Cartilage-on-cartilage contact: effect of compressive loading on tissue deformations and structural integrity of bovine articular cartilage.

OBJECTIVE: This study aims to characterize the deformations in articular cartilage under compressive loading and link these to changes in the extracellular matrix constituents described by magnetic resonance imaging (MRI) relaxation times in an experimental model mimicking in vivo cartilage-on-cartilage contact. DESIGN: Quantitative MRI images, T1, T2 and T1ρ relaxation times, were acquired at 9.4T from bovine femoral osteochondral explants before and immediately after loading. Two-dimensional intra-tissue displacement and strain fields under cyclic compressive loading (350N) were measured using the displacement encoding with stimulated echoes (DENSE) method. Changes in relaxation times in response to loading were evaluated against the deformation fields. RESULTS: Deformation fields showed consistent patterns among all specimens, with maximal strains at the articular surface that decrease with tissue depth. Axial and transverse strains were maximal around the center of the contact region, whereas shear strains were minimal around the contact center but increased towards contact edges. A decrease in T2 and T1ρ was observed immediately after loading whereas the opposite was observed for T1. No correlations between cartilage deformation patterns and changes in relaxation times were observed. CONCLUSIONS: Displacement encoding combined with relaxometry by MRI can noninvasively monitor the cartilage biomechanical and biochemical properties associated with loading. The deformation fields reveal complex patterns reflecting the depth-dependent mechanical properties, but intra-tissue deformation under compressive loading does not correlate with structural and compositional changes. The compacting effect of cyclic compression on the cartilage tissue was revealed by the change in relaxation time immediately after loading.

Functional assessment of strains around a full-thickness and critical sized articular cartilage defect under compressive loading using MRI.

OBJECTIVE: The objective of this study was to evaluate the effect of full-thickness chondral defects on intratissue deformation patterns and matrix constituents in an experimental model mimicking in vivo cartilage-on-cartilage contact conditions. DESIGN: Pairs of bovine osteochondral explants, in a unique cartilage-on-cartilage model system, were compressed uniaxially by 350 N during 2 s loading and 1.4 s unloading cycles (≈1700 repetitions). Tissue deformations under quasi-steady state load deformation response were measured with displacement encoded imaging with stimulated echoes (DENSE) in a 9.4 T magnetic resonance imaging (MRI) scanner. Pre- and post-loading, T1, T2 and T1ρ relaxation time maps were measured. We analyzed differences in strain patterns and relaxation times between intact cartilage (n = 8) and cartilage in which a full-thickness and critical sized defect was created (n = 8). RESULTS: Under compressive loading, strain magnitudes were elevated at the defect rim, with elevated tensile and compressive principal strains (Δϵmax = 4.2%, P = 0.02; Δϵmin = -4.3%, P = 0.02) and maximum shear strain at the defect rim (Δγmax = 4.4%, P = 0.007). The opposing cartilage showed minimal increase in strain patterns at contact with the defect rim but decreased strains opposing the defect. After defect creation, T1, T2 and T1ρ relaxation times were elevated at the defect rim only. Following loading, the overall relaxations times of the defect tissue and especially at the rim, increased compared to intact cartilage. CONCLUSIONS: This study demonstrates that the local biomechanical changes occurring after defect creation may induce tissue damage by increasing shear strains and depletion of cartilage constituents at the defect rim under compressive loading.

Roux-en-Y gastric bypass in mice--surgical technique and characterisation.

BACKGROUND: A reproducible Roux-en-Y gastric bypass (RYGB) model in mice is needed to study the physiological alterations after surgery. METHODS: Male C57BL6 mice weighing 29.0 ± 0.8 g underwent either RYGB (n = 14) or sham operations (n = 6). RYGB surgery consisted of a small gastric pouch (~2 % of the initial stomach size), a biliopancreatic and alimentary limb of 10 cm each and a common channel of 15 cm. Animals had free access to standard chow in the postoperative period. Body mass and food intake were recorded for 60 days. Bomb calorimetry was used for faecal analysis. Anatomical rearrangement was assessed using planar X-ray fluoroscopy and computed tomography (CT) after oral Gastrografin® injection. RESULTS: RYGB surgery led to a sustained reduction in body weight compared to sham-operated mice (postoperative week 1: sham 27.8 ± 0.7 g vs. RYGB 26.5 ± 1.0 g, p = 0.008; postoperative week 8: sham 30.7 ± 0.8 g vs. RYGB 28.4 ± 1.1 g, p = 0.003). RYGB mice ate less compared to shams (sham 4.6 ± 0.2 g/day vs. RYGB 4.3 ± 0.4 g/day, p < 0.001). There were no differences in faecal mass (p = 0.13) and faecal energy content (p = 0.44) between RYGB and shams. CT scan demonstrated the expected anatomical rearrangement without leakage or stenosis. Fluoroscopy revealed rapid pouch emptying. CONCLUSIONS: RYGB with a small gastric pouch is technically feasible in mice. With this model in place, genetically manipulated mouse models could be used to study the physiological mechanisms involved with metabolic changes after gastric bypass.

Lasting effects of chronic fluoxetine treatment on the late developing rat brain: age-dependent changes in the serotonergic neurotransmitter system assessed by pharmacological MRI.

RATIONALE: With the growing prevalence of psychotropic drug prescriptions among children and adolescents, the need for studies on lasting effects of drug exposure on the developing brain rises. Fluoxetine is the only selective serotonin reuptake inhibitor (SSRI) officially registered to treat major depressive disorder in children. Although various (pre)clinical studies have assessed the (long-term) effects of fluoxetine exposure in the perinatal period and in adulthood, limited data is available on its effects on the developing brain later in life, i.e. during adolescence. OBJECTIVE: The present study aimed at investigating the effects of age following chronic SSRI treatment on the central serotonin (5-HT) system. To this end, pharmacological MRI (phMRI) was performed in chronic fluoxetine-treated (5 mg/kg, oral gavage for 3 weeks) juvenile (PND25) and adult rats (PND65) after a 1-week washout period, using an acute fluoxetine challenge (5 mg/kg, i.v.) to trigger the 5-HT system. RESULTS: We observed a diminished brain response to the acute challenge in adult treated animals when compared to control animals, whereas this response was increased in juvenile treated rats. As a result, a significant age by treatment interaction effect was seen in several (subcortical) 5-HT related brain regions. CONCLUSION: An opposite effect of chronic fluoxetine treatment was seen in the developing brain compared to that in matured brain, as assessed non-invasively using phMRI. These findings most likely reflect neuronal imprinting effects of juvenile SSRI treatment and may underlie emotional disturbances seen in animals and children treated with this drug. Also, our findings suggest that phMRI might be ideally suited to study this important issue in the pediatric population.

Angiotensin II type 1 receptor as a novel therapeutic target in rheumatoid arthritis: in vivo analyses in rodent models of arthritis and ex vivo analyses in human inflammatory synovitis.

OBJECTIVE: Angiotensin II (Ang II) is known to have proinflammatory actions, and Ang II type 1 (AT(1)) receptors are up-regulated in the rheumatoid synovium, suggesting that this receptor could be a therapeutic target. The purpose of this study was to investigate the antiinflammatory potential of the selective AT(1) receptor antagonist losartan, which is currently used for the treatment of cardiovascular disease. METHODS: Dose-ranging studies of losartan (1-50 mg/kg) were initially conducted in a rat model of acute (carrageenan/kaolin) arthritis, with subsequent evaluation in a rat model of adjuvant-induced arthritis (Freund's complete adjuvant). Losartan (10(-10) to 10(-6)M) was further tested ex vivo in human inflammatory synovitis, using collagenase-digested synovium. RESULTS: Western blot and immunohistochemical analyses both revealed a substantial increase in AT(1) receptor protein content in synovium from acutely and chronically inflamed rat knee joints. Similarly, synovial Ang I/II protein content was elevated during inflammation. Losartan inhibited acute joint inflammation in a dose-dependent manner, with 15 mg/kg being the optimal dose (and used in subsequent studies). Both prophylactic and therapeutic administration of 15 mg/kg of losartan substantially reduced knee joint swelling in rats with adjuvant monarthritis (> or =50%; P < 0.0001). Losartan also suppressed tumor necrosis factor alpha generation from inflamed human synovium in a dose-dependent manner (P < 0.05). CONCLUSION: Targeting the angiotensin pathway, particularly AT(1) receptors, could have significant therapeutic potential. Randomized placebo-controlled trials are now warranted to establish the extent to which angiotensin receptor blockers may provide antiinflammatory benefits.

Increased brain levels of 4-hydroxy-2-nonenal glutathione conjugates in severe Alzheimer's disease.

In the last decade an important role for the progression of neuronal cell death in Alzheimer's disease (AD) has been ascribed to oxidative stress. trans-4-Hydroxy-2-nonenal, a product of lipid peroxidation, forms conjugates with a variety of nucleophilic groups such as thiols or amino moieties. Here we report for the first time the quantitation of glutathione conjugates of trans-4-hydroxy-2-nonenal (HNEGSH) in the human postmortem brain using the specific and very sensitive method of electrospray ionization triple quadrupole mass spectrometry (ESI-MS-MS). Levels of HNEGSH conjugates calculated as the sum of three chromatographically separated diastereomers were determined in hippocampus, entorhinal cortex, substantia innominata, frontal and temporal cortex, as well as cerebellum from patients with AD and controls matched for age, gender, postmortem delay and storage time. Neither age, nor postmortem delay, nor storage time did correlate with levels of HNEGSH conjugates which ranged between 1 and 500 pmol/g fresh weight in the brain areas examined. The brain specimen from patients with clinically and neuropathologically probable AD diagnosed according to criteria of the consortium to establish a registry for AD (CERAD) show increased levels of HNEGSH in the temporal and frontal cortex, as well as in the substantia innominata. Classification of disease severity according to Braak and Braak, which takes into consideration the amount of neurofibrillary tangles and neuritic plaques, revealed highest levels of HNEGSH in the substantia innominata and the hippocampus, two brain regions known to be preferentially affected in AD. These results substantiate the link between conjugates of glutathione with a product of lipid peroxidation and Alzheimer's disease and justify further studies to evaluate the role of HNE metabolites as potential biomarkers for disease progression in AD.

Brain aging phenomena in migrating sockeye salmon Oncorhynchus nerka nerka.

Aging, a process occurring in all vertebrates, is closely related to a loss in physical and functional abilities. There is widespread interest in clarifying the relevance of environmental, metabolic, and genetic factors for vertebrate aging. In the Pacific salmon a dramatic example of aging is known. Looking for changes in the salmon brain, perhaps even in the role of initiating the aging processes, we investigated several biochemical parameters that should reflect brain functional activity and stress response such as the neurotransmitters dopamine, and serotonin, and two of their respective metabolites 3,4-dihydroxyphenylacetic acid, and 5-hydroxyindole acetic acid, as well as glutathione, glutathione disulfide, and the extent of terminal deoxynucleotidyltransferase-mediated dUTP nick end-labelling. The aging of migrating sockeye salmon (Oncorhynchus nerka nerka) is accompanied by gradual increase in dopamine and serotonin turnover and a gradual decrease of brain total protein and glutathione levels. There appears to be an increased need for detoxification of reactive biological intermediates since activities of superoxide dismutase and catalase increase with age. However, our data do not support a major increase in apoptotic cell death during late aging but rather implicate an age related downward regulation of protein and glutathione synthesis and proteolysis increasing the need for autophagocytosis or heterophagocytosis in the course of cell death.

(r)-, but not (s)-alpha lipoic acid stimulates deficient brain pyruvate dehydrogenase complex in vascular dementia, but not in Alzheimer dementia.

In dementia of Alzheimer type (DAT), cerebral glucose metabolism is reduced in vivo, and enzymes involved in glucose breakdown are impaired in post-mortem brain tissue. Pyruvate dehydrogenase complex activity (PDHc) is one of the enzymes known to be reduced, while succinate dehydrogenase activity (SDH), another enzyme of oxidative glucose metabolism is unchanged. In dementia of vascular type (DVT), variable changes in glucose metabolism have been demonstrated in vivo, while changes of enzyme activities in post-mortem brain tissue are unknown. Here, PDHc and SDH activity were stimulated with each of the two stereoisomers of alpha lipoic acid in post-mortem parietal brain cortex of patients with DAT, DVT, and one case of Pick's disease and compared to stimulation effects in a control group, matched for age, sex, post-mortem delay, and storage time of brain tissue. PDHc in DAT and DVT, but not in Pick's disease was reduced. PDHc activity could be slightly stimulated by 10 micro M of the physiological stereoisomer (r)-alpha-lipoic acid, in controls and DVT (possibly also in Pick's disease), but not in DAT. In all groups investigated SDH was activated by 100 micro M and 1 mM of both isomers of alpha-lipoic acid, whereas 10 mM of both stereoisomers of alpha-lipoic acid caused an inhibition of both, PDHc and SDH activity. The loss of basal and of (r)-alpha-lipoic acid stimulated PDHc activity indicate that a functional or structural impairment of PDHc may exist in DAT and DVT which is not merely attributable to loss of mitochondria since basal and stimulated SDH activities are similar in controls, DVT and DAT, thus indicating selective vulnerability of PDHc.

Impairment of G(salpha) function in human brain cortex of Alzheimer's disease: comparison with normal aging.

We examined the quantity and quality of G proteins in membrane preparations of post-mortem human brain, i.e. in parietal, temporal and occipital cortical regions, from normal subjects over age (17-89 years old) and with Alzheimer's disease (AD) in comparison with aged-matched controls. In normal aging, the immunoreactivities determined of G(ialpha), G(qalpha) and G(beta) were inversely correlated with age. The function of G proteins was examined by photoaffinity GTP analogue [azidoanilido GTP (AAGTP)] labelling. AAGTP labelling to G(salpha) and G(i/oalpha), and the ratio of G(salpha) to G(i/oalpha) AAGTP labelling showed no age-dependent changes. In AD compared to age-matched controls, there were no significant differences in the levels of G(sHalpha), G(sLalpha), G(ialpha), G(oalpha), G(qalpha) and G(beta) subunits. Functional effects of G proteins, however, as measured by AAGTP labelling to G(salpha), but not to G(i/oalpha), was significantly decreased in AD compared to controls in the parietal and temporal cortex, but not in the occipital cortex. These results suggest that the disturbances of post-receptor trans-membrane signalling in AD can be attributed to functional changes of G(salpha), and these are independent of alterations in the level for those proteins in normal aging.

Chronic alcohol consumption and cerebral indices of oxidative stress: is there a link?

BACKGROUND: It is still difficult to define the biochemical mechanisms that cause alterations in neuronal function and plasticity and neuronal cell loss in the brains of alcohol-dependent patients. METHODS: To evaluate the extent of cerebral alcohol-induced oxidative stress ex vivo, we investigated the levels of glutathione (GSH), its oxidation product glutathione disulfide (GSSG, produced by GSH-peroxidases), and the activities of catalase and superoxide dismutases (SOD). In addition, selected brain regions from up to 22 subjects (versus controls) were studied post mortem to compare the amount of oxidized DNA-base 8-hydroxy-2'-deoxyguanosine (8-OHdG) with levels of deoxyguanosine (dG) in mitochondrial and nuclear DNA. RESULTS: The most prominent findings showed significantly decreased GSH/(GSH+2GSSG) molar redox (oxidation-reduction) ratios in the corpus mamillare and cerebellum, which appeared due to an increase in GSSG caused by chronic alcohol intake. Catalase activity was increased in only the frontal cortex, whereas decreased catalase activity was found in the corpus callosum. In contrast, neither copper-zinc-superoxide dismutase (CuZnSOD) and manganese-superoxide dismutase (MnSOD) activities nor 8-OHdG/dG molar ratios were altered, although a tendency toward higher OHdG/dG ratios in temporal and parietal cortex from alcohol-dependent patients could be detected when mitochondrial DNA was analyzed selectively. CONCLUSIONS: We propose that decreased brain GSH/(GSH+2GSSG) molar redox (oxidation-reduction) ratios in alcohol-dependent patients may reflect neural impairment due to increased peroxide production after chronic alcohol consumption. However, future experiments, investigating the activities of enzymes and cofactors involved in GSH synthesis and metabolism in the human brain, will have to validate the specificity of these results for oxidative stress.

Inhibition of neuronal nitric oxide synthase by 7-methoxyindazole and related substituted indazoles.

The synthesis and pharmacological evaluation of methoxyindazoles as new inhibitors of neuronal nitric oxide synthase are presented. The 7-methoxyindazole, although less potent than 7-NI, is the most active compound of the series in an in vitro enzymatic assay of neuronal nitric oxide synthase activity. This result shows that the nitro-substitution is not indispensable to the biological activity of the indazole ring. 7-Methoxyindazole possesses in vivo NOS inhibitory as well and related antinociceptive properties.

Long-term effects of tricyclic antidepressants on norepinephrine kinetics in humans.

The nature of the discrepancy between short-term pharmacokinetic data (hours) on the one hand and long-term pharmacodynamic effects and the clinical latency of therapeutic amelioration on the other hand by tricyclic antidepressants is still unclear. A relapsed sensibilization of neuronal, immunologic, and endocrinologic systems by changes in receptor sensitivity has been proposed. However, the discrepancy may have a strong influence on many aspects of antidepressive therapy in humans. The aim of our study was to demonstrate long-term pharmacodynamic effects by single-dose antidepressive treatment in humans by measuring heart rate parameters in response to neurochemical parameters. 25 young healthy probands, divided into three treatment groups (amitriptyline, n = 10; clomipramine, n = 10; placebo, n = 5), were challenged by a noradrenaline infusion test at baseline and one and 21 days after a single dose of antidepressant. Heart rate and blood pressure as well as plasma levels of antidepressants and of noradrenaline and adrenaline were measured in response to noradrenaline infusion test. Noradrenaline infusion rate to reach an increase in blood pressure of RR > 30 mmHg was significantly decreased for both antidepressants on day 1. The same effect was true for the amitriptyline group on day 21. Furthermore, pretreated probands respond to antidepressants in a different way when compared to untreated probands. Like depressed patients under therapy they respond with a dramatic increase in sensitivity of the alphal-adrenergic receptor. We could demonstrate that the long-term pharmacodynamic effects have a strong influence on antidepressive therapy. A prolonged pharmacodynamic effect influences further clinical studies as well as our thinking about adverse drug effects. In clinical studies, washout periods may be to short to overcome the benefits of a previous medication. Adverse drug effects are often seen during periods when drugs were changed. The negative effect may be due to an additional effect of both medicaments.

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.

The use of cerebral blood flow as an index of neuronal activity in functional neuroimaging: experimental and pathophysiological considerations.

Over recent years, activation studies that have been undertaken using brain imaging techniques, such as functional magnetic resonance imaging, positron emission tomography or near infrared spectroscopy, have greatly improved our knowledge of the functional anatomy of the brain. Nevertheless, activation studies do not directly quantify the variations of synaptic transmission (neuronal activity) but detect it indirectly either through the visualisation of changes in cerebral blood flow, oxidative or glycolytic metabolism (for positron emission tomography), or through the measurement of a global index that is dependent on both cerebral blood flow and oxidative metabolism (for functional magnetic resonance imaging and near infrared spectroscopy). Such approaches are based on the concept of a tight parallelism--termed coupling--between variations in neuronal activity, metabolism and cerebral blood flow. However, several "uncoupled" situations between these parameters have been reported over the last decade through experimental, pharmacological and pathophysiological studies. The aim of this review is to focus on these data that have to be taken into account for the interpretation of the results obtained in activation paradigms.

Pro- and antioxidative properties of cortical tissue preparations from human brain exhibiting NMDA-receptor characteristics.

The effects of cortical tissue preparations (CTP) from human brain on the production of reactive oxygen species (ROS) has been investigated with several biochemical model reactions. As indicators for ROS, fragmentation of the methionine derivatives, alpha-keto-gamma-methylthiobutyric acid (KMB) or 1-amino-cyclopropane-1-carboxylic acid (ACC), yielding ethene have been used. With these systems we have shown that production of OH-radical-type oxidants by the xanthine oxidase (XOD)-system is strongly stimulated by CTP. This activity is due to intrinsic iron ions since ethene formation from KMB is stimulated by EDTA, inhibited by desferrioxamine (Desferal) and also visible with heat-denatured CTP. CTP by themselves have no XOD activity. 3-Hydroxykynurenine (3HK) is another possible substrate for XOD but produces H2O2 without XOD-catalysis, whereas allopurinol is not inhibiting. CTP contain measurable NAD(P)H oxidoreductase activity, producing OH- radical- type oxidants at the expense of NADPH and (to a lesser extent) NADH as electron donors, shown as redox-cycling of 2-methyl-5-hydroxy-1,4-naphthoquinone, plumbagin. Ethene formation from KMB is also driven by both morpholinosydnonimine (SIN) or ONOOH. The reaction driven by SIN is stimulated by CTP and inhibited by catalase, SOD and hemoglobin. Since ethene release from KMB driven by ONOOH is inhibited by CTP the mechanisms driving KMB fragmentation are different for SIN and ONOOH. Furthermore CTP contain approx. 4 U catalase activity per mg protein and very weak peroxidase (POD) activity shown as ACC fragmentation yielding ethene in the presence of both H2O2 and KBr or NaCl. Since ACC binds to CTP and both compounds, ACC and KMB are natural products, present in food (ACC) or synthesized from methionine in vivo (KMB), these compounds may represent protecting agents in systems where reactive oxygen species are formed. One might even speculate that the production of ethene at these membrane receptor sites may have biological functions, since ethene is known to possess anaesthetic activities.

Free radicals in Alzheimer's disease.

Alzheimer's disease is a neurodegenerative disorder comprising multisystem atrophies probably caused by multifactorial processes. The disease is characterized by typical neuropathology, impaired synaptic function and massive cell loss. The pathobiochemistry of this disorder involves oxidative stress, which accumulates free radicals leading to excessive lipid peroxidation and neuronal degeneration in certain brain regions. Moreover, radical induced disturbances of DNA, proteins and lipid membranes have been measured. The hypothesis has been proposed that cellular events involving oxidative stress may be one basic pathway leading to neurodegeneration in Alzheimer's disease. In this work we report evidence for increased oxidative stress and disturbed defense mechanisms in Alzheimer's disease, which may result in a self-propagating cascade of neurodegenerative events. Furthermore it is evident from experimental data, that aggregation of beta-amyloid and beta-amyloid toxicity is favourably caused by oxidative stress. Therefore, oxidative stress plays a key role in the conversion of soluble to unsoluble beta-amyloid, suggesting that oxidative stress is primary to the beta-amyloid cascade.

Acetylcholine in human CSF: methodological considerations and levels in dementia of Alzheimer type.

Four different methods to measure acetylcholine (ACh) and choline (Ch) concentration, i.e. thermospray/mass spectroscopy (TS/MS), high pressure liquid chromatography/mass spectroscopy (HPLC/MS), high pressure liquid chromatography/electrochemical detection (HPLC/ECD) and gas chromatography/mass spectroscopy (GC/MS), both latter methods coupled to a solid phase extraction system were compared for their applicability to human lumbar cerebrospinal fluid (CSF). Furthermore, samples from 15 control persons and 11 patients with dementia of Alzheimer-type (DAT) were compared to search for an ACh deficit in the CSF in DAT. GC/MS was the most sensitive, but most laborious method, and HPLC/ECD was acceptably sensitive, reliable and more specific. TS/MS was not specific enough for CSF extracts and HPLC/MS was more specific, but far less sensitive. Thus, only GC/MS and HPLC/ECD were qualified to detect ACh in human CSF extracts. Comparison of GC/MS and HPLC/ECD revealed highly correlated levels of ACh (r = 0.999). Using HPLC/ECD, ACh concentrations were greatly reduced in the DAT group (3.75 +/- 1.40 pmol/ml CSF) as compared to the controls (6.14 +/- 1.39 pmol/ml CSF), but the difference between controls and DAT patients was not statistically significant due to the number of samples below detection limit (8 out of 11 samples in DAT, 7 out of 15 in controls). Ch concentrations were not statistically significant between the two groups. The data show that methodological limitations preclude a widespread clinical application of determining ACh in the human CSF. Despite of reductions of ACh in the CSF in DAT, the determination of Ach in the CSF is not suitable for diagnostic purposes.

Inhibition of [3H]alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid [AMPA] binding by the anticonvulsant valproate in clinically relevant concentrations: an autoradiographic investigation in human hippocampus.

The interaction of the anticonvulsant valproate with AMPA glutamate receptors in human post mortem hippocampus was investigated. At concentrations of > or = 100 microM valproate decreased binding of 40 nM [3H]AMPA to 45+/-56% of control level (CA 1). Clinically effective brain concentrations for valproate are estimated at 100-200 microM. Our results thus provide evidence that the anticonvulsant effects of valproate may partially be caused by interaction with AMPA receptors.

Platelet monoamine oxidase B activity in dementia. A 4-year follow-up.

Platelet monoamine oxidase B (MAO-B) activity has been found to increase significantly in demented patients. For the first time, a 4-year follow-up of platelet MAO-B activity and Mini-Mental State (MMS) was performed in patients with probable dementia of the Alzheimer type (DAT) and age-matched controls. MAO-B activity of DAT patients increased significantly 2 years after the beginning of the study as compared with controls and remained significantly higher for the entire period of the examinations (p < 0.0001). The decrease of the MMS scores did not correlate with the time course of the increase of platelet MAO-B activity (Spearman rank correlation test). The decline of the MMS scores of DAT patients preceded the elevation of MAO-B activity. Since degenerative processes in brain areas which are responsible for cognitive function and are reflected by the MMS scores rather affect cerebral cholinergic than monoaminergic neurotransmitter systems, degeneration of the latter at late stages of DAT might be reflected by increased platelet MAO-B activity.

Time course of manganese superoxide dismutase concentrations in serum of alcohol-dependent patients during abstinence.

Mean manganese superoxide dismutase (Mn-SOD) concentrations in the serum of patients suffering from alcohol dependence is almost twice as high as in serum of non-dependent controls. In order to investigate the time course of this parameter during abstinence, we determined it at different time points. Patients had mean Mn-SOD serum concentrations (+/-S.D.) of 150.4 +/- 76.3, 121.1 +/- 40.7, 94.6 +/- 37.8 micrograms/ml at 1, 10 and 40 days after abstinence compared to 76.3 +/- 16.9 micrograms/ml as mean Mn-SOD value in the control group. Although the Mn-SOD concentration tended to normalise during abstinence, the differences between index and control group remained significant up to the last measurement at day 40.