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  • 1
    ISSN: 1871-4528
    Keywords: immunocytology ; protein solubility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Two potato (Solanum tuberosum L., cv. Irish Cobbler) Kunitz-type proteinase inhibitors (PKPI) were previously described to be present in the soluble fraction of proteins from tubers in the early stages of development. One of them became insoluble in mature tubers, being extractable from this material in presence of urea. Amino acid sequencing showed that the soluble and insoluble PKPI were identical to each other. Also, immunolocalization using the protein A-gold method showed that both proteins were present inside the vacuole in free (intravacuolar space) and aggregated forms. The density of PKPI in the vacuolar protein aggregates increased from developing to mature tubers. showing that the soluble-insoluble state of this protein is related to the aggregation levels. Purified PKPI precipitated in vitro. mainly in presence of high calcium concentrations and low pH, but this precipitated form was not as stable as aggregates found in vivo. Based on the results obtained, a model of PKPI insolubilization in vivo is discussed.
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  • 2
    ISSN: 1432-0878
    Keywords: Thymus gland ; Epithelium ; Tissue culture ; Cell line ; Immunofluorescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In the monolayer of an established epithelial cell line from the rat thymus, IT-26R21, characteristic cell aggregates quite similar to Hassall's corpuscles were formed. These aggregates were examined by light and electron microscopy, and immunohistochemically. Their interpretation as Hassall's corpuscles is based on the following observations: (1) The aggregates are formed in the monolayer of cells that greatly resemble medullary epithelial cells of the thymus. (2) They consist of flattened epithelial cells in a concentric pattern with one or more degenerating cells in the center. (3) Loss of microvilli suggests that these cells are keratinizing. (4) The aggregates show strongly positive reactions in immunofluorescent staining with antikeratin and antiprekeratin. When Hassall's corpuscles increase in size, cellular proliferation is somewhat suppressed. Both in vivo and in vitro, they may be interpreted as an expression of a changing growth pattern in confined spaces and thus seem to have little immunological function.
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  • 3
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper describes the verification of the accuracy of residual stress measurement by the hole-drilling method. The strain measurement is simulated by the use of the indirect fictitious-boundary integral method. As an example, a finite rectangular plate subjected to initial stress is treated, and a simulated measurement of the residual stress is made using the strain relieved during hole drilling. The accuracy of residual stress measurement is estimated by comparing the simulated measured residual stress with the actual residual stress, i.e., the given initial stress. The results are shown for various distances and angles of strain gages. Also, the influences of the eccentricity of the hole from the center of the strain gages and the effect of a boundary near the hole are examined.
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  • 4
    ISSN: 1615-6102
    Keywords: Boergesenia forbesii ; Cellulose microfibrils ; Cell wall ; Fluorescent brightening agent ; Freeze fracture ; Terminal synthesizing complex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Wounding cells ofBoergesenia forbesii (Harvey) Feldmann induces the synchronous formation of numerous protoplasts which synthesize large cellulose microfibrils within 2–3 hours after wounding. The microfibrils appear to be assembled by linear terminal synthesizing complexes (TCs). TC subunits appear on both E- and P-faces of the plasma membrane, thus suggesting the occurrence of a transmembrane complex. The direction of microfibril synthesis is random during primary wall assembly and becomes ordered during secondary wall assembly. The average density of TCs during secondary wall deposition is 1.7/μm2, and the average length of the TC is 510 nm. TC organization is similar to that ofValonia macrophysa; however, the larger TCs ofBoergesenia (510 nm vs. 350 nm) produce correspondingly larger microfibrils (30 nm vs. 20 nm). The effects of a fluorescent brightening agent (FBA), Tinopal LPW, on cell wall regeneration ofBoergesenia protoplasts was investigated. The threshold level of Tinopal LPW for interfering with microfibril assembly is 1.5 μM. At 95 μM Tinopal (for short periods up to 15 minutes), microfibril impressions have atypical spherical impressions at their termini. At longer incubations (24 hours), TCs and microfibril impressions are absent. When washed free of Tinopal, the protoplasts eventually resume normal wall assembly; however, TCs do not reappear until at least 30 minutes after the removal of Tinopal. In consideration of the presence of ordered TCs before FBA treatment, their random distribution upon recovery implies an intermediate stage of assembly or possiblyde novo synthesis.
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  • 5
    ISSN: 1615-6102
    Keywords: Boergesenia forbesii ; Microfibrils ; Microtubules ; Plasma membrane ; Sectioned material ; Terminal complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Transmembrane linear terminal complexes considered to be involved in the synthesis of cellulose microfibrils have been described in the plasma membrane ofBoergesenia forbesii. Evidence for the existence of these structures has been obtained almost exlusively using the freeze etching technique. In the present study an attempt has been made to complete these studies using conventional fixation, staining, and sectioning procedures. In developing cells ofBoergesenia forbesii, strongly stained structures traversing the plasma membrane and averaging 598.9 nm ± 171.3 nm in length, 28.7 nm ± 4.2 nm in width, and 35.2 nm ± 6.6 nm in depth have been demonstrated. These structures are considered to be linear terminal complexes. At their distal (cell wall) surface, they appear to be closely associated with cellulose microfibrils. At the proximal (cytoplasmic) surface, they are associated with microtubules and polysomes. A model of the possible interrelation of the terminal complexes and microtubules leading to the generation of cell wall microfibrils is proposed.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 144 (1988), S. 160-169 
    ISSN: 1615-6102
    Keywords: Boergesenia forbesii ; Valonia ventricosa ; Freeze fracturing ; Cellulose synthesizing complexes ; Microfibrils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The development of linear cellulose synthesizing complexes (=TCs) of two selected siphonocladalean algae,Boergesenia forbesii andValonia ventricosa was investigated by following the time course of the regeneration of cell walls with the freeze fracture technique after aplanospore induction. The following structural changes of TC development were examined: (1) TCs initiatede novo; (2) the first nucleation of TC subunits occurs within 2 hr inBoergesenia and 5 hr inValonia after aplanospore induction, immediately followed by the assembly of cellulose microfibrils; (3) TCs increase their length during the assembly of randomly oriented microfibrils; and, (4) TCs stop increasing in length after the assembly of ordered microfibrils begins, with some time lag. The data demonstrate that linear TCs are not artificial products but dynamic entities which are involved in the assembly of cellulose microfibrils.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 180 (1994), S. 39-48 
    ISSN: 1615-6102
    Keywords: Oocystis apiculata ; Rapid freezing ; Deep etching ; Crossbridges ; Cell wall ; Cellulose microfibrils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The cell wall of a green alga,Oocystis apiculata, was visualized by electron microscopy after preparation of samples by rapid-freezing and deep-etching techniques. The extracellular spaces clearly showed a random network of dense fibrils of approximately 6.4 nm in diameter. The cell wall was composed of three distinct layers: an outer layer with a smooth appearance and many protuberances on its outermost surface; a middle layer with criss-crossed cellulose microfibrils of approximately 15–17 nm in diameter; and an inner layer with many pores between anastomosing fibers of 8–10 nm in diameter. Both the outer and the inner layer seemed to be composed of amorphous material. Cross-bridges of approximately 4.2 nm in diameter were visualized between adjacent microfibrils by the same techniques. The cross-bridges were easily distinguished from cellulose microfibrils by differences in their dimensions.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 204 (1998), S. 94-102 
    ISSN: 1615-6102
    Keywords: Ascidian ; Cellulose microfibril ; Hemocoel ; Polyandrocarpa misakiensis ; Tunic cord
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A specialized structure of tunic cord inPolyandrocarpa misakiensis is investigated by electron microscopy. The tunic cord is a cord-like coiled structure of 5–30 μm in diameter and 0.1–9.0 mm in length. The tunic cords originate and elongate from the dorsal tunic, and their termini have a swollen and ornamented structure. Scanning and transmission electron micrographs and the electron diffractogram show that the tunic cords are composed of bundled microfibrils of cellulose I with high crystallinity. The tunic cord is completely surrounded by single-layered epidermal cells, which have been found as the site of cellulose biosynthesis. A number of tunic cords are connected to the internal tunic of the siphon by forming “eyelet” structures at their termini. These observations suggest that the tunic cords act as a connector between dorsal and internal tunic of the siphon.
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  • 9
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The nomenclature proposed by Otaka et al. (1968) for the 30S ribosomal protein components of Escherichia coli as separated by carboxymethyl(CM)-cellulose column chromatography was adopted in several papers in which the genetic loci for many 30S ribosomal proteins on the E. coli chromosome were determined. In order to compare these data with those obtained in other laboratories, the 30S ribosomal proteins fractionated by CM-cellulose chromatography were correlated with the standard nomenclature proposed by Wittmann et al. (1971).
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  • 10
    ISSN: 1615-6102
    Keywords: Cellulose microfibril ; Freeze-fracture ; Terminal complex ; Tunic ; Tunicate ; Ascidian
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cellulose synthesizing enzyme complexes (terminal complexes, TCs) have been found in the plasma membrane of epidermal cells in the tunicateMetandrocarpa uedai by using freeze-fracture replication techniques for electron microscopy. Assembly of cellulose microfibrils by TCs is a universal phenomenon in the biological kingdoms. The TCs are locally distributed in the plasma membrane of the epidermal cells facing the tunic, and no TCs are observed on the lateral membranes bordered by tight junctions. The TCs consist of two types of membrane subunits: large particles (14.5 nm in diameter) on the periphery and small subunit particles (7.2 nm) filling the center; the latter are hypothesized to be involved in cellulose synthesis. The TCs are the linear type (ca. 195 nm in length and 78 nm in width). Direct connections of TCs with the termini of microfibrils were observed. Amorphous regions, which were hypothesized the nascent microfibrils, were associated with the depressions of the TCs. The distortion of microfibrils on their terminus indicates that the crystallization may occur at the margin of TCs from which the microfibrils are discharged. This report provides evidence that: (1) The outer cell membrane of epidermis is the site for the assembly of cellulose microfibrils in the tunic; (2) a new type of TC is involved in the biosynthesis of cellulose microfibrils in the tunicates; (3) disorganized glucan chains may be synthesized in the depression of TCs and crystallized outside the E-surface of the epidermal cell membrane.
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