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.     

Ultrastructure of intestinal and gall-bladder epithelium in the teleost Gasterosteus aculeatus L., as related to their osmoregulatory function

Summary Intestinal and gall-bladder epithelial cells in sticklebacks have been examined in ultrathin sections and freeze-etch replicas. Enterocytes throughout the intestine appear to have a well-developed basal labyrinth similar to that of renal tubular cells, consisting of baso-lateral infoldings closely associated with numerous mitochondria. The lumen inside these intracellular membranes is continuous with the intercellular space via pores. Such a membrane system is also present in the epithelial cells lining the gall bladder, distinguishing them from gall-bladder cells of higher vertebrates. Morphometric analysis indicates that the basal labyrinth of enterocytes in the posterior part of the intestine increases markedly in both sexually mature males and androgen-treated females. This does not occur in the anterior part or gall bladder. In sticklebacks, androgens cause reduced urine excretion and enhanced fluid release via the anus. We conclude that the cells lining the intestine and gall bladder possess an extensive basal labyrinth that may function as a backward channel system, enabling fluid to be produced in the intestine of fish. The androgen-induced increase in the extent of the basal labyrinth in the posterior part of the intestine may be related to the enhanced rate of intestinal fluid excretion observed in sexually mature male sticklebacks.     

Effects of castration and of oestradiol treatment on the subcellular structure of the mouse seminal vesicles, with particular reference to the function of the Golgi apparatus and the lysosomes

Synopsis A number of changes were observed in the ultrastructure of seminal vesicles from castrated mice fed continuously with oestradiol. Treatment for two weeks was accompanied in the epithelial cells by the disappearance of secretion droplets, swelling of the Golgi structures and the appearance of many dense bodies and vesicles of various sizes. Subsequently, there was a decrease in the amount of rough endoplasmic reticulum followed by the disappearance of the vesicles. These changes were paralleled by a decrease in size and, finally, disappearance of the dense bodies, and by the appearance of abnormal nuclei. Ultimately, the epithelial cells became packed with free ribosomes and keratinization of the epithelium ensued.These metaplastic phenomena in the epithelium were accompanied by thickening and infolding of the basement membrane and by the formation of several layers of smooth muscle cells. The latter cells were very abnormal in that they contained prominent Golgi apparatuses and a vesiculated cytoplasm.When vesiculation occurred, both in the epithelium and in the cells of the basal areas of the acini (myoepithelial, basal and muscle cells), the vesicles, the Golgi bodies and the dense bodies (lysosomes) contained acid naphthol-AS-phosphatase activity. This enzyme was different from the more commonly described lysosomal acid -glycerophosphatase in that it was not inhibited by either sodium fluoride or sodium molybdate; in certain instances its activity in the cisternae of the endoplasmic reticulum could be shown to be enhanced by these compounds. The significance of these findings is discussed.     

A quantitative electron microscopic analysis of the keratinizing epithelium of normal human hard palate

Summary The epithelium of normal human hard palate was subjected to stereologic analysis. Ten biopsies were selected from a total of twenty specimens collected from 9 to 16 year old females, and processed for light- and electron microscopy. At two levels of magnification, electron micrographs were sampled from three strata (basale, spinosum, granulosum) in two locations (epithelial ridges and portions over connective tissue papillae). Stereologic point counting procedures were employed to analyse a total 1560 electron micrographs. In general, the thickness of the palate epithelium was 0.12 mm (over papillae) and 0.31 mm (in ridges), the epithelium is distinctly stratified, and homogeneously ortho-keratinized. From basal to granular layers, the composition of strata revealed decreasing densities of nuclei, mitochondria, membrane-bound organelles and aggregates of free ribosomes. Keratohyalin bodies and membrane coating granules increased, and cytoplasmic filaments with a constant diameter of about 85 Å increased from 14 to 30% of cytoplasmic unit volume. The cytoplasmic ground substance occupied a stable 50% of the epithelial cytoplasm in all strata. The composition of basal layers in ridges differed from that over connective tissue papillae. The data are discussed in relation to the observations that (1) an increasing gradient of filament density is not the most characteristic feature of ortho-keratinizing oral epithelium and (2) differences in the degree of differentiation in cells of the stratum basale coincided with the comparable frequency distribution pattern of dividing cells.The authors are thankful to Miss K. Rossinsky for excellent technical assistance, to Mrs. M. Graf-de Beer for competent data computation and to Mrs. S. Münzel-Pedrazzoli for help in morphometric analysis. This study was in part supported by Grants Nos. 51 and 106 of the Hartmann Müller Foundation and by a Grant from the Foundation of Scientific Research at the University of Zürich.     

Unusual membrane-bound bodies in the basal lamina of the uriniferous tubules of the camel Camelus dromedarius. Freeze-fracture and ultrathin-section study

Kidney samples of the camel Camelus dromedarius were aldehyde fixed and glycerol impregnated for ultrathin-section and freeze-fracture studies of the basal lamina. Results obtained show the presence of extracellular membrane-bound bodies within the thick basal lamina of the tubular portion of the nephron. The 10- to 500-nm bodies appear isolated and are found at various levels along the width of a highly structural lattice basal lamina. The bodies are observed either in small groups or as single structures which are invariably surrounded by a clear halo of the basal lamina. In ultrathin sections they appear limited by a typical unit-membrane structure, and their interior may appear empty or may exhibit material of variable electron opacity. Freeze-fracture replicas reveal the limiting membrane of the bodies which appear either as concave or convex structures. Intramembrane particles (IMPs) measuring between 5 and 15 nm are present in some of the bodies, whilst others appear devoid of IMPs. The IMPs are present in both concave and convex surfaces and are usually aggregated into clumps. The region of the basal lamina which contains the membrane-bound bodies is usually granular except in the area immediately surrounding the bodies which corresponds to the clear halo observed in thin sections. Although these basal lamina membrane-bound bodies appear to be similar to matrix vesicles previously described in mineralizing tissues, it seems unlikely that they are involved in calcification. It is possible that the membrane-bound bodies and the highly configurated basal lamina may be related to ionic transport mechanisms which are associated with the high osmolarity of the camel urine.     

Immunocytochemical localization of myosin during ciliogenesis of quail oviduct

Myosin has been localized during ciliogenesis of quail oviduct by immunocytochemistry (immunofluorescence, immunoperoxidase, immunogold labeling) using a previously characterized monoclonal antibody. In ovariectomized quail oviduct many undifferentiated epithelial cells present a primary cilium arising from one of the diplosome centrioles. Myosin is associated with material located between the two centrioles. In contrast, in estrogen-stimulated quail oviduct, the material preceding the procentioles is never labeled. Basal bodies become labeled just before their migration toward the apical plasma membrane. During the anchoring phase, the labeling is mainly associated with the basal feet. In mature ciliated cells, myosin appears associated with an apical network embedding the basal bodies. This network is connected to a myosin-rich belt associated with the apical junctional complex which differentiates at the beginning of centriologenesis. The association of myosin with migrating basal bodies suggests that myosin could be involved in basal body movements.     

Organization of actin microfilaments in the apical border of oviduct ciliated cells

Actin microfilaments were localized in quail oviduct ciliated cells using decoration with myosin subfragment S1 and immunogold labeling. These polarized epithelial cells show a well developed cytoskeleton due to the presence of numerous cilia and microvilli at their apical pole. Most S1-decorated microfilaments extend from the microvilli downward towards the upper part of the ciliary striated rootlets with which they are connected. From the microvillous roots, a few microfilaments connect the proximal part of the basal body or the basal foot associated with the basal body. Microfilament polarity is shown by S1 arrowheads pointing away from the microvillous tip to the cell body. Furthermore, short microfilaments are attached to the plasma membrane at the anchoring sites of basal bodies and run along the basal body. The polarity of these short microfilaments is directed from the basal body anchoring fibers downward to the cytoplasm. At the cell periphery, microfilaments from microvillous roots and ciliary apparatus are connected with those of the circumferential actin belt which is associated with the apical zonula adhaerens. Together with the other cytoskeletal elements, the microfilaments increase ciliary anchorage and could be involved in the coordination of ciliary beating. Moreover, microvilli surrounding the cilia probably modify ciliary beating by offering resistance to cilium bending. The presence of microvilli could explain the fact that mainly the upper part of the cilia appanars to be involved in the axonemal bending in metazoan ciliated cells.     

The ultrastructure of the spermatheca of Biomphalaria glabrata (gastropoda,pulmonata)

A study of the ultrastructure of the spermatheca of virgin freshwater snails Biomphalaria glabrata, kept in isolation since hatching, and in freely mating individuals maintained in colonies, shows that the spermatheca, an accessory organ of the female genital tract of pulmonate snails, is a pear-shaped blind pocket, lined with a single-layered columnar epithelium, surrounded by a thin muscle and pigmented connective. The apex of each epithelial cell may be ciliated, whereas the basis lies on a thick basement membrane. In virgin snails the spermatheca is smaller, its lumen contains a gelatinous, amorphous material; the apex of the epithelial cells contains many mitochondria but few granules. The nucleus appears in the basal third of the cell, topped by the Golgi complex and endoplasmic reticulum elements. In snails which have mated, the spermatheca is swollen, with a somewhat distended lower epithelium; its lumen contains numerous spermatozoa, in various degrees of degradation, which increases with the passage of time after copulation. The apex of the epithelial cells becomes very rich in granules with varied content, including multivesicular bodies. The latter are apparently exocytosed. Pinocytosis occurs at the base of microvilli. Glycogen can be seen accumulating in some cells. Tubular structures, ca. 60 nm in diameter, arranged regularly within the endoplasmic reticulum elements, could occasionally be seen at the basal part of the epithelial cells. It is suggested that the multivesicular bodies may contain enzymes which are secreted to the lumen. The partially digested sperm material would then be absorbed by micropinocytosis, and further digested in the secondary phagosomes at the apical portion of the epithelium.     

Uptake of exogenous protein tracer in cells of the rat renal papilla

In order to study the phagocytic potential of different cell types of the rat renal papilla with special emphasis on interstitial cells, horseradish peroxidase (HRP) (8 mg/100 g body weight) was injected intravenously into adult rats. The distribution of peroxidase was studied in animals perfusion-fixed 60 and 180 min after injection and was found to be similar after both time intervals. The epithelial cells of the collecting ducts took up the largest amounts of the tracer. HRP was mainly located in large lysosome-like bodies in the basal part of the cytoplasm, suggesting peritubular uptake from the interstitial space. However, small amounts of the tracer were also seen in apical vesicles close to the luminal plasma membrane. The interstitial cells of peroxidase-injected animals were ultrastructurally altered and had large irregular invaginations of the cell membrane. The cells had taken up only small amounts of the tracer which were located in small round lysosome-like bodies. Thus, the interstitial cells displays no macrophage characteristics, either in the native state or when challenged with an extracellular protein.     

Ultrastructure of oral (buccopharyngeal) membrane formation and rupture in the hamster embryo

The ultrastructure of the oral (buccopharyngeal) membrane was examined during normal development in embryos removed from pregnant hamsters at intervals from 7.5–10 days postcoitum. The oral membrane is represented at 7.5 days by a region of close approximation between endoderm and surface ectoderm anterior to the neural folds. A distinct basal lamina develops subjacent to each epithelial germ layer, and the narrow extracellular space separating the epithelia contains patches of fibrillar and flocculent material. Cell processes extend from cells of one epithelium across the extracellular space to make direct contact with cells of the opposing germ layer by 7.75 days. Increased intermingling of cells subsequently occurs within the oral membrane, and some cells extend the entire width of the membrane with surfaces exposed to both foregut and stomodeum. Accumulations of presumed basal lamina and extracellular material are observed at intervals within the oral membrane, but a continuous intercellular space is no longer present. Many of these accumulations are encompassed by processes of adjacent cells containing dense intracellular bodies, indicating active phagocytosis of this material by the epithelial cells. Rupture of the oral membrane begins between 8.25 and 8.75 days, and all remnants are removed by Day 9. Possible factors involved in rupture are discussed.     

Uptake of exogenous protein tracer in cells of the rat renal papilla

Summary In order to study the phagocytic potential of different cell types of the rat renal papilla with special emphasis on interstitial cells, horseradish peroxidase (HRP) (8 mg/100 g body weight) was injected intravenously into adult rats. The distribution of peroxidase was studied in animals perfusion-fixed 60 and 180 min after injection and was found to be similar after both time intervals. The epithelial cells of the collecting ducts took up the largest amounts of the tracer. HRP was mainly located in large lysosome-like bodies in the basal part of the cytoplasm, suggesting peritubular uptake from the interstitial space. However, small amounts of the tracer were also seen in apical vesicles close to the luminal plasma membrane. The interstitial cells of peroxidase-injected animals were ultrastructurally altered and had large irregular invaginations of the cell membrane. The cells had taken up only small amounts of the tracer which were located in small round lysosome-like bodies. Thus, the interstitial cells displays no macrophage characteristics, either in the native state or when challenged with an extracellular protein.Supported by Karolinska Institutet and the Swedish Medical Research Council (proj. no. 05937)     

Ultrastructure of the Somatic Cortex of the Gymnostome Ciliate Spathidium spathula (O. F. M.)1

The somatic cortex of Spathidium spathula is described ultrastructurally. The pellicle consists of an outer membrane and an underlying alveolar system. Numerous membrane-bound mucocysts and spherical electron-opaque bodies have similar circular sites of attachment to the outer membrane. Below these are a microfibrillar zone and an underlying region of rough ER. Mitochondria are lined up under the rough ER in longitudinal cortical ridges. Parasomal sacs are found near the basal bodies and are associated with cytoplasmic membranous sacs. Various microtubular and fiber systems are associated with single basal bodies: (1) a short kinetodesmal fiber; (2) two transverse microtubular ribbons and a transverse fiber; (3) a postciliary microtubular ribbon, initially sandwiched by two fibers, which gives rise to longitudinal subpellicular microtubules extending posteriorly for a distance of some four or five basal bodies; and (4) a system of overlapping subkinetal microtubules. A three-dimensional reconstruction is included. The somatic cortex of S spathula is similar to that reported for other Haptorida of the ciliate subclass Gymnostomata.     

An electron microscopical study of epididymal epithelium of rats treated with gonadotropic hormone

The ultrastructural modifications of the epithelial cells of rat corpus epididymis stimulated with gonadotropic hormone were studied. The structural variety of the cells depending on functional conditions becomes more prominent 6 h after the injection of gonadotropic hormone. Light large cells have one or often two nucleus-containing bing nucleoli, in their cytoplasm there are numerous vesicles, a well-developed Golgi apparatus, other organelles and lysosomal bodies. Some other cells are filled with many large vacuoles of different density, dense bodies and vesicles. Cells of another type which are in the majority show an unusually active structure reflecting the function of synthesis. The more prominent nucleolus is associated to clumps of chromatin. Their apical cytoplasm is filled by a structure related to absorption. The whole remaining part of their cytoplasm is covered with a very extensive Golgi apparatus and a very well developed granular endoplasmic reticulum. The extremely enlarged cisternae of this reticulum were found to be very closely applied to the basal cell membrane. There is a flocculent material inside the cisternae. Similar material is observed in the extracellular medium under the basal membrane. The epithelium seems normal 10 h after the injection of hormone, but large light cells make up the majority of them.     

A dense cell in the epithelium of the gill lamellae of the brook trout, Salvelinus fontinalis (Mitchill)

A cell was found in freshwater brook trout which was similar to a chloride cell as it was mitochondria-rich with an extensive tubular network, but differed in having a dark cytoplasm, large round vesicles in the apical cytoplasm, and large membrane-bound bodies near the nucleus. The base of the cell was separated from the basement membrane by cytoplasm from another epithelial cell. The cell was more rarely found in trout adapted to brackish water and salt water.     

Histochemical and Ultrastructural Analyses of the Epithelial Cells of the Body Surface Skin from the Terrestrial Slug, Incilaria fruhstorferi

Dorsal and ventral epithelium of the terrestrial slug, Incilaria fruhstorferi, is simple and consists of five cell types: microvillous, ciliated, round mucous, tubular mucous and channel. Microvillous cells were similar to human intestinal epithelial cells morphologically and functionally. At the base of microvilli, pinocytic vesicles which ultimately fused to form larger vacuoles, or multivesicular bodies were present. At the edge of tail or mouth, ciliated epithelial cells possessed the typical axonemes (9 plus 2 arrangement of microtubles). Mucous secretory cells were either tubular or round and their granules were membrane-bound and secreted by exocytosis. Granules of round mucous cells were proteinaceous but those of tubular cells were acidic mucopolysaccharides. Channel cells were elongate U-shaped and the central lumen was filled with a large amount of fluid (hemolymph). The function of channel cells is thought to remove hemolymph accumulated during hyperhydration. Our experiments of some markers-injection revealed that the fluid containing large molecules passed transcellularly from the hemolymph, across the basal or side region of the cell and into the central lumen. These results suggest that channel cell of the slug skin and vertebrate nephron showed some parallels in structure and function.     

Fusion of lamellar body with plasma membrane is driven by the dual action of annexin II tetramer and arachidonic acid

Annexin II has been implicated in membrane fusion during the exocytosis of lamellar bodies from alveolar epithelial type II cells. Most previous studies were based on the fusion assays by using model membranes. In the present study, we investigated annexin II-mediated membrane fusion by using isolated lamellar bodies and plasma membrane as determined by the relief of octadecyl rhodamine B (R18) self-quenching. Immunodepletion of annexin II from type II cell cytosol reduced its fusion activity. Purified annexin II tetramer (AIIt) induced the fusion of lamellar bodies with the plasma membrane in a dose-dependent manner. This fusion is Ca2+-dependent and is highly specific to AIIt because other annexins (I and II monomer, III, IV, V, and VI) were unable to induce the fusion. Modification of the different functional residues of AIIt by N-ethylmaleimide, nitric oxide, or peroxynitrite abolished AIIt-mediated fusion. Arachidonic acid enhanced AIIt-mediated fusion and reduced its Ca2+ requirement to an intracellularly achievable level. This effect is due to membrane-bound arachidonic acid, not free arachidonic acid. Other fatty acids including linolenic acid, palmitoleic acid, myristoleic acid, stearic acid, palmitic acid, and myristic acid had little effect. AIIt-mediated fusion was suppressed by the removal of arachidonic acid from lamellar body and plasma membrane using bovine serum albumin. The addition of arachidonic acid back to the arachidonic acid-depleted membranes restored its fusion activity. Our results suggest that the fusion between lamellar bodies with the plasma membrane is driven by the synergistic action of AIIt and arachidonic acid.     

Ovariolar 'basal body' development and physiological age of the mosquito Aedes aegypti

Abstract. Dissection of the ovaries of the mosquito Aedes aegypti (Diptera: Culicidae) revealed, in each ovariole, a group of seven to nine specialized epithelial cells in a region of the calyx wall that is enclosed by the end of the ovariolar sheath. This group of cells is termed the basal body. During ovulation, the mature oocyte passes from the ovariole into the calyx lumen through the basal body. Subsequently, granulation occurs in the basal body cells. The granular basal bodies differ from all previously described ovarian structures. In multiparous females the size and optical density of the granular basal bodies increase after each ovulation. Examination of the granular basal bodies in intact ovaries, stained with neutral red, provides an easy method for distinguishing parous from nulliparous females, and has potential as a new method of age grading.     

Fine structure of the rectal pads in the desert locust Schistocerca gregaria with reference to the mechanism of water uptake

The rectal pads of Schistocerca gregaria are composed of three different cell types: epithelial, secondary and junctional cells. The rectal pads are interconnected by simple rectal cells and both are lined internally by a articular intima. The epithelial cells exhibit extensive infoldings of the apical plasma membranes that are closely associated with mitochondria. Their lateral plasma membranes are highly folded around large mitochondria and enclose intercellular channels and spaces. They are united by belt and spot desmosomes, septate junctions, gap junctions and scalariform junctions, but terminate in a basal syncytium without contacting the basal plasma membranes. The apical and basal cytoplasm contain coated vesicles, dense tubular elements, multivesicular bodies and lysosomes, suggesting receptor-mediated endocytosis of small peptide molecules into the epithelial cells. The apical membrane infoldings of the secondary cells are also associated with large mitochondria. Their basal plasma membranes are covered by connective cell processes and connected with them by spot desmosomes which may be involved in solute recycling. The presence of neurosecretory-like axons near the secondary cells suggests that they exert local control on the function of these cells. The ultrastructural details are examined in relation to their role in solute and water transport.     

Features of the structure of the cornea of fish]

Electron microscopy of the cornea have been performed in marine fishes. Some structural peculiarities in the cornea of prebottom-dwelling fishes have been demonstrated. In Gobius fluviatilis (Pallas), Gobius (Proterorhinus) marmoratus (Pallas), glossa Platichthys flesus (L) the cornea is double and there is an iridescent layer. It is stated that cells of the iridescent layer play an active part in the formation of the endothelial basal membrane. In Syngnathus nigrolineatus, according to its living conditions, the cornea has a rather simple composition and structure. In the cornea of fishes either epithelial or endothelial basal membrane (Gobiidae, Syngnathus nigrolineatus) or a wide electron opaque epithelial membrane (Blennius tentacularis) or else, besides this, the Bowmen membrane (glossa) can be formed.