Sex pheromone gland of the female European corn borer moth,Ostrinia nubilalis (Lepidoptera,Pyralidae): ultrastructural and biochemical evidences

The sex pheromone gland of the female European corn borer moth, Ostrinia nubilalis was studied using light and electron microscopy. The pheromone gland is formed by hypertrophied epidermal cells at the mid-dorsal region of the intersegmental membrane between abdominal segments 8 and 9/10. Active glandular cells contain extensive apical membrane foldings, a single nucleus, many free ribosomes, numerous mitochondria, microtubules and lipid droplets. Smooth endoplasmic reticulum is scanty. In young moths, the glandular cells are smaller in size, the microvilli at the apical membrane are poorly developed and the cytoplasm contains fewer mitochondria, microtubules, and no lipid droplets. The surrounding unmodified epidermal cells are small cuboidal or squamous cells. These cells have ill-defined apical membrane foldings and do not contain lipid droplets in the cytoplasm and the overlying cuticle. Fatty acids analyses revealed the presence of the sex pheromone components, (E)-11-tetradecenyl acetate, and their immediate precursors, methyl (E)-11- and methyl (Z)-11-tetradecenoate, only in the dorsal portion of the cylindrical intersegmental membrane. Results of the present study show that the sex pheromone gland of O. nubilalis is restricted to the dorsal aspect of the intersegmental membrane between segments 8-9/10 and is not a ring-gland.     

An autoradiographic,biochemical, and morphological study of the harderian gland of the mouse

Biochemical and morphological properties of the Harderian gland of the mouse were examined by combining autoradiographic, biochemical, and electron microscopic techniques. Autoradiographs show that the radioactive carbon from [U-¹⁴C]glucose injected into the abdominal cavity is completely incorporated into the acid-insoluble substances within 30 minutes. The results of chemical analysis show that the main components of this gland are glyceryl ether diesters and phospholipids. Scanning electron microscopy shows numerous lipid droplets in the secretory cells and alveolar lumina. Myoepithelial cells lie between the secretory cell base and the basement membrane and have a basket-like distribution of processes as confirmed by hydrochloric acid and collagenase digestions. Myofilaments are demonstrated in the cytoplasm. Two types of secretory cells (A and B) comprise the alveolar epithelium and can be differentiated under the electron microscope. The cytoplasm of both contains numerous vacuoles. The vacuoles are almost empty in A cells, which are a more numerous constituent of the alveolar epithelium than B cells. However, the vacuoles of the B cells contain densely osmiophilic material. In both, cell types show a merocrine mode of secretion. Unmyelinated nerve cell endings occur in the interstices of the connective tissue, and contain clear or cored vesicles.     

Cotton embryogenesis: The pollen cytoplasm

Summary The ultrastructure and composition of cotton (Gossypium hirsutum) pollen, exclusive of the wall, was examined immediately before and after germination. The pollen grain before germination consists of two parts: the outer layer and a central core. The outer layer contains large numbers of mitochondria and dictyosomes as well as endoplasmic reticulum (ER). The core contains units made of spherical pockets of ER which are lined with lipid droplets and filled with small vesicles; the ER is rich in protein and may contain carbohydrate while the vesicles are filled with carbohydrate. Starch-containing plastids are also present in the core as are small vacuoles. The cytoplasm of the pore regions contains many 0.5 spherical bodies containing carbohydrate. After germination the ER pockets open and the lipid droplets and small vesicles mix with the other portions of the cytoplasm. With germination the pore region becomes filled with mitochondria and small vesicles. The vegetative nucleus is large, extremely dense and contains invaginations filled with coils of ER. A greatly reduced nucleolus is present in the generative cell which is surrounded by a carbohydrate wall. The cytoplasm of the generative cell is dense and contains many ribosomes, a few dictyosomes and mitochondria, many vesicles of several sizes, and some ER. No plastids were identified. The generative nucleus is also dense with masses of DNA clumped near the nuclear membrane. An unusual tubular structure of unknown origin or function was observed in the generative cell.     

Ultrastructure of the perfused rat epididymis: Effect of luminal sodium ion concentration

Summary The appearance of the rat epididymal epithelium changed when it was perfused in vivo through the lumen with unphysiologically high sodium ion concentrations; dilatation of intercellular spaces (ICS) at threshold concentrations of 30mM-Na⁺ in the cauda and about 55mM-Na⁺ in the corpus was associated with absorption of water from the lumen. Despite the distended ICS, junctional complexes appeared intact, and their integrity was confirmed by the exclusion of luminal horseradish peroxidase (HRP) from the ICS, and by demonstrating that circulating [³H]inulin did not enter the lumen. Smooth ER and lipid droplets in the principal cells of the corpus epididymidis were well maintained, and the preservation of granular ER in principal cells of the cauda epididymidis lent morphological support to the continued secretion of protein in this segment. However, occasional distension or involution of inner Golgi cisternae was evident in principal cells after 3–6 h perfusion. In contrast to multivesicular bodies of principal cells, the apical and basal vacuoles characteristic of clear cells changed in size with different perfusing solutions. When low Na⁺ concentrations were perfused large translucent vacuoles were frequently found in the apical cytoplasm of clear cells in the corpus and cauda epididymidis, and filled vacuoles became larger and showed a decrease in content density in the cauda epididymidis. These large vacuoles were absent from tissue perfused with high Na⁺ concentrations. Normal pinocytotic activity of both cell types was demonstrated by perfusing HRP which was taken up by the normal route in principal cells, with some transfer to the Golgi cisternae. By far the most HRP was accumulated in clear cell vacuoles irrespective of the composition of the perfusing solution.     

Ultrastructure ofCatharanthus roseus cells culturedin vitro and exposed to conditions for alkaloid accumulation

Summary Periwinkle (Catharanthus roseus) cells cultured in 1-B 5 medium display the ultrastructure of parenchyma cells. The parenchyma character remained unchanged when cells were exposed to any one of three different conditions effecting alkaloid accumulation. Transfer of cells to alkaloid production medium for 2 weeks (condition 1) accorded two special features,i.e., unusually big lipid droplets in the cytoplasm and, upon fixation, one or several electron-dense droplets of spongy precipitate in vacuoles. Among hormone-autotrophic cultures (condition 2) some cells showed a fine electron-dense vacuolar precipitate. Addition ofPhythium homogenate (fungal elicitor) to cells cultured in 1-B 5-medium for 10 days (condition 3), cells showed a frequent appearance of singular big lipid droplets in the cytoplasm, whereas vacuoles remained devoid of precipitate. The appearance of big lipid droplets and of vacuolar precipitate is interpreted as progressing cytodifferentiation, but is coincidental with alkaloid accumulation.NRCC no. 24524.     

Ultrastructural changes in the epidermis of petals of the sweet orange infected by <Emphasis Type="Italic">Colletotrichum acutatum</Emphasis>

Postbloom fruit drop (PFD) is an important disease caused by the fungus Colletotrichum acutatum. PFD is characterised by the formation of necrotic lesions on the petals and stigmas of flowers as well as premature abscission of the fruit in Citrus spp. We compare the ultrastructure of the epidermis of uninoculated Citrus sinensis petals with that of petals inoculated with the fungus to understand the changes that occur upon C. acutatum infection. Healthy petals have a cuticle with parallel striations covering the uniseriate epidermis. This pattern consists of vacuolated parietal cells whose cytoplasm contains mitochondria, plastids with an undeveloped endomembrane system and a slightly dense stroma, a poorly developed rough endoplasmic reticulum, polysomes, few lipid droplets, and a nucleus positioned near the inner periclinal wall. In damaged regions, the cytoplasm of some cells is densely packed with well-developed endoplasmic reticulum, a large number of hyperactive dictyosomes, numerous mitochondria, and many lipid droplets. The plastids have an electron-dense stroma, starch grains, and a large amount of electron-dense lipid droplets, which can be released into vacuoles or the endoplasmic reticulum. Multivesicular bodies and myelin bodies are frequently observed in the vacuole, cytoplasm, and periplasmic space. Vesicles migrate through the cell wall and are involved in the deposition of cuticular material. In the later stages of infection, there is deposition of new cuticle layers in plaques. The outer periclinal walls can be thick. These observations indicate that epidermal cells respond to the pathogen, resulting in cuticular and parietal changes, which may limit further infection.     

On the histology and ultrastructure of the Harderian gland in rabbits

Summary The Harderian gland of rabbits has been studied with light and electron microscopes. The red part contains relatively wide alveoli with an irregular cuboidal epithelium. The stainability of the cytoplasm is poor. The white part has smaller alveoli with a low columnar epithelium. The cells show cytoplasmic basophilia removable with ribonuclease. The cytoplasm of both kinds of cells is very dense when examined in the electron microscope. The mitochondria show branched, closely packed cristae and a dense matrix. The Golgi apparatus displays few lamellae and rows of vacuoles. The endoplasmic reticulum is very finemeshed and partly associated with ribonucleoprotein particles. Both kinds of cells contain numerous lipid droplets, leaving vacuoles in the sections prepared for electron microscopy. They are fewer but distinctly larger in the red part. In both lobes pictures suggesting a secretion of lipid droplets have been observed. Cells showing signs of degeneration with subsequent discharge of the detritus have been observed in both lobes, but this process does not correspond to the holocrine secretion in sebaceous glands. Likewise, no apocrine secretion was observed.     

An Ultrastructural Study of the Hemocytes of the Pericardial Body in the Ascidian Ciona intestinalis (L.)

Abstract The hemocytes of the pericardial body of Ciona intestinalis were studied by electron microscopy. Our findings showed that stem cells, clear vesicular granulocytes, microgranulocytes, unilocular granulocytes and globular granulocytes are present at the periphery of the smaller-sized pericardial bodies. The stem cells are small round cells with a large nucleus, with or without nucleolus, and homogeneous cytoplasm containing numerous ribosomes. The clear vesicular granulocytes are characterized by an ameboid shape and cytoplasm containing several large electron-lucent vacuoles and small electron-dense granules. The microgranulocytes are variable in shape and contain numerous large electron-dense granules. The unilocular granulocytes show a single large vacuole with an electron-dense or electron-lucent content and a thin layer of peripheral cytoplasm that contains the flattened nucleus. The globular granulocytes are characterized by the presence of large vacuoles containing either fibrogranular material or electron-dense aggregates.     

Morphology of the air-breathing stomach of the catfish Hypostomus plecostomus

Histological and ultrastructural investigations of the stomach of the catfish Hypostomus plecostomus show that its structure is different from that typical of the stomachs of other teleostean fishes: the wall is thin and transparent, while the mucosal layer is smooth and devoid of folds. The epithelium lining the whole internal surface of the stomach consists of several types of cells, the most prominent being flattened respiratory epithelial cells. There are also two types of gastric gland cells, three types of endocrine cells (EC), and basal cells. The epithelial layer is underlain by capillaries of a diameter ranging from 6.1-13.1 microm. Capillaries are more numerous in the anterior part of the stomach, where the mean number of capillary sections per 100 microm of epithelium length is 4, compared with 3 in the posterior part. The cytoplasm of the epithelial cells, apart from its typical organelles, contains electron-dense and lamellar bodies at different stages of maturation, which form the sites of accumulation of surfactant. Small, electron-dense vesicles containing acidic mucopolysaccharides are found in the apical parts of some respiratory epithelial cells. Numerous gastric glands (2 glands per 100 microm of epithelium length), composed of two types of pyramidal cells, extend from the surface epithelium into the subjacent lamina propria. The gland outlets, as well as the apical cytoplasm of the cells are Alcian blue-positive, indicating the presence of acidic mucopolysaccharides. Zymogen granules have not been found, but the apical parts of cells contain vesicles of variable electron density. The cytoplasm of the gastric gland cells also contains numerous electron-dense and lamellar bodies. Gastric gland cells with electron-dense cytoplasm and tubulovesicular system are probably involved in the production of hydrochloric acid. Fixation with tannic acid as well as with ruthenium red revealed a thin layer of phospholipids and glycosaminoglycans covering the entire inner surface of the stomach. In regions of the epithelium where the capillaries are covered by the thin cytoplasmic sheets of the respiratory epithelial cells, a thin air-blood barrier (0.25-2.02 microm) is formed, thus enabling gaseous exchange. Relatively numerous pores closed by diaphragms are seen in the endothelium lining the apical and lateral parts of the capillaries. Between gastric gland cells, solitary, noninnervated endocrine cells (EC) of three types were found. EC are characterized by lighter cytoplasm than the surrounding cells and they contain dense core vesicles (DCV) with a halo between the electron-dense core and the limiting membrane. EC of type I are the most abundant. They are of an open type, reaching the stomach lumen. The round DCV of this type, with a diameter from 92-194 nm, have a centrally located core surrounded by a narrow halo. EC of type II are rarely observed and are of a closed type. They possess two kinds of DCV with a very narrow halo. The majority of them are round, with a diameter ranging from 88-177 nm, while elongated ones, 159-389 nm long, are rare. EC of type III are numerous and also closed. The whole cytoplasm is filled with large DCV: round, with a diameter from 123-283 nm, and oval, 230-371 nm long, both with a core of irregular shape and a wide, irregular halo. EC are involved in the regulation of digestion and probably local gas exchange. In conclusion, the thin-walled stomach of Hypostomus plecostomus, with its rich network of capillaries, has a morphology suggesting it is an efficient organ for air breathing.     

Microscopic anatomy of the orbital Harderian gland in the common tree shrew (Tupaia glis)

The orbital Harderian gland of the common tree shrew (Tupaia glis) was investigated at the macroscopic and microscopic levels. In the glands of both sexes only one acinar cell type was found. The cell is characterized by the presence of numerous lipid vacuoles of variable size and by a small number of PAS-positive, electron-dense granules distributed throughout the cytoplasm, which are predominant at the basal portion of each acinar cell. The duct system is well developed within the gland. The content of lipid vacuoles within the acinar cells is secreted from the apical portions by exocytosis, indicating the exocrine function of the organ. Apart from the lipid vacuoles, both acinar and ductal luminal contents of the Harderian gland also contain accretion of electron-dense materials. The vascularization within the Harderian gland is unique in that two capillary types (small fenestrated and irregular sinusoidal capillaries) could be demonstrated. The presence of fenestrated capillaries together with other morphological features (such as accumulation of the small electron-dense granules at the basal pole and the presence of basolateral microvilli) near the basal portion of the acinar cells suggest that the Harderian gland in T. glis might also be involved in an endocrine function.     

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.     

Cytochemical observations concerning the formation,release, and transport of lipid secretory products in the interstitial (thecal) cells of the rabbit ovary

Summary The release of lipid droplets from the ovarian interstitial gland cells of thecal origin into the circulating blood has been studied by cytochemical methods. Estrous, preovulatory, and postovulatory ovaries of rabbits were used. Ovulation was induced by human chorionic gonadotropin (HCG) administration. The cytoplasm in the gland cells of estrous ovaries is filled with lipid droplets consisting of cholesterol or its esters, triglycerides, and some phospholipids. Mitochondria, Golgi zone, and diffuse lipoproteins are well differentiated. The lipid droplets decrease in interstitial gland cells of preovulatory ovaries stimulated with HCG. The release of lipid droplets by the formation of vacuoles is closely accompanied by a considerable loss of cytoplasm and its organelles; consequently the cells are reduced in size. Degenerating gland cells do not release their lipids because they are refractory to gonadotropic stimulation. The released secretory products are found in the form of discrete bodies between gland cells, in regions adjacent to blood vessels, and in the lumen of the latter. The mechanism by which the liberated lipids are transported into the circulation could not be determined. The depletion of lipid droplets is clearly related with the production of 20a-OH steroid (20a-hydroxy-pregn-4-en-3-one) and progesterone studied by other workers.The replenishment of cytoplasm and its organelles, and the formation and storage of secretory lipid granules have also been studied both in the preovulatory and postovulatory ovaries. The organelles could not be seen to be visibly related to lipid synthesis.     

Dufour gland of the digger wasp<Emphasis Type="Italic"> Liris niger:</Emphasis> structure and developmental and biochemical aspects

The tubiform Dufour gland in the digger wasp species Liris niger is about 1.0 mm long ( 0.15 mm). An alternating arrangement of longitudinal and circumferential bundles of striated muscle fibers surrounds the gland. The Dufour gland, together with the venom gland, enters the sting base and terminates in the sting. The glandular epithelium is monolayered. Glands about 3 day after imaginal ecdysis have an empty lumen but a thick lining epithelium. The gland cells are characterized by a well-developed vesicular smooth endoplasmic reticulum, sparse rough ER and numerous free ribosomes. They also exhibit several electron-lucent vesicles and autophagic vacuoles. Secretion of electron-dense material via the gland cuticle into the gland lumen is apparent. Glands more than 20 days after imaginal ecdysis display a large lumen and a thin epithelium. The cells show signs of degeneration with numerous cytolytic inclusions. Dufour gland liquid contains numerous polypeptides of molecular weights ranging from 14 to about 200 kDa. In addition the secretion consists predominantly of straight-chain hydrocarbons, accompanied by small amounts of esters. The major hydrocarbons are pentadecane and (Z)-8-heptadecene. Dufour gland secretion may have several functions: (1) the polypeptides might be involved in the gluing process of the eggs, while (2) the hydrocarbon oils may function as lubricants for the lancets and (3) might soften the secretion, thus allowing easier application of the glue. The lipophilic volatile material (4) might also be involved in pheromonal signaling.     

The formation of glandular secretion in larval Austramphilina elongata (Amphilinidea)

The ultrastructure of three types of gland cells of embryos and free-swimming larvae of Austramphilina elongata is described. Type I gland cells contain large, more or less round electron-dense granules which are formed by numerous Golgi complexes. Type II gland cells contain thread-like, membrane-bound secretory granules with longitudinally arranged microtubules inside the granules; secretory droplets are produced by Golgi complexes and the microtubules apparently condense in the cytoplasm or in the droplets. Type III gland cells contain irregular-ovoid membrane-bound granules with coiled up microtubules which have an electron-dense core; the granules are formed by secretionderived from Golgi complexes and the microtubules aggregate around and migrate into the secretion; microtubules are at first hollow and the early secretory granules have a central electron-dense region.     

Morphology of the bovine epididymis

The epididymis of the bull was divided into six regions, and morphological differences between regions were studied. The epithelium of all regions contained four cell types: principal and basal epithelial cells, and intraepithelial lymphocytes and macrophages. The epithelium of regions II-V also contained a few apical cells. Principal cells of all regions possessed an endocytotic apparatus including stereocilia underlain by canaliculi, coated vesicles, and subapical vacuoles (up to 1 micron in diameter); however, large vacuoles with a flocculent content and multivesicular bodies (up to 5 microns in diameter) were most numerous in regions II, III, and IV. The unique features of principal cells of region I were the presence of well-developed Golgi bodies, few lipid droplets, and whorls of smooth endoplasmic reticulum in the supranuclear cytoplasm. Numerous mitochondria, distended cisternae of rough endoplasmic reticulum, and dense granules characterized the infranuclear cytoplasm of the principal cells of regions II-VI; however, these features were more developed in region V. Apical cells were characterized by the apical location of the nucleus, many mitochondria in the apical cytoplasm, and few microvilli at the luminal border. Basal cells with few cytoplasmic lipid droplets were present throughout the length of the epididymis but appeared more numerous in region V. Intraepithelial lymphocytes were present at all levels of the epithelium but were never seen in the lumen. Intraepithelial macrophages containing heterogeneous granules, eccentric nuclei, and pseudopods were invariably seen near the basal area of the epithelium in all regions. These observations are discussed in an effort to define the role of each cell type in the epididymal epithelium.     

Peroxisomes in guinea pig liver: their peculiar morphological features may reflect certain aspects of lipoprotein metabolism in this species

Summary We have studied the ultrastructural characteristics and the distribution of peroxisomes in guinea pig liver using electron-microscopic cytochemistry for catalase and morphometry. By light microscopy, peroxisomes appear as dark 0.2–0.5 m granules in the cytoplasm of liver parenchymal cells, often forming large clusters that measure up to 5 m across. Rows of single peroxisomes or their aggregates line the sinusoidal surface of hepatocytes. Electron microscopy reveals that clusters of up to 25 individual peroxisomes are usually located in the subsinusoidal region of parenchymal cells. The mean diameter and the volume density of peroxisomes are larger in pericentral than in periportal regions of the liver lobule. Whereas large amounts of lipoprotein particles with a mean diameter of 160 nm (chylomicrons) are present in the Disse space, the cytoplasm of parenchymal cells contains multivesicular bodies and abundant lipid droplets. In addition, the Golgi complexes show distended lipoprotein-filled vesicles suggesting active biosynthesis of lipoproteins. We propose that the unique features of peroxisomes in guinea pig liver, such as cluster formation and alignment along the sinusoidal surface, may be related to the high levels of lipoproteins in the portal circulation and their hepatic catabolism in this species.     

Fine structure of the spiracular glands in larval Drosophila melanogaster (Meig.) (Diptera : Drosophilidae)

The spiracular glands in the third-instar larvae of Drosophila melanogaster (Diptera : Drosophilidae) were examined with light and electron microscopy. Three club-shaped, unicellular glands are associated with each spiracle. Each gland has a large nucleus with a well-developed nucleolus and polytene chromosomes. Cytoplasmic features include a prominent plasma membrane reticular system (PMRS), which contains electron-dense material and gives rise to endocytotic vesicles. Numerous lipid droplets, mitochondria, free ribosomes, glycogen, lysosomes, and vesicles are scattered throughout the cytoplasm. The smooth endoplasmic reticulum is abundant, but rough endoplasmic reticulum and Golgi complexes are sparse. Small lipid droplets appear to fuse with one another to form larger droplets. In late third-instar glands, normal mitochondria decrease in number; they appear to degenerate and become converted into dense bodies with finely granular interiors. Several microvillous channels containing lipid are present within the cytoplasm. In the lumina of most of these channels are found the distal tips of cuticular ductules. The cuticular ductules merge with one another dorsally to form the main duct that carries the lipoid secretion to the spiracle cleft. The ultrastructure of the spiracular glands is consistent with their roles in the synthesis of lipoid secretion, which is used to provide hydrophobicity of the surface and to trap small particulate matter.     

Changes in the lipid inclusion/Sertoli cell cytoplasm area ratio during the cycle of the human seminiferous epithelium

The area occupied by Sertoli cell lipid inclusions--electron-lucent lipid vacuoles (LLV) and electron-dense lipid droplets (DLD)--at each stage of the cycle of the seminiferous epithelium was measured on electron micrographs in young adults and elderly men, and expressed as the ratio "area occupied by lipid inclusions/area occupied by the Sertoli cell cytoplasm". For LLV this ratio increased from stage I to stage III, and decreased from stage IV to stage VI in young adults. These results suggest that the development of LLV is synchronized with the spermatogenic process: the residual bodies released in stages I and II are phagocytized by Sertoli cells and transformed into LLV; the amounts of LLV decrease in the subsequent stages of the cycle and increase again when new residual bodies appear. In elderly men the ratio LLV/Sertoli cell cytoplasm was 1.9-2.9 times higher than in young adults at each stage of the cycle. This increase may be related to the increased germ-cell degeneration observed in ageing testes, DLD were less abundant than LLV and the DLD/Sertoli cell cytoplasm ratio did not undergo cyclic changes in young adults or elderly men.     

Fine Structure of the Ovarian Development in the Orb-web Spider, Nephila clavata

ABSTRACT Fine structural changes of the ovary and cellular composition of oocyte with respect to ovarian development in the orb-web spider, Nephila clavata were examined by scanning and transmission electron microscopy. Unlike the other arthropods, the ovary of this spider has only two kinds of cells-follicle cells and oocytes. During the ovarian maturation, each oocyte bulges into the body cavity and attaches to surface of the elongated ovarian epithelium through its peculiar short stalk attachments. In the cytoplasm of the developing oocyte two main types of yolk granules, electron-dense proteid yolk and electron-lucent lipid yolk granules, are compactly aggregated with numerous glycogen particles. The cytoplasm of the developing oocyte contains a lot of ribosomes, poorly developed rough endoplasmic reticulum, mitochondria and lipid droplets. These cell organelles, however, gradually degenerate by the later stage of vitellogenesis. During the active vitellogenesis stage, the proteid yolk is very rapidly formed and the oocyte increases in size. However, the micropinocytosis invagination or pinocytotic vesicles can scarcely be recognized, although the microvilli can be found in some space between the oocyte and ovarian epithelium. During the vitellogenesis, the lipid droplets in the cytoplasm of oocytes increase in number, and become abundant in the peripheral cytoplasm close to the stalks. On completion of the yolk formation the vitelline membrane, which is composed of an inner homogeneous electron-lucent component and an outer layer of electron-dense component is formed around the oocyte.     

Electron microscopy of vesicular-arbuscular mycorrhizae of yellow poplar. II. Intracellular hyphae and vesicles.

Intracellular hyphae and vesicles in mycorrhizal roots of yellow poplar were examined by electron microscopy. An investing layer of host wall material and cytoplasm enclosed the endophyte within the cells. Young developing hyphae contained abundant cytoplasm and few vacuoles. As hyphae matured, they became highly vacuolated and accumulated carbohydrate (glycogen) and lipid reserves. Mature vesicles were engorged with lipid droplets, possessed a trilaminate wall and were also enclosed by host wall material and cytoplasm. Compared with uninfected cells, infected cortical cells showed an increase in cytoplasmic volume, enlarged nuclei, and a reduction of starch reserves. Host nuclei were always proximal to the hyphae during hyphal development and deterioration. While other cytoplasmic components of infected and uninfected cells were comparable large electron-dense bodies occurred in vacuoles of most cells containing hyphae. Deterioration of intracellular hyphae occurred throughout the samples examined. Septa separated functional and degenerating portions of the hyphae. Hyphal deterioration involved degeneration and ultimate disappearance of fungal cytoplasm as well as collapse of hyphal walls. Based on these observations, the authors hypothesize that deterioration of the endophyte may release significant quantities of mineral nutrients, via hyphal contents, which are absorbed by the host.