DIFFERENTIATION OF NEUROBLASTOMA CELLS IN CULTURE

1. An elevation of the intracellular level of cyclic AMP in neuroblastoma cells by prostaglandin E₁ by an inhibitor of cyclic AMP phosphodiesterase, or by analogues of cyclic AMP irreversibly induces many differentiated functions which are characteristic of mature neurones. These include formation of long neurites, increase in size of soma and nucleus associated with a rise in total RNA and protein contents, increase in activities of specific neural enzymes, loss of malignancy, increase in sensitivity of adenylate cyclase to catecholamines and blockade of cells in G₁-stage of the cell cycle. 2. Other agents, including serum-free medium, X-irradiation, 6-thioguanine, cytosine arabinoside, methotrexate, 5-bromodeoxyuridine, nerve growth factor, glial extract and hypertonic medium can induce some of the differentiated functions which are induced by high intracellular cyclic AMP. 3. Morphological differentiation and differentiated biochemical functions can each be expressed in the absence of the other. 4. Many of the responses of normal embryonic nerve cells to cyclic AMP are similar to those of neuroblastoma cells. 5. A working hypothesis for the malignancy of nerve cells has been proposed. This states that an abnormal regulation of cyclic AMP phosphodiesterase activity which allows the expression of high amounts of this enzyme in neuroblastoma cells, may be one of the early lesions during a malignant transformation of nerve cells. 6. A new experimental therapeutic model for the treatment of neuroblastoma is proposed. This involves the administration of sodium butyrate followed by the injection of l -dihydroxyphenylalanine (l-dopa) and prostaglandin E₁ in the presence of cyclic AMP phosphodiesterase inhibitor. 7. Recent studies have elucidated the control mechanisms of some differentiated functions in neuroblastoma cells. Cyclic AMP may become an important biological tool to probe the regulation and expression of many other differentiated functions in these cells. In addition to neuroblastoma cells, other neuronal culture systems are now available for investigating the problems of differentiation and maturation in nerve cells.     

FACTORS CONTROLLING DEVELOPMENT OF CHICK EMBRYO LIVER CELLS DURING ORGAN CULTURE

The 5 day chick embryo liver cell still lacks many of the ultrastructural features of the adult liver cell. During organ culture on rafts over Eagle's medium, it develops electron-opaque mitochondria with granules, biliary microvilli, and compact Golgi complexes containing what appears to be secretory material. Rough ER proliferates and free ribosomes become bound to membrane. Thus, the 5 day cell, exposed only to simple nutrients (glucose, amino acids, vitamins) develops the general appearance of the adult liver cell except for the continued absence of smooth ER and glycogen. The significance of this incomplete differentiation and the factors controlling development are discussed in the light of accompanying metabolic changes.     

CHANGES IN CELL SURFACE MORPHOLOGY DURING DIFFERENTIATION OF MICROMERE- AND MESOMERE-DERIVED CELLS OF THE SEA URCHIN EMBRYO

Micromeres and mesomeres isolated from 16-cell embryos of the sea urchin, Strongylocentrotus intermedius , were cultured in vitro , and changes in the cells surface architecture during the differentiation of the micromere- and mesomere-derived cells were observed using scanning electron microscopy. Two types of the distribution of the surface microvilli were observed in both blastomere-derived cell masses. One type showed a uniform distribution of the microvilli and the other type showed an uneven one. Though many microvilli were observed in most of both mesomere and micromere-derived cells at the 64-cell stage and the early blastula stage (16 hr after the 16-cell stage at 6°C) respectively, the microvilli decreased in number at the later stages in both blastomere-derived cell masses as compared with the 64-cell stage and the early blastula stage respectively. Rapid disappearance of the surface microvilli was observed in the micromere-derived cells in contrast with the mesomere-derived cells which still had many microvilli even at the midmesenchyme stage.     

TRANSFER RNA AND THE REGULATION OF PROTEIN SYNTHESIS IN RAT CEREBRAL CORTEX DURING NEURAL DEVELOPMENT

Protein synthesis was measured in ribosomal systems derived from the cerebral cortex of 5-and 35-day-old rats. Under optimal conditions incorporation of radioactive leucine per mg ribosomal protein was four times higher with ribosomes from the younger animals than with ribosomes from the 35-day-old rats. This suggests that a decrease in the rate of protein synthesis occurs during neural development. Both ribosomes and the pH enzyme fraction from the cerebral cortex of 35-day-old rats had lower activities than preparations from the younger rats. Cerebral cortical ribosomes from 35-day-old animals had a lower polyribosome content than similar preparations from 5-day-old rats. A three-fold higher requirement for the pH 5 enzyme fraction was observed with the ribosomal system from 5-day-old rats, an observation which correlated with the yields of pH 5 enzyme and ribosomal protein from the younger tissue. The nature of the changes in the composition of the pH 5 enzyme fraction was investigated. Methylated albumin kiesselguhr (MAK) and Sephadex G-75 column chromatography showed that RNA from the pH 5 enzyme fraction was heterogeneous, containing tRNA, rRNA, and a small molecular weight RNA. This latter RNA, perhaps a degradation product of rRNA, comprised the greatest portion of RNA from the pH 5 enzyme fraction of cerebral cortex. The data obtained with MAK chromatography were used to estimate the total tRNA content of the cerebral cortex, with no age-related differences being observed. Since evidence of RNA degradation was seen, tRNA was also isolated by phenol extraction of whole cerebral cortex in the presence of bentonite. Purification of tRNA by NaCl and isopropanol fractionation gave preparations with no detectable rRNA or small molecular weight RNA. With this purification method, the tRNA yield was greater than estimated by the MAK method, demonstrating that losses of tRNA occurred during the cell fractionation steps. With the purification method 1.6 times more tRNA was obtained from the cerebral cortex of 5-day-old animals than from the older tissue. This higher level of tRNA in the younger, more active tissue appeared to involve all tRNA species, since in vitro aminoacyiation studies revealed nearly identical acceptance values for 18 individual amino acids. These results suggest that the rate of protein synthesis in cerebral cortex is regulated in part by the total amount of tRNA present to translate the higher level of polysome-bound mRNA.     

肌细胞分化基因与大鼠肝再生的相关性分析

肌细胞是组织器官的重要组成部分。为在基因转录水平了解肌细胞分化相关基因在大鼠肝再生中的作用,本文用搜集网站资料和查阅相关论文等方法获得上述基因．用Rat Genome2302．0芯片检测它们在大鼠肝再生（liver regeneration,LR）中表达情况,用比较真、假手术基因表达的差异性方法确定肝再生相关基因。初步证实上述基因中52个基因与肝再生相关。根据肝再生中基因表达的时间相关性将上述基因聚合为0．5-1h;2—12h;16、30、42、96h;18—24、36、48—60h;66—72、120-168h等5类,表达上调和下调的基因数分别为8和10,24和8,21和24,53和64,28和36。它们表达的相似性分为均上调、上调占优势、均下调、下调占优势、上调和下调次数相近等5类,涉及15、10、17、7和3个基因,共上调表达143次、下调136次,分为8类表达方式。表明肌细胞分化相关基因表达变化多样和复杂。根据上述结果推测,肝再生中成肌细胞和平滑肌细胞分化增强：骨骼肌和心肌细胞分化相关基因参与肝再生的生理生化活动。     

DIFFERENTIATION OF RAT LENS EPITHELIAL CELLS IN TISSUE CULTURE (III) FUNCTIONS IN VITRO OF A TRANSFORMED RAT LENS EPITHELIAL CELL LINE

Epithelial cells isolated from one-day-old rat lens were neoplastically transformed using Rous Sarcoma Virus (Schmidt-Ruppin-D strain) and have been in continuous culture for over 30 months. This cell line displays some of the characteristics of lens epithelial cells, but can be shown to represent a permanent cell line in that it has been transferred more than 50 times and is continuing to grow, while primary lens cell cultures have never survived beyond 8 weeks. The infecting viral genome can be rescued from the cell line upon fusion with uninfected chick embryo cells. It is anticipated that this newly established cell line, designated RLE-R, will be useful in studies on cellular differentiation.     

ULTRASTRUCTURAL CHANGES IN CELLS OF PEA EMBRYO RADICLES DURING GERMINATION

Radicles (1 mm long) of pea embryo axes, excised from dormant seeds and from seeds soaked for 80 min, 8, 12, and 48 hr, were fixed in glutaraldehyde and postfixed in OsO₄. The nucleus was only slightly changed by 48 hr soaking, but cytoplasmic organelles underwent developmental changes. There was proliferation of endoplasmic reticulum, the appearance of dictyosomes, and an inward migration of lipid bodies. Most of these changes were observed within 8 hr after soaking started. Plastids, mitochondria, protein bodies, and protein crystalline bodies were also identified and their developmental changes were followed.     

ULTRASTRUCTURAL CHANGES IN EMBRYONIC ECTODERMAL CELLS OF THE NEURULATING RAT EMBRYO

Embryonic ectodermal cells of rat embryos were examined by light and electron microscopy during the early stage of neurulation. Before the onset of neurulation (day 9–6 hr embryos), the cells underwent certain characteristic ultrastructural changes; that is, apical cytoplasmic protrusions and free spherules appeared, numerous vacuoles were formed in the cytoplasm, mitochondria showed ballooning, and the endoplasmic reticulum became dilated. The amniotic cells derived from the embryonic ectoderm exhibited the same ultrastructural changes, but those from the extraembryonic mesoderm did not. Embryonic mesodermal cells and neuroectodermal cells also did not show these changes. In the middle stage of neurulation (day 9–12 hr embryos), the embryonic ectodermal cells and the amniotic cells derived from the embryonic ectoderm assumed a flat squamous shape. None of the ultrastructural changes observed in day 9–6 hr embryos were noted in these cells. The functional significance of the production of apical cytoplasmic protrusions and free spherules in the embryonic ectodermal cells and amniotic cells is discussed in relation to similar phenomena reported to occur in other cell types.     

DIFFERENTIATION OF A PRIMARY CHEMICALLY INDUCED RAT NEPHROBLASTOMA IN ORGAN CULTURE

The differentiation in organ culture of a rat nephroblastoma is compared with differentiation of normal rat metanephric tissue under the same conditions. The nephroblastoma arose in a 19 week old female Fischer F344 rat given a single intraperitoneal injection of 4.0 μmole methyl(methoxymethy1)nitrosamine (DMN-OMe)/g body weight at one day of age. The tumor consisted almost entirely of spindle cells although a few well-differentiated tubules were scattered throughout the tumor mass. No primitive tubules were seen, but focal aggregates of tumor cells suggestive of nascent epithelial differentiation were frequent. Fragments of the nephroblastoma were cultured on gelfoam sponge in Williams Medium E supplemented with hydrocortisone, insulin, and fetal bovine serum. Within one day extensive tubulogenesis was observed. High mitotic activity resulted in a steady increase in the size of cultured explants over a period of 6 days. By day six, differentiating tubules filled the explant tissue. Cultured fragments were nearly indistinguishable histologically from normal F344 rat fetal kidney explanted to organ culture on day 15 of gestation and grown in vitro for the same period.     

不同活力玉米种子胚萌发过程中蛋白质的变化

从不同人工老化处理中筛选出３组分别代表不同活力的玉米种子。萌发期间,中、低活力种子胚蛋白的降解比高活力对照种子慢,萌发前期胚蛋白合成能力也较低。吸胀２４ｈ,不同活力胚的蛋白合成能力差异显著,可以作为衡量种子活力的指标。     

大鼠原生殖细胞培养和分化的研究

研究大鼠胚胎原生殖细胞（primordial germ cells,PGCs)的培养及分化,取受精后11-12.5天大鼠PGCs进行原代培养,光、电镜观察PGCs及其分化细胞的微细结构,碱性磷酸酶染色检测细胞的分化程度,结果显然显示大鼠PGCs大而圆,散在分布,或多个聚集成团,胞质中含有椭圆形的线粒体和丰富的核糖体,在鼠胚成纤维细胞饲养层存在的情况下,PGCs保持未分化状态,碱性磷酸酶反应呈强阳性,在缺乏饲养层的条件下PGCs很快分化,形态不规则,有伪足,碱性磷酸酶反应减弱,进一步分化可形成具有细长突起的神经元样细胞,胞质中含有细丝束的表皮细胞,可见节律性跳动的心肌细胞,具有分泌颗粒的分泌细胞及似血管,心脏形状的管腔结构等,由PGCs分化来的细胞碱性磷酸酶反应均呈阴性,结果表明大鼠PGCs能够分化形成三个胚层的衍生物,生殖嵴来源的PGCsp是一种具有发育全能性的胚胎多能干细胞,本研究同时证明鼠胚饲养层能抑制大鼠PGCs的分化。     

脂肪细胞分化相关基因在大鼠再生肝中表达变化

肝脏由多种细胞构成,肝再生与细胞分化密切相关,细胞分化受基因转录水平调控。为在基因转录水平了解脂肪细胞分化基因在大鼠肝再生中作用,本文用搜集网站资料和查阅相关论文等方法获得上述基因,用Rat Genome2302.0芯片检测它们在大鼠肝再生(liver regeneration,LR)中表达情况,将三次检验结果相同或相似、在肝再生中表达变化2倍以上、真手术组和假手术组相比差异显著的基因视为肝再生相关基因。初步证实上述基因中75个基因与肝再生相关。肝再生启动(PH后0.5-4h)、G0/G1过渡(PH后4-6h)、细胞增殖(PH后6-66h)、细胞分化和组织结构功能重建(PH后72-168h)等四个阶段起始表达的基因数为44、13、30和1;基因的总表达次数为88、58、302和90。表明相关基因主要在肝再生启动阶段起始表达,在不同阶段发挥作用。它们共表达上调313次、下调167次,分为43种表达方式。表明肝再生中脂肪细胞发生和分化相关基因活动多样和复杂。根据本文研究结果推测,上述基因不仅调节脂肪细胞分化,而且参与肝再生的生理生化活动。     

THE DIFFERENTIATING ABILITY OF RAT LENS EPITHELIAL CELLS IN CELL CULTURE

Dissociated cells of lens epithelia of adult rats were monolayerly cultured in vitro. After about 15–20 days' period of active cell growth, such characteristic structures that correspond to "lentoid bodies" described previously in chick cultures were formed. These structures consisted of elongated cells, ultrastructural profile of which was similar with lens fiber. The presence of gamma-crystallin, a marker molecule specific to mature lens fiber, was confirmed in these elongated cells by means of fluorescent antibody technique. The differentiation of lens fiber in vitro was also recognized in clones originating from single lens epithelial cells cultured at very low cell density.     

兔输卵管上皮细胞解除大鼠早期胚胎发育阻滞的研究

本研究利用兔输卵管上皮细胞(ROEc), 与异种动物大鼠的受精卵共培养,结果大量出现突破2细胞发育阻滞的现象。体外受精卵和体内受精卵的2细胞发育阻滞突破率分别为62%和73%;利用ROEC 条件培养液培养大鼠的体外受精卵,2细胞发育阻滞的突破率达68%,且能顺利发育至桑椹胚和囊胚。将ROEC直接培养在含~(35)S-甲硫氨酸的CZB 培养液中,经SDS-聚丙烯酰胺凝胶电泳及放射自显影,发现在该条件培液中出现了分子量分别为135Kd,68Kd,55Kd,51Kd 和44Kd 由ROEC 分泌的多肽,其中68 Kd 区带最显著,而135 Kd区带非常弱。用(125)~I-酰化剂标记示踪发现,与ROEC 共培养24 h 的大鼠胚胎透明带上含有68Kd 蛋白,并发现55 Kd 蛋白与透明带结合的痕迹。这些蛋白很可能就是胚胎发育调控由母型向合子型过渡并突破早期发育阻滞的关键因子,在功能上似无种属特异性。     

CHANGES IN GLUCOSE OXIDATION DURING GROWTH OF EMBRYONIC HEART CELLS IN CULTURE

A rapid and convenient method has been utilized to investigate glucose oxidation during growth of chick embryo heart cells in tissue culture. Primary isolates of chick embryo heart cells showed exponential growth when plated at low densities and exhibited density-inhibited growth as cultures became confluent. The density-dependent growth inhibition of chick embryo heart cells is associated with a marked decrease in the specific activity of glucose oxidation to CO₂. This decrease in glucose oxidation was observed as density increased as either a function of time in culture or as related to initial plating density. The decrease in ¹⁴CO₂ production associated with density-dependent inhibition of growth is due to a marked decrease in activity of the pentose phosphate pathway.     

CGRP和NGF对局灶性脑缺血再灌注大鼠海马HSP70蛋白表达的影响

目的探讨外源性降钙素基因相关肽(CGRP)和神经生长因子(NGF)对局灶性脑缺血再灌注大鼠海马热休克蛋白70(HSP70)表达的影响.方法用线栓法制备大鼠大脑中动脉阻塞(MCAO)模型,应用免疫组化和显微图像分析方法检测局灶性脑缺血再灌注大鼠海马HSP70的表达.结果假手术组海马未见HSP70阳性细胞,缺血再灌注组海马HSP70阳性细胞数增多.分别注射CGRP或NGF后海马区HSP70阳性细胞平均光密度值明显高于缺血再灌注组(P<0.01),二者合用时平均光密度值较比单独应用高(P<0.05).结论CGRP和NGF上调缺血神经元HSP70的表达,二者合用作用更强,对缺血神经元恢复有促进作用.