Epilepsy, hyperalgesia, impaired memory, and loss of pre- and postsynaptic GABA(B) responses in mice lacking GABA(B(1))

GABA(B) (gamma-aminobutyric acid type B) receptors are important for keeping neuronal excitability under control. Cloned GABA(B) receptors do not show the expected pharmacological diversity of native receptors and it is unknown whether they contribute to pre- as well as postsynaptic functions. Here, we demonstrate that Balb/c mice lacking the GABA(B(1)) subunit are viable, exhibit spontaneous seizures, hyperalgesia, hyperlocomotor activity, and memory impairment. Upon GABA(B) agonist application, null mutant mice show neither the typical muscle relaxation, hypothermia, or delta EEG waves. These behavioral findings are paralleled by a loss of all biochemical and electrophysiological GABA(B) responses in null mutant mice. This demonstrates that GABA(B(1)) is an essential component of pre- and postsynaptic GABA(B) receptors and casts doubt on the existence of proposed receptor subtypes.

VR1 protein expression increases in undamaged DRG neurons after partial nerve injury

Changes in phenotype or connectivity of primary afferent neurons following peripheral nerve injury may contribute to the hyperalgesia and allodynia associated with neuropathic pain conditions. Although earlier studies using partial nerve injury models have focused on the role of damaged fibres in the generation of ectopic discharges and pain, it is now thought that remaining undamaged fibres may be equally important. We have examined the expression of the sensory neuron-specific cation channel Vanilloid Receptor 1 (VR1), an important transducer of noxious stimuli, in three models of nerve injury in the rat, using anatomical separation or fluorescent retrograde tracers to identify damaged or undamaged sensory neurons. After total or partial sciatic nerve transection, or spinal nerve ligation, VR1-immunoreactivity (IR) was significantly reduced in the somata of all damaged dorsal root ganglion (DRG) neuronal profiles, compared to controls. However, after partial transection or spinal nerve ligation, VR1 expression was greater in the undamaged DRG somata than in controls. Unexpectedly, after L5 spinal nerve ligation, VR1-IR of the A-fibre somata increased approximately 3-fold in the uninjured L4 DRG compared to controls; a much greater increase than seen in the somata with C-fibres. Furthermore, we found that VR1-IR persisted in the transected sciatic nerve proximal to the lesion, despite its down-regulation in the damaged neuronal somata. This persistence in the nerve proximal to the lesion after nerve section, together with increased VR1 in DRG neurons left undamaged after partial nerve injury, may be crucial to the development or maintenance of neuropathic pain.

The role of central and peripheral Cannabinoid1 receptors in the antihyperalgesic activity of cannabinoids in a model of neuropathic pain

We have examined the effects of cannabinoid agonists on hyperalgesia in a model of neuropathic pain in the rat and investigated the possible sites of action. The antihyperalgesic activity of the cannabinoids was compared with their ability to elicit behavioural effects characteristic of central cannabinoid activity. WIN55,212-2 (0.3-10 mg kg(-1)), CP-55,940 (0.03-1 mg kg(-1)) and HU-210 (0.001-0.03 mg kg(-1)) were all active in a 'tetrad' of tests consisting of tail-flick, catalepsy, rotarod and hypothermia following subcutaneous administration, with a rank order of potency in each of HU-210 > CP-55,940 > WIN55,212-2. The effects of WIN55,212-2 in each assay were blocked by the Cannabinoid1 (CB1) antagonist SR141716A. In the partial sciatic ligation model of neuropathic pain WIN55,212-2, CP-55,940 and HU-210 produced complete reversal of mechanical hyperalgesia within 3 h of subcutaneous administration with D50 values of 0.52, 0.08 and 0.005 mg kg(-1), respectively. In this model WIN55,212-2 was also effective against thermal hyperalgesia and mechanical allodynia. WIN55,212-2 produced pronounced reversal of mechanical hyperalgesia following intrathecal administration that was blocked by the CB1 antagonist SR141716A. Following intraplantar administration into the ipsilateral hindpaw, WIN55,212-2 produced up to 70% reversal of mechanical hyperalgesia, although activity was also observed at high doses following injection into the contralateral paw. The antihyperalgesic effect of WIN55,212-2 injected into the ipsilateral paw was blocked by subcutaneously administered SR141716A, but was not affected by intrathecally administered SR141716A. These data show that cannabinoids are highly potent and efficacious antihyperalgesic agents in a model of neuropathic pain. This activity is likely to be mediated via an action in both the CNS and in the periphery.

Intrathecally administered endotoxin or cytokines produce allodynia, hyperalgesia and changes in spinal cord neuronal responses to nociceptive stimuli in the rat

Inflammatory processes occurring within the central nervous system (CNS) can produce 'illness induced behaviours' which include fever, sleep and the development of allodynia and hyperalgesia. Here we demonstrate the effects of the pro-inflammatory mediators, bacterial endotoxin, and rat recombinant interleukin 1 beta (rrIL-1 beta) or tumour necrosis factor-alpha (rrTNF alpha) on the integration of somatosensory information at the single neuronal level, via recordings from wide-dynamic range neurones in the dorsal horn of the spinal cord in anaesthetized rats. Intrathecal administration of E. coli lipopolysaccharide (LPS, 10 and 100 microg, i.t.) enhanced the activity of dorsal horn neurones, including facilitation of neuronal post-discharge. Intrathecal administration of IL-1 beta (5-5000 pg) or TNF-alpha (5-5000 pg) enhanced dorsal horn neuronal responses, including the acute responses to C-fibre stimulation, wind-up and post-discharge, however, the effects of IL-1 beta were more robust than those of TNF alpha. Intrathecal administration of IL-1 beta (1-1000 pg) also leads to the development of mechanical allodynia and hyperalgesia. On the other hand intrathecal application of TNF alpha did not produce changes in sensitivity to mechanical stimuli. Changes in the activity of spinal wide-dynamic range neurones induced by local inflammation may provide a pathomechanism for the clinical pathology of central pain syndrome, which can accompany CNS disease or acute CNS injury.

A new definition of Alzheimer's disease: a hippocampal dementia

Preliminary data support the hypothesis that the decline of all higher cognitive functions in senile dementia of the Alzheimer type is attributable to histopathological changes in the hippocampal formation, with or without neocortical neuronal lesions. Previous literature amply supports the critical role of this "locus minoris resistentiae" in memory processing and cognitive physiology. New observations include quantitative morphometric evaluations of the hippocampal formation from a longitudinal study of prospectively tested patients and histological and neurochemical data from patients with a clinical presentation consistent with typical Alzheimer's disease, in whom the only neuropathological abnormality was devastating nerve cell loss and gliosis in the hippocampi.

Combined endovascular embolization and surgery in the management of cerebral arteriovenous malformations: experience with 101 cases

The authors describe their experience with 101 cerebral arteriovenous malformations (AVM's) treated by endovascular embolization followed by surgical removal. Fifty-three patients presented with intracranial hemorrhage and 35 had seizures. Based on the classification of Spetzler and Martin, two AVM's were Grade I, 13 were Grade II, 26 were Grade III, 43 were Grade IV, and 17 were Grade V. Fifty-six AVM's were in the right hemisphere, 28 were in the left hemisphere, 12 were in the corpus callosum, and five involved the cerebellum. In 50 cases, presurgical obliteration of 50% to 75% of the AVM nidus was achieved by embolization, and in 31 cases this percentage increased to between 75% and 90%. In 97 (96%) patients, complete surgical removal of the AVM was obtained. Morbidity resulting from preoperative endovascular embolization was classified as mild in 3.9% of the cases, moderate in 6.9%, and severe in 1.98%. The death rate related to embolization was 0.9%. The immediate postsurgical morbidity was classified as mild in 5.9% of the cases, moderate in 10.8%, and severe in 5.9%. The overall long-term morbidity was mild in 5.9% of the cases, moderate in 6.9%, and severe in 1.98%. Two patients (1.98%) died due to intractable intraoperative hemorrhage and two (1.98%) as a result of postsurgical pulmonary complications.

Treatment of 54 traumatic carotid-cavernous fistulas

A series of 54 traumatic carotid-cavernous fistulas has been treated with detachable balloon catheters. The balloon was introduced through one of three different approaches: the endarterial route; the venous route through the jugular vein, the inferior petrosal sinus, and the cavernous sinus; or surgical exposure of the cavernous sinus; with occlusion of the fistula by a detachable balloon directly positioned in the cavernous sinus. Full follow-up review demonstrated that the carotid blood flow was preserved in 59% of cases. The most frequent complication was a transient oculomotor nerve palsy, which occurred in 20% of cases. In three cases where both the fistula and the carotid artery were originally occluded by the balloon, the superior portion of the fistula was later found not to be completely occluded, and these patients had intracranial ligation of the supraclinoid portion of the carotid artery. Three patients had hemiparesis, transient in two cases and permanent in the other. The results show that the fistula was totally occluded in 53 cases; in the one exception the patient became asymptomatic but had a minimal angiographic leak.

Peripheral nerve injury induces cannabinoid receptor 2 protein expression in rat sensory neurons

We have localized cannabinoid receptor 2 protein in rat and mouse somatic sensory nervous system, using an antibody that recognizes mouse cannabinoid receptor 2. Little or no cannabinoid receptor 2 immunoreactivity was found in sections of naive rat or mouse dorsal root ganglia or spinal cord. This was in accord with the lack of detectable cannabinoid receptor 2 mRNA in (dorsal root ganglion) neurons by in situ hybridization experiments described in the literature. However, we could detect cannabinoid receptor 2 immunoreactivity following unilateral nerve damage-either by sciatic nerve section, or by spinal nerve ligation. It was localized to the superficial laminae of the dorsal horn of the spinal cord, ipsilateral to the nerve damage, coincident with the area of termination of damaged afferents which was marked by loss of isolectin B4 binding. This upregulation was not seen in cannabinoid receptor 2 null mice. The cannabinoid receptor 2 protein in spinal cord appeared to be expressed on sensory neuron afferent terminals as it colocalized with two markers of damaged afferents, namely growth associated protein-43 and the neuropeptide galanin. Moreover, it did not colocalize with markers of activated microglial cells (OX-42) or astroglial cells (glial fibrillary acidic protein) in rat spinal cord. In the peripheral nerve, accumulation of cannabinoid receptor 2 immunoreactivity was seen in nerve sections proximal, but not distal, to the ligation site, suggesting transport down the nerve from the cell bodies. Although convincing cannabinoid receptor 2 immunoreactivity was seen in neither uninjured nor injured dorsal root ganglion neuron cell bodies in tissue sections, expression was detectable in isolated, cultured neurons that had received a prior axotomy in vivo. This clear demonstration of CB(2) receptors on sensory neurons suggests an additional cellular target for CB(2) agonist induced analgesia, at least in neuropathic models.

Serogroup W135 meningococcal disease in Hajj pilgrims

An outbreak of W135 meningococcal disease occurred in the spring of 2000 among pilgrims returning from Saudi Arabia and their contacts. Clinical isolates from England and France were examined and compared with reference strains from other countries. Characterisation of isolates by a range of typing methods showed them to be of clonal origin (ET-37) and closely related to other meningococci with an established propensity to cause disease clusters. A reappraisal of vaccination strategies for travellers is required.

Meningococcal serogroup C conjugate vaccine is immunogenic in infancy and primes for memory

The safety, immunogenicity, and immunologic priming of 2 dosages (2 microgram or 10 microgram) of a meningococcal C oligosaccharide-CRM197 conjugate vaccine was evaluated in 114 infants vaccinated at ages 2, 3, and 4 months. Antibody persistence and response to boosting with 10 microgram of meningococcal C polysaccharide were assessed. The meningococcal conjugate vaccine produced fewer local reactions than concurrent routine immunizations. Total serogroup C-specific immunoglobulin geometric mean concentration (GMC) increased from 0.3 microgram/mL before vaccination to 13.1 microgram/mL at age 5 months. Serum bactericidal antibody (SBA) geometric mean titers (GMTs) rose from <1:4 to 1:1057 at 5 months and fell by 14 months to 1:19. Following boosting, anti-C-specific immunoglobulin GMC rose to 15.9 microgram/mL and SBA GMT to 1:495. Antibody responses in the 10-microgram dose cohort were significantly higher at 5 months (P<.01) than in the 2-microgram dose cohort but were lower after polysaccharide boosting (P=.02). This meningococcal conjugate vaccine was well tolerated and immunogenic and induced immunologic memory in infants.

Capsule phase variation in Neisseria meningitidis serogroup B by slipped-strand mispairing in the polysialyltransferase gene (siaD): correlation with bacterial invasion and the outbreak of meningococcal disease

A mechanism of capsular polysaccharide phase variation in Neisseria meningitidis is described. Meningococcal cells of an encapsulated serogroup B strain were used in invasion assays. Only unencapsulated variants were found to enter epithelial cells. Analysis of one group of capsule-deficient variants indicated that the capsular polysaccharide was re-expressed at a frequency of 10(-3). Measurement of enzymatic activities involved in the biosynthesis of the alpha-2,8 polysialic acid capsule showed that polysialyltransferase (PST) activity was absent in these capsule-negative variants. Nucleotide sequence analysis of siaD revealed an insertion or a deletion of one cytidine residue within a run of (dC)7 residues at position 89, resulting in a frameshift and premature termination of translation. We analysed unencapsulated isolates from carriers and encapsulated case isolates collected during an outbreak of meningococcal disease. Further paired blood-culture isolates and unencapsulated nasopharyngeal isolates from patients with meningococcal meningitis were examined. In all unencapsulated strains analysed we found an insertion or deletion within the oligo-(dC) stretch within siaD, resulting in a frameshift and loss of capsule formation. All encapsulated isolates, however, had seven dC residues at this position, indicating a correlation between capsule phase variation and bacterial invasion and the outbreak of meningococcal disease.

Embolization of cerebral arteriovenous malformations with bucrylate

Forty-six patients with cerebral arteriovenous malformations (AVM's) were selected for embolization with bucrylate. These patients were assigned to three different groups. Group I consisted of 22 patients with nonresectable AVM's who were selected for embolization with a Silastic calibrated-leak ballon. In 16 or these patients, embolization was achieved, with partial obliteration of the AVM in 14 and complete obliteration in two. Five patients had subarachnoid hemorrhage caused by the balloon bursting and concomitant dissection of the feeding vessel. Four of these patients recovered completely and one died of a brain-stem hemorrhage. A permanent field defect was noted in five cases, and two patients had a transient mild neurological deficit. Group II consisted of 13 patients treated by intraoperative embolization. Complete obliteration by embolization was obtained in four cases, and complete surgical resection after embolization in five. Partial embolization with no surgical resection was achieved in five cases. Three of these patients had a permanent mild neurological deficit and two had transient deficits. There was no mortality in this group. Group III consisted of 11 patients treated by embolization with bucrylate using a new latex calibrated-leak balloon. This balloon has a higher malleability, and takes on the exact configuration of the feeder, with no risk of dissection. This balloon also permits delivery of the faster and larger injection of bucrylate to the arterial feeders of the AVM. Two AVM's were completely obliterated, and embolization was only partially successful in the other cases. Neurological complications consisted of incomplete field defects in two cases, slight memory loss in one case, and transient clumsiness of the arm and face in one case. Two patients have a catheter permanently glued in the malformation, with no neurological complication. There was no mortality in this group.

Vascular risk factors and leuko-araiosis

Leuko-araiosis was found in 49 of 140 demented patients compared with 12 out of 110 control subjects. Thirty-one of 95 patients with dementia of the Alzheimer's type had leuko-araiosis. A history of stroke was four times more frequent in patients with leuko-araiosis than in those without leuko-araiosis (17.4% and 4.4%, respectively). It occurred in 25% of controls with leuko-araiosis compared with only 2% of those without leuko-araiosis. Mean systolic blood pressure was associated with leuko-araiosis. No association was found for diastolic blood pressure, myocardial infarction, angina, diabetes, or carotid bruits. On logistic regression analysis, the strong association between dementia and leuko-araiosis was mainly explained by a history of stroke. There are common factors in leuko-araiosis and stroke, but stroke alone does not account for leuko-araiosis.

Differential impairments of selective attention due to frequency and duration of cannabis use

The evidence for long-term cognitive impairments associated with chronic use of cannabis has been inconclusive. We report the results of a brain event-related potential (ERP) study of selective attention in long-term cannabis users in the unintoxicated state. Two ERP measures known to reflect distinct components of attention were found to be affected differentially by duration and frequency of cannabis use. The ability to focus attention and filter out irrelevant information, measured by frontal processing negativity to irrelevant stimuli, was impaired progressively with the number of years of use but was unrelated to frequency of use. The speed of information processing, measured by the latency of parietal P300, was delayed significantly with increasing frequency of use but was unaffected by duration of use. The results suggest that a chronic buildup of cannabinoids produces both short- and long-term cognitive impairments.

Quality of patient health information on the Internet: reviewing a complex and evolving landscape

BACKGROUND

The popularity of the Internet has enabled unprecedented access to health information. As a largely unregulated source, there is potential for inconsistency in the quality of information that reaches the patient.

AIMS

To review the literature relating to the quality indicators of health information for patients on the Internet.

METHOD

A search of English language literature was conducted using PubMed, Google Scholar and EMBASE databases.

RESULTS

Many articles have been published which assess the quality of information relating to specific medical conditions. Indicators of quality have been defined in an attempt to predict higher quality health information on the Internet. Quality evaluation tools are scoring systems based on indicators of quality. Established tools such as the HONcode may help patients navigate to more reliable information. Google and Wikipedia are important emerging sources of patient health information.

CONCLUSION

The Internet is crucial for modern dissemination of health information, but it is clear that quality varies significantly between sources. Quality indicators for web-information have been developed but there is no agreed standard yet. We envisage that reliable rating tools, effective search engine ranking and progress in crowd-edited websites will enhance patient access to health information on the Internet.

Immunogenicity and reactogenicity in UK infants of a novel meningococcal vesicle vaccine containing multiple class 1 (PorA) outer membrane proteins

The development of effective vaccines against serogroup B meningococci is of great public health importance. We assessed a novel genetically engineered vaccine containing six meningococcal class 1 (PorA) outer membrane proteins representing 80% of prevalent strains in the UK. 103 infants were given the meningococcal vaccine at ages 2, 3 and 4 months with routine infant immunisations, with a fourth dose at 12-18 months. The vaccine was well tolerated. Three doses evoked good immune responses to two of six meningococcal strains expressing PorA proteins contained in the vaccine. Following a fourth dose, larger bactericidal responses to all six strains were observed, suggesting that the initial course had primed memory lymphocytes and revaccination stimulated a booster response. This hexavalent PorA meningococcal vaccine was safe and evoked encouraging immune responses in infants. Vaccines of this type warrant further development and evaluation.

Meta-Analysis of Neuropsychological Symptoms of Adolescents and Adults with PKU

Phenylketonuria (PKU; OMIM 261600) is an autosomal recessive inborn error of phenylanaline metabolism. PKU is characterized by deficient or defective phenylalanine hydroxylase activity and persistantly increased levels of the essential amino acid phenylalanine in the circulation. The present article examines current understanding of the etiology of PKU, along with a meta-analysis examining neuropsychological and intellectual presentations in continuously treated adolescents and adults. Patients with PKU differed significantly from controls on Full-Scale IQ, processing speed, attention, inhibition, and motor control. Future research utilizing an integrative approach and detailed analysis of specific cognitive domains will assist both the scientist and clinician, and ultimately the patient.

Exercise alters mouse sperm small noncoding RNAs and induces a transgenerational modification of male offspring conditioned fear and anxiety

There is growing evidence that the preconceptual lifestyle and other environmental exposures of a father can significantly alter the physiological and behavioral phenotypes of their children. We and others have shown that paternal preconception stress, regardless of whether the stress was experienced during early-life or adulthood, results in offspring with altered anxiety and depression-related behaviors, attributed to hypothalamic-pituitary-adrenal axis dysregulation. The transgenerational response to paternal preconceptual stress is believed to be mediated by sperm-borne small noncoding RNAs, specifically microRNAs. As physical activity confers physical and mental health benefits for the individual, we used a model of voluntary wheel-running and investigated the transgenerational response to paternal exercise. We found that male offspring of runners had suppressed reinstatement of juvenile fear memory, and reduced anxiety in the light-dark apparatus during adulthood. No changes in these affective behaviors were observed in female offspring. We were surprised to find that running had a limited impact on sperm-borne microRNAs. The levels of three unique microRNAs (miR-19b, miR-455 and miR-133a) were found to be altered in the sperm of runners. In addition, we discovered that the levels of two species of tRNA-derived RNAs (tDRs)-tRNA-Gly and tRNA-Pro-were also altered by running. Taken together, we believe this is the first evidence that paternal exercise is associated with an anxiolytic behavioral phenotype of male offspring and altered levels of small noncoding RNAs in sperm. These small noncoding RNAs are known to have an impact on post-transcriptional gene regulation and can thus change the developmental trajectory of offspring brains and associated affective behaviors.

Arthropathic properties related to the molecular weight of peptidoglycan-polysaccharide polymers of streptococcal cell walls

The covalently bound polymers of peptidoglycan and group-specific polysaccharide (PG-APS) were isolated from the cell walls of group A streptococci. Arthritis was induced in rats with a single intraperitoneal injection of an aqueous suspension of PG-APS fragments derived by sonication. The joint lesions induced with this polydisperse suspension followed a bimodal pattern consisting of an acute phase, which reached a peak 5 days after injection and then receded, followed by a chronic, remittent, erosive arthritis lasting several months. The relative severities of the acute and chronic phases could be manipulated by selection of the size of PG-APS fragments. The fragments of PG-APS obtained by sonic treatment were resolved on the basis of size into three major populations by sucrose gradient or differential centrifugation. Based upon light scattering and gel filtration, the average molecular weight of the largest family of fragments was estimated to be about 500 x 10(6), the intermediate fragments were 50 x 10(6) daltons, and the predominant size in the smallest population was 5.3 x 10(6) daltons. The larger fragments induced negligible acute inflammation, but chronic disease became apparent 5 to 9 weeks after injection. The smallest fragments induced the most severe acute inflammation, with relatively little late, chronic joint disease. The particles of intermediate size induced moderate acute inflammation and the most severe chronic, erosive joint lesions. A single injection of fragments of the isolated peptidoglycan moiety of the PG-APS induced only a moderate acute inflammation of joints, with no apparent capacity to maintain the injury and induce chronic disease.

Next Generation Sequencing for Detection and Discovery of Plant Viruses and Viroids: Comparison of Two Approaches

Next generation sequencing (NGS) technologies are becoming routinely employed in different fields of virus research. Different sequencing platforms and sample preparation approaches, in the laboratories worldwide, contributed to a revolution in detection and discovery of plant viruses and viroids. In this work, we are presenting the comparison of two RNA sequence inputs (small RNAs vs. ribosomal RNA depleted total RNA) for the detection of plant viruses by Illumina sequencing. This comparison includes several viruses, which differ in genome organization and viroids from both known families. The results demonstrate the ability for detection and identification of a wide array of known plant viruses/viroids in the tested samples by both approaches. In general, yield of viral sequences was dependent on viral genome organization and the amount of viral reads in the data. A putative novel Cytorhabdovirus, discovered in this study, was only detected by analysing the data generated from ribosomal RNA depleted total RNA and not from the small RNA dataset, due to the low number of short reads in the latter. On the other hand, for the viruses/viroids under study, the results showed higher yields of viral sequences in small RNA pool for viroids and viruses with no RNA replicative intermediates (single stranded DNA viruses).

Innate and adaptive immune responses to nonvascular xenografts: evidence that macrophages are direct effectors of xenograft rejection

Nonvascularized xenograft rejection is T cell mediated, but is dependent on initial macrophage (Mphi) infiltration. We developed an i.p. transplant model to define the roles of Mphi and T cells in xenograft rejection. Nonobese diabetic or BALB/c mice were injected i.p. with xenogeneic, allogeneic, or syngeneic cells, and the responding cells in subsequent lavages were assessed by flow cytometry and adoptive transfer. Neutrophils and monocytes/elicited Mphi were rapidly recruited in response to xenogeneic pig (PK15 or spleen) cells and, to a significantly lesser extent, allogeneic cells. These innate responses preceded T cell infiltration and occurred in their absence in SCID mice. Syngeneic cells induced negligible neutrophil or Mphi responses. Neutrophils and Mphi induced by xenogeneic cells in SCID mice stimulated T cell recruitment after transfer to immunocompetent mice. T cells in turn were required for Mphi activation and xenogeneic cell rejection. Thus, Mphi harvested from immunocompetent but not SCID mice injected with xenogeneic cells expressed activation markers and rejected xenogeneic cells when transferred into SCID mice. These findings demonstrate the interdependent roles of Mphi and T cells in xenograft rejection. The requirement for Mphi reflects their ability to mount a rapid, local innate response that stimulates T cell recruitment and, having received T cell help, to act as direct effectors of rejection.

Event-related potential indices of semantic processing in schizophrenia

Event-related potentials (ERPs) were recorded while schizophrenic patients and healthy controls read congruous and incongruous sentences in anticipation of a memory test. The schizophrenic group performed more poorly in both recognition memory and cued recall tests. The two groups did not differ in the amplitude of the N400 component of the ERP but the difference between the ERPs to congruous and incongruous sentences persisted longer in the schizophrenic sample. The schizophrenic sample also showed reduced parietal positivity and a reduced effect of congruity on the late positive component that follows N400. Within the schizophrenic sample, measures of attentional impairment and positive thought disorder were correlated with mean amplitude of both the N400 and the subsequent positivity. The results imply that the structure and spread of activation within semantic memory is not impaired in schizophrenia. Rather, impairments appear to lie in processes required to integrate activated information with the current context.

Effects of long-term cannabis use on selective attention: an event-related potential study

Brain event-related potentials (ERPs) were recorded from nine long-term cannabis users during a complex auditory selective attention task and compared with nine nonuser controls. Stimuli consisted of a random sequence of tones varying in location, pitch and duration. Subjects were instructed to respond to long-duration tones of a particular pitch and location. Cannabis users' task performance was significantly worse than controls. The most striking difference between the ERPs of the two groups was in the greatly enhanced early processing negativity in the user group to short-duration stimuli which matched the target on location only. This is indicative of users engaging in unnecessary pitch processing and thus having difficulty in setting up an accurate focus of attention and in filtering out irrelevant information. The data suggest a dysfunction in the allocation of attentional resources and stimulus evaluation strategies. These results imply that long-term cannabis use may impair the ability to efficiently process information.

Modifications in the alditol acetate method for analysis of muramic acid and other neutral and amino sugars by capillary gas chromatography-mass spectrometry with selected ion monitoring

Two alditol acetate methods for the gas chromatographic (GC) analysis of neutral and amino sugars were compared. Following sodium borohydride reduction, one method uses methylimidazole as an acetylation catalyst without prior removal of water or borate salts and the other method uses sodium acetate after removal of borate and water. Depending on the acetylation conditions, muramic acid produced different derivatives. With methylimidazole, reliable derivatization of muramic acid was not possible, although other sugars derivatized reliably. With sodium acetate, all sugars tested were reproducibly derivatized. The utility of the sodium acetate method is shown by the trace GC-mass spectrometric analysis of muramic acid and rhamnose derived from bacterial peptidoglycan-polysaccharide complexes in mammalian tissue.