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Showing papers on "Ultrastructure published in 1976"


Journal ArticleDOI
TL;DR: The ultrastructural features of nerve cell bodies and axon profiles within Auerbach's plexus in the stomach, ileum, caecum and colon of the guinea-pig have been examined and some correlation between types of axon profile and two types of nerve body was recognized.
Abstract: The ultrastructural features of non-neuronal cells associated with Auerbach's plexus in the stomach, ileum and colon of the guinea-pig have been examined. Apart from Schwann, mast and interstitial or fibroblast-like cells, two other cell types are described that do not appear to have been reported previously. Of these two cell types, one was found external, but close to, the plexus and contained large granular vesicles. The other cell type contained numerous glycogen-like granules, was situated close to or within axon bundles and had processes that extended within and peripheral to nerve bundles as well as being close to smooth muscle cells. Although axon varicosities were opposed to both the processes and cell body of the second type of cell, synaptic-like contacts were not observed.

246 citations


Book ChapterDOI
TL;DR: There is evidence from cytogenetic studies that stem cells differentiating into lymphocytes differ from the so-called pluripotent cells which give rise to myeloid cell lines.
Abstract: Publisher Summary This chapter deals with ultrastructural and cytochemical studies of human normal hemic cells, excluding a detailed analysis of pathological maturation. However, two types of abnormalities involving specific organelles of maturing cells are described (mitochondria with iron accumulation in erythroblasts, and crystalline granules in some leukemic granulocytes). Most of the maturation steps of immunocytes take place outside the bone marrow, that is, in the thymus and in other lymphoid tissues, and very few data are available that can distinguish on an ultrastructural basis between marrow lymphocytes and others. Furthermore, there is evidence from cytogenetic studies that stem cells differentiating into lymphocytes differ from the so-called pluripotent cells which give rise to myeloid cell lines. Numerous studies have been developed for the detection of enzymatic activities in monocytes operating in the process of intracellular digestion that follows endocytosis. At the light microscope level many reactions are available, some of which may be used as specific markers for cell line. At the ultrastructural level, cytochemical studies have established that enzymatic activities are segregated in the endoplasmic reticulum and the golgi complex, and stored into granules. With available techniques, peroxidase and some hydrolases can be detected.

154 citations


Journal ArticleDOI
01 May 1976-Cancer
TL;DR: It is suggested that mucin and ultrastructural changes described in the “TR” zone may indicate a failure in the normal process of cell differentiation along the crypt, reflecting a cellular response to unknown stimuli rather than a local secondary effect of tumor growth.
Abstract: The material was taken from surgical specimens of large intestine resected for carcinoma. A parallel study by electron microscopy and mucin histochemistry was made on fragments from “transitional” (TR) mucosa (adjacent to carcinoma) and “normal” (N) mucosa (remote from the tumor). These were compared with similar studies on the mucosa from control individuals. Histochemically, the “TR” mucosa shows an increase in sialomucins as compared with the “N” and control mucosae, where sulphomucins normally predominate. At the ultrastructural level, the “TR” mucosa is characterized by the following changes which may precede the histochemical variations: A) alteration in the relative proportions of the different cell types, along the crypt, with a persistence of immature and intermediate cells at higher levels of the crypt than in the control. Mature absorptive cells are fewer and bear an inverse relationship to intermediate cells. Goblet cells are increased in number and size. B) Appearance of electron-dense bodies 0.15–0.3μm in diameter and membrane limited. C) An elaborated and enlarged Golgi zone showing increased secretory activity. It is suggested that mucin and ultrastructural changes described in the “TR” zone may indicate a failure in the normal process of cell differentiation along the crypt. Previous work7,8 further suggests that the mucin changes may be primary, reflecting a cellular response to unknown stimuli (i.e., carcinogens) rather than a local secondary effect of tumor growth. As for the ultrastructural features in the “TR” mucosa, the secondary effect cannot be excluded at the present.

139 citations


Journal ArticleDOI
TL;DR: SDS-polyacrylamide gel electrophoresis shows that the tissue dossociation technique does not lead to major deletions of cell proteins and that the pattern of perikaryal protein synthesis in vitro closely resembles that in vivo.

134 citations


Journal Article
TL;DR: The observations support the concept that the neoplastic cell of malignant mesothelioma can differentiate into a number of cell lines.
Abstract: Eleven cases of malignant diffuse mesotheliomas, histologically classified into two groups, epithelial (5 pleural and 3 peritoneal) and biphasic or mixed (2 pleural and 1 peritoneal) forms, were stuied by electron microscopy to elucidate their ultrastructural characteristics. The neoplastic cells of the epithelial forms were varied in ultrastructure, from well differentiated (marked by polarity, micovilli, glycogen granules, junctional structures, tonofilaments, intracellular vacuoles, and a basement membrane) to poorly differentiated (which lacked some of these epithelial characteristics). In four of eight instances in epithelial type tumors, nonepithelial or mesenchymal neoplastic cells were recognized. The biphasic or mixed cases included three major cell types: epithelial, atypical epithelial, and mesenchymal. It appeared that there were transitional forms among the three cell types. The observations support the concept that the neoplastic cell of malignant mesothelioma can differentiate into a number of cell lines.

134 citations


Journal ArticleDOI
TL;DR: The ultrastructure of Mycoplasma pneumoniae M129 was studied by using specialized staining methods for thin-section transmission electron microscopy and found that M. pneumoniae was enveloped in an extracellular mucoprotein layer that was especially concentrated around its terminal structure.
Abstract: The ultrastructure of Mycoplasma pneumoniae M129 was studied by using specialized staining methods for thin-section transmission electron microscopy. Nucleic acid was shown in the cytoplasmic granules and fibrillar material in the nuclear region. The central filament of the highly structured tip contained basic protein. With one method of fixation, parallel filaments were seen in the central core. M. pneumoniae was enveloped in an extracellular mucoprotein layer that was especially concentrated around its terminal structure.

113 citations


Journal ArticleDOI
TL;DR: In this paper, three cases of giant cell carcinoma of lung and six other lung carcinomas with large atypical cell formation were studied by both light and electron microscopy.

99 citations


Journal ArticleDOI
TL;DR: These studies have provided the first correlative SEM and TEM analyses of solid human tumor cells of diverse pathologic types in vitro and the cytoskeleton of normal fibroblasts was shown to be well organized, with parallel orientation of microfilaments, filaments, and microtubules.
Abstract: Human tumors of a variety of histopathologic types have been established in tissue culture. The surface features of these cell lines were investigated by scanning electron microscopy (SEM) with the use of new techniques for specimen preparation. Tumor cells demonstrated striking degrees of surface activity with numerous microvilli, filopodia, blebs, and ruffles. Intercellular contacts were also prominent in cultures of most solid tumors observed by SEM. At low cell density, normal human fibroblasts exhibited some surface features such as microvilli and blebs, but at higher cell density they lacked extensive surface modifications. By transmission electron microscopy (TEM), the cytoskeleton of normal fibroblasts was shown to be well organized, with parallel orientation of microfilaments, filaments, and microtubules. These structures were also in tumor cells, but they lacked the degree of organization of fibroblasts. Desmosomes were readily demonstrated in normal fibroblasts and carcinoma cells in culture but not in sarcomas, melanomas, or tumors of neural origin. These studies have provided the first correlative SEM and TEM analyses of solid human tumor cells of diverse pathologic types in vitro.

90 citations


Journal ArticleDOI
TL;DR: Striking changes in mitochondrial fine structure accompany the growth of Ankistrodesmus falcatus, Chlorella pyrenoidosa and Scenedesmus quadricauda in culture medium containing cadmium chloride chelated with EDTA and are suggested to be sufficient to deleteriously affect cell metabolism.
Abstract: Striking changes in mitochondrial fine structure accompany the growth of Ankistrodesmus falcatus, Chlorella pyrenoidosa and Scenedesmus quadricauda in culture medium containing cadmium chloride chelated with EDTA. The presence of extremely prominent intramitochondrial dense granules is the most noticeable feature. The granules were interpreted to contain cadmium on the basis of energy dispersive X-ray analysis. While mitochondria of untreated cells appear as ovoid to rod-shaped organelles with either plate-like or tubular protrusions of the inner mitochondrial membrane, those of cadmium-exposed cells contain electron-lucid areas suggesting that the organelles are not very active. Ultrastructural changes in the form of swelling and mitochondrial vacuolation were observed. Additionally, successive stages of mitochondrial degeneration are described. It is suggested that since these alterations in mitochondrial fine structure may be sufficient to deleteriously affect cell metabolism, the mitochondrio...

85 citations


Journal Article
TL;DR: It was concluded that the fine structure and developmental changes in the early sheep embryo are very similar to those of other mammalian species.
Abstract: Sheep embryos were examined with the electron microscope in order to characterize their organelles and the changes that occur during the preimplantation period. The first sign of differentiation of trophoblast cells was the appearance of junctions between external cells at the 16-cell stage. Nucleoli developed a granular component suggesting the synthesis of ribosomal RNA at the 16-cell stage also. Centrioles were seen as early as the 8-cell stage. Intracytoplasmic vesicles were present in large numbers in all cleavage stages but disappeared at blastulation. Mitochondria progressed from a very electron-dense hook- or U-shaped form with a few cristae to a cylindrical or spherical form of light density with many transverse cristae. Microvilli were not seen until the blastocyst stage and then only on the exterior surface of the trophoblast cells. Crystalloid or virus inclusions were not observed. It was concluded that the fine structure and developmental changes in the early sheep embryo are very similar to those of other mammalian species.

84 citations


Journal ArticleDOI
TL;DR: The morphogenesis of Blattella tergal glands, present only in male imagoes and composed of class 3 gland cells, has been studied at the ultrastructural level.

Journal ArticleDOI
TL;DR: It is suggested that damage of basal cell membranes on their dermal side leads to the destruction of basal cells with the subsequent protrusion of epidermal and junctional substances into the dermis, which may result in inflammatory cell infiltration and blister formation.

Journal ArticleDOI
TL;DR: The ultrastructure of plasma cell granuloma, like the histologic and clinical aspects, differs from that of sclerosing hemangioma, pseudolymphoma, and malignant plasma cell tumor affecting the lung.

Journal ArticleDOI
TL;DR: In the rumen ecosystem, bacteria appeared to adhere to plant substrates during degradation by capsule-like material and by small amounts of extracellular material, as well as by the other means not observable by electron microscopy.
Abstract: The degradation of forage cell walls by rumen bacteria was investigated with critical-point drying/scanning electron microscopy and ruthenium red staining/transmission electron microscopy. Differences were observed in the manner of attachment of different morphological types of rumen bacteria to plant cell walls during degradation. Cocci, constituting about 22% of the attached bacteria, appeared to be attached to degraded plant walls via capsule-like substances averaging 58 nm in width (range, 21 to 84 nm). Many bacilli appeared to adhere to forage substrates without distinct capsule-like material, although unattached bacteria with capsules were observed occasionally. Certain bacili appeared to be attached to degraded tissue via small amounts of extracellular material, but others apparently had no extracellular material. Bacilli with a distinct morphology due to an irregularly folded, electron-dense outer layer or layers (about 15 nm thick) and without fibrous extracellular material consituted about 37% of the attached bacteria and were observed to adhere so closely to degraded plant walls that the bacterial shape conformed to the shape of the degraded zone. In the rumen ecosystem, bacteria appeared to adhere to plant substrates during degradation by capsule-like material and by small amounts of extracellular material, as well as by the other means not observable by electron microscopy.

Journal Article
TL;DR: Ultrastructural studies of the rabbit bronchial mucosa revealed that the bronchus-associated lymphoid aggregates could be distinguished from the surrounding tissue, since they were covered with epithelial cells possessing microvilli but not cilia.

Journal ArticleDOI
01 Nov 1976-Cancer
TL;DR: A striking ultrastructural similarity of the tumor cells to those encountered in ethylnitrosourea‐induced malignant schwannomas in rats was noteworthy.
Abstract: The light microscopy and ultrastructure of a malignant eipthelioid schwannoma are described. Characteristic cells resembling perineural elements with various degrees of differentiation were observed. Primitive epithelioid cells contained scant ergastoplasm, and few tubules and filaments, but did have abundant free ribosomes and Golgi membranes. Also noted were junctional complexes and focal fusion of plasma membranes, basal laminae were absent. Better differentiated cells were completely limited by a well-developed basal membrane and had an abundance of intracytoplasmic filaments and multiple pinocytotic vesicles. The intercellular ground substance was composed of numerous fine collagen fibrils and amorphous, basement membrane-like, electron-dense material. A striking ultrastructural similarity of the tumor cells to those encountered in ethylnitrosourea-induced malignant schwannomas in rats was noteworthy.

Journal ArticleDOI
TL;DR: The ultrastructural development of the principal cells in rat small intestine was studied by morphometric analyses in relation to the exact cell position along crypt and villus with gradual increase in absolute size of the total cell, the cytoplasm, the terminal web and of nearly all cell organelles.
Abstract: The ultrastructural development of the principal cells in rat small intestine was studied by morphometric analyses in relation to the exact cell position along crypt and villus. From the bottom to the tip of the crypt, a gradual increase occurred in absolute size of the total cell, the cytoplasm, the terminal web and of nearly all cell organelles. Also, the relative size of the cytoplasm, mitochondria, microvilli and endoplasmic reticulum increased during crypt cell differentiation. No sudden changes in ultrastructure were observed in the so-called “critical decision zone”, normally located halfway up the crypt where the proliferative activity ceases. At the crypt-villous junction a 1.4–3 fold increase in cell size, cytoplasm, terminal web and of most organelles was noted. Expansion of the proliferative cell compartment over the total length of the crypt as occurs during recovery after a low X-irradiation dose (72 h after 400 R) does not affect the normal development of cellular ultrastructure. These findings are discussed in relation to biochemical and cell kinetic data.

Journal ArticleDOI
TL;DR: Second stage larvae of the root-knot nematode, Meloidogyne incognita [(Kofoid and White) Chitwood], were examined to elucidate the ultrastructure of the amphids, which are paired lateral organs believed to function in chemosensory perception.

Journal ArticleDOI
TL;DR: The increase in the number of epidermal filament-containing cells,Epidermal thickness and stratum compactum thickness is correlated with an increased need for protection from abrasion and mechanical damage as the eel moves from a pelagic, oceanic habitat to a benthic, freshwater habitat.
Abstract: The morphology and ultrastructure of the lateral body integument of the leptocephalus, glass eel, pigmented elver, and adult stages of the American eel, Anguilla rostrata, were examined with light and electron microscopy. The integument consists of an epidermis separated by a basal lamina from the underlying dermis. Three cell types are present in the epidermis in all stages. Filament-containing cells, which are the principal structural cell type, are increasingly numerous at each stage. Mucous cells, which secrete the mucous that compose the mucous surface coat, are also more numerous in each subsequent stage and are more numerous in the anterior lateral body epidermis than in the posterior lateral body epidermis of the adult. Club cells, whose function is unknown, are most numerous in the glass eel and pigmented elver. Chloride cells are common in the leptocephalus which is marine and infrequent in the glass eel. They are not present in the pigmented elver and adult which inhabit estuaries and fresh-water. Lymphocytes and melanocytes are also present in some stages. The dermis comprises two layers: a layer of collagenous lamellae, the stratum compactum, and an underlying layer of loose connective tissue, the stratum spongiosum. There is a progressive increase in epidermal thickness at each stage which is paralleled by an increase in the thickness of the stratum compactum. Rudimentary scales are present in the dermis of the adult. The increase in the number of epidermal filament-containing cells, epidermal thickness and stratum compactum thickness is correlated with an increased need for protection from abrasion and mechanical damage as the eel moves from a pelagic, oceanic habitat to a benthic, freshwater habitat. The increase in mucous cell numbers is likewise correlated with an increased need for the protective and anti-bacterial action of the mucous surface coat in the freshwater environment.


Journal ArticleDOI
TL;DR: The ultrastructure of the basal cells of rat lateral and ventral prostate and of dog prostate has been studied and it is not considered to be sufficient evidence to assume any similarity to myoepithelium as has been previously suggested.
Abstract: The ultrastructure of the basal cells of rat lateral and ventral prostate and of dog prostate has been studied. Basal cells from both species appear as undifferentiated cells, characterised by a lack of cytoplasmic organelles and a poorly developed Golgi complex and endoplasmic reticulum. The presence of cytoplasmic filaments and micropinocytosis is not considered to be sufficient evidence to assume any similarity to myoepithelium, as has been previously suggested. Basal cells are instead considered to be precursors of secretory epithelial cells.

Journal Article
TL;DR: In this paper, the ultrastructural detail was detected in structures interpreted as remnants of cell walls, mucilaginous envelopes, cytoplasmic material, organelles, and membranes.
Abstract: The ultrastructure of microfossils from the late Precambrian Bitter Springs Formation has been studied using transmission electron microscopy (TEM); this is the first systematic investigation of the ultrastructure of ultrathin-sectioned, organic microfossils of Precambrian age. The procedure developed for preparing organic microfossils for ultramicrotomy and TEM involves i) acid maceration of a fossiliferous rock sample and ii) alcohol dehydration and resin embedment of the acid-resistant organic residue. Neither chemical fixation nor heavy-metal staining appear to affect the ultrastructure or electron opacity of the cells here studied. The relatively high electron opacity of unfixed and unstained Bitter Springs organisms suggests that they have been diagenetically "carbonized" or enriched in certain heavy elements. Ultrastructural detail was detected in structures interpreted as remnants of cell walls, mucilaginous envelopes, cytoplasmic material, organelles, and membranes. Walls appear as distinct, densely granular bands. Walls of prokaryotes (Myxococcoides, Palaeoanacystis, and Palaeolyngbya) generally are thinner, more homogeneous, and less frequently layered than walls of eukaryotes (Glenobotrydion). Wall contacts between all observed, contiguous cells appear to be fused. Mucilaginous envelopes occur as extracellular, particulate aggregates that parallel cell contours and appear to bind together colonial cells. Cytoplasm is preserved as intracellular, particulate aggregates of variable size, shape, and cellular position. The distinct intracellular bodies in cells of Glenobotrydion appear as densely granular, solid masses with sharply defined borders; these bodies are interpreted as remnants of cellular organelles, probably pyrenoids. Low opacity, threadlike structures, often appearing to be triple-layered, and to be attached to or to enclose the organelles, are interpreted as remnants of membranes, perhaps derived from chloroplasts. This study demonstrates that considerable ultrastructural detail can be preserved in organic microfossils of Precambrian age and that such detail can be useful for assessing the biological affinities and diagenetic histories of organically preserved microorganisms.

Journal ArticleDOI
TL;DR: Stages of Isospora felis of the cat in the mesenteric lymph node of the mouse 25 days after oral inoculation with oocysts, have been described at the ultrastructural level, with a biological function similar to that of the tissue cyst stage of other genera of isosporan coccidia.
Abstract: Stages of Isospora felis of the cat in the mesenteric lymph node of the mouse 25 days after oral inoculation with oocysts, have been described at the ultrastructural level. The organisms occurred singly within parasitophorous vacuoles in host cell cytoplasm and were sporozoite-like, having a large crystalloid body up to 5.5 mum in length posterior to the nucleus. The size and appearance of the parasitophorous vacuole varied. Some vacuoles contained numerous, small, electron dense granules about 30 nm in diameter. Because of the aggregation of granules and their arrangement within the parasitophorous vacuole, the impression was sometimes gained by light microscopy that parasites were surrounded by a sheath or cyst wall. However, a cyst wall was not present. In host cells, spherical, membrane-bound bodies with a homogeneous, electron dense core and a maximum diameter of 0.25 mum were filed along the limiting membrane of the parasitophorous vacuole. These extra-intestinal parasites were considered to be waiting stages, with a biological function similar to that of the tissue cyst stage of other general of isosporan coccidia.

Journal ArticleDOI
01 Apr 1976-Cancer
TL;DR: Findings support a salivary duct origin, and are evidence against a neurendocrine derivation for this tumor, which was studied by light and electron microscopy.
Abstract: A case of small cell carcinoma of salivary gland was studied by light and electron microscopy Light microscopy showed sheets of small uniform cells with scanty cytoplasm and pyknotic nuclei Electron microscopy showed two distinct cell types: An electron-lucent epithelial-appearing cell, and a denser cell with processes containing bundles of filaments and other features suggesting myoepithelial differentiation Neurosecretory granules were absent These findings support a salivary duct origin, and are evidence against a neurendocrine derivation for this tumor

Journal ArticleDOI
TL;DR: Ultrastructural aspects of interlamellar Henneguya exilis infections in channel catfish are reported and evidence suggests that host cellular cytoplasm as well as interstitial material is taken in by plasmodia.
Abstract: Ultrastructural aspects of interlamellar Henneguya exilis infections in channel catfish are reported. The plasmodium wall of this form differs from that of other species in that it is composed of two outer unit membranes which give rise to a zone of numerous pinocytic canals. Single-membraned canals appeared to be a stable feature of the wall while double-membraned canals are interpreted as those actively carrying out pinocytosis. Evidence suggests that host cellular cytoplasm as well as interstitial material is taken in by plasmodia. Plasmodium wall integrity, aggregation of parasite ectoplasmic components, numbers of pinocytic canals, and number of mitochondria proximal to the wall vary among different plasmodium profiles and may be related to plasmodium maturity. The parasite causes extensive hyperplasia of basal cells, which in turn replaces most other cell types found in noninfected gill filaments. Cytoarchitectural differences between basal cells of noninfected filaments and basal cells adjacent to plasmodia include significantly shorter microfilament bundles in the latter.

Journal ArticleDOI
TL;DR: It is suggested that byssus collagen may be localized in the matrix and in the FBE, which were found mainly in the stem outer laminae.
Abstract: The ultrastructure of the byssus of Mytilus galloprovincialis was analysed by transmission electron microscopy in thin sections of either embedded or frozen samples. All parts of the byssus (stem core laminae, stem outer laminae, threads proximal and distal parts) appear to be formed by the same basic filamentous components organized in different ways at the submicroscopic level and embedded in a variable quantity of matrix. The filaments appear to consist of a central electron-lucent zone (3 nm in diameter), surrounded by an electron-dense rim (total diameter 7 nm). The matrix has a granular or microfilamentous structure. The stem and the threads differ greatly in their submicroscopic organization, but their basic constituents (filaments and matrix) are similar. Peculiar filamentous banded elements (FBE) were found mainly in the stem outer laminae. A relation between the ultrastructure and mechanical properties of the different parts of the byssus was established. The presence of collagen is discussed; since no morphological evidence of any of the known forms of collagen organization was revealed by electron microscopy, it is suggested that byssus collagen may be localized in the matrix and in the FBE.

Journal ArticleDOI
Norio Nakatsuji1
01 Sep 1976
TL;DR: Investigation of the ultrastructure of the migrating cells in anuran gastrulae suggests that the cells migrate along the inner surface of the blastocoel wall by forming filopodia and pseudopodias flattened against the wall.
Abstract: In order to investigate the ultrastructure of the migrating cells in anuran gastrulae, three anurans, which belong to three different genera, were observed with transmission electron microscopy supported by light microscopy of the 1 μm sections and scanning electron microscopy. Fine filopodial cell processes, as well as cell processes probably flattened against the inner surface of the blastocoel wall, were formed by the migrating cells. Blebs and lobopodial cell processes were frequently observed inBufo, sometimes inXenopus, but not observed inRana. Microfilaments were observed in the cell processes. Focal close contacts, probably having adhesive properties, were made between the migrating cells and the inner surface of the blastocoel wall. These observations suggest that the cells migrate along the inner surface of the blastocoel wall by forming filopodia and pseudopodia flattened against the wall. The role of the blebs and lobopodial cell processes requires more investigation.

Journal ArticleDOI
TL;DR: Feeding in Babesia seems to take place by a special organelle composed of tightly coiled double membranes located partly inside and partly outside the parasite, and it is assumed that extracellular digestion of host cytoplasm take place through this organelle.
Abstract: Babesia microti is a highly polymorphic organism. To unravel its fine structure and the function of organelles it was necessary to resort often to serial sections. A single plasma membrane covers the organism. In trophozoites approaching reproduction, segments of double membranes can be found below the plasma membrane. In electron micrographs of poor resolution these segments of double membranes look like pieces of thick membranes and they were often thought to be a thick 2nd membrane. Before the segments of double membranes appear 2 other organelles are formed in older trophozoites: micronemes and rhoptries. There are indications that these structures originate from vesicles of the Golgi apparatus. Large dense bodies of the same structure as the host cytoplasm are not food vacuoles but merely invaginations of host cytoplasm, as found in serial sections and in organisms removed from the host cell. Feeding in Babesia seems to take place by a special organelle composed of tightly coiled double membranes located partly inside and partly outside the parasite. It is assumed that extracellular digestion of host cytoplasm take place through this organelle. The nucleus remains undifferentiated throughout the whole intraerythrocytic stage. It becomes irregular, loboid, but does not divide and remains a single body until the late stage of reproduction when only a small portion, a bud, extends into the forming merozoite.

Journal ArticleDOI
TL;DR: Differences in ultrastructure throughout the apex seemed to be associated with cellular differentiation rather than with the plastochronic functioning of the apex during leaf initiation, and could be correlated with the different rates of cell division in different regions of the meristem.
Abstract: The ultrastructure of the pea shoot apical meristem was examined quantitatively in longitudinal sections. Photographs were taken at eleven defined positions in the apex, at six developmental stages within a single plastochron. The only change in ultrastructure during the period of a single plastochron was the increase in the proportion of plastids with starch in the central regions of the apex and in the young leaf axils. This increase occurred midway in time between the emergence of successive leaves, at precisely the time that the orientation of growth changes in the region where a new leaf is to emerge. There were quantitative changes in ultrastructure associated with cell differentiation. In the sequence of cell development from the summit of the apex (central zone) to the incipient pith, cell enlargement was accompanied by an increase in the volume of endoplasmic reticulum, dictyosomes, microbodies and vacuoles per cell, an increase in the number of mitochondria, microbodies and vacuoles per cell, and an increase in the volume, but not the number, of plastids per cell. In the sequence of axillary development (before the axillary bud begins to grow) the number of mitochondria per cell decreased as cell volume decreased but the number of plastids per cell remained constant. The number of plastids per cell increased only in the developmental sequence leading to leaf development, in which the number of mitochondria and dictyosomes per cell also increased. There appeared to be no features of ultrastructure, qualitative or quantitative, which could be correlated with the different rates of cell division in different regions of the meristem. The differences in ultrastructure throughout the apex were mainly quantitative and seemed to be associated with cellular differentiation rather than with the plastochronic functioning of the apex during leaf initiation.

Journal ArticleDOI
TL;DR: Tomato seedlings were exposed to 3 days of chilling at 5 °C in both the presence and absence of 5 mM ethanolamine, and protection by ethanolamine at the ultrastructural level was most pronounced for the cytoplasm, the mitochondria, and the cell walls.
Abstract: Tomato seedlings were exposed to 3 days of chilling at 5 °C in both the presence and absence of 5 mM ethanolamine. An array of pathological responses could be seen at both the light and electron microscope levels: apparent loss of cell turgor, vacuolization, reduction in the apparent volume of both the cytoplasm and the vacuolar protein bodies, apparent deposition of new material in the cell walls, general disorganization of organelles, especially plastids, and a general loss of cytoplasmic structure. Chilling injury was less pronounced in ethanolamine-treated cotyledonary tissues which appeared to have normal turgor and cell shape at the light microscope level and better preserved organelles at the ultrastructural level. Protection by ethanolamine at the ultrastructural level was most pronounced for the cytoplasm, the mitochondria, and the cell walls. Dead cells were seen with both treatments but were 2–3 times as numerous in the chilled-only tissue.