LIGHT AND ELECTRON MICROSCOPIC STUDIES OF THE FUSION CELL IN ASTEROCOLAX GARDNERI SETCH. (RHODOPHYTA,CERAMIALES)12

The fusion cell in Asterocolax gardneri Setch, is a large, multinucleate, irregularly-shaped cell resulting from cytoplasmic fusions of haploid and diploid cells. Subsequent enlargement takes place by incorporating adjacent gonimoblast cells. The resultant cell consists of two parts—a central portion of isolated cytoplasm, surrounded by an electron dense cytoplasmic barrier, and the main component of the fusion cell cytoplasm surrounding the isolated cytoplasm. The fusion cell contains many nuclei, large quantities of floridean starch, endoplasmic reticulum, and vesicles, but few mitochondria, plastids and dictyosomes. The endoplasmic reticulum forms vesicles that apparently secrete large quantities of extracellular mucilage which surrounds the entire carposporophyte. The isolated cytoplasm also is multinucleate but lacks starch and a plasma membrane. Few plastids, ribosomes and mitochondria are found in this cytoplasm. However, numerous endoplasmic reticulum cisternae occur near the cytoplasmic barrier and they appear to secrete material for the barrier. In mature carposporophytes, all organelles in the isolated cytoplasm have degenerated.     

THE DIFFERENTIATION OF WHITE ADIPOSE CELLS : An Electron Microscope Study

Differentiating white adipose tissue from presumptive and developing fat pads of newborn and young rats was fixed in buffered osmium tetroxide, embedded in Vestopal W, and examined in an electron microscope. Pre-adipose cells were found to be fibroblasts characterized by their spindle shape, long tenuous cytoplasmic extensions, and profuse endoplasmic reticulum. The developmental stages traced from fibroblast to mature adipose cell show a gradual change in cell shape, an accumulation of cytoplasm and non-membrane-bounded lipid, a decrease in the endoplasmic reticulum, and a change in shape of mitochondria. Transitory glycogen appears at mid-differentiation. Numerous smooth-membraned vesicles occur in the cytoplasm throughout differentiation. Pinocytosis is constantly evident. Cells of the multilocular stage are shown to differ from brown fat cells, particularly with respect to cytoplasmic membrane systems and mitochondria. No transport of particulate lipid from the lumen of the capillary to, or within, the adipose cell was detected, nor could any cell organelle be demonstrated to be visibly related to lipid synthesis and/or deposition.     

Cytoplasmic Ultrastructural Changes During Microsporogenesis of Gossypium hirsutum:With Emphasis on

Conspicuous cytoplasmic changes took place during the microsporogenesis of Gossypium hirsutum L. These changes mainly involved in the ribosomes, plastids and mitochondria. During meiotic prophase 1, the ribosome population of the cytoplasm diminished and reached to aminimum during pachytene--diplotene interval, and the membrane structures of both plastids and mitochondria turned unclear. In metaphase I, cytoplasmic ribosome population restored to premeiotic level; plastids and mitochondria also regained their normal structures. The disintegration of nucleoloids from nucleus was the main mechanism for the restoration of ribosome population in metaphase I cytoplasm. Endoplasmic reticulum may play an important role in the elimination and protection of part of cytoplasmic ribosomes during prophase I. These obvious cytoplasmic changes are considered to be relevant to sporophyte-gametophyte transition.     

THE FINE STRUCTURE OF TESTICULAR INTERSTITIAL CELLS IN GUINEA PIGS

In guinea pig testes perfused with either glutaraldehyde or osmium tetroxide fixative, the cytoplasm of the interstitial cells contains an exceptionally abundant agranular endoplasmic reticulum. The reticulum in central regions of the cell is a network of interconnected tubules, but in extensive peripheral areas the reticulum is commonly organized into closely packed, flattened cisternae which are fenestrated. Occasional small patches of the granular reticulum occur in the cytoplasm and connect freely with the agranular reticulum. The mitochondria have a dense matrix and contain cristae and some tubules. The Golgi complex is disperse and shows no evidence of secretory material. The cytoplasm also contains lipid droplets. Lipofuscin pigment granules are probably polymorphic residual bodies and contain three components: (1) a dense material which at high magnification shows a 75-A periodicity; (2) a medium-sized lipid droplet; and (3) a cap-like structure. In glutaraldehyde-perfused testis the interstitial cell cytoplasm appears to have the same density from cell to cell, and the agranular reticulum is tubular or cisternal but not in the form of empty vesicles. Thus the "dark" and "light" cells and the vesicular agranular reticulum sometimes encountered in other fixations may be artifacts. Biochemical results from other laboratories, correlated with the present findings, indicate that the membranes of the agranular endoplasmic reticulum in guinea pig interstitial cells are the site of at least two enzymes of androgen biosynthesis, the 17-hydroxylase and the 17-desmolase.     

The cytoskeleton of cryofixed Purkinje cells of the chicken cerebellum

Summary Cerebella of 3- to 6-week-old chickens were cryofixed in a nitrogen-cooled propane jet, deep-etched and rotary-shadowed. The use of a brief perfusion of 0.32 M sucrose improved the quality of the cryofixation and allowed the study of the deeper layers of the cerebellar cortex. It is reported that the cytoskeleton of the Purkinje cells (PC) shows distinct domains and composition of filamentous structures in the different regions of the cell cytoplasm, such as the perikaryon, the cytoplasm of dendrites and the axoplasm. The perikaryon is occupied by a meshwork of fine filaments, 4–7 nm in diameter, that extends from the nuclear outer membrane to the cell membrane. In this zone the cell organelles (e.g., endoplasmic reticulum, mitochondria) adopt a circular arrangement around the nucleus. All structures are anchored by microfilaments to the cytoplasmic network. The dendrites show a dense cytoplasmic network including bundles of microtubules, neurofilaments and microfilaments. Numerous aggregated globular components are attached to this cytoskeleton. The cytoskeleton of the dendritic spines shows axially oriented 10-nm bundles of filaments, which are interconnected and anchored also to the cell membrane and the components of the agranular endoplasmic reticulum by cross-linkers. As described in peripheral nerves, the axoplasm of axons in the central nervous system exhibits predominantly neurofilaments and microtubules aligned along the axis of the neuntes in a three-dimensional arrangement and interconnected by cross-linker filaments and filamentous structures.     

Effects of parathyroid hormone on osteoclasts in vivo

Summary Young rats were treated with high doses of parathyroid hormone (PTH). Osteoclasts from these animals revealed characteristic alterations in comparison to control cells: a) The cytoplasm contained large vacuoles with phagocytosed cells, some of which resembled osteoblasts or osteocytes. The vacuoles were interpreted as lysosomes because the engulfed cells often appeared partly digested and the vacuoles contained acid phosphatase as demonstrated histochemically, b) lipid droplets were present in the cytoplasm and usually located close to the endoplasmic reticulum and/or in regions with many free ribosomes, c) the Golgi complex was more frequently separated from the nuclei than in control cells, d) small coated cytoplasmic bodies were numerous in the peripheral cytoplasm, e) the membranes of the endoplasmic reticulum were fused in some places, f) cytoplasmic regions with numerous free ribosomes were frequent, g) large ring-shaped granules occurred in some mitochondria. Energy dispersive X-ray analysis of these granules provided evidence that they contained calcium and probably phosphorus, h) in some osteoclasts the mitochondria were enlarged. — The findings are consistent with an increased activity of osteoclasts and in particular a stimulation of the lysosomal system in these cells.This research was supported by grants no. 512-819, 512-1545 and 512-1912 from the Danish Research Council. The observations were reported in part at the annual meeting of the Scandinavian Society for Electron Microscopy in Aarhus 1972 (Lucht, 1973). — The authors thank Mr. K. Ibe for cooperation in the energy dispersive X-ray analysis, which was carried out at the JEOL (Europe) S. A. Application Center, Paris.     

阔口尖毛虫形成包囊期间细胞超微结构的观察

阔口尖毛虫形成囊期间,细胞质内出现条带状或管产产的内质网和由不同大小的囊泡组成的包囊壁前体。并且,前体的产生与内质网有关;细胞质内发生自噬泡消化现象,这是细胞将原有结构和能量进行贮存,利用的一种重要形式;大核向细胞质突出形成阿米巴形结构,这与大核向细胞质排出部分核物质有关。     

Observations on the gametolytic gland in the anaspidean opisthobranchs,Phyllaplysia taylori and Aplysia californica

The wall of the gametolytic gland in Aplysia and Phyllaplysia consists of a muscular layer lined with an epithelium incorporating four distinct cell types, some of which show intense secretory activity. The cytoplasm of these cells, rich in RNA, has a peripheral layer of densely-packed mitochondria in association with a smooth endoplasmic reticulum. Lipid globules, perhaps resulting from absorption of lumen contents by microvilli, appear in the cytoplasm in the course of growth and reproductive activity. A basal band of fibrillar material appears to serve as a cytoplasmic skeleton. The elaboration of cell types, extensive areas of cytoplasmic RNA, and vigorous secretory activity suggest important roles for this organ such as development of food reserves, recycling of sexual materials of high physiological value, and interaction with the bag cells of the nervous system in coordinating ovulation with the availability of capacitated, exogenous sperm.     

Immunocytochemical localization of pleurocidin to the cytoplasmic granules of eosinophilic granular cells from the winter flounder gill

The teleost gill is considered to be of significant immunological importance, as it is one of the first tissues exposed to environmental or pathogenic challenge and thus should be well equipped to mount an effective immune response. This study characterizes ultrastructurally and immunocytochemically a tissue granulocyte (eosinophilic granular cell) from the winter flounder gill that was previously determined to be involved in the gene expression and synthesis of a known antimicrobial peptide (pleurocidin). The cell is irregular in shape with a cytoplasm characterized by numerous large, electron-dense, membrane-bounded granules. The nucleus is euchromatic and closely associated with a prominent rough endoplasmic reticulum. The cytoplasm typically contains two to three mitochondria and a centralized Golgi apparatus surrounded by numerous electron-lucent vesicles. Immunogold staining of the cells with an anti-pleurocidin antibody shows large number of gold particles in direct association with the electron-dense granules. These data provide the first evidence definitively showing storage of an antimicrobial peptide in the cytoplasmic granules of an eosinophilic granule cell resident in gill tissue.     

Comparison of expression of three different sub-cellular targeted GFPs in transgenic Valencia sweet orange by confocal laser scanning microscopy

The green fluorescent protein (GFP) has become an ideal visual marker to monitor and quantify the expression of the transgene. It can be targeted to specific subcellular locations, including the endoplasmic reticulum, mitochondria, actin cytoskeleton and nuclei through the addition of signal peptides. Our previous work has resulted in transgenic citrus plants expressing cytoplasmic targeted GFP (Cy-GFP) or endoplasmic reticulum targeted GFP (Er-GFP) gene. To evaluate the localization of three different subcellular targeted GFP, i.e., Cy-GFP, Er-GFP and mitochondria targeted GFP (Mt-GFP) in citrus tissues and to utilize cell lines containing Mt-GFP for basic research in cell fusion, the plasmid pBI-mgfp4-coxIV encoding the Mt-GFP gene was successfully transferred into embryogenic callus of Valencia sweet orange (Citrus sinensis (L.) Osbeck) via Agrobacterium tumefaciens-mediated transformation. Furthermore, we compared the specific expression of these three different subcellular localized GFP constructs in cells of different mature leaf tissues (upper epidermis, palisade parenchyma, spongy parenchyma and lower epidermis) by a confocal laser scanning microscope (CLSM). Cytoplasmic-localized GFP expression was observed throughout the cytoplasm but appeared to accumulate within the nucleoplasm. The Er-GFP occurred within a layer very close to the cell wall. In addition, a stable fluorescence on the ER network throughout the guard cells was detected. Interestingly, the Mt-GFP specifically expressed in the guard cells to particles of about 1–2 μm within the cytoplasm in this case. To verify that the fluorescent particles observable in the guard cells are indeed mitochondria, we co-localize the Mt-GFP fusion protein with a mitochondrial-specific dye in citrus protoplasts. These results demonstrate that the subcellular distribution of the three subcellular targeted GFP is very distinct in citrus leaf cells and the cell lines containing Mt-GFP gene can be further used in citrus basic cell fusion research.     

四种淡水养殖鱼类血细胞的细微结构

四种淡水鱼的血细胞形态基本相似。红血球形态与其他低等脊椎动物基本相似。淋巴球绝大部分是小淋巴球:单核球数量较少;四种鱼的嗜中性白血球形态结构差不多,胞核多为蚕豆形,很少见分叶核,分叶一般也只有二叶,这与哺乳类显然不同;嗜酸性白血球的形态结构与其他脊椎动物基本相似;在少数血涂片中看到了嗜碱性白血球。       

Fine structure of the formation and fate of the residual bodies of mouse spermatozoa with evidence for the participation of lysosomes

Routine electron microscopy in combination with subcellular localization of acid phosphatase has been employed to study the formation and fate of residual cytoplasmic bodies extruded into the tubular lumen shortly before spermiation. Prior to extrusion the spermatid cytoplasm contains lipid droplets, mitochondria, ribosomes, endoplasmic reticulum, the caudally migrated Golgi apparatus, and numerous multivesicular and multigranular bodies. These membrane-limited bodies and the Golgi zone stain heavily for acid phosphatase. Following extrusion the residual bodies undergo a series of alterations: (1) disruption of multigranular bodies with release of free granules; (2) sequestration of granules, ribosomes, and reticulum inside double-membrane-limited vacuoles derived from Golgi lamellae; (3) appearance of numerous, single-membrane-bound, cytoplasmic vacuoles; (4) fragmentation; (5) peripheral migration toward the tubular wall; and (6) phagocytosis of these migrating fragments by the Sertoli cells. The demonstration of acid phosphatase activity within free granules, the sequestering Golgi lamellae, and both classes of vacuoles suggests that initial residual body degradation occurs through lysosomal cytoplasmic autophagy.     

CYTOLOGICAL ALTERATIONS RELATED TO STIMULATION OF THE ZONA GLOMERULOSA OF THE ADRENAL GLAND

The structure of the zona glomerulosa of the rat adrenal gland stimulated by sodium restriction has been studied by light and electron microscopy. The major changes observed during the course of the experiment in stimulated glands involve cytoplasmic droplets, mitochondria, and the endoplasmic reticulum. There is a progressive decrease in the number of cytoplasmic droplets of low electron opacity. Numerous, greatly elongated mitochondria containing parallel arrays of tubules are noted. These tubules extend from within the mitochondria through gaps in the mitochondrial-limiting membranes into the cytoplasm. In addition, amorphous intramitochondrial deposits, possibly aldosterone precursors, are seen. Increased amounts of smooth-surfaced endoplasmic reticulum, often showing complex arrangements, are another feature of the stimulated zona glomerulosa. Other alterations include the presence of large numbers of dense bodies as well as cytoplasmic droplets of high electron opacity. These observations are discussed in relation to the biosynthesis of aldosterone.     

Intracisternal polycylinders: A cytoplasmic structure in cells of the terrestrial slug Arion empiricorum férussac (Pulmonata,Stylommatophora)

Study of the digestive organs of the slug Arion empiricorum with the electron microscopy has revealed cytoplasmic structures that we call intracisternal polycylinders (ICPC). They consist of cylinders of cytoplasm (about 550 A in diameter) arranged in sheafs within cisterns of the endoplasmic reticulum. They appear in different cell types, being most common in the digestive epithelium of the midgut. Their morphology and apparent association with other cytoplasmic organelles such as mitochondria, peroxisomes, multivesicular and residual bodies suggests that the ICPC might be involved in exchange, transport and oxidation processes, contributing to the excretory function at a subcellular level.     

ORGANIZATION AND BREAKDOWN OF THE PROTOPLAST DURING MATURATION OF PINE TRACHEIDS

The protoplast of maturing axial tracheids in the secondary xylem of shortleaf pine (Pinus echinata Mill.) was studied by transmission and scanning electron microscopy. The mature protoplast is differentiated into two interconnected components: (1) the commonly observed peripheral layer lining the secondary cell wall, and (2) an elaborate reticulum of cytoplasmic filaments and placoids within the central vacuole. The reticulum provides an extensive surface area of vacuolar membranes for rapid exchange of nutrients and metabolites with the vacuolar sap, which is envisaged to function as a vital medium during the period of secondary cell wall synthesis. The breakdown of the protoplast which terminates tracheid maturation is associated with poorly defined alterations of the vacuolar membranes. This is indicated by increased formation of cytoplasmic spherules and membraneous vesicles which may be portions of separated vacuolar membrane during early stages of degradation. Autolysis is supposed to occur when the cytoplasm is exposed to the vacuolar sap after rupture and separation of the vacuolar membranes. The Gomori acid phosphatase technique as combined with electron microscopy produced no evidence of autolysosomal segresomes in strands of intravacuolar reticulum of the cytoplasm.     

STUDIES ON THE HUMAN CORPUS LUTEUM : II. Observations on the Ultrastructure of Luteal Cells During Pregnancy

The ultrastructure of human corpora lutea obtained during the 6th, 10th, 16th, and 35th week of pregnancy is reported. Differences between the established luteal cell of pregnancy and the transitory luteal cell of the menstrual cycle are noted. In pregnancy the luteal cell is more compartmentalized into a peripheral mass of ER (endoplasmic reticulum) and a central area where mitochondria and Golgi complexes are concentrated. The latter area extends to a cell surface where microvilli face on a perivascular space. Long bundles of filaments are prominent within the luteal cell cytoplasm and, in contiguous cells, appear to arise from adjacent desmosomal regions. Bilateral subsurface cisternae of granular ER at lateral cell borders appear to be areas of specialized junctional surfaces. Certain luteal cells with irregular nuclear membranes are also characterized by vesicular aggregates enclosed within a single membrane. These aggregates are found within the peripheral nucleoplasm or the perinuclear cytoplasm. Their single limiting membrane often appears continuous with either the inner or outer leaflet of the nuclear membrane.     

Fine structure of smooth muscle and neuromuscular junctions in the optic tentacles of Helix aspersa and Limax flavus

Summary The smooth muscle cells studied contain a central core of thick and thin myofilaments surrounded by a peripheral layer of myofilament-free cytoplasm. Numerous vesicles, tubules, microfilaments, mitochondria and fine granules are present in the peripheral cytoplasm. Glycogen particles are distributed in large or small groups in both the peripheral cytoplasm and among the myofilaments. In contracted muscle cells the peripheral cytoplasm bulges out at regular intervals into the intercellular connective tissue. Numerous close contacts between single, usually naked, axons and these cytoplasmic protrusions occur. The axons at these contacts contain numerous small (500 Å in diameter) and large vesicles (800–1000 Å in diameter). Sometimes a number of axons simultaneously form close contacts with a muscle cell. These close contacts are considered to be the sites at which transmitter is released and acts on the muscle cell membrane.I wish to thank Professor G. Burnstock for making laboratory facilities available. This work has been supported by the Australian Research Grants Committee.     

ULTRASTRUCTURE OF THE SECONDARY PHLOEM OF TILIA AMERICANA

Summer and winter (July and January) samples of secondary phloem of Tilia americana were studied with the electron microscope. Parenchyma cells contain: nuclei, endoplasmic reticulum, ribosomes, plastids, mitochondria and occasional dictyosomes. Well-defined tonoplasts separate vacuoles from cytoplasmic ground substance. Vacuoles often contain tannins. Lipid droplets are common in cytoplasm. Endoplasmic reticulum–connected plasmodesmata are aggregated in primary pit fields. Companion cells differ from parenchyma cells in having numerous sieve-element connections, possibly slime, and in lacking plastids. Mature, enucleate sieve elements possess 1–4 extruded nucleoli. Numerous vesicles occupy a mostly parietal position in association with plasmalemma. The mature sieve element lacks endoplasmic reticulum, organelles (except for few mitochondria) and tonoplast. In OsO_4– and glutaraldehyde-fixed elements, slime has a fine, fibrillar appearance. Normally, these fine fibrils are organized into coarser ones which form strands that traverse the cell and the plasmalemma-lined pores of sieve plates and lateral sieve areas.     

Ultrastructural investigation of spermiogenesis in Peripatopsis capensis (Onychophora)

Early spermatids of the onychophoran Peripatopsis capensis are spherical cells with a centrally located nucleus, numerous mitochondria, Golgi complexes, microtubules and two centrioles. During spermiogenesis, Golgi vesicles migrate to one side of the cell where they form a tight aggregate, which is later shed. The mature spermatozoon has no acrosome. Several mitochondria fuse to form a middle piece containing three large mitochondria. Nucleus and middle-piece elongate, presumably under the influence of helically twisted microtubules. Outside this set of microtubules a continuous layer of endoplasmic reticulum cisternae is formed which separates the interior portion of the cell from an external cytoplasmic rim, which is later shed. Outside the 9 + 2 complex, the tail presents nine accessory microtubules, and a peripheral layer of microtubules beneath the plasma membrane. The enforcement of the tail structure may be related to the fertilization biology of this animal, which is by “hypodermal” impregnation.