The effect of diet on the ultrastructure of the mid-gut cells of Nasonia vitripennis (Walk.) (Insecta: Hymenoptera) at various ages

Summary The ultrastructure of mid-gut cells of female Nasonia fed on a diet of 10% sterile sucrose is described. There are extensive alterations in cell organelles, particularly the mitochondria, rough endoplasmic reticulum (R.E.R.) and lipid inclusions, when compared to similar insects fed a normal diet of dipteran pupae. A proportion of the mitochondria found in the apical cell region are enlarged in size and contain electron-dense granules. The remaining mitochondria are smaller, but also contain electron-dense granules. Cytochrome-c oxidase activity appears to be absent from the enlarged mitochondria. The R.E.R. appears reduced in many cells of the 1 day old, sugar-fed insects, however, this component fluctuates throughout the remaining life span. The lipid inclusions prominent in the 1 day old, pupae-fed insects are not present in sucrose-fed females of the same age, but lipid deposition was recorded later in the life span. There are many large residual bodies and cytolysosomes present in the old, sugar-fed insects. These changes in ultrastructure are discussed in relation to diet and longevity.     

Ultrastructural, histochemical and cytochemical characterization of intestinal epithelial cells in Aplysia depilans (Gastropoda, Opisthobranchia)

To improve the current knowledge about the digestive system in opisthobranchs, light and electron microscopy methods were used to characterize the epithelial cells in the mid‐intestine of Aplysia depilans. This epithelium is mainly formed by columnar cells intermingled with two types of secretory cells, named mucous cells and granular cells. Columnar cells bear microvilli on their apical surface and most of them are ciliated. Mitochondria, multivesicular bodies, lysosomes and lipid droplets are the main components of the cytoplasm in the region above the nucleus of these cells. Peroxisomes are mainly found in middle and basal regions, usually close to mitochondria. Mucous cells are filled with large secretory vesicles containing thin electron‐dense filaments surrounded by electron‐lucent material in which acidic mucopolysaccharides were detected. The basal region includes the nucleus, several Golgi stacks and many dilated rough endoplasmic reticulum cisternae containing tubular structures. The granular cells are characterized by very high amounts of flat rough endoplasmic reticulum cisternae and electron‐dense spherical secretory granules containing glycoproteins. Enteroendocrine cells containing small electron‐dense granules are occasionally present in the basal region of the epithelium. Intraepithelial nerve fibres are abundant and seem to establish contacts with secretory and enteroendocrine cells.     

The ultrastructure of the mid-gut cells of Nasonia vitripennis (Walker) (Hymenoptera,Pteromalidae)

Summary The ultrastructure of the mid-gut cells of female Nasonia vitripennis is described. The mid-gut consists of a uniform, single-cell epithelium. The cells of different gut regions were analysed using morphometric techniques in order to determine any differences in the components. The structure of the cells is described in the unfed animal, and after varying periods of feeding on host body-fluids. Tissues were sampled after 12 h and 24 h of feeding on host body-fluids and after 24 h feeding/24 h starvation. The cells were found to be complex and contain an organelle component that allows solute-transport and extensive lipid synthesis. A limited cytochemical analysis involving the lysosomal marker enzyme-acid phosphatase — and the respiratory enzyme — cytochrome oxidase was carried out.We are indebted to Professor E.W. Knight-Jones, in whose Department this work was carried out, and to the Science Research Council for financial support to one of us (I.D.)     

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.     

Ultrastructure of the colon of Locusta migratoria

The ultrastructure of the colon of Locusta migratoria is described. The colon is lined by a thick cuticle that, for the most part, adheres to the underlying epithelium. The cuboid epithelial cells are characterized by moderate invaginations of the apical and, to a lesser extent, basal plasma membranes; the lateral plasma membranes are relatively flat. The bulk of the mitochondria are located in the apical region of the cell and are not particularly associated with any of the plasma membranes. The basal region of the cells contains much rough endoplasmic reticulum, glycogenlike granules, and a predominance of spherical, electron-dense bodies of various sizes. Where muscle fibers make contact with the epithelium, the cells are much reduced; the cytoplasm is usually less electron-dense, and, typically, the nucleus has a thick layer of granular material associated with the inner nuclear membrane. The apical and basal plasma membranes of the reduced epithelial cells contain numerous hemidesmosomes. The apical hemidesmosomes occur in pairs around an extracellular space that contains electron-opaque material. The latter forms tonofibrillae that extend into the endocuticle. Bundles of microtubules are associated with the hemidesmosomes. The tubules traverse the cell from the apical to the basal region. The possible significance of these findings is discussed.     

An ultrastructural study of the prostate gland of megascolicid earthworm Lampito mauritii (Kinberg)

The ultrastructure of prostate gland of Lampito mauritii revealed two types of secretory cells. Type 1 cells with a broad basal region and a long apical region contain electron dense oval secretory granules with an increased density at the core region. Numerous electron lucent granules with fine filamentous and electron dense amorphous materials also occur at the basal region of these cells. Type 2 cells contain electron lucent mucous-like secretory granules. This cell type contains exceptionally large Golgi complexes having 20-23 stacked cisternae. Both cell types open into a common lumen and numerous microtubules are visible at the apical end. Junctional complexes, such as desmosomes and septate junctions, are observed in this glandular tissue.     

Ultrastructure of spermatogenesis in Cerastoderma glaucum (Cardiacea) and Spisula subtruncata (Mactracea)

Summary

In Cerastoderma glaucum, Sertoli cells are rich in lipids, glycogen and lysosomes, and premeiotic cells exhibited nuage, a prominent Golgi complex and endoplasmic reticulum cisternae encircling the nucleus. The Golgi complex gives rise to proacrosomal vesicles during mid-spermiogenesis, and the round acrosomal vesicle, with a dense fibrillar core, migrates laterally while linked to the plasma membrane as it develops the subacrosomal material. In its final position, the vesicle becomes cap-shaped (0.6 μm) and differentiates into apical light and basal dense regions. The elongated and helicoidal nucleus (8–9.9 μm) has a thin tip (0.3 μm) that invades the subacrosomal space, and in the midpiece (0.8 μm) two of the four mitochondria extend laterally to the nucleus (1.5–2.1 μm). In Spisula subtruncata, Sertoli cells are rich in lipids, glycogen and phagocytosed sperm. Premeiotic cells exhibit nuage, a prominent Golgi complex that gives rise to proacrosomal vesicles from the leptotene stage and a flagellimi that is extruded at zygotene. The acrosomal vesicle forms during the round spermatid stage and differentiates into a large and dense basal region and an apical light region. It then migrates while linked to the plasma membrane by its apical pole. Development of the subacrosomal perforatorium is associated with nuage materials and endoplasmic reticulum vesicles. The mature cap-shaped (0.6 μm) acrosomal vesicle exhibits a large apical and irregular region with floccular contents and a basal dense region. The round nucleus becomes barrel-shaped (1.5 μm) and the midpiece (0.8 μm), with four mitochondria, contains a few glycogen particles.     

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.     

A model of calcium waves in pancreatic and parotid acinar cells

We construct a mathematical model of Ca(2+) wave propagation in pancreatic and parotid acinar cells. Ca(2+) release is via inositol trisphosphate receptors and ryanodine receptors that are distributed heterogeneously through the cell. The apical and basal regions are separated by a region containing the mitochondria. In response to a whole-cell, homogeneous application of inositol trisphosphate (IP(3)), the model predicts that 1), at lower concentrations of IP(3), the intracellular waves in pancreatic cells begin in the apical region and are actively propagated across the basal region by Ca(2+) release through ryanodine receptors; 2), at higher [IP(3)], the waves in pancreatic and parotid cells are not true waves but rather apparent waves, formed as the result of sequential activation of inositol trisphosphate receptors in the apical and basal regions; 3), the differences in wave propagation in pancreatic and parotid cells can be explained in part by differences in inositol trisphosphate receptor density; 4), in pancreatic cells, increased Ca(2+) uptake by the mitochondria is capable of restricting Ca(2+) responses to the apical region, but that this happens only for a relatively narrow range of [IP(3)]; and 5), at higher [IP(3)], the apical and basal regions of the cell act as coupled Ca(2+) oscillators, with the basal region partially entrained to the apical region.     

Developmental study onHypolepis punctata (Thunb.) Mett.

The origins of the first and second petiolar buds ofHypolepis punctata were clarified in relation to the early development of the leaf primordium, which arises from a group of superficial cells of the shoot apical meristem. One of these superficial cells produces a two-sided leaf apical cell which subsequently cuts off segments to make a well-defined cell group, called here the leaf apical cell complex, on the distal part of the leaf primordium. Meanwhile, cells surrounding the leaf apical cell complex also divide frequently to form the basal part of the leaf primordium. Two groups of basal cells of the leaf primordium located on the abaxial and the adaxial sides initiate the first and the second petiolar buds, respectively. The initial cells are usually contiguous to the leaf apical cell complex, constructing the abaxial and adaxial flanks of the very young leaf primordium. However, the first petiolar bud sometimes develops from cells located farther from the leaf apical cell complex. These cells are derived from those originally situated in the peripheral region of the shoot apical meristem. This study was supported by a Grant-in-Aid for Encouragement of Young Scientists by the Ministry of Education, Science and Culture, of Japan No. 474322 in 1979.     

Confocal laser scanning light microscopy of the extra-thecal epithelia of undecalcified scleractinian corals

The extra-thecal epithelia of cryofixed undecalcified, freeze-substituted polyps of the scleractinian corals Galaxea fascicularis and Tubastrea faulkneri and axial and basal polyps of Acropora formosa have been examined, in anhydrously prepared thick slices, by confocal laser scanning light microscopy. The avoidance of chemical fixation and decalcification makes it possible to determine whether previously seen structures are real or artefactual products of swelling, shrinkage and distortion. All of the epithelia of all the corals examined are characterised by well defined intercellular spaces. Mucocytes are present in all cell layers in Galaxea and Tubastrea but are not present in any cell layers in the axial polyp of Acropora although they are abundant in the oral ectoderm of the basal polyps in this coral. Zooxanthellae are absent in Tubastrea, the epithelia of the exert septa of Galaxea and the axial polyp of Acropora. The calicoblastic ectoderm is generally composed of thin squamous cells with large intercellular spaces. At rapidly calcifying regions such as the tips of the exert septa of Galaxea, the calicoblastic cells are elongated with extensive arborisation of the basal regions of the cells. They are separated by large intercellular spaces and contain numerous fluorescent granules. The apical regions of these cells appear to be closely applied to the surface of the skeleton. There is no evidence of a space between the apical region of the calicoblastic cells and the skeleton.     

Ultrastructure of the sexual segments of the kidney in male and female lizards,Cnemidophorus l. lemniscatus (L.)

Summary Kidneys of adult male and female lizards were studied by electron microscopy, in order to understand the ultrastructure of the collecting duct and a differentiated part thereof, the sexual segment, which is an important accessory sexual organ. First portion of sexual segment in males: The cells are filled with large secretory granules of a wide range of opacities. The granular endoplasmic reticulum is abundant; basal formations of superimposed flat cisternae are frequent. Distended vesicles and microvesicles prevail in the supranuclear, well developed Golgi apparatus. Evidences indicate that secretion of these cells is holocrine. Second portion of sexual segment in males: All of the secretory granules are apical in location and relatively electron-opaque; they show a denser core. This core is formed by a substance which, after lying in contact with ribosomes, enters the secretory vesicles of the highly developed Golgi apparatus. A lighter substance is then condensed around it. The secretion of the granules is merocrine. The granular endoplasmic reticulum is very abundant in these cells, but basal ergastoplasmic formations are lacking. Sexual segment in females: The cells show features similar to those of the male first portion, but they are smaller. Undifferentiated collecting duct: Most of the cells are mucigenic. They have small ovoid, apical secretory granules. The density of the granules varies from cell to cell; when they are electron-lucent, they exhibit laminar or dotted opaque figures. Moderately developed Golgi apparatus and granular endoplasmic reticulum, as well as elongated mitochondria, occur in mucigenic cells. Intercalated among the latter are non-secretory cells. They have very abundant mitochondria, numerous microvilli, many pinocytic and smooth-membrane vesicles, whereas the organelles participating in synthetic processes are poorly developed; their function is most likely related to active solute transport.     

Light and electron microscopy study of the salivary glands of the carnivorous opisthobranch Philinopsis depicta (Mollusca, Gastropoda)

Cephalaspideans are a group of opisthobranch gastropods that comprises carnivorous and herbivorous species, allowing an investigation of the relationship between these diets and the morphofunctional features of the salivary glands. In this study, the salivary glands of the carnivorous cephalaspidean Philinopsis depicta were observed by light and electron microscopy. The secretory epithelium of these ribbon-shaped glands is formed by ciliated cells, granular cells and cells with apical vacuole. In ciliated cells the nucleus and most cytoplasmic organelles are located in the wider apical region and a very thin stalk reaches the base of the epithelium. These cells possess significant amounts of glycogen. Granular cells are packed with electron-dense secretory granules and also contain several cisternae of rough endoplasmic reticulum and Golgi stacks. The other type of secretory cell is mainly characterized by the presence of a large apical vacuole containing secretion. These cells possess high amounts of rough endoplasmic reticulum cisternae and several Golgi stacks. Vesicles with peripheral electron-dense material are also abundant, and seem to fuse to form the apical vacuole. The available data point out to a significant difference between the salivary glands of carnivorous and herbivorous cephalaspidean opisthobranchs, with an intensification of protein secretion in carnivorous species.     

Histology and ultrastructure of the salivary glands in Bulla striata (Mollusca, Opisthobranchia)

Abstract. The ribbon‐shaped salivary glands in Bulla striata were studied with light microscopy and transmission electron microscopy (TEM). Secretion is produced in tubules formed by two types of secretory cells, namely granular mucocytes and vacuolated cells, intercalated with ciliated cells. A central longitudinal duct lined by the same cell types collects the secretion and conducts it to the buccal cavity. In granular mucocytes, the nucleus is usually central and the secretory vesicles contain oval‐shaped granular masses attached to the vesicle membrane. Glycogen granules can be very abundant, filling the space around the secretory vesicles. These cells are strongly stained by PAS reaction for polysaccharides. Their secretory vesicles are also stained by Alcian blue, revealing acidic mucopolysaccharides, and the tetrazonium reaction detects proteins in minute spots at the edge of the vesicles, corresponding to the granular masses observed in TEM. Colloidal iron staining for acidic mucopolysaccharides in TEM reveals iron particles in the electron‐lucent region of the vesicles, while the granular masses are free of particles. In vacuolated cells, which are thinner and less abundant than the granular mucocytes, the nucleus is basal and the cytoplasm contains large electron‐lucent vesicles. These vesicles are very weakly colored by light microscopy techniques, but colloidal iron particles could be observed within them. The golf tee‐shaped ciliated cells contain some electron‐dense lysosomes in the apical region. In these cells, the elongated nucleus is subapically located, and bundles of microfibrils are common in the slender cytoplasmic stalk that reaches the basal lamina. The morphological, histochemical, and cytochemical data showed some similarities between salivary glands in B. striata and Aplysia depilans. These similarities could reflect the phylogenetic relationship between cephalaspidean and anaspidean opisthobranchs or result from a convergent adaptation to an identical herbivorous diet.     

Morphology of the epithelium of the extratesticular rete testis, ductuli efferentes and ductus epididymidis of the adult male rabbit

The fine structure of the epithelium lining the extratesticular rete testis, ductuli efferentes and ductus epididymidis of the rabbit has been investigated. In the ductuli efferentes the epithelium is composed of two cell types, principal cells and ciliated cells. The latter type is distinguished from principal cells by the presence of cilia projecting into the lumen and the position of the nucleus in the apical half of the cell. Principal cells in this segment are characterized by micropinocytotic vesicles on the surface plasma membrane and a variety of small dense bodies scattered throughout the cytoplasm. In the ductus epididymidis basal cells replace ciliated cells as the second cell type, but differences between various segments of the epididymis are related to the fine structure of the principal cells. In the proximal caput epididymidis (Nicander's region 1) the principal cells are tall with long microvilli. They typically contain a small Golgi apparatus and a cluster of dense bodies adjacent to the nucleus. In the distal caput epididymidis (Nicander's regions 2-5) the apical cytoplasm of principal cells is filled with numerous micropinocytotic vesicles and large multivesicular bodies; these features are interpreted as signs of absorptive activity. The multivesicular bodies are absent from the cytoplasm of principal cells in the corpus epididymidis (Nicander's region 6) and, instead, numerous elements of smooth endoplasmic reticulum, a large Golgi apparatus, lipid droplets and dense bodies characterize principal cells in this segment. Towards the proximal cauda epididymidis (Nicander's region 7), the number of dense bodies (lysosomes) in the cytoplasm increases considerably. In the globose cauda (Nicander's region 8), the principal cells are reduced in height, and in addition to the features described in region 7, are characterized by a concentric array of rough endoplasmic reticulum in the basal cytoplasm. These observations are discussed in relation to the role of the epididymis in promoting the maturation and survival of spermatozoa.     

Fine structure of the sweat glands of the antebrachial organ of Lemur catta

Summary The sweat glands of the antebrachial organ of the ring-tailed lemur are atypical apocrine glands which have some characteristics of eccrine sweat glands. The myoepithelial cells are large and consist of well-differentiated basal and apical regions. The secretory cells form a monolayer of tall, columnar cells filled with numerous secretory vacuoles and capped with differentiated apical blebs. The vacuoles are formed in the Golgi region and their contents are discharged into the lumen and into intercellular canaliculi. The blebs are pinched off at the luminal surface by a true apocrine mechanism. In addition to the usual organelles (abundant rough endoplasmic reticulum, prominent Golgi region, large mitochondria, pigment, secretory vacuoles), the secretory cells contain bundles of microtubules. Each microtubule is about 325–350 Å in diameter. The glands are larger and more active in the male. These sweat glands are distinctly different from the apocrine glands of the general body surface of L. catta.Publication No. 128 of the Oregon Regional Primate Research Center, supported in part by Grants FR 00163 and AM 08445 from the National Institutes of Health. The author expresses thanks to D. McLean for preparation of the diagram.     

Fine Structure of the ‘Slit Organs’ of the Pycnogonid Anoplodactylus petiolatus (Anoplodactylidae)

Abstract The ‘slit organs’ of Anoplodactylus petiolatus are found all over the body cuticle. They are composed of a cuticular pore apparatus, an inner and an outer canal cell, and of four large and one to three small compartment cells. Plasma of the latter seven cells is almost completely filled with large membrane-enclosed compartments that contain either numerous small vesicles (one of the large cells) or homogeneous material of varying electron density (three large and all the small cells). Microvilli are found in the apical region of the compartment cells. The nucleus is situated basally where Golgi-cisternae, coated vesicles and free ribosomes are frequently found. Apical microvilli and vesicles are also formed by the inner canal cell indicating that it might directly be involved in transport. Anatomically the ‘slit organs’ are similar to class III glands described for many arthropods. In addition, discharge of secretion via large intracellular compartments is also a feature found in arthropod glands. Although pycnogonids appear to take up substances across the cuticle, a genuine secretion rather than a more generalized transport function is suggested for the ‘slit organs’.     

Division,growth, and branch formation in protonema of the mossPhyscomitrium turbinatum: Studies of sequential cytological changes in living cells

Summary Elongating caulonemal tip cells ofPhyscomitrium turbinatum were cultivated on mediumcoated cover slips and periodically observed with Nomarski differential interference contrast optics. Tip cells exhibit apical growth and an average growth rate of 27.5 m/h. During cell elongation the nucleus migrates forward in the tip cell, but this movement slowly decreases so that there is a gradual increase in the distance between the nucleus and cell tip. Minimum length cells contain small vacuoles adjacent to the basal wall which coalesce during subsequent cell elongation to form a solitary large basal vacuole.An increase in chloroplasts during cell elongation is due to the presence of a population of proliferating chloroplasts located between the cell tip and the nucleus resulting in a gradient in chloroplast number and shape. The zone of chloroplast proliferation shifts progressively forward during cell elongation from a peri-nuclear position to a region closer to the cell tip. During division of the apical cell a perpendicular metaphase plate is formed. Reorientation movements of the phragmoplast-cell plate during telophase, and early stages of the following interphase produce a 35–40° cross wall. This rotation of the spindle axis positions the daughter nuclei temporarily adjacent to the lateral walls on opposite sides of the cell with the sub-apical nucleus on the side nearest the light source. It subsequently migrates across the cell to become situated on the wall farthest from the light source. Sub-apical cells form branches at the distal (= apical) end of the cell on the lateral wall closest to the light source. Branch development is accompanied by changes in chloroplast shape, number, and position.     

Cellular Events of Wrinkled Blastula Formation and the Influence of the Fertilization Envelope on Wrinkling in the Seastar Patiriella exigua

Like many echinoderms, the seastar, Patiriella exigua has a wrinkled blastula rather than the smooth-walled blastula typical of most phyla. The cellular events of wrinkled blastula formation in P. exigua were documented using light, confocal and electron microscopy. Wrinkled blastulae have a highly infolded epithelium. Prior to wrinkling, the blastomeres are cuboidal with lipid droplets and yolk granules distributed throughout their cytoplasm. During wrinkling, the cells become columnar and the lipid and yolk reserves become redistributed to the basal and apical ends of the cells, respectively. Gastrulae have a tall columnar epithelium, with a basal accumulation of lipid. Interdigitation of numerous cell projections, including short lateral processes, basal lamellipodia and apical filopodia, assists in maintaining epithelial integrity during wrinkling. Apical filopodia have not been observed in other echinoderm embryos. Although 1 M urea caused elevation of the fertilization envelope, the embryos did not expand into the newly-created space. This is suggested to be due to the adhesive properties of the hyaline layer. Embryos removed from their envelope were enlarged with shallower and fewer wrinkles compared with controls. It appears that the integrity of the hyaline layer and fertilization envelope both influence the compact wrinkled profile of P. exigua blastulae.