 4. Intracellular lonidamine led to the introduction of brief interruptions in the single channel current at hyperpolarized voltages, leading to a reduction in channel mean open time. Lonidamine also introduced a new component of macroscopic current variance. Spectral analysis of this variance suggested a blocker on rate of 1.79 micro M(-1) s(-1) and an off-rate of 143 s(-1). 5. Several point mutations within the sixth transmembrane region of CFTR (R334C, F337S, T338A and S341A) significantly weakened block of macroscopic CFTR current, suggesting that lonidamine enters deeply into the channel pore from its intracellular end. 6. These results identify and characterize lonidamine as a novel CFTR open channel blocker and provide important information concerning its molecular mechanism of action.

Animals↗
PubMed1998

Genetic linkage analysis using lognormal variance components.

Typically genetic studies of continuous traits such as cholesterol levels or blood pressure assume that interindividual variability follows a normal distribution. Here we develop methods to analyze positively skewed data by assuming a lognormal distribution. We develop a variance components approach for identifying such effects from a major gene, residual polygenic factors and nongenetic factors. We compare by a simulation study results from fitting this lognormal model with either applying the log transformation or not transforming the data. We found that the lognormal model provided more precise estimates and more powerful tests than a simple log transformation when analyzing lognormally distributed data. Power varied with sibship size. For the same total number of nonindependent sibpairs, larger sibships were less powerful. However, larger sibships are more economical because they require a smaller sample size to obtain a specified power. To illustrate the application of this lognormal model to real data, we studied evidence for linkage between triglycerides and the lipoprotein lipase gene.

Genetic Linkage↗
PubMed2003

Neuroimaging in cerebrovascular disorders: measurement of cerebral physiology after stroke and assessment of stroke recovery.

Nuclear medicine imaging can play an important role in the diagnosis of stroke risk, the differential diagnosis of vascular and parenchymal cerebral abnormalities, and the understanding and management of poststroke recovery. Radionuclide brain-imaging methods can assess hemodynamic, vascular, and metabolic status before and after stroke. Several techniques, including vasodilatory stress imaging with regional cerebral blood flow (rCBF) single-photon emission computed tomography (SPECT), oxygen extraction methods with positron emission tomography (PET), and spectroscopic imaging with magnetic resonance spectroscopic imaging, offer ways to distinguish vascular from parenchymal dysfunction and to determine whether any observed abnormalities in cerebral blood flow are primary or secondary disease manifestations. The value of radionuclide imaging in assessing the efficacy of several interventional surgical procedures is presented. Data from several imaging modalities bearing on the controversial issue of luxury perfusion and reperfusion injury are analyzed, including some of the discrepancies between animal and human clinical data. Imaging evidence for white matter disease and microangiopathy is analyzed, including a quantitative rCBF pattern analysis that distinguishes between typical Alzheimer's disease and microangiopathy by using multivariate analysis of variance curve profile analysis, which shows results of significant differences in the circumferential cortical blood flow profiles at P =.01. Microangiopathy showed rCBF reduction in the frontal and frontotemporal regions as compared with the more typical reduction in posterior temporal-parietal rCBF diminution characteristic of Alzheimer's disease. Several functional neuroimaging approaches to the study of cerebral poststroke reorganization are analyzed in the context of 2 major models of recovery: the resolution of diaschisis and reorganization in spared brain. Research on these issues is presented with SPECT, PET, magnetic resonance imaging, and magnetic resonance spectroscopy. Data show how standard structural magnetic resonance imaging, (99m)Tc hexamethylpropylene amine oxime SPECT, PET imaging, and magnetic resonance spectroscopy can be used to identify the extent of permanent damage versus penumbral and remote effects of a stroke. The results of the analysis of the pure-diaschisis model show a high correlation between the rCBF brain SPECT defect volume in the cortex and the magnetic resonance spectroscopic imaging (MRSI) change in the white matter. There is a statistically significant positive correlation between the 2 (P <.01; r(2) = 0.94). The increased creatine/N-acetyl aspartate and reduced rCBF are proposed to be due to an increase in the white matter creatine component due to diaschisis and the repair mechanisms associated with increased astrocytosis, in addition to a reduction of N-acetyl aspartate in diaschitic white matter. Xenon-133 dynamic SPECT is shown to be a quantitative and sensitive measure of cerebrovascular status and hemodynamic constraints in both spared and affected brain, providing evidence for reorganization and cerebral plasticity. Fluorine-18 PET and (31)P spectroscopic imaging data show reorganizational changes in the contralesional hemisphere after stroke. The phosphocreatine-adenosine triphosphate ratio in the contralesional hemisphere was 38% +/- 17% higher than in the ipsilateral hemisphere. The phosphocreatine-adenosine triphosphate ratio was highly correlated (r = 0.88, P <.05) with increasing (18)F-fluorodeoxyglucose uptake. These results showed that there is a parallel change in glucose metabolism and high-energy phosphate metabolism associated with poststroke recovery that is proposed to be due to cerebral reorganization in the contralateral premotor cortex. The value of these results on rehabilitation strategy, including possible criteria for the use of facilitatory versus compensatory approaches, is analyzed.

Aged↗
PubMedDate not supplied

Effects of home telemonitoring and community-based monitoring on blood pressure control in urban African Americans: a pilot study.

BACKGROUND: African Americans have a higher prevalence and greater severity of hypertension than do other minorities and whites. This fact is particularly problematic when one realizes that the rate of control and treatment of hypertension in the US population is getting worse rather than better. Alternative strategies to promote blood pressure control need to be tested. OBJECTIVES: The purpose of this pilot study was to test the following hypothesis: Persons who participate in nurse-managed home telemonitoring (HT) plus usual care or who participate in nurse-managed community-based monitoring (CBM) plus usual care will have greater improvement in blood pressure from baseline to 3 months' follow-up than will persons who receive usual care only. METHODS: This study used a randomized controlled design; participants were randomly assigned to 1 of 3 groups that were stratified by use or nonuse of antihypertension medication. One-way analysis of variance (ANOVA) and analysis of covariance (ANCOVA) controlling for age and body weight were used to determine changes in blood pressure from baseline to 3 months. The sample contained 26 African Americans with a mean age of 59 years. RESULTS: Both the HT group and the CBM group had clinically and statistically significant (P <.05) drops in systolic blood pressure (SBP) and diastolic blood pressure (DBP) at 3 months' follow-up, with participants in the HT group demonstrating the greatest improvement (HT: baseline SBP 148.8 +/- 13.8, DBP 90.2 +/- 5.79; 3 months' follow-up SBP 124.1 +/- 13.82, DBP 75.58 +/- 11.4; CBM: baseline SBP 155.25 +/- 17.014, DBP 89.42 +/- 10.95; 3 months' follow-up SBP 142.3 +/- 12.1, DBP 78.25 +/- 6.86). There was little change in SBP or DBP at 3 months' follow-up in the usual care only group. CONCLUSION: These are important pilot results, which if replicated in a larger sample will significantly improve care for urban African Americans with hypertension.

Adult↗
PubMed2002

Genes on chromosomes 1 and 13 have significant effects on Ascaris infection.

Nematode parasites show a characteristic aggregated distribution among hosts. This observation has important implications for pathogenesis, immunology, and control of these infections, but the relative roles of environment and genetics in determining these patterns have remained uncertain. This paper presents the results of the first genome scan for susceptibility to infection with roundworm (Ascaris lumbricoides). Data on 375 genetic markers were generated for each of 444 members of a genetically isolated Nepalese population, the Jirels. Ascaris worm burden as assessed by egg counts was measured in these same individuals by using the Kato Katz thick smear method. The extensive genealogical data available for the population allowed assignment of all 444 individuals to a single pedigree that contained 6,209 pairs of relatives that were informative for genetic analysis. A variance components linkage analysis resulted in the unequivocal localization of two genes (one on chromosome 1 and another on chromosome 13) with clear, significant effects on susceptibility to Ascaris infection. This is the first evidence that individual quantitative trait loci influence variation in Ascaris burden in humans.

Adolescent↗
PubMed1988

Toward an analogue of alcoholism in mice: analysis of nongenetic variance in consumption of alcohol.

Drinking behavior of the isogenic mouse strain C57BL/6J was analyzed into nongenetic components: stochastic fluctuations, responses to fluctuations in the current environment, and persistent differences between individual animals. The latter accounted for the major part of the variance. The variance was neither increased by differences in diet during the postweaning rapid growth period (prior to assay for drinking choice) nor diminished by uniformity of treatment during this period, suggesting that significant differentiation had occurred prior to weaning. The large variance between animals could be explained by assuming that the genetic role in consumption of alcohol by C57BL mice is permissive--a relative insensitivity to the aversive orosensory and pharmacological effects of 10% alcohol--rather than a specific drug-seeking predisposition.

Alcohol Drinking↗
PubMed1992

Methodologic aspects of a population pharmacodynamic model for cognitive effects in Alzheimer patients treated with tacrine.

Tacrine is a cholinesterase inhibitor with activity in the central nervous system originally marketed for the reversal of competitive neuromuscular blockade. Because a marked reduction in cholinergic neurons is a hallmark of brain changes in Alzheimer disease, tacrine has been studied in two placebo-controlled clinical trials of patients with probable Alzheimer disease. Standard analysis of variance (ANOVA) and analysis of covariance (ANCOVA) have shown a difference between the tacrine group and the placebo group in terms of the cognitive component of the Alzheimer disease assessment scale at the end of the placebo-controlled phase. Due to limitations of ANOVA and ANCOVA, only a selected group of patients could be analyzed by those methods. A population pharmacodynamic model has been developed that allows the use of all observations from one or more trials to be combined. It can incorporate any sequence of active or placebo treatments and account for carryover effects of both placebo and active drug. The time courses of active or placebo treatment response and the development of tolerance to active drug or placebo can be defined. The model describes disease progression without treatment, the placebo effect, and the effect of tacrine as a function of daily dose. Placebo effect and active drug effects are modeled by effect site concentration components.

Algorithms↗
PubMed1996

Adjustments of posture and viewing parameters of the eye to changes in the screen height of the visual display terminal.

To understand the motions caused by the interaction among the different body parts, adjustments of both eye position and body posture to screen height settings of 80, 90, 100, 110 and 120 cm were determined in 10 subjects. The subjects engaged in a non-keyboard, interactive computer game requiring constant visual monitoring. Changes in body positions were determined by video image analysis for the posture parameters and by video frame analysis for the eye parameters. Analysis of variance and correlation analysis showed that neck angle, thoracic bending and vertical eye position were significantly affected by changes in the screen height of the VDT. The study of the interrelationship of eye position and body posture suggested that changes in body positions served to complement the eye position in attaining a better view of the visual target. Viewing angle was observed to be decided mainly by inclination of the neck and the eye. Thoracic bending was also noted to contribute in setting the viewing angle, although to a lesser extent. On the other hand, viewing distance and trunk inclination showed significant correlation.

Adult↗
PubMed2005

Morning melatonin has limited benefit as a soporific for daytime sleep after night work.

Exogenous melatonin administration in humans is known to exert both chronobiotic (phase shifting) and soporific effects. In a previous study in our lab, young, healthy, subjects worked five consecutive simulated night shifts (23:00 to 07:00 h) and slept during the day (08:30 to 15:30 h). Large phase delays of various magnitudes were produced by the study interventions, which included bright light exposure during the night shifts, as assessed by the dim light melatonin onset (DLMO) before (baseline) and after (final) the five night shifts. Subjects also ingested either 1.8 mg sustained-release melatonin or placebo before daytime sleep. Although melatonin at this time should delay the circadian clock, this previous study found that it did not increase the magnitude of phase delays. To determine whether melatonin had a soporific effect, we controlled the various magnitudes of phase delay produced by the other study interventions. Melatonin (n=18) and placebo (n=18) groups were formed by matching a melatonin participant with a placebo participant that had a similar baseline and final DLMO (+/-1 h). Sleep log measurements of total sleep time (TST) and actigraphic measurements of sleep latency, TST, and three movement indices for the two groups were examined. Although melatonin was associated with small improvements in sleep quality and quantity, the differences were not statistically significant by analysis of variance. However, binomial analysis indicated that melatonin participants were more likely to sleep better than their placebo counterparts on some days with some measures. It was concluded that, the soporific effect of melatonin is small when administered prior to 7 h daytime sleep periods following night shift work.

Adult↗