The mGlu(2/3) agonist 2R,4R-4-aminopyrrolidine-2,4-dicarboxylate, is anti- and proconvulsant in DBA/2 mice

The anticonvulsant activity of the selective group II metabotropic glutamate receptor (mGlu) agonist 2R,4R-4-aminopyrrolidine-2,4-dicarboxylate (2R,4R-APDC) has been evaluated in chemoconvulsant and sound-induced models of epileptic seizures in DBA/2 mice. 2R,4R-APDC (> or =10 nmol, intracerebroventricularly (i.c.v.), -15 min) transiently reduced sound-induced seizure activity including clonic seizures to 40% of vehicle at 20 nmol (i.c.v.) and 30% of vehicle at 100 mg/kg (intraperitoneally (i.p.), -15 min). 2R,4R-APDC inhibited clonic seizures induced by the group III mGlu antagonist (R,S)-alpha-methylserine-O-phosphate (2.5 micromol, i.c.v.) when co-injected at 20-40 nmol and inhibited limbic seizure activity induced by the mGlu(1/5) agonist (R,S)-3,5-dihydroxyphenylglycine (1.5 micromol, i.c.v.) when co-injected at 10-40 nmol. A reversal of the anticonvulsant activity of 2R,4R-APDC was observed at (>20 nmol) in each of the chemoconvulsant and sound-induced models of epileptic seizures. 2R,4R-APDC (0.1-1 micromol, i.c.v.) induced stimulus-independent, rapid and dose-dependent clonic seizures. Selective mGlu(2/3) agonists represent a novel class of potential anti-epileptic drugs, however due to the proconvulsant activity observed here, 2R,4R-APDC is obviously limited in this regard.

Beneficial immune activity after CNS injury: prospects for vaccination

A recent study in our laboratory showed, against all expectations, that macrophages and a particular type of T cell, by promoting regrowth and reducing the post-traumatic spread of damage in the injured rat optic nerve or spinal cord, have a beneficial effect on the injured CNS. Macrophages in the CNS have long been thought to have predominantly destructive effects. Autoimmunity in general, and in the CNS in particular, has never been documented as a purposeful physiological response of benign character. Our results suggest that after traumatic injury to the central nervous system (CNS), both of these immune cell types potentially have beneficial effects: macrophages can promote repair and T cells of a particular specificity can reduce the spread of damage. However, possibly because of the immune-privileged character of the CNS, the spontaneously evoked physiological activities of both macrophages and T cells in the CNS are restricted, and appear to need well-controlled boosting in order to be effective. It thus appears that (i) a stress signal transmitted from the traumatized tissue (in this case the CNS) for recruitment of the adaptive immune system does not have to be pathogen-related in order to evoke a response, (ii) a response to self is not necessarily a quirk of nature, and (iii) an autoimmune response, provided that it is well-regulated, helps the individual to cope with stress signals from the traumatized CNS, and thus plays a role in maintenance of the injured tissue without posing a threat to the organism.

Intra-CNS activation by antigen-specific T lymphocytes in experimental autoimmune encephalomyelitis

Identification and quantitation of autoreactive T lymphocytes is crucial in order to understand the pathogenesis of autoimmune diseases. We used flow cytometry to analyze autoantigen-specific T cellular responses in the well characterized rat experimental autoimmune encephalomyelitis (EAE) model. Cells isolated from both the central nervous system (CNS) tissue and peripheral lymph nodes were analyzed directly ex vivo or after short term in vitro culture with specific autoantigen. CNS infiltrating T lymphocytes displaying an interferon-gamma response to selected encephalitogenic myelin protein epitopes were measured kinetically during an individual disease episode and also between relapses in a chronic rat EAE model. One of the EAE models used displays a restriction towards TCRBV8S2 chain usage by the encephalitogenic T cells. In this model, in vitro production of intracellular interferon-gamma was selectively detected within this T cell subset derived from both the CNS and peripheral lymph nodes. Furthermore, antigen-specific cells infiltrating the CNS in this model produced several-fold higher amounts of interferon-gamma upon antigen stimulation and displayed a significantly increased in vivo proliferation compared with peripheral lymphocytes. These data thus directly demonstrates that T cells stimulated by a specific autoantigen in the periphery primarily acquire effector functions in the cellular environment of the target organ of the autoantigen.

Stem cell transplantation into the central nervous system and the control of differentiation

Recent advances in stem cell biology, including methods of cell amplification and control of differentiation in vitro, provide us with new and powerful tools with which to explore the cellular, molecular, and genetic factors affecting cell survival, proliferation, differentiation, and differentiation potential. Mitigating this vein of enthusiasm are the results of stem cell transplantation studies, which highlight our inability to control the fate of stem cell populations following transplantation to the central nervous system (CNS). Differentiation of transplanted cells is strongly influenced by the environmental signals and cellular deficiencies operating at the site of implantation, over which we can exert little or no control. Where stem cell transplantation-mediated repair of the injured CNS has been demonstrated most successfully, the transplant environments have invariably been simplistic, and transplantation into the complex and reactive environment of a CNS injury site generally results in migration from the site of implantation followed by glial cell differentiation. Together, these findings suggest that the most significant advances for the stem cell transplantation field will come from research strategies that include predifferentiation of stem cells prior to transplant and studies that further our understanding of the factors affecting stem cell differentiation in the complex environment of the CNS in vivo.

Gender differences and hormonal modulation in visceral pain

Women seek healthcare and are diagnosed more frequently with chronic somatic and visceral pain conditions relative to men. These conditions tend not to be life-threatening disorders, but rather ones that decrease people's quality of life, impinge on work and recreational activities, and increase healthcare resource utilization. With increased awareness of basic gender differences in biology and responsiveness to therapies, there has been renewed interest in factors which may account for the gender disparity in chronic visceral pain conditions. Basic and clinical evidence primarily from patients with irritable bowel syndrome has provided initial insights into visceral pain sensitivity, perception, and responsitivity.

Brain-gut interaction in irritable bowel syndrome: new findings of a multicomponent disease model

Knowledge on the pathophysiology of irritable bowel syndrome has evolved, beginning with disturbances in motility to visceral hypersensitivity, and ultimately to alterations in brain-gut bi-directional communication, where neurotransmitters such as serotonin play a key role. Recently, a multicomponent disease model that integrates all these alterations was proposed. This model is divided into physiological, cognitive, emotional and behavioral components that explain the gastrointestinal as well as the constitutional symptoms. In recent years there has been an explosion of research together with new developments in pharmacological treatments for IBS that support each component of this model. This review presents recent data in favor of these alterations in IBS.

Developmental mechanisms in the pathogenesis of neurodegenerative diseases

Cellular genes that are mutated in neurodegenerative diseases code for proteins that are expressed throughout neural development. Genetic analysis suggests that these genes are essential for a broad range of normal neurodevelopmental processes. The proteins they code for interact with numerous other cellular proteins that are components of signaling pathways involved in patterning of the neural tube and in regional specification of neuronal subtypes. Further, pathogenetic mutations of these genes can cause progressive, sublethal alterations in the cellular homeostasis of evolving regional neuronal subpopulations, culminating in late-onset cell death. Therefore, as a consequence of the disease mutations, targeted cell populations may retain molecular traces of abnormal interactions with disease-associated proteins by exhibiting changes in a spectrum of normal cellular functions and enhanced vulnerability to a host of environmental stressors. These observations suggest that the normal functions of these disease-associated proteins are to ensure the fidelity and integration of developmental events associated with the progressive elaboration of neuronal subtypes as well as the maintenance of mature neuronal populations during adult life. The ability to identify alterations within vulnerable neuronal precursors present in pre-symptomatic individuals prior to the onset of irrevocable cellular injury may help foster the development of effective therapeutic interventions using evolving pharmacologic, gene and stem cell technologies.

Enhancement of central nervous system pathology in early simian immunodeficiency virus infection by dopaminergic drugs

Human immunodeficiency virus infection (HIV) at late stages of the disease is accompanied by neurological complications, including motor, behavioral and cognitive impairment. Using simian immunodeficiency virus (SIV)-infected rhesus monkeys, an animal model of HIV infection, we found that during the asymptomatic SIV infection dopamine (DA) deficits are early components of central nervous system (CNS) dysfunction. To investigate the role of the DA system in SIV infection and to restore the DA deficiency, we administered selegiline, an agent with DAergic and neuroprotective properties, to SIV-infected monkeys. Selegiline increased DA availability but induced CNS vacuolization, SIV encephalitic lesions, and enhanced CNS viral replication during early SIV infection. The pathological changes seem to be mediated by DA, as treatment with L-DOPA, the precursor of DA, had similar effects. We propose that any natural or induced DAergic dysregulation which results in increased DA availability may potentiate HIV-associated neurological disease (ND). Our findings raise new questions regarding the pathogenesis of HIV-ND and generate concerns about the safety of dopaminergic drugs in the clinical management of HIV-infected patients.

Myelin proteolipid proteins promote the interaction of oligodendrocytes and axons

Although proteolipid protein (PLP) and its DM20 isoform are the major membrane proteins of CNS myelin, their absence causes surprisingly few developmental defects. In comparison, missense mutations of the X-linked Plp gene cause severe dysmyelination. Previous studies have established roles for PLP/DM20 in the formation of the intraperiod line and in maintaining axonal integrity. We now show that a normal number of oligodendrocytes are present in mice lacking PLP/DM20. However, in heterozygous females, which are natural chimeras for X-linked genes, oligodendrocytes lacking PLP/DM20 are in direct competition with wild-type oligodendrocytes that have a distinct advantage. PLP+ oligodendrocytes and PLP+ myelin sheaths make up the greater majority, and this feature is generalised in the CNS throughout life. Moreover, in the absence of PLP/DM20, a proportion of small-diameter axons fails to myelinate, remaining ensheathed but lacking a compact sheath, or show delayed myelination. These findings suggest that PLP/DM20 is also involved in the early stages of axon-oligodendrocyte interaction and wrapping of the axon.

Incomplete lupus erythematosus: results of a multicentre study under the supervision of the EULAR Standing Committee on International Clinical Studies Including Therapeutic Trials (ESCISIT)

OBJECTIVE

Patients characterized with antinuclear antibodies (ANA) and disease symptoms related to one organ system can be described as having incomplete systemic lupus erythematosus (SLE). The aim of this multicentre study was to describe the outcome of these so-called incomplete SLE patients. Two aspects of the outcome were studied: (i) the disease course, defined by the presence or absence of clinical symptoms; and (ii) the number of patients that eventually developed full SLE.

METHODS

Outcome parameters were the ACR criteria, the SLE disease Activity Index (SLEDAI), the European Consensus Lupus Activity Measure (ECLAM) and the requirement for treatment. In 10 European rheumatology centres, patients who had been evaluated in the last 3 months of 1994 and had been diagnosed as having incomplete SLE on clinical grounds for at least 1 yr were included in the study. All 122 patients who were included in the study were evaluated annually during 3 yr of follow-up.

RESULTS

Our results are confined to a patient cohort defined by disease duration of at least 1 yr, being under clinical care at the different centres in Europe. These patients showed disease activity that was related mostly to symptoms of the skin and the musculoskeletal system, and leucocytopenia. During the follow-up, low doses of prednisolone were still being prescribed in 43% of the patients. On recruitment to the study, 22 of the 122 incomplete SLE patients already fulfilled the ACR criteria for the diagnosis of SLE. In the 3 yr of follow-up only three patients developed SLE.

CONCLUSIONS

A high proportion of patients in our cohort defined on clinical grounds as having incomplete SLE eventually showed disease activity defined by the SLEDAI as well as ECLAM. However, only three cases developed to SLE during the follow-up. This suggests that incomplete SLE forms a subgroup of SLE that has a good prognosis.

Effects of alcohol and HIV infection on the central nervous system

Many people at risk for or infected with the human immunodeficiency virus (HIV) are heavy drinkers. Both HIV infection and heavy alcohol use adversely affect the immune system and central nervous system (CNS) function. However, little research has addressed the effects of heavy alcohol use on the severity and progression of HIV disease, including the development of HIV-associated CNS disease. Animal and in-vitro studies suggest that alcohol impairs various aspects of the immune system and increases the susceptibility to HIV infection, but may not accelerate progression of HIV disease. However, heavy alcohol use may interfere with the patient's adherence to antiretroviral treatment regimens. Neuropathological and neuropsychological studies have indicated that certain brain areas are affected by both HIV-infection and chronic alcohol abuse. Magnetic resonance spectroscopy studies of both HIV-positive and HIV-negative people who were either heavy or light drinkers found that chronic alcohol abuse exacerbates some metabolic injury in the brains of HIV-infected people, although this effect may be less pronounced in patients receiving effective antiretroviral therapy.

Morphine tolerance and dependence in nociceptin/orphanin FQ transgenic knock-out mice

It has been hypothesized that morphine tolerance and dependence in mice following chronic exposure may reflect increased compensatory activity of antiopioid systems. The endogenous peptide nociceptin/orphanin FQ has been shown to have anti-opioid effects, for example antagonizing morphine analgesia. Moreover, chronic morphine administration increases synthesis of the peptide, and morphine tolerance and dependence can be attenuated or reversed by antagonists and agonists of the nociceptin/orphanin FQ receptor, respectively. The present study seeks to confirm a role for nociceptin/orphanin FQ in opioid tolerance and dependence by comparing morphine ED(50) values and naloxone-precipitated withdrawal jumping in mice homozygous (knock-out) and heterozygous for a null mutation of the Npnc1 gene encoding the nociceptin/orphanin FQ propeptide, and their wild type littermates, following chronic morphine exposure. Relative to morphine-naive control mice, significant rightward shifts in the morphine dose-response curve, resulting in increased morphine ED(50) values (approximately two to three-fold), was observed for all genotypes following three days of repeated systemic morphine injections. However, no differences between genotypes in the magnitude of tolerance were observed. In contrast, knock-out mice displayed significantly increased naloxone-precipitated withdrawal jumping relative to heterozygous and wild-type mice following implantation with a morphine pellet (25mg) for 72h. Use of nociception/orphaninFQ transgenic knock-out mice thus demonstrate the differential involvement of nociceptin/orphanin FQ in morphine tolerance and dependence.

[Neural networks and pain processing. New insights from imaging techniques]

Imaging techniques with high spatial and temporal resolution (PET,fMRI, MEG) provide detailed information about the brains' processing of pain. Structures detected by these techniques are not understood as pain centers but as nodal points of a dynamic network which is influenced by physiological and psychological input. Imaging techniques can be used for the investigation of different pain components. The neuronal network that encodes sensory-discriminative information consists of the primary and secondary somatosensory cortex which receive input from lateral thalamic nuclei. Information for the affective pain component reach the anterior cingulate cortex, insula and prefrontal cortex via medial thalamic nuclei. Until now only little is known about cortical structures mediating the cognitive pain component. In chronic pain the cortical and subcortical processing of nociceptive input is presumably modified. Reorganization in the primary somatosensory cortex is presented as an example of neuronal plasticity induced by chronic pain.

The effect of gamma-linolenic acid-alpha-lipoic acid on functional deficits in the peripheral and central nervous system of streptozotocin-diabetic rats

Diabetes mellitus can lead to functional and structural deficits in both the peripheral and central nervous system. The pathogenesis of these deficits is multifactorial, probably involving, among others, microvascular dysfunction and oxidative stress. The present study examined the effects of 12 weeks of treatment with a conjugate of the essential fatty acid gamma-linolenic acid and the anti-oxidant alpha-lipoic acid (GLA-LA) on functional deficits in the peripheral and central nervous system in streptozotocin-diabetic rats. Treatment was initiated 16 weeks after diabetes induction. Sciatic nerve motor and sensory conduction velocity, brainstem auditory evoked potentials and visual evoked potentials were measured in control, untreated and GLA-LA treated diabetic rats. Also, long-term potentiation, a form of synaptic plasticity used as a model for learning and memory at the cellular level, was examined in hippocampal slices. GLA-LA treatment (50 mg/kg/day) did not reverse established deficits in nerve conduction velocity or in evoked potential latencies in diabetic rats. However, GLA-LA treatment did improve long-term potentiation in the hippocampus. It is concluded that GLA-LA, which is known to improve early deficits in peripheral nerve conduction in diabetic rats, is unable to reverse late deficits. However, the compound does reverse established deficits in long-term potentiation, suggesting that at least part of its activity is specifically directed at synaptic plasticity.

Comparative lipid binding study on the cerebroside sulfate activator (saposin B)

Cerebroside sulfate activator (saposin B) is a small protein involved in glycosphingolipid metabolism. It binds certain membrane lipids, making them available to water-soluble enzymes. Defects in this protein are responsible for a form of metachromatic leukodystropy, a progressive neurodegenerative condition. The protein participates in the catabolism of a number of lipids but does show lipid binding selectivity. However, the basis of this selectivity is unclear. Here we assess the relative binding of a number of lipids compared to cerebroside sulfate (sulfatide). We utilize a competitive binding paradigm, in which the lipids compete for protein under favorable conditions and are then switched to a condition in which the complex is stable. This study is unique in that a single molecular species of the activator is employed, and an expanded selection of natural and semisynthetic membrane lipids is surveyed. No simple "binding rule" can be ascertained from these data, but ligands with longer and/or more complex lipoidal and polar adducts appear to be favored.

Autosomal recessive spastic paraplegia with hypoplastic corpus callosum, multisystem degeneration and ubiquitinated eosinophilic granules

We report a 48-year-old woman with familial spastic paraplegia (FSP) showing mental retardation, amyotrophy and sensory disturbance. Her parents were second cousins and there were two other affected siblings in the family. Autopsy revealed degenerative lesions characterized by neuronal loss and gliosis in the upper and lower motor neuron systems, thalamus, lateral geniculate body, dentate nucleus and posterior column of the spinal cord. The remaining neurons often contained ubiquitinated lipofuscin granules. Although the corpus callosum was severely attenuated, it exhibited well-preserved myelination and only minimal gliosis. In the substantia nigra, the number of pigmented neurons was apparently low, but there was slight gliosis and no extraneuronal free melanin pigment in the background. The neurons in this brain region contained much smaller amounts of melanin pigment than might be expected for the patient's age. These findings suggest that this is an example of a family with autosomal recessive FSP with thin corpus callosum, and that maldevelopment of the corpus callosum and substantia nigra is a characteristic feature of the disease.

Chemokines and viral diseases of the central nervous system

This chapter discusses chemokines and their receptors in the evolution of viral infectious diseases of the central nervous system (CNS). Infection of the human CNS with many different viruses or infection of the rodent CNS induces vigorous host-inflammatory responses with recruitment of large numbers of leukocytes, particularly T lymphocytes and macrophages. Chemokines coordinate trafficking of peripheral blood leukocytes by stimulating their chemotaxis, adhesion, extravasation, and other effector functions. In view of these properties, research efforts have turned increasingly to the possible involvement of chemokines in regulating both peripheral tissue and CNS leukocyte migration during viral infection. The biological effects of chemokines are mediated via their interaction with receptors belonging to the family of seven transmembrane (7TM)-spanning, G-protein coupled receptors (GPCRs). In the normal mammalian CNS, the number of leukocytes present in the brain is scant. However, these cells are attracted to, and accumulate in, a variety of pathologic states, many involving viral infection. Although leukocyte migration into local tissue compartments, such as the CNS, is a multifactorial process, it has become clear that chemokines are pivotal components of this process, providing a necessary chemotactic signal for leukocyte recruitment.

Acute effects on the human EEG after an external exposure to 200 ppm methanol

OBJECTIVES

Even low concentrations of organic solvents may cause acute effects on the human central nervous system. The German MAK (threshold limit value) of methanol is 200 ppm. The aim of this study was to investigate whether acute exposure to 200 ppm methanol causes adverse effects, measured by EEG, and moreover, whether it is possible to differentiate between sedative and excitatory effects with this method.

METHODS

Twelve healthy subjects were exposed for 4 h to 200 ppm and to 20 ppm (control) in an exposure chamber in a cross-over design. The EEG was recorded before (reference) and at the end of each exposure with, the subject's eyes closed and opened and during a choice reaction test (color word stress test). Spectral power was calculated by fast Fourier transformation. Subjective symptoms and effects of blinding with 20 ppm methanol were assessed by questionnaires.

RESULTS

The study was a single-blind one. During subjects' exposure to 200 ppm, their scores for prenarcotic and irritating symptoms were not different from controls. In the closed-eye condition of subjects, the spectral power of the theta-band and of some electrodes of the delta-band was significantly less at the end of exposure to 200 ppm, than that of controls. In the open-eye condition and during the color word stress test no significant changes were found.

CONCLUSION

The changes in the theta-band suggest a slight excitatory effect of 200 ppm methanol. The effect was weak, as scores of acute symptoms did not change. With respect to our results, it is not necessary for the MAK value to be decreased.

Acute hypoglycemia impairs the functioning of the central but not peripheral nervous system

Acute hypoglycemia impairs functions of the central nervous system, but few controlled studies have assessed the impact of hypoglycemia on the function of the peripheral nervous system. Sixteen non-diabetic humans underwent two separate hyperinsulinemic glucose clamp procedures on different study days, in a counter-balanced fashion. On one occasion, euglycemia was maintained (blood glucose, 5.0 mmol l(-1)), and on the other occasion, hypoglycemia (blood glucose, 2.6 mmol l(-1)) was induced. During each condition, subjects performed a combined psychometric, cognitive-experimental and psychophysical test battery, and measures were made (in the dominant median and common peroneal nerves) of the motor nerve conduction velocities and the amplitudes of the motor action potentials. Hypoglycemia caused impaired performance of general cognitive and information processing tasks (P<.05), but nerve conduction velocities and the amplitudes of motor action potentials were unaffected. Conduction velocities of the common peroneal nerve decreased from baseline within each experimental condition, perhaps due to hyperinsulinemia. Overall, these results demonstrate that multiple levels of information processing in the brain may alter while peripheral nerve function remains intact, and imply that peripheral neurons do not have the same obligate requirement for glucose as a metabolic fuel as neurons of the central nervous system.

Cytomegalovirus ventriculoencephalitis presenting as a Wernicke's encephalopathy-like syndrome

Cytomegalovirus ventriculoencephalitis (CMV-VE) is a devastating opportunistic infection seen most frequently in patients with AIDS. The authors describe eight patients with AIDS and CMV-VE, who developed the clinical features of the Wernicke-Korsakoff syndrome, including impaired memory, confabulation, nystagmus, ophthalmoplegia, and ataxia. CMV-VE is perhaps a more frequent cause of the Wernicke-Korsakoff syndrome than traditional associations.

Pure autonomic failure in association with human alpha-synucleinopathy

We studied an autopsy case with pure autonomic failure, using anti-alpha-synuclein antibody. Until now there has been no report about the immunohistochemical properties of alpha-synuclein in pure autonomic failure. In conventional stainings, both pre- and post-ganglionic lesions of the sympathetic and parasympathetic nervous systems were found. Lewy bodies and Lewy neurites were abundant especially in the sympathetic nervous system. These inclusions were immunoreactive to anti-alpha-synuclein antibody. The intensity of alpha-synuclein immunoreactivity was stronger in the halos than in the cores of the Lewy bodies. The edges of the swollen neurites had strong immunoreactivity. The substantia nigra was well preserved, and no cortical Lewy bodies were seen. These findings indicate that pure autonomic failure is one of the Lewy body type alpha-synucleinopathies, such as Parkinson's disease and dementia with Lewy bodies, targeting the peripheral autonomic nervous system.