Conversion of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) by ten-eleven translocation (TET) family proteins leads to the accumulation of 5hmC in the central nervous system; however, the role of 5hmC in the postnatal brain and how its levels and target genes are regulated by TETs remain elusive. We have generated mice that lack all three Tet genes specifically in postnatal excitatory neurons. These mice exhibit significantly reduced 5hmC levels, altered dendritic spine morphology within brain regions crucial for cognition, and substantially impaired spatial and associative memories. Transcriptome profiling combined with epigenetic mapping reveals that a subset of genes, which display changes in both 5hmC/5mC levels and expression patterns, are involved in synapse-related functions. Our findings provide insight into the role of postnatally accumulated 5hmC in the mouse brain and underscore the impact of 5hmC modification on the expression of genes essential for synapse development and function.
Animals ; Brain/growth & development* ; 5-Methylcytosine/metabolism* ; Mice ; Synapses/genetics* ; Proto-Oncogene Proteins/metabolism* ; DNA-Binding Proteins/metabolism* ; Dioxygenases/metabolism* ; Cognition/physiology* ; Gene Expression ; Mixed Function Oxygenases/metabolism* ; Epigenesis, Genetic ; Mice, Knockout ; Mice, Inbred C57BL

Objective To reveal the fibrillar network in vitreous and the effect of plasmin on this network. Methods 20 vitreous gels of freshly slaughtered pigs were divided into 2 groups, the gels in first group were digested by 3 U plasmin (3 U/ml) at 37℃ for 24 hours respectively, the second group received the same PBS as control. After digestion, gels were fixed in neutral buffered formalin solution. Samples from vitreous base, cortex and the central region were observed by the technique of freeze etching electron microscopy. Results In vitreous collagen fibril network was in a three-dimensional array, collagen fibril density showed marked differences, central vitreous had the sparse fibril density, the cortex denser and the basal vitreous densest. After digestion by plasmin, the collagen fibrillar network was destructed. Conclusion Collagen fibrils in vitreous present spatial arrangement regularly, plasmin can lead to destruction of the fibrillar network.

This paper presents the observation on the structure,quantity,distribution andmembrane characteristics of mitochondria in spermatogonia,spermatocyte,spermatidand mature sperm during spermatogenesis.They were examined by electron micro-scope (ultrathin section and freeze fracture).Conclusions obtained are as follows:1.There exists regular changes for the proliferation,development and distribu-tion of mitochondria.(a)Quantity of mitochondria:total number of mitochondriain spermatogonia are 80-120 for one cell.They increase to 400-500 in primary sper-matocyte.Spermatid has 200-300 mitochondria.(b)Distribution of mitochondria.Mitochondria in spermatogonia distribute randomly.There are several groups ofmitochondria in spermatocyte.During spermatogenesis mitochondria moved fromhead to back side.In Golgi phase and cap phase spermatid,mitochondria situatedunder the plasm membrane,in mature sperm they arrange regularly outside the densefiber of middle piece of tail.(c)Structure and development:Mitochondria inspermatogonia are round and oval.Cristae arrange parallelly.At spermatocyte stagemitochondria are proliferated by dividing itself.Newly formed mitochondria haveno cristae.In mature sperm mitochondria developed well,but arrangement ofcristae is not regular.2.Membrane of mitoehondria.There are three laminar structure for mitochon-drial membrane.It is thinner than plasm membrane.Protein particles in outermembrane are more than inner membrane.There are a few protein particles in cristae.3.The changes of mitochondria have close relationship with spermatogenesis.(a)Mitochondria proliferate itself rapidly in spermatocyte to match with enlarge-ment of cellular size and content:(b)Mitochondria situated near the Golgi complexin Golgi phase spermatid,after cap formation they moved to tail side to support thetail formation.(c)In mature sperm mitochondria arranged regularly in middlepiece,so sperm can swim quickly.

The fine ultrastructure and localization of acid phosphatase in cell ultrastructuralevel of a HGPRT-human promyelocytic leukemia cell mutant(HL-60-AR)arestudied by scanning electron microscopy,transmission electron microscopy,freezeetching,and electron microscopic cytochemistry techniques.The results of theobservation show that the ultrastructural characteristics of HL-60-AR cells aresimilar to that of HL-60 cells.There are microvilli and ridges over cell surface.Thecells have large nucleus with prominent nucleoli,and numerous nuclear pores.Thereare less developed Golgi complex,expanded rough endoplasmic reticulum andabundant polyribosomes.After treatment with retinoic acid(RA)at 10~(-6) mol/L for 5days,HL-60-AR cells differentiate along myeloid pathway and have a decreasednucleocytoplasmic ratio accompanied with nuclear condensation and segmention.A (?)ignificant increase of specific granules is demonstrated.Microvilli of the cellsdisappear,surface features of the treated cells become more irregular and largeprotrusion and blunt pseudopodia appear.Increase of acid phosphatase content localizedon azurophilic granules(lysosomes)and Golgi complex is showed.The application offour kinds of electron microscopic techniques might provide the best way foridentifying cell ultrastructure.