Neuroprotective actions of lithium]

Lithium has long been one of the primary drugs used to treat bipolar mood disorder. However, neither the etiology of this disease nor the therapeutic mechanism(s) of this drug is well understood. Several lines of clinical evidence suggest that lithium has neurotrophic actions. For example chronic lithium treatment increases the volume of gray matter and the content of N-acetyl-aspartate, a cell survival marker, in bipolar mood disorder patients (Moore et al., 2000). Moreover, treatment with this mood-stabilizer suppresses the decrease in the volume of the subgenual pre-frontal cortex found in bipolar patients (Drevets, 2001). To elucidate molecular mechanisms underlying the neuroprotective and neurotrophic actions of lithium, we employed a preparation of cultured cortical neurons prepared form embryonic rats. We found that treatment with therapeutic doses (0.2-1.2 mM) of lithium robustly protects cortical neurons from multiple insults, notably glutamate-induced excitotoxicity. The neuroprotection against glutamate excitotoxicity is time-dependent, requiring treatment for 5-6 days for maximal effect, and is associated with a reduction in NMDA receptor-mediated Ca2+ influx. The latter is correlated with a decrease in Tyrosine 1472 phosphorylation levels in the NR2B subunit of NMDA receptors and a loss of Src kinase activity which is involved in NR2B tyrosine phosphorylation. Neither the activity of total tyrosine protein kinase nor that of tyrosine protein phosphatase is affected by this drug, indicating the selectivity of the modulation. Lithium neuroprotection against excitotoxicity is inhibited by a BDNF-neutralizing antibody and K252a, a Trk antagonist. Lithium treatment time-dependently increases the intracellular level of BDNF in cortical neurons and activates its receptor, TrkB. The neuroprotection can be completely blocked by either heterozygous or homozygous knockout of the BDNF gene. These results suggest a central role of BDNF and TrkB in mediating the neuroprotective effects of this mood-stabilizer. Finally, long-term lithium treatment of cortical neurons stimulates the proliferation of their progenitor cells detected by co-labeling with BrdU and nestin. Lithium pretreatment also blocks the decrease in progenitor proliferation induced by glutamate, glucocorticoids and haloperidol, suggesting a role in CNS neuroplasticity. We used animal models to investigate further therapeutic potentials for lithium. In the MCAO/reperfusion model of stroke, we found that post-insult treatment with lithium robustly reduced infarct volume and neurological deficits. These beneficial effects were evident when therapeutic concentrations of lithium were injected at least up to 3 h after ischemic onset. The neuroprotection was associated with activation of heat-shock factor-1 and induction of heat-shock protein-70, a cytoprotective protein. In a rat excitotoxic model of Huntington's disease, the excitotoxin-induced loss of striatal medium-sized neurons was markedly reduced by lithium. This lithium protection was correlated with up-regulation of cytoprotective Bcl-2 and down-regulation of apoptotic proteins p53 and Bax, and neurons showing DNA damage and caspase-3 activation. Taken together, our results provide a new insight into the molecular mechanisms involved in lithium neuroprotection against glutamate excitotoxicity. Moreover, these novel molecular and cellular actions might contribute to the neurotrophic and neuroprotective actions of this mood-stabilizer in patients, and could be related to its clinical efficacy for treating mood disorder patients. Clearly, mood-stabilizers may have expanded use for treating excitotoxin-related neurodegenerative diseases.     

Assay of different photoproducts after UVA, B and C irradiation of DNA and human skin explants

A ³²P-HPLC method was applied to study the induction of UVB-and UVC-induced DNA lesions (cyclobutane dimers, 6-4 photoproductsand Dewar isomers) in human skin explants. The employed techniquewas sensitive enough to detect the lesions at a dose of 10 J/m²UVB. Comparison of photoadduct formation under UVC and UVB indicatedthe importance of photosensitization pathways in DNA damage.Dewar isomers were detected only at a high dose of UVB. Thecompounds were identified by their photochemical reactivityand by spiking with prepared standards. Treatment with nucleaseP1 was used to identify the 5'-terminal nucleotide. UVA causedno detectable adducts.     

Isolation and characterization of mutants as an approach to a transformation system in Kluyveromyces marxianus

 A method to obtain K. marxianus mutants has been developed. Different auxotrophic mutants were isolated by nystatin and snail-enzyme enrichment procedures using an incubation time of 2 h before adding the antibiotic or the enzyme respectively. All his mutants analyzed by complementation tests turned out to belong to the same complementation group. Some of them were transformed and complemented by the S. cerevisiae HIS3 gene. These non-reverting his3 mutants contain no heterologous sequence, which is essential to make them acceptable for application in the food industry. Received: 15 November/21 December 1995     

Verhalten der menschlichen Haut gegenüber elektromagnetischer Strahlung im sichtbaren und nahen IR-Bereich

In der Gerichtsmedizin, aber auch in anderen medizinischen Bereichen besteht of die Notwendigkeit, biologische Proben optisch eindeutig zu beschreiben.Es wird daher ein Verfahren zur Beschreibung solcher Proben im Wellenlängenbereich 400 nm bis 1100 nm des elektromagnetischen Spektrums vorgestellt.     

Interactions of Phenytoin and Phenobarbital in Terms of Order and Temporal Spacing of Administration in Monkeys

The present study investigated order and temporal spacing interactions of phenytoin and phenobarbital in terms of plasma levels during multiple dosing in monkeys. Phenytoin at a dose of 30 mg/kg and phenobarbital at a dose of 3 mg/kg were administered separately to 4 animals (control group) by nasogastric intubution daily for 10 days. In four subsequent 10-day periods the drugs were administered together in 4 other animals (interaction group) at different times of the day (immediately following one another, 1/2 hr apart, and 6 hr apart) and in a different order of administration (either phenobarbital first and phenytoin later, or the reverse). Blood samples were obtained on the 5th, 8th, and 10th day of each 10-day period. The plasma data indicated: (a) phenytoin is capable of autoinduction, (b) phenobarbital lowers the levels of phenytoin under the four methods of administration studied here, and (c) phenytoin can affect the levels of phenobarbital. The latter interaction is a function of order and temporal spacing of drug administration.     

Propylene polymerization on titanium-magnesium catalysts, 3. Influence of the products resulting from the interaction of trialkylaluminium with aromatic esters on the activity and stereospecificity

The influence of the conditions of interaction between AlR₃ and aromatic esters (D) and of the products formed on the activity and stereospecificity of the actalytic system TiCl₄/ethyl benzoate/MgCl₂ + Al(i-Bu)₃ + D in propylene polymerization was studied. An increase of the polymerization temperature above 60°C leads to a decrease in the activity of the titaniummagnesium catalyst (TMC) and in the isotacticity of the polypropylene produced. A preliminary interaction of AlR₃ with D at elevated temperatures diminishes the isotacticity of the polymer and has no influence on the activity of TMC. IR spectroscopy was employed to study the influence of the temperature and time of AlR₃ interaction with the esters as well as that of the composition of AlR₃ (AlEt₃ or Al(i-Bu)₃) on the process of reduction of these esters. Reduction products such as aldehydes, ketones, and primary alkoxy derivatives of aluminium cannot provide of high stereopecificity of TMC. High stereospecificity is rather thought to be provided by the interaction of active sites with a free ester or tertiary alkoxy derivaties of aluminium. The contribution of each of these processes depends on the catalyst composition and on the polymerization conditions.     

Development of Methods of Assisted Circulation with Artificial Heart Ventricles

A comparative study of two methods of bypassing the heart with artificial ventricles (AV) was conducted: left atrium-aorta and left ventricle-aorta. The following factors permit left ventricular bypass to compete successfully with left ventricle-aorta bypass: creation of perfected pumps with low input impedance, use of materials with high resistance to thrombus formation for preparation of the AV and main connecting lines, and development of optimum methods of anticoagulant, disaggregation, and cardiac therapy so that there is no danger of thrombosis and hemorrhage, either experimentally or clinically. Thrombosis was the primary cause of death in only one case in a series of experiments on 15 calves with AV connected according to the atrium-aorta scheme. The positive changes in hemodynamics were approximately the same with the two methods.     

Growth of Human Marrow in Plasma Clot Diffusion Chambers

Unseparated as well as nonadherent human bone marrow cells produced colonies while suspended within plasma clots contained within diffusion chambers implanted into irradiated mice. The majority of colonies consisted of granulocytes or macro-phages. Colony size was significantly increased by the administration of endotoxin prior to implantation of the chambers.     

Modeling and Prospects for Study of Cardiovascular Pathology with the Artificial Heart

A series of models of the artificial heart has been developed for simulating different heart defects including stenosis of the atrioventricular ostium and mitral and tricuspid incompetence. Simulation of ventricular fibrillation is also possible. Repeated perturbation and restoration of artificial heart function are possible in the same animal. These processes are controlled externally. The surgical technique of implanting the artificial heart does not differ from the usual technique. Models of the artificial heart permit the study of fundamental problems in the physiology and pathology of the cardiovascular system.