BEHAVIOR OF NUCLEOLI AND CONTRACTING NUCLEOLAR VACUOLES IN TOBACCO CELLS GROWING IN MICROCULTURE

The ability to observe for extended periods of time individual tobacco cells growing in microculture has made it possible to describe the behavior of their nucleoli and contracting nucleolar vacuoles. Nucleoli typically disappeared in prophase and reappeared in telophase. If several nucleoli were present in telophase they generally fused to form only one or two during interphase. In one instance a nucleolus was seen to separate into two nucleoli prior to disappearance in late prophase. In aging and senescent cells the number of nucleoli or bodies similar to normal nucleoli often increased, and occasionally fragmentation of nucleoli was noted prior to death of cells. Budding of solid material from the nucleolus was also observed. The amount of nucleolar material decreased rapidly prior to death of tobacco cells. Nucleolar vacuoles were found to be a general and consistent component of tobacco cells in microculture. Nucleolar vacuoles typically formed and contracted repeatedly in interphase nuclei and apparently released a fluid material into the nucleus. Associated with the contraction of the nucleolar vacuoles was a corresponding decrease in diameter of the nucleolus. Nucleolar vacuoles were observed to occur in about 70% of the actively growing cells examined, whereas they were present in only 33% of the senescent or weakened cells. These data indicate a relationship between nucleolar vacuoles and the morphogenic status of the cells. Since it has been shown by others that the nucleolus is an active site of RNA metabolism, it is suggested that the contracting nucleolar vacuoles may be involved in the controlled release of a soluble product associated with RNA metabolism.     

DEVELOPMENT OF VACUOLES AND LIPID BODIES IN APICAL MERISTEMS OF PINUS BANKSIANA

Shoot apical meristems of jack pine were examined weekly during the first 8 weeks post-germination with light and electron microscopy. Most of the storage lipids were utilized by the end of the 2nd week. A few lipid bodies, possibly high in phospholipid content, remained in the apical initials and central mother cells and, during the 3rd week, gave rise to vacuoles via lamellar or myelin-like structures which were first seen on their periphery. The inter-lamellar spaces enlarged and eventually a vacuole was formed. At 5 weeks, elongate and spherical osmiophilic inclusions, presumably lipid, were found in the endoplasmic reticulum. Lipid bodies, visible with light microscopy, began to accumulate in the apical initials and central mother cells in the 6th week.     

莲子叶叶肉细胞液泡的类型,来源与发育

莲(Nelumbo nucifera Gaertn)子叶发育期间叶肉细胞液泡系变化巨大。发育阶段Ⅰ时,液泡系为具一些单个小液泡的分生细胞型。1—2天后,进入发育阶段Ⅱ,这时中央大液泡形成,液泡系转变为分化细胞型。细胞质和液泡中出现大量小液泡。新液泡的来源和发育是多样的:可由(1)核外膜起泡、断落、扩大形成;(2)高尔基体端部膨大、断落、扩大形成;(3)管状粗糙型内质网任意部位出芽或端部膨大,脱掉核糖体,断落、变形形成;(4)质膜内陷,吞并部分细胞质或营养液形成;(5)中央液泡被原生质丝分割等方式形成。在发育阶段Ⅱ和Ⅲ期间新生液泡大分小合,形成许多平均直径为0.4—1.2μm,形态各异的液泡群。它们各自发育成溶酶体、圆球体、微体、壁旁体、自体吞噬泡和胞饮液泡等。在后继发育中,一些液泡转变为蛋白体和脂肪体。本章论证了莲子叶的液泡系具有同双子叶植物子叶液泡系相似的结构与功能。     

植物细胞培养—分离耦合过程研究进展

本文评述了近10年来植物细胞培养-分离耦合过程的研究及应用,就如何深入开展植物细胞培养-分离耦合过程的研究提出了几点建议。     

ULTRASTRUCTURAL STUDIES PLASMA MEMBRANE RELATED SECONDARY VACUOLES IN CULTURED CELLS

The plasma membrane of cultured cells of several plant species was observed to possess invaginations, or secondary vacuoles, of variable size in the adjacent cytoplasm. These structures, which occurred in cells at different phases in vacuolation, were very numerous in thin sections of some cells but fewer in others. In vacuolated cells enlarged secondary vacuoles protrude into the primary vacuole but are delimited from the tonoplast by an intermembrane zone of variable width. The plasma membrane at the orifice of an invagination may fuse and detach the secondary vacuole from the membrane to form in the cytoplasm a structure bounded by a single membrane. Complex accumulations of membranes consisting of spherical, tubular, and laminar structures, possibly containing cytoplasm, may develop within secondary vacuoles. Contents of many of these vacuoles arise from folds along its limiting membrane which pinch off into the interior of the secondary vacuole. A fibrous substance, possibly derived from the wall, is present in some secondary vacuoles. Observed folding of the plasma membrane and measurements of membrane width of various organelles and cytomembranes support an interpretation that endocytosis occurs in cultured cells.     

鱼腥藻PCC7120细胞液泡的初步研究

从保存３个月以上的老化培养物中直接检查到游离液泡。液泡为标准圆球状,完全透明,大小相差极为悬殊,多数大型液泡吞噬了数个衰老藻细胞。采用低渗酶解,渗透冲击,低渗酶解和渗透冲击相结合从培养３个月以上,２个月,１个月,１８ｄ,１０ｄ及２ｄ的藻丝细胞都分离到液泡。液泡略大于细胞,泡内无吞噬物。培养３ｄ的藻丝有１５％的细胞分离到液泡。其他多种蓝藻也分离到同样的液泡。     

一种新型的植物细胞结晶

高山芹Coelopleurum saxatile (Turcz.)Drude为大型多年生草本植物,茎粗而直立,不分枝,叶三回三出状羽裂。与苔藓植物混生于长白山高山冻原带的林缘处。其活体植物细胞内含有特殊类型的结晶,其化学性质属于草酸钙。因为这种结晶的形状不同于已报道过的任何一种结晶,因此,提出一种新型的细胞结晶——羽毛状结晶。     

ACCUMULATION OF SALT AND PERMEABILITY IN PLANT CELLS

1. Comparisons are made of concentrations of K and Br in exudates of barley roots and in expressed sap from roots, under conditions favorable for aerobic metabolism. Both methods lead to the same general viewpoint concerning metabolically governed transport of solutes by living plant cells. 2. Cyanide in low concentration prevented salt accumulation by barley roots. Methylene blue, without decrease of CO₂ production by roots, destroyed power of salt accumulation. 3. K and Br ions entered roots to only a slight extent under an anaerobic condition, even with an inward gradient of ionic concentration. 4. Lactate or alcohol, under aerobic conditions, did not prevent rapid accumulation of salt by root cells. 5. Experiments on fluids obtained by suction from tomato roots gave evidence of loss of salt-accumulating power under the influence of N₂ gas or CO₂ gas, together with probable effects on cell permeability. 6. Several experiments on Nitella cells in which radioactive isotopes were used are reported. Bromide gradually moved into vacuolar sap until the concentration appeared to exceed that of the protoplasm, on the basis of the results of the several types of experiments. Accumulation of salt in the vacuole did not occur anaerobically. 7. Some views of interrelations of permeability, salt accumulation, and metabolism are suggested for further discussion.     

DEVELOPMENT OF JUNCTIONAL COMPLEX IN CULTURED CELLS

The development of specialized intercellular junctions in cultured cells was studied ultrastructurally. MDCK cells, derived from dog kidney, were fixed in situ at proper times after replating, and the sections were cut perpendicular to the plane of the monolayer. In three or four days, the apposition of cell membranes and condensation of extracellular flocculent material were observed between the neighboring cells, and such were regarded as the early signs of desmosome formation. In many cases, a desmosome was formed first, and the formation of a tight junction followed on the apical (medium facing) side. Finally, all intercellular spaces were closed by a junctional complex at the apical edge. In the complex, a tight junction, (intermediate junction) and desmosome(s) succeeded each other in a medium-substratum direction in all cases. In glutaraldehyde-O^sO⁴ fixed specimens, the intermediate dense line in the desmosome was ascertained from the infant stage of development, while in O^sO⁴ fixed material, the structure was obscure throughout the observation but side-arm-like projections were more prominent.     

植物细胞中间纤维角蛋白性质的分析

角蛋白是植物细胞中间纤维的主要成分。应用选择性抽提和生物化学技术,分离纯化了豌豆根尖细胞58-、52 kD、白菜子叶52kD和胡萝卜悬浮细胞64kD角蛋白,测定了它们的氨基酸组成,结果表明上述角蛋白与动物细胞中间纤维角蛋白的氨基酸组成有较大的相似性。比较了动、植物细胞角蛋白的肽谱,结果显示它们之间存在较大的差异,但是植物细胞间角蛋白的肽谱比较一致,这提示它们属于同一蛋白家族,为植物中间纤维及其角蛋白的存在提供了新的论据。     

LOCALIZATION OF ACID PHOSPHATASE IN LIPOFUSCIN GRANULES AND POSSIBLE AUTOPHAGIC VACUOLES IN INTERSTITIAL CELLS OF THE GUINEA PIG TESTIS

The intracellular localization of acid phosphatase in guinea pig testicular interstitial cells was investigated by incubating nonfrozen thick sections of glutaraldehyde-perfused testis in a modified Gomori medium and preparing the tissue for electron microscopy. Lipofuscin pigment granules in these cells contain dense pigment, granular matrix, and often a lipid droplet. Reaction product is seen in the matrix of the pigment granules, and they may therefore be called residual bodies. At least some of the dense pigment appears to be derived from myelin figures and membrane whorls, since suitable intermediates can be seen. Lipid droplets found free in the cytoplasm are another possible source of pigment. In both cases the chemical mechanism is presumed to be autoxidation of unsaturated lipid. Acid phosphatase is present in the inner cisterna of Golgi elements. Enzyme activity also appears in possible autophagic vacuoles bounded by double membranes; the reaction product lies between the membranes. Consideration of the enzyme as a tracer suggests that the autophagic vacuoles are derived from the Golgi complex. Possible stages in the formation of these vacuoles by the inner Golgi cisternae are observed.     

A COMPARISON OF PERMEABILITY IN PLANT AND ANIMAL CELLS

Quantitative studies show a striking agreement between frog skin and plant tissues in respect to certain important aspects of permeability, antagonism, injury, recovery, and death.     

人外周血树突状细胞亚型的形态学观察

Ｓ１００ 蛋白染色是鉴定树突状细胞（ＤＣ） 的一种重要而可靠的方法。本文采用Ｓ１００ 蛋白免疫细胞化学方法及电镜观察, 对人外周血树突状细胞的亚型进行研究。结果表明： 人血ＤＣ在形态学上分为两个亚型－ Ⅰ型中等淋巴细胞大小, 线粒体少, 核内异染色质多; Ⅱ型胞体较大, 线粒体丰富, 异染色质少