| Objective:Cerebral cortex is the most important part of brain, and is the material basis of higher nervous activity. The highest centers of various functional activities center have corresponding positions in the cerebral cortex, forming important centers. The large and middle pyramidal neurons, mainly distributed in the5th layer of cerebral cortex (internal pyramidal layer), are the main projection neurons in human cerebral cortex, and their function is very important.Currently, the research on pyramidal neurons of cerebral cortex mainly focuses on rats, goats, otter and other animals. Data of the human cerebral cortex pyramidal neurons is rarely reported. In this paper, we will study the cell body area, basal dendric length, apical dendric length, basal dendric nodes and apical dendric nodes of pyramidal neurons by rapid Golgi staining and Neurolucida software technology, for exploring the developmental patterns of pyramidal cells of cerebral cortex in human fetus.Methods:Five specimens were legally collected. The gestational age of specimens was19W,20W,26W,35W,38W respectively. The samples of cerebral cortex were taken and fixed by mixture of solution A and solution B (1:1). The mixed solutions were changed after one day, and they were preserved for14days under common temperature, then the mixed solutions were changed into solution C at4℃in the fridge. After3days, they were cut by freezing microtome under-22℃(100um). After drying naturally for5days away from light under common temperature, the sections were stained by rapid GolgiStain. The staining protocol contains:1. rinsed by purified water for2times,2min/time;2. tinctured by mixed solution (Golgi solution D, solution E and purified water,1:1:2) once; 3. rinsed by purified water for2times,4min/time;4. dehydrated by gradient alcohol (one time by50%alcohol,75%alcohol,95%alcohol,4min/time; four times by100%alcohol,4min/time);5. three times by100%xylene solution4min/time;6. mounted by neutral and transparent resin;7. dry at common temperature away from light film for a week.After staining, the sections were observed by Neurolucida microscope. Every section was observed in the same position. The neurons were selected under the standardization:1. stained clearly and completely;2. relatively independence, didn’t overlap with other neurons;3. the branches were not cut off. Neurolucida software was used in tracing and describing for analyzing the influential factors of morphological development, including cell body circumference, cell body area, dendric length, dendric nodes and spines density.Data were input and stored in SPSS version15.0for Windows. Measurement data were represented as mean±standard deviation (SD) and performed statistical analysis by using student t-test, and p value<0.05was considered statistical significant.Results：1.The cell body area of pyramidal neurons of human fetusThe cell body areas of pyramidal neurons were105.1±32.4μm2(19W),188.8±7.7μm2(20W),206.9±28.9(26W),237.5±41.3(35W),357.9±65.1(38W) respectively. The cell body areas of19W was lower than20W(P<0.05). The cell body areas of19W and20W were lower than26W,35W and38W, with statistical significant (P<0.05). The cell body area of26w was lower than35w(P<0.05).the cell body area of26w was lower than38W (P<0.05). The cell body area of35W was lower than38W (P<0.05).2. Dendric length and dendric nodes of human cerebral cortex pyramidal neuronsThe basal dendric length and apical dendric length of19W were lower than20W,26W,35W and38W, with statistical significant (P<0.05). The basal dendric length and apical dendric length of20W were lower than26W,35W and38W (P<0.05). The basal dendric length and apical dendric length of26W were lower than35W and38W, with statistical significant (P<0.05). The basal dendric length and apical dendric length of35W were lower than38W, with statistical significant (P<0.05). The basal dendric length of19W,20W,26W,35W and38W were lower than apical dendric length in the same period, with statistical significant (P<0.05).The basal dendric nodes and apical dendric nodes of19W were lower than20W,26W,35W and38W, with statistical significant (P<0.05). The basal dendric nodes and apical dendric nodes of20W were lower than26W,35W and38W, with statistical significant (P<0.05). The basal dendric nodes and apical dendric nodes of26W were lower than35W and38W, with statistical significant (P<0.05). The basal dendric nodes of35W were lower than38W, with statistical significant (P<0.05). There were no difference in apical dendric nodes between35W and38W, without statistical significant (P>0.05). The basal dendric nodes of19W,20W,26W,35W and38W were lower than apical dendric nodes in the same period, with statistical significant (P<0.05).3. Morphology of human cerebral cortex pyramidal neuronsThe morphology of pyramidal neurons of19W,20W,26W,35W,38W had conical shape and pyramidal shape. With the gestational age increased, the cell bodies were transformed from conical shape into pyramidal shape gradually, the cell body was enlarged, the base of cell body became broaden, the basal dendrite and apical dendrite were become thickening and longer, and the dendric spines density was increased gradually.Conclusions:With development of brain of human fetus, the cell body areas, apical dendric length, basal dendric length, apical dendric nodes, and basal dendric nodes of cerebral cortex pyramidal neurons were increased gradually. The pyramidal cell bodies grew faster relatively from35W to38W. The apical dendric length, basal dendric length, apical dendric nodes, and basal dendric nodes of pyramid cells in cerebral cortex grew faster from26W to35W, this period may be a key time of dendric development in human fetus. |
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