Ultrastructural studies on the secretory cavities ofCitrus deliciosa ten. II. Development of the essential oil-accumulating central space of the gland and process of active secretion

Summary Oil glands ofCitrus deliciosa are multicellular secretory structures, globular to oval in shape, in the centre of which an essential oil-accumulating space is formed. Opening of this space begins from a single cell. It undergoes lysis which later extends to the neighbouring gland cells.Secretory material in form of droplets is produced in plastids, from where it is transported to the parietal cytoplasm of the secretory cells via numerous ER-elements. After fusion of the ER-membranes with the plasmalemma, the exudate reaches the apoplast, through which it is driven to the central cavity of the gland.Peripheral cells of the secretory complex are modified into a protective sheath with thick walls and large vacuoles, while their plastids are differentiated from leucoplasts into typical amyloplasts.     

The secretory apparatus of Ginkgo biloba: structure,differentiation and analysis of the secretory product

Summary The differentiation of the secretory cavities of Ginkgo stem and the structural organization of the epithelial cells were followed by light and electron microscopy. The mode of formation of the cavities is schizo-lysigeneous. Functional complexes of leucoplasts and associated endoplasmic reticulum (ER) membranes are assumed to be the site of synthesis and translocation of the lipophilic secretory product. Most of the endoplasmic reticulum membranes are paired. The content of the cavities was directly collected and analysed by low- and high-resolution mass spectrometry. The cavities contain anacardic acids and cardanols, which are long-chain phenol lipids not characteristic of Ginkgo. The relationship between the plastid/ER complexes and the production of these secondary metabolites is discussed.     

Cloning and characterization of five cDNAs for genes differentially expressed during fruit development of kiwifruit (Actinidia deliciosa var.deliciosa)

Five cDNAs for genes differentially expressed during fruit development of kiwifruit (Actinidia deliciosa var.deliciosa cv. Hayward) were isolated from a library made from young fruit, 8–10 days after anthesis. One gene (pKIWI503) has low levels of expression in young fruit but is induced late in fruit development and during fruit ripening, and has some homology to plant metallothionein-like proteins. The other four genes are highly expressed in young fruit with reduced expression in the later stages of fruit development. pKIWI504 has strong homology to plant metallothionein-like proteins and pKIWI505 exhibits homology to the -subunit of the mitochondrial ATP synthase gene. The two other genes (pKIWI501 and 502) encode proteins with no significant homology to other known sequences.     

Ultrastructure of the stylar canal cells ofCitrus limon (Rutaceae)

The ultrastructure of the canal cells and the canal filling substance ofCitrus limon have been studied. At maturity the canal cells are very rich in cytoplasm. Their inner tangential walls lining the canal are much thickened and formed by two layers: the outer corresponds to the original wall, the inner is formed by subsequent deposition of abundant materials of different origin. This thickening occurs at the same time as the filling of the stylar canal. Both events are paralleled by considerable dictyosomic activity, the formation of a large amount of rough endoplasmic reticulum, and the incorporation of small cytoplasmic masses into the cell wall, due to plasmalemma evaginations. — The material in the stylar canal has a heterogeneous ultrastructure aspect and consists of polysaccharides, proteins and lipids; it presumably provides nutrients for the growing pollen tubes.Research performed under CNR program Biology of Reproduction.     

Special secretory cells in the soybean seed coat

Summary The seed coat of soybean (Glycine max L. Merr.) is of physiological interest for synthesis and transport of amino acids and photosynthates during embryo development. A transmission and scanning electron microscopic study to elucidate the structure of the seed coat disclosed a specialized convex area (antipit) appressed to a concave pit in the center of the abaxial surface of the cotyledon. The antipit, which lies on the inner surface of the seed coat at a medial point in the anterior to posterior direction of the seed, contained specialized secretory cells bounded by loose multi-layered cell walls. These cells were rectangular in the developing seed, varied in length, and contributed directly to the convex morphology of the antipit seen on the ventral surface of the seed coat. At maturity these cells assumed the shape of a cone, extending from the aleurone layer in a perpendicular array. The aleurone and cone cells contained numerous Golgi apparatus, laminated rough endoplasmic reticulum, secretory vesicles, and amyloplasts. Secretory vesicles arose directly from tubules of fenestrated trans cisternae of the Golgi apparatus. Mitochondria were clustered with the amyloplasts; stacks of lamellar cisternae of rough endoplasmic reticulum were associated with the nucleus and Golgi apparatus. The cellular contents, the interconnections by plasmodesmata, and the close physical association with the cotyledon suggested that the aleurone and cone cells may be involved in symplastic transport of nutrients for use by the developing embryo.This paper is dedicated to the memory of my parents, Joseph and Theresa Yaklich, who by their example taught me the value of work and the enjoyment of simple things.     

Early Development of the Secretory Cavity of Peltate Glands in Humulus lupulus L. (Cannabaceae)

Early development of the secretory cavity of chemically fixed peltate glands in Humulus lupulus L. showed secretions with different densities, light, gray and dark, in the cytoplasm of disc cells and in the periplasmic space adjacent to the developing secretory cavity. Secretions were detected in the disc cell wall and subsequently in the developing secretory cavity under the subcuticular wall of the sheath. Light and gray secretions in the cavity possessed a membrane-like surface feature. Secretions were in contact with the irregular inner surface of the cuticle. Secretions contributed to the thickening of the cuticle, whereas the membrane-like surface feature contributed to a network of Cannabis striae distributed throughout the cuticle. This study supports an early development and organization of the secretory cavity in H. lupulus, parallel to those in Cannabis, and may represent common features for lipophilic glands in angiosperms.     

Fine-grained secretory cells in the intestine of the lancelet,Branchiostoma (Amphioxus) lanceolatum,studied by light microscopy

Summary In the posterior part of the mid-gut epithelium in the lancelet, Branchiostoma lanceolatum, fine-grained cells occur. The appearance of the these cells is conspicuous with a basal and an apical swelling with small secretory granules. At the end of the secretion cycle the granular content is released into the gut lumen. The secretion product seems to consist of proteins and probably has an enzyme function. The restricted localization, the fine granulation, and the characteristic shape are features, that make these cells distinguishable from other secretory cells in the lancelet intestinal epithelium. A possible endocrine capacity of the cells is discussed.This work was supported by grant 2124-23 from the Swedish Natural Science Research Council and by grants from the Faculty of Science, University of Stockholm, Sweden.     

Ultrastructural changes in nurse and follicle cells during late stages of oogenesis in Drosophila melanogaster

Summary During stages 11 and 12, follicle cells surrounding the nurse cells produce lysosomes which presumably aid in the breakdown of the nurse cells. Accompanying a DNA reduction in nurse cell nuclei are several characteristic morphological changes including the appearance of intranuclear rod-like structures and nuclear granules about 300 Å in diameter. Similarities between structures seen in Drosophila nurse cell nuclei and those seen in other organisms are discussed.This research was supported by U. S. Public Health Service Grants 5TIGM903-3 and 1-F1-GM-33, 385-01 and National Science Foundation grant GB-7457.     

Ultrastructural studies on the nucleoli of the follicle cells in the Lizards Acanthodactylus scutellatus hardyi and Eremias brevirostris

Summary In male mice homozygous for both p ^s and hpy, two recessive, pleiotrophic, mutations, gametogenesis is normal through meiosis but no functional spermatozoa are produced. Spermiogenesis is abnormal from the Golgi phase on. The types of abnormalities seen during the early and mid-stages of Spermiogenesis are characteristic of those associated with the presence of the p ^s mutation whereas those associated with the hpy mutation appear during the later stages of spermatid development. While centriolar ultrastructure was normal, axonemal structures were only rarely encountered and no late spermatids with recognizable flagella were seen. Some late spermatids showed head abnormalities of the type characteristic of the p^s mutation while others were recognizable as being of the hpy type. A released gamete usually consisted of a distorted nucleus and associated acrosome enclosed in a tightly fitting plasma membrane. No spermatids exhibiting a novel phenotype were encountered. The findings support the view that, despite their simultaneous presence in the double homozygote, each mutation acts autonomously. These studies also allow a similar inference to be made with respect to the extent of the interrelationship of the other major sub-processes of Spermiogenesis.The author wishes to express his thanks to Mr. Clifford S. Shuman III for capable technical assistance     

Ultrastructural studies on prolactin and growth hormone cells in Anguilla pituitaries in long term cultures

Summary Eel hemi-pituitaries were cultured in vitro on high or low sodium media, previously shown to affect differentially prolactin and growth hormone release. After 6 days culture, there were marked differences in the ultrastructure of both prolactin and growth hormone cells from the two groups. Morphometric data on the prolactin cells from SW-adapted eels showed a greater abundance of RER and paucity of secretory granules in cells from the low sodium medium. The size of the Golgi apparatus and the number of exocytosed secretory granules did not differ markedly between experimental groups, in contrast to previous findings on short-term cultures. Differences in the profile diameters of secretory granules are recorded between the experimental groups and the pattern differs markedly from that previously recorded for short-term cultures. The growth hormone cells from low sodium media were characterised by abundant, vesiculated RER, a prominent Golgi apparatus (in SW-adapted animals) and relatively few secretory granules. The activity of these growth hormone cells is in marked contrast to previous findings relating to short-term cultures. The shape and size of the non-granulated (stellate) cells of the RPD was again affected by the osmotic pressure of the medium.I should like to thank Mr. P.F. Hire for his photographic assistance     

Effects of “media osmotic agents” on the growth and morphogenesis ofActinidia deliciosa cv “hayward” callus

Summary The influence of various osmotic agents (carbohydrates) on the morphogenesis and growth of callus ofActinidia deliciosa cv Hayward was studied. Sucrose supported the highest level of growth and the lowest was supported by the sugar alcohols used in the experiments (glycerol, mannitol, sorbitol). The growth and survival of callus were evaluated with different osmotic sources in media containing glycerol, mannitol, or sorbitol at a concentration of 0.2M each for an extended period of eight subcultures (360 days). Two crucial points were identified: until the third subculture (135 days) the vitality seemed to be elevated; whereas the fifth (225 days) seemed to be a “point of no return” for tissues grown in glycerol and mannitol. Pretreatment with osmotic carbohydrates was shown to increase the magnitude of the morphogenetic events of callus subsequently transferred to sucrose-containing medium. Callus grown in the presence of mannitol and sorbitol showed a similar frequency of morphogenetic response. With respect to the media containing glycerol and sucrose, these induced more intense regeneration of shoots. When glycerol was present in the medium, however, we observed a synchronization of the morphogenetic response. Our results suggest that it is possible both to stimulate and to synchronize morphogenesis utilizing osmotic conditioning subcultures.     

Ultrastructural localization of calcium in prothoracic gland cells of Galleria mellonella L. (Insecta,Lepidoptera) in relation to secretory activity

Summary Localization of intracellular calcium was demonstrated by precipitation with potassium hexahydroxoantimonate in the fixation medium containing osmium tetroxide or osmium tetroxide and glutaraldehyde. The presence of calcium in the precipitates was confirmed by X-ray microanalysis. Cells from active prothoracic glands contain more calcium deposits than inactive glands. The calcium precipitates are mainly localized in the nucleus, in the smooth endoplasmic reticulum, in the hyaloplasm and to a lesser degree in the mitochondria. These findings are consistent with the proposed role of calcium in the stimulation of steroidogenesis.     

Ultrastructural ontogeny of leaf cavity trichomes inAzolla implies a functional role in metabolite exchange

Summary Anabaena azollae is associated with two types of multicellular epidermal trichomes inAzolla leaf cavities, the simple and branched hairs. The observation of transfer cell ultrastructure in some hair cells led to speculation that the cavity hairs might participate in metabolite exchange between the symbionts. The developmental ontogeny of cavity trichomes is described here, using transmission electron microscopy, with a goal of improving our understanding of possible functions of these structures in the symbiosis. The observations have established that all cells of simple and branched hairs develop the structural characteristics of transfer cells, but not simultaneously. Rather, there is an acropetal succession of transfer cell ultrastructure beginning in terminal cells, moving to body cells where present, and ending in stalk cells. The transfer cell stage is followed immediately by senescence in all hair cells. The timing of transfer cell differentiation, considered together with information from other studies, suggests that branched hairs may be involved in exchange of fixed nitrogen between the symbionts, while simple hairs may participate in exchange of fixed carbon fromAzolla toAnabaena. Contribution no. 869 from the Battelle-C. F. Kettering Research Laboratory.     

Non-volatile components of the essential oil secretory cavities of Eucalyptus leaves: Discovery of two glucose monoterpene esters, cuniloside B and froggattiside A

The essential oils extracted from the embedded foliar secretory cavities of many Eucalyptus species are of economic value as pharmaceuticals and fragrance additives. Recent studies have indicated that Eucalyptus secretory cavities may not be exclusively involved in the biosynthesis and storage of essential oils. Therefore, we selected three species upon which to perform an examination of the contents of foliar secretory cavities: Eucalyptus froggattii, E. polybractea and E. globulus. This paper describes the isolation and structural characterization of two non-volatile glucose monoterpene esters, which we have named cuniloside B and froggattiside A, from within the secretory cavities of these species, and shows the presence of these compounds in solvent extracts of the leaves from two other species of Eucalyptus. Both compounds were found in high proportions relative to the essential oils extracted from the leaves. We propose that many other carbohydrate monoterpene esters previously isolated from bulk leaf extracts of various Eucalyptus species may also be localized within the non-volatile fraction of foliar secretory cavities.     

Ultrastructural studies on the secretory cycle of the neurosecretory cells and the formation of herring bodies in the paraventricular nucleus of the rat

Summary The ultrastructure of the neurosecretory cells in the paraventricular nucleus of the normal male rat was studied by electron microscopy during various functional states. Four morphologically distinct types of neurosecretory cells were observed. It appears that they do not represent different classes of cells but different phases of secretory activity of a single cell type. The perikarya of the neurosecretory cells show a definite cycle of formation and transportation of secretory granules. We have designated the phases of this cycle as: (1) phase of synthesis, (2) phase of granule production, (3) phase of granule storage and (4) phase of granule transport. The neurosecretory granules appear to be moved in bulk into the axons, forming a large axonal swelling filled with granules as a result of one cycle in the neurosecretory process. Thus it may be postulated that a secretory cycle in the perikaryon of the neurosecretory cell seems to result in the formation of a Herring body in its axon, and that its content is then conveyed to the posterior pituitary.     

Ultrastructural studies on plastids of generative and vegetative cells in Liliaceae

Summary The behaviour of plastids and mitochondria during the formation and development of the male gametophyte of Chlorophytum comosum has been investigated using electron microscopy. During first pollen mitosis an intracellular polarization of plastids occurs in that the plastids are clustered in the centre of the microspore. The originating generative cell normally lacks plastids. Only in a small number of microspores have plastids been observed near the dividing nucleus of the microspore and later on in the generative cell. These observations agree with the genetic investigations of Collins (1922) on the mode of plastid inheritance which demonstrated a small amount of biparental plastid inheritance in Chlorophytum. The cytological mechanisms underlying plastid polarization during the first pollen mitosis are discussed.     

Histochemical analysis of glycoproteins in the secretory cells in the gill epithelium of a catfish, Rita rita (Siluriformes, Bagridae)

Glycoproteins (GPs) were visualised histochemically in the secretory cells – the mucous goblet cells (the type A and the type B), the serous goblet cells, the club cells and the epithelial cells in the gill epithelium of Rita rita. The type A mucous goblet cells, the type B mucous goblet cells and the epithelial cells elaborate GPs with oxidizable vicinal diols and GPs with sialic acid residue without O-acyl substitution. In addition, GPs with O-sulphate esters are elaborated by the type A and GPs with O-acyl sugars by the type B mucous goblet cells. GPs are absent in the serous goblet cells and are with oxidizable vicinal diols in low moieties in the club cells. The analysis of the results elucidates interesting differences in the composition and concentration of GPs in the mucus elaborated by the epithelium of the gill arches and the gill rakers; and the gill filaments and the secondary lamellae indicating the potential importance of the glycoproteins at these locations. GPs elaborated on the surfaces of the gill arches and the gill rakers could be associated to assist in feeding activities and on the surfaces of the gill filaments and the secondary lamellae in the respiratory activity.