Nonlinear analysis of EEG during NREM sleep reveals changes in functional connectivity due to natural aging

The spatial organization of nonlinear interactions between different brain regions during the first NREM sleep stage is investigated. This is achieved via consideration of four bipolar electrode derivations, Fp1F3, Fp2F4, O1P3, O2P4, which are used to compare anterior and posterior interhemispheric interactions and left and right intrahemispheric interactions. Nonlinear interdependence is detected via application of a previously written algorithm, along with appropriately generated surrogate data sets. It is now well understood that the output of neural systems does not scale linearly with inputs received and, thus, the study of nonlinear interactions in EEG is crucial. This approach also offers significant advantages over standard linear techniques, in that the strength, direction, and topography of the interdependencies can all be calculated and considered. Previous research has linked delta activity during the first NREM sleep stage to performance on frontally activating tasks during waking hours. We demonstrate that nonlinear mechanisms are the driving force behind this delta activity. Furthermore, evidence is presented to suggest that the aging brain calls upon the right parietal region to assist the pre-frontal cortex. This is highlighted by statistically significant differences in the rates of interdependencies between the left pre-frontal cortex and the right parietal region when comparing younger subjects (<23 years) with older subjects (>60 years). This assistance has been observed in brain-imaging studies of sleep-deprived young adults, suggesting that similar mechanisms may play a role in the event of healthy aging. Additionally, the contribution to the delta rhythm via nonlinear mechanisms is observed to be greater in older subjects.     

Digital imaging of the chest

During the past several years, image acquisition in nuclear medicine, computed tomography, ultrasonography, subtraction angiography, and magnetic resonance has been by digitization. Despite these advances, research in the development of digital imaging in conventional radiography has lagged behind. Although studies with a variety of digital techniques have been carried out on several fronts, we still do not possess a method that has captured the imagination of the majority of radiologists and other physicians to a point where it could replace conventional screen-film imaging. This article reviews the current status and general principles of the technology, focusing on the four digital radiographic techniques that have shown the greatest promise - film digitization, an image intensifier - based system, photostimulable phosphor plates, and a scanned projection system. The physical aspects of each of the four systems and the clinical results that have been reported to date, as well as the advantages and disadvantages of each system, are presented.     

Differential effects of sleep disordered breathing on polysomnographic characteristics in preschool and school aged children

ObjectiveChildhood sleep disordered breathing (SDB) peaks in the preschool years. We aimed to compare the effects of SDB on polysomnographic characteristics between preschool and school aged children.Participants and MethodsOne hundred and fifty-two preschool (3–5 y) and 105 school-aged (7–12 y) children, referred for assessment of SDB, plus controls (39, 3–5 y and 34, 7–12 y) with no history of snoring underwent overnight polysomnography. Subjects were grouped by their obstructive apnea hypopnea index (AHI) into those with primary snoring, mild obstructive sleep apnea (OSA), and moderate/severe OSA. The effects of SDB severity on sleep architecture and respiratory characteristics were compared between the age cohorts using quantile regression.ResultsThere was an average reduction in median sleep efficiency of 3.5% (p = 0.004) and an average increase in median WASO of 2% (p = 0.08) between the age cohorts across the severity groups, with sleep efficiency falling and WASO increasing with increasing SDB severity in the school-aged, but not the preschool, cohort. There was an average difference in median central AHI of 0.6 events/h (p < 0.001) between the age cohorts across the severity groups, with the 3–5 y old cohort but not the 7–12 y old cohort having more central apneas with increasing SDB severity.ConclusionsWe have demonstrated clinically important, age-related differences in sleep architecture in children with SDB. Preschool children with SDB maintain sleep efficiency and awaken fewer times throughout the night than do school aged children with a comparable severity of SDB, but experience more central apneas. This may have implications for the outcomes and treatment of SDB in children of different ages.     

The effect of different cement insertion techniques on the bone-cement interface

Since the introduction of cemented total hip arthroplasty, the method of cement usage has evolved through several generations. These changes may have been responsible for an improvement in femoral component longevity. The nature of the bone-cement interface in first-generation cementing techniques has been described, but the bone-cement interface in more recent cementing techniques has not. This article describes the bone-cement interface after 2 different cementing techniques in a canine total hip arthroplasty model.     

Comparison of the basal ganglia in rats, marmosets, macaques, baboons, and humans: volume and neuronal number for the output, internal relay, and striatal modulating nuclei

This study compares the basal ganglia of rats, marmosets, macaques, baboons, and humans. It uses established protocols to estimate the volume and number of neurons within the output nuclei (internal globus pallidus, IGP; and nondopaminergic substantia nigra, SNND), two internal relay and modulating nuclei (subthalamic nucleus, STh; and external globus pallidus, EGP), and a modulator of the striatum (dopaminergic substantia nigra, SND). Nuclear boundaries were defined by using immunohistochemistry for striatal afferents. Total numbers of Nissl-stained and parvalbumin-immunoreactive neurons were calculated by using the fractionator technique. Comparisons between species were standardized relative to brain mass (rats < marmosets < macaques < baboons < humans). The EGP consistently had more neurons relative to the IGP, STh, and SND, which had similar neuronal numbers within each species. The SNND had proportionally more neurons in rats than in primates (especially humans). The distribution of SND neurons varied substantially between rats and primates (very few ventrally located neurons in rats) with humans containing fewer SND neurons than other primates. The reduction in SND neurons in humans suggests less dopaminergic regulation of the basal ganglia system compared with other species. The consistency in the number of IGP neurons across all species, combined with the reduction in SNND neurons in humans, suggests a greater emphasis on output pathways through the IGP and that there are proportionally more STh and EGP neurons in humans.     

The influence of health beliefs on the presentation and consultation outcome in patients with chemical sensitivities

OBJECTIVE: This study was carried out to investigate the impact of the physical effects of a chemical exposure, health and chemical beliefs, and chemical sensitivities treatment preferences on the consultation outcome at a tertiary liaison clinic. METHOD: Eighty-five patients exposed to a range of chemicals were assessed at a joint medical toxicology and psychiatric clinic. Patient's beliefs about chemicals and health, chemical sensitivities and their treatment preferences were assessed using a 23-item questionnaire. RESULTS: Fifty-seven patients (69%) had suffered from a range of initial or delayed symptoms that were probably a clear physical consequence of the exposure (Group A), whereas 26 patients (31%) had not (Group B). There were no significant differences found between groups A and B in terms of their diagnosis and their beliefs about health, food, chemicals and chemical sensitivities treatment preferences. However, patients in Group A were significantly more likely to report moderate to severe symptoms in comparison to Group B. Consultation outcome too did not differ between the two groups. The only predictors of consultation outcome were the patients' chemical sensitivities treatment preferences. Patients who at the outset thought that their treatment should comprise of complete avoidance to chemicals, regular monitoring and the use of alternative rather than conventional medicine were significantly less likely to achieve a favourable consultation outcome. Patients' chemical sensitivities treatment preferences were related to the more general beliefs on health, food and the harmful nature of chemicals and were not related to the chemical exposure variables. CONCLUSION: These findings suggest that addressing patients' treatment preferences and the general beliefs on chemicals, food and health may enhance outcome and perhaps ought to be the target for intervention in context of such a liaison clinic.     

Whole body protein metabolism in children with cancer

Whole body protein synthesis and catabolism were measured using the [ring-2H5]phenylalanine and [1-13C]leucine primed constant infusion technique in 32 paediatric patients with cancer at different stages of treatment. Rates of synthesis (S) and catabolism (C) derived from the [ring-2H5]phenylalanine and [1-13C]leucine models were 4.7 (SD 1.3) (S) and 6.0 (1.5) (C) g/d/kg, and 5.5 (0.8) (S) and 6.8 (1.2) (C) g/d/kg, respectively. These results show that these two tracer techniques give similar results in this study population. Comparison of these values with results previously reported for groups of control children using the [ring-2H5]phenylalanine model (S = 3.69 and 3.93; C = 4.09 and 4.28 g/d/kg) and the [1-13C]leucine model (S = 4.32; C = 4.85 g/d/kg) show that rates of synthesis and catabolism were higher in cancer patients than in controls. Thus whole body protein turnover is increased in children under treatment for cancer. Other indices of metabolism such as plasma amino acids and intermediary metabolites were also measured and showed that, although subjects were in isotopic steady state, there were significant metabolic changes during the course of the primed constant infusions used to measure protein turnover.     

Creatinine related reference ranges for urinary homovanillic acid and vanillylmandelic acid at 6 months of age

The relationship between homovanillic acid (HVA), vanillylmandelic acid (VMA), and creatinine in the urine of 6 month old babies has been studied and reference ranges in the form of centiles constructed for HVA and VMA against creatinine. Over 10,000 urine samples were collected from babies in four health districts in the north of England. HVA and VMA concentration, either independently or when divided by creatinine concentration, were dependent upon the absolute concentration of creatinine in the sample. After adjustment for creatinine significant differences in the mean concentration of HVA were found between sexes. No such differences were found for VMA. HVA and VMA were also found to be age dependent. Centiles were constructed using a procedure which makes no distributional assumptions about the data. The net effect of utilising these centiles was to increase the predictive value of a positive screening test from 20% to 40% without any increase in the false negative rate.