Showing papers on "Ultrastructure published in 1977"

The Ultrastructure of the Osteoclast and its Functional Implications

Abstract: Recent findings on the ultrastructure of the osteoclast indicate that special attention should be given to the ruffled border, clear zone, and the vacuoles and vesicles of the cell and their significance for the mechanism of breakdown of bone matrix. The ruffled border is seen as an extensive area of cell surface where secretion of enzymes as well as uptake of matrix components takes place. The clear zone encircles the ruffled border completely and thus forms an integral part of the resorbing apparatus. Vacuoles and vesicles are thought to secret enzymes as well as take up extracellular material and possible digest or transport these products in the cell. The changes that occur in the ultrastructure of the osteoclast after exposure to parathyroid hormone and calcitonin indicate an important role of the ostioclast in bone metabolism. The cell can increase its activity very rapidly in response to parathyroid hormone, and decrease its activity in response to calcitonin.

Midgut ultrastructure of Culex tarsalis (Diptera:Culcidae) before and after a bloodmeal☆

Abstract: The midgut ultrastructure of raisin- and blood-fed female mosquitoes, Culex tarsalis Coquillett, was examined. The raisin-fed midgut is characterized by: (1) large nuclei, (2) small mitochondria, (3) short segments of rough endoplasmic reticulum, (4) rough endoplasmic reticular vesicles in the posterior midgut only, and (5) increased autophagic activity with age. Blood feeding elicits drastic changes in midgut epithelial structures: (1) nuclei are smaller, (2) mitochondria are much enlarged, (3) rough endoplasmic reticular vesicles disappear, (4) rough endoplasmic reticular whorls appear, (5) residual lyosomal figures are abundant, and (6) an intercellular accumulation of an electron-opaque material is noted. The significance of rough endoplasmic reticular whorls and vesicles in bloodmeal digestion is discussed. In addition, the concept of a functional host ‘gut barrier’ to infection by pathogens is examined as related to a possible by-pass mechanism.

Ultrastructure of epithelial cells in the epididymal region of the turkey (Meleagris gallopavo).

Abstract: SUMMARY The epithelial cells in the epididymal region of the turkey were classified ultra­structurally by electron microscopy Six cell types were described: squamous and low cuboidal cells of the rete testis, non-ciliated Type I and ciliated cells of the ductuli efferentes and connecting ductules, non-ciliated Type II cells of the ductus epididymidis, and basal cells occasionally found in all the ducts except the rete The squamous cells were more electron-dense and contained fewer organelles than the cuboidal cells The Type I cells secreted blebs of material into the ductal lumen and contained numerous mitochondria, extensive rough and smooth endo­plasmic reticulum and well developed Golgi complexes, indicating active apocrine secretion The Type I cells also contained large zymogen-like granules and numerous rod-shaped bodies which were considered to be lysosomes associated with an absorptive function The Type II cells had small Golgi complexes and numerous lipid vesicles Ciliated cells presumably concerned in the transport of spermatozoa contained numerous mitochondria in the apical cytoplasm, lobulated nuclei and perinuclear fibrillar bundles Lysosomal-like bodies and large cytoplasmic vacuoles indicated an absorptive function The basal cells were smaller and more electron­dense than other cell types, and rested directly on the basal lamina This study has shown that the epithelial cells of the ductuli efferentes appear to be the most active cells of the turkey epididymal region They apparently function in the transportation of spermatozoa, resorption of luminal fluids, and the secretion of proteinaceous material

Ultrastructure of the Organ of Jacobson and Comparative Study with Olfactory Mucosa

Abstract: The organ of Jacobson has been studied in lizards, rats, guinea pigs, rabbits and dogs by means of embedding in nitrocellulose, semithin sectioning, and electron microscopy. The various elements of the organ in the species studied have been analysed and a comparative study carried out between the sensory portion of the organ and the olfactory epithelium.

Ultrastructure of the feline area postrema

Abstract: The morphology of the feline area posterma (AP), a circumventricular organ, has been studied by scanning (SEM) and transmission electron microscopy (TEM). In SEM preparations the boundary of the AP was sharply delineated by the absence of kinocilia. Microvilli were numerous and seemed to be concentrated at the junction between ependymal cells, imparting a polygonal surface pattern superimposed on cell boundaries. Some cell processes were present on the AP surface, but no supra-ependymal cell bodies could be seen over the AP proper. In TEM preparations the AP was characterized by blood vessels with distinct perivascular spaces. These spaces contained fibroblasts and collagen, and were limited by basal laminae. Capillary endothelial cells were typically fenestrated and contained numerous pinocytotic vesicles. Bulbous ending of attenuated cellular processes terminated on the external basal laminae of AP vasculture. Some of these endings could be traced to the cells covering the ventricular surface of the AP. These cells demonstrated several features co-mon to ependymal cells which have been identified as tanycytes. The presence of small neurons frequently seen in groups of three or four confirm previous light microscopic studies. Synapses predominantly of the axodendritic variety were observed, and both dense cored and clear cored vesicles were present on the same ending. Myelinated and unmyelinated axons were a consistent finding in the AP with the former being more abundant in the lateral margins of the AP and in the region of the area subpostrema. The chemoreceptive function of the AP has been widely accepted; however, studies indicate that it is not possible to distinguish species possessing an emetic reflex on the basis of ultrastructural morphology. The possibility that the AP serves functions in addition to emetic chemoreception is considered.

An ultrastructural and cytochemical study of the wall-membrane apparatus of transfer cells using freeze-substitution

Abstract: A freeze-substitution technique is described which enables the ultrastructure of certain types of plant transfer cells to be preserved with minimal ice crystal damage. The ultrastructure of transfer cells fromFunaria, Lonicera, andSenecio after freeze-substitution has been compared with that of glutaraldehyde-osmium fixed material. The irregular clear zone between wall and plasma membrane, present in conventional preparations, is absent in freeze-substituted tissue. It is proposed that this interfacial zone is an artefact caused by expansion of wall ingrowth material during conventional fixation procedures. In transfer cells with a complex wall labyrinth the swelling of wall material severely disrupts the true structure of the wall-membrane apparatus and results in a large decrease in the surface to volume ratio of the protoplast. These findings are supported in the case ofFunaria by a freezefracture study. The reactivity of the plasma-membrane to the PTA/chromic acid stain is enhanced in freeze-substituted material. Use of theThiery silver proteinate reagent in conjunction with freeze-substitution has revealed marked differences between the wall ingrowths ofFunaria sporophyte haustorium transfer cells and those ofLonicera nectary trichomes.

Origin and Ultrastructure of Cells in Vitro

Abstract: Publisher Summary This chapter discusses the origin and ultrastructure of cells in vitro. The chapter discusses those features that are particularly suitable for electron microscope investigation, and in particular the changes in ultrastructure due to in vitro culture. Ultrastructural evidence, confirmed by functional studies and animal inoculation of cultured cells has shown that differentiated epithelial and mesenchymal cells can be maintained in primary culture or in organ culture for many months. As a rule, there is a gradual loss of differentiated function, particularly if its maintenance is dependent on the endocrine environment, but differentiated structure may sometimes be retained. Most, if not all, epithelial cell strains or lines established from normal tissues, usually by enzyme selection techniques, produce tumors on reinoculation into animals. Most mesenchymal cell lines or strains established from normal tissue are similar to each other in ultrastructure. Two cell types predominate in these cultures, although transition forms may occur. The proportion of the different cell types may vary between cell lines. Depending on species of origin these cells may undergo neoplastic transformation or in vitro senescence. The cells are probably derived from endothelial cells and pericytes. Mesenchymal and epithelial cells with differentiated characters can be maintained as cell lines from a small proportion of tumors, so that there is some as yet unexplained relationship between neoplastic change and the ability to survive in vitro.

Ultrastructure of human endometrial epithelium in monolayer culture with and without steroid hormones

Abstract: Colonies of cells of epithelioid appearance were identified in monolayer cultures grown up to 50 days from normal human endometrial cell suspension obtained by a method designed to insure a maximum harvest of glandular cells Groups of these cells were separated from stromal cells by means of cloning cylinders Studies comparing the ultrastructure of cells of this type to fresh endometrial tissue revealed a number of similarities The morphological characteristics common to both types of samples included junctional complexes, perinuclear microfilaments and microvilli with glycocalyx Other common features were prominent nucleoli, well developed Golgi, rough endoplasmic reticulum and membrane-bound electron-dense bodies in the cytoplasm A stripping technique applied to the fetal bovine serum used in the nutrient medium made it possible to initiate cultures in a steroid-free environment and to maintain them in the presence of the specified concentration of estradiol and/or progesterone Isolation of epithelial cells of endometrium in monolayer culture may provide a useful model system in which to study the specific effects of steroid hormones on cellular function and differentiation

The Ultrastructure of Kranz Cells in the Family Cyperaceae

Abstract: The anatomy of the leaves and ultrastructure of the photosynthetic cells of 18 Cyperus and five Fimbristylis species with Kranz anatomy have been examined and described The Kranz cells are all centripetal to the mestome sheath, and their ultrastructure conforms to the pattern previously reported in NADP-ME-type species, which are characterized by high NADP malic enzyme activity and form one of three subgroups of C4 pathway species based on differing C4 acid decarboxylating systems In some Cyperus species the peripheral reticulum is arranged in radial bands of regular vesicles in denser staining stroma, alternating with radial bands showing less regular organization and staining less deeply; Fimbristylis never shows this arrangement

Cell death in developing skeletal muscle: Histochemistry and ultrastructure

Abstract: The histological, histochemical and ultrastructural features of cell death in the normal human foetus are described. The age range of the foetuses was 7 to 16 wk. Cell death was observed in all foetuses between 10 and 16 wk. On the basis of these findings it is suggested that disintegration of cell membrane may be a crucial factor in this process. Acid phosphatase activity and phagocytosis of cell debris are evidently not the main means of disposal of degenerate cell products. The possible relevance of cell death in embryogenesis for dystrophic processes is discussed.

Observations on the regulation of cell volume and metabolic control in vitro; changes in the composition and ultrastructure of liver slices under conditions of varying metabolic and transporting activity.

Abstract: Liver slices incubated at 1 °C underwent swelling of both cellular and intercellular compartments, as judged by electronmicroscopy. The ultrastructure showed marked changes, including disorganization of the cytocavitary network and plasma membrane and alterations of mitochondria. Restoration of metabolically favorable conditions (oxygenated medium at 38 °C) caused a nearly complete recovery of ultrastructure closely associated with extrusion of water; measurements of inulin space and electronmicroscopy both indicate a recovery of cell volume, with intercellular spaces remaining somewhat expended. The fluid lost was a roughly isotonic solution of Na+ and Cl−, while K+ was reaccumulated in exchange for Na+. Cyanide prevented recovery. Ouabain and oligomycin each partially prevented fluid extrusion, but had little effect on ultrastructural recovery except to induce intracellular vesicles containing particles of thorium dioxide derived from sinusoidal spaces. The vesicles were, however, markedly different in form with each inhibitor. There are, thus ouabain-sensitive and-insensitive components of volume regulation; the former appears to depend on the coupled transport of Na+ and K+ and the latter, we suggest, on a secretion of Na+ and Cl− into vesicles which release their contents into the bile canaliculi by an oligomycin-sensitive mechanism. Mitochondria showed conformational changes between orthodox and condensed forms, but these could not be directly related to tissue energy states; the numbers of mitochondrial dense granules bore a closer relation to tissue ATP.

Pneumocystis carinii in vitro: A study by scanning electron microscopy.

Abstract: Pneumocystis carinii is a parasitic microorganism which induces an often fatal pneumonitis in a variety of compromised patients (e.g., premature infants, those with congenital immune deficiency disorders, those therapeutically immune suppressed, etc.). Organisms derived from murine sources were cultivated in vitro on monolayers of primary embryonic chick epithelial lung cells. The infected cultures were then examined by scanning electron microscopy. An examination of the surface ultrastructure revealed pleomorphic organisms which were not only attached to host cells with anchoring fibers but also connected to other parasites via fine fibrils. Another type of fine fibril was observed which may play a role in the organism's nutrition.

Morphology and ultrastructure of Crenothrix polyspora Cohn.

Abstract: Naturally grown cell material of Crenothrix polyspora from the well of a waterworks was studied by means of phase-contrast and Nomarski interference microscopy as well as by transmission electron microscopy. The material consisted of clusters of sheathed filaments up to 2 cm long. Propagation forms observed were nonmotile, spherical cells that arose by simple ("macrogonidia") or multiple ("microgonidia") septation of the filamental tips. Ultrastructural analysis revealed Crenothrix to be procaryotic and gram negative, with several layers of sheath material surrounding the filaments. On thin sections, individual cells had elaborate membrane systems in the form of lamellar stacks. They resembled thylakoids of photosynthetic bacteria. Spectrophotometric analysis gave no indication of photosynthetic pigments. The cells also contained large hexagonal bodies, rod-shaped fibrillar elements, and polyphosphate granules.

Ultrastructural and histochemical differences in cell surface properties of strain-specific and nonstrain-specific TA3 adenocarcinoma cells.

Abstract: Transmission and scanning electron microscopy and histochemical and biochemical methods were used to investigate differences in cell structure and cell surface properties between the strain-specific TA3-St and nonstrain-specific TA3-Ha ascites sublines of the TA3 murine mammary adenocarcinoma. The TA3-St subline is lethal only to the syngeneic strain A mouse (the strain of origin), whereas the TA3-Ha subline is lethal even to foreign species. In contrast to the TA3-St cell surface, which has numerous folds and irregular microprojections, the TA3-Ha cell has abundant long microvilli of uniform dimensions. An extensive cell surface coat which resembles the "fuzz" coat found on microvilli of normal epithelium was present on the TA3-Ha, but not on the TA3-St cells. After routine fixation, the surface coat of the TA3-Ha cell usually appeared as a filamentous network extending 30-50 nm from the plasmalemma; occasionally, longer filamentous or rod-like structures were found extending 200-400 nm from the plasmalemma. The cell coat material was more extensive on the microvilli than on the intermicrovillous membranes. Free virus-like particles associated with TA3-Ha cells have a similar-appearing surface coat on their outer membranes. The density of surface anionic sites, determined with polycationic ferritin, was greater on the TA3-Ha than on the TA3-St cell surface, consistent with the presence at the TA3-Ha cell surface of several-fold more neuraminidase-susceptible sialic acid groups. The observed surface features of the nonstrain-specific TA3-Ha cell, in comparison to the strain-specific TA3-St cell, are consistent with the suggestion that sialic acid-rich glycoproteins at the TA3-Ha cell surface mask histocompatibility antigens and enhance the ability of malignant cells to invade foreign species.

Ultrastructure of a chain-forming diatom phaeodactylum tricornutum1

Abstract: The ultrastructure of a chain-forming clone of the polymorphic diatom Phaeodactylum tricornutum Bohlin has been studied by scanning and transmission electron microscopy. Both fusiform and tri-radiate cells are capable of forming chains. The cells, lacking any silica shell, are attached to each other at the central region of the theca, leaving the arms free. Neither homogenization nor sonication completely disrupts the chains. The attachment is due to fusion of the cell wall in the central region of the cell during cell wall deposition. This fusion results from failure of the cytoplasmic cleavage furrow to separate the plasma membranes of the two daughter cells sufficiently so that a single wall is deposited instead of two separate walls. Possible explanations for this are discussed.

The ultrastructure of the posterior midgut caecum of Pachygrapsus crassipes (Decapoda, Brachyura) adapted to low salinity

Abstract: The effects of salinity adaptation and of composition and tonicity of fixatives upon the ultrastructure of the posterior midgut caecum (PMC) of Pachygrapsus crassipes have been studied. The PMC epithelium consists of a single layer of columnar cells with a microvillous border. The apical cytoplasm contains numerous mitochondria, lysosomes, and much smooth endoplasmic reticulum. Rough endoplasmic reticulum and Golgi apparatus are situated in the perinuclear cytoplasm. This epithelium resembles other transporting epithelia in that the basal cytoplasm has an extensive system of branched tubules formed from invaginations of the lateral and basal plasma membrane. Numerous mitochondria are associated with the basal tubular system. To determine the possible contribution of the PMC to the osmoregulatory ability of Pachygrapsus , the ultrastructure of the PMC from animals adapted to 40, 50, 100 and 150% sea water was investigated. Enlargement of basal tubules and intercellular spaces at low salinity, suggestive of fluid-transport activity, was found to be an artifact of fixation. The most consistent response when animals were acclimated to dilute salinities was that some basal mitochondria assume a more complex shape, usually appearing as rings in cross sections of the caecum. A hypothesis concerning the functional significance of these mitochondria is proposed.

Ultrastructure of osteoblastoma.

Abstract: The ultrastructure of three cases of osteoblastoma is described. The osteoblasts resemble normal osteoblasts with a few exceptions: irregular, indented nuclei, and occasional mitochondria with curved cristae and electron-lucent areas. The osteocytes and osteoclasts basically resemble their normal counterparts. There are also osteoprogenitor cells in different stages of maturation, some containing glycogen. The ultrastructure of an additional case histologically classified as aggressive osteoblastoma is described. It is essentially similar to the previous three cases of typical osteoblastoma. The only exception is the presence of osteoblasts with electron-lucent nuclei and less prominent organelles than the typical osteoblastoma cells have markedly indented and multilobed nuclei, dilated rough endoplasmic reticulum and lipid droplets. However, these differences from osteoblastoma cells are not pathognomonic. The final diagnosis of osteoblastic tumors rests at the light microscopy level.

Ultrastructural observations of X-ray induced chromatid gaps

Abstract: Summary A combination of light microscopy, transmission electron microscopy of whole-mount preparations and sectioned material, and scanning electron microscopy was employed to examine the fine structure of X-ray-induced gaps and breaks in mammalian chromosomes, in an effort to determine the true nature of these aberrations. The results suggest that, rather than being completely separate phenomena, gaps and breaks are different manifestations of the same events, and that gaps may be incomplete breaks. It was determined that light microscopy alone is inadequate for making accurate quantitative assessments of these aberrations, and it is therefore proposed that electron microscopy be used to supplement light microscopy for the analysis of gaps and breaks.

The ultrastructure of cell walls in Enteromorpha intestinalis (L.) link

Abstract: Using transmission electron microscopy, the process of cell wall development following cytokinesis is described. Three distinct components appear to be localized in the wall and these are discussed in relation to previous work. In older cells the walls are stratified and the origin of the layers is described. The outer layers of wall are continually being shed and it is suggested that this process prevents epiphytes persisting on this species of alga.

The ultrastructure of the interfollicular epidermis of the hairless (hr/hr) mouse

Abstract: The ultrastructure of horny cells in the interfollicular epidermis of the hairless mouse and in the mouse with hair has been studied with particular emphasis on changes in the cytoplasm through the horny layer Horny cells from the two strains have a similar appearance, and the horny layer can be divided into three sublayers, each with a different ultrastructure It is suggested that in vivo the same arrangement of densely packed filaments and fibrils which represents the keratin pattern in the basal sublayer is preserved throughout the horny layer However, the filaments and interfilamentous substance seem to undergo a continuous transformation, which possibly results in a disintegration of the filaments when desquamation of the uppermost cell takes place

Ascospores, Germ Pores, Ultrastructure, and Thermophilism of Chaetomium

Abstract: SUMMARY Ascospores of 15 isolates of Chaetomium thermophile were compared with those of 105 other Chaetomium species by use of light microscopy and scanning electron microscopy. Two stable characteristics distinguished C. thermophile ascospores from those of all other Chaetomium species examined: a papillate germ pore and pustulate surface ornamentation. Transmission electron microscopy revealed multilayered walls in ascospores of C. semen-citrulli and C. thermophile. In addition, germ pores were confirmed as thin areas in ascospore wall layers. Germinated ascospores of C. semen-citrulli contained several nuclei, mitochondria, fibrillar bundles, vacuoles, and glycogen-like particles.

Ultrastructural and functional changes in pancreatic acinar cells during autolysis.

Abstract: Effects of anoxemic cell injury on rat pancreatic acinar cells were studied in a preparation where tissue samples were incubated at temperature between 18–20° C in a moist atmosphere for 0, 0.5, 1, 3, 6, 12, and 24 h in vitro. Electron microscopy revealed that disintegration of acinar cells began by swelling of various cell compartments and gradual breakdown of cell membranes. Zymogen granules remained morphologically intact for at least 3 h. There were no signs of increased autophagic activity during the period of observation. Myelin figures and other membranous remnants of disintegrated cells, together with individual cells and cell organelles whose morphology was relatively well preserved were seen even after 24 h incubation. The secretory response of acinar cells to pancreozymin stimulation, as measured by amylase release into the incubation medium in vitro, decreased progressively closer to zero during 12 h autolysis. No active trypsin could be detected in the tissue samples during the 24 h observation time. It was concluded that during hypoxic autolysis at room temperature between 18–20° C in vitro:

Dorsal-ventral differentiation in Simonsiella and other aspects of its morphology and ultrastructure

Abstract: The morphology and ultrastructure of the aerobic, Gram-negative multicellular-filamentous bacteria of the genus Simonsiella were investigated by scanning and transmission electron microscopy. The flat, ribbon-shaped, multicellular filaments show dorsal-ventral differentiation with respect to their orientations to solid substrata. The dorsal surface, orientated away from the substrate, is convex and possesses an unstructured capsule. The ventral surface, on which the organisms adhere and glide, is concave and has an extracellular layer with fibrils extending at right angles from the cell wall. The cytoplasm in the ventral region contains a proliferation of intracytoplasmic membranes and few ribosomes in comparison to the cytoplasm in other parts of the cell. Centripetal cell wall formation is asymmetrical and commences preferentially in the ventral region. Quantitative differences in morphology and cytology exist among selected Simonsiella strains. Functional aspects of this dorsalventral differentiation are discussed with respect to the colonization and adherence of Simonsiella to mucosal squamous epithelial cells in its ecological habitat, the oral cavities of warm-blooded vertebrates.

Focal epithelial hyperplasia in a group of South Africans: Its ultrastructural features

Abstract: . Election microscopic observation of samples of tissues from lesions diagnosed as focal epithelial hyperplasia revealed the presence of viral particles in six (possibly seven) of 13 cases examined. Viral particles were intranuclear and varied from sparsely scattered to densely packed. A crystalline arrangement was present in one case. The chromatin of affected cells was typically condensed into clumps and thick bands, and the nuclear membrane was usually absent in pronounced cases. The nuclei of the basal and prickle cells were frequently indented and the chromatin peripherally condensed. Numbers of lysosomal-like organelles were observed in many of these cells. The ballooning epithelial cells with their mitosis-like aberrations observed with light microscopy consisted of a rim of tonofilmaments and organelles and a homogeneous granular center interspersed with dense areas. It is suggested that the nuclear characteristics and numerous lysosomes observed in basal and prickle cells are cellular changes induced by the viral infection and that the mitosis-like aberrations represent a bizarre and arrested form of mitosis.

Ultrastructure of the gut neurotensin cell

Abstract: SummaryIn mammals, neurotensin cells occur scattered in the epithelium of the jejunum-ileum. In chicken, neurotensin cells are abundant in the region of the gizzard-duodenal junction (antrum) where they occur intermingled with numerous somatostatin and gastrin cells. The neurotensin cells in chicken, dog and man were identified at the electron microscopic level by immunocytochemistry, using the consecutive semithin/ultrathin section technique. They contain numerous electron dense cytoplasmic granules, predominantly in the basal portion of the cell. It was shown that these granules are the storage site for neurotensin. The neurotensin granules are round, highly electron dense and of about the same size in the different species examined (mean diameter 260–290 nm). in dog and man the granules have a tightly applied surrounding membrane while in the chicken a relatively electron lucent zone separates the electron dense core from the granule membrane. The ultrastructure of the neurotensin granules in chicken is some-what reminiscent of that of the gastrin granules. The mean diameter of the gastrin granules in chicken antrum is 230 nm; for the somatostatin granules the mean diameter is 305 nm.