Acute MPTP treatment produces no changes in mitochondrial complex activities and indices of oxidative damage in the common marmoset ex vivo one week after exposure to the toxin

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) has been shown to cause a Parkinsonian syndrome in man and non-human primates. Hypotheses concerning the pathogenetic mechanisms of MPTP toxicity on nigro-striatal dopaminergic neurons relate to impairment of mitochondrial function and oxidative stress. However, surprisingly few primate studies addressed these issues ex vivo. Thus, the present study assessed the enzyme activities of the respiratory chain, GSH/GSSG and ubiquinol/ubiquinone content in the MPTP primate model (common marmoset, Callithrix jacchus; 2 mg MPTP-hydrochloride/kg body wt were injected subcutaneously (s.c.) on four consecutive days; animals were sacrificed 7 days after last MPTP exposure). Activities of respiratory chain enzymes were measured in crude homogenates of the caudate nucleus, because the probable toxic metabolite of MPTP, MPP+, is transported into dopaminergic neurons via the dopamine uptake system in striatal synapses and mitochondria are concentrated in axonal terminals. Since MPP+ can damage membranes of axonal terminals of nigro-striatal neurons we measured GSH/GSSG contents in the putamen and ubiquinol/ubiquinone concentrations in the substantia nigra and putamen as indices of oxidative damage. At the time of sacrifice MPTP-induced deficits comprised severe behavioural Parkinsonian symptoms, profound depletion of striatal dopamine and its major metabolites as well as pronounced loss of nigro-striatal neurons. Despite these severe lesions, acute MPTP treatment had no effect on any of the enzymes of the respiratory chain in the caudate nucleus and indices of oxidative damage in both the substantia nigra and putamen. These results suggest that factors other than mitochondrial impairment and/or oxidative stress may be involved in MPTP neurotoxicity in primates. Alternatively, early compensatory mechanisms and/or transient effects could account for the reported results and will be discussed.

Depression in Parkinson's disease: biogenic amines in CSF of "de novo" patients

INTRODUCTION

Etiology of depression in Parkinson's disease (PD) is associated with serotonergic dysfunction. Previous studies, supporting this hypothesis, were performed on patients treated with antiparkinsonian drugs. To eliminate the influence of parkinsonian drug therapy and to elucidate significance of different biochemical pathways in PD associated with depression we determined levels of biogenic amines in cerebrospinal fluid (CSF) of 26 untreated "de novo" Parkinsonian patients.

MATERIAL AND METHODS

Patients were scored with the Hamilton depression scale (HD) and subdivided into groups with HD score > or = 18 and HD score < 18. Diagnosis of depression was made according to DSM III R. Both groups were matched for age and motor disability.

RESULTS

In both groups no significant differences appeared between CSF levels of dopamine, noradrenaline, 3,4-dihydroxyphenylacetic acid, homovanillic acid, 3-methoxy-4-hydroxyphenylglycol and 5-hydroxyindole acetic acid, determined by high-performance liquid chromatography.

DISCUSSION

In contrast to previous studies on treated Parkinsonian patients no sign of altered serotonin metabolism especially in context with severity of depression in early stages of PD was found. Due to our results, we suggest, that biochemical markers of depression in CSF of PD may be influenced by antiparkinsonian therapy and that depression in PD may respond to serotonin reuptake inhibitors mainly in later stages of PD.

Animal models of Parkinson's disease: an empirical comparison with the phenomenology of the disease in man

Animal models are an important aid in experimental medical science because they enable one to study the pathogenetic mechanisms and the therapeutic principles of treating the functional disturbances (symptoms) of human diseases. Once the causative mechanism is understood, animal models are also helpful in the development of therapeutic approaches exploiting this understanding. On the basis of experimental and clinical findings. Parkinson's disease (PD) became the first neurological disease to be treated palliatively by neurotransmitter replacement therapy. The pathological hallmark of PD is a specific degeneration of nigral and other pigmented brainstem nuclei, with a characteristic inclusion, the Lewy body, in remaining nerve cells. There is now a lot of evidence that degeneration of the dopaminergic nigral neurones and the resulting striatal dopamine-deficiency syndrome are responsible for its classic motor symptoms akinesia and bradykinesia. PD is one of many human diseases which do not appear to have spontaneously arisen in animals. The characteristic features of the disease can however be more or less faithfully imitated in animals through the administration of various neurotoxic agents and drugs disturbing the dopaminergic neurotransmission. The cause of chronic nigral cell death in PD and the underlying mechanisms remain elusive. The partial elucidation of the processes underlie the selective action of neurotoxic substances such as 6-hydroxydopamine (6-OHDA) or 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), has however revealed possible molecular mechanisms that give rise to neuronal death. Accordingly, hypotheses concerning the mechanisms of these neurotoxines have been related to the pathogenesis of nigral cell death in PD. The present contribution starts out by describing some of the clinical, pathological and neurochemical phenomena of PD. The currently most important animal models (e.g. the reserpine model, neuroleptic-induced catalepsy, tremor models, experimentally-induced degeneration of nigrostriatal dopaminergic neurons with 6-OHDA, methamphetamine, MPTP, MPP+, tetrahydroisoquinolines, beta-carbolines, and iron) critically reviewed next, and are compared with the characteristic features of the disease in man.

Relationship between ionized and total magnesium in serum

The relationship between the concentration of ionized magnesium and total magnesium was investigated. Ionized magnesium was determined by an ion-selective electrode (Microlyte 6, KONE) and the result was adjusted to pH 7.4. Total magnesium concentration was measured by flame atomic absorption spectrometry. Total and ionized magnesium were only closely related in marked hypermagnesaemia (> 1.2 mmol/L), but correlation was poor in samples with slightly elevated total concentration or in hypomagnesaemia (< 0.65 mmol/L). The relationship was dependent on protein concentration. The agreement between total and ionized magnesium was acceptable in normoproteinaemia, but in hypoproteinaemia (< 40 g/L) total magnesium concentration was classified in 35% of the samples as below or within the reference interval, whereas the pertinent ionized magnesium concentration was normal or elevated, instead. Studies on paraproteinaemic sera clearly demonstrated that albumin concentration is most important for the size of the protein bound fraction.

New horizons in molecular mechanisms underlying Parkinson's disease and in our understanding of the neuroprotective effects of selegiline

There have been many claims that the selective monoamine oxidase type B (MAO-B) inhibitor selegiline may have distinct properties in slowing the progression of Parkinson's disease (PD). Degeneration of nigro-striatal dopaminergic neurons is the primary histopathological feature of PD. Although many different hypotheses have been advanced, the cause of chronic nigral cell death and the underlying mechanisms remain elusive as yet. Therefore, there is no clear knowledge regarding an understanding of the reported effects of selegiline on the progression of PD. However, there is a considerable body of indirect evidence that oxidative stress may play a role in the pathogenesis of this illness. Oxidative stress refers to cytotoxic consequences of hydrogen peroxide and oxygen-derived free radicals such as the hydroxyl radical (.OH), the superoxide anion (.O2), and nitric oxide (NO), which are generated as byproducts of normal and aberrant metabolic processes that utilize molecular oxygen. On the other hand, an increasing body of experimental data has implicated excitotoxicity as a mechanism of cell death in both acute and chronic neurological disease. One of the receptor which is particularly involved in the toxic effects of excitatory amino acids is the NMDA (N-methyl-D-aspartate) receptor. Excessive stimulation of this type of receptor by glutamic acid or NMDA agonists leads to a massive influx of calcium ions into the neuron followed by activation of a variety of calcium-dependent enzymes, impaired mitochondrial function, and the generation of free radicals. This article will consider the concept that excitotoxicity is linked with the generation of free radicals. In view of this idea it will be further discussed how selegiline might exert its neuroprotective effects via indirect actions on the polyamine binding site of the NMDA receptor. Under treatment with the MAO-B inhibitor selegiline, the degradation of putrescine via MAO, a key factor in regulating the polyamine metabolism, might be diminished in the Parkinsonian brain, which in turn would suppress the polyamine synthesis. Hence, the reported neuroprotective effect of selegiline might also receive a contribution from the diminished potentiation of the NMDA receptor by the polyamine binding site. On the other hand, since N1-acetylated spermine and spermidine are also good substrates of MAO-B, it is likely that these compounds will be present in the brain in increased concentrations. It therefore seems possible that they will exert a neuroprotective effect via an antagonistic modulation of the polyamine binding site of the NMDA receptor.

Interleukin-1 beta and interleukin-6 are elevated in the cerebrospinal fluid of Alzheimer's and de novo Parkinson's disease patients

Interleukin-1 beta (IL-1 beta), interleukin-2 (IL-2), and interleukin-6 (IL-6) were measured in the cerebrospinal fluid (CSF) and plasma of 12 control subjects, 11 sporadic Alzheimer's disease (AD) and 22 de novo Parkinson's disease (PD) patients using high sensitivity enzyme-linked immunosorbent assays (ELISA). IL-1 beta and IL-6 contents were significantly elevated in the CSF of de novo PD and AD patients in comparison to the control group. In contrast, the plasma levels were not significantly affected. IL-2 contents in the CSF and plasma samples were unchanged in the three groups compared. Because the two cytokines IL-1 beta and IL-6 are known to play a key role in the interaction between the nervous and immune system, e.g. in the so-called acute phase response, our results support the involvement of immunological events in the complex process of neurodegeneration in AD and PD.

Mössbauer spectroscopic studies of purified human neuromelanin isolated from the substantia nigra

57Fe Mössbauer spectroscopy at different temperatures has been used to characterize the nature of purified human neuromelanin isolated from the substantia nigra. The quantitative determination of iron(III) by estimation of the overall area of the Mössbauer spectrum at room temperature reveals an iron content of 2.8 +/- 1.4%. No subspectra corresponding to divalent iron could be observed in these spectra. The derived Mössbauer parameters lead to the conclusion that the iron sites in the human neuromelanin are similar to those of human hemosiderin (or ferritin). However, owing to the water insolubility of the purified neuromelanin, it must be concluded that the neuromelanin hemosiderin (or ferritin) is bound in a protein matrix that makes it insoluble and difficult to stain histochemically. This protein attachment to neuromelanin is important in that it is what makes it different from synthetic dopamine melanin.

Regional distribution and characterization of nitric oxide synthase activity in the brain of the common marmoset

The distribution of nitric oxide synthase (NOS) within the brain of the common marmoset, a non-human primate species, was investigated using the [3H]L-citrulline formation assay and Western blot analysis. No hemispheric asymmetry of specific NOS activity was shown. The highest levels of NOS were found in the putamen and caudate nucleus--more than twice those in the cortex and the cerebellum, the brain regions with the lowest activities. The regional distribution pattern was similar to that in the ferret brain and contrasted to that in the mouse and bovine brain. Analysis of NOS catalytic activities in subcellular fractions revealed marked differences in the subcellular localization. Neuronal NOS accounted mainly for the measured catalytic activity in the brain. Differences in the regional distribution pattern of brain NOS activity among species may be indicative of diversities in the functional role of nitric oxide and NOS in mammals.

Pretreatment with nimodipine prevents MPTP-induced neurotoxicity at the nigral, but not at the striatal level in mice

The present study assessed the effects of pretreatment with the calcium-L-type channel blocker nimodipine on biochemical and histological parameters of systemic MPTP-induced (2 x 40 mg kg-1 body weight subcutaneously, 16 h apart), dopaminergic neurotoxicity in black C57BL/6 mice. Continuous administration of nimodipine via subcutaneously implanted pellets (10 mg), starting 7 days before administration of MPTP, did not antagonize the striatal MPTP-induced dopamine depletion (caudate-putamen: 80% of control; nucleus accumbens; 25% of control), but almost completely prevented the MPTP-induced tyrosine hydroxylase immunoreactive-cell loss in the substantia nigra (20% of control) 7 days after administration of MPTP. This data suggests that pretreatment with nimodipine--during the observation period of 7 days--protects against MPTP-induced neurotoxicity in mice at the nigral ('cell body'), but not at the synaptic striatal level.

Altered brain metabolism of iron as a cause of neurodegenerative diseases?

Iron is the most abundant metal in the human body (Pollitt and Leibel, 1982; Youdim, 1988), and the brain, like the liver, contains a substantially higher concentration of iron than of any other metal (Yehuda and Youdim, 1988). Within the brain, iron shows an uneven distribution, with high levels in the basal ganglia (substantia nigra, putamen, caudate nucleus, and globus pallidus), red nucleus, and dentate nucleus (Spatz, 1922; Hallgren and Sourander, 1958; Hill and Switzer, 1984; Riederer et al., 1989). Iron deposition in the brain is mainly in organic storage forms such as ferritin but not hemosiderin (Hallgren and Sourander, 1958; Octave et al., 1983), with relatively little in a free and reactive form. Although the function of a regionally high brain iron content is unknown, the homeostasis of brain iron is thought to be necessary for normal brain function, especially in learning and memory (Youdim et al., 1989; Yehuda and Youdim, 1989; Pollit and Metallinos-Katsaras, 1990; Youdim, 1990). Thus, a high content of brain iron may be essential, particularly during development, but its presence means that injury to brain cells may release iron ions that can lead to oxidative stress via formation of oxygen free radicals. Such radicals are thought to be involved in lipid peroxidation of the cell membrane, leading to increased membrane fluidity, disturbance of calcium homeostasis, and finally cell death (Youdim et al., 1989; Halliwell, 1992). Iron is an essential participant in many metabolic processes, including (a) DNA, RNA, and protein synthesis, (b) as a cofactor of many heme and nonheme enzymes, (c) the formation of myelin, and (d) the development of the neuronal dendritic tree (Ben-Shachar et al., 1986; Youdim et al., 1991b). A deficiency of iron metabolism would therefore be expected to alter some or all of these processes (Jacobs and Worwood, 1980; Youdim, 1985, 1988). Studies of iron distribution in the human brain have demonstrated that the degree of iron deposition, primarily in the basal ganglia (a predominantly dopamine structure), increases with age (Hallgren and Sourander, 1958) and in certain disorders, most notably the basal ganglia disorders (Seitelberger, 1964). This review will present some of the experimental evidence indicating a role of disturbed iron metabolism as a cause of the neurodegenerative disorder Parkinson's disease and possibly other neurodegenerative disorders such as Alzheimer's disease.(ABSTRACT TRUNCATED AT 400 WORDS)

Is selegiline neuroprotective in Parkinson's disease?

Recent findings emphasize the significance of oxidative mechanisms, involving the activity of monoamine oxidase (MAO) and the formation of free radicals, in the pathogenesis of Parkinson's disease. The possible role of such mechanisms in the degeneration of neurones in the substantia nigra has led to clinical trials aimed at preventing or slowing the progressively disabling course of the disease. However, conclusive clinical evidence of a neuroprotective effect in PD is still lacking. In this paper, we discuss possible mechanisms by which selegiline manifests neuroprotective effects in experimental and clinical situations. Besides MAO-B inhibition, which above all explains the prevention of protoxin activation and substrate oxidation by MAO-B, selegiline appears to exhibit other mechanisms of action (induction of superoxide dismutase, stimulation of neurotrophic factor synthesis, antagonistic modulation of the polyamine binding site of the NMDA-receptor) which are independent of its action on MAO-B.

Relevance of tumour necrosis factor-alpha and interleukin-1-alpha in the pathogenesis of hypoxia-related organ failure

Tumour necrosis factor-alpha (TNF) and Interleukin-1-alpha (IL-1) are both cytokines which are known to be released by stimulated macrophages during septic events. Because of their influence on the function of the vascular endothelium, TNF and IL-1 contribute to the pathogenesis of hypoperfusion and organ dysfunction. The finding of elevated cytokine levels in patients with hypoxic organ failure, suggesting a relation between systemic oxygen supply and humoral mechanisms, led us to perform laboratory investigations on the relevance of TNF and IL-1 for the pathogenesis of hypoxia-related deterioration of the microcirculation. In vivo studies with anaesthetized rats demonstrated a synergism between hypoxaemia and endotoxaemia on the development of lethal organ failure. In vitro studies with human monocytes showed that a hypoxic atmosphere was not able to induce synthesis or release of TNF and IL-1, whereas re-oxygenation after hypoxia initiated a significant increase in TNF and IL-1 synthesis, probably mediated by oxygen radicals. Finally, experiments with human endothelial cells established that hypoxia is able to induce high affinity receptors for TNF in a time- and dose-dependent manner. These studies demonstrate that hypoxia influences humoral mechanisms which are known to contribute to the pathogenesis of vessel dysfunction, probably through a cytokine-dependent pathway of hypoxia-related organ dysfunction.

Effects of nimodipine on the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced depletions in the biogenic amine levels in mice

In view of the calcium hypothesis the effect of nimodipine (Bay e 9736, CAS 66085-59-4) on the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced depletions in dopamine and serotonin were investigated in C57-BL/6 mice. Oral treatment with nimodipine (5 mg/kg and 20 mg/kg b.i.d., respectively, for 9 days) prior to, during and following administration of MPTP appeared to attenuate MPTP-induced neurochemical changes in a dose-related manner. The results suggest that nimodipine reduces MPTP-induced damages, especially in the serotoninergic system, through its calcium antagonistic effects.

Isolation and characterization of two binding proteins for advanced glycosylation end products from bovine lung which are present on the endothelial cell surface

Nonenzymatic glycosylation of proteins, as occurs at an accelerated rate in diabetes, can lead to the formation of advanced glycosylation end products of proteins (AGEs), which can bind to endothelial cells, thereby altering cellular function in a manner which could contribute to the pathogenesis of diabetic angiopathy. In this report, we describe the isolation of two endothelial cell surface-associated proteins which mediate, at least in part, the interaction of AGEs with endothelium. Based on pilot studies demonstrating AGE binding activity with comparable characteristics in bovine endothelial cell and lung extracts, the material from lung was sequentially subjected to chromatography on hydroxylapatite, fast protein liquid chromatography Mono S, and gel filtration. Two distinct polypeptides, approximately 35 and approximately 80 kDa, were purified to homogeneity, each of which bound AGEs as demonstrated by competitive binding assays using cellular binding proteins immobilized on a plastic surface. NH2-terminal sequence analysis indicated that the approximately 35-kDa protein was novel, whereas the NH2-terminal sequence of the approximately 80-kDa protein was identical to that of lactoferrin. Immunocytologic studies using polyclonal antibody prepared to each of the purified polypeptides demonstrated the presence of immunoreactive material on the surface of bovine endothelial cells maintained under serum-free conditions. Furthermore, immunoelectron microscopic studies with antibodies to the approximately 35- and approximately 80-kDa AGE-binding proteins conjugated to different size colloidal gold particles confirmed the presence of the target antigens on the cell surface and suggested that they were closely associated. IgG purified from polyclonal antisera to either the 35- or 80-kDa AGE-binding proteins blocked the binding of 125I-AGE-albumin to the cell surface. These results indicate that endothelial cells express specific cell surface molecules which mediate AGE-endothelial interaction. These polypeptides represent a novel class of cell surface acceptor molecules for glucose-modified proteins which may promote degradation and/or transcytosis of the ligand, and modulation of cellular function.

The molecular pharmacology of L-deprenyl

L-Deprenyl, the selective inhibitor of monoamine oxidase type B (MAO-B), has gained wide acceptance as a useful form of adjunct therapeutic drug in the treatment of Parkinson's disease. This review summarizes the molecular pharmacology of L-deprenyl, and the advances in our understanding of its possible mode of action in Parkinson's disease. L-Deprenyl belongs to the class of enzyme-activated irreversible inhibitors also described as 'suicide' inhibitors, because the compound acts as a substrate for the target enzyme, whose action on the compound results in irreversible inhibition. L-Deprenyl first of all forms a noncovalent complex with MAO as an initial, reversible step. The subsequent interaction of L-deprenyl with MAO leads to a reduction of the enzyme-bound flavin-adenine dinucleotide (FAD), and concomitant oxidation of the inhibitor. This oxidized inhibitor then reacts with FAD at the N-5-position in a covalent manner. The observed in vitro selectivity of L-deprenyl for MAO-B may be accounted for by differences in the affinities of the two MAO subtypes for reversible interaction with L-deprenyl, differences in the rates of reaction within the noncovalent complexes to form the irreversibly inhibited adduct, or a combination of both these factors. However, if selective inhibition is to be maintained in vivo, correct dosage schedules are critically important, since all selective MAO inhibitors described up to now lack selectivity at high doses. In experimental animals L-deprenyl is protective against the damaging effects of several neurotoxins, including the dopaminergic agents 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 6-hydroxydopamine (6-OHDA) and the noradrenergic neurotoxin N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4). Beside MAO-B inhibition, which above all explains the prevention of neurotoxic action of MPTP by preventing its metabolism, L-deprenyl appears to exhibit other mechanisms of action which are independent of its action on MAO-B.

MPTP mechanisms of neurotoxicity and their implications for Parkinson's disease

Systemic administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) gives rise to motor deficits in humans and other primates which closely resemble those seen in patients with Parkinson's disease. These deficits are associated with a relatively selective loss of cells in the pars compacta of the substantia nigra and severe reductions in the concentrations of dopamine, noradrenaline and serotonin in the striatum. Similarly, in mice of various different strains the administration of MPTP also induces a marked loss of dopaminergic cells with severe depletion of biogenic amines, but higher doses of MPTP are required to produce these effects in mice than in primates. This review summarises advances made in understanding the biochemical events which underlie the remarkable neurotoxic action of MPTP. Major steps in the expression of neurotoxicity involve the conversion of MPTP to the toxic agent 1-methyl-4-phenylpyridinium ion (MPP+) by type B monoamine oxidase (MAO-B) in the glia, specific uptake of MPP+ into the nigro-striatal dopaminergic neurones, the intraneuronal accumulation of MPP+, and the neurotoxic action of MPP+. This is exerted mainly through the inhibition of the enzymes of the respiratory chain (Complex I), the disturbance of Ca2+ homeostasis, and possibly by the formation of free radicals. The relevance of the MPTP model to idiopathic Parkinson's disease is discussed.

Active site-blocked factor IXa prevents intravascular thrombus formation in the coronary vasculature without inhibiting extravascular coagulation in a canine thrombosis model

To assess the contribution of Factor IX/IXa, to intravascular thrombosis, a canine coronary thrombosis model was studied. Thrombus formation was initiated by applying current to a needle in the circumflex coronary artery. When 50% occlusion of the vessel developed, the current was stopped and animals received an intravenous bolus of either saline, bovine glutamyl-glycyl-arginyl-Factor IXa (IXai), a competitive inhibitor of Factor IXa assembly into the intrinsic Factor X activation complex, bovine Factor IX, or heparin. Animals receiving saline or Factor IX developed coronary occlusion due to a fibrin/platelet thrombus in 70 +/- 11 min. In contrast, infusion of IXai prevented thrombus formation completely (greater than 180 min) at doses of 460 and 300 micrograms/kg, and partially blocked thrombus formation at 150 micrograms/kg. IXai attenuated the accumulation of 125I-fibrinogen/fibrin at the site of the thrombus by approximately 67% (P less than 0.001) and resulted in approximately 26% decrease in serotonin release from platelets in coronary sinus (P less than 0.05). Hemostatic variables in animals receiving IXai, remained within normal limits. Animals given heparin in a concentration sufficient to prevent occlusive thrombosis had markedly increased bleeding, whereas heparin levels that maintained extravascular hemostasis did not prevent intracoronary thrombosis. This suggests that Factor IX/IXa can contribute to thrombus formation, and that inhibition of IXa participation in the clotting mechanism blocks intravascular thrombosis without impairing extravascular hemostasis.

(-)-Deprenyl treatment of patients with Parkinson's disease does not affect erythrocyte catechol-O-methyl transferase activity

(-)-Deprenyl has been increasingly used in recent years as an adjuvant with levodopa and a decarboxylase inhibitor in the treatment of Parkinson's disease. The inhibition of dopa decarboxylase and monoamine oxidase B resulting from this combination suggests that there may be a counter-regulatory increase in the activity of the third main enzyme in the catabolism of levodopa, i.e. catecholamine-O-methyl transferase (COMT). The current study on 36 patients with Parkinson's disease under long-term treatment with levodopa/dopadecarboxylase inhibitor showed, however, that the erythrocyte-COMT was unaffected by additional (-)-deprenyl medication. The patients in this study received levodopa and benserazide either with (-)-deprenyl (n = 21) or without (-)-deprenyl (n = 15). When allowance was made for the different genotypes, COMTLL, COMTLH, and COMTHH, there were no differences in the enzyme activities between the two treatment groups and the untreated controls (n = 26). On the basis of these results, consideration is given to the conditions in which COMT inhibitors are likely to be of value in the treatment of Parkinson's disease.

Treatment with antioxidants does not prevent loss of dopamine in the striatum of MPTP-treated common marmosets: Preliminary observations

Administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to common marmosets causes a profound loss of dopamine and serotonin in the striatum. Additional daily systemic treatment of monkeys with the antioxidants ascorbic acid (100 mg/kg) and alpha-tocopherol (2,350 mg/kg) prior to, during and following administration of MPTP does not prevent the loss of dopamine and serotonin in the striatum, suggesting that these antioxidants are unable to protect dopaminergic neurones against neurotoxicity of MPTP.

Neurochemical and behavioural features induced by chronic low dose treatment with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in the common marmoset: implications for Parkinson's disease?

Protracted long-term treatment of common marmosets with 15 doses (0.5-4.5 mg/kg, i.p.) of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP; total dose 25 mg/kg, given over 29 days) caused transitory changes in motor behaviour reminiscent of human Parkinson's disease. 16 days from the start of MPTP administration, all animals showed motor impairment, consisting of profound akinesia and a rigid posture, but in no case resting tremor. Biogenic amines were measured in nigrostriatal regions one month after finishing MPTP treatment. There was a profound loss of dopamine and serotonin in the substantia nigra and in the striatum; noradrenaline was only reduced in the putamen. Continuous analyses of the concentrations of biogenic amine metabolites in the CSF during this study revealed persistent dopaminergic disturbances and temporary alterations in serotoninergic and noradrenergic function.

Endothelium and regulation of coagulation

Endothelial cells form the luminal vascular surface and thus have a central role in the regulation of coagulation. One important way in which endothelial cells control the clotting system is by regulating the expression of binding sites for anticoagulant and procoagulant factors on the cell surface. In the quiescent state, endothelial cells maintain blood fluidity by promoting the activity of numerous anticoagulant pathways, including the protein C/protein S pathway. After activation, as can be brought about by cytokines, the balance of endothelial properties can be tipped to favor clot formation through coordinated induction of procoagulant and suppression of anticoagulant mechanisms. Tumor necrosis factor suppresses the endothelial anticoagulant cofactor thrombomodulin and induces expression of the procoagulant cofactor tissue factor. Working in concert, these changes can allow fibrin formation to proceed in an inflamed focus but maintain blood fluidity in the surrounding area of normal vasculature. Recent studies suggest that similar changes in endothelial coagulant properties can be induced by advanced glycosylation end products, proteins modified by glucose that accumulate in the vasculature at a rapid rate in diabetic subjects, indicating the potential relevance of these mechanisms in diabetic vascular disease.

Vascular permeability factor: a tumor-derived polypeptide that induces endothelial cell and monocyte procoagulant activity, and promotes monocyte migration

Systemic infusion of low concentrations of tumor necrosis factor/cachectin (TNF) into mice that bear TNF-sensitive tumors leads to activation of coagulation, fibrin formation, and occlusive thrombosis exclusively within the tumor vascular bed. To identify mechanisms underlying the localization of this vascular procoagulant response, a tumor-derived polypeptide has been purified to homogeneity from supernatants of murine methylcholanthrene A-induced fibrosarcomas that induces endothelial tissue factor synthesis and expression (half-maximal response at approximately 300 pM), and augments the procoagulant response to TNF in a synergistic fashion. This tumor-derived polypeptide was identified as the murine homologue of vascular permeability factor (VPF) based on similar mobility on SDS-PAGE, an homologous NH2-terminal amino acid sequence, and recognition by a monospecific antibody to guinea pig VPF. In addition, VPF was shown to induce monocyte activation, as evidenced by expression of tissue factor. Finally, VPF was shown to induce monocyte chemotaxis across collagen membranes and endothelial cell monolayers. Taken together, these results indicate that VPF can modulate the coagulant properties of endothelium and monocytes, and can promote monocyte migration into the tumor bed. This suggests one mechanism through which tumor-derived mediators can alter properties of the vessel wall.

[Mercaptopurine and silylated mercaptopurine the treatment of experimental allergic encephalomyelitis]

The therapeutic effects of mercaptopurine (6-mercaptopurine, 6-MP) and a silylated derivative (6-trimethylsilylthio-9-trimethyl-silylpurine, S-MP) were compared on the course of T lymphocyte line mediated experimental allergic encephalomyelitis (t-EAE). This transferred EAE is a passively induced model disease in Lewis rats easy to elicit, reliably reproducible and characterized by a dose-dependent lethality. If given at different points in single injections the silicon derivative is shown to be more efficient than 6-MP (43/125 surviving animals compared to 26/129), severity of disease is attenuated and number of survivors increased. Silylation is able to improve blood-brain barrier and cellular permeability; S-MP suppresses intrathecal inflammatory cells more effectively than the original immunosuppressant.

Autocrine tumor cell growth-inhibiting activities from human malignant melanoma

Autocrine-secreted tumor cell growth-inhibiting activities were isolated from supernatants of a malignant melanoma cell line, HTZ 19-dM, established from a central nervous system melanoma metastasis. HTZ 19-dM was characterized by cyto- and immunocytochemistry and karyotyping; cells were propagated in defined serum-free tissue culture medium for up to 8 months. Supernatants were ultrafiltrated, dialyzed, lyophilized, and purified by Bio-Gel P-10 gel permeation chromatography, leading to three active fraction pools, MIAI [melanoma-inhibiting activity (MIA), 2 kDa), MIAII (Mr 11,500-17,000) and MIAIII (proteins at the cutoff of Bio-Gel P-10) inhibiting growth of 19-dM cells with 50% inhibitory concentrations of 0.79 microgram/ml (MIAI), 0.13 microgram/ml (MIAII), and 16.7 micrograms/ml (MIAII). MIAII could be further purified by reverse phase high pressure liquid chromatography; the main activity displayed a 50% inhibitory concentration of 0.33 microgram/ml. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis one major band (molecular weight about 14,000) and two minor bands (up to Mr 17,000) were identified. Macromolecular synthesis was inhibited in 19-dM cells up to greater than 99.5%; tumor stem cell colony formation was reduced by 99.89%; the inhibitory effect of MIAII was irreversible, nonsaturable, and partially antagonized by a serum factor (depending on purification stage). MIAII was heat stable (3 min at 100 degrees C) and trypsin labile. The effect of MIAII on allogeneic neuroectodermal tumors was also investigated; proliferation of two of three malignant melanomas and two of four glioblastomas was inhibited up to 85.2%; proliferation of a neuroblastoma cell line could be inhibited to 33.8%, whereas normal fibroblasts and low grade gliomas were not influenced in their proliferation.

4,4-Diphenylpiperidine derivates and their sila analogues. A comparative study of their interaction with neural receptor biding sites and synaptosomal monoamine uptake

The potential anti-Parkinson drugs 1-R-4,4-diphenylpiperidines and 1-R-4,4-diphenyl-4-sila-piperidines (R = H, CH3, i-propyl and t-butyl) were evaluated for their neuroreceptor affinity with respect to their structure-activity relationship. In these compounds substitution of the central carbon at position 4 by a silicon leads to more lipophilic substances. While the binding of these compounds to dopamine, serotonin and gamma-aminobutyric acid/benzodiazepine receptors is relatively non-specific, the binding to the mu- and delta-subtypes of opiate receptors and to the 1-methyl-4-phenyl-1,2,3,6-tetra-hydropyridine receptor binding site show probably pharmacologically relevant effects. In almost all cases the sila-compounds have a slightly higher receptor affinity than the corresponding carbon-compounds. The studies on the uptake sites for the biogenic amines noradrenaline, dopamine and serotonin, on the other hand, reveal some considerable differences between the carbon- and silicon-containing analogues. The 4,4-diphenyl-4-sila-piperidine has much stronger uptake inhibiting properties for noradrenaline and serotonin than the corresponding carbon compound.

Pharmacokinetic studies with sustained-release formulations of levodopa in healthy volunteers

On the basis of the results of a large number of studies of the correlation between plasma levodopa levels and the occurrence of mobility disorders, it was concluded that side-effects such as dyskinesia, end-of-dose, peak-dose and on-off phenomena, which occur especially during levodopa long-term treatment of Parkinson patients, may be caused by fluctuations in the plasma levodopa levels. Some preliminary trials using sustained-release formulations were not up to expectations. Still, we studied the question of whether it might not be possible after all to obtain sustained plasma levodopa levels over prolonged periods of time with levodopa sustained-release (S. R.) formulations, without causing a high initial peak. For this purpose, we compared the pharmacokinetics of six different levodopa S. R. formulations with a standard preparation in two randomized cross-over trials in healthy male volunteers. Although the levodopa S. R. formulations prolonged the time to peak blood levels in all cases, a plateau that was constant over a longer period of time could not be obtained. However, none of the S. R. preparations studied gave rise to a high initial peak of the plasma levodopa concentration. The levodopa concentrations had again returned to endogenous levels within no more than 8 hours of administration of all six levodopa S. R. formulations.

The effect of silyl substituted methotrexate in the treatment of experimental allergic encephalomyelitis in rats mediated by T-line cells

The effect of methotrexate and of silyl-methotrexate were compared in the treatment of experimental allergic encephalomyelitis (EAE) mediated by T-line lymphocytes. It was demonstrated that, during the first three days after cell transfer, no difference between methotrexate and its silyl derivative could be seen. At a time when the cytotoxic lymphoblasts must have penetrated the blood brain barrier, only silyl methotrexate was able to prevent severe paralysis and death of the animals. It is suggested that the effect of N,N,O,O-Tetrakis (t-butyldimethylsilyl)-methotrexate, (N-4-N-(2,3-bis-t-butyldimethylsilyl-amino-6-pteridinyl-methyl)- methylamino-benzoyl-glutamic acid-bis-(t-butyldimethylsilyl)-ester), depends on the increased lipid solubility and permeability of the blood brain barrier of silylated drugs.

Determination of Diagnostic Levels of Arsenic in Animal Tissue: Collaborative Study

The method chosen for this collaborative study is a modification of the AOAC method for As residues, 41.009-41.012. The tissue is dry-ashed overnight at 500°C, and then dissolved in dilute HCl. The solution is diluted and an aliquot is reacted with zinc metal to evolve arsine gas. The gas is trapped in AgDDC solution and As is quantitated at 540 nm. Nine collaborating laboratories performed single analyses on 4 blind duplicate pairs of bovine liver samples which were spiked at 0, 4.3, 10.8, or 21.6 mg As/kg liver. A National Bureau of Standards control (SRM 1566 Oyster Tissue, 13.4 ± 1.9 mg As/kg) and a 1000 mg As/L standard were also submitted to the collaborators. Intralaboratory coefficients of variation ranged from 7.7 to 17.8%; interlaboratory coefficients of variation ranged from 10.9 to 19.0%. The method has been adopted official first action.

The interactions of 1-alkyl-4,4-diphenylpiperidines with opiate receptors

1-Alkyl-4,4-diphenylpiperidines inhibit the binding of mu- and delta-opiate receptor agonists to crude synaptosomal membranes of rat brain. Opiate receptor affinity is dependent on the nature of the 1-alkyl substitution. In displacing [3H]etorphine, [3H]dihydromorphine and [3H][D-Ala2,D-Leu5] enkephalin, the 1-methyl-derivative was most effective (IC50 [3H]etorphine = 9 microM, IC50 [3H]dihydromorphine = 0.71 microM, IC50 [3H][D-Ala2,D-Leu5]enkephalin = 2.1 microM). 1-t-Butyl-4,4-diphenylpiperidine and its 1-isopropyl analogue, used as antiparkinsonism drugs, exhibit distinctly lower inhibiting concentration values (50% inhibition, IC50 values).