Electron microscopy of gametangial interaction and oospore development in Phytophthora capsici

Gametangial development and oospore formation were studied, with emphasis on cell wall morphogenesis, on mated cultures (A¹xA²) of Phytophthora capsici. In this species, the oogonial and antheridial hyphae interact to produce a typical amphigynous antheridium. The following developmental steps were recognized: 1) contact between oogonial and antheridial initials; 2) penetration of the antheridial initial by the oogonial initial; 3) reemergence of the oogonial initial; 4) oogonial expansion; 5) gametangial delimitation and oogonial wall thickening; 6) penetration of the oogonium by the antheridial fertilization tube; 7) oosphere formation; 8) periplasm degeneration and outer oospore wall formation; and 9) inner oospore wall formation. Electron micrographs were obtained of steps 3–9. Steps 1 and 2 were reconstructed from subsequent events. Steps 3–6 are stages of active wall formation with clear indication of intensive dictyosome activity leading to the formation of numerous wall-destined vesicles of two different sizes and electron densities. No vesicles were seen associated with the development of the inner oospore wall; however, by this stage of development the oosphere cytoplasm exhibited an overall intense electron density that obscured fine detail. Cytoplasmic appearance changed enormously during differentiation, from a developing oogonium rich in mitochondria, ribosomes, rough endoplasmic reticulum, dictyosomes and their vesicles, through an oosphere filled with large finger-print vacuoles and lipid-like bodies, to a mature oospore with a large central vacuole (ooplast) surrounded by a cortex of numerous lipid-like bodies; other organelles are confined to the interstitial space between these storage bodies.     

An electron microscopic observation of conidium and hypha of Erysiphe graminis hordei

Summary The fine structure of conidia and hyphae ofErysiphe graminis hordei, attacking leaves of barley, were investigated. The cell walls of conidia and hyphae were relatively thin and consisted of two layers, the inner and outer layers. The surface of conidia was not smooth and the thickness of cell walls was irregular. A nucleus, mitochondria, endoplasmic reticula and vacuoles in plasma were identified. The vacuoles in conidia were tightly packed with fine granules. Such granules in vacuoles, however, were not observed in hyphal cells.A lamellar structure was located in conidia, but not in hyphal cells. This structure may be specific in conidia of this fungus, but its function is not yet known. Many glycogen granules were observed in endoplasm of conidia, which were scattered or congregated in groups. In hyphae, however, they were extremely few. Hyphal septa were connected directly with the inner layer of cell walls. These had simple septal pore. The Woronin bodies were detected in the endoplasm in the vicinity of hyphal septa.Contribution No. 192.     

Consumption of lipid granules and formation of vacuoles in the pollen tube ofTradescantia reflexa

Summary The ultrastructure in pollen tubes ofTradescantia reflexa was studied with special attention to the consumption of lipid granules and the formation of vacuoles. Electron dense, thin vesicles (EDTV) were developed from the small spherical vesicles. ER-associated lipid granules attached to both surfaces of the EDTV. Then, the EDTV became bottle-shaped, surrounding a part of cytoplasm. In the compartment surrounded by the membranes of EDTV, lipid granules were decomposed and finally disappeared. Protuberances were formed at the terminals of the expanded membranes of the EDTV and at the delimiting membranes of the compartment. These protuberances were pinched off from the membranes to form vesicles. These vesicles were transported from the site of origin to destinations in the pollen grain where they fused with each other to form vacuoles.Abbreviation EDTV electron dense, thin vesicle(s)     

Über die Entwicklung des marinen parasitischen PhycomycetenLagenisma coscinodisci (Lagenidiales)

This paper concentrates on the study of vegetative development and sexual reproduction inLagenisma coscinodisci Drebes. Before infecting a diatom cell (Coscinodiscus granii), the freshly released zoospores pass through two different cyst stages. The primary zoospores are kidney-shaped and laterally biflagellated. They form a primary cyst with a spiny cyst wall which is left by isomorphic secondary zoospores. The latter form a secondary cyst (sometimes perhaps repeatedly), which is smooth-walled. The secondary cyst germinates and infects a new diatom cell by means of an infecting tube which enters the cell through the gap between epi- and hypotheca and develops a new thallus. Sexual reproduction is induced by ageing of cultures. Two kinds of isomorphic, kidney-shaped, laterally biflagellated swarmers are produced as in zoosporogenesis. Female-determined swarmers settle down near the host cell and encyst with a more or less smooth wall (oogonia). Male-determined swarmers are obviously attracted by the oogonia and encyst close to them to form a more or less smooth-walled antheridium which drives a thin fertilization tube to the oogonium. During plasmogamy the oogonium develops a thick, short hypha. The cytoplasm with the two nuclei moves completely into this hypha, concentrates near the hyphal tip, and surrounds itself with a thick wall to become a resting spore (oospore) in which karyogamy takes place. The walls of cysts, tubes, hyphae and spores react positively with zinc-chlor-iodide. In the spines and walls of the primary cysts the network of 2 to 3 nm thick fibrils is more distinct than in the other walls.     

A LIGHT- AND ELECTRON-MICROSCOPIC STUDY OF PRIMARY HETEROGENEITY IN THE EGGS OF TWO BROWN ALGAE

The mature eggs of Zonaria farlowii and Dictyota binghamiae exhibit a distinctively symmetrical arrangement of organelles. In mature oogonia plastids occur in two groups in the central region of the cell and vacuoles of several types are arranged in peripheral layers. Before the mature egg is released, an amorphous “mucilage layer” developes inside the wall of the oogonium. After fertilization the plastids become uniformly distributed. When the eggs of Zonaria develop parthenogenetically the primary heterogeneity is retained. The symmetrical arrangement of membranes seen in the oocytes of these plants may represent an organizing system that influences cytodifferentiation and perhaps subsequent embryology.     

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.     

Ultrastructure and cytochemical localization of acid phosphatase of laticifers in Euphorbia kansui Liou

Acid phosphatase (AcPase) activities are involved in the degeneration process of cytoplasm in plants. In this study, acid phosphatase was detected by the method of lead nitrate and cytochemical electron microscopy during the development of nonarticulated laticifers in Euphorbia kansui Liou. The most important feature in the differentiation of the laticifers in E. kansui is that the development of small vacuoles arises from endoplasmic reticulum (ER). The mature laticifers possess a thin layer of electron-dense peripheral cytoplasm in which the organelle cannot be distinguished and a large central vacuole filled with latex particles. AcPase cytochemistry studies show AcPase reaction products congregated into heaps are distributed along the tonoplast of central vacuole and around the mitochondria and plastids. Some small vacuoles which develop at later developmental stages of laticifers contain AcPase reaction products. As a result, the central vacuole is formed by cellular autophagy and fusion of small vacuoles which apparently arises from ER.     

An observation on fine structure of conidia of sphaerotheca pannosa (wallr.) lév. attacking leaves of roses

Summary Fine structures of conidia ofSphaerotheca pannosa, the causal fungus of powdery mildew of rose plants were investigated. The cell wall of conidia was relatively thin and consisted of two layers. Nuclei, mitochondria, endoplasmic reticula and vacuoles were identified in the conidia, and there were many unknown vesicles just inside the plasma membrane. Usually the conidia were uninucleate, but before the germination the nucleus divided into two. Vacuole held a number of osmiophilic globules which were located along the tonoplast, and in large magnifications they appeared as aggregation of small electron-transparent globules when fixed with KMnO₄ solution. In a germ tube one large mitochondrion and many endoplasmic reticula were found.Contribution from the Laboratory of Plant Pathology, Kyoto University, No. 174.     

Investigations on the hypothalamo-neurohypophysial neurosecretory system of the grass frog (Rana pipiens) after transection of the proximal neurohypophysis

Summary With the onset of degeneration of the neurosecretory nerve fibers following transection of the proximal neurohypophysis, the pituicytes phagocytize these nerve fibers. Concomitant with a considerable increase in the size of the pituicytes, which reaches a peak between 8 and 10 days after the transection, the following sequence of events can be observed: reduction of the amount of intergranular axoplasm, increase in the size of some granules, partial or total loss of the electron density of the neurosecretory granules, loss of granule membranes, fusion of some granules, polymorphous axonal content in digestion vacuoles, formation of multilamellate bodies, digestion vacuoles with moderately electron dense peripheral material, empty digestion vacuoles. At about 12 days after the transection many vacuoles appear which subsequently disappear as the pituicytes shrink. Free neurosecretory granules resulting from the disappearance of the axolemma remain intact in the intercellular and perivascular connective tissue spaces and are eventually phagocytized by pituicytes and pericytes.Phagocytosis is considered to be a basic function of pituicytes. The problems related to this function as well as the possible implications for the interpretation of Herring bodies are discussed.This investigation was supported by Grant No. NB-06641 of the National Institute of Neurological Diseases and Blindness. The technical assistance of Mrs. Mildred Floyd and Christa Cooper is gratefully acknowledged.Dedicated to Prof. Dr. H. Grau on the occasion of his 70th birthday.     

Histochemical and ultrastructural changes in the haustorium of date (Phoenix dactylifera L.)

Summary During imbibition ofPhoenix dactylifera embryos, all cotyledon cells show the same changes: protein and lipid bodies degrade, smooth endoplasmic reticulum (ER) increases in amount, and dictyosomes appear. At germination, the distal portion of the cotyledon expands to form the haustorium. At this time, epithelial cells have a dense cytoplasm with many extremely small vacuoles. Many ribosomes are present along with ER, dictyosomes, and mitochondria. The parenchyma cells have large vacuoles and a small amount of peripheral cytoplasm. Between 2 and 6 weeks after germination, epithelial cells still retain the dense cytoplasm and many organelles appear: glyoxysomes, large lipid bodies, amyloplasts, large osmiophilic bodies, and abundant rough and smooth ER which appear to merge into the plasmalemma. A thin electron-transparent inner wall layer with many small internal projections is added to the cell walls. Starch grains appear first in the subsurface and internal parenchyma and subsequently in the epithelium. Lipid bodies, glyoxysomes, protein, and osmiophilic bodies occur in the epithelial and subepithelial cell layers but not in the internal parenchyma. At 8 weeks after germination, the cytoplasm becomes electron transparent, vacuolation occurs, lipid bodies and osmiophilic bodies degrade, and the endomembranes disassemble. After 10 weeks, the cells are empty. These data support the hypothesis that the major functions of the haustorium are absorption and storage.     

腐霉属的一个新种和二个新记录

本文报告作者1982—1983年在北京和广东一些地区土壤中用已知方法(余永年,1975)分离到的几种腐霉,其中1个新种(Pythium borealis sp.nov.)、2个国内未报道的种(P.oligandrum和P.myriotylum)和1个已知种的变异株(P.ultimum variant)。文中对以上各菌进行了形态学描述。     

NUCLEAR MIGRATION AND ASYMMETRIC CELL DIVISION IN ONOCLEA SENSIBILIS SPORES: AN ULTRASTRUCTURAL AND CYTOCHEMICAL STUDY

A method of preparation for electron microscopy of fern spores in early stages of germination is presented. The cytochemistry and fine structure of Onoclea spores during the early stages of germination are described. The cytoplasm of the hydrated spore is filled with lipid droplets, protein granules and chloroplasts. During the early stages of development ribosomes and mitochondria increase in the area surrounding the central nucleus, and a new peripheral wall forms around the protoplast. Microtubules and large, branching mitochondria are associated with the nucleus during migration from its original central position in the spore to the proximal face and then to one end of the spore. There is no morphological polarization of cytoplasmic organelles of the spore before migration of the nucleus.     

Oogonial release in Turbinaria conoides (J. Agardh) Kützing (Fucales,Sargassaceae)

The oogonium in Turbinaria conoides (J. Agardh) Kürzing at the time of release is 8-nucleate and consists of 3 wall layers namely exochiton, mesochiton and endochiton. The exochiton contains alginic acid. The mesochiton a mixture of alginic acid and sulphated polysaccharides. The endochiton that is evident in the unreleased 8-nucleate oogonium, stains for sulphated polysaccharides, but is PAS negative. In a released oogonium, the endochiton is Alcian blue and PAS positive and consists of both alginic acid and sulphated polysaccharides.Polysaccharide granules are secreted near the perinuclear region and in thecytoplasmic vacuoles during the initiation of mesochiton. Furthermore, at the distal end the mesochiton froms a pad that fuses with the exochiton. The pad consists of alternate thick and thin bands. The exochiton opens at one side due to the swelling of the oogonium and accumulation of sulphated polysaccharides between exochiton and mesochiton followed by formation and elongation of a mesochiton stalk. The 8-nucleate oogonium is, thus, extruded from the conceptacle, but remains attached to the exochiton by means of a long mesochiton stalk. The secretory paraphyses, at the time of oogonial release, produce copious amounts of polysaccharides. The oogonium is, thus, extruded through the ostiole by the combined efforts of the 3 wall layers that are histochemically and histologically different, in combination with secretion produced by secretory paraphyses.     

ULTRASTRUCTURAL STUDIES OF PINUS PINASTER NEEDLES: THE ENDODERMIS

The endodermis in the needles of Pinus pinaster was examined with light and electron microscopy. The endodermis is composed of very long, radially flattened cells, filled with a large central vacuole, which contains spherical dense bodies whose concentration decreases from the ends of the cell to the middle part. They are individually surrounded by a fine granular matrix. The central vacuole is bounded by a thick tonoplast. Other small, clear vacuoles are limited by a thin tonoplast. The parietal cytoplasm contains relatively few ribosomes, long slender chloroplasts, and lipid bodies. The smooth endoplasmic reticulum is highly developed along the tangential walls and frequently connected, or apposed, to the plasma membrane. Numerous primary pit fields are seen in the radial walls which are lignified and in the tangential walls; the latter exhibit a characteristic loosening of the outer layer of the wall. The lipid bodies are connected to endoplasmic reticulum tubules. The role of the endodermis in the active transport of water inside the needle is discussed in reference to previous physiological studies. The chemical composition of the vacuolar dense bodies is as yet unknown.     

AN ULTRASTRUCTURAL STUDY OF SPERMATIUM FORMATION IN THE RUST FUNGUS GYMNOSPORANGIUM JUNIPERI-VIRGINIANAE

Spermatium formation in G. juniperi-virginianae is phialidic. The spermatia are blown out of the tips of spermatiophores which possess a thickened neck region and a distinct, flared collarette. Each spermatium initial is surrounded by a thin wall which is attached to the inner surface of the spermatiophore wall just below the thickened neck region. A spermatium is delimited by a centripetally developing septum and then pushed into the spermogonial cavity by the next spermatium initial. Mature spermatia are ellipsoid with tapered ends and are surrounded by a thin wall. Each contains a single nucleus, many ribosomes, a few small vacuoles, and a number of lipid bodies and mitochondria.     

Electron microscopic observations on the involution of the human corpus luteum of menstruation

Summary The involution of the granulosa lutein cell in the human corpus luteum is characterized by a dilatation of agranular endoplasmic reticulum vesicles and tubules. This process continues until the whole cell is filled with large vacuoles and the cytoplasm is reduced to thin strands between the vacuoles. The contents of the latter are of low electron density in contrast to the very electron dense lipid droplets in vascularization, bloom and early involution phase. Light microscopical evidence shows that the contents of the vacuoles must be lipid and the lower electron density might be explained by the relative decrease in phospholipids and increase in cholesterol and cholesterol esters during involution. Simultaneously processes of focal cytoplasmic degradation resulting in autophagic vacuoles occur in the cells. These lead in some cases to the formation of residual bodies which can be identified with lipofuscin granules. Finally, the degenerating cells disintegrate and part of the debris, including the lipofuscin granules are phagocytosed by macrophages, the so-called fluorocytes of Hamperl. During involution an amorphous substance with some protofilaments and collagen fibrils is deposited in the spaces between the shrinking lutein cells. This is the fibrohyalin material which will form the bulk of the corpus albicans.We are grateful for the assistance given by Dr. J. M. Moyes of the Women's Hospital, Crown Street, Sydney and the staff of King George V. Hospital at Sydney with the supply of the material.     

成年草鱼外周血细胞的超微结构

用透视电镜技术研究了成年草鱼外周血细胞的超微结构，结果表明：在外周血细胞中可区分出红细胞，淋巴细胞，单核细胞，嗜中性白细胞，嗜酸性白细胞和血检细胞；嗜碱性白细胞无论在血涂片上或超薄切片上都没有发现。电镜图像显示，在红细胞中，仅能看到少数线粒体和液泡。淋巴细胞以短的伪足，较多的游离核糖体和滑面内质网为其特征。单核细胞的特征是具有较多的伪足和胞质液泡以及偏位核。在外周血液中发现了嗜中性白细胞生长、发育、功能成熟和衰退的全过程，描述了嗜中性白细胞的幼稚型、成熟型和衰退型细胞的超微结构。在成年草鱼外周血中，还发现了一种新型的颗粒细胞，它的特殊颗粒为大的六角形或棒状致密结晶颗粒，对上述特殊颗粒细胞的属性也进行了讨论。     

The fine structure of the liver cells in the bat (Myotis myotis) during hibernation,arousal and forced feeding

Summary The ultrastructure of liver cells was studied in three groups of bats (Myotis myotis) captured in March. 1. Hibernating animals: The liver cells contain much glycogen and large mitochondria, poorly developed ER, relatively well developed Golgi apparatus, various amounts of lysosomes. Most of the bile canaliculi are closed. 2. Non-hibernating, starving animals: 24 hours after arousal the glycogen and lipid droplets disappear from the liver cells, the mitochondria swell slightly. There is no essential alteration in the ER. In the liver cells of the starving animals numerous autophagic vacuoles appear including disintegrated cytoplasmic components. 3. Non-hibernating force-fed animals: They were given food rich in fat and protein, containing sugar and a drug increasing bile secretion. Within an hour, glycogen and lipid reappears in the liver cells, autophagic vacuoles disappear, mitochondria become larger. After feeding, the Golgi apparatus hypertrophies considerably, many bile canaliculi open, the number of the peribiliary lysosomes decreases.This paper is dedicated to Professor W. Bargmann on the occassion of his 60th birthday.     

Gametogenesis and auxospore development in actinocyclus (bacillariophyta)

cGametogenesis and auxospore development have been studied in detail in surprisingly few centric diatoms. We studied the development of sperm, eggs and auxospores in Actinocyclus sp., a radially symmetrical freshwater diatom collected from Japan, using LM and electron microscopy of living cultures and thin sections. Actinocyclus represents a deep branch of the 'radial centric' diatoms and should therefore contribute useful insights into the evolution of sexual reproduction in diatoms. Spermatogenesis was examined by LM and SEM and involved the formation of two spermatogonia (sperm mother-cells) in each spermatogonangium through an equal mitotic division. The spermatogonia produced a reduced 'lid' valve, resembling a large flat scale with irregular radial thickenings. Sperm formation was merogenous, producing four sperm per spermatogonium, which were released by dehiscence of the 'lid' valve. The sperm were spindle-shaped with numerous surface globules and, as usual for diatoms, the single anterior flagellum bore mastigonemes. One egg cell was produced per oogonium. Immature eggs produced a thin layer of circular silica scales before fertilization, while the eggs were still contained within the oogonium. Sperm were attracted in large numbers to each egg and were apparently able to contact the egg surface via a gap formed between the long hypotheca and shorter epitheca of the oogonium and a small underlying hole in the scale-case. Auxospores expanded isodiametrically and many new scales were added to its envelope during expansion. Finally, new slightly-domed initial valves were produced at right angles to the oogonium axis, after a strong contraction of the cell away from the auxospore wall. At different stages, Golgi bodies were associated with chloroplasts or mitochondria, contrasting with the constancy of Golgi-ER-mitochondrion (G-ER-M) units in some other centric diatoms, which has been suggested to have phylogenetic significance. Electron-dense bodies in the vacuole of Actinocyclus are probably acidocalcisomes containing polyphosphate.     

Phosphate availability affects the tonoplast localization of PLDzeta2, an Arabidopsis thaliana phospholipase D

Under phosphate deprivation, higher plants change their lipid composition and recycle phosphate from phospholipids. A phospholipase D, PLDzeta2, is involved in this recycling and in other cellular functions related to plant development. We investigated the localization of Arabidopsis PLDzeta2 by cell fractionation and in vivo GFP confocal imaging. AtPLDzeta2 localizes to the tonoplast and the Nter regulatory domain is sufficient for its sorting. Under phosphate deprivation, AtPLDzeta2 remains located in the tonoplast but its distribution is uneven. We observed PLDzeta2-enriched tonoplast domains preferentially positioned close to mitochondria and beside chloroplasts. In absence of PLDzeta2, membrane developments were visualized inside vacuoles.