bluuebunny/crossref_metadata_2025_split huggingface dataset:
Traffic through the golgi apparatus as studied by radioautography
Authors: Bennett G. , Wild G. 
Published: February 2005

AbstractThe ability to radiolabel biological molecules, in conjunction with radioautographic or cell fractionation techniques, has brought about a revolution in our knowledge of dynamic cellular processes. This has been particularly true since the 1940's, when isotopes such as 35S and 14C became available, since these isotopes could be incorporated into a great variety of biologically important compounds. The first dynamic evidence for Golgi apparatus involvement in biosynthesis came from light microscope radioautographic studies by Jennings and Florey in the 1950's, in which label was localized to the supranuclear Golgi region of goblet cells soon after injection of 35S‐sulfate. When the low energy isotope tritium became available, and when radioautography could be extended to the electron microscope level, a great improvement in spatial resolution was achieved. Studies using 3H‐amino acids revealed that proteins were synthesized in the rough endoplasmic reticulum, migrated to the Golgi apparatus, and thence to secretion granules, lysosomes, or the plasma membrane. The work of Neutra and Leblond in the 1960's using 3H‐glucose provided dramatic evidence that the Golgi apparatus was involved in glycosylation. Work with 3H‐mannose (a core sugar in N‐linked side chains), showed that this sugar was incorporated into glycoproteins in the rough endoplasmic reticulum, providing the first radioautographic evidence that glycosylation of proteins did not occur solely in the Golgi apparatus. Studies with the tritiated precursors of fucose, galactose, and sialic acid, on the other hand, showed that these terminal sugars are mainly added in the Golgi apparatus. With its limited spatial resolution, radioautography cannot discriminate between label in adjacent Golgi saccules. Nonetheless, in some cell types, radioautographic evidence (along with cytochemical and cell fractionation data) has indicated that the Golgi is subcompartmentalized in terms of glycosylation, with galactose and sialic acid being added to glycoproteins only within the trans‐Golgi compartment. In the last ten years, radioautographic tracing of radioiodinated plasma membrane molecules has indicated a substantial recycling of such molecules to the Golgi apparatus.
Scale formation in algae
Authors: Melkonian Michael , Becker Burkhard , Becker Dieter 
Published: February 2005

AbstractScale biogenesis in algae represents a unique model system to study the transport of secretory macromolecules through the Golgi apparatus (GA) and their exocytosis. The larger scales can be visualized in the light microscope, and thus the kinetics of scale assembly, transport, and secretion can be studied in vivo. In addition, scales are osmiophilic and readily visible in conventional transmission electron microscopy; thus, details of scale assembly and sorting can be studied without invoking immunolabeling techniques. The following are distinctive features of scale biogenesis in algae: (1) transport of scales through the GA‐stack occurs by cisternal progression; (2) scale secretion may be very rapid (in some cases a single GA‐cisterna leaves the stack every 15–20 s); (3) sorting of different scale types does not occur in the GA, but in a post‐GA‐compartment. Recent progress in the analysis of scale formation in the green flagellates Tetraselmis and Scherffelia is reviewed.
Role of the golgi apparatus in cellular pathology
Authors: Morré Dorothy M. 
Published: February 2005

AbstractThe Golgi apparatus response to pathological disorders is predominantly as an intermediary component of membrane biogenesis where it is involved in processing, sorting and secretion of materials via secretory granules, and in the formation of lysosomes. A common initial response of the Golgi apparatus to any stress is an alteration or cessation of secretory activity. In the transformed cell, the Golgi apparatus is altered both morphologically and biochemically, suggesting a shift from a secretory to a membrane‐generating mode of functioning. However, since fewer or less well‐developed Golgi apparatus are frequently found in transformed cells, analytical methods of membrane isolation developed for normal tissues may not always yield equivalent results when applied to tumors. Cell surface alterations characteristic of malignant cells may result from modifications occurring at the level of the Golgi apparatus. Some lysosomal dysfunctions may result from underglycosylation of acid hydrolases by the Golgi apparatus. The use of cell‐free systems between endoplasmic reticulum and Golgi apparatus or within Golgi apparatus cisterane is providing a new approach to the elucidation of the role of the Golgi apparatus in normal as well as pathological states.
Polarity of the surface and cortex of the amphibian egg from fertilization to first cleavage
Authors: Stewart‐Savage J. , Grey Robert D. , Elinson Richard P. 
Published: February 2005

AbstractThe anuran egg is polarized along its animal–vegetal axis and becomes bilaterally symmetrical before first cleavage. Functional sperm entry is regionally restricted to the animal hemisphere of the egg, and functional sperm entry does not occur after egg activation. This regional and functional restriction in sperm entry correlates with the presence of long, slender microvilli and with the presence of the filamentous component of the glycocalyx. After sperm fusion, the egg undergoes activation, including a depolarization of the membrane potential and exocytosis of granules in the cortex. Both of these activation responses are the result of a propagated increase in intracellular calcium. The egg's ability to undergo a propagated activation response develops after germinal vesicle breakdown and depends on the development of the cortical endoplasmic reticulum. Once activated, the radial symmetric egg acquires bilateral symmetry due to a rotation of the egg cortex relative to the inner cytoplasm. A transient array of parallel microtubules forms near the vegetal cortex and may be part of the motor driving the cortical rotation.
Ultrastructural immunocytochemistry of the adenohypophysis in the rat: A review
Authors: Kurosumi Kazumasa 
Published: February 2005

AbstractImmunocytochemistry has made great strides in the morphology of endocrine glands, especially the adenohypophysis, because the localization of hormones can be clearly demonstrated by this method in the microscopic preparations both for light and electron microscopy. In the adenohypophysis, electron microscopic immunocytochemistry is useful for identifying the producer cell of each hormone. The second contribution is its application to the cell biology of secretion mechanisms. The pituitary hormones, their precursors, derivatives, and fragments were artificially synthesized and their antibodies were produced. Using these antibodies the intracellular sites of synthesis, condensation, processing, and sorting were studied under the electron microscope. The ultrastructure of each cell organelle and its alteration due to the changing function was studied. It was proved that the intracisternal granules in the thyroidectomy cells contain thyroid‐stimulating hormone (TSH). The trans‐Golgi network or GERL contains a peculiar supporting structure, intracisternal skeleton. Transport of secretory granules may be performed in relation to the microtubules, actin, and some related substances. The most frequently observed mode of hormone release in the adenohypophysis is exocytosis. Sometimes multigranular exocytosis occurs. Vesiculation of membrane around the secretory granules often occur inward or outward. The inward vesiculation forms pinocytotic vesicles, through which the membrane material may be retrieved. The outward vesiculation forms vesicle‐like fragments of cytoplasm being discarded to the extracellular space. By these mechanisms the surface area of the cell is maintained constantly.
Ultrastructure of spontaneous and transplanted pituitary tumors in laboratory animals
Authors: Lloyd Ricardo V. 
Published: February 2005

AbstractThe present review examines ultrastructural studies of pituitary tumors in laboratory animals. Such studies have been facilitated by the development of newer techniques such as immunocytochemistry and in situ hybridization. Using these methods it has been possible to correlate morphological features with function by characterizing specific pituitary hormones in secretory granules and analyzing the messenger ribonucleic acids produced by specific cell types. Analyses of spontaneous and experimentally induced tumors have provided a great deal of insight into the function and ultrastructure of these neoplasms. The description of tumor cells producing more than one hormone has been facilitated by immunocytochemical analyses. Studies of transgenic models of pituitary hyperplasia and tumor development are expanding our knowledge about the ultrastructure and about other aspects of pituitary tumors in a more controlled experimental setting. The production of various hormones by the same pituitary tumors and even the same tumor cells indicates that complex regulatory mechanisms must be analyzed by a combination of ultrastructural and other techniques to learn more about growth and hormone secretion in pituitary neoplasms.
Design and operation of a simple environmental chamber for rapid freezing fixation
Authors: Bailey S. M. , Chiruvolu S. , Longo M. L. , Zasadzinski J. A. N. 
Published: February 2005

AbstractRapid freezing is the most important step in sample preparation for freeze‐fracture and other cryotechniques for electron microscopy. We present the design and operation of a simple environmental chamber coupled to a plunger‐driven freezing device that has provided simple and reliable freezing from temperatures and humidities other than ambient. The chamber can be constructed and operated with equipment and techniques common to most electron microscopy labs. Temperature control of ±0.1°C and relative humidities of >90% were provided over the range −5–60°C. Typical electron micrographs showing well preserved structures comparable to jet‐freezing are presented.
Scanning electron microscopy of piliated Neisseria gonorrhoeae processed with hexamethyldisilazane
Authors: Dekker Nusi P. , Lammel Claudia J. , Brooks Geo. F. 
Published: February 2005

AbstractPiliated Neisseria gonorrhoeae are virulent and attach readily to some human mucosal cells. The study of interactions between piliated Neisseria gonorrhoeae and surface structures of eukaryotic cells in tissue culture requires consistent high resolution imaging in scanning electron microscopy (SEM). The combination of the fixatives glutaraldehyde, osmium, tannic acid, and uranyl acetate improves preservation of pili and other delicate structures. Following the critical point drying (CPD) process, pili bundles remained intact, but charging produced image distortion in most of the specimens. The use of hexamethyldisilazane (HMDS) with air drying substantially reduced charging and image distortion. Less contrast and greater resolution of pili bundles and surface structures of bacteria or tissue culture cells were obtained at magnifications of 10,000 or higher. As an alternative to CPD, HMDS processing of cell culture monolayers was simple and was more efficient when a large number of samples was processed.
Effects of vitamin A deficiency on the inter—Sertoli cell tight junctions and on the germ cell population
Authors: Ismail Nermine , Morales Carlos R. 
Published: February 2005

AbstractWhen 20‐day‐old rats are placed on a vitamin A deficient diet (VAD) for a period of 10 weeks, the seminiferous tubules are found to contain only Sertoli cells, a few residual A0, A1 spermatogonia, and preleptotene spermatocytes (PL). The type A1 spermatogonia and PL spermatocytes are arrested in their G2 phase. In VAD rats type A2‐A4, intermediate (In) and B spermatogonia and all types of spermatocytes (except PL spermatocytes) and spermatids are eliminated from the seminiferous tubules. Two questions were raised in this investigation: (1) Is there, in VAD rats, any correlation between a breakdown of the blood‐testis barrier (e.g., Sertoli cell tight junctions) and germ cell loss? (2) Is the disappearance of most germinal cells due to their degeneration during spermatogenesis or to a maturation depletion process resulting from an arrest of spermatogenesis at the spermatogonial stage? To investigate these questions four groups of male Sprague‐Dawley rats (20‐days old) were fed a VAD diet for 7 to 12 weeks. The testes were fixed by perfusion with 2.5% glutaraldehyde in 0.1 M sodium cacodylate containing 2% lanthanum nitrate, an electron opaque tracer used to test the patency of Sertoli cell tight junctions. The lanthanum permeated the intercellular space of the basal compartment but was arrested by normal inter—Sertoli cell tight junctions. The seminiferous epithelium showed numerous degenerating germ cells, some being internalized by Sertoli cells as membrane‐bound phagosomes. Thus, these results indicate firstly that inter—Sertoli cell tight junctions remain intact during vitamin A deficiency, and secondly that in a first phase nonviable germinal cells degenerate during spermatogenesis and their residues are actively phagocytosed by Sertoli cells followed by a second phase where the regressed state of the seminiferous epithelium is maintained by a maturation depletion condition resulting from an arrest of spermatogonial proliferation and differentation.
Intermediate filaments in sertoli cells
Authors: Aumüller G. , Schulze C. , Viebahn C. 
Published: February 2005

AbstractUsing immunohistochemical techniques both at light and electron microscopic levels, the arrangement and distribution of intermediate filaments in Sertoli cells of normal testis (in rat and human), during pre‐ and postnatal development (in rabbit, rat, and mouse) and under experimental and pathological conditions (human, rat), have been studied and related to the pertinent literature. Intermediate filaments are centered around the nucleus, where they apparently terminate in the nuclear envelope providing a perinuclear stable core area. From this area they radiate to the plasma membranes; apically often a close association with microtubules is seen. Basally, direct contacts of the filaments with focal adhesions occur, while the relationship to the different junctions of Sertoli cells is only incompletely elucidated. In the rat (not in human) a group of filaments is closely associated with the ectoplasmic specializations surrounding the head of elongating spermatids. Both in rat and human, changes in cell shape during the spermatogenic cycle are associated with a redistribution of intermediate filaments. As inferred from in vitro studies reported in the literature, these changes are at least partly hormone‐dependent (vimentin phosphorylation subsequent to FSH stimulation) and influenced by local factors (basal lamina, germ cells). Intermediate filaments, therefore, are suggested to be involved in the hormone‐dependent mechanical integration of exogenous and endogenous cell shaping forces. They permit a cycledependent compartmentation of the Sertoli cell into a perinuclear stable zone and a peripheral trafficking zone with fluctuating shape. The latter is important with respect to the germ cell‐supporting surface of the cell which seems to limit the spermatogenetic potential of the male gonad.
Ultrastructure of the neurohypophysis
Authors: Scheithauer B. W. , Horvath E. , Kovacs K. 
Published: February 2005

AbstractThis review summarizes our current knowledge of the ultrastructure of the human neurohypophysis and includes comments on its anatomy, physiology, and embryology. The neurohypophysis represents a unique tissue having neural and endocrine characteristics and possessing ultrastructural features distinct from those of conventional endocrine organs such as the anterior pituitary, thyroid, pancreatic islets, etc. In contrast to these glands, the neurohypophysis is composed of the processes of mature neurons. As such, it is not capable of synthesizing hormones but only of their storage and release. Neurosecretion is one of the most exciting areas of neuroendocrinology and, although spectacular progress has been achieved in elucidating the process, a number of aspects are incompletely understood. Recent evidence indicates that the magnocellular nuclei of the hypothalemus, the anatomic origin and functional basis of the neurohypophysis, produce not only vasopressin and oxytocin, the so‐called “neurohypophyseal hormones,” but a number of other biologically active peptides as well. The physiologic function of these substances is largely unknown but they may be of profound importance in endocrine homeostasis. Based on these novel findings, the role of the neurohypophysis in endocrine regulation has to be re‐evaluated.
Species‐specific localization of actin in mammalian spermatozoa: Factor artifact?
Authors: Fouquet Jean‐Pierre , Kann Marie‐Louise 
Published: February 2005

AbstractActin has been characterized and localized in sperm cells of many mammals. Nevertheless, the reported localizations obtained by different methods and/or antibodies varied from species to species and even for the same species. To clarify the question, sperm actin distribution was reinvestigated under uniform technical conditions. Immunogold post‐embedding procedures were performed using a polyclonal and two monoclonal antibodies of known specificity to localize actin in spermatids and spermatozoa of rabbit, mouse, rat, monkey, and human. In these species, actin (F‐actin) was detected with the three antibodies between the nucleus and the acrosome of round and elongating spermatids. Species‐specific changes occurred in maturing spermatids. In the rabbit, actin labeling decreased and disappeared from the tip to the base of the subacrosomal layer. In testicular and epididymal spermatozoa actin was detected only with a monoclonal antibody (Amersham) successively in the neck, postacrosomal area, and subacrosomal bulges. In mouse late spermatids a transitory labeling of the neck was detected only with the polyclonal antiactin. In testicular and epididymal spermatozoa an actin labeling was observed in the principal piece of the tail. In rat, monkey, and human sperm cells actin remained undetected. These results suggest that there is a redistribution of actin in late spermatids and spermatozoa which is a species‐specific process but not an artifact of methodological origin. Thus, a function for actin in sperm, if any, remains to be demonstrated.
Degradation, amorphization, and recrystallization of ion bombarded si(111) surfaces studied by in situ reflection electron microscopy and reflection high energy electron diffraction techniques
Authors: Claverie A. , Beauvillain J. , Fauré J. , Vieu C. , Jouffrey B. 
Published: February 2005

AbstractIn this paper we report the effect of noble gas ions bombardment on the degradation of atomically flat Si(111) surfaces at room and high (400°C—600°C) temperatures. Reflection high energy electron diffraction (RHEED) and reflection electron microscopy (REM) have been used to characterize the topography and structure of the as‐implanted and post annealed surface layers. It is shown that the fading of the specularly reflected beam is not directly related to the amorphization of the surface. This experimental study has also evidenced the difficulties one meets to regrow a defect‐free material after amorphization by noble gas bombardment. For high temperature for which the amorphization is not possible, the surface loses its stepped structure and turns into a monocrystalline but atomically rough surface. This roughness is a function of substrate temperature.
Ab‐initio primitive cell parameters from single convergent‐beam electron diffraction patterns: A converse route to the identification of microcrystals with electrons
Authors: Page Y. Le 
Published: February 2005

AbstractA new method for the ab initio derivation of Buerger‐reduced primitive cell parameters from coordinate measurements of spots on single convergent‐beam electron diffraction (CBED) patterns is described, which does not involve trial‐and‐error. The pattern can be taken along any zone axis, and misorientations of the crystallite by as much as a few degrees are taken into account without loss of accuracy. This derivation of cell parameters by least‐squares analysis of the measurements has been automated in a program called NRCBED. Present accuracy is about 1% on lengths and 2° on angles, but could be significantly improved by modelling projector lens aberrations, or by using a microscope without a projector lens. With present technology, it is possible to obtain a CBED pattern and a semi‐quantitative energy‐dispersive X‐ray (EDX) analysis simultaneously from a single microcrystal a few hundred Ångströms across. It becomes therefore possible to identify the material of the crystal on a single CBED pattern: a cell parameter database for known compounds is searched with the primitive cell parameters obtained in the above way, and with a mask describing the EDX results qualitatively. Feasibility is demonstrated on a crystallite of CeO2 500 Ångströms across. With this new approach, trial‐and‐error should disappear from the solution of other long‐standing problems: interpretation of X‐ray powder patterns for new compounds in the presence of impurity lines, or in the case of multiple phases should become straightforward.
Fine structure of the pinealopetal innervation of the mammalian pineal gland
Authors: Møller Morten 
Published: February 2005

AbstractThe mammalian pineal gland is innervated by peripheral sympathetic and parasympathetic nerve fibers as well as by nerve fibers originating in the central nervous system (central innervation). The perikarya of the sympathetic fibers are located in the superior cervical ganglia, while the fibers terminate in boutons containing small granular vesicles and a few large granular vesicles. Both noradrenaline and neuropeptide Y are contained in these neurons. The parasympathetic fibers originate from perikarya in the pterygopalatine ganglia. The neuropeptides, vasoactive intestinal peptide and peptide histidine isoleucine, are present in these fibers, the boutons of which contain small clear transmitter vesicles and larger granular vesicles. The fibers of the central innervation originate predominantly from perikarya located in hypothalamic and limbic forebrain structures as well as from perikarya in the optic system. These fibers terminate in boutons containing small clear and, in certain fibers, an abundant number of large granular vesicles. In rodents, the majority of the central fibers terminate in the deep pineal gland and the pineal stalk. From these areas impulses might be transmitted further caudally to the superficial pineal gland via neuronal structures or processes from pinealocytes. Several hypothalamic neuropeptides and monoamines might be contained in the central fibers.The intrapineal nerve fibers are located both in the perivascular spaces and intraparenchymally. The majority of the intraparenchymally located fibers terminate freely between the pinealocytes. However, some nerve terminals make synaptic contacts with the pinealocytes and in some species with intrapineal neurons.In fetal mammals, sympathetic, parasympathetic, and central fibers are also present. In addition, an unpaired nerve, connecting the caudal part of the pineal gland with the extreme rostral part of the mesencephalon, is present. This nerve is a homologue to the pineal nerve (nervus pinealis) observed in lower vertebrates. © 1992 Wiley‐Liss, Inc.