Search results for "Microscopy"
showing 10 items of 3390 documents
Astrocytes give rise to new neurons in the adult mammalian hippocampus
2001
Neurogenesis in the dentate gyrus of the hippocampus persists throughout life in many vertebrates, including humans. The progenitors of these new neurons reside in the subgranular layer (SGL) of the dentate gyrus. Although stem cells that can self-renew and generate new neurons and glia have been cultured from the adult mammalian hippocampus, the in vivo primary precursors for the formation of new neurons have not been identified. Here we show that SGL cells, which express glial fibrillary acidic protein and have the characteristics of astrocytes, divide and generate new neurons under normal conditions or after the chemical removal of actively dividing cells. We also describe a population o…
Development of the filiform hairs on the cerci of Gryllus bimaculatus Deg. (Saltatoria, Gryllidae)
1978
The filiform hairs, mechanoreceptors of Gryllus, pass through six developmental stages during the last larval stage. The cytoplasm of their sense cells suggests intensive synthesis of protein for cellular metabolism and intercytoplasmic exchange of material via glial evaginations. Ultrahistochemical tests demonstrated acid phosphatase in the lysosomes as well as in components of the Golgi apparatus. There was no significant change in the appearance of the sense cell cytoplasm, indicating a maintained functional state also during molting. The new cuticular apparatus is formed after apolysis by the three enveloping cells. Formation of the replacement hairs is initiated by a cytoplasmic outgro…
Unusual basement layer in the midgut of gammaridean Niphargus virei Chevreux (Crustacea, Amphipoda).
1988
The basement membrane of the midgut and posterior caeca epithelium in the gammaridean amphipod Niphargus virei Chevreux, 1896 is made of an unusual structure. This basal lamina, properly called “basal layer”, shows a dense sheet formed by a system of dense hexagonal plates connected by thin filaments. Histochemical studies and enzymatic reactions lead to the conclusion that these structures are proteinaceous, without collagenous protein, and embedded in a neutral polysaccharide matrix. The possible mechanical significance of these mesenteric structures is discussed.
Comparative electronmicroscopic studies on the central cardiac organs of cephalopods (Sepia officinalis)
1969
Die Untersuchungen zur Feinstruktur des Herzens von Sepia officinalis zeigen fur die quer- bzw. schraggestreifte Muskulatur dieses Organs einen hohen Differenzierungsgrad auf. 1. Die Sarkomeren werden mit dem Auftreten zweier Filamenttypen wie die quergestreifte Vertebratenmuskulatur in Z-, A- und I-Bande gegliedert, wobei jedoch die Z-Bande aus einzelnen Teilelementen besteht. 2. Die Herzmuskulatur der Cephalopoden verfugt uber Strukturen, die in Analogie zum Vertebratenherzen als Disci intercalares bezeichnet werden. 3. eben einem langs und quer verlaufenden sarkotubularen System wird die Existenz eines mit dem Ausenraum kommunizierenden T-Systems nachgewiesen. Beide Systeme stehen uber M…
Autophagy, cathepsin L transport, and acidification in cultured rat fibroblasts.
1992
The mechanisms of enzyme delivery to and acidification of early autophagic vacuoles in cultured fibroblasts were elucidated by cryoimmunoelectron microscopic methods. The cation-independent mannose-6-phosphate receptor (MPR) was used as a marker of the pre-lysosomal compartment, and cathepsin L and an acidotropic amine (3-(2,4-dinitroanilino)-3'-amino-N-methyl-dipropylamine (DAMP), a cytochemical probe for low-pH organelles) as markers of both pre-lysosomal and lysosomal compartments. In addition, cationized ferritin was used as an endocytic marker. In ultrastructural double labeling experiments, the bulk of all the antigens was found in vesicles containing tightly packed membrane material…
Effects of caspase inhibitors (z-VAD-fmk, z-VDVAD-fmk) on Nile Red fluorescence pattern in 7-ketocholesterol-treated cells: Investigation by flow cyt…
2007
Background: The 7-ketocholesterol (7KC)-induced cell death has some characteristics of apoptosis and is associated with polar lipid accumulation. So, we investigated the effects of the broad-spectrum caspase inhibitor z-VAD-fmk and of the caspase-2 inhibitor z-VDVAD-fmk on lipid profile evaluated by staining with Nile Red (NR). Methods: The 7KC-treated human monocytic U937 cells were cultured in the absence or in the presence of the caspase inhibitors z-VAD-fmk or z-VDVAD-fmk. When staining with NR is performed, neutral and polar lipids have yellow and orange/red emission, respectively, and fluorescence was then analyzed by flow cytometry (FCM) and by confocal laser scanning microscopy (CLS…
Supravital Uptake of Methylene Blue by Dendritic Cells within Stratified Squamous Epithelia: a Light and Electron Microscope Study
1996
Electron microscopic data on methylene blue staining of dendritic cells in the epithelia of the soft palate and skin of the mouse after supravital dye injection are presented. The ultra-structural details were compared with corresponding light microscopic findings. Methylene blue stained tissue was fixed by immersion in a paraformaldehyde-glutaraldehyde solution containing phosphomolybdic acid. The ensuing dye precipitate was stabilized by ammonium heptamolybdate. The light microscopic investigation revealed that selective staining of dendritic cells depended on the presence of ambient oxygen. In addition, delicate morphological characteristics, like spinous structures of the dendrites, wer…
Differential staining of mucin granules from epoxy resin sections by a phosphotungstic acid-methyl green procedure.
1991
After treatment of epoxy resin semithin sections from glutaraldehyde fixed rat large intestine with 5% aqueous phosphotungstic acid (PTA), staining with unpurified 0.2% solutions of methyl green at 60 C for 5 min produces a color differentiation between mucin granules of goblet cells. Some mucin granules and the glycocalyx appear deep green while the remaining granules, luminal mucin and collagen fibers are pink. The known contamination of unpurified methyl green with crystal violet seems to be responsible for the pink staining reaction of the latter structures, which also present an orange-red fluorescence under green exciting light. Electron microscopic observations show selective contras…
Tracing keratin evolution: catalog, expression patterns and primary structure of shark (Scyliorhinus stellaris) keratins.
1998
We have studied individual keratins of an elasmobranch, the shark Scyliorhinus stellaris (the lesser-spotted dogfish). From various shark tissues, notably skin and stomach, cytoskeletal proteins were isolated and then separated by two-dimensional polyacrylamide gel electrophoresis. Using complementary keratin blot-binding assays and immunoblotting, among these proteins we identified a variety of type I and type II keratins. According to their tissue-specific expression, we distinguished Is and IIs keratins from IE and IIE keratins ("S" and "E" from "simple epithelial" and "epidermal", respectively). Guinea pig antibodies which in immunoblots specifically labeled the entire range of identifi…
At reduced temperature, endocytic membrane traffic is blocked in multivesicular carrier endosomes in rat cardiac myocytes.
1998
Temperatures around 20 degrees C are known to block degradation of endocytosed material by preventing its transport to lysosomes, accordingly reduced temperature has been widely used to define endosomes. Newer studies have revealed that the low temperature block is proximal to perinuclear late endosomes, but it is not clear whether the block is already in early endosomes, or whether the traffic proceeds to multivesicular carrier endosomes which mediate transport from early to late compartments. We have now focused on this problem using rat cardiac myocytes. First, cell fractionation on Percoll gradients showed that at reduced temperatures (22 degrees C and 26 degrees C), with prolonged chas…