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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 191 (1961), S. 1318-1319 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] These characterizations have been made from fixed specimens at high-magnification light microscopy after certain staining procedures. In some cases it has been possible to confirm the findings by dark-field microscopy on living flagella2. Manton3 and Pitelka et al.* have been able to confirm ...
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994), S. 135-142 
    ISSN: 0886-1544
    Keywords: bidirectional swimming ; flagellar movement ; helical bends ; 9+0 axoneme ; planar bends ; viscosity ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Spermatozoa of the small myzostomid worm Myzostomum cirriferum usually swim with the flagellum foremost but occasionally stop and then swim with the head foremost. The spermatozoa have axoneme of the 9+0 type; thus each lacks the central pair microtubules. The flagellum emerges in the anterior end of the cell body and attaches to it with junctions. To understand the mechanism regulating the swimming direction of the spermatozoa, we recorded the sperm and their flagellar movements using a video camera with a high-speed shutter. The effects of calcium and viscosity on these movements were also examined.The cell body with the flagellum attached to it formed a curved plate during beating, while the free portion of the flagellum beats with small helical bends. Motive force to propel a spermatozoon was mainly due to the bends in the cell body. The spermatozoa reversed the direction of their swimming as a result of a change in the direction of bend propagation. The direction of bend propagation was regulated by calcium; the bends in the cell body propagated from the end of the head toward the free portion of the flagellum at low concentrations of Ca2+, whereas the direction of bend propagation was reversed at high concentrations of this ion. High viscosity of the medium stimulated a change in the direction of bend propagation. © 1994 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 45 (1957), S. 660-675 
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The following RNA-containing components of sea urchin oocytes and eggs, some of which stratified by centrifugation, were examined in the electron microscope: the main nucleolus, the “minor nucleoli” and cytoplasmic “heavy bodies” and yolk nuclei. The inclusionfree and RNA-containing clear cytoplasm was also examined. 1. The cytoplasmic RNA content was correlated with the presence of granules, somewhat angular in size and approximately 150 Å in diameter. 2. In the yolk nuclei of the oocyte these granules were attached to membranes in a way characteristic of α-cytomembranes. In the clear cytoplasm they appear free. 3. The “heavy bodies” were surrounded by a membrane that very closely resembled the nuclear membrane. Evidence is presented that the “heavy bodies” may be derived from the nucleus, but they are not extruded portions of the main nucleolus.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 59 (1963), S. 289-308 
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fine structure of the caudal neurosecretory system in Raia batis was studied. Far-reaching similarities with ultrastructural details of other vertebrate neurosecretory systems were noted. The secretion is present in all parts of the system in the form of elementary neurosecretory granules which seem to be formed in the Golgi complex of the cell body. The morphology of the terminal region is discussed in relation to the possible mode of secretion release and in connection with the routes of secretion to the vascular lumen. The Dahlgren cell is not considered to be a secretory neuron, but a specialized glandular cell type, which has, to some extent, the same properties as nerve cells.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 46 (1957), S. 672-685 
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Reissner's fibre and the subcommisssural cells mainly from Myxine were investigated by light and electron microscope methods. The subcommissural cells carry several cilia and produce a chrome haematoxyphile secretion in the form of granules. It is probable that the nucleus as well as the mitochondria are involved in the synthesis of this material. The secretory release suggests an apocrine type in which the granules swell and form a fine-granulated, chrome haematoxyphile substance in the ventricle. Caudally in the subcommissural canal this material condenses to form Reissner's fibre, which in electron micrographs, except for a fine-granulated ground substance, does not show any structures, a limiting membrane or traces of cell organelles or remnants.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 42 (1955), S. 134-148 
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructure of the sea urchin spermatozoon has been studied by means of electron microscopy in ultra-thin sections prepared according to the technique of Sjöstrand. 1. A cellmembrane covers the spermatozoon completely; it is a double membrane with a total thickness of 100 Å units. 2. In the acrosomal region there is a particle—diameter 0.24 μ—and under this a cave filled with a less osmiophilic substance. In some Strongylocentrotus spermatozoa there is a vacuole near the bottom of this cave, it is divided into two parts, its walls measure around 200 Å, and its dimensions are about 0.1×0.2 μ. 3. The nucleus has a few small spaces with nucleoplasm within a rather homogeneous mass of irregular particles with a mean size of 95 Å. The nuclear membrane is double and has a thickness of 140 Å. 4. The middle piece is filled with mitochondrial double membranes of 190 Å; these are parallel with each other, but otherwise with random orientation. No division of the middle piece to subunits has been found. 5. The centriole is at the anterior end of the tail, located in a depression of the posterior part of the nucleus; it appears as a curved disk with a diameter of 0.15 μ. 6. Eleven filaments start at the centriole, there are two central ones which appear as single circular tubuli, there are nine peripheral ones, which appear as doublets or even triplets, with each unit having a diameter smaller than that of the central filaments. All filaments follow a straight course, have no striations and are not surrounded by helicoidal sheats. These findings are discussed together with current theories regarding sperm tail and cilia movement. 7. The tail end consists of the cell membrane and often single filament units formed by the more proximal forking of some filament doublets.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 191 (1978), S. 27-37 
    ISSN: 1432-0878
    Keywords: Spermatozoon ; Oikopleura dioica ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The spermatozoon of Oikopleura dioica is about 30 μm long, with a spherical head, about 1 μm wide, a 3 μm long and 1 μm wide midpiece, and a 25 μm long tail with a tapered end piece. The head contains a nucleus with the chromatin volume limited to about 0.1 μm3. A small acrosome is found in an anterior inpocketing, and a flagellar basal body in a posterior inpocketing of the nucleus. The midpiece contains a single mitochondrion with the flagellar axoneme embedded in a groove along its medial surface. The flagellar axoneme has the typical 9 + 2 substructure, and the basal body the typical 9+0 substructure. A second centriole and special anchoring fibres are absent.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 21 (1992), S. 65-72 
    ISSN: 1059-910X
    Keywords: Section mordanting ; Tannic acid mordanting ; Staining compounds ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The possibility that tannic acid and other classical mordants can be used in the electron microscopial section staining technique has been tested. A mordant can be defined as a chemical that combines with both a certain specific tissue component and the staining substance and thereby permits a staining reaction that otherwise will not be obtained. The following features were found to characterize section staining of tannic acid mordanted sections. Tannic acid apparently blocks those sites that normally would be contrasted by uranyl acetate or some other staining compounds. Ribosomes remain unstained. Glycogen particles, on the other hand, were stianed, whereas they are not in non-mordanted sections. In fact, glycogen was the only cytoplasmic component to be contrasted by the uranyl acetate, and collagen the only extracellular component. Several different section staining solutions gave the same staining patterns of examined cells and tissues. Specificity of the reaction thus seems to depend on the mordant rather than on the heavy atom section stain. Some other tested mordants, which have also been used in the light microscopical technique, did not give any useful new information.
    Additional Material: 26 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 202 (1989), S. 173-177 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Spermatozoa from three insect groups were examined by electron microscopy and found to have bridges that connect some of the axonemal doublets with either the two mitochondrial derivatives or, in the phasmids, the so-called laminated bodies. Within Hemiptera Heteroptera the bridges extend from doublet Nos. 1 and 5, within chrysopid neuropterans from doublet Nos. 2 and 5, and in the phasmids from axonemal doublet Nos. 2 and 4. Bridges were looked for in spermatozoa from several other insect groups but not found. The bridges in the chrysopids are regularly curved rather than straight. While bridges in heteropterans and chrysopids were seen in spermatozoa fixed with “standard fixatives,” those in the phasmids were distinctly resolved only in spermatozoa that had been fixed with a tannic acidcontaining fixative. In spite of these differences, it is conceivable that the bridges in these three insect taxa are all derived from similar, faint, bridge-like connections that sometimes can be seen to extend from all or many doublets toward the axonemal sheath of the early insect spermatid. These bridges or bridge-like structures might have a morphogenic function in that they may specify the location of the mitochondria later to become mitochondrial derivatives or, in the phasmids, of the laminated bodies.
    Additional Material: 3 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 164 (1980), S. 301-309 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Spermatozoa from eight heteropterans, each representing a different family, have been examined by electron microscopy in order to determine whether there exist characters typical for this insect group. Two such characters were found, namely bridges from the mitochondrial derivatives to the axonemal microtubules nos. 1 and 5, and two or three, rather than one, crystalline bodies within the mitochondrial derivatives. It is suggested that these characters are synapomorphic traits. The heteropteran spermatozoa lack accessory bodies typical of spermatozoa from many related groups of insects. The acrosome of the aquatic or semi-aquatic heteropterans (the infraorders Nepomorpha and Gerromorpha) has a peculiar inner structure consisting of tightly packed tubules. On the common theme of the heteropteran sperm structure, there were many variations, and the spermatozoa of each species examined can be recognized.
    Additional Material: 19 Ill.
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