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

Summary 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 nigro-striatal dopaminergic neurons with 6-OHDA, methamphetamine, MPTP, MPP⁺, tetrahydroisoquinolines, -carbolines, and iron) critically reviewed next, and are compared with the characteristic features of the disease in man.     

Liver Targeting of Interferon Through Pullulan Conjugation

Purpose. The purpose of this study was to actively target interferon (IFN) to the liver through its chemical conjugation with pullulan, a water-soluble polysaccharide with a high affinity for the liver. Methods. Chemical conjugation of IFN with pullulan was achieved by a cyanuric chloride method. Following intravenous injection of the conjugates to mice, their body distribution and the activity of an IFN-induced enzyme, 2,5-oligoadenylate (2-5A) synthetase in the liver and other organs, were evaluated. Results. The cyanuric chloride method enabled us to prepare an IFN-pullulan conjugate that retained approximately 7–9 % of the biological activity of IFN. Pullulan conjugation enhanced the liver accumulation of IFN and the retention period with the results being reproducible. When injected intravenously to mice, the IFN-pullulan conjugate enhanced the activity of 2-5A synthetase in the liver. The activity could be induced at IFN doses much lower than those of free IFN injection. In addition, the liver 2-5A synthetase induced by conjugate injection was retained for 3 days, whereas it was lost within the first day for the free IFN-injected mice. Conclusions. IFN-pullulan conjugation was promising for IFN targeting to the liver with efficient exertion of its antiviral activity therein.     

Population studies of three AMPFLPs systems in a North Polish population

Allele and phenotype frequencies for D1S80, D17S5 and ApoB were determined in a population sample of more than 200 unrelated persons from North Poland using the PCR method. For D1S80, D17S5 and ApoB 19, 13 and 21 alleles respectively were observed. No deviations from Hardy-Weinberg equilibrium were detected. All three systems have discrimination values above 92% and a cumulative discrimination index of 4.5 × 10⁴.Dedicated to Prof. Dr. J. Gerchow on the occasion of his 75th anniversary     

Polymorphism analysis of the VNTR locus D17S5 in Central Spain

The fragment length polymorphism YNZ22 (D17S5) was analysed for a sample of 207 unrelated individuals living in Madrid (Spanish Caucasians) using PCR-methodology and high resolution separation. Hardy-Weinberg expectations (HWE) were calculated after pooling alleles into four groups. No deviations from HWE were detectable using the conventional ²-test. The power of discrimination was estimated as 0.96 and the mean paternity exclusion chance as 0.7587. A comparison of the allele frequency distribution with those of other Caucasian groups revealed no major differences.     

Dependence of 5-HT and catecholamine synthesis on concentrations of precursor amino-acids in rat brain

Summary The short-term influence of varying concentrations of the precursors tryptophan and tyrosine on the formation of 5-hydroxytryptophan and Dopa, respectively, in three different rat-brain regions was investigated. The concentrations of the precursors were either increased by the intraperitoneal administration of the respective precursor or decreased by loading with large neutral amino acids competing with the precursors for the same carrier mechanisms.The formation of 5-hydroxytryptophan was found to depend on the level of tryptophan in the brain in a manner predicted from published kinetic data, except when large doses of non-precursor amino acids had been given (>300 mg/kg). In the latter case the hydroxylation of tryptophan was less rapid than expected. The apparent K _m of tryptophan hydroxylase calculated from these data was about 25 M, which is in reasonably good agreement with earlier published in-vitro and in-vivo data.The formation of Dopa likewise depended on the level of the precursor tyrosine in a predictable manner, in this case without any anomalous results after large doses of non-precursor amino acids. The apparent K _m of tyrosine hydroxylase was calculated from these invivo observations to be about 25 M, which is in fairly close agreement with published in-vitro data.It is concluded that under normal conditions tryptophan hydroxylase in the rat brain is about half-saturated with its amino-acid substrate, whereas tyrosine hydroxylase appears to be about 75% saturated.     

Effects of GABA,dopamine, and substance P on the release of newly synthesized 3H-5-hydroxytryptamine from rat substantia nigra in vitro

Summary The effects of GABA, substance P and dopamine on the release of newly synthesized ³H-5-HT were investigated, using slices of rat substantia nigra superfused with l-³H-tryptophan in vitro. GABA (50 M) had no inhibitory effect on the potassium-evoked-release of ³H-5-HT. Substance P (50 M) and eledoisin (50 M) stimulated the spontaneous release of ³H-5-HT. This effect seems to be indirect and is possibly mediated by dopaminergic neurones, since the dopamine antagonist drug -flupenthixol (1 M) abolished the substance P-evoked release of 5-HT. Furthermore, it was found that substance P (10 M) stimulated ³H-dopamine release from nigral slices in vitro and the dopaminergic agonist apomorphine (50 M) also stimulated ³H-5-HT release. Substance P may, therefore, activate nigral dopaminergic neurones which then release dopamine from their dendrites. The release of dopamine may in turn stimulate 5-HT release from terminals of the raphe-nigral pathway.     

Cyclic adenosine 3′,5′monophosphate in cerebrospinal fluid of multiple sclerosis patients

Summary Cyclic adenosine 3,5monophosphate (cAMP) was assayed in CSF and plasma obtained from patients with multiple sclerosis. Decreased CSF cAMP levels were found in more than half of the patients while plasma cAMP was normal. The decrease is correlated significantly with the disability of the patient and with the progression of the disease. A low CSF cAMP level can be considered as prognostically unfavorable, particularly in the early stage of the disease. There was no correlation between the cAMP levels and the duration of the disease or with bouts and remissions. ACTH therapy did not normalize the decreased values. Obviously the decrease of CSF cAMP is related to the demyelination and not to the intensity of the pathological immunoreactions.

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Zusammenfassung Es wurde das cyclische Adenosin-3,5monophosphat im Liquor von Patienten mit multipler Sklerose untersucht. Bei einem Teil der Patienten wurden auch die Vergleichswerte im Blutplasma bestimmt. Es zeigte sich bei mehr als der Hälfte der Patienten eine Verminderung der cAMP-Konzentration im Liquor bei normalem Plasmaspiegel. Diese cAMP-Verminderung erwies sich als signifikant abhängig von dem Schweregrad der Erkrankung bzw. der Erkrankungsprogredienz und ist besonders in frühen Erkrankungsfällen als prognostisch ungünstiges Zeichen anzusehen. Es fand sich kein Zusammenhang mit dem Krankheitsstadium, d.h. Schub bzw. Intervall, und mit der Erkrankungsdauer. Eine ACTH-Behandlung vermochte diese Verminderung der Werte nicht auszugleichen. Es wird die Wertigkeit dieser Befunde diskutiert.

     

Effect of de novo purine synthesis inhibitors on 5-fluorouracil metabolism and cytotoxicity

Methotrexate pretreatment of L1210 cells had been shown previously by us to cause an enhancement of the intracellular accumulation of 5-fluorouracil and of the formation of 5-fluorouracil nucleotides which was correlated with synergistic cytotoxicity. This effect of methotrexate was associated with increases in 5-phosphoribosyl-1-pyrophosphate, the cofactor required for the conversion of 5-fluorouracil to 5-fluorouridine-5'-monophosphate (FUMP). Because these influences on 5-fluorouracil metabolism were most likely mediated by the activity of methotrexate as an inhibitor of purine synthesis, the effects of other agents that inhibit purine synthesis were examined. An inhibitor of amidophosphoribosyltransferase, 6-methylmercaptopurine ribonucleoside, the glutamine antagonists, azaserine and 6-diazo-5-oxo-L-norleucine (DON), and the L-aspartate analogue inhibitor of adenylsuccinate synthetase, L-alanosine, all reduced the incorporation of [1-14C]glycine into adenine and guanine bases isolated from nucleic acids. Each drug also resulted in intracellular elevations of 5-phosphoribosyl-1-pyrophosphate that were 15- to 25-fold greater than control levels. These alterations in de novo purine nucleotide synthesis were associated with enhanced intracellular 5-fluorouracil accumulation and synergistic cytotoxicity.