Regeneration of sensory hair cells after acoustic trauma

Any loss of cochlear hair cells has been presumed to result in a permanent hearing deficit because the production of these cells normally ceases before birth. However, after acoustic trauma, injured sensory cells in the mature cochlea of the chicken are replaced. New cells appear to be produced by mitosis of supporting cells that survive at the lesion site and do not divide in the absence of trauma. This trauma-induced division of normally postmitotic cells may lead to recovery from profound hearing loss.     

Proliferation of functional hair cells in vivo in the absence of the retinoblastoma protein

In mammals, hair cell loss causes irreversible hearing and balance impairment because hair cells are terminally differentiated and do not regenerate spontaneously. By profiling gene expression in developing mouse vestibular organs, we identified the retinoblastoma protein (pRb) as a candidate regulator of cell cycle exit in hair cells. Differentiated and functional mouse hair cells with a targeted deletion of Rb1 undergo mitosis, divide, and cycle, yet continue to become highly differentiated and functional. Moreover, acute loss of Rb1 in postnatal hair cells caused cell cycle reentry. Manipulation of the pRb pathway may ultimately lead to mammalian hair cell regeneration.     

Noncycling tumor cells: mitogenic response to antilymphocytic serum

After continuous labeling with tritiated thymidine for a period several times the cell generation time, some ELD ascites cells remained unlabeled. Despite continued exposure to tritiated thymidine, unlabeled mitoses appeared promptly after administration of mouse antilymphocytic serum. Immunosuppression released some noncycling G(2) tumor cells into mitosis.     

Plasticity and differentiation of embryonic retinal cells after terminal mitosis

The relation between terminal mitosis and the events that determine the developmental fate of embryonic precursor cells is not well understood. This relation has now been investigated with [3H]thymidine autoradiography to determine the time of cell birth and with a culture system that allows the testing of the developmental potential of cells isolated from the chick embryo retina. Contrary to the situation in vivo, where neuronal differentiation always precedes photoreceptor differentiation, photoreceptor differentiation occurs prematurely and precedes neuronal differentiation when precursor cells are isolated from the retina at early embryonic stages. Thus, cells born by embryonic day 5 (ED-5) give rise predominantly to photoreceptors when isolated for culture on ED-6 but develop mainly as neurons when isolated on ED-8. This suggests that retinal precursor cells retain after terminal mitosis the capacity to develop either as neurons or as photoreceptors. Moreover, photoreceptor differentiation appears to represent a constitutive or "default" pathway that precursor cells follow in the absence of neuron-inducing signals.     

Frequency discrimination following the selective destruction of cochlear inner and outer hair cells

Frequency discrimination was measured behaviorally before and after drug-induced lesions of cochlear hair cells in the cat. Discrimination was unaffected by complete loss of outer hair cells provided that at least 50% of inner hair cells were intact. Thus, inner hair cells are important for frequency discrimination, and they can function normally in this regard without the influence of outer hair cells.     

Blockade of deoxyribonucleic acid synthesis by deuterium oxide

Interference with deoxyribonucleic acid replication need not be a primary mechanism in the blockade of cell division by deuterium oxide, but current hypotheses on the molecular basis of the blockade do suggest that such interference might take place under appropriate conditions. Autoradiographic experiments support the suggestion, for whereas normal sea urchin eggs incorporate H(3)-thymidine into deoxyribonucleic acid from almost the beginning of development, cells immersed in deuterium-enriched media do not. Blockade of mitosis and inhibition of thymidine incorporation are simultaneously relieved when the eggs are returned to normal water.     

DNA synthesis and mitosis in well-differentiated mammalian cardiocytes

Incorporation of [(3)H]thymidine into nuclei of heart cells of 2-day-old rats indicates that neonatal cardiac cells containing well-aligned myofibrils synthesize DNA. In these highly differentiated cells, neither the presence of contractile proteins nor their organization into myofibrils inhibits either DNA synthesis or mitosis.     

Human-mouse somatic cell hybrids with single human chromosome (group E): link with thymidine kinase activity

Mouse somatic cells lacking thymidine kinase were mixed in culture with human diploid cells lacking hypoxanthine guanine phosphoribosyl transferase, and hybrid cells were isolated and maintained in a selective medium containing hypoxanthine, aminopterin, and thymidine. The hybrid cells at the time of isolation had karyotypes consisting predominantly of mouse chromosomes but with one human chromosome, a submetacentric member of group E, apparently giving thymidine kinase to the hybrid cell. However, after long-term propagation in the selective medium this chromosome has been lost, although cells continue to show thymidine kinase activity as demonstrated by the incorporation of (3)H-thy-midine into DNA in the hybrid cell. The hybrid cells have only mouse electro-phoretic variants for glucose-6-phosphate dehydrogenase, lactate dehydrogenase, and malate dehydrogenase, suggesting that the human genetic loci for these enzymes are not represented in the hybrid genome and may be unlinked to that for thymidine kinase.     

On the nature of a defect in cells from individuals with ataxia-telangiectasia

The cells and tissues of patients with ataxia-telangiectasia (A-T), an inherited disease characterized by a high degree of proneness to cancer, are abnormally sensitive to ionizing radiation. Noncycling cultures of normal human and A-T fibroblasts were exposed to x-rays so that the breakage and rejoining of prematurely condensed chromosomes in the G1 phase could be compared. After a dose of 6.0 grays, both cell types had the same initial frequency of breaks and the same rate for rejoining of the breaks, but the fraction of breaks that did not rejoin was five to six times greater for the A-T cells. The results also show that progression of cells into the S phase is not a prerequisite for the increased frequency of chromosome fragments that appear in mitosis after A-T cells are irradiated in the G1 or G0 phase.     

Alternating current delivered into the scala media alters sound pressure at the eardrum

Alternating current delivered into the scala media of the gerbil cochlea modulates the amplitude of a test tone measured near the eardrum. Variations in the electromechanical effect with acoustic stimulus parameters and observed physiological vulnerability suggest that cochlear hair cells are the biophysical origin of the process. Cochlear hair cells have traditionally been thought of as passive receptor cells, but they may play an active role in cochlear micromechanics.     

Eya1-Six1信号在斑马鱼侧线神经丘毛细胞再生过程中的表达

机械感觉毛细胞对于脊椎动物的听力和平衡能力至关重要,低等脊椎动物毛细胞在遭受损伤后具有很强的再生能力。鱼类侧线神经丘毛细胞与内耳毛细胞具有相似的结构、功能、发育和再生过程。我们将受精后5~6 d的斑马鱼仔鱼置于400 μmol/L新霉素溶液中处理1 h破坏神经丘毛细胞。分别对处理后2、4、8、12及24 h的斑马鱼仔鱼进行组织学切片及功能基因eya1和six1b的整体原位杂交。组织学切片结果显示：对照组神经丘毛细胞与支持细胞形态及排布都很规则,毛细胞和支持细胞分别位于上层和下层;处理后2~4 h,上层毛细胞数量显著下降;处理后8~12 h,支持细胞和毛细胞之间界限模糊,部分支持细胞变长,且与基膜脱离;处理后24 h,部分神经丘内毛细胞及支持细胞数量、形态及排布接近对照组水平。整体原位杂交结果显示：eya1和six1b在对照组斑马鱼仔鱼整个神经丘都有表达;处理后4 h内神经丘中央毛细胞中eya1和six1b的表达量显著下降,周围的支持细胞中仍保持一定量的表达;这两个基因的表达量从处理后8 h起逐渐提高,在处理后12~24 h恢复甚至超过对照组。综上结果表明：神经丘毛细胞再生过程中可能有支持细胞的参与,且重启了神经丘毛细胞发育过程中的功能基因eya1和six1b。     

The goldfish ear codes the axis of acoustic particle motion in three dimensions

Auditory and vestibular nerve fibers of the goldfish are strongly directionally sensitive to whole-body acceleration at audio frequencies. The three-dimensional pattern of sensitivity shows that input from a receptor ensemble (hair cells) is essentially equivalent to that expected from a single hair cell having a given three-dimensional orientation of best sensitivity. Fibers from the sacculus, lagena, and utriculus differ with respect to distributions of directional orientation, but are similar in best threshold (less than 1 nanometer, root mean square, at 140 hertz). In combination with other mechanisms for detection of sound pressure, this directionality is a likely basis for directional hearing in fishes, and it could allow the determination of underwater acoustic intensity.     

Cyclic changes in enzyme activity in synchronized mammalian cell cultures

Activity of the enzymes glucose-6-phosphate dehydrogenase and lactate dehydrogenase increases intermittently in synchronized cultures of Chinese hamster cells. During G(1) phase (3 hours after mitosis), midway through S phase (7 hours after mitosis) and again in late S phase (10 hours after mitosis), rapid increases in activity were observed and correlated with a net increase in cell size and total protein. The evidence suggests that this is a general phenomenon which affects a whole population of proteins and may be the expression of an endogenous cellular rhythm.     

Distribution of chromatids at mitosis

The distribution of labeled chromatids at the second mitosis after labeling with tritiated thymidine is random in both Vicia faba (the broad bean) and Potorous tridactylis (the rat kangaroo). This finding is contrary to that predicted by the hypothesis that chromatids containing "grandparent" polynucleotide templates segregate from those containing "parent" templates.     

单细胞测序对绒山羊毛乳头细胞的鉴定

【目的】 基于单细胞测序技术探究绒山羊毛乳头细胞标记基因,优化毛乳头细胞体外鉴定的方法,为研究绒山羊毛囊发生发育提供良好的细胞模型。【方法】 运用Seurat单细胞分析法分析陕北白绒山羊胚胎期60、90、120 d皮肤组织的单细胞测序数据。原始数据经质控、过滤、标准化后,采用UMAP方法进行数据降维与聚类分析。通过对比已报道的毛囊相关标记基因,获得完整绒山羊毛囊细胞类群谱系信息。通过基因差异表达分析,筛选绒山羊毛乳头细胞特异性标记基因。利用免疫荧光试验鉴定标记蛋白在绒山羊皮肤组织中的表达与分布情况,进一步筛选毛乳头区域特异性表达蛋白。体视镜下机械分离完整绒山羊毛囊,采用酶消化法分离绒山羊毛乳头区域并在体外培养至细胞分离,最终通过差速贴壁法纯化细胞。待毛乳头细胞纯度较高时,利用免疫荧光试验验证候选标记蛋白在分离细胞中的表达情况。【结果】 从单细胞水平分析了绒山羊毛囊发生过程中涉及的关键细胞转录信息,成功获得绒山羊皮肤中的17个主要细胞类群信息,鉴定出包括真皮细胞谱系、表皮细胞谱系、毛乳头细胞、毛干细胞、内根鞘细胞等绒山羊皮肤结构关键细胞类群,以及周皮细胞、巨噬细胞、肌肉细胞等其他功能细胞类群。筛选获得毛乳头细胞特异性基因427个,包括SOX2、FGF7、APOD、BMP3、HHIP、HEY2和SPON1等,这些基因在绒山羊毛乳头细胞中的表达丰度远高于其他细胞类型,被认为是毛乳头细胞特异性标记基因。组织免疫荧光试验进一步证明SOX2、FGF7与APOD等蛋白在绒山羊毛乳头区域内特异性表达,可用于皮肤组织中绒山羊毛乳头细胞的定位。此外,本研究在成功分离单根绒山羊次级毛囊的基础上,实现了绒山羊毛乳头区域的贴壁培养,成功观测到大量细胞从毛乳头区域逐步迁移分离的过程。细胞免疫荧光试验结果显示SOX2、FGF7与APOD均在绒山羊毛乳头细胞中表达,且SOX2阳性细胞约占毛乳头细胞总量的76%左右,而FGF7和APOD阳性细胞则占98%以上。结合绒山羊皮肤组织免疫荧光定位结果,SOX2、FGF7与APOD等标记可用于鉴定体外分离培养的绒山羊毛乳头细胞。【结论】 利用单细胞测序技术描述了绒山羊主要皮肤细胞的转录组信息,筛选出毛乳头细胞特异性表达基因。经免疫荧光试验证实,单细胞测序鉴定标记基因的方法简单高效,且具备较高准确率。筛选的SOX2、FGF7与APOD不仅为绒山羊毛乳头细胞体内定位提供了有效的标记,而且为多标记鉴定毛乳头细胞提供可能,更为进一步研究毛囊发育相关基因的功能及调控机制奠定重要基础。     

甘蔗茎尖细胞有丝分裂过程中微管骨架的变化（英文）

In order to understand the microtubule change of monocotyls stem-tip during mitosis,the arrangement,transformation of microtubule array and its relation with chromosome movement during mitosis were studied with freezing microtome,indirect immunofluorescence,DAPI staining and fluorescence microscopy.The results showed that nucleolus was intact when the cortical microtubules formed;cortical microtubules were changed into phramoplast microtubule bands at mitosis prophase.When phramoplast microtubule came into being,nuclear membrane was ruptured and chromosome was arranged at the position of cell plate;subsequently,phramoplast microtubules were changed into phragmoplast microtubules,phramoplast microtubules were shortening and microtubules on the sides of cell plate were increasing gradually,during this course sister chromatid was separated by microtubules at cell plate and tract to the two poles,forming phragmoplast microtubules.Then the nucleolus of two daughter cells formed and separated in the end with the increase of cells numbers.Therefore,cell division orientation could be judged from the arrangement of cell microtubules in different periods in order to understand its growth status.     

甘蔗茎尖细胞有丝分裂过程中微管骨架的变化

笔者拟从微管列阵变化及其参与染色体运动的关系方面探讨甘蔗茎增粗机理,为单子叶植物的微管与染色体相关研究提供一定的例证。     

Prevention of chemotherapy-induced alopecia in rats by CDK inhibitors

Most traditional cytotoxic anticancer agents ablate the rapidly dividing epithelium of the hair follicle and induce alopecia (hair loss). Inhibition of cyclin-dependent kinase 2 (CDK2), a positive regulator of eukaryotic cell cycle progression, may represent a therapeutic strategy for prevention of chemotherapy-induced alopecia (CIA) by arresting the cell cycle and reducing the sensitivity of the epithelium to many cell cycle-active antitumor agents. Potent small-molecule inhibitors of CDK2 were developed using structure-based methods. Topical application of these compounds in a neonatal rat model of CIA reduced hair loss at the site of application in 33 to 50% of the animals. Thus, inhibition of CDK2 represents a potentially useful approach for the prevention of CIA in cancer patients.     

满江红与无藻满江红的超微结构

用显微解剖技术和扫描电子显微镜观察了羽叶满江红、蕨状满江红和小叶满江红以及它们的无藻萍的茎尖、叶腔和腺毛。对蕨状满江红和小叶满江红正在萌发的大孢子果和胚的微形态也作了研讨。在满江红的茎尖或胚即有腺毛发生,未分化的鱼腥藻或厚垣孢子总是有选择地附着于腺毛上。每片叶片至少有两个初生分支腺毛。它们是鱼腥藻由茎尖进入叶腔的桥梁。腺毛除了具有运输的功能外,很可能是蕨体用来吸收和识别共生藻的主要结构。     

氯霉素细胞毒性研究

[目的]了解氯霉素的细胞毒性机理。[方法]用浓度为0.5、1、5、10 mg/L的氯霉素稀释液处理蚕豆根尖,进行氯霉素细胞毒性检测试验,光学显微镜下观察细胞的分裂情况,统计微核数。[结果]氯霉素稀释液处理的蚕豆根尖细胞依然能够进行分裂和增殖。氯霉素培养液中的蚕豆根尖细胞经固定、酸解和染色处理后,在光学显微镜下能观察到微核。氯霉素浓度为0.5、1、5 mg/L时,微核率分别为1.25‰、4.50‰和7.00‰,表现出剂量效应;氯霉素浓度为10 mg/L时,微核率为9.75‰,与蒸馏水对照存在极显著差异(P<0.01)。[结论]氯霉素可能是作为DNA的断裂剂,在细胞有丝分裂时产生作用,微核在细胞间期或有丝分裂中后期形成。