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W latach 2002-2005 w Mochełku koło Bydgoszczy przeprowadzono dwuczynnikowe doświadczenie polowe, którego celem było porównanie reakcji żyta i pszenżyta ozimego na uprawę po zbożach jarych: jęczmieniu, owsie, pszenicy, pszenżycie oraz ugorze. Eksperyment zlokalizowano na glebie płowej typowej, kompleksu żytniego dobrego, klasy bonitacyjnej IVa. Różnicę oddziaływania przedplonów na obydwa gatunki zbóż ozimych oceniono na podstawie istotności interakcyjnego oddziaływania stanowisk na strukturalne elementy plonowania i plon ziarna oraz zmienności tych cech pod wpływem przedplonów. Stwierdzono, że średnio w okresie badań reakcja zbóż ozimych na przedplon była podobna, a ich strukturalne elementy plonowania i plon ziarna nie zależały od stanowiska. Natomiast w poszczególnych latach zboża jare i ugór, stosowane jako przedplony, oddziaływały odmiennie na obsadę kłosów i plon ziarna żyta niż pszenżyta ozimego. W roku najbardziej korzystnym dla plonowania zbóż ozimych reakcja żyta i pszenżyta ozimego na zboża jare i ugór była jednakowa. W tych warunkach zboża ozime plonowały najlepiej w stanowisku po owsie.
Locomotor exercise, sufficient to increase expression of brainderived neurotrophic factor and neurotrophin 4 in the lumbar spinal cord, does not affect protein level of neurotrophin 3 (NT-3), as we have shown previously. The effect of 7 days of direct, lowfrequency electrical stimulation of the tibial nerve on expression of NT-3 was also negligible although this stimulation was addressed to low-threshold muscle afferents expressing the NT-3 and its high-affinity receptor trkC. To verify whether upregulation of NT-3 requires stronger stimulation, we maximized efficiency of electrical stimulation. Hoffmann reflex, recorded from the soleus muscle, allowed controlling low-threshold stimulation delivered by cuff electrode implanted over the tibial nerve. Electrodes were implanted bilaterally. The nerve was stimulated unilaterally for 7 days, starting 3 weeks after surgery. The contralateral limb served as a control. Series of 3 rectangular pulses of 200 µs duration and 4 ms inter-pulse intervals were applied every 25 ms in four 20 min sessions daily. NT-3 was evaluated in supernates of homogenates from L1 – L2 and L3 – L6 segments of the spinal cord and in the soleus muscles with ELISA. In intact rats (n=4) NT-3 concentration amounted to 225 pg/mg of protein in the soleus muscle and about 60 pg/mg in lumbar segments of the spinal cord. NT-3 increased by 77% in the soleus muscle on stimulated and by 18% on non-stimulated side, comparing to intact rats. In L3 – L6 segments of the spinal cord the NT-3 was raised by 35% and 15 % on stimulated and non-stimulated side, respectively. In L1 – L2 segments there was bilateral increase of NT-3 by about 30%. We show that high-frequency low-threshold stimulation of the tibial nerve, by means of chronically implanted cuff electrodes, is capable to activate NT-3 protein both in the soleus muscle and in the caudal lumbar spinal cord indicating that also NT-3 expression is regulated in activity-dependent manner. Supported by MSE grant N N401 0480 33.
BACKGROUND AND AIMS: NMDA receptor hypofunction is widely considered to contribute to the symptoms of schizophrenia. Although the pathophysiology of this disease remains unclear the nucleus accumbens (NAc) is one of the brain regions that has been widely implicated. Abnormal high frequency oscillations (HFO, 130–180 Hz) can be recorded in the rat NAc after injection of NMDA receptor antagonists. We have shown previously that reversible inhibition of the NAc by local infusion of tetrodotoxin reduces the amplitude of MK801-enhanced HFO indicating that this oscillation is generated by the intrinsic NAc network. Afferent regions powerfully modulate the activity of NAc neurons. However, it is not known to what extent HFO in the NAc may be driven by its afferent projections (ventral hippocampus, basolateral amygdala, prefrontal cortex and the vental tegmental area). METHODS: To address this issue, rats were implanted with electrodes in the NAc and guides targeted at these afferent sites. RESULTS: We found that infusion of TTX to the ventral tegmental area reduced the power of MK801-enhanced HFO on the ipsilateral but not contralateral side. In contrast infusion of TTX to the prefrontal cortex or ventral hippocampus had negligible effect MK801-enhanced HFO, although TTX infusion to the amygdala was found to produce a much weaker reduction in HFO power. CONCLUSIONS: These findings indicate that projections from the ventral tegmental area are capable of driving abnormal HFO in the NAc after injection of NMDA receptor antagonist. Further it suggests a loop involving these regions are required for the generation of HFO in rodent NAc. Project funded by the National Center of Science DEC-2011/03/B/ NZ4/03053.
BACKGROUND AND AIMS: To examine the effect of NMDA receptor antagonists and antipsychotics on high frequency oscillations (HFO, 130–180 Hz) recorded in local field potentials from the nucleus accumbens (NAc) of freely moving mice. To identify the receptors that may underlie clozapine-induced reductions in HFO frequency. METHODS: Freely moving mice, with electrodes implanted in the NAc, received systemic injection of NMDAR antagonists (ketamine and MK801); antipsychotic compounds (clozapine and haloperidol) were administered to MK801-pretreated mice. We attempted to identify the receptors mediating clozapine-induced reductions in HFO frequency using a pharmacological agents targeting 5HT1A, 5HT2A, histamine H3 and NMDA receptors. RESULTS: Ketamine and MK801 dose dependently increased the power of HFO and produced small increases in their frequency. Clozapine, dose dependently reduced the frequency of HFO whereas haloperidol had little effect on HFO. Systemic injection of glycine, which has antipsychotic properties, and allosterically modulates NMDAR, reduced the frequency of HFO to values comparable after injection of clozapine. Systemic administration of NMDA produced a short-lasting reduction in MK801-enhanced HFO frequency. Other receptors known to be targets for clozapine, namely 5-HT2A, 5-HT7 and histamine H3 receptors had no effect on MK801-enhanced HFO, although we did find a reduction in HFO frequency after injection of 5HT1A agonist. CONCLUSIONS: These results show that NMDAR antagonists and antipsychotics produce broadly similar fundamental effects on HFO in mice and rats. Stimulation of NMDAR (directly, or through the glycine site) as well as activation of 5HT1A receptors, reduces the frequency of MK801-enhanced HFO suggesting that atypical antipsychotic drugs may alter HFO by interacting with NMDA and 5HT1A receptors. Project funded by the National Center of Science DEC-2011/03/B/ NZ4/03053.
Availability of brain-derived neurotrophic factor (BDNF) and neurotrophin 4 (NT-4) in the nervous system depends on the neuronal activity. We have previously shown that moderate locomotor exercise causes an increase of BDNF and NT-4 proteins but not neurotrophin 3 (NT-3) in the lumbar spinal cord. The questions arise whether NT-3 is regulated in a different way than BDNF and NT-4 or, that proprioceptive stimulation during treadmill locomotion is not sufficient to activate NT-3? To verify the latter possibility we applied direct electrical stimulation of the tibial nerve to activate the low-threshold muscle afferent fibers eliciting monosynaptic Hoffmann (H) reflex, an analog of the stretch reflex. Both the H-reflex and direct motor response (M), recorded from the soleus muscle, allowed keeping the strength of stimulus near the threshold of M response, confirming that stimulus is primarily addressed to lowthreshold afferents. The cuff stimulating electrode over the nerve and recording intramuscular electrodes were implanted bilaterally. The tibial nerve was stimulated unilaterally, throughout one and four weeks, starting two weeks after implantation of electrodes. The contralateral limb served as a control. Two sessions of stimulation daily, 30 min each (rectangular pulse of 300 µs duration at 0.33 Hz) were separated by about 2 h break. The total number of stimuli delivered was about 800 per day. The expression of NT-3 in the spinal cord was evaluated immunohistochemically (IR, Santa Cruz antibody) in the lumbar L4/L5 segments. Both neuropil and numerous cell bodies expressed NT-3. Perikaryonal expression was predominantly observed in the lower dorsal horn laminae (III- VI), in the intermediate zone and in the lamina IX. However, the effects of implantation and stimulation on the expression of NT-3 was negligible. The effect will be verified quantitatively with Elisa method. Supported by MSE grant N N401 0480 33.
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