Mortality from neurodegenerative disease and exposure to extremely low-frequency magnetic fields: 31 years of observations on Swiss railway employees

AIMS: The objective of the present study was to investigate the relationship between extremely low-frequency magnetic field (ELF-MF) exposure and mortality from several neurodegenerative conditions in Swiss railway employees. METHODS: We studied a cohort of 20,141 Swiss railway employees with 464,129 person-years of follow-up between 1972 and 2002. For each individual, cumulative exposure was calculated from on-site measurements and modelling of past exposure. We compared cause-specific mortality in highly exposed train drivers (mean exposure: 21 microT) with less exposed occupational groups (for example station masters: 1 microT). RESULTS: The hazard ratio for train drivers compared to station masters was 1.96 [95% confidence interval (CI) = 0.98-3.92] for senile dementia and 3.15 (95% CI = 0.90-11.04) for Alzheimer's disease. For every 10 microT years of cumulative exposure senile dementia mortality increased by 5.7% (95% CI = 1.3-10.4), Alzheimer's disease by 9.4% (95% CI = 2.7-16.4) and amyotrophic lateral sclerosis by 2.1% (95% CI = -6.8 to 11.7). There was no evidence for an increase in mortality from Parkinson's disease and multiple sclerosis. CONCLUSIONS: This study suggests a link between exposure to ELF-MF and Alzheimer's disease and indicates that ELF-MF might act in later stages of the disease process.

E- and P-selectin are not required for the development of experimental autoimmune encephalomyelitis in C57BL/6 and SJL mice

In multiple sclerosis and in its animal model experimental autoimmune encephalomyelitis (EAE), inflammatory cells migrate across the endothelial blood-brain barrier (BBB) and gain access to the CNS. It is well-established that alpha4 integrins are actively involved in leukocyte recruitment across the BBB during EAE. In contrast, the role of endothelial E- and P-selectin in this process has been a controversial issue. In this study, we demonstrate that P-selectin protein can be detected in meningeal blood vessel endothelial cells in healthy SJL and C57BL/6 mice and on rare parenchymal CNS blood vessels in C57BL/6, but not SJL, mice. During EAE, expression of P-selectin but not E-selectin was found up-regulated on inflamed CNS microvessels surrounded by inflammatory infiltrates irrespective of their meningeal or parenchymal localization with a more prominent immunostaining detected in C57BL/6 as compared with SJL mice. P-selectin immunostaining could be localized to CNS endothelial cells and to CD41-positive platelets adhering to the vessel wall. Despite the presence of P-selectin in wild-type mice, E/P-selectin-deficient SJL and C57BL/6 mice developed clinical EAE indistinguishable from wild-type mice. Absence of E- and P-selectin did neither influence the activation of myelin-specific T cells nor the composition of the cellular infiltrates in the CNS during EAE. Finally, endothelial-specific tetracycline-inducible expression of E-selectin at the BBB in transgenic C57BL/6 mice did not alter the development of EAE. Thus, E- and P-selectin are not required for leukocyte recruitment across the BBB and the development of EAE in C57BL/6 and in SJL mice.

A review identifies and classifies reasons for ordering diagnostic tests

OBJECTIVE: To consider the reasons and context for test ordering by doctors when faced with an undiagnosed complaint in primary or secondary care. STUDY DESIGN AND SETTING: We reviewed any study of any design that discussed factors that may affect a doctor's decision to order a test. Articles were located through searches of electronic databases, authors' files on diagnostic methodology, and reference lists of relevant studies. We extracted data on: study design, type of analysis, setting, topic area, and any factors reported to influence test ordering. RESULTS: We included 37 studies. We carried out a thematic analysis to synthesize data. Five key groupings arose from this process: diagnostic factors, therapeutic and prognostic factors, patient-related factors, doctor-related factors, and policy and organization-related factors. To illustrate how the various factors identified may influence test ordering we considered the symptom low back pain and the diagnosis multiple sclerosis as examples. CONCLUSIONS: A wide variety of factors influence a doctor's decision to order a test. These are integral to understanding diagnosis in clinical practice. Traditional diagnostic accuracy studies should be supplemented with research into the broader context in which doctors perform their work.

Brain endothelial PPARgamma controls inflammation-induced CD4+ T cell adhesion and transmigration in vitro

An important step in the pathogenesis of multiple sclerosis is adhesion and transmigration of encephalitogenic T cells across brain endothelial cells (EC) which strongly relies on interaction with EC-expressed adhesion molecules. We provide molecular evidence that the transcription factor peroxisome proliferator-activated receptor gamma (PPARgamma) is a negative regulator of brain EC inflammation. The PPARgamma agonist pioglitazone reduces transendothelial migration of encephalitogenic T cells across TNFalpha-stimulated brain EC. This effect is clearly PPARgamma mediated, as lentiviral PPARgamma overexpression in brain EC results in selective abrogation of inflammation-induced ICAM-1 and VCAM-1 upregulation and subsequent adhesion and transmigration of T cells. We therefore propose that PPARgamma in brain EC may be exploited to target detrimental EC-T cell interactions under inflammatory conditions.

Therapeutic targeting of leukocyte trafficking across the blood-brain barrier

The central nervous system (CNS) has long been regarded as an immune privileged organ implying that the immune system avoids the CNS not to disturb its homeostasis, which is critical for proper function of neurons. Meanwhile, it is accepted that immune cells do in fact gain access to the CNS and that immune responses are mounted within this tissue. However, the unique CNS microenvironment strictly controls these immune reactions starting with tightly regulating immune cell entry into the tissue. The endothelial blood-brain barrier (BBB) and the epithelial blood-cerebrospinal fluid (CSF) barrier control immune cell entry into the CNS, which is rare under physiological conditions. During a variety of pathological conditions of the CNS such as viral or bacterial infections, or during inflammatory diseases such as multiple sclerosis (MS), immunocompetent cells readily traverse the BBB and subsequently enter the CNS parenchyma. Most of our current knowledge on the molecular mechanisms involved in immune cell entry into the CNS has been derived from studies performed in experimental autoimmune encephalomyelitis (EAE), an animal model for MS. Thus, a large part of our current knowledge on immune cell entry across the BBBs is based on the results obtained in this animal model. Similarly, knowledge on the benefits and potential risks associated with therapeutic targeting of immune cell recruitment across the BBB in human diseases are mostly derived from such treatment regimen in MS. Other mechanisms of immune cell entry into the CNS might therefore apply under different pathological conditions such as bacterial meningitis or stroke and need to be considered.

Mechanisms of unexpected death and autopsy findings in Leigh syndrome (subacute necrotising encephalomyelopathy)

A 21-year-old previously-well woman who was undergoing medical investigations for problems with balance and suspected multiple sclerosis, developed a headache and breathing difficulties, and died suddenly and unexpected at home. The autopsy was unremarkable except for pulmonary and cerebral oedema. However, subsequent microscopy of the brain revealed characteristic features of Leigh syndrome with multifocal areas of astrogliosis, capillary proliferation, and parenchymal vacuolation. While Leigh syndrome is more commonly diagnosed in infancy, manifestations may occur throughout early life into adulthood. Sudden and unexpected death is a rare presentation that may be associated with cerebral necrosis and oedema. An awareness of the variable manifestations of Leigh syndrome is necessary in forensic practice as not all cases will present in a typical manner and sudden death may occur before a diagnosis has been established. The heritable nature of this condition makes accuracy of diagnosis essential.

Diagnostic workup of patients with acute transverse myelitis: spectrum of clinical presentation, neuroimaging and laboratory findings

STUDY DESIGN: Retrospective 9-year survey. OBJECTIVES: Clinical presentation of acute myelitis syndromes is variable, and neuroimaging and laboratory findings are not specific enough to establish the diagnosis with certainty. We evaluated the spectrum clinical features and paraclinical findings encountered during diagnostic workup and aiding the diagnosis. SETTING: Department of Neurology, Inselspital Bern, Switzerland. MATERIAL: Charts and magnetic resonance imaging (MRI) of 63 patients discharged with the diagnosis of acute transverse myelitis. RESULTS: The diagnosis was supported by abnormal MRI and cerebrospinal fluid (CSF) findings in 52 patients (82.5%) and suspected in the remaining either because of a spinal cord MRI lesion suggestive of myelitis (n=5), or abnormal CSF findings (n=4), or electrophysiological evidence of a spinal cord dysfunction (n=2). Clinical impairment was mild (ASIA D) in the majority. All patients had sensory disturbances, whereas motor deficit and autonomic dysfunction were less frequent. Neurological levels were mainly located in cervical or thoracic dermatomes. Spinal cord lesions were visualized by MRI in 90.4% of the patients and distributed either in the cervical or thoracic cord, or both. Multiple lesions were present in more than half of the patients, and lateral, centromedullary and posterior locations were most common. A high percentage of multiple sclerosis (MS)-typical brain lesions and CSF findings suggested a substantial number of MS-related myelitis in our cohort. CONCLUSION: The diagnostic workup of acute myelitis discloses a broad spectrum of CSF or MRI findings, and may be associated with diagnostic uncertainty due to lack of specific CSF or MRI features, or pathological findings.

Residence near power lines and mortality from neurodegenerative diseases: longitudinal study of the Swiss population

The relation between residential magnetic field exposure from power lines and mortality from neurodegenerative conditions was analyzed among 4.7 million persons of the Swiss National Cohort (linking mortality and census data), covering the period 2000-2005. Cox proportional hazard models were used to analyze the relation of living in the proximity of 220-380 kV power lines and the risk of death from neurodegenerative diseases, with adjustment for a range of potential confounders. Overall, the adjusted hazard ratio for Alzheimer's disease in persons living within 50 m of a 220-380 kV power line was 1.24 (95% confidence interval (CI): 0.80, 1.92) compared with persons who lived at a distance of 600 m or more. There was a dose-response relation with respect to years of residence in the immediate vicinity of power lines and Alzheimer's disease: Persons living at least 5 years within 50 m had an adjusted hazard ratio of 1.51 (95% CI: 0.91, 2.51), increasing to 1.78 (95% CI: 1.07, 2.96) with at least 10 years and to 2.00 (95% CI: 1.21, 3.33) with at least 15 years. The pattern was similar for senile dementia. There was little evidence for an increased risk of amyotrophic lateral sclerosis, Parkinson's disease, or multiple sclerosis.

The blood-central nervous system barriers actively control immune cell entry into the central nervous system

Before entering the central nervous system (CNS) immune cells have to penetrate any one of its barriers, namely either the endothelial blood-brain barrier, the epithelial blood-cerebrospinal fluid barrier or the tanycytic barrier around the circumventricular organs, all of which maintain homeostasis within the CNS. The presence of these barriers in combination with the lack of lymphatic vessels and the absence of classical MHC-positive antigen presenting cells characterizes the CNS as an immunologically privileged site. In multiple sclerosis a large number of inflammatory cells gains access to the CNS parenchyma. Studies performed in experimental autoimmune encephalomyelitis (EAE), a rodent model for multiple sclerosis, have enabled us to understand some of the molecular mechanisms involved in immune cell entry into the CNS. In particular, the realization that /alpha4-integrins play a predominant role in leukocyte trafficking to the CNS has led to the development of a novel drug for the treatment of relapsing-remitting multiple sclerosis, which targets /alpha4-integrin mediated immune cell migration to the CNS. At the same time, the involvement of other adhesion and signalling molecules in this process remains to be investigated and novel molecules contributing to immune cell entry into the CNS are still being identified. The entire process of immune cell trafficking into the CNS is strictly controlled by the brain barriers not only under physiological conditions but also during neuroinflammation, when some barrier properties are lost. Thus, immune cell entry into the CNS critically depends on the unique characteristics of the brain barriers maintaining CNS homeostasis.

L-Selectin-deficient SJL and C57BL/6 mice are not resistant to experimental autoimmune encephalomyelitis

L-selectin has been suggested to play a role in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. Here we demonstrate that L-selectin(-/-) SJL mice are susceptible to proteolipid protein (PLP)-induced EAE because the compromised antigen-specific T cell proliferation in peripheral lymph nodes is fully compensated by the T cell response raised in their spleen. Transfer of PLP-specific T cells into syngeneic recipients induced EAE independent of the presence or absence of L-selectin on PLP-specific T cells or in the recipient. Leukocyte infiltration into the central nervous system parenchyma was detectable independent of the mode of disease induction and the presence or absence of L-selectin. In addition, we found L-selectin(-/-) C57BL/6 mice to be susceptible to myelin oligodendrocyte glycoprotein-induced EAE. Taken together, we demonstrate that in SJL and C57BL/6 mice L-selectin is not required for EAE pathogenesis. The apparent discrepancy of our present observation to previous findings, demonstrating a role of L-selectin in EAE pathogenesis in C57BL/6 mice or myelin-basic protein (MBP)-specific TCR-transgenic B10.PL mice, may be attributed to background genes rather than L-selectin and to a unique role of L-selectin in EAE pathogenesis in MBP-TCR-transgenic mice.

Immune cell entry into the central nervous system: involvement of adhesion molecules and chemokines

In multiple sclerosis and in its animal model experimental autoimmune encephalomyelitis (EAE), inflammatory cells migrate across the highly specialized endothelial blood-brain barrier (BBB) and gain access to the central nervous system (CNS). It is well established that leukocyte recruitment across this vascular bed is unique due to the predominant involvement of alpha4-integrins in mediating the initial contact to as well as firm adhesion with the endothelium. In contrast, the involvement of the selectins, L-selectin, E- and P-selectin and their respective carbohydrate ligands such as P-selectin glycoprotein (PSGL)-1 in this process has been controversially discussed. Intravital microscopic analysis of immune cell interaction with superficial brain vessels demonstrates a role for E- and P-selectin and their common ligand PSGL-1 in lymphocyte rolling. However, E- and P-selectin-deficient SJL- or C57Bl/6 mice or PSGL-1-deficient C57Bl/6 mice develop EAE indistinguishable from wild-type mice. Considering these apparently discrepant observations, it needs to be discussed whether the molecular mechanisms involved in leukocyte trafficking across superficial brain vessels are irrelevant for EAE pathogenesis or whether the therapeutic efficacy of targeting alpha4-integrins in EAE is truly dependent on the inhibition of leukocyte trafficking across the BBB.

Interferon-beta stabilizes barrier characteristics of the blood-brain barrier in four different species in vitro

BACKGROUND: Blood-brain barrier (BBB) breakdown is an early event in the pathogenesis of multiple sclerosis (MS). In a previous study we have found a direct stabilization of barrier characteristics after treatment of bovine brain capillary endothelial cells (BCECs) with human recombinant interferon-beta-1a (IFN-beta-1a) in an in vitro BBB model. In the present study we examined the effect of human recombinant IFN-beta-1a on the barrier properties of BCECs derived from four different species including humans to predict treatment efficacy of IFN-beta-1a in MS patients. METHODS: We used primary bovine and porcine BCECs, as well as human and murine BCEC cell lines. We investigated the influence of human recombinant IFN-beta-1a on the paracellular permeability for 3H-inulin and 14C-sucrose across monolayers of bovine, human, and murine BCECs. In addition, the transendothelial electrical resistance (TEER) was determined in in vitro systems applying porcine and murine BCECS. RESULTS: We found a stabilizing effect on the barrier characteristics of BCECs after pretreatment with IFN-beta-1a in all applied in vitro models: addition of IFN-beta-1a resulted in a significant decrease of the paracellular permeability across monolayers of human, bovine, and murine BCECs. Furthermore, the TEER was significantly increased after pretreatment of porcine and murine BCECs with IFN-beta-1a. CONCLUSION: Our data suggest that BBB stabilization by IFN-beta-1a may contribute to its beneficial effects in the treatment of MS. A human in vitro BBB model might be useful as bioassay for testing the treatment efficacy of drugs in MS.

Thalamic stimulation for tremor. Subtle changes in episodic memory are related to stimulation per se and not to a microthalamotomy effect

The aim of this study was to investigate the impact of unilateral deep brain stimulation (DBS) of the ventrointermediate (Vim) thalamic nucleus on neuropsychological functioning comparing stimulation-on with stimulation-off conditions. Nine patients [five patients with Parkinson's Disease (PD), two patients with essential tremor (ET) and 2 patients with multiple sclerosis (MS)] underwent comprehensive neuropsychological testing for cognitive functions, including general mental impairment, aphasia, agnosia, executive and constructional abilities, learning, memory, cognitive processing speed and attention as well as depression. The neuropsychological assessments were performed at least 6 months postoperatively (mean 9 months). Testing in the stimulation-on and stimulation-off condition was obtained within a period of 3 to 4 weeks. Unilateral DBS resulted in improvement of tremor in all patients. There were no significant differences between the stimulation-on and the stimulation-off condition with the exception of a decrement of word-recall in the short delay free-recall subtest of the Rey Auditory-Verbal Learning Test (RAVLT). Subgroup analysis indicated that the impairment in word-recall was related to left-sided thalamic stimulation. Our study confirms that chronic unilateral DBS is a safe method with regard to cognitive function. The subtle changes in episodic memory are related to stimulation per se and not to a microthalamotomy effect.

Effect of discharge desynchronization on the size of motor evoked potentials: an analysis

OBJECTIVE: Motor evoked potentials (MEPs) after transcranial magnetic brain stimulation (TMS) are smaller than CMAPs after peripheral nerve stimulation, because desynchronization of the TMS-induced motor neurone discharges occurs (i.e. MEP desynchronization). This desynchronization effect can be eliminated by use of the triple stimulation technique (TST; Brain 121 (1998) 437). The objective of this paper is to study the effect of discharge desynchronization on MEPs by comparing the size of MEP and TST responses. METHODS: MEP and TST responses were obtained in 10 healthy subjects during isometric contractions of the abductor digiti minimi, during voluntary background contractions between 0% and 20% of maximal force, and using 3 different stimulus intensities. Additional data from other normals and from multiple sclerosis (MS) patients were obtained from previous studies. RESULTS: MEPs were smaller than TST responses in all subjects and under all stimulating conditions, confirming the marked influence of desynchronization on MEPs. There was a linear relation between the amplitudes of MEPs vs. TST responses, independent of the degree of voluntary contraction and stimulus intensity. The slope of the regression equation was 0.66 on average, indicating that desynchronization reduced the MEP amplitude on average by one third, with marked inter-individual variations. A similar average proportion was found in MS patients. CONCLUSIONS: The MEP size reduction induced by desynchronization is not influenced by the intensity of TMS and by the level of facilitatory voluntary background contractions. It is similar in healthy subjects and in MS patients, in whom increased desynchronization of central conduction was previously suggested to occur. Thus, the MEP size reduction observed may not parallel the actual amount of desynchronization.

Cathepsin G is differentially expressed in primary human antigen-presenting cells

Cathepsins are required for the processing of antigens in order to make them suitable for loading on major histocompatibility complex (MHC) class II molecules, for subsequent presentation to CD4(+) T cells. It was shown that antigen processing in monocyte-derived dendritic cells (DC), a commonly used DC model, is different from that of primary human DC. Here, we report that the two subsets of human myeloid DC (mDC) and plasmacytoid DC (pDC) differ in their cathepsin distribution. The serine protease cathepsin G (CatG) was detected in mDC1, mDC2, pDC, cortical thymic epithelial cells (cTEC) and high levels of CatG were determined in pDC. To address the role of CatG in the processing and presentation of a Multiple Sclerosis-associated autoantigen myelin basic protein (MBP), we used a non-CatG expressing fibroblast cell line and fibroblasts, which were preloaded with purified CatG. We find that preloading fibroblasts with CatG results in a decrease of MBP84-98-specific T cell proliferation, when compared to control cells. Our data suggest a different processing signature in primary human antigen-presenting cells and CatG may be of functional importance.