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  • 1
    ISSN: 0886-1544
    Keywords: brain spectrin ; actin ; immunofluorescence ; peptide mapping ; protein phosphorylation ; syndeins ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Membrane-associated mouse brain spectrin is a 972,000 Mr, 10.5S, (αβ)2 tetramer containing two ∼ 240,000 Mr subunits and two ∼ 235,000 Mr subunits. Two-dimensional [125I]tryptic peptide mapping indicates that these subunits share only limited and equivalent overlap with the α- and β-subunits of red blood cell (RBC) spectrin. Both the 220,000 Mr β-subunit of RBC spectrin and the 235,000 Mr β-subunit of brain spectrin are phosphorylated in the intact mouse. In vitro analysis suggests that both are phosphorylated by a cAMP-independent protein kinase. Antibodies against pure native mouse red blood cell spectrin cross-react with brain spectrin, and antibodies against pure brain spectrin cross-react with both the α-and β-subunits of mouse RBC spectrin. Both antibodies have been utilized to localize brain spectrin within distinct cellular entities of the mouse cerebellum. Granule cell neurons of the internal granule layer and Purkinje cell neurons demonstrated intense fluorscence of the cortical cytoplasm immediately adjacent to the plasma membrane and unstained nuclei, when either RBC or brain spectrin antibodies were utilized for staining. The molecular layer of the cerebellum stained only lightly, and oligodendrocytes and astrocytes appeared to have little fluorescence. Therefore, while brain is a tissue rich in nonerythroid spectrin, the concentration of these immunoreactive analogues is quite variable within distinct cellular entities of the cerebellum.
    Additional Material: 3 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SYNOPSIS Intramitochondrial inclusions of a paracrystalline nature were observed in the peritrichous ciliate Carchesium polypinum This ciliate was found growing in the effluent of a sewage treatment plant. When paracrystalline inclusions were present, there was one per mitochondrion. A variety of profiles was encountered, all presumably of the same structure. Cross-sections revealed packed, spherical masses of 100-150 A diameter with dense walls 30-40 A thick and a variety of core densities. In more longitudinal sections the paracrystalline array appeared as long. electron-dense, finely filamentous elements oriented in parallel arrays and regularly spaced with a diameter of 60-100 A. Mitochondria tended to cluster, and between closely apposed mitochondria a dense, amorphous material was present. Numerous bud-like processes projected from mitochondria. Structural evidence, particularly the arrangement and core densities of these arrays, suggests a filamentous type of viral infection.
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  • 3
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SYNOPSIS. Sessile zooids, and mobile telotrochs and microgamonts of Carchesium polypinum (Protozoa, Ciliata, Peritrichia), were examined by scanning electron microscopy. The results were compared to earlier light and electron microscope studies in order to investigate structural changes concerned with adaptation and differentiation. Telotrochs and microgamonts always had a contracted peristome and usually had a long phalange of cilia. Striae around the contracted buccal apparatus in all 3 stages were convoluted and often had thickened margins; those in telotrochs and microgamonts had oral-aboral ectoplasmic cross-connections. Nonbuccal striae of telotrochs and microgamonts varied in structure and height differences between epiplasmic peaks and alveoli surface membranes. The number of striae were constant in all 3 stages. Pellicular pore structure did not vary in any of the stages examined and resembled parasomal sacs located near buccal structures. Fully relaxed sessile zooids had ectoplasmic ridges coursing from polykinety kinetosomes and cilia to an area in front of the ciliated portion of the haplokinety; these ridges were interpreted to be the interkinetal fibers. Telotroch bands of sessile zooids consisted of 2 or 3 parallel ectoplasmic ridges which circled the aboral region and contained structures resembling pores. Telotroch bands in telotrochs and microgamonts had 2 enlarged, parallel ectoplasmic ridges circling the aboral region; telotroch band cilia were found between these ridges. In addition, a fold-like, ectoplasmic structure extended beyond the 2 ridges and was located between the telotroch band cilia and the aboral ridge. The epiplasmic shelf surrounding the stalk in sessile zooids was enlarged in telotrochs, and cilia were seen in the scopula depression. No scopula organelle was seen in any microgamont.
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  • 4
    ISSN: 1432-0878
    Keywords: Ornithine decarboxylase ; Polyamines ; Mouse ; kidney ; Autoradiography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Ornithine decarboxylase, a key enzyme in polyamine biosynthesis and cell growth, has been localized in mouse kidney by autoradiography after administration of radiolabeled α-difluoromethylornithine. This drug is an enzyme-activated irreversible inhibitor of ornithine decarboxylase and forms a covalent bond with the enzyme. It was found that ornithine decarboxylase is present in all cell types studied but that the highest content occurs in the proximal convoluted tubules followed by the distal convoluted tubules and the collecting tubules. The majority of the enzyme is located in the cytoplasm but about 10–15% is present in the nuclei (often associated with nucleolus-like components) of the cells of the proximal and distal convoluted tubules. The labeled ornithine decarboxylase was lost rapidly from both nucleus and cytoplasm of all the cell types examined, and labeling by radioactive α-difluoromethylornithine was greatly reduced if the mice were pretreated for 5 h with cycloheximide to block protein synthesis. These results indicate that ornithine decarboxylase turns over rapidly in all of the cells.
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  • 5
    ISSN: 1432-0878
    Keywords: Growth ; Enkephalin ; Endogenous opioids ; Immunocytochemistry ; Differentiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The distribution of enkephalin, an endogenous opioid, in tissues and cells of the developing and adult rat was determined by immunocytochemistry with antibodies to met- and leu-enkephalin. Met- and leu-enkephalin were found in all developing cells investigated, with staining generally located throughout the cytoplasm; cell nuclei were not immunoreactive. In comparison to developing cells, immunoreactive analogues to met-enkephalin were usually difficult to detect in the adult. Some notable exceptions were reaction products in leukocytes in blood, lung, and cortex of thymus, fibroblasts in the skin, and seminiferous tubules. These results, in concert with earlier reports that opioid receptors are found largely in developing, but not adult, tissues, indicate that endogenous opioids are specifically involved in biological development, particularly cell proliferation and differentiation. Immunoreactivity in adult nonneural cells may be related to their development in some cases, but also could indicate other functions.
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  • 6
    ISSN: 1432-0878
    Keywords: Spectrin ; Cytoskeleton ; Isoforms ; Heart ; Immunocytochemistry ; Western blotting ; Mouse (C57BL/6)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The distribution of two isoforms of spectrin in the adult mouse heart was investigated by Western blotting and immunocytochemistry by use of monospecific antibodies to erythrocyte spectrin and nonerythroid brain spectrin (240/235). Western blotting revealed proteins analogous to both isoforms of α-spectrin in adult heart. Light-microscopic immunocytochemistry indicated that erythroid spectrin was distributed throughout the myocardium, with immunofluorescence localized to plasma membranes, Z-lines, and intercalated discs. Antibodies to brain spectrin (240/235) exhibited staining throughout the heart, with a generally diffuse distribution except for the prominent immunoreactivity associated with the intercalated discs. Nonerythroid spectrin immunofluorescence was detected in the endothelial cells of the endocardium and the mesothelial cell lining of the epicardium. Erythrocyte spectrin was not detected in the endocardium or the epicardium. The identification and localization of spectrin isoforms in the mammalian heart suggest the importance of spectrin proteins in the structural integrity and proper function of cardiac cells and tissues. This is the first demonstration of two different α-spectrin subunits in the mammalian heart.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    BioEssays 6 (1987), S. 274-279 
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In a companion review1 we discussed the data supporting the conclusion that at least two subtypes of spectrin exist in mammalian brain. One form is found in the cell bodies, dendrites, and post-synaptic terminals of neurons (brain spectrin(240/235E)) and the other subtype is located in the axons and presynaptic terminals (brain spectrin(240/235)). Our recent understanding of brain spectrin subtype localization suggests a possible explanation for a conundrum concerning brain 4.1 localization. Amelin, an immunoreactive analogue of red blood cell (rbc) cytoskeletal protein 4.1, is localized in neuronal cell bodies and dendrites when brain sections are stained with antibody against rbc protein 4.1. However, it has recently been suggested that synapsin I, a neuron-specific phosphoprotein associated with the cytoplasmic surface of small synaptic vesicles, is related to erythrocyte 4.1. In this review we hypothesize that there are at least two forms of brain 4.1: a cell body/dendritic form (amelin) which is detected with rbc protein 4.1 antibody, and a unique form found exclusively in the presynaptic terminal (synapsin I). The binding of synapsin I to brain spectrin(240/235), and its ability to stimulate the spectrin/F-actin interaction in a phosphorylation-dependent manner suggests a model for the regulation of synaptic transmission mediated by the neuronal cytoskeleton.
    Additional Material: 5 Ill.
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