Search results for "Ultrastructure"
showing 10 items of 224 documents
A Comparative Ultrastructural Investigation of Some Nannochloris Species (Chlorococcales) with Particular Reference to the Systematic Position of Nan…
1989
Nanochlorum eucaryotum was described by Wilhelm et al. (1982) as a new algal species with an uncertain taxonomic position. Whereas some features were chlorococcacean, others suggested an isolated position in the sense of a “pre-eucaryote” (Wilhelm, 1983; Zahn, 1984; Geisert et al., 1987). Our comparative ultrastructural, physiological and biochemical examinations of coccoid microalgae (Menzel, 1988) gave no arguments for the separation of Nanochlorum eucaryotum from the genus Nannochloris. This paper is concerned with the ultrastructural composition of the cell wall and mode of reproduction in Nanochlorum eucaryotum as well as in three Nannochloris species. The systematic position of Nanoch…
Ultrastructural patterns of human dentinal tubules, odontoblasts processes and nerve fibres.
2005
The structure of the dentin, consists of the following elements: the odontoblastic processes, dentinal tubules and their periodontoblastic spaces. The odontoblasts are aligned in a single layer in the periphery of the dental pulp and secrete the organic components of dentin. The vitality of dentin is mediated too by the nerve fibres. The ultrastructure of the trigeminal sensory nerves in dentin, especially in relation to odontoblasts remains to be clarified. We studied the third molars and young premolars. The specimens were fixed in glutaraldehyde immediately after extraction. Our investigations give evidence to prove that the distribution of the dentinary tubules is homogeneous, containin…
Zinc-positive presynaptic boutons of the rabbit hippocampus during early postnatal development
1998
Abstract The evolution of vesicular zinc-containing boutons in the developing rabbit hippocampus has been studied during early postnatal life using the selenite–Danscher histochemical method. By P3, large immature mossy fiber boutons with labeled synaptic vesicles were seen in the hilus of the dentate gyrus and in the stratum lucidum of the CA3–CA4 hippocampal areas. After P5, smaller boutons with labeled vesicles were identified in the stratum oriens and stratum radiatum of all hippocampal areas, and even transiently in the stratum lacunosum of P6 animals. Vesicular zinc-containing boutons increased in number and underwent ultrastructural maturation; light microscope densitometric–volumetr…
Ultrastructure of a muscle spindle-analogous receptor organ in the mandible of Oncopeltus fasciatus (Insecta, Heteroptera) with remarks on the homolo…
1985
A non-ciliary muscle receptor organ in the first mandibular retractor muscle of Oncopeltus fasciatus is described. The organ consists of two specialized muscle fibres of the first retractor, which are embedded in a thickened layer of connective tissue. The sensory innervation is supplied by three multiterminal sense cells sending several dendrites to the receptor muscle fibres. ‘Naked’ dendritic terminals are attached to the muscle surface or connective tissue fibrils. The far-reaching analogy of the receptor to the intrafusal chain-fibres of vertebrate muscle spindles is remarkable. The existence of a muscle receptor organ in the first mandibular retractor may serve as an argument in favor…
Feinstruktur der Cheliceren-Dr�se von Nemastoma dentigerum Canestrini (Opiliones, Nemastomatidae)
1973
1. Nemastoma dentigerum Canestrini besitzt als sekundares mannliches Geschlechtsmerkmal eine Apophyse auf dem ersten Chelicerenglied, die eine Druse enthalt. 2. Die einzelnen Drusenzellen schliesen sich jeweils zu Dreiergruppen zusammen, deren distales Ende immer von 3 Hullzellen umfast wird. Diese 6 Zellen bilden eine funktionelle Einheit innerhalb des komplexen Drusenorgans. Jede Drusenzelle gliedert sich in 3 Abschnitte: 1. in den basalen kernhaltigen Teil, 2. in den mittleren sehr langen Drusenzellschlauch und 3. in den distalen Kopf mit Mikrovilli-Becher. 3. An der Sekretion beteiligen sich 2 Zelltypen: die 3 Drusenzellen und die innere Hullzelle (H1). Das Sekret beider Zelltypen gelan…
Ultrastructure, development, and moulting of the aesthetascs of Neomysis integer and Idotea baltica (Crustacea, Malacostraca)
1983
The development of the aesthetascs of Neomysis integer (Malacostraca, Mysidacea) and Idotea baltica (Malacostraca, Isopoda) were investigated by electron microscope methods. Basically the aesthetascs of both species develop according to the same pattern. The newly formed sensillar shafts lie invaginated within the epidermal tissue. They are formed by numerous enveloping cells, which are arranged telescopically one by one. Each enveloping cell secretes a definite portion of the new shaft cuticle. The innermost enveloping cell extends furthest distally and deposits the cuticle of the future shaft tip. The outer enveloping cells produce the cuticle of the more proximal shaft portions. Whereas …
Practical application of electron microscopy to neuromuscular diseases.
2013
Concerning individual neuromuscular conditions, electron microscopy may be considered “essential,” “helpful,” or “wasteful.” “Essential” electron microscopy should provide a clear diagnosis, because of the disease specificity of the ultrastructural findings, in particular as to inclusions within muscle fibers, such as cylindrical spirals and reducing bodies. Electron microscopy may be “helpful” in detecting ultrastructural features preceding typical light microscopic findings, for instance, undulating tubules in endothelial cells. Congenital, metabolic, and inflammatory myopathies may often be more easily and more reliably diagnosed by means of the electron microscope. Diagnostically “waste…
Morphological aspects of the neuronal ceroid lipofuscinoses
2000
Morphological aspects of the neuronal ceroid lipofuscinoses (NCL) encompass two main features: loss of nerve cells and accumulation of autofluorescent lipopigments within cellular compartments. The former requires histology and morphometry for assessment, while the latter necessitates fluorescence microscopy, electron microscopy, and immunohistochemistry. Accumulation of lipopigments is widespread throughout the central nervous system and extracerebrally. The latter feature enables diagnosis of NCL and its clinical subtype. Loss of neurons is most pronounced in cerebral and cerebellar cortices, in early childhood forms. In subcortical grey matter and in later-onset forms, juvenile and adult…
Supravital Uptake of Cationic Dyes by Mast Cell Granules: A Light and Electron Microscope Study
1994
Methylene blue and neutral red were selected for staining mast cell granules by supravital injections. A new technique was applied for embedding in paraffin and Araldite without dislocation or loss of dye. Stabilization and electron microscopic identification of the dyes were achieved by transforming them into electron-dense precipitates using phosphomolybdic acid dissolved in a paraformaldehyde-glutaraldehyde mixture to preserve the ultrastructure of the tissues. It was found that in general the intensity of the light microscopic staining correlated directly with the electron density. Closer study revealed that not all cytoplasmic granules exhibited the same strong affinity for the cationi…
Electronmicroscopical Contrast by Palladium Chloride
1986
Thin sections of glutaraldehyde-fixed, epoxy resin-embedded bone marrow from rats were treated with 2% palladium chloride in 2% concentrated HCl. This procedure was found to induce high electron density in chromatin from all cell types and in cytoplasmic granules of neutrophils and eosinophils. In the latter, the crystalline body showed more contrast than the matrix.