Research progress on Alzheimer's disease: pathogenesis and medical therapy / 中国医学科学院学报

Alzheimer's disease (AD) is a common disease in elder people. Its incidence rate is about 5% in people above 60 years old. It has become an important factor that seriously impacts the development of families and society, and caused wildly attention all over the world. In this article, we discuss the mechanisms of AD in four aspects and put forward the strategies of drug therapy.

Age-related Changes of Doublecortin Positive Cells in the Olfactory Bulb of the Rat / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: It is well-established that neurogenesis continues to occur during life in the restricted brain areas, such as the glomerular and granule cell layers of the olfactory bulb. Doublecortin is a protein required for neuronal migration in the developing brian and olfactrory bulb, and is expressed in postmitotic migrating and differentiating neurons during embryonic and postnatal development periods. We investigated age-related changes of doublecortin positive cells in the olfactory bulb of aged rat compared with new born rat. MATERIALS AND METHOD: Four months old (control group, n=7) and 24 months old (aged group, n=7) male Fischer 344 rats were used in this study. Olfactory bulbs of the rats were cut into 40 micro m-thick coronal sections and immunostained. We counted the doublecortin positive cells and neurofibrils, and measured the optical density of doublecortin by layer. We compared the results between the aged group and the control group. RESULTS: In the olfactory bulbs of aged group, we observed less doublecortin positive cells, neurofibrils and lower optical density than the control group. Doublecortin is expressed during life in migratory neuroblasts of the olfactory bulb of the rats. This expression is reduced in the aged group and the reduced degree is variable according to the layer. CONCLUSION: Age-related changes of the olfactory bulb are associated with the reduction of postnatal neurogenesis, especially during the migration and differentiaion stages. This changes result in reduction of interneurons of the olfactory bulb, and may be responsible for the decreased olfactory function.

The Effect of Thyrotropin Releasing Hormone on the Somatosensory Evoked Potentials and the Ultrastructure of Myelinated Nerve Fibers in Injuried Spinal Cord

The purpose of this study was to determine the effect of treatment with thyrotropin releasing hormone(TRH) on the somatosensory evoked potentials(SSEPs) and ultrastructures of myelinated nerve fibers in injured spinal cords. Spinal cords of cats were injured expermentally at the second lumbar vertebra level with 20gm-20cm(400gm-cm) impact force using modified Allen's weight drop method. The animals were treated with TRH(2mg/Kg, bolus, then 2mg/Kg/hour, IV, for 4 hours) 1 hour after injury. SSEPs were checked serially in both treated and untreated groups for 24 hours. And the fine strucures of myelinated nerve fibers in the white matters were observed in electronmicroscope before and after the injury in both groups. In treated groups, the inital positive waves were re-elicited 3 hours after injury which was eliminated immediately after injury. Fine structure of the myelinated nerve fibers were changed progressively. With time after injury, the myelinated nerve fibers showed enlarged periaxonal spaces, irregulary contoured axons, and disarray of myelin sheaths. By 4 hours after injury, there appeared marked separation and disrray of myelin sheaths, and mitochondria and neurofibrils in axoplasm showed serve degeneration. The result of this study suggested that TRH has a beneficial effect on the re-elicitation of SSEP's and the preservation of myelinated nerve fibers in the acute stage of spinal cord injury.