• Journal of Korean Neurosurgical Society
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• v.29 no.9
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• pp.1161-1170
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• 2000

Objective : The transverse hippocampal slice is one of the most commonly studied in vitro models of mammalian brain physiology. However, despite its broad usage, there has been no standardization of slice preparation techniques or recording condition. It is well known that variations in recording conditions can result in profound different effects to neuronal responses. Evoked field potentials, recorded extracellularly, were used to investigate the effects of variations in hippocampal slice preparation protocol on hypoxia responses of CA1 neurones. Material & Methods : Before hypoxic injury, hippocampal slices were incubated for 4 hours. During incubation period, the slices were placed in a incubation chamber($21^{\circ}C$) for recovery from preparation injury and then transferred to recording chamber($34^{\circ}C$) for more recovery and baseline electric recording with current stimulation(0.1Hz). Various time periods in incubation chamber and recording chamber were applied to each experimental group(group 1=60min : 180min, group 2=90min : 150min, group 3=180min : 60min, time in incubation chamber : time in recording chamber) before 10 min hypoxia produced by replacing 95% $O_2$+5% $CO_2$ mixed gas to 95% $N_2$+5% $CO_2$ gas. Calcium, Magnesium ions and several drugs effecting on glutamate receptor also were studied. Recoveries from hypoxic injury of hippocampal slices were estimated by percent recovery of population spike(PS). Statistic analysis of study were performed using paired t-test. Results : The percent recovery of PS after 10min hypoxia was considerably enhanced by increasing the period of current stimulation during incubation period before hypoxic injury. Temperature effect on the result of this experiment was also studied(group 4) but the result from this showed no statistic significance. Low magnesium ion concentration of artificial CSF(Mg-free aCSF) during incubation period enhanced the recovery of PS but low calcium (calcium-free) and high magnesium ion concentration(2mM) reduced it after hypoxic injury. L-glutamate($100{\mu}M$) and AP-5($50{\mu}M$) had no effect on the recovery of PS but CNQX($10{\mu}M$) in artificial CSF during incubation period markedly enhanced the recovery of PS. Co-treatment of AP-5($50{\mu}M$), CNQX($10{\mu}M$) and high magnesium concentration(2mM) enhanced recovery of PS in immediate following period of hypoxic injury but the effect of cotreatment after then decayed rapidly and lost statistic significance. Conclusions : Judging from above results, the condition of baseline recording is important in observing the recovery of population spike after hypoxia, and the time and the condition should be controled more strictly to obtain reliable results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.3
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• pp.87-94
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• 2007

A structural dynamic analysis can be divided into a time domain analysis and a frequency domain analysis. The time domain analysis makes use of a direct integration method or a mode superposition method and the frequency domain analysis applies a DFT method. Generally the DFT method is more effective method in case of calculating response of periodic excitation. But in case of transient excitation exact solution can not be acquired. So, by modifying the response or increasing the period accuracy of solution can be enhanced. Accordingly this study analyzed dynamic responses of structures under aperiodic moving load in time domain and frequence domain. Consequently it is concluded that exact solution would be get enough using DFT method by increasing the duration of free vibration or modifying the dynamic response.

• Parasites, Hosts and Diseases
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• v.27 no.1
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• pp.23-34
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• 1989

In an attempt to investigate the effect of Hymenolepis dana infection on immunological responses to sRBC in ICR strain of mice, cellular and humoral immune responses were chronologically monitored after sensitization with sRBC. Mice weighing about 20 g were allocated into artificial and natural infection groups. The shell-free eggs of H. dana were inoculated into mice on the day 0 (initial) and day 10 in the former group, and praziquantel (25 mg/kg/day) was administered for 3 days to the one half of the mice at the 15th day after the first inoculation and to all of the mice in natural infection group. In artificial infection group, the delayed-type hypersensitivity (DTH) to sRBC was considerably decreased on the day 10 after the first inoculation, and then elevated gradually to normal. Eosinophils in the peripheral blood increased slightly. The hemagglutinin (HA) and hemolysin (HE) titers during the early stage were shown to be more or less higher than those of control. Thereafter, the titers were returned to normal, followed by a transient decrease on the day 15 post-infection. The sRBC rosette and antibody-treated rosette-forming capacities on the day 15 post.infection were temporarily lowered but became higher thereafter. The mucosal mast cells (MMC) in the small intestine were gradually increased to make a peak on the day 10 post-infection and then maintained more or less at lower level. After praziquantel treatment, the DTH and the number of eosinophils were decreased slightly and the MMC number and sRBC rosette-forming capacity were considerably decreased. The titers of HA and HE and antibody-treated rosette-forming capacity, however, were elevated in general. In natural infection group, the DTH, the number of eosinophils, and MMC which were elevated due to H. dana infection were gradually returned to normal after prasiquantel treatment. The titers of HA and HE which were decreased by parasite infection were increased to normal after the treatment. However, the capacities of sRBC rosette or antibody-treated rosette formation were maintained at low levels in spite of the treatment. These results revealed that the immune responses to sRBC were significantly activated during H. dana infection, although they were transiently decreased during the days 10~15 post-infection.