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  • 1975-1979  (126)
  • 1920-1924
  • 1850-1859
  • 1978  (126)
  • Electron microscopy  (126)
  • 101
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 192 (1978), S. 267-276 
    ISSN: 1432-0878
    Keywords: Endocrine glands ; Mouse small intestine ; Mouse embryo ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The duodenum and ileum of 15 to 18-day old Swiss ICR mouse embryos were studied with the electron microscope to follow the differentiation of endocrine cells. Endocrine cells were classified on purely morphological characteristics. EC cells appeared at 16 days of gestation in both segments. At the same stage G cells were seen in the duodenum and K cells in the ileum. ECL, and S cells were identified in the duodenum at 17 days. Finally, D cells were seen at 18 days of gestation in the duodenum and ileum. With the electron microscope, endocrine cells were not identified in the small intestine of the mouse before the formation of villi.
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  • 102
    Electronic Resource
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    Springer
    Cell & tissue research 186 (1978), S. 39-52 
    ISSN: 1432-0878
    Keywords: Muscle spindle ; Nerve endings ; Acetylcholinesterase ; Cytochemistry ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Muscle spindles from lumbricalis muscles of the rat were incubated for acetylcholinesterase with a modified thiocholine-method of Lewis and Shute and examined by light and electron microscopy. All types of motor nerve ending showed heavy deposits of reaction product in the synaptic cleft. The underlying sarcoplasmic reticulum, transverse tubular system, and, when present, the envelope of sole plate nuclei were also stained. In the sensory region, the reaction was negative in the interface between the plasma membranes of the primary sensory terminal and muscle. One of two secondary sensory endings identified showed distinct reaction product in the cleft; the other secondary sensory ending showed no such reaction. Precipitates were present on the sarcolemma of the intrafusal muscle fibers in the polar and adjacent myotube regions, but not at the spindle equator. Extrafusal and intrafusal myelinated γ-nerve fibers and preterminal motor axons showed staining of the axolemma. Fibers with thick myelin sheaths and preterminal sensory axons were free of acetylcholinesterase activity, as were the unmyelinated nerve fibers.
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  • 103
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 186 (1978), S. 507-525 
    ISSN: 1432-0878
    Keywords: Human thymus ; Age involution ; Cellular composition of cortex, medulla and connective tissue ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Age involuted thymus tissue from a middle aged (33 years) and an old (63 years) man have been examined by electron microscopy and compared with thymus tissue from children. Biopsies had been taken during surgical correction of congenital heart defects. The fine structural architecture of cortex, medulla and connective tissue in the remaining lymphatic islands in the adult thymus investigated was not different to the thymus of children. We were surprised to find vigorous lymphocytopoiesis in the cortical regions and to recognize extended areas of medulla with a cellular composition which obviously provides the same microenvironment for T-cell maturation as the medulla of the non involuted thymus. Our findings are discussed in relation to the increasing arguments that the human thymus serves an immunological function throughout life.
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  • 104
    ISSN: 1432-0878
    Keywords: Pancreatic β-cells (mouse) ; Formation and storage of insulin ; Role of zinc and calcium ; Culture of islets ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. The effects of culture of isolated mouse islets of Langerhans for up to 9 days in media which had been depleted of zinc electrochemically or with the chelating agent Tris-(2-aminoethyl) amine, or of calcium, have been compared. 2. An 83% reduction of extracellular zinc concentration did not adversely affect proinsulin biosynthesis, conversion of proinsulin to insulin, or the ability of cells to store newly formed insulin in granules. When incubation media were depleted of both zinc and calcium the β-cells produced abnormally large electron-lucent granules, consistent with the failure of insulin to crystallise within the granule sac. 3. Very similar results, with formation of large electron lucent granules, were obtained after culture of islets in the absence of calcium but in the presence of normal concentrations of zinc. 4. It is suggested that zinc may play a less critical role in the biosynthesis of proinsulin and its conversion to insulin, while calcium may have a more important function in insulin storage, than has sometimes previously been supposed.
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  • 105
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    Springer
    Cell & tissue research 188 (1978), S. 171-187 
    ISSN: 1432-0878
    Keywords: Embryonic heart ; Crustacea (Homarus americanus) ; Cardiac muscle ; Intercellular junctions ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The cellular organization of the embryonic heart of the lobster Homarus americanus was examined in 6-week and 6-month-old animals. The heart wall consists of an outer adventitial layer of fibroblast cells and an inner layer of transversely striated myocardial cells. Present in close association with the myocardium are cardiac neurons, hemocytes and so-called storage cells. Adjacent fibroblasts form fasciae adhaerentes and gap junctions. Adherent junctions also occur between fibroblasts and myocardial cells. Intercalated discs and differentiated membrane regions of close apposition (4 nm) occur between adjacent myocardial cells. The cardiac neurons form a ganglion that contains four small and five large somata. Regions of neuropil are present. Motor axons arising from the cardiac ganglion form neuromuscular synapses with the myocardial cells. The storage cells contain large inclusions and form gap junctions with the myocardial cells. They may supply nutritive material to the developing myocardium. The heart at 6 weeks is about 200 μm long and 160 μm wide. At 6 months, it is about 300 μm long and 250 μm wide. The myocardium at 6 weeks is one cell layer thick, and the cells are from 2–6 μm in maximum width. At 6 months the myocardium is 2–4 cells thick, and the cells are from 6–12 μm in width. Therefore, the myocardium grows by an increase in the number and size of the myocardial cells.
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  • 106
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    Cell & tissue research 186 (1978), S. 121-133 
    ISSN: 1432-0878
    Keywords: Proximal tubule ; Tight junctions ; Ultrastructure ; Electron microscopy ; Freeze fracturing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The morphology of tight junctions of the renal proximal tubule was studied comparing the pars convoluta and pars recta of rat, golden hamster, rabbit, cat, dog and tupaia. Though some interspecies variations were observed, the convoluted portions of the proximal tubules revealed quite uniformly very leaky tight junctions with mainly 1–2 strands. Along the whole proximal tubule of the rabbit kidney including the pars recta only minor differences of the zonulae occludentes were found. By contrast, the tight junctions of the pars recta in other species were much more elaborate, especially in cat and tupaia, having up to 6 strands and an overall depth of more than 150 nm. The implications of these findings are discussed with special regard to the functional differences between the pars convoluta and pars recta of the proximal tubule.
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  • 107
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    Springer
    Cell & tissue research 186 (1978), S. 535-540 
    ISSN: 1432-0878
    Keywords: Skeletal muscle ; Satellite cells ; Regeneration ; Electron microscopy ; Autoradiography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Satellite cells were traced autoradiographically during the regeneration of skeletal muscle in young Sprague-Dawley rats. Approximately 31% of the satellite cells in uninjured muscles appeared labelled after three injections of tritiated thymidine; none of the myonuclei were labelled in the same muscles. Four to six days after transplanting the radioactive muscles to non-radioactive littermates, regenerating myotube nuclei in the host appeared labelled. Thus, this study confirms that satellite cells in young rats can differentiate into multinucleated myotubes following muscle injury.
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  • 108
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    Cell & tissue research 187 (1978), S. 439-448 
    ISSN: 1432-0878
    Keywords: Urinary bladder epithelium (Rat) ; Gap junctions ; Tight junctions ; Electron microscopy ; Freeze-fracturing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The junctional connections between the cells of the urinary bladder epithelium in rat have been studied by freeze-fracturing. Tight junctions and desmosomes are known as structural features of the epithelium. In addition, gap junctions (nexus) have been found to connect the epithelial cells in an irregular distribution pattern. The junction size ranges from few assembled particles up to plaques with irregular forms. This may indicate that the gap junctions are mobile structures. The functional significance of the junctions in comparison with electrophysiological data is discussed.
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  • 109
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    Cell & tissue research 187 (1978), S. 457-472 
    ISSN: 1432-0878
    Keywords: Ovarian follicles (sheep) ; Theca interna ; Oestrogen ; Androgen ; Capillaries ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The theca interna of non-atretic ovarian follicles from 2.0 mm in diameter up to the stage shortly following ovulation was studied by light and electron microscopy. In follicles 〈3.0mm in diameter, the theca interna consisted of about 8–12 layers of flattened cells, together with many capillaries and small bundles of collagen. Two main forms of cellular differentiation were seen. These were towards either fibroblast-like cells or presumed steroidogenic cells whose cytoplasm contained large amounts of predominantly smooth tubular endoplasmic reticulum, to which some ribosomes were attached. The majority of cells were of relatively undifferentiated or intermediate structure. In larger follicles up to the early stages of oestrus the theca interna cells became larger and less flattened, and cells rich in tubular endoplasmic reticulum became proportionately more numerous. By 18 h after the onset of oestrus the theca interna was oedematous, and many cells possessed pseudopodia. Many cells also contained numerous lipid droplets, but there were no signs of thecal cell degeneration or death. Shortly after ovulation the basal lamina of the membrana granulosa was incomplete, and it became more difficult to distinguish between theca and granulosa layers. Structural heterogeneity, with two major cell types and cells of intermediate structure, was present at all stages. It was concluded that: (1) the theca interna of 2.0–2.9 mm follicles contained many cells whose structure was compatible with a steroidogenic capacity; (2) changes in the differentiated thecal cells up to the early stages of oestrus were quantitative rather than qualitative, and suggestive of an increased steroidogenic capacity; (3) the accumulation of lipid in many cells of the theca interna by 18 h after the onset of oestrus probably reflected a reduction in steroidogenic activity; and (4) there was no evidence of any structural specialization to facilitate the transport of steroids from the theca interna to the membrana granulosa.
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  • 110
    ISSN: 1432-0878
    Keywords: Serum and pituitary LH ; Rat gonadotrophs ; LH-RH and Granule release, Synthesis and Degradation ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The effects of single and repeated LH-RH injections at 120 min intervals on female rat LH gonadotrophs and on pituitary and serum LH levels were investigated using electronmicroscopy and radioimmunoassay. A temporary stimulation of granule release, of protein and new granule synthesis and of the accumulation of lysosomal structures was found in LH cells after the first LH-RH injection. The temporary stimulations were massively enhanced after the second injection. These consecutive yet in their time-sequence overlapping processes account for the initial depletion of secretory granule content (3–15 min after LH-RH injection), for the subsequent regranulation and accumulation of granules above control levels (60–120 min after injection) and also for the reduction in the number of granules to control levels (150 min after LH-RH injection and thereafter). Increased polymorphic lysosomal structures are believed to be responsible for this reduction of excess granules. The amount of assayable pituitary and serum LH generally corresponds with the morphological changes observed in LH-gonadotrophs, thus further substantiating the above observations. A schema which summarizes the observed morphological and hormonal changes in their time-sequence in response to LH-RH stimulation depicts the short-term regulation of secretory processes in female gonadotrophs.
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  • 111
    ISSN: 1432-0878
    Keywords: Endometrium ; Rabbit ; Reproductive cycle ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Changes occurring on the surface of the uterine luminal epithelium of the rabbit during the estrous and progestational stages of the reproductive cycle were examined by scanning and transmission electron microscopy. The findings demonstrate that the uterine epithelium, or endometrium, contains two cell types: ciliated cells and nonciliated, microvillous cells. In estrous animals, ciliated cells, although not very numerous, were usually observed in small groups. However, at increasing intervals of time following mating, ciliated cells progressively disappeared from the endometrium until approximately eight to ten days post coitum, when they became scare. From several hours to four to five days following mating, extensive changes occurred on the surfaces of microvillous cells. When observed by TEM, these elements contained organelles typical of cells involved in the synthesis and secretion of glycoproteins. Furthermore, microvillous cells during this period displayed numerous apical protrusions of different sizes and shapes and containing material of varying electron density. Parallel SEM examinations of the same material confirmed the presence of these protrusions. Some of the protrusions appeared as spheroidal masses attached to the cytoplasm by means of a cytoplasmic strand. Other surface masses were clearly unattached to the cell surface and were distributed (1) on the surface of microvillous cells, (2) on the cilia of adjacent ciliated cells, and (3) on the surface of spermatozoa. Changes occurring on the luminal surface during the early postcoital period are interpreted as an expression of morphodynamic processes likely involving coupled secretion (exocytosis) and resorption (endocytosis) of luminal material. The observations presented here also demonstrate that between six and ten days post coitum, the rabbit endometrium contained increasing numbers of enlarged, nonciliated cells that probably arose by the fusion of smaller, microvillous elements.
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  • 112
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    Cell & tissue research 190 (1978), S. 301-316 
    ISSN: 1432-0878
    Keywords: Trachea (Guinea-Pig) ; Plexus submucosus ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructure of the nerves forming the submucous plexus of cervical and thoracic parts of the trachea was studied in the guinea-pig. Specimens were obtained from 6 animals perfused with warm fixative and from 6 animals in which pieces of trachea were incubated in buffer containing 5-hydroxydopamine before being immersed in cold fixative. Of the two types of axonal terminal identified in the nerves, one contained mainly large dense-cored vesicles, and the second contained numerous small vesicles. In specimens incubated in 5-hydroxydopamine, the small vesicles of the latter terminals exhibited the electron-dense cores which are characteristic of adrenergic axonal terminals. Counts made on perfused specimens showed that, in both the thoracic and cervical parts of the trachea, the density of adrenergic terminals was higher than that of terminals containing mainly large dense-cored vesicles. Overall terminal density was, however, higher in the thoracic than in the cervical part of the trachea, and estimates of nerve size showed that this was associated with the presence in the thoracic plexus of a substantially greater proportion of nerves with less than 6 axons. The possible function of the nerves in the control of the calibre of the submucous blood vessels was discussed.
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  • 113
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    Cell & tissue research 190 (1978), S. 357-369 
    ISSN: 1432-0878
    Keywords: Ampullary organs ; Siluroidea ; Sensory cells ; Synaptic junctions ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Ampullary organs were found in the epidermis of the paddle-fish Sorubim lima; they are distributed all over the skin surface of the fish but are particularly densely grouped in the head region and on the dorsal surface of the paddle. Histological and electron microscopical observations show that their structure is similar to the type of cutaneous ampullary organs characteristic of other Siluroidea. Composed of a relatively large mucus-filled ampulla, the organ possesses a short and narrow canal which leads to the outer epidermal surface. The wall of the ampulla is formed of several layers of flat epidermal cells. In general four sensory cells, each one surrounded by supporting cells, compose the sensory epithelium at the bottom of the ampulla. The inner surface of the sensory cells in contact with the ampullary mucus bears only microvilli. The contact between the nerve endings and the sensory cells show the characteristic structure of an afferent neuro-sensory junction. Two ampullae are innervated in some cases by the same afferent nerve fibre.
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  • 114
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    Cell & tissue research 190 (1978), S. 539-552 
    ISSN: 1432-0878
    Keywords: Prostate ; Praomys natalensis ; Castration ; Changes ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Male ventral and female prostates of Praomys (Mastomys) natalensis were examined with the electron microscope. The findings support and add to information obtained with the light microscope on tissues from normal, castrated and ovariectomised animals. Our results indicate that although the female prostate may be considered a homologue of the male ventral prostate anatomically and histologically, there are differences in sub-cellular morphology and hormone dependence. Cells of the intact ventral prostate of the male are characterised by prominent dilated Golgi vesicles and electron-dense “mature secretory granules” seen in the apical region of the cell. In the cells of the female prostate these features are absent. These morphological differences reflect the influence of hormones upon the cells, as shown by the reduction of the dilated Golgi vesicles in the castrated male and conversely, their occasional presence in the cells of the oestrous female. Comparison of castrated and ovariectomised animals shows that the male ventral prostate is much more dependent on androgens than the female is on ovarian hormones. There are several modes of secretion in the male ventral and the female prostate. These are by acellular and cellular blebbing, by a variety of secretory vesicles into the acinar lumina, and by a system of “double walled” vesicles not previously described.
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  • 115
    ISSN: 1432-0878
    Keywords: Adrenal medulla ; Dog ; SGC cell ; Histochemistry ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Small granule chromaffin cells (SGC cells) were identified in the adrenal medulla of adult dogs. They were small in size and usually showed a high nucleo-cytoplasmic ratio. Cytoplasmic projections were occasionally observed in some of these cells. They contained a variable number of small secretory granules with diameters ranging from 70 to 300 nm, but mostly from 100 to 200 nm. The densities of the secretory granules were variable, ranging from highly dense to less dense. These adrenal SGC cells were rich in free ribosomes and polysomes, but were relatively poor in other cell organelles. Chromaffin cells which were intermediate in their characteristics (IM cells) between the SGC cells and the typical A and N cells were also identified. These IM cells contained both highly electron dense and less dense granules in various proportions. The IM cells were classified into two subgroups, according to the proportions of adrenaline type granules and noradrenaline type granules. One group resembled A cells (IM-A cells) and the other resembled N cells (IM-N cells). Light microscopic histochemical studies of A cells stained with the ammoniacal silver solution demonstrated that they contained a small number of darkly stained granules. Electron microscopic cytochemistry revealed that the electron dense granules in the SGC cells, IM cells and A cells reacted positively with both the potassium dichromate solution at pH 4.1 and the ammoniacal silver solution.
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  • 116
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    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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  • 117
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    Cell & tissue research 188 (1978), S. 509-520 
    ISSN: 1432-0878
    Keywords: Cerebellar cortex (Cat) ; Postnatal development ; Myelination of efferent and afferent fiber systems ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The myelination of the cerebellar cortex of the cat was investigated in 61 cats aged from 3 hrs post partum to two and a half years. The first myelinated fibers appear at the time of birth in the central medullary ray. Before the onset of myelination, all fibers reach a critical diameter of about 1 μm. About the 14th day of life the number of oligodendrocytes in the prospective white matter increases markedly. Thereafter, the oligodendrocytes invade the inner granular layer. It therefore seems that the myelination of the cerebellar cortex proceeds from the central medullary ray towards the granular layer. At the 60th day of postnatal life, most of the afferent and efferent fiber systems are myelinated. These findings are discussed in relation to the development of function and the maturation of the electrical activity of the cerebellar circuit.
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  • 118
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    Cell & tissue research 189 (1978), S. 1-18 
    ISSN: 1432-0878
    Keywords: Kidney medulla ; Rat, rabbit, gerbil ; Interstitial cells ; Lipid droplets ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The inner zone of the renal medulla of rats, gerbils, and rabbits was investigated to determine whether or not there are any characteristic ultrastructural differences between the interstitial cells of these species. The effects on the interstitial cells of water deprivation and water loading were also investigated. In all three species, the Type 1 interstitial cells, the lipid containing cells, were abundant and their distribution and topographical relations as well as their general ultrastructure were similar. The previously reported significantly higher frequency in desert rats could not be confirmed. Although the lipid droplets of the interstitial cells were smaller in gerbils and rabbits when compared to rats, their fine structure was similar. Their electron dense outer zone was sometimes associated with a granular material and/or a lamellar material with a periodicity of about 40 Å resembling phospholipid “myelin figures”. Water-loaded rats showed a considerable increase in the number of lipid droplets when compared to dehydrated or untreated animals. In contrast, the interstitial cells of waterloaded gerbils and rabbits were depleted of lipid droplets.
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  • 119
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    Cell & tissue research 192 (1978), S. 461-474 
    ISSN: 1432-0878
    Keywords: Cerebral vessels ; Venules ; Pericytes ; Electron microscopy ; Microvasculature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Intracerebral venules of the cat were examined to establish criteria for a distinct separation between the venous and arterial system, and to characterize, in greater detail, the mural construction of individual venules. The intracerebral venules were compared with those of other organs. Venules do not have a vascular wall composed clearly of endothelium, media, and adventitia, as is characteristic of arteries and arterioles. The venous endothelium has a similar structure to that of capillaries. The periendothelial cells of the venule differ in shape depending on the vascular diameter. The number of periendothelial cell processes in postcapillary venules increases progressively. Segments in which the basal lamina of the endothelium merges with that of the glia cover a smaller portion of the circumference than in venous capillary loops. In collecting venules, the endothelium is almost completely enveloped by periendothelial cells which have a larger number of filaments. There are no typical smooth muscle cells in the intracerebral venules. The perivascular space becomes wider in collecting venules, contains adventitial cells, phagocytes and a great number of collagen fibers.
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  • 120
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    Cell & tissue research 193 (1978), S. 11-23 
    ISSN: 1432-0878
    Keywords: Tectorial membrane ; Organ of Corti ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The tectorial membrane (t.m.) of mammals, which lies over the organ of Corti, is made up of an agglomerate of protofibrils of varying degrees of hydration. Two types of protofibrils are clearly distinguishable in the mouse t.m. While type-A protofibrils are straight and unbranched (thickness: 110Å) demonstrating a periodic structure (period = 70Å), type-B protofibrils are branched and coiled (thickness: 150–200Å). These protofibrils could be systematically ordered according to the different t.m. zones. Type-A protofibrils predominate in the basal layer and in the entire middle zone, where they are interlaced with strongly hydrated type-B protofibrils. Weakly hydrated type-B protofibrils essentially make up the marginal zone (with the marginal net), the covering net, Hensen's stripe and the immediate contact layer with the limbus.
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  • 121
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    Cell & tissue research 193 (1978), S. 41-59 
    ISSN: 1432-0878
    Keywords: Electrical synapse (frog) ; Electrotonic coupling ; Electron microscopy ; Freeze fracture ; Gap junction ; Mixed synapse ; Motoneuron
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Freeze-fracture replicas and ultrathin sections were used to characterize the gap junctions on the somata and large dendrites of frog motoneurons found earlier by Sonnhof et al. (1977). In freeze-fracture replicas one of the specific features of these relatively frequent gap junctions is the presence of circular regions of non-junctional membrane (“fenestrae”) within areas of typical gap junction appearance displaying P-face particles or E-face pits. Such “fenestrated” gap junctions are mostly associated with membrane specializations indicative of the active zone of a chemical synapse (including vesicle attachment sites in non anaesthetized animals) to constitute mixed synapses. These findings could be verified in ultrathin sections, which revealed that the vesicles of the chemical component of the mixed synapses were spherical and agranular. Our results suggest that the mixed synapses are predominantly axo-somatic and axo-dendritic. The existence of dendro-dendritic gap junctions in the ventral horn region as described by Sotelo and Taxi (1970) was verified in ultrathin sections; they were rare, solely electrotonic in character, and probably represent the morphological basis for the VR-EPSP (Katz and Miledi, 1963; Kubota and Brookhart, 1963), i.e. electrotonic coupling between motoneurons of different spinal segments (Washizu, 1960). Electrotonic coupling can also be demonstrated between motoneurons and afferent fibers of the dorsal root and the lateral column. Electrotonic potentials recorded within motoneurons during electrical stimulation of dorsal root or lateral column precede the chemical postsynaptic potentials; after Mn2+ blockade of chemical synaptic transmission, the electrotonic component persists. Some fibers of these afferent pathways are therefore assumed to act monosynaptically on the motoneuron via mixed axo-somatic and axo-dendritic synapses.
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  • 122
    ISSN: 1432-0878
    Keywords: Olfactory epithelium ; Supporting cells ; Protuberances ; Electron microscopy ; Insectivora ; Talpidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The regio olfactoria of the mole, Talpa europaea, was studied by scanning and transmission electron microscopy. Peculiar structural differentiations, i.e. ovoid-shaped, balloon-like protuberances were found on the surface of the supporting cells. The apical portion of these protuberances contained finely dispersed granular material, whereas in their central part vesicular extensions of the smooth endoplasmic reticulum were observed.
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  • 123
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    Cell & tissue research 194 (1978), S. 183-205 
    ISSN: 1432-0878
    Keywords: Bone marrow ; Heterophil granulocytes ; Granules ; Guineapig ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The development of the heterophil granulocytes in the bone marrow of the guinea pig is described. During the maturation of these cells, three types of granule are formed, not only the azurophil and specific granules already described in other mammals but also a third type of granule referred to here as the nucleated granule. During the process of maturation of the cells, these three types of granule are formed successively. On this basis, two steps can be distinguished in the promyelocyte phase in which primary (nucleated and azurophil) granules are formed, i.e. an early and a late stage, nucleated granules being formed in early and azurophil granules in late promyelocytes. Secondary (specific) granules occur first in myelocytes. In mature heterophils of the guinea pig the granule population is composed of about 85% secondary granules, about 10% azurophil granules, and about 5% nucleated granules. The changes in the granule population during the maturation process were quantified. The observations and calculations point to the occurrence of three mitoses: one in the early and one in the late promyelocyte and the third in the myelocyte.
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  • 124
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 189 (1978), S. 515-523 
    ISSN: 1432-0878
    Keywords: Protonephridium ; Rotifer ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The excretory system of Habrotrocha rosa consists of two protonephridia. From each of them seven tubules lead to a terminal organ, also called cyrtocyte. Its weir basket contains structures which resemble ciliary rootlets. The lumen of the excretory system is bordered by a syncytial layer of cytoplasm. Cells are only found in the upper region of the trunk, where the channel is twisted several times.
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  • 125
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 189 (1978), S. 525-535 
    ISSN: 1432-0878
    Keywords: Alimentary system ; Rotifer ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The alimentary system of Habrotrocha rosa is composed of the alimentary channel, five digestive glands and another gland which is in close relation to the intestinal syncytium. After the present investigation, the alimentary channel can be divided into sections which clearly differ from each other, these are: oral cavity, pharynx, oesophagus, mastax, stomach-hose, syncytium of intestine, and terminal intestine.
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  • 126
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 191 (1978), S. 449-462 
    ISSN: 1432-0878
    Keywords: Ileum (Rat) ; Occluding junctions ; Freeze-fracture ; Ultrastructure ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Two kinds of occluding junctions are found between ileal epithelial cells of suckling rats: apical zonulae occludentes (ZO) and fasciae occludentes (FO) which are associated with the lateral plasma membranes of many epithelial cells. In unfixed preparations, glycerol treatment induces the further proliferation of extensive fasciae occludentes. Both kinds of junction have identical structural elements when visualized in freeze fracture replicas, although the arrangement of these elements differs. Zonulae occludentes consist of networks of branching and anastomosing linear ridges or rows of ∼10 nm particles with 20–30 nm spaces between the rows which form narrow belt-like structures around the apical region of adjacent cells. Fasciae occludentes, on the other hand, consist of similar linear ridges or rows of particles but the junction strands are often discontinuous, open ended and only occasionally intersect with each other. Several different fracture planes through the plasma membrane in the region of the occluding junctions have been observed and these provide further evidence that two components, one from each membrane, fused at the level of the extracellular space, form the junction sealing element. Furthermore, we present evidence which indicates a staggered rather than an in-register arrangement of these two components.
    Type of Medium: Electronic Resource
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