Road safety: The influence of vibration frequency on driver drowsiness, reaction time, and driving performance

Driver drowsiness is a factor in at least 20% of serious motor vehicle accidents. Although research has shown that Whole-Body Vibration (WBV) can induce drowsiness in drivers, it is unknown whether particular frequencies are more problematic. The present study systematically investigated the influence of WBV frequency on driver drowsiness. Fifteen participants each undertook six 1-h sessions of simulated driving while being subjected to WBV of either 0 Hz (no vibration), 1-4 Hz, 4-8 Hz, 8-16 Hz, 16-32 Hz or 32-64 Hz. Subjective sleepiness, as measured by the Karolinska Sleepiness Scale (KSS), confirmed that drivers felt drowsier when exposed to the two lowest frequency ranges (1-4 Hz and 4-8 Hz). Reaction time, which measures attention and alertness, was significantly impaired by the two lowest frequency ranges. Objective driving performance measures (Standard Deviation of Lane Position (SDLP), Standard Deviation of (SD) Steering Angle, Time in Unsafe Zone) also showed significant degradation due to exposure to the two lowest frequency ranges. Exposure to 1-4 Hz or 4-8 Hz vibration caused attention to become significantly impaired within 15-20 min and driving performance to be significantly impaired by 30-35 min. The other frequency ranges had little or no effect. These findings point to a need to develop equivalent vibration-induced drowsiness contours that can be adopted as transportation safety standards.

Facilitators of Formal Help-Seeking for Adult Survivors of IPV in the United States: A Systematic Review

A survivor's decision to engage with formal services for experiences of intimate partner violence (IPV) is influenced by factors at the individual, interpersonal, and sociocultural levels. Understanding factors that facilitate survivors' choice to seek services could be beneficial to formal service providers including community agencies, health professionals, and the criminal justice system, providing guidance toward the development and implementation of accessible services for survivors of IPV. This systematic review of the literature aims to identify key factors that facilitate survivors' formal help-seeking. Ten electronic databases were searched for key terms related to help-seeking from formal services and facilitators of formal help-seeking. Articles were included in the review if the studies were conducted in the United States, focused on adults with experiences of IPV, and discussed facilitators of formal help-seeking. A total of 1,155 studies were initially identified, and after screening, 24 were included in the review. Seven factors were identified including provider knowledge, support, accessibility, desire to provide protection and to prevent future violence, and other factors such as knoweldge of and desire for services, policy factors, and personal factors. Findings demonstrate a need for more research on the facilitators of help-seeking among East Asian, South Asian, and Middle Eastern survivors living in the United States, as well as male-identified, trans, and gender nonconforming survivors. The review also indicates a need for culturally sensitive and accessible services that support survivors and the importance of raising awareness of the services and resources available for survivors.

"Is It My Responsibility?": A Qualitative Review of University Students' Perspectives on Bystander Behavior

Bystander interventions focus on framing violence as a community problem and encourage all community members to act as prosocial bystanders if they witness a dangerous situation. Research has demonstrated there are multiple barriers and facilitators that might discourage or encourage an individual to act as a prosocial bystander. A qualitative interpretive meta-synthesis (QIMS) of existing literature was conducted to determine university students' perspectives on bystander facilitators and barriers. A systematic search of the literature was completed to identify articles that included university students' perspectives on bystander facilitators and barriers, utilized a qualitative methodology, and contained participant quotations in the published article. The search yielded 181 articles and after screening 10 articles were included in the QIMS. The original themes and participant quotations were qualitatively coded to develop five new themes: (1) the impact of alcohol, (2) beliefs about responsibility, (3) peer perceptions, (4) indicators and situational dilemmas, and (5) the role of friendship and group impact. The results of this synthesis reveal important implications for the continued development of bystander intervention programs for universities. By incorporating the perspectives of university students, bystander intervention programs may be more effective at encouraging students to be prosocial bystanders by confronting perceived barriers to intervention.

A Systematic Review of Barriers to Formal Help Seeking for Adult Survivors of IPV in the United States, 2005-2019

For individuals experiencing intimate partner violence (IPV), formal services, including community agencies, health services, or the criminal justice system, are critical resources. Understanding the specific barriers that hinder or prevent survivors from seeking help from formal services could reveal important implications for the development of services for IPV as well as for members of other organizations who encounter survivors. The authors conducted a systematic review of the literature to identify barriers to help-seeking from formal services for survivors. Ten electronic databases were searched for key terms related to IPV, help seeking from formal services, and barriers to help seeking. Articles were included in the review if they were U.S.-based, contained samples that were adults who had experienced IPV, and discussed barriers to seeking help from formal services. An initial search yielded 1,155 articles and after screening, 29 articles were included in the review. Data were extracted to reveal the state of the literature regarding help-seeking barriers for survivors. Six barriers to help seeking were identified as follows: (1) lack of awareness, (2) access challenges, (3) consequences of disclosure, (4) lack of material resources, (5) personal barriers, and (6) system failures. These findings demonstrate the need for continued education surrounding available services for IPV as well as the continued development of resources that can mitigate personal barriers that survivors may face. Furthermore, these findings illuminate the necessity to increase the access of services, particularly for non-English speakers, immigrants and refugees, individuals with disabilities, men, and LGBTQIA identified individuals.

Using Community-Based Participatory Research Strategies in Age-Friendly Communities to Solve Mobility Challenges

The number of older adults is steadily increasing in the United States and across the globe. Aging is linked to an increased risk of disability. Disabilities that limit one or more major life activities such as seeing, hearing, walking, and motor skills impact a person's ability to drive a car. Low utilization of alternative transportation by older adults and people with disabilities may put them at risk for social isolation. Social isolation is associated with a variety of negative health outcomes. While communities are challenged to create available, acceptable, accessible, adaptable and affordable mobility options, there are widely held, inaccurate biases around older adults' abilities to contribute to the development and improvement of alternative transportation options. Gerontological social workers are well-positioned to address this bias. This paper presents a case study of a large metropolitan county in the Midwest where community-based participatory research (CBPR) strategies were used to engage older residents to support the development of alternative transportation options supporting the tenets of environmental justice.

Qualitative, Interpretive Metasynthesis of Women's Experiences of Intimate Partner Violence During Pregnancy

OBJECTIVE

To describe the perspectives of women who experienced intimate partner violence (IPV) during pregnancy through a qualitative, interpretive metasynthesis.

DATA SOURCES

We searched 12 electronic databases to identify articles on qualitative studies pertaining to women's experiences of IPV during pregnancy. We searched Academic Search Complete, AgeLine, CINAHL Complete, Family Studies Abstracts, MEDLINE, PsycARTICLES, Psychology and Behavioral Sciences, PsycINFO, Social Work Abstracts, Health Source-Consumer Edition, Health Source-Nursing/Academic Edition, and Humanities Full Text for articles published from 2008 through 2018.

DATA EXTRACTION

We used inclusion and exclusion criteria to identify eight reports of qualitative studies that contained direct quotations in which women described their experiences of IPV.

DATA SYNTHESIS

We used a methodologic reduction to provide a theoretical context that helped us synthesize the data to five key themes: Pregnancy Escalates Abuse, Concern for Unborn Fetus, Importance ofSupport, My Child Saved Me, and Pregnancy Is a Catalyst for Reflection.

CONCLUSION

The results of our synthesis illustrate the unique perspectives of women who experienced IPV during pregnancy. Understanding these experiences can help health care providers assist pregnant women through enhanced screenings and education. Health care providers can also help women identify resources for emotional and financial support as they determine the best courses of action for themselves and their children.

"I keep it to myself": A qualitative meta-interpretive synthesis of experiences of postpartum depression among marginalised women

Postpartum depression (PPD) is a significant public health concern due to the physical, emotional, economic, and life course outcomes. Rates of PPD are significantly higher for marginalised populations and can impact low-income, minority, and/or immigrant women differently when compared to white middle-class women. Commonly studied negative effects of PPD include poor health outcomes, mother-child bonding challenges, and negative child educational outcomes. However, research surveying the postpartum experience and negative outcomes among marginalised women is sparse. This study implemented a qualitative meta-interpretive synthesis (QIMS) methodology to synthesise themes across 12 qualitative research articles surveying postpartum experiences of marginalised women in North American countries. Articles included in the QIMS were extracted from online databases from a 10-year window spanning January 2008-2018. The guiding research question was "What are the PPD experiences of women belonging to marginalized populations?" Constant comparative analysis was used with coding in atlas.ti and themes were synthesised with input of all three authors. Five main themes emerged. The themes are (a) intersections of PPD and poverty, (b) culture and PPD, (c) pressures of mothering, (d) strengths and coping, and (e) abuse affects my PPD experience. Subthemes such as "I keep it to myself" relating to cultural response to PPD and idealised mothering were also discovered. Implications for social workers, nurses, and future research are discussed.

The Role of Social Support in the Link Between Economic Abuse and Economic Hardship

More data is needed about the pathways through which intimate partner violence (IPV) impacts the economic well-being of survivors. The current study assesses the moderating influence of social support on the association between economic abuse (EA) and economic hardship. Female participants (n = 435) were recruited to participate in a web-based survey which included standardized measures of EA, other forms of IPV, domains of social support, and economic hardship. Analysis included bivariate and multivariate regression with an investigation into interaction effects.Experiencing EA was significantly correlated with economic hardship, even with extent of physical and emotional IPV controlled. Both tangible and appraisal support had significant negative association with extent of material hardship. Significant interactions between forms of social support and economic abuse were observed. For those at high levels of economic abuse, support had less influence on economic hardship. A mix of direct economic aid, advocacy, education and support could provide a blueprint for addressing the economic hardship experiences of community-dwelling survivors of economic abuse. A comprehensive response to EA requires interventions aimed directly at economically controlling and exploitative tactics, including credit building, individual economic advocacy, and education. Interventions that seek to enhance survivors' access to social support may be necessary but not sufficient to buffer the impacts of violence on survivors' economic outcomes.

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.

Investigation of bacterial biofilm in the human middle ear using optical coherence tomography and acoustic measurements

Children with chronic otitis media (OM) often have conductive hearing loss which results in communication difficulties and requires surgical treatment. Recent studies have provided clinical evidence that there is a one-to-one correspondence between chronic OM and the presence of a bacterial biofilm behind the tympanic membrane (TM). Here we investigate the acoustic effects of bacterial biofilms, confirmed using optical coherence tomography (OCT), in adult ears. Non-invasive OCT images are collected to visualize the cross-sectional structure of the middle ear, verifying the presence of a biofilm behind the TM. Wideband measurements of acoustic reflectance and impedance (0.2-6 [kHz]) are used to study the acoustic properties of ears with confirmed bacterial biofilms. Compared to known acoustic properties of normal middle ears, each of the ears with a bacterial biofilm has an elevated power reflectance in the 1 to 3 [kHz] range, corresponding to an abnormally small resistance (real part of the impedance). These results provide assistance for the clinical diagnosis of a bacterial biofilm, which could lead to improved treatment of chronic middle ear infection and further understanding of the impact of chronic OM on conductive hearing loss. This article is part of a special issue entitled "MEMRO 2012".

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.

Safety of wireless capsule endoscopy in patients with implantable cardiac defibrillators

OBJECTIVES

Wireless video capsule endoscopy (CE) is a new technology that allows visualization of the entire small intestinal mucosa. It is indicated for the evaluation of obscure gastrointestinal bleeding (OGIB) and other disorders of the small intestine. Studies to date suggest that CE is safe and associated with few adverse events. A concern, which has not been studied, is the potential effect of CE on implanted cardiac devices such as implantable cardiac defibrillators (ICD) and other electromedical devices. We previously found CE to be safe in patients with cardiac pacemakers. The primary aim of this study was to evaluate the safety of CE in patients with ICDs who were being evaluated for OGIB. In addition, a secondary aim of the study was to determine whether ICDs had any effect on the images captured by CE.

METHODS

Patients referred for the evaluation of OGIB and who also had an ICD were enrolled into the study after informed consent. Five consecutive patients (four females and one male; mean age: 72 yr; range: 60-81 yr) with ICDs were studied. All patients had transvenous endocardial ICDs located in the chest. Prior to CE, patients had a baseline electrocardiogram (ECG) and ICD interrogation. Thereafter, CE was performed in a hospital setting with telemetry monitoring performed simultaneously. A post-procedure ICD interrogation was carried out to evaluate changes in programmed parameters. A cardiologist and ICD nurse specialist together reviewed both the telemetry monitor and the post-procedure ICD interrogation on each patient. When CE studies were reviewed, observations pertaining to technical difficulties and interference with video imaging were documented.

RESULTS

No arrhythmia or other adverse cardiac events were noted during capsule transmission. No interference by the ICD on the CE video images was seen.

CONCLUSIONS

CE was performed safely in these five patients with ICDs, and was not associated with any adverse cardiac events. ICDs also do not appear to interfere with video capsule imaging.

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 Aβ (β-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 Aβ) with microglia leads to a strong pro-inflammatory response, indicating that priming of immune cells with β-amyloid potentiates their response to secondary stimuli such as AGE and cytokines such as interferon-γ. 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.

Spontaneous motor activity in fetal and infant rats is organized into discrete multilimb bouts

Spontaneous motor activity (SMA) is a ubiquitous feature of fetal and infant behavior. Although SMA appears random, successive limb movements often occur in bouts. Bout organization was evident at all ages in fetal (embryonic day [E] 17-21) and infant (postnatal day [P] 1-9) rats, with nearly all bouts comprising 1-4 movements of different limbs. A computational model of SMA, including spontaneous activity of spinal motor neurons, intrasegmental and intersegmental interactions, recurrent inhibition, and descending influences, produced bouts with the same structure as that observed in perinatal rats. Consistent with the model, bouts were not eliminated on E20 after cervical spinal transection, suggesting that the brain is not necessary to produce bout organization. These investigations provide a foundation for understanding the contributions of SMA to neuromuscular and motor development.

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.

Neuronal expression of glutamine synthetase in Alzheimer's disease indicates a profound impairment of metabolic interactions with astrocytes

A considerable body of evidence indicates that the activity of glutamine synthetase is decreased in the cerebral cortices of brains affected by Alzheimer's disease. It is difficult to discern the reason for this decrease because it is not known whether the cellular distribution of glutamine synthetase is altered in Alzheimer's disease. Therefore the present study has used immunocytochemistry to compare the cellular distributions of glutamine synthetase in the inferior temporal cortices of six Alzheimer's diseased brains and six age-matched, non-demented brains. Double-label immunocytochemistry has been used to examine whether the distribution of cellular glutamine synthetase is influenced by the distribution of senile plaques. It was found that glutamine synthetase expression in astrocytes is diminished in Alzheimer's disease, particularly in the vicinity of senile plaques. The most striking finding of the present study was that glutamine synthetase was expressed in a subpopulation of pyramidal neurons in all six Alzheimer's diseased brains, whereas glutamine synthetase was not observed in any neurons from control brains. The changed expression of glutamine synthetase may be triggered by toxic agents in senile plaques, a reduced noradrenergic supply to the cerebral cortex, and increased brain ammonia levels. That such dramatic changes occur in the distribution of this critical, and normally stable enzyme, suggests that the glutamate-glutamine cycle is profoundly impaired in Alzheimer's disease. This is significant because impairments of the glutamate-glutamine cycle are known to cause alterations of mood and behaviour, disturbance of sleeping patterns, amnesia, confusion and reduced awareness. Since these behavioural changes are also seen in Alzheimer's disease, it is speculated that they might be attributable to the reduced expression of glutamine synthetase or to impairments of the glutamate-glutamine cycle.

Spontaneous motor activity in fetal and infant rats is organized into discrete multilimb bouts

Spontaneous motor activity (SMA) is a ubiquitous feature of fetal and infant behavior. Although SMA appears random, successive limb movements often occur in bouts. Bout organization was evident at all ages in fetal (embryonic day [E] 17-21) and infant (postnatal day [P] 1-9) rats, with nearly all bouts comprising 1-4 movements of different limbs. A computational model of SMA, including spontaneous activity of spinal motor neurons, intrasegmental and intersegmental interactions, recurrent inhibition, and descending influences, produced bouts with the same structure as that observed in perinatal rats. Consistent with the model, bouts were not eliminated on E20 after cervical spinal transection, suggesting that the brain is not necessary to produce bout organization. These investigations provide a foundation for understanding the contributions of SMA to neuromuscular and motor development.

Inhibition of Müller cell glutamine synthetase rapidly impairs the retinal response to light

It is widely assumed that neurones have sufficient metabolic reserves to allow them to function independently of glial cells for extended periods. The present study investigates the length of time taken before retinal neurones no longer respond normally to light after the inhibition of glial enzymes that are involved in the synthesis of precursors of neuronal glutamate. The glutamine synthetase inhibitor methionine sulfoximine, when injected intraocularly in Wistar rats, caused a time- and dose-dependent suppression of the scotopic electroretinogram b-wave. At the highest dosage (40 mM) the b-wave was significantly reduced within 2 min of injection. Because the b-wave is an indicator of neurotransmission in the retina, it is deduced that inhibition of glutamine synthetase rapidly blocks glutamatergic neurotransmission. Immunohistochemistry revealed a depletion of neuronal glutamate and an accumulation of glutamate in Müller glial cells, in a time course that matched the b-wave suppression. The b-wave was quickly restored by injection of glutamine (4 mM). The rapid reduction of glutamatergic transmission after methionine sulfoximine administration challenges the view that neurones have sufficient reserves to allow them to function independently for extended periods; instead, it indicates that glia are essential for the moment-to-moment sustenance of neuronal function.

Alzheimer's disease and inflammation: a review of cellular and therapeutic mechanisms

1. Of the neurodegenerative diseases that cause dementia, Alzheimer's disease (AD) is the most common. Three major pathologies characterize the disease: senile plaques, neurofibrillary tangles and inflammation. We review the literature on events contributing to the inflammation and the treatments thought to target this pathology. 2. The senile plaques of AD consist primarily of complexes of the beta-amyloid protein. This protein is central to the pathogenesis of the disease. 3. Inflammatory microglia are consistently associated with senile plaques in AD, although the classic inflammatory response (immunoglobulin and leucocyte infiltration) is absent. beta-Amyloid fragments appear to mediate such inflammatory mechanisms by activating the complement pathway in a similar fashion to immunoglobulin. 4. Epidemiological studies have identified a reduced risk of AD in patients with arthritis and in leprosy patients treated with anti-inflammatory drugs. Longitudinal studies have shown that the consumption of anti-inflammatory medications reduces the risk of AD only in younger patients (< 75 years). 5. There is a considerable body of in vitro evidence indicating that the inflammatory response of microglial cells is reduced by non-steroidal anti-inflammatory drugs (NSAID). However, no published data are available concerning the effects of these medications on brain pathology in AD. 6. Cyclo-oxygenase 2 enzyme is constitutively expressed in neurons and is up-regulated in degenerative brain regions in AD. Non-steroidal anti-inflammatory drugs may reduce this expression. 7. Platelets are a source of beta-amyloid and increased platelet activation and increased circulating beta-amyloid have been identified in AD. Anti-platelet medication (including NSAID) would prevent such activation and its potentially harmful consequences. 8. Increased levels of luminal beta-amyloid permeabilizes the blood-brain barrier (BBB) and increases vasoconstriction of arterial vessels, paralleling the alterations observed with infection and inflammation. Cerebral amyloidosis is highly prevalent in AD, compromising the BBB and vasoactivity. Anti-inflammatory medications may alleviate these problems.

Astrocytes: glutamate producers for neurons

In order for the brain to use the common amino acid glutamate as a neurotransmitter, it has been necessary to introduce a series of innovations that greatly restrict the availability of glutamate, so that it cannot degrade the signal-to-noise ratio of glutamatergic neurons. The most far-reaching innovations have been: i) to exclude the brain from access to glutamate in the systemic circulation by the blood-brain barrier, thereby making the brain autonomous in the production and disposal of glutamate; ii) to surround glutamatergic synapses with glial cells and endow these cells with much more powerful glutamate uptake carriers than the neurons themselves, so that most released transmitter glutamate is rapidly inactivated by uptake in glial cells; iii) to restrict to glial cells a key enzyme (glutamine synthetase) that is involved in the return of accumulated glutamate to neurons by amidation to glutamine, which has no transmitter activity, and can be safely released to the extracellular space, returned to neurons and deaminated to glutamate; iv) to restrict to glial cells two key enzymes (pyruvate carboxylase and cytosolic malic enzyme) that are involved in, respectively, de novo synthesis (from glucose) of the carbon skeleton of glutamate, and the return of the carbon skeleton of excess glutamate to the metabolic pathway for glucose oxidation. As a consequence of these innovations, neurons constantly require new carbon skeletons from glial to sustain their TCA cycle. When these supplies are withdrawn, neurons are unable to generate amino acid transmitters and their rate of oxidative metabolism is impaired. Given the commensalism that exists between neurons and glia, it may be fruitful to view brain function not just as a series of interactions between neurons, but also as a series of interactions between neurons and their collaborating glial cells.

Effects of amniotic fluid on opioid activity and fetal responses to chemosensory stimuli

The present study provides evidence that milk or amniotic fluid (AF) can promote activity in the endogenous opioid system of the E20 rat fetus. Fetal responses to a chemosensory test stimulus (lemon) were reduced after intraoral infusion of milk (Experiment 1). The effect of milk was mimicked by the kappa opioid agonist U50,488 (Experiment 2), and blocked by pretreatment with naloxone (Experiment 3), confirming opioid involvement. E20 fetuses also showed reduced responses after exposure to AF collected on E20 or E21, but not to AF collected on E19 (Experiment 4). The effects of AF on fetal responses were blocked by pretreatment with naloxone (Experiment 5), and by a selective kappa opioid antagonist, but not by a mu antagonist (Experiment 6). These findings suggest that the fetus may experience activation of the kappa opioid system for several days before birth as a consequence of its exposure to AF in utero.

The development of nuchal atonia associated with active (REM) sleep in fetal sheep: presence of recurrent fractal organization

The behavioral state of active or rapid eye movement sleep (REMS) is dominant during fetal life and may play an important role in brain development. One marker of this state in fetal sheep is neck nuchal muscle atonia (NA). We observed burst within burst NA patterns suggestive of recurrent fractal organization in continuous 13 day in utero recordings of NA during the third trimester. Consistent with fractal renewal processes, the cumulative mean and standard deviation (SD) diverged over this time and the tail of NA distributions fit a stable Lévy law with exponents that remained invariant over the periods of development examined. The Hurst exponent, a measure of self-affine fractals, indicated that long-range correlations among NA intervals were present throughout development. A conserved complex fractal structure is apparent in NA which may help elucidate ambiguities in defining fetal states as well as some unique properties of fetal REMS.

Stimulus contingencies that permit classical conditioning of opioid activity in the rat fetus

In a prenatal model of classical conditioning, rat fetuses received presentations of an artificial nipple (conditioned stimulus; CS) paired with milk (unconditioned stimulus). Infusion of milk promotes activity in the kappa opioid system of the fetus, but after 2, 3, or 6 pairings with the artificial nipple, milk evoked both kappa and mu opioid activity. The nipple CS has no effect on opioid activity, but after pairing with milk evoked a mu opioid response. Conditioned mu opioid activity was evident in 60% of subjects tested after 1 paired conditioning trial. Significantly more fetal subjects (90%) exhibited conditioned opioid activity if preexposed to the nipple twice before conditioning. CS preexposure altered behavior during the conditioning trial, with preexposed fetuses showing more pronounced responses to milk infusion. Exposure to familiar stimuli facilitates classical conditioning of physiological responses, including opioid activity, during the first suckling episode.

Stimulus contingencies that permit classical conditioning of opioid activity in the rat fetus

In a prenatal model of classical conditioning, rat fetuses received presentations of an artificial nipple (conditioned stimulus; CS) paired with milk (unconditioned stimulus). Infusion of milk promotes activity in the kappa opioid system of the fetus, but after 2, 3, or 6 pairings with the artificial nipple, milk evoked both kappa and mu opioid activity. The nipple CS has no effect on opioid activity, but after pairing with milk evoked a mu opioid response. Conditioned mu opioid activity was evident in 60% of subjects tested after 1 paired conditioning trial. Significantly more fetal subjects (90%) exhibited conditioned opioid activity if preexposed to the nipple twice before conditioning. CS preexposure altered behavior during the conditioning trial, with preexposed fetuses showing more pronounced responses to milk infusion. Exposure to familiar stimuli facilitates classical conditioning of physiological responses, including opioid activity, during the first suckling episode.

Relationships between Müller cells and neurons in a primitive tetrapod, the Australian lungfish

We recently proposed a model of cytogenesis which assumes that primitive ancestral mammals and premammalian vertebrates had a retinal composition that consisted of about seven neurons per Müller cell, comprising 1-2 cone photoreceptors, 1-2 rod photoreceptors, 2-3 bipolar cells, 1-2 amacrine cells, less than 1 ganglion cell, and less than 1 horizontal cell (Reichenbach & Robinson, 1995). The Australian lungfish (Neoceratodus forsteri) closely resembles the lobe-finned ancestors of land vertebrates, and has an extremely plesiomorphic nervous system. The present study, therefore, has examined the relative frequencies of retinal neurons and Müller cells (identified by immunolabelling for glutamine synthetase) in the lungfish retina. It was found that for each Müller cell there is an average of 1.9 cone photoreceptors, 1.7 rod photoreceptors, 3.1 amacrine/bipolar/horizontal cells, and 0.6 ganglion cells; amounting to a ratio of 7.3 neurons per Müller cell. These results support our conjecture that the sequence of cytogenesis in mammals is constrained by a developmental program that predates the evolution of mammals. The study also provides the first detailed morphological descriptions of lungfish Müller cells and their relationship with adjacent neurons. It was found that individual Müller cells in lungfish have a volume (more than 12,000 microns3) that is an order of magnitude higher than in mammals, yet the proportion of total retinal volume occupied by these cells (20%) is very similar.

Chicks injected with antisera to either S-100 alpha or S-100 beta protein develop amnesia for a passive avoidance task

The cellular expression of S-100 beta protein is upregulated in Alzheimer's disease and in Down's syndrome, and this protein has been implicated in memory-related processes in laboratory animals. However, the possibility that the alpha subunit of S-100 is also involved in memory has not yet been examined. In the present study, day-old black Australorp white Leghorn cockerel chicks (Gallus domesticus) received injections of monoclonal antisera to S-100 alpha (1:50) or S-100 beta (1:500) into each hemisphere immediately after training on a one-trial passive avoidance task. The chicks displayed significantly lower retention levels than control birds that had been injected with antisera to carbonic anhydrase, or with saline (p < .01). S-100 alpha antisera had an amnestic effect when injected between 0 and 20 min after training, with memory deficits occurring from 30 min post-learning, at the point of transition between the A and the B phases of the Gibbs-Ng intermediate memory stage. By contrast, the S-100 beta antisera needed to be injected either 5 min before or immediately after training and produced amnesia 10 min earlier, at the start of the A phase of the intermediate memory stage. We conclude that the two subunits of the S-100 protein are required at different points in the sequence of events leading to the consolidation of passive avoidance memory.

Distribution of glutamine synthetase in the chick forebrain: implications for passive avoidance memory formation

The glial enzyme glutamine synthetase (GS) converts glutamate to glutamine; the latter is used by neurons for the resynthesis of glutamate and GABA. We have used a monoclonal antibody to GS to examine the regional distribution of this enzyme in the forebrains of day-old chicks. GS was detected in glia throughout the rostral and caudal regions of the forebrain and was particularly intense in the hippocampus, area parahippocampus and parts of the hyperstriatal and paleostriatal complex, regions widely considered to be involved in memory formation. Thus, our data provide an anatomical framework for the conclusion that neurons require the support of glia in order to restock their glutamate and/or GABA transmitter supplies during memory processing.

Complex roles of glutamate in the Gibbs-Ng model of one-trial aversive learning in the new-born chick

Glutamate is the most widespread excitatory transmitter in the CNS and is probably involved in LTP, a neural phenomenon which may be associated with learning and memory formation. Intracerebral injection of large amounts of glutamate between 5 min and 2.5 min after passive avoidance learning in young chicks inhibits short-term memory, which occurs between 0 and 10 min post-learning in a three-stage model of memory formation first established by Gibbs and Ng(25) [Physiol. Behav. 23:369-375; 1979]. This effect may be attributed to non-specific excitation. Blockade of glutamate uptake by L-aspartic and beta-hydroxamate also abolishes this stage of memory, provided the drug is administered within 2.5 min of learning. Interference with either production of percursors for transmitter glutamate in astrocytes or with glutamate receptors is also detrimental to memory formation, but the effects appear much later. After its release from glutamatergic neurons, glutamate is, to a large extent, accumulated into astrocytes where it is converted to glutamine, which can be returned to glutamatergic neurons and reutilized for synthesis of transmitter glutamate, and partly oxidized as a metabolic substrate. The latter process leads to a net loss of transmitter glutamate which can be compensated for by de novo synthesis of a glutamate precursor alpha-ketoglutarate (alpha KG) in astrocytes, a process which is inhibited by the astrocyte-specific toxin fluoroacetate (R. A. Swanson, personal communication). Intracerebral injection of this toxin abolishes memory during an intermediate stage of memory processing occurring between 20 and 30 min post-training (50) [Cog. Brain Res, 2:93-102; 1994]. Injection of methionine sulfoximine (MSO), a specific inhibitor of glutamine synthetase, which interferes with the re-supply of transmitter glutamate to neurons by inhibition of glutamine synthesis in astrocytes, has a similar effect. This effect of MSO is prevented by intracerebral injection of glutamate, glutamine, or a combination and alpha KG and alanine. MSO must be administered before learning, but does not interfere with acquisition since short-term memory remains intact. Administration of either the NMDA antagonist AP5, the AMPA antagonist DNQX, or the metabotropic receptor antagonist MCPF, also induces amnesia. Memory loss in each case does not occur until after 70 min post-training, during a protein synthesis-dependent long-term memory stage which begins at 60 min following learning. However, to be effective, AP5 must be administered within 60 s following learning, MCPG before 15 min post-learning, and DNQX between 15 and 25 min after learning. Together, these findings suggest that learning results in an immediate release of glutamate, followed by a secondary release of this transmitter at later stages of processing of the memory trace, and that one or both of these increases in extracellular glutamate concentration are essential for the consolidation of long-term memory. Since both fluoroacetate and MSO act exclusively on glial cells, the findings also show that neuronal-glial interactions are necessary during the establishment of memory.

Contractile activity of the uterus prior to labor alters the temporal organization of spontaneous motor activity in the fetal sheep

Contractile activity of the uterus before the onset of labor (uterine contractures) has been described in a number of species and provides a powerful source of repeated stimulation for the fetus throughout much of gestation. To understand how fetal behavior responds to this dynamic aspect of the intrauterine environment, we investigated the effects of uterine contractures on the temporal organization of spontaneous motor activity in the fetal sheep during the last fifth of gestation. Eleven fetuses were instrumented on 113-116 days of gestation (dGA). Electromyogram (EMG) activity was recorded from flexor and extensor muscles in the fetal forelimbs and hindlimbs, and from the uterus. Pooled limb EMG activity from 2300 hr to 0700 hr on 118, 125, 132, and 139 dGA before, during, and after uterine contractures was spectral analyzed to detect and quantify the cyclic organization in fetal motor activity. There was strong evidence of cyclic organization in fetal motor activity (CM) at each gestational age, similar to what has been described in the fetal rat and human. There was no evidence of developmental changes in the baseline spectral measures of CM. The most prominent feature of the response of CM to uterine contractures was a transient decrease in irregularity at 118-132 dGA. The strength of CM increased during contractures at 125 and 132 dGA, and a slight acceleration of CM during contractures was detected at 118 and 139 dGA. The results demonstrate that the stimulation associated with contractures influences an important source of complexity in early behavioral organization. The results are consistent with speculation by others that uterine contractures might induce transient cerebral hypoxemia in the fetus, and suggest that conditions established in the first few minutes of sustained uterine activity constitute the effective perturbation of CM.