Age-dependent susceptibility of adult hippocampal cell proliferation to chronic psychosocial stress

Stress inhibits neurogenesis in the adult dentate gyrus. It is not known, however, whether age has any influence on this process. We subjected adult male tree shrews to 5 weeks of psychosocial stress, after which dentate cytogenesis was determined using BrdU immunohistochemistry. We found that older animals were significantly more vulnerable to the adverse effect of stress on dentate cell proliferation.     

Dexamethasone protects against dopaminergic neurons damage in a mouse model of Parkinson's disease

The pathological process of neurodegeneration, which is observed in Alzheimer's (AD) and Parkinson's (PD) diseases and that follows any insult to the central nervous system, is accompanied by an inflammatory reaction, which is believed to contribute to the pathogenesis of the diseases. In accordance to this, the anti-inflammatory agents are suggested to be effective in slowing or inhibiting the degenerative process. In this study, we investigated the influence of dexamethasone (DXM) on the nigrostriatal dopaminergic neurons damage following administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropiridine (MPTP). Mice C57BL received pre-treatment of the various doses of dexamethasone followed by MPTP administration (40 mg/kg). We found that dexamethasone 1 mg/kg diminished a dopamine content depletion in striatum by about 20%, when the doses of 0.1 mg/kg was ineffective and 10 mg/kg even aggravate the dopamine content decrease. In the second step of the experiment, we chose the effective doses, 1 mg/kg, and started the treatment before and 24 h after MPTP administration. We observed the same protection in both situations: less dopamine depletion and less decrease in the number of dopaminergic cells in the substantia nigra (SN). Dexamethasone also similarly decreased the inflammatory reaction (glial activation, lymphocytic infiltration) in the injured areas. Our study showed that dexamethasone may exert a neuroprotective effect towards neurons injured by MPTP, but only when used in a proper dose. The mechanism of dexamethasone protective properties may be an inhibition of inflammatory process; however, direct interactions with neurons are also possible.     

Primary Intraspinal Cervical Melanoma

A case of primary intraspinal melanoma is presented. This is a very rarely observed lesion, as only 37 cases have been described up to now. Patient presenting with signs and symptoms of spinal cord compression after MRI and spinal angiography was operated upon. Total removal of an intraspinal cervical tumour was performed. Histopathological investigation confirmed melanoma. Subsequent radiotherapy was given. Follow up of 4 years duration showed no signs of recurrence in MRI and full motor and sensory recovery.     

Knowledge of stroke problems among adults in Poland

An inquiry questionnaire was given to 180 adults without a history of stroke. The questions concerned the problem of stroke. The responders were aged from 15 to 82 years (mean 48 years). They were asked about risk factors for stroke, symptoms preceding stroke, behaviour of stroke witnesses. A correct definition of stroke was given by 86.7% of the responders. Only a small proportion of them knew risk factors for stroke (27.8% knew that one of them was hypertension, 6.1% gave smoking, 4.4% diabetes as risk factors). Although 93.9% knew that in face of stroke physician or ambulance service should be called, 6.1% thought that it would be sufficient to lie down or take paracetamol. The inquiry showed that the knowledge of risk factors for stroke is insufficient in the Polish adult population who not yet had cerebrovascular disturbances. It seems advisable to deliver an education programme in mass media on stroke prevention and its management in case of its development.     

Axonal degeneration in the pathogenesis of multiple sclerosis

Axonal degeneration plays an important role in the cumulation of disability in patients with multiple sclerosis (MS). Pathological studies have demonstrated axonal damage, particularly in area of acute inflammation and demyelination, and in chronic lesions. The mechanism of axonal loss is uncertain, but may involve axonal degeneration which is secondary to demyelination. Mediators of inflammation, including cytokines and proteolytic enzymes may be responsible for axonal damage, as may be nitric oxide. Moreover, axonal destruction might be due to immune cells attack directed to axonal components. The method to evaluate the intensity of cerebral and spinal cord atrophy, both reflecting axonal damage, is still searched. It is thought that therapy affecting the axonal destruction would possibly reduce progression of disability in MS patients.     

Determination of the fine epitope specificity of an anti-hepatitis B virus X protein monoclonal antibody using microanalytical and molecular biological methods

The recombinant form of the 17kDa, highly hydrophobic and disulfide-bonded hepatitis B virus X protein (HBX) was used for developing a set of monoclonal antibodies (Mab). Our present goal was to determine the fine epitope specificity of our anti-HBX Mab. Based on computer analysis two sequences (amino acids 22-31 and 100-114) were predicted for possessing high immunogenity while the anti-HBX Mab did not recognized them. Limited proteolysis and mass spectroscopic analysis suggested another possible sequence (amino acids 14-26), which also proved to be negative using an immunoserological test. Subsequently, we performed a screen of a phage displayed random peptide library, by which we could localize the epitope to amino acids 88-93. This finding was confirmed using three overlapping fusion peptides spanning amino acids 77-142. Their testing in ELISA assigned the epitope to amino acids 77-95, which supports the result obtained by screening the phage displayed library. Our results suggest the necessity of a complex application of current molecular biological and immunological techniques in fine structure mapping. This approach will be useful to study the prognostic relevance of different antigenic sites on HBX during the development of chronic hepatitis and primary hepatocellular carcinoma.     

Dynamics of expression of the mRNA for cytokines and inducible nitric synthase in a murine model of the Parkinson's disease

The inflammatory reaction and oxidative stress has been linked with PD. Proinflammatory cytokines promote neurodegeneration or neuroprotection in different animal models. In addition, these cytokines have been reported to increase iNOS expression. With the RT-PCR method we evaluated mRNA levels for IL 1beta, IL6, TNF, IFNgamma, IL-10 and iNOS in the striatum of C57BL/6 mice after MPTP intoxication. The IL1beta mRNA expression rapidly increased and peaked at 6 h. The first increase of mRNA for TNFalpha and IFNgamma was noticed at 6-24 h and the second at the 7th day after MPTP intoxication. Two peaks of IL10 mRNA were seen, immediately (6 h) and at the 3 day post MPTP injection. The peak of mRNA level for IL6 was observed at the 7th day. Expression of mRNA for iNOS peaked at 24 h, started decreasing on the 3rd day, but was still present till the 14th day. Those findings suggest that cytokine network and iNOS may be involved in the development of immune changes accompanying degeneration of the nigrostriatal system.     

Dendritic responses of frog motoneurons produced by antidromic activation

Responses to ventral root stimulation were studied in spinal cords in situ in unanesthetized frogs. Extracellular as well as intracellular recordings from motoneurons indicated that considerable depolarization of the dendrites occurred in the response to ventral root volley. Active components of this dendritic depolarization could also be observed. Extracellularly, negative field potentials were recorded both in the vicinity of motoneuron cell bodies and in areas occupied mostly by motoneuron dendrites. The refractory period of the negativity recorded at the vicinity of dendrites was longer than in the vicinity of somata. Changes in antidromic excitability were studied by the double volley technique. Augmentation of the field potential to a test volley was observed during the period of dendritic depolarization, followed by a longer-lasting period of depression of the test response. It is concluded that an action potential in frog motoneurons induces depolarization of the dendrites. The depolarized dendrites can generate local action potentials and can produce negative field potentials remotely from the somatic pool. The response of dendrites to stimulation of the ventral root has particular importance in the recurrent facilitation of the frog motoneurons.     

Hippocampal network patterns of activity in the mouse

Genetic engineering of the mouse brain allows investigators to address novel hypotheses in vivo. Because of the paucity of information on the network patterns of the mouse hippocampus, we investigated the electrical patterns in the behaving animal using multisite silicon probes and wire tetrodes. Theta (6-9 Hz) and gamma (40-100 Hz) oscillations were present during exploration and rapid eye movement sleep. Gamma power and theta power were comodulated and gamma power varied as a function of the theta cycle. Pyramidal cells and putative interneurons were phase-locked to theta oscillations. During immobility, consummatory behaviors and slow-wave sleep, sharp waves were present in cornu ammonis region CA1 of the hippocampus stratum radiatum associated with 140-200-Hz "ripples" in the pyramidal cell layer and population burst of CA1 neurons. In the hilus, large-amplitude "dentate spikes" occurred in association with increased discharge of hilar neurons. The amplitude of field patterns was larger in the mouse than in the rat, likely reflecting the higher neuron density in a smaller brain. We suggest that the main hippocampal network patterns are mediated by similar pathways and mechanisms in mouse and rat.