The effects of physical vibration on heart rate variability as a measure of drowsiness.

We investigated the effects of low frequency whole body vibration on heart rate variability (HRV), a measure of autonomic nervous system activation that differentiates between stress and drowsiness. Fifteen participants underwent two simulated driving tasks for 60 min each: one involved whole-body 4-7 Hz vibration delivered through the car seat, and one involved no vibration. The Karolinska Sleepiness Scale (KSS), a subjective measure of drowsiness, demonstrated a significant increase in drowsiness during the task. Within 15-30 min of exposure to vibration, autonomic (sympathetic) activity increased (p < .01) in response to the stress of maintaining alertness and performance when drowsy, and peaked at 60 min (p < .001). Changes in three other HRV domains [higher LF/HF ratios, lower RMSSD (ms) and pNN50 (%) values] were consistent with increased sympathetic activation. These findings have implications for the future development of equivalent drowsiness contours leading to improvements in road safety. Practitioner summary: The effects of physical vibration on driver drowsiness have not been well investigated. This laboratory-controlled study found characteristic changes in heart rate variability (HRV) domains that indicated progressively increasing neurological effort in maintaining alertness in response to low frequency vibration, which becomes significant within 30 min. ABBREVIATIONS: ANS: autonomic nervous system; Ctrl: control; EEG: electroencephalography; HF: the power in high frequency range (0.15 Hz-0.4Hz) in the PSD relected parasympathetic activity only; HRV: heart rate variability; KSS: karolinska sleepiness scale; LF: the power in low frequency range (0.04 Hz-0.15Hz) in the PSD reflected both sympathetic and parasympathetic activity of the autonomic nervous system; LF/HF ratio: the ratio of LF to HF indicated the balance between sympathetic and parasympathetic activity; RMSSD: the root mean square of difference of adjacent RR interval; pNN50: the number of successive RR interval pairs that differed by more than 50 ms divided by the total number of RR intervals; RR interval: the differences between successive R-wave occurrence times; PSD: power spectral density; RTP: research training program; SD: standard deviation; SEM: standard error of the Mean; Vib: vibration.

Cognitive impairment in coeliac disease improves on a gluten-free diet and correlates with histological and serological indices of disease severity.

BACKGROUND: Mild impairments of cognition or 'Brain fog' are often reported by patients with coeliac disease but the nature of these impairments has not been systematically investigated. AIM: This longitudinal pilot study investigated relationships between cognitive function and mucosal healing in people with newly diagnosed coeliac disease commencing a gluten-free diet. METHODS: Eleven patients (8 females, 3 males), mean age 30 (range 22-39) years, were tested with a battery of cognitive tests at weeks 0, 12 and 52. Information processing efficacy, memory, visuospatial ability, motoric function and attention were tested. Small bowel biopsies were collected via routine gastroscopy at weeks 12 and 52 and were compared to baseline Marsh scores. Cognitive performance was compared to serum concentrations of tissue transglutaminase antibodies, biopsy outcomes and other biological markers. RESULTS: All patients had excellent adherence to the diet. Marsh scores improved significantly (P = 0.001, Friedman's test) and tissue transglutaminase antibody concentrations decreased from a mean of 58.4 at baseline to 16.8 U/mL at week 52 (P = 0.025). Four of the cognitive tests assessing verbal fluency, attention and motoric function showed significant improvement over the 12 months and strongly correlated with the Marsh scores and tissue transglutaminase antibody levels (r = 0.377-0.735; all P < 0.05). However, no meaningful patterns of correlations were found for nutritional or biochemical markers, or markers of intestinal permeability. CONCLUSIONS: In newly diagnosed coeliac disease, cognitive performance improves with adherence to the gluten-free diet in parallel to mucosal healing. Suboptimal levels of cognition in untreated coeliac disease may affect the performance of everyday tasks.

Dynamics of sleep-wake cyclicity across the fetal period in sheep (Ovis aries).

All adult mammals examined thus far exhibit sleep bout durations that follow an exponential distribution and wake bout durations that follow a power-law distribution. In altricial rodents such as rats and mice, exponential distributions of sleep bouts are found soon after birth, but the power-law distribution of wake bouts does not emerge until the third postnatal week. Also, both sleep and bouts consolidate across the early postnatal period. It is not known whether similar developmental processes occur in precocial species during the prenatal period. Here we characterize sleep-wake development in a precocial species, the domestic sheep (Ovis aries), from 114 to 148 days gestational age (DGA). Sleep and wake bout durations exhibited exponential distributions throughout the fetal period with some evidence of an emerging exponential-to-power-law transition for wake bouts toward the end of gestation. Both sleep and wake bouts consolidated in an orderly fashion across development and there was little evidence of circadian variation, even in the oldest subjects. These results indicate that similar patterns of sleep-wake organization are found prenatally in a precocial species as are found postnatally in altricial species. Data from more species are needed to fully realize the benefits of a developmental comparative approach for understanding the forces that have shaped the ontogeny and phylogeny of mammalian sleep.

Inactivation of astrocytic glutamine synthetase by hydrogen peroxide requires iron.

The specific activity of brain glutamine synthetase (GS) is lowered in several neurodegenerative diseases that involve iron-mediated oxidative stress. The present study has investigated whether H2O2 directly inactivates GS or whether GS is primarily inactivated by hydroxyl radicals that are produced by the Fenton reaction when H2O2 reacts with ferrous iron. Exposure of purified sheep brain GS to supraphysiological concentrations of H2O2 (1 mM for 30 min) reduced its specific activity by only 41%, indicating that the enzyme is fairly resistant to oxidation by peroxide. However, the enzyme was completely inactivated when co-incubated with H2O2, iron and ascorbate, indicating a vulnerability to oxidation by conditions that favour the production of hydroxyl radicals. Similarly, specific GS activity in cultured mouse astrocytes was resistant to supraphysiological concentrations of H2O2, with approximately 37% of activity remaining 3h after incubation with 1mM H2O2. This inactivation was prevented by the iron chelators 2,2'-dipyridyl or 1,10-phenanthroline, but not by their non-chelating analogues. These data suggest that inactivation of astrocytic GS is caused by H2O2 indirectly via the Fenton reaction as it required the presence of chelatable intracellular iron.

HIV-1 protein gp120 rapidly impairs memory in chicks by interrupting the glutamate-glutamine cycle.

Learning and memory impairments are frequently observed in patients suffering from AIDS Dementia Complex (ADC). These effects have been linked to the presence of gp120, an HIV viral coat glycoprotein. The present study investigated the possibility that gp120 prevents the uptake of extracellular glutamate by astrocytes, leading to an interruption of the glutamate-glutamine cycle and a subsequent impairment of memory. Ten microliters of 10nM gp120 was bilaterally injected into the region of the intermediate medial mesopallium of day-old chicks at various times before, or after, training using a single-trial passive avoidance task. Gp120 was found to significantly impair memory retention when injected 10-40 min after training. Memory impairments were evident within 5 min of gp120 administration and remained evident 24h later. Further, the amnestic effect of gp120 could be overcome with glutamine or with precursors of glutamate synthesis, but only weakly by glutamate. These results support the conclusion that the amnestic effect of gp120 is due to an impaired uptake of glutamate by astrocytes and a subsequent interruption of glutamine supply to neurones. The data indicate that the glutamate-glutamine cycle may be a useful therapeutic target in the treatment of ADC.

TNF alpha affects the expression of GFAP and S100B: implications for Alzheimer's disease.

Neurodegenerative disorders such as Alzheimer's disease are characterized by increased intracellular and extracellular concentrations of the astrocytic proteins glial fibrillary acidic protein (GFAP) and S100B. The present study examined the potential contribution of tumor necrosis factor alpha (TNFalpha) to these changes by measuring astrocyte viability along with the intracellular and extracellular expression of GFAP and S100B following exposure to this cytokine. Although TNFalpha did not affect astrocyte viability, the extracellular levels of both proteins were increased three-fold with associated reductions in immunocytochemical labeling.

Glutathione peroxidase-1 contributes to the protection of glutamine synthetase in astrocytes during oxidative stress.

Glutamine synthetase (GS) is an astrocytic enzyme that is essential for the glutamate-glutamine cycle between neurons and astrocytes. To measure the effects of oxidative stress on the activity of GS in astrocytes, astrocyte-rich primary cultures from the brains of wild-type and glutathione peroxidase-1 deficient mice (GPx1(-/-)) were exposed to a chronic hydrogen peroxide-generating system consisting of xanthine oxidase, hypoxanthine and superoxide dismutase. The specific activity of GS was strongly diminished by chronic exposure to hydrogen peroxide in astrocytes cultured from both mouse lines. After 60 min of oxidative stress in the presence of 5 mU/mL, 10 mU/mL and 20 mU/mL of xanthine oxidase, the specific GS activity of wild-type astrocytes was reduced to 47%, 22% and 13% of the initial activity, respectively. For all activities of xanthine oxidase applied, astrocytes from GPx1(-/-) mice experienced a significantly greater rate of GS inactivation compared to their wild-type counterparts. These results confirm that GS is sensitive to inactivation by chronic peroxide stress in viable astrocytes and show that glutathione peroxidase-1 helps to protect GS from inactivation by oxidative stress.

Altered cellular distribution of iron in rat cerebral cortex during the oestrous cycle.

Iron levels in blood, liver and the substantia nigra fluctuate during the oestrous cycle but it is not known whether the cellular distribution also changes. This study shows that during dioestrus, when serum levels of oestradiol are low, the amount of histochemically detectable iron in the cerebral cortex is significantly lower than in proestrus when oestradiol levels are highest. During dioestrus iron is concentrated within neurones, and the transition to proestrus is associated with a shift in iron localisation from neurones to vascular endothelial cells and oligodendrocytes. These data raise the possibility that changes in the concentration of serum oestrogen (or other reproductive hormones) during the oestrous cycle can influence the intercellular transport of iron in the brain.

Anti-AGEing defences against Alzheimer's disease.

Accumulation of insoluble protein deposits and their cross-linking by AGEs (advanced glycation end products) in the brain is a feature of aging and neurodegeneration, especially in AD (Alzheimer's disease). In AD, two types of fibrillar protein aggregates are present: extracellular deposits (plaques) consisting mainly of Abeta (beta-amyloid peptide), and intracellular deposits (tangles) composed predominantly of microtubule-associated protein tau. Both plaques and tangles are modified by AGEs, which occurs particularly at lysine and arginine residues. Interaction of a synthetic amyloid plaque (fibrillar Abeta) with microglia leads to a strong pro-inflammatory response, indicating that priming of immune cells with beta-amyloid potentiates their response to secondary stimuli such as AGE and cytokines such as interferon-gamma. Formation of hyperphosphorylated and cross-linked microtubule-associated protein tau aggregates, especially tau dimers as the first step in tangle formation, can be induced in vitro by the combination of okadaic acid, a PP2A phosphatase inhibitor, and methylglyoxal. These results suggest that excess production of reactive carbonyl compound ("carbonyl stress") and subsequent AGE formation can contribute to cross-linking of protein fibrils and to pathological pro-inflammatory signalling, which all contribute to pathological changes and dementia progression in AD. However, the human brain has developed the glyoxalase system, a most effective defence system to scavenge small dicarbonyl compounds such as glyoxal and methylglyoxal. Very importantly, this system needs GSH as a rate-limiting cofactor. Since GSH is limited under conditions of oxidative stress and inflammation, supplementation with antioxidants such as lipoic acid, vitamin E or flavonoids could indirectly strengthen the anti-glycation defence system in AD. In addition, synthetic carbonyl scavengers and anti-inflammatory drugs could also be valuable drugs for the "anti-glycation" treatment of AD.

Deposits of fibrillar A beta do not cause neuronal loss or ferritin expression in adult rat brain.

In Alzheimer's disease (AD), senile plaques containing amyloid-beta (Abeta) are associated with neurodegeneration, yet little quantitative data are available concerning the spatiotemporal patterns of neuronal death that result from exposure to Abeta deposits. Furthermore, plaques are accompanied by ferritin-rich cells but no data exist regarding the spatiotemporal expression of ferritin in response to Abeta. The present study has obtained such data after injecting aged Abeta peptide into the parietal cortex of adult rats. Injected deposits of fibrillar Abeta (1 microliter of 1 mM in saline) were cleared within 7 days but did not cause a significant increase in ferritin expression. Counts of dying neurones showed that human Abeta1-40 killed as many neurones as control injections of saline, while human Abeta1-42 and rat Abeta1-40 killed significantly less. We conclude that the fibrillar Abeta in plaques is not likely to be directly responsible for the neurodegeneration and ferritin expression that occurs in AD.

Potential neurotoxic inflammatory responses to Abeta vaccination in humans.

Studies in transgenic mouse models of Alzheimer's disease suggested the development of a vaccine that would induce the production of antibodies against amyloid-beta (Abeta) peptide, which in turn would stimulate microglia to phagocytose and remove senile plaques. However, some patients in the human clinical trials developed symptoms of brain inflammation, demonstrated by lymphocyte infiltration and elevated protein levels. These parameters are indicative of a breakdown of the blood-brain-barrier and entry of T-cells into the brain. Abeta-specific activated T-helper cells have the potential to amplify the existing pro-inflammatory conditions that are present in the brains of Alzheimer's disease patients. Cytotoxic T-cells might even attack the amyloid precursor protein which is present on the surface of many cells, including neurons. Before undertaking further vaccination trials there is a need to re-assess the risks associated with Abeta vaccination and with the therapeutic containment of a neuroinflammatory response. These risks may not be justified in the light of recent studies which have shown the efficacy of conventional, low-risk treatments in slowing the progress of AD.

Alzheimer's vaccine: a cure as dangerous as the disease?

Studies in transgenic mouse models of Alzheimer's disease suggested the potential for a vaccine development. However, some patients in the human clinical trials developed symptoms of brain inflammation, demonstrating the high risk of a deliberately induced auto-immune response.

Changes in the cellular distribution of glutamine synthetase in Alzheimer's disease.

The intracellular localization of glutamine synthetase (GS) in the inferior temporal cortices of non-demented elderly individuals was compared with that in brains affected by Alzheimer's disease (AD). The present study confirmed previous reports of a general decrease in GS expression in astrocytes and the expression of GS in some neurons. Several new observations were made: the morphology of astrocytes is generally unaffected by the presence of plaques, GS labeling is present in some diffuse plaques and occasional neuritic plaques, whereas the overall density of astrocytes increases 1.4-fold in AD. In addition, the present study found that the reduction in GS expression is almost entirely due to a loss of GS from perisynaptic regions of the neuropil and from the astrocytic endfeet that normally abut cortical blood vessels. These changes implicate astrocytes in glutamate excitotoxicity and ammonia neurotoxicity. It is suggested that it may be more fruitful to regard AD not as a neuronal disease, but as a disorder of astrocyte-neuron interactions.

Differential regulation of the dopamine D2 and D3 receptors by G protein-coupled receptor kinases and beta-arrestins.

The D(2) and D(3) receptors (D(2)R and D(3)R), which are potential targets for antipsychotic drugs, have a similar structural architecture and signaling pathway. Furthermore, in some brain regions they are expressed in the same cells, suggesting that differences between the two receptors might lie in other properties such as their regulation. In this study we investigated, using COS-7 and HEK-293 cells, the mechanism underlying the intracellular trafficking of the D(2)R and D(3)R. Activation of D(2)R caused G protein-coupled receptor kinase-dependent receptor phosphorylation, a robust translocation of beta-arrestin to the cell membrane, and profound receptor internalization. The internalization of the D(2)R was dynamin-dependent, suggesting that a clathrin-coated endocytic pathway is involved. In addition, the D(2)R, upon agonist-mediated internalization, localized to intracellular compartments distinct from those utilized by the beta(2)-adrenergic receptor. However, in the case of the D(3)R, only subtle agonist-mediated receptor phosphorylation, beta-arrestin translocation to the plasma membrane, and receptor internalization were observed. Interchange of the second and third intracellular loops of the D(2)R and D(3)R reversed their phenotypes, implicating these regions in the regulatory properties of the two receptors. Our studies thus indicate that functional distinctions between the D(2)R and D(3)R may be found in their desensitization and cellular trafficking properties. The differences in their regulatory properties suggest that they have distinct physiological roles in the brain.

Pre-exposure to (+/-)3,4-methylenedioxy-methamphetamine (MDMA) facilitates acquisition of intravenous cocaine self-administration in rats.

Pre-exposure to (+/-)3,4-methylenedioxymeth-amphetamine (MDMA) elevates locomotor activity and extracellular dopamine levels in the nucleus accumbens following a cocaine challenge. The present study determined whether MDMA-induced sensitization to the effects of cocaine could be demonstrated in rats self-administering cocaine. Three groups of rats were treated with saline (Sal), 5 mg/kg MDMA (once per day for 10 days; MDMA-5) or 20 mg/kg MDMA (twice per day for 4 days; MDMA-20). Subsequently, spontaneous acquisition of cocaine self-administration was measured in 12 daily 2-h sessions. During these test sessions, two response levers were present. Responses on one lever delivered infusions of 0.1 mg of cocaine; responses on the other lever had no programmed consequences. Group Sal showed a weak preference for the active lever; whereas, group MDMA-20 exhibited a stronger active lever preference. By day 12, the MDMA-20 group earned approximately twice the number of cocaine infusions as those in group SAL. At this time point, more than twice as many rats in group MDMA-20 were taking a minimum of 10 infusions per session, as compared to group Sal. Rats in group MDMA-5 did not seem to differ from group Sal in terms of lever discrimination, number of cocaine infusions, and percentage of rats obtaining a criterion of 10 infusions. These results indicate that pre-exposure to a high dose of MDMA may facilitate acquisition of cocaine self-administration. This dosing regimen of MDMA is likely to release DA and to be neurotoxic to 5-HT neurons. Either or both of these mechanisms could contribute to the ability of MDMA to facilitate cocaine self-administration.

Quantitative analysis of cell death and ferritin expression in response to cortical iron: implications for hypoxia-ischemia and stroke.

Iron that is not bound to storage proteins can catalyse the generation of toxic hydroxyl radicals. Iron can be released from brain storage proteins by hypoxic conditions, such as those that accompany stroke, and the situation can be compounded by iron released from hemoglobin in extravasated blood cells. Despite the neurotoxicity of iron, there is little quantitative data concerning the spatio-temporal extent of its toxicity in vivo. The present study measures the effects of a pathologically relevant concentration of iron (1.0 mM) on neuronal death and on ferritin expression in vivo. Injection of iron (1 microl ferric ammonium citrate) into rat parietal cortex resulted in 7.9-fold more ferritin-labeled cells than did control injections of ammonium citrate at 1 day post-injection. This elevated expression continued for at least 1 week. One day after injection, the mean number of Fluoro-Jade-labeled degenerating neurons in 100 microm sections passing through the center of ferric ammonium citrate injection sites was 664+/-64. This value was 4.5-fold higher than at ammonium citrate injection sites, and this difference increased to 56-fold by day three. By 5 days post-injection, few dying neurons were observed at the control sites, but neurodegeneration continued beyond a week at the iron-injected sites. Thus, iron released during a brief episode of hypoxia-ischemia or during a stroke may be neurotoxic for a protracted period. Therefore, our findings indicate that it may be beneficial to target iron-induced peroxidation throughout the first few weeks following an intracerebral hemorrhage or an hypoxic-ischemic episode.

Reducing post-tonsillectomy pain with cryoanalgesia: a randomized controlled trial.

OBJECTIVE/HYPOTHESIS: To evaluate the use of cryoanalgesia in reducing post-tonsillectomy pain. STUDY DESIGN: A prospective, randomized double-blind study of 59 consecutive patients (age range, 8-40 y) undergoing tonsillectomy for recurrent tonsillitis. METHODS: All patients underwent bipolar tonsillectomy. At the completion of the tonsillectomy patients were randomly assigned to a control or a cryotherapy group. The cryotherapy patients had both their tonsillar fossa "supercooled" to between -20 degrees C and -32 degrees C for 1 minute. Patients recorded their pain using a visual analogue scale over the next 10 days. Patients were also monitored for postoperative complications, time until resumption of a normal diet, time back to work or school, and analgesic consumption. RESULTS: The two groups were similar for age and sex. There was a 28.3% reduction in mean pain scores over the 10 days in the cryotherapy compared to the control group. This difference did not significantly depend on the day after operation or time of the day. Cryotherapy patients also returned to work or school, on average, 4 days earlier than controls. There was no significant difference in postoperative complications between the two groups. CONCLUSION: Cryotherapy is a new technique that significantly reduces post-tonsillectomy pain without evidence of causing additional complications.