OBSERVATIONS ON THE FINE STRUCTURE OF SPHEROPLASTS OF RHODOSPIRILLUM RUBRUM

Spheroplasts of the photosynthetic bacterium Rhodospirillum rubrum were prepared from cultures grown in either the presence or absence of light. Cells were converted into spheroplasts by using lysozyme and Versene and fixed in a sucrose-veronal-acetate buffer mixture containing osmium tetroxide. Some preparations were shadow-cast and examined whole; others were embedded in Epon 812 and sectioned. The action of lysozyme and Versene appears to result in removal of the cell wall in strips. The relationship of the chromatophores to the cytoplasmic membrane is readily visualized in sections of broken spheroplasts, and in areas the chromatophores are seen to be continuous with the membrane. In all preparations examined, no definite connections between individual chromatophores were observed. In some cells large spherical granules were evident which either possessed or lacked a clearly visible limiting membrane. On serial sectioning, all granules appeared bounded by a single membrane 40 A wide. The granule membrane was well defined only if the section came from the center of the granule. Sections at other levels showed either a diffuse membrane or no membrane at all. The reasons for this are discussed.     

OSMIUM ZINC IODIDE REACTIVE SITES IN THE EPIDERMAL LANGERHANS CELL

Fixation of epidermis with a mixture of osmium tetroxide and zinc iodide (OsO₄-ZnI₂) for 24 hr renders the central periodic lamella of the Langerhans cell granule (LCG), the Golgi region, and the nuclear envelope of epidermal Langerhans cells preferentially visible. The use of this technique on Langerhans cells in normal epidermis and in epidermis of patients with histiocytosis (Letterer-Siwe disease) allows a broader visualization of the LCG's than was heretofore possible with routine glutaraldehyde-osmium tetroxide fixation and uranyl acetate-lead staining. The identical staining of Golgi apparatus and LCG favors the view that there is close relation between the Golgi area and the LCG's. Different staining characteristics of the LCG's near the Golgi region and at the cell periphery, respectively, may suggest that the LCG undergoes changes on its way from the Golgi area towards the extracellular space. The hypothesis is advanced that the material which is heavily impregnated with metal after fixation with OsO₄-ZnI₂ might be a lipid.     

FINE STRUCTURE OF THE MUCOCYSTS OF COLACIUM CALVUM (EUGLENOPHYCEAE)1

The characteristic stalk of Colacium calvum Stein is formed from carbohydrate extruded by granules in the anterior portion of the cell. These granules exhibit the characteristics of mucocysts and their contents have two electron densities. A narrow extension of each granule extends past neighboring muciferous bodies to attachment sites in the posterior notch of the pellicle strip. The granule contains neutral polysaccharide which resembles that in the peripheral cisternae of the Golgi apparatus. The attachment site is structurally complex.     

STRUCTURE OF THE EUGLENOID STORAGE CARBOHYDRATE,PARAMYLON

Paramylon, the euglenoid storage carbohydrate, was studied by transmission electron microscopy (thin sectioning, negative staining, and freeze-etching) and scanning electron microscopy in order to develop a three-dimensional model of paramylon structure. The paramylon granule is a membrane-bound crystal composed of two types of segments, rectangular solids and wedges. The segments meet in the central region of the crystal. Both the segments and the granule as a whole are composed of several layers. Fibers traverse the paramylon granule in an overall concentric pattern. These fibers appear to be composed of bundles of microfibrils, which measure 4.0 nm in diameter and are similar to cellulose elementary microfibrils.     

EFFECTS OF THE SURFACTANTS ON THE CLEAVAGE AND FURTHER DEVELOPMENT OF THE SEA URCHIN EMBRYOS II. DISTURBANCE IN THE ARRANGEMENT OF CORTICAL VESICLES AND CHANGE IN CORTICAL APPEARANCE

After fertilization, two types of cortical vesicles ware examined under the electron microscope (the cortical vesicle I and II) and the light microscope (pigment granules and another kind of vesicles). The cortical vesicle I corresponds to the pigment granule and the cortical vesicle II does to the other vesicle.
The unequal division of the sea urchin embryo which occurs at the fourth cleavage was modified to an equal cleavage pattern by the treatment with sodium lauryl sulfate (SLS) or cetyl trimethyl ammonium bromide (CTAB). But other surfactants such as sodium deoxycholate, Tween 80, Lubrol PX did not have such an effect. The cell surface of the embryo which had been treated either SLS or CTAB became rough or smooth. Cortical vesicles and pigment granules disappeared and/or were dislocated from the cortex. However, cell organelles were as normal as the control. On the other hand, the cortical appearance of other surfactant-treated embryos showed no disturbance and cell organelles were also more or less normal. Therefore, the equalization of unequal cleavage is caused by the disturbance in the cortex and thus the cortex plays a major role on the micromere formation at the 16-cell stage and on the further sea urchin development.     

CONCOMITANT SYNTHESIS OF MEMBRANE PROTEIN AND EXPORTABLE PROTEIN OF THE SECRETORY GRANULE IN RAT PAROTID GLAND

After enzyme secretion the membrane of the secretory granule, which had been fused to the cell membrane, was resorbed into the cell. Experiments were therefore carried out to test whether formation of new secretory granules involves reutilization of the resorbed membrane or synthesis of a new membrane, de novo, from amino acids. Incorporation of amino acids-¹⁴C into proteins of various cell fractions was measured in vivo, 30, 120, and. 300 min after labeling. At all times the specific radioactivity of the secretory granule membrane was about equal to that of the granule's exportable content. At 120 and 300 min the specific radioactivity of the granule membrane and of the granule content was much higher than that of any other subcellular fraction. It is therefore concluded that the protein of the membrane is synthesized de novo concomitantly with the exportable protein. The proteins of the granule membrane could be distinguished from those of the granule content by gel electrophoresis. All major bands were labeled proportionately to their staining intensity. The amino acid composition of the secretory granule membrane was markedly different from that of the granule's content and also from that of the mitochondrial membrane. The granule membrane showed a high proline content, 30 moles/100 moles amino acids. The analyses show that the radioactivity of the granule membrane is indeed inherent in its proteins and is not due to contamination by other fractions. The possibility is considered that the exportable protein leaves the endoplasmic reticulum already enveloped by the newly synthesized membrane.     

ASSOCIATION OF THE ALKALINE PHOSPHATASE OF RABBIT POLYMORPHONUCLEAR LEUKOCYTES WITH THE MEMBRANE OF THE SPECIFIC GRANULES

The localization of alkaline phosphatase in the specific granules of rabbit polymorphonuclear leukocytes was investigated. The results obtained suggest very strongly that alkaline phosphatase is a component of the granule membrane. The enzyme remains attached to the membrane upon disruption of the granules by the use of detergents or by hypotonic shock and subsequent extraction with sodium sulfate, and can be isolated together with fragments of the granule membrane by isopycnic equilibration. Treatment of the granules with high amounts of Triton-X-100, sodium deoxycholate, or hexadecyltrimethylammonium bromide releases the enzyme in soluble form. In polymorphonuclear leukocyte homogenates, lysis of the granules is needed in order to render alkaline phosphatase fully accessible to substrates. This suggests that the catalytic site of the enzyme is exposed at the inner face of the granule membrane.     

STUDIES ON THE FINE STRUCTURE OF THE MAMMALIAN TESTIS : I. DIFFERENTIATION OF THE SPERMATIDS IN THE CAT (FELIS DOMESTICA)

The differentiation of cat spermatids was studied in thin sections examined with the electron microscope. The Golgi complex of the spermatid consists of a central aggregation of minute vacuoles, partially surrounded by a lamellar arrangement of flattened vesicles. In the formation of the acrosome, one or more moderately dense homogeneous granules arise within vacuoles of the Golgi complex. The coalescence of these vacuoles and their contained granules gives rise to a single acrosomal granule within a sizable membrane-limited vacuole, termed the acrosomal vesicle. This adheres to the nuclear membrane and later becomes closely applied to the anterior two-thirds of the elongating nucleus to form a closed bilaminar head cap. The substance of the acrosomal granule occupies the narrow cleft between the membranous layers of the cap. The caudal sheath is comprised of many straight filaments extending backward from a ring which encircles the nucleus at the posterior margin of the head cap. Attention is directed to the frequent occurrence of pairs of spermatids joined by a protoplasmic bridge and the origin and possible significance of this relationship are discussed.     

Linking Macroscopic with Microscopic Neuroanatomy Using Synthetic Neuronal Populations

Dendritic morphology has been shown to have a dramatic impact on neuronal function. However, population features such as the inherent variability in dendritic morphology between cells belonging to the same neuronal type are often overlooked when studying computation in neural networks. While detailed models for morphology and electrophysiology exist for many types of single neurons, the role of detailed single cell morphology in the population has not been studied quantitatively or computationally. Here we use the structural context of the neural tissue in which dendritic trees exist to drive their generation in silico. We synthesize the entire population of dentate gyrus granule cells, the most numerous cell type in the hippocampus, by growing their dendritic trees within their characteristic dendritic fields bounded by the realistic structural context of (1) the granule cell layer that contains all somata and (2) the molecular layer that contains the dendritic forest. This process enables branching statistics to be linked to larger scale neuroanatomical features. We find large differences in dendritic total length and individual path length measures as a function of location in the dentate gyrus and of somatic depth in the granule cell layer. We also predict the number of unique granule cell dendrites invading a given volume in the molecular layer. This work enables the complete population-level study of morphological properties and provides a framework to develop complex and realistic neural network models.     

ELECTRON MICROSCOPE STUDIES ON THE DICTYOSOMES AND ACROBLASTS IN THE MALE GERM CELLS OF THE CRICKET

The dictyosome (Golgi body) in the secondary spermatocyte of the cricket appears in electron micrographs as a duplex structure composed of (a) a group of parallel double-membraned lamellae and (b) a group of associated vacuoles arranged along the compact lamellae in a chain-like fashion. This arrangement of ultramicroscopic structure for the dictyosomes is strikingly comparable to that described for the Golgi apparatus of vertebrates. Accordingly, the two are considered homologous structures. Associated with the duplex structure of the dictyosomes is a differentiated region composed of small vacuoles. This is thought to represent the pro-acrosome region described in light microscope preparations. In the spermatid the dictyosomes fuse, giving rise to the acroblast. Like the dictyosomes, the acroblasts are made up of double-membraned lamellae and associated vacuoles. In addition, a differentiated acrosome region is present which, in some preparations, may display the acrosome vacuole and granule. Both the dictyosomes and acroblasts are distinct from mitochondria.     

人体病理组织中细菌L型的电镜观察

对9例细菌L型感染的人体病理组织进行透射电镜观察。结果显示:(1)L型可分布于组织间质或进入吞噬细胞、上皮细胞和癌细胞等细胞胞质;(2)L型具有多形态、大小不等、胞壁缺陷、电子密度低等特点,细胞胞质内的细菌L型尚有A、B两种形态区别;(3)L型在组织中形成了不完全箍缩分裂;(4)宿主细胞超微结构仅出现轻微改变。本结果与文献报道基本一致,提出了透射电镜下病理组织中细菌L型的形态特征及分布;并对L型感染与慢性炎症的关系等问题进行了讨论。     

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.     

A FINE STRUCTURAL INVESTIGATION OF SURFACE SPECIALIZATIONS AND THE CORTICAL REACTION IN EGGS OF THE CNIDARIAN BUNODOSOMA CAVERNATA

Developing oocytes of the cnidarian Bunodosoma cavernata are located within the mesoglea of the mesenteries of the gastrovascular cavity. The cortex of the more mature vitellogenic oocytes contains numerous, electron-dense, membrane-bound, cortical granules. The surface of these oocytes possesses prominent radially projecting structures termed cytospines. Each cytospine has a core of microfilaments, 50–70 Å in diameter, that extends basally as a rootlet through the cortical layer. During spawning, ova lacking any extraneous investments are released from the enclosing gastrodermis. As a consequence of fertilization or events associated with the earliest stages of development the ova undergo a massive cortical reaction. This reaction, which occurs during or just after release of the ova, involves extensive reorganization of the cortical layer. The cortical granule membranes and egg surface membrane fuse and vesiculate resulting in the massive discharge of granule contents. This event is accompanied by the loss of vesicular remnants of cortical ooplasm and the disruption of cytospine organization. Light and electron microscope comparisons of unreacted and reacted eggs show that the reaction results in a significant decrease in egg diameter with the oolemma of the reacted egg reorganizing in a position centripetal to its original location.     

冲绳海槽海底黑烟囱中微生物化石的发现及其意义

采用光学显微镜以及扫描电镜对冲绳海槽海底黑烟囱样品进行研究,发现了大量的微生物化石,它们保留了完好的形态,主要有四种不同类型的丝状体,可能是硫或者铁氧化化能自养细菌和真菌。这些化石微生物的鉴别基于大小、形状、细胞分裂、群落聚集等物理标志。初步研究表明这些微生物不仅依存于海底热液活动,同时在热液成矿过程中起着重要的作用。     

ISOLATION AND PROPERTIES OF SECRETORY GRANULES FROM RAT ISLETS OF LANGERHANS : II. Ultrastructure of the Beta Granule

Beta granules isolated from rat islets of Langerhans and subjected only to phosphotungstic acid had, in negatively stained images, a 50-A periodicity. This periodicity was also observed in thin-section profiles of beta granules in intact cells. In shadowed preparations, the granules were spherical in shape and had irregular edges and surface structure. The presence of such a periodicity in the beta granule indicates that its matrix may be composed of a crystalline material.     

THE FINE STRUCTURE OF THE RAT CEREBELLUM : II. The Stellate Neurons, Granule Cells, and Glia

This paper describes the fine structure of the granule cells, stellate neurons, astrocytes, Bergmann glia, oligodendrocytes, and microglia of the rat cerebellum after fixation by perfusion with buffered 1 per cent osmium tetroxide. Criteria are given for differentiating the various cell types, and the findings are correlated with previous light microscope and electron microscope studies of the cerebellum.     

DYNAMIC CHANGES IN THE ULTRASTRUCTURE OF THE ACINAR CELL OF THE RAT PAROTID GLAND DURING THE SECRETORY CYCLE

Synchronization of the secretory cycle in vivo was obtained by injecting isoprenaline as an inducer of secretion. A quantitative correlation between enzyme release, its subsequent reaccumulation, and the sequence of ultrastructural changes was found. At the ultrastructural level secretion was paralleled by depletion of zymogen granules through fusion of the granule membrane with the lumen membrane and discharge of the content. Each zymogen granule membrane, once connected with the lumen, acted as a lumen membrane. Fusion was thus sequential and resulted in a dramatic enlargement of the lumen space. During the entire process the passage between the lumen and the intercellular space remained blocked by the tight junctions, as shown by their impenetrability to ferritin. Reduction of the lumen size following enzyme discharge seemed to be achieved by withdrawal of lumen membrane in the form of small smooth vesicles which appeared mostly in the apical part of the cell. At the same time, the cell retracted towards the lumen, the whole process being completed within 2 hr from onset of secretion. Disappearance of the smooth vesicle followed, concomitant with formation of many condensing vacuoles and appearance of mature zymogen granules. The fate of the zymogen granule membrane, including its fusion with the lumen membrane, resorption in the form of small smooth vesicles, and its eventual reutilization mediated by the Golgi system, is discussed.     

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.     

ELECTRON MICROSCOPIC DEMONSTRATION OF A DITHIOTHREITOL-LABILE VITELLINE COAT SURROUNDING THE UNFERTILIZED EGG OF COMANTHUS JAPONICA (ECHINODERMATA: CRINOIDEA)*

In Comanthus, the unfertilized egg is surrounded by a vitelline coat, which is separated from the underlying plasma membrane by a space several hundred Ångstroms wide. By electron microscopy, the vitelline coat is a distinct layer 100 to 150 Å thick, which consists of finely granular material of moderate electron density. Treatment for 3 min in 0.01 M dithiothreitol in sea water buffered to pH 9.2 almost completely removes the vitelline coat and causes the irregularly shaped egg to become spherical. After such DTT-treated eggs have been washed for 2 min in sea water, they cannot be fertilized, but they can undergo a cortical reaction when treated with ionophore A23187. This cortical reaction consists of the exocytosis of cortical granule material directly into the surrounding sea water. By several hours after DTT treatment, most of the eggs, whether exposed to ionophore or not, fragment into spheres of diverse sizes.     

THE PYRENOID OF SCENEDESMUS QUADRICAUDA

The development of the pyrenoid of Scenedesmus quadricauda from the time of its initiation and its subsequent activities is described in some detail. Correlation is made between the evidence from light and electron microscopy. The pyrenoid is a dynamic organelle which continues to change its appearance throughout the development of the algal cell due to the following factors: the deposition of starch platelets within the periphery of the expanding matrix; the separation of starch grains into individual pockets by the intrusive growth of the chloroplast lamellae in centripetal fashion; and the transition of the shape of the starch from concavo-convex platelets to lenticular grains. By these processes starch grains are continuously formed by deposition of carbohydrates within the matrix. The grains accumulate within the chloroplast, maintaining an organic connection with each other by slender starch bridges. Some parental starch grains are passed on to daughter cells during cell division. By taking into account the planes of cleavage during cell division, it is not difficult to see that pyrenoid starch grains could become distributed throughout the daughter chloroplast, regardless of their distance from the pyrenoid.