文昌鱼Sertoli细胞超微结构的进一步研究

用光镜和电镜技术观察厦门文昌鱼(Branchiostoma belcheri Gray)精巢中Sertoli细胞在不同发育时期的细微结构后发现:精巢发育Ⅰ—Ⅱ期,Sertoli细胞贴近基底膜,与生殖细胞相间排列;Ⅲ—Ⅳ期时,逐渐向管腔方向移动;这种细胞在核的顶部及其周围胞质中,有丰富的粗面内质网、发育良好的高尔基复合体、大量溶酶体及糖元颗粒,并可见精细胞附着在Sertoli细胞的胞质中。据此,我们认为Sertoli细胞具有营养、吞噬和释放精子的功能。本文旨在为研究这种细胞的内分泌功能提供有价值的依据。     

泽蛙单倍体细胞RNA含量对胚胎发育和成活的影响

对两栖类单倍体的综合症以及死亡原因,前人有许多不同认识,本文用实验说明,单倍体细胞的RNA含量不及二倍体的一半,并认为,单倍体泽蛙的死亡原因与其细胞中RNA含量不足密切相关。     

THE FINE STRUCTURE OF THE GALL BLADDER EPITHELIUM OF THE MOUSE

Sections of mouse gall bladder epithelium fixed by perfusion with buffered osmium tetroxide have been studied in the electron microscope as an example of simple columnar epithelium. The free surface presents many microvilli, each presenting a dense tip, the capitulum, and displaying a radiating corona of delicate filaments, the antennulae microvillares. Very small pit-like depressions, representing caveolae intracellulares, are encountered along the cell membrane of the microvilli. The free cell surface between microvilli shows larger cave-like depressions, likewise representing caveolae intracellulares, containing a dense material. The lateral cell borders are extensively folded into pleats, which do not interdigitate extensively with corresponding folds of the adjacent cell membrane. The terminal bars are shown to consist of thickened densities of the cell membrane itself in the region of insertion of the lateral cell wall with the free cell surface. This thickening is associated with an accumulation of dense cytoplasmic material in the immediate vicinity. The terminal bar is thus largely a cytoplasmic and cell membrane structure, rather than being primarily intercellular in nature. The basal cell membrane is relatively straight except for a conical eminence near the center of the cell, projecting slightly into the underlying tunica propria. The basal cell membrane itself is overlain by a delicate limiting membrane, which does not follow the lateral contours of the cell. Unmyelinated intercellular nerve terminals with synaptic vesicles have been encountered between the lateral walls of epithelial cells. A division of the gall bladder epithelial cell into five zones according to Ferner has been found to be convenient for this study. The following cytoplasmic components have been noted, and their distribution and appearance described: dense absorption granules, mitochondria, Golgi or agranular membranes, endoplasmic reticulum or ergastoplasm, ring figures, and irregular dense bodies, perhaps lipoid in nature. The nucleus of these cells is also described.     

THE PHYSICAL BASIS OF THE POSITIVE PHOTOTROPISM OF PHYCOMYCES

A physical basis is demonstrated, in the case of a cylindrical cell illuminated with parallel light from one side, for greater photochemical action in the half of the cell farthest from the source of light, when the cell is surrounded by a medium of refractive index less than that of the cell. Factors governing the balance and magnitude of unequal action of light in the two halves of the cell are: the refractive index of the cell, the cell radius, and the absorption coefficient of the intracellular pigment. A limiting value of absorption coefficient is deduced which cannot be exceeded in cells of a particular size showing positive phototropism. In terms of this mechanism the positive phototropism of Phycomyces in air is explained.     

THE SIZE OF BACTERIA AS THE CAUSE OF THE LOGARITHMIC ORDER OF DEATH

Death of unicellular organisms is brought about by the inactivation of a certain number of essential molecules in the cell. If the number of these essential molecules is only one per cell, the order of death is the same as if the cell were identical with this molecule; the order of death is logarithmic following the mass law. If more than one molecule must be inactivated before the cell dies, the order of death is not logarithmic. With 2 or 3 molecules, it still resembles the logarithmic order, but with an increasing number of reacting molecules, it approaches more and more the order of death known with higher organisms, namely a period of no death, followed by a comparatively short period of rapid death. The decision whether or not the logarithmic order exists, should be based upon the constancy of the death rate See PDF for Equation. The existence of a straight line when logarithms of survivors are plotted against time, is not sufficient proof unless the initial number of cells is included. These deductions are made with the assumption that all organisms are exactly alike, and show no individual variations or graded resistance. With most bacteria, the order of death is so nearly logarithmic that death must be brought about by the inactivation of only one molecule, though there may be several molecules of this same type in each cell.     

红松配子体的发育过程

红松是我国主要用材树种,材质优良。我国主要分布在长白山和小兴安岭,随着森林工业的发展,大面积的原始森林迅速减少,人工更新日趋重要。在生产中采用种子育苗,因此对红松种子的发育规律应全面掌握,以便为种子园建立、良种选育采取有效措施提供理论依据。根据国内外有关报导,红松雌雄配子的形成、受精作用已有一定的研究^[14、15],但这些研究只侧重在小孢子母细胞的减数分裂和受精作用。故对雌雄配子体的发育过程仍需深入研究,尤其是授粉后的雄配子体发育和精子进入颈卵器的过程,均未见详细报导。     

EFFECT OF CYCLOHEXIMIDE ON THE CELL CYCLE OF THE CRYPTS OF THE SMALL INTESTINE OF THE RAT

A single injection of 1.5 mg/kg of cycloheximide induces a complete disappearance of mitotic activity in rat intestinal crypts within 1.5–2 hr. No significant necrosis of crypt cells is observed even though this phenomenon is accompanied by a marked decrease in uptake of labeled precursors into protein and DNA. Mitoses reappear 6 hr after injection and recovery then follows a cyclic pattern over a period equivalent to one cell cycle, thereby reflecting at least a partial synchronization of cell division. Concurrent use of colchicine, an agent known to induce metaphase arrest, has demonstrated that cycloheximide, while having no apparent effect on cells already in division, prevents the entrance of new cells into visible mitosis. Analysis of the cell cycle suggests that one block initiated by cycloheximide occurs in G₂, presumably as the result of an interference with the formation of protein(s) required for the normal progression of cells from this phase of the cycle into mitosis.     

THE COMPOSITION OF THE CELL SAP OF THE PLANT IN RELATION TO THE ABSORPTION OF IONS

1. Chemical examination of the cell sap of Nitella showed that the concentrations of all the principal inorganic elements, K, SO₄, Ca, Mg, PO₄, Cl, and Na, were very much higher than in the water in which the plants were growing. 2. Conductivity measurements and other considerations lead to the conclusion that all or nearly all of the inorganic elements present in the cell sap exist in ionic state. 3. The insoluble or combined elements found in the cell wall or protoplasm included Ca, Mg, S, Si, Fe, and Al. No potassium was present in insoluble form. Calcium was predominant. 4. The hydrogen ion concentration of healthy cells was found to be approximately constant, at pH 5.2. This value was not changed even when the outside solution varied from pH 5.0 to 9.0. 5. The penetration of NO₃ ion into the cell sap from dilute solutions was definitely influenced by the hydrogen ion concentration of the solution. Penetration was much more rapid from a slightly acid solution than from an alkaline one. It is possible that the NO₃ forms a combination with some constituent of the cell wall or of the protoplasm. 6. The exosmosis of chlorine from Nitella cells was found to be a delicate test for injury or altered permeability. 7. Dilute solutions of ammonium salts caused the reaction of the cell sap to increase its pH value. This change was accompanied by injury and exosmosis of chlorine. 8. Apparently the penetration of ions into the cell may take place from a solution of low concentration into a solution of higher concentration. 9. Various comparisons with higher plants are drawn, with reference to buffer systems, solubility of potassium, removal of nitrate from solution, etc.     

THE FINE STRUCTURE AND DEVELOPMENT OF THE COMPANION CELL OF THE PHLOEM OF ACER PSEUDOPLATANUS

At maturity the companion cell of the phloem of the sycamore Acer pseudoplatanus has a large nucleus, simple plastids closely sheathed with rough endoplasmic reticulum, and numerous mitochondria. The cytoplasm contains numerous ribosomes, resulting in a very electron-opaque cytoplasm after permanganate fixation. Bodies similar to the spherosomes of Frey-Wyssling et al. (4) are collected in clusters and these also contain bodies of an unidentified nature similar to those found by Buttrose (1) in the aleurone cells of the wheat grain. The pores through the wall between the companion cell and sieve tube are complex and develop from a single plasmodesma. Eight to fifteen plasmodesmata on the companion cell side communicate individually with a cavity in the centre of the wall which is linked to the sieve tube by a single pore about twice the diameter of an individual plasmodesma. This pore is lined with material of an electron opacity equivalent to that of material bounding the sieve plate pores. The development of the cell organelles, the possible role played in the phloem tissue by the companion cell, and the function of the complex pores contained in its wall are discussed.     

THE ULTRASTRUCTURE AND HISTOCHEMISTRY OF THE SYNERGIDS OF COTTON

The composition and ultrastructure of the synergids of cotton were studied. The cells were found to be surrounded by a partial wall composed of cellulose, hemicellulose, and pectins. The structure of the wall was observed to consist of an unusual fibrillar arrangement. The filiform apparatus was demonstrated to be an extension of the wall at the micropylar end of the cell. Large amounts of ER surround the filiform apparatus. Also associated with the latter are large numbers of plastids and mitochondria. The nucleus is large and contains a single, large nucleolus and, frequently, 1 or more micronucleoli. The nuclear membrane contains membrane-bound vesicles but has few extensions into the cytoplasm. The ER is oriented parallel to the long axis of the cell and decreases in concentration from the micropylar to the chalazal end of the cell. Dictyosomes are common throughout the cell but are more numerous in the midportion where they are closely associated with the ER. The chalazal end of the cell is occupied by vacuoles rich in an inorganic compound which leaves a considerable residue of ash. Spherosome-like bodies are common throughout the cell. Both the plastids and mitochondria show evidence of division. Ribosomes are numerous and are both free and associated with the ER, nucleus, plastids, and mitochondria. The function of the synergids is proposed to be the absorption, storage, and transport of compounds from the nucellus. On the basis of this function, it is suggested that the synergids act by providing material to the egg and the developing embryo and endosperm and that they are involved in the growth of the pollen tube into the embryo sac.     

THE ULTRASTRUCTURE OF THE PELLICLE COMPLEX OF EUGLENA GRACILIS

The pellicle complex of E. gracilis is composed of the cell membrane, the ridge and groove with the notch, four fibrils, and the subpellicular ER. The cell membrane is of unit membrane configuration and covers the outside of the cell, the cytostome, the gullet, and the reservoir. The notch of the pellicle complex has always a close topographic relationship to two particular fibrils, as well as the subpellicular ER. The gullet is that region between the reservoir and the cytostome which, in addition to longitudinal fibrils, is surrounded by a single row of circular fibrils. The circumference of the cytostome has twenty large pellicular ridges alternating with small pellicular ridges. Alternating tall and small pellicular ridges cover the entire cell during division.     

EXPERIMENTAL MODIFICATION OF THE MORPHOGENETIC BEHAVIOR OF THE ISOLATED SUB-APICAL CELL OF THE APEX OF SPHACELARIA CIRROSA (PHAEOPHYCEAE)1

Experimental isolation of the terminal cells of the apex of Sphacelaria cirrosa (Roth) C. Agardh shows that the isolated apical cell retains a self-maintained mode of functioning. The isolated sub-apical cell, however, gives rise to a newly-formed axis after undergoing a different type of developmental sequence. An experimental scheme allowing one to defer isolation of the sub-apical cell after killing the apical cell shows that the maintenance, for a few hours only, of connections with subjacent cells is sufficient to induce an apical type mode of functioning in the sub-apical cell. The sequential analysis of the first cytological events in this phenomenon allows one to relate this modification of the morphogenetic program to a functional and polarized arrangement of organelles within the cell reconstituting the apical. The morphogenetic program is characterized by a migration of the nucleus to a distal position prior to an asymmetrical mitosis characteristic of the apical mode of functioning.     

NOTE ON THE NATURE OF THE CURRENT OF INJURY IN TISSUES

Leading off from two places on the same cell (of Nitella) with 0.001 M KCl we observe that a cut produces only a temporary negative current of injury. If we lead off with 0.001 M KCl from any cell to a neighboring cell we find that when sap comes out from the cut cell and reaches the neighboring intact cell a lasting negative "current of injury" is produced. This depends on the fact that the intact cell is in contact with sap at one point and with 0.001 M KCl at the other (this applies also to tissues composed of small cells). If we employ 0.1 M KCl in place of 0.001 M the current of injury with a single cell is positive (and is more lasting when a neighboring cell is present). Divergent results obtained with tissues and single cells may be due in part to these factors.     

THE ROLE OF PLASMODESMS IN THE TRANSLOCATION OF VIRUS

Although intracellular inclusion bodies may occur in every cell over large areas of the epidermis, they have not been found in the guard cells of the stomata. No protoplasmic connexions could be shown to exist between the guard cells and the surrounding tissues. These findings suggest that, owing to the absence of plasmodesms, the virus is unable to reach the guard cells. Support is lent to the view that, when the virus moves in the ground tissue of the host, it is carried from cell to cell along the protoplasmic bridges.     

THE EFFECT OF SALT CONCENTRATION OF THE MEDIUM ON THE RATE OF OSMOSIS OF WATER THROUGH THE MEMBRANE OF LIVING CELLS

1. Using the unfertilized egg of the sea urchin, Arbacia, as osmometer, it was found that the rate with which water enters or leaves the cell depends on the osmotic pressure of the medium: the velocity constant of the diffusion process is higher when the cell is in concentrated sea water, and lower when the sea water medium is diluted with distilled water. Differences of more than tenfold in the value of the velocity constant were obtained in this way. When velocity constants are plotted against concentration of medium, a sigmoid curve is obtained. 2. These results are believed to indicate that cells are more permeable to water when the osmotic pressure of the medium is high than when it is low. This relation would be accounted for if water should diffuse through pores in a partially hydrated gel, constituting the cell membrane. In a medium of high osmotic pressure, the gel is conceived to give up water, to shrink, and therefore to allow widening of its pores with more ready diffusion of water through them. Conversely, in solutions of lower osmotic pressure, the gel would take up water and its pores become narrow.     

THE ULTRASTRUCTURE OF THE QUIESCENT CENTER IN THE APEX OF CULTURED ROOTS OF CONVOLVULUS ARVENSIS L.

Cultured roots of the common bindweed, Convolvulus arvensis L. growing at the rate of 15–30 mm/day in sterile nutrient medium were fixed for electron microscopic analysis. The ultrastructure of the quiescent center, the initials of the ground meristem, and the initials of the procambium were studied in order to determine whether sequential structural changes could be correlated with models for specifying the mechanisms by which cell differentiation and cell division might be controlled. The differentiation of cells in the root proper occurs very gradually in linear files from the site of the quiescent center proximally into the different tissue regions. Major structural changes, such as the orientation and subsequent elongation of cells along the longitudinal axis of the root and cell wall changes, indicate that the control of differentiation and perhaps cell division occurs in radial gradients outwardly from the quiescent center.     

THE LABELLED MITOSES CURVE AND THE ESTIMATION OF THE PARAMETERS OF THE CELL CYCLE

A method is described for fitting a 'fraction labelled mitoses'curve to a set of data points and for estimating the values of the best fitting parameters of the cell cycle. Estimates of the SE of the parameters are obtained. The method depends on the fact that when gamma distributions are used to describe the durations of the phases of the cell cycle, the Laplace transform of a FLM curve can be described by simple analytic functions enabling a least squares fit to be made to a set of Laplace transforms of the experimental data. The method is easy to program and quick to execute.     

噬菌体脱毒机理的研究Ⅰ

用噬菌体处理河流弧菌Ⅱ的时间不同,细菌菌落的透明度和超微结构也不一样。在吸附后７ｈ开始菌落出现透明度的变化,首先是不透明（乳黄色）的菌落占绝对优势,但已出现半透明和透明菌落,培养到４８ｈ时,几乎全部变为透明菌落。透明菌落不再能与其噬菌体吸附而产生噬斑,也不会再感染鲍而产生脓疱病。透射电镜观察发现,透明菌落的菌细胞形状和结构大都发生变化。细胞壁薄,细胞质浓缩集中在细胞的一侧或一端。不透明菌落细胞形状正常,细胞壁完整,细胞质外延使细胞横切面呈指环状。电镜观察不同时间取样发现,１号样品细胞结构无明显变化。２号样品多数细胞产生外膜泡。３号样品许多细胞结构与１号相似,但在一些细胞的附近出现成簇的外膜泡和噬菌体。４号样品细胞结构变化较大,细菌的核区被破坏,在细胞的周围发现许多噬菌体。５号样中发现许多菌细胞被破坏,也在一些细胞内发现噬菌体。６号样中透明菌落和不透明菌落细胞结构变化明显。７号样几乎所有菌落都变为透明状,许多细胞破裂等。     

THE FINE STRUCTURE OF VON EBNER''S GLAND OF THE RAT

The fine structure of von Ebner's gland was studied in untreated rats and rats stimulated to secrete by fasting-refeeding or injection of pilocarpine. Cytological features were similar to those reported for pancreas and parotid gland. Abundant granular endoplasmic reticulum filled the basal portion of the cell, a well-developed Golgi complex was located in the vicinity of the nucleus, and the apical portion of the cell was filled with dense secretory granules. Dense heterogeneous bodies resembling lysosomes were closely associated with the Golgi complex. Coated vesicles were seen in the Golgi region and also in continuity with the cell membrane. Granule discharge occurred by fusion of the granule membrane with the cell membrane at the secretory surface. Successive fusion of adjacent granules to the previously fused granule formed a connected string of granules in the apical cytoplasm. Myoepithelial cells were present within the basement membrane, and nerve processes were seen adjacent to acinar and myoepithelial cells. Duct cells resembled the intercalated duct cells of the major salivary glands.