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  • Articles  (411)
  • Electron microscopy  (378)
  • 01. Atmosphere::01.01. Atmosphere::01.01.07. Volcanic effects
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  • Springer  (411)
  • American Geophysical Union
  • Copernicus
  • 1975-1979  (411)
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  • Articles  (411)
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  • Springer  (411)
  • American Geophysical Union
  • Copernicus
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  • 101
    ISSN: 1432-0878
    Keywords: Cardiac sarcomeres ; Tmetonyx cicada (Crustacea) ; T-tubules ; Sarcoplasmic reticulum ; Couplings ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The membrane systems of the cardiac muscle cell of the amphipod Tmetonyx cicada (O. Fabricius) are described. The sarcolemma invaginates and forms a transverse network of tubules at the level of the Z band. Narrow longitudinal tubules branch from the network and connect to another transverse network of tubules at the H band level, where dyadic and triadic junctions are formed with the sarcoplasmic reticulum. Adjacent myofibrils are normally separated by a well developed double layer of the sarcoplasmic reticulum. In areas where the myofibrils closely approach the outer sarcolemma, peripheral couplings have been found at the level of the H band.
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  • 102
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    Cell & tissue research 174 (1976), S. 99-108 
    ISSN: 1432-0878
    Keywords: Axonal spheroids ; Spinal cord ; Rabbit ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Within the gray matter and the white matter of the spinal cord of apparently healthy rabbits, myelinated and unmyelinated axonal swellings, so called “axonal spheroids”, occur. Most of the spheroids contain mitochondria, dense bodies, vesicles and fragments of the tubular or smooth endoplasmic reticulum. In myelinated spheroids the process of swelling is effected by slippage of the myelin leaflets. At the periphery of the unmyelinated parts of the spheroids, synapses are regularly found. The presynaptic terminal bouton is formed by the spheroid. A few myelinated and unmyelinated spheroids are packed with fine granular material while mitochondria are lacking. The axonal spheroids may represent a physiological, perhaps age dependent phenomenon.
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  • 103
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    Cell & tissue research 174 (1976), S. 281-288 
    ISSN: 1432-0878
    Keywords: Striated muscle ; Guinea-pig urethra ; Innervation ; Morphology ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Light and electron microscopic techniques have been used to determine the distribution, morphology and innervation of subepithelial striated muscle cells in the wall of the proximal urethra of the male guinea-pig. These cells form a continuous layer, immediately beneath the urethral epithelium extending from the bladder neck to the termination of the ejaculatory ducts into the proximal urethra. They differ from “typical” striated muscle fibres (as seen in the external urethral sphincter) by their small size, rich acetylcholinesterase content and the irregular arrangement of intracellular myofilaments and sarcoplasmic reticulum. In addition, motor end plate regions have not been observed on these striated cells when examined using a light microscopic histochemical technique. The cells are related to acetylcholinesterase positive nerves which run between them in a manner compatible with the occurrence of “en passant” synaptic interactions. Using electron microscopy, axonal varicosities containing small (50 nm diameter) agranular vesicles are encountered 50 nm from the striated cells; membrane specialisations characteristic of motor end plates have not been observed on the cells. The findings are discussed, particularly in relation to the distribution, unusual morphology and innervation of these subepithelial muscle cells.
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  • 104
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    Cell & tissue research 174 (1976), S. 427-430 
    ISSN: 1432-0878
    Keywords: Chromatoid body ; Acrosome ; Electron microscopy ; Myxine glutinosa L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Eine vorübergehende enge Beziehung zwischen dem Chromatoiden Körper und dem sich entwickelnden Acrosom wird in jungen Spermatiden von Myxine glutinosa demonstriert.
    Notes: Summary A transient close relationship between the chromatoid body and the developing acrosome is demonstrated in early spermatids of Myxine glutinosa.
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  • 105
    ISSN: 1432-0878
    Keywords: Ecdysial gland (crab) ; Regression ; Rhizocephalan parasite ; Absorptive roots ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ecdysial glands (Y organs) of the crab Carcinus maenas regress in the presence of an external parasite, Sacculina carcini. This regression is more or less severe and may lead to complete autolysis. Three gradual stages in this involutionary process are described. In stage I, the gland cells are nearly normal. Nuclei and cytoplasmic organelles remain unchanged, but large vacuoles begin to appear. Stage II corresponds to more or less drastic nuclear pyknosis and cytoplasmic alterations. Myelin figures are large and numerous. Lysosomes and autophagic vacuoles with phosphatase activity are abundant. However, the general cellular architecture remains preserved. Stage III corresponds to irreversible cytolysis; nuclear envelopes and plasma membranes have disappeared. What remains is an accumulation of cellular debris becoming engulfed by circulating hemocytes. Not all of the gland cells of any given Y organ show the same degree of regression; degeneration is asynchronous. Structures seemingly corresponding to absorptive roots of the parasite are seen. Their lumen is coated with microvilli. The putative direct and indirect influences of the rhizocephalan parasite on its host are discussed. Our results on regressing Y organs of parasitized crabs are compared with those on regressing ecdysial glands of insects.
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  • 106
    ISSN: 1432-0878
    Keywords: Neurosecretory granules ; Morphometric classification ; Neurohypophysis ; Hagfish, Eptatretus burgeri ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Neurosecretory axons in the neurohypophysis of the hagfish, Eptatretus burgeri, were statistically classified into six types according to the size of secretory granules. These types are comparable with those in higher vertebrates. The concentration of each axon type is different in three regions: anterior dorsal wall, posterior dorsal wall, and ventral wall. The regional differences of the hagfish neurohypophysis are discussed in relation to the regional differentiation of the tetrapod neurohypophysis into the median eminence and the pars nervosa.
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  • 107
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    Cell & tissue research 168 (1976), S. 33-43 
    ISSN: 1432-0878
    Keywords: Human fetal pancreas ; Endocrine cells ; Argyrophil reactions ; Light microscopy ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The endocrine cells in the pancreas of five human fetuses with gestational ages of 18–20 weeks were examined by light and electron microscopy with special regard to argyrophil reactions. B-cells and typical A and D-cells were easily identified electron microscopically on the basis of their typical secretory granules. In the Grimelius argyrophil silver stain, a concentration of silver grains over the less electron dense peripheral mantle of the A-cell secretory granules was observed by electron microscopy. In the Hellerström and Hellman modification of the argyrophil Davenport alcoholic silver stain, silver grains were concentrated over the internal structures of the D-cell secretory granules. With this stain an accumulation of silver grains was also seen at the surface of the A-cell secretory granules. The argyrophil reaction of the A-granules was less pronounced than in the D-cells. In addition to B-cells and A- and D-cells, two other types of endocrine cell were observed by electron microscopy. These cells were argyrophil with the silver impregnation method of Grimelius. The electron microscopic findings at least partly explain the frequent overlapping between the two staining methods observed at the light microscope level.
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  • 108
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    Cell & tissue research 168 (1976), S. 89-99 
    ISSN: 1432-0878
    Keywords: Osteoclast ; Protein export ; Lysosome ; Electron microscopy ; Autoradiography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The present electron microscopic autoradiographic study includes a quantitative analysis of osteoclasts in vitro using tritiated leucin as a protein tracer. A significant increase in the grain density over the ruffled border and the underlying resorption zone was demonstrated two hours post pulse whereas the grain density of the remaining cytoplasm was relatively constant. This indicates a transport of newly synthesized protein from the osteoclast to the extracellular resorption zone. Earlier histochemical and biochemical experiments suggest that the exported protein may represent lysosomal enzymes to be used in the extracellular bone degradation.
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  • 109
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    Cell & tissue research 168 (1976), S. 133-140 
    ISSN: 1432-0878
    Keywords: Thyroid gland ; Follicle cell ; Junctional complex ; Freeze fracturing ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Zonulae occludentes, gap junctions and desmosomes have been demonstrated in replicas of freeze-fractured follicular cells of normal human and rabbit thyroid glands. The zonulae occludentes between the human follicular cells are composed of two to eight strands, which completely separate the intercellular space from the follicular lumen. Four to twelve or more strands are visible between the follicular cells of the rabbit thyroid gland. In the meshes of the zonulae occludentes as well as below them, gap junctions are present. They are numerous on the fracture faces of the human follicular cell membranes, but infrequent in those of the rabbit. Aggregates of particles related to desmosomes are found in the deeper meshes of the zonulae occludentes or close to them.
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  • 110
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    Cell & tissue research 175 (1976), S. 369-390 
    ISSN: 1432-0878
    Keywords: Electron microscopy ; Crustacea ; Synaptic vesicles ; Biogenic amines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The appearance and distribution of dense-core vesicles in the stomatogastric ganglion of the spiny lobster, Panulirus interruptus, were examined using transmission electron microscopy. Following five fixation techniques, three types of dense-core vesicles were identified on the basis of size and morphology. Type-I vesicles are found in a distinct neuronal fiber system that appears to be involved in chemical transmission within the ganglion. Type-II vesicles occur in nerve processes in the ganglion, in major nerve trunks and in the perineural sheath of the nerves and ganglion. Type-III vesicles are present in all neuronal somata of the ganglion. The distinct morphology and location of the three types of vesicles suggest that their functional roles differ. Furthermore, the histochemical, biochemical and physiological data available for the Stomatogastric ganglion indicate that Type-I vesicles may store dopamine.
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  • 111
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    Cell & tissue research 168 (1976), S. 277-287 
    ISSN: 1432-0878
    Keywords: Proteoglycans ; Odontoblasts, predentin, dentin ; Calcification ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The localization of proteoglycans in the predentin of the rat incisor was investigated by ultrastructural histochemistry. Ruthenium red stained the cell coat of the odontoblasts as well as intracellular vesicles. There was also a staining of the extracellular matrix, but not of collagen fibers in the predentin. Treatment with the enzyme hyaluronidase prior to staining with ruthenium red abolished the staining of the vesicles and the extracellular matrix but not that of the cell coat. Bismuth nitrate and phosphotungstic acid gave similar staining of odontoblast vesicles and extracellular matrix. It is likely that the stained structures contain proteoglycans. The importance of these proteoglycans and their ultrastructural localization are discussed in relation to intracellular transport and the calcification process.
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  • 112
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    Cell & tissue research 176 (1977), S. 23-36 
    ISSN: 1432-0878
    Keywords: Lateral line organ ; Shark (Mustelus manazo) ; Neuromasts ; Cell types ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The lateral line organ of the spotted shark is characterized by its semi-cylindrical shape. Each organ (neuromast) is so closely apposed to the next that the individual neuromasts are almost continuous. The neuromast is composed of receptor cells, supporting cells and mantle cells. The receptor cells bear one kinocilium and up to 40 stereocilia. Bi-directional arrangement of the receptor cells as occurs in teleosts was demonstrated. Afferent and efferent nerve endings were found at the base of the receptor cells. The supporting cells extend from the basal lamina to the free surface. Long microvilli and a cilium-like “ciliary rod” project from the top of each supporting cell. The cell contains relatively few elements of the Golgi apparatus and little rough endoplasmic reticulum, but mitochondria and filaments are abundant. The mantle cell limits the lateral margin of the neuromast. It is distinguished from the supporting cell because of its long crescent-shaped nucleus and scarce, short microvilli. Myelinated nerve fibres are found in the subepithelial connective tissue but not in the epithelium. The fine structure of the shark lateral line organ suggests that this organ is in an intermediated step of evolution between that of lamprey and teleost.
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  • 113
    ISSN: 1432-0878
    Keywords: OsO4 ; Cholesterol ; Symbiotes ; Aphids ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Pea aphids left for 48 h in unbuffered osmium tetroxide show heavy staining of many organelles in the symbiote-containing cells (mycetocytes and sheath), embryos and oenocytes very similar to that characteristic of mammalian sterol-synthesizing cells. However, the staining of the pea-aphid cells is, to a large extent, dependent on the presence of cholesterol benzoate, or free cholesterol, in the aphid's diet. In aphids cultured in vitro with 3H mevalonate in the presence of added cholesterol, the incorporation of label into the cholesterol and lanosterol fractions is significantly reduced. If the dietary cholesterol effects a similar inhibition in vivo, the cholesterol-dependent osmium staining could be due to precursors(s) of cholesterol accumulating in the intracellular sites described. There is also osmium staining of large (normally electron-transparent) vacuoles in mycetocytes, gut and fat body, irrespective of dietary cholesterol.
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  • 114
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    Cell & tissue research 175 (1976), S. 403-416 
    ISSN: 1432-0878
    Keywords: Mammals ; Mole ; Male genital system ; Accessory sex organs ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The mole has a single pair of accessory sex organs with features of both the prostate and the seminal vesicle, for which the term prostate gland is not appropriate. Seasonal changes occurring in this gland were related to four periods: a) the quiescence period, b) the maturation period, c) the active period and d) the involution period. During the quiescence period the cuboidal epithelial cells display a quasi-embryonic fine structure and are sparse in cytoplasmic organelles, but rich in glycogen and lipopigment. With the onset of sexual activity glycogen and lipopigment disappear and the rough endoplasmic reticulum as well as the Golgi apparatus begin to proliferate. The fully active gland is lined by a low epithelium with parallel stacks of rough endoplasmic reticulum, a large Golgi apparatus and several lysosomes and secretory granules. In the involution period the gland collapses and the epithelial cells are eliminated by hetero-and autophagic processes. During this period a great number of presumably endocrine cells were observed. The results were compared with findings in experimental studies and those on postnatal development of accessory sex glands in laboratory animals.
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  • 115
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    Cell & tissue research 176 (1977), S. 417-429 
    ISSN: 1432-0878
    Keywords: Fat body ; Galleria mellonella ; Basement membrane ; Ruthenium red staining ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fat body lobes of Galleria mellonella are surrounded by basement membrane — a fine granular layer of connective tissue. This membrane has an affinity for ruthenium red. The results obtained after treatment of the fat body with neuraminidase, hyaluronidase, phospholipase C and proteolytic enzymes suggest that glycoproteins and phospholipoproteins are constituents of this basement membrane. The basement membrane also has the ability to bind concanavalin A-peroxidase, which is associated with the presence of mannoside residues.
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  • 116
    ISSN: 1432-0878
    Keywords: Skeletal muscle ; Protamine ; Endocytosis ; Autophagic vacuolation ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The uptake in vitro of horseradish peroxidase (HRP) in mouse skeletal muscle was examined by electron microscopy and chemical determination. In muscles exposed to an HRP solution for 60 min at +37°C, HRP infiltrated the basal lamina of muscle fibres and caused an intense labelling of their sarcolemma. In addition HRP was found within the transverse tubules. Exposure to HRP for 30 min at +37°C followed by HRP together with a polycationic protein (protamine) for 30 min at +37°C caused an intracellular vesicular uptake of HRP. Intracellular HRP was found in numerous vesicles, membrane limited bodies and vacuoles. Protamine also induced focal autophagic vacuolation with progressive muscle fibre degeneration. An intracellular HRP uptake or muscle cell vacuolation could not be detected in the absence of protamine or when the incubation temperature was + 4°C. Chemical determination of HRP uptake was in general agreement with the morphological results. The uptake of HRP in the presence of protamine was stimulated at +31°C and blocked at +4°C. The results suggest that in skeletal muscle in vitro intracellular uptake of macromolecules occurs by endocytosis.
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  • 117
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    Cell & tissue research 167 (1976), S. 179-195 
    ISSN: 1432-0878
    Keywords: Islets of Langerhans ; Horse pancreas ; Cell types ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Das Inselorgan der Bauchspeicheldrüse des Pferdes wurde an immersions- und perfusionsfixiertem Material untersucht. Dabei ließen sich nach der Immersions- wie Perfusionsfixation fünf Zelltypen unterscheiden: 1. A-Zellen, die im Zentrum der Insel liegen, 2. B-zellen, die hauptsächlich blasse Granula enthalten und den größten Teil der Inselperipherie ausmachen, 3. D-Zellen, die ebenfalls vorwiegend in der Inselperipherie liegen, 4. G-Zellen, die am Rand der Inseln und im exokrinen Pankreas anzutreffen sind, 5. S-Zellen (“small granule cells”), die relativ selten und nur in den Inseln zu finden sind. Über die Funktion und altersabhängigen Veränderungen dieser Zellen wird diskutiert. Die Bildung von hellen und dunklen Zellen halten wir für ein Artefakt, ebenso die Bildung von sog. Mischzellen, da diese Zelltypen nur nach Immersionsfixation auftreten.
    Notes: Summary The islets of Langerhans of the equine pancreas were examined with the electron microscope after immersion or perfusion fixation. Five cell types could be distinguished after fixation by either technique: 1. A-cells, situated at the center of the islets, 2. B-cells, containing mostly “pale granules” and constituting the principal cell type of the periphery of the islets, 3. D-cells, also located mainly at the periphery of the islets, 4. G-cells, found at the edge of the islets and in the exocrine pancreas, and 5. S-cells, (small granule cells), which are relatively few in number and occur only in the islets. The function and age-dependent modifications of these cells are discussed. The formation of light and dark cells and of “mixed cells” are regarded as artifact, since cells of this type occur only under the condition of immersion fixation.
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  • 118
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    Cell & tissue research 167 (1976), S. 265-288 
    ISSN: 1432-0878
    Keywords: Myelinated fibres ; Visual cortex ; Stereology ; Development ; Electron microscopy ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary With the aid of stereological procedures the development of myelinated nerve fibres (MF) was quantitatively investigated in electron micrographs of the visual cortex from animals of different ages: 36 days-old, the age at which fibres first appear, through adulthood. A short description of tissue treatment, methods and qualitative results is given. The following quantitative results are presented: 1. Myelinization begins at about the 36th day postpartum and is not completed by the 164th day. At this time a lack of about 20% MF can be observed. 2. The average diameter of MF decreases from 1.3 μm to 0.8 μm from day 36 to adulthood. 3. The first MF appear near the border of the album. 4. Beginning with the 55th day, small MF arise in layer I, showing two periods of growth. 5. The maximum MF density in the region of layer IV corresponds to the strip of Baillarger. Other aspects of visual cortex development are dealt with in the Discussion. The following conclusions can be drawn: a) The growing of inand output-MF is completed first. b) The development of the internal connecting systems in layers I and IV begins a little later and is completed by the 5th month. c) The MF in layers II and III appear after the 4th month. Kaes (1907) has also described a continuation of MF growth in man lasting into the twenties.
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  • 119
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    Cell & tissue research 167 (1976), S. 363-371 
    ISSN: 1432-0878
    Keywords: Synapses ; Synaptogenesis ; Dense projections ; Cerebral cortex ; E-PTA ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The molecular layer of rat occipital cortex was studied at a number of ages throughout postnatal development in an attempt to formulate a quantitative morphogenetic scheme of synaptic development. As previous work had pointed to the potential usefulness of E-PTA stained material in synaptogenic studies, this technique was employed. Synaptic junctions were assigned to five categories, A-E, on the basis of variations in the organization of their presynaptic densities. Of these categories, Type A represented a mature junctional form with well-defined and discrete dense projections. Type E, by contrast, represented the immature end of the spectrum, its presynaptic apposition generally lacking recognizable densities. Types B-D represented intermediate forms. As development proceeded, the percentage of A type junctions increased from 0.3% at 7 days to 25% in the adult. Type E junctions showed the opposite trend falling from 42% at 7 days to 5% in the adult. On the basis of these results, and those relating to types B-D, possible morphogenetic schemes involving the five synaptic categories are put forward. These schemes incorporate and extend those previously suggested by other workers. By placing observations on a quantitative footing, the schemes proposed here lend themselves to use in experimental investigations.
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  • 120
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    Cell & tissue research 167 (1976), S. 373-385 
    ISSN: 1432-0878
    Keywords: Gills ; Salmo gairdneri ; Specialized endothelia ; Arteriovenous anastomoses ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The origin of arterio-venous anastomoses, connecting the efferent filament artery (EFA) with the central venous sinus (CVS) of gill filaments can be well discerned by scanning electron microscopy in the rainbow trout. Corresponding vessels between the afferent filament artery and the CVS could not be detected with the techniques applied. AVA-specific endothelial cells are characterized by their bulky shape and their microvillous surface. The general morphology of AVA's in Salmo gairdneri is very similar to that of AVA's in Tilapia mossambica (Vogel et al., 1974) but they are much longer in the trout. No filament whorls have been encountered in AVA endothelia of Salmo gairdneri.
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  • 121
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    Cell & tissue research 167 (1976), S. 527-536 
    ISSN: 1432-0878
    Keywords: Endometrium ; Innervation ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The innervation of the endometrium of rabbit, rat, mink, mongoose and pig has been investigated electron microscopically. Large bundles of nerve fibers can be observed in the connective tissue spaces within the basal layer of the endometrium. Unmyelinated nerve fibers enter the lamina functionalis, terminal nerve fibers penetrate the basal lamina and make contact with the glandular and the cavum epithelial cells. The terminal axons contain abundant synaptic vesicles, dense core vesicles and mitochondria. To date, no specialized presynaptic or postsynaptic membranes have been found.
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  • 122
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    Cell & tissue research 167 (1976), S. 563-567 
    ISSN: 1432-0878
    Keywords: Trigeminal ganglion ; Dorsal root ganglia ; Continuous endothelium ; Fenestrated endothelium ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Several fenestrated capillaries were seen in the endoneurium of trigeminal and dorsal root ganglia from two young adult albino rats treated with tetraethylthiuram disulfide. The finding is regarded as normal, although the possibility exists that intoxication with tetraethylthiuram disulfide may have enhanced the intensity and/or rate of this cytologic specialization of some isolated endothelial cells.
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  • 123
    ISSN: 1432-0878
    Keywords: Adrenal cortex ; Mitochondria ; ACTH ; Stereology ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The effects of chronic administration of ACTH (up to 36 consecutive days) on the mitochondria of the zona reticularis of the rat adrenal cortex were investigated by stereologic techniques. It was found that ACTH induces two phases of hypertrophy of mitochondria alternating with two proliferative stages, which are associated with a significant decrease in the average volume of the organelles. It is suggested that, as in the zona fasciculata, ACTH controls the processes of growth and division of mitochondria in the zona reticularis. The mechanism underlying this action of ACTH as well as the differences between the responses to ACTH of the mitochondrial population of the two adrenal zones are discussed in the light of evidence indicating that mitochondria contain a complete genetic apparatus largely independent of nuclear control.
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  • 124
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    Cell & tissue research 168 (1976), S. 45-53 
    ISSN: 1432-0878
    Keywords: Juxtaglomerular apparatus ; Exocytosis ; Microtubules ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The epithelioid cells of the juxtaglomerular apparatus have been studied with respect to the release mechanism of the secretory granules. Invaginations of the plasma membrane into the interior of the epithelioid cells are interpreted as stages before or after an exocytotic process. Granules are sometimes observed in close contact with the plasma membrane, and material with electron density similar to that of the granules can also be observed in the invaginations. These morphological features suggest that the granular material of the epithelioid cells is extruded into the texture of the basal lamina. Furthermore, a dense network of microtubules and microfilaments is described and the functional role of this system in exocytosis is discussed.
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  • 125
    ISSN: 1432-0878
    Keywords: Muscle fibre types ; Axolotl (Ambystoma mexkanum) ; Morphometry ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Morphometric analysis by light microscopy of p-phenylene-diamine stained semithin sections of axolotl tail muscle revealed differences in the cross-sectional area of the fibres and in the number of mitochondria and of lipid inclusions per fibre, and indicated the presence of three distinct types of fibres. The tripartition was found to be statistically highly significant. Representative fibres from each group established by light microscopic morphometry were subjected to an ultrastructural morphometric analysis. The volume content of mitochondria amounted to 9.8% of the fibre volume for red, 4.0% for intermediate and 0.8% for white fibres. The myofibrils composed 60%, 70% and 83% in the same fibres. The volume of the sarcotubular system (t-tubuli and sarcoplasmic reticulum) was 2.5% in red, 4.5% in intermediate and 11.7% in white fibres. The three fibre types also demonstrated differences in myofibrillar cross-striation pattern and number of triads. The reliability of the light microscopic morphometry was tested by correlation with EM montages of the representative fibres.
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  • 126
    ISSN: 1432-0878
    Keywords: Electron dense plaques ; Pancreatic islets ; Parathyroids ; Electron microscopy ; Calcium binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Small electron dense plaques (EDP) were found in the plasma membrane of pancreatic islet A-, B- and D-cells and parathyroid chief cells of mice and gerbils. The identification of the EDP was facilitated by the use of special fixation techniques. The EDP may represent sites of calcium binding in the cell membranes.
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  • 127
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    Cell & tissue research 177 (1977), S. 127-140 
    ISSN: 1432-0878
    Keywords: Microtubules ; Retina ; Electron microscopy ; Rainbow trout
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In the retina of the rainbow trout (Salmo gairdneri, Richardson) two types of microtubular structures are demonstrated. Besides the normal type of microtubules (about 200 Å in diameter), occurring in all cell types of the retina, a second type is described which is termed microtubule-like structure (MLS) because of its extracellular localization. These MLS have a diameter of about 250 Å under the same preparative conditions in which the normal microtubules appear 180–200 Å thick. The interspace between the tubules is smaller than between the microtubules. Specific MLS to membrane associations exist, which are analyzed by serial sectioning and tilting procedures. It is suggested that the MLS have their origin at small membranous extrusions of the plasmalemma. These extrusions could contain nucleation sites for the MLS-formation within the extracellular space. It remains unknown which cell type produces the MLS proteins and which factors are responsible for the aggregation of the subunits to intact MLS.
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  • 128
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    Cell & tissue research 177 (1977), S. 221-226 
    ISSN: 1432-0878
    Keywords: Actin-like filaments ; Myoid cell ; Testis ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Microfilaments in the myoid cells of the peritubular tissue in the mouse, swine and human testis bind heavy meromyosin (HMM) and form arrowhead complexes. The periodicity of the arrowhead complexes is about 35 nm. Individual filaments show arrowheads that point in the same direction. Opposing polarity of the HMM-bound filaments is also observed. The microfilaments do not bind HMM in the presence of 10 mM ATP. After treatment with the contraction medium of Hoffmann-Berling, the filaments appear to be undulated. These observations indicate that the microfilaments in the myoid cell are actin-like in nature. A small number of thicker filaments (about 10 nm in diameter) which do not bind HMM is also observed in the cell. Microfibrils which have been reported around the human myoid cell are also found in the swine.
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  • 129
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    Cell & tissue research 200 (1979), S. 337-344 
    ISSN: 1432-0878
    Keywords: Glomerulo-tubular feedback ; Tight junctions ; Macula densa ; Distal tubule ; Electron microscopy ; Freeze fracture ; Horseradish peroxidase
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    Notes: Summary In the present study the tight junctions at the macula densa were compared to those of the adjacent straight and convoluted segments of the distal tubule using freeze fracturing and thin sectioning techniques. Only insignificant differences were found in the number of strands and the apico-basal depth of the tight junctions in the three distal tubular segments of rat, dog and tree shrew. In experiments with horseradish peroxidase on mice and tree shrews, the tracer did not penetrate the apical junctions in any of the distal tubular segments. Our findings do not support the concept of considerably higher permeability of the tight junctions at the macula densa, as previously reported. Gap junctions were never observed in the distal nephron. The present results suggest that the glomerulo-tubular feedback is more likely to be mediated by transcellular resorption of solutes than by passive diffusion through a leaky paracellular shunt pathway.
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  • 130
    ISSN: 1432-0878
    Keywords: T-lymphocytes ; Blast cells ; Lymph node ; Electron microscopy ; Stereology
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    Topics: Biology , Medicine
    Notes: Summary Changes in the volumes and surfaces of subcellular compartments of unstimulated small lymphocytes and immunoblasts in mouse axillary lymph nodes have been established using stereological techniques. Blast transformation was induced in vivo with dinitrochlorobenzene (DNCB). Cell samples were obtained by random sampling regimes applied at light and electron microscopic levels. From electron micrographs the volume densities of euchromatin, heterochromatin, nucleoli, mitochondria, Golgi apparatus and rough endoplasmic reticulum were determined. Cell surface/volume ratios were also computed. By estimating mean nuclear volumes using light microscopy, it was possible to calculate absolute compartmental volumes and to evaluate the plasma membrane surface areas of average cells. Transformation in this model was characterized by a considerable cellular hypertrophy and a substantial increase in plasmalemma surface. Hypertrophy was the consequence of increases in the volumes of all measured intracellular compartments, notably euchromatin and “residual cytoplasm” (including ground cytoplasm and free ribosomes). These changes are discussed in the context of the altered metabolic status of cells.
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  • 131
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    Cell & tissue research 163 (1975), S. 175-184 
    ISSN: 1432-0878
    Keywords: Cardiac sarcomeres ; Circolana borealis (Isopod) ; T-tubules ; Sarcoplasmic reticulum ; Couplings ; Electron microscopy
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    Topics: Biology , Medicine
    Notes: Summary The membrane systems of the cardiac muscle cell of the isopod Cirolana borealis Lilljeborg are described. The sarcolemma invaginates at the level of the Z band, forming transverse tubules. Narrow tubules branch off in a longitudinal direction from these transverse and radially arranged TZ-tubules forming a transverse collar at each A-I level, where dyadic and triadic junctions are formed with the sarcoplasmic reticulum. Two different orientations of the coupling discs have been detected in the supercontracted sarcomere, and this observation has been discussed. Adjacent myofibrils are separated by a double layer of sarcoplasmic reticulum.
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  • 132
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    Keywords: Adrenal cortex ; Mitochondria ; Dexamethasone ; DNA-synthesis ; Electron microscopy
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    Notes: Summary The effects of chronic administration of dexamethasone (for up to 15 consecutive days) on both the morphology and DNA-synthesis of the mitochondria of the rat adrenal zona fasciculata were investigated by stereologic and autoradiographic techniques. Up to the 3rd day of continuous dexamethasone treatment, the average volume of mitochondria did not change, whereas the number of mitochondria per cell was significantly decreased. From the 3rd to the 15th day of hormonal administration both the volume and number of mitochondria were found to decrease in proportion to the duration of treatment. Autoradiography showed that after the 3rd day of dexamethasone administration there is virtually no incorporation of 3H-thymidine into the mitochondrial compartment. These findings are discussed in the light of evidence indicating that dexamethasone blocks ACTH-release by inhibiting the hypothalamo-hypophyseal axis. The results confirm the view that ACTH controls the maintenance of growth and proliferation of rat adrenocortical mitochondria.
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  • 133
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    Keywords: Specific heart granules (Cyclostome) ; Atrial granules ; Calcium ; Uranophilic core substance ; Electron microscopy
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    Notes: Summary The occurrence of structural connections between myocardial granules and tubular elements of the sarcoplasmic reticulum in the cardiac ventricle of the Atlantic hagfish is described. The core substance of the myocardial granules is shown to be uranophilic and in this respect similar to the granular cores within the lumen of the sarcoplasmic reticulum. After application of CaCl2-containing fixatives, the ultrastructure of the core substance of these organelles resembles that described for calcium-containing structures in vertebrate glial cells. Incidences of uranophilic core substance in the extracellular space suggest a secretory function of the myocardial granules. Possible implications of the sarcoplasmic reticulum and the myocardial granules in storage, intracellular transport, and secretion of bound calcium are discussed.
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  • 134
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    Keywords: Optic neuropile ; Crustacea ; Catecholamine ; Fluorescence histochemistry ; Electron microscopy
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    Notes: Summary The crustacean optic neuropiles, the lamina ganglionaris and especially the medulla externa, show a specific pattern of green fluorescence with the fluorescence histochemical method of Falck-Hillarp. Normally, only the terminals and the cell bodies fluoresce, but in reserpine-treated animals exogenous catecholamines are taken up by the whole adrenergic neuron and are thus visualized as a whole. Incubating crayfish optic neuropiles in dopamine or α-methylnoradrenaline after reserpine treatment demonstrated a tangential neuron connecting the lamina and the medulla externa. The morphology of this tangential neuron differs from the two types of tangential neurons, Tan1 and Tan2, previously characterized with Golgi techniques. The catecholaminergic neuron thus constitutes a third tangential neuron type.
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  • 135
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    Cell & tissue research 182 (1977), S. 401-407 
    ISSN: 1432-0878
    Keywords: Microtubules ; Sciatic nerve (rat) ; Tannic acid ; Electron microscopy
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    Notes: Summary Tannic acid in glutaraldehyde was used to stain microtubules in myelinated and unmyelinated axons of rat sciatic nerve. In the majority of areas the tannic acid failed to penetrate the unmyelinated axons whilst penetrating neighbouring myelinated axons, suggesting a difference in the ability of the two types of nerves to exclude tannic acid. Where tannic acid had penetrated the unmyelinated axons the 13 protofilament substructure and size of the microtubules appeared identical to those seen in the myelinated axons.
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  • 136
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    Keywords: Albinism ; Pigment epithelium ; Tyrosinase ; Electron microscopy ; Carassius auratus L.
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    Notes: Summary Ultrastructural studies, and cytochemical and biochemical determinations of tyrosinase activity were conducted on the pigment epithelium of albino and xanthic goldfish eyes. In eyes of xanthic goldfish, two types of melanosomes are present, spherical and elongated. Melanized melanosomes are absent in the eyes of the albino goldfish, but elongated lamellar premelanosomes are observed. Internal vesicles are present in both melanosome types in the pigment epithelium of the xanthic goldfish but are absent in premelanosomes of the albino. There are also differences in the distribution of lipid droplets, smooth endoplasmic reticulum and Golgi complexes with the latter two being more abundant in the albino. Tyrosinase was not identified cytochemically; however, the enzyme was demonstrated biochemically in the pigment epithelia of both albino and xanthic goldfish. The enzyme is associated with the particulate and soluble fractions of both types of eyes. Particulate albino tyrosinase may be solubilized by triton X-100 treatment. Tyrosinase inhibitors are present in the particulate fractions of both albino and xanthic goldfish eyes. Thus, in the goldfish, ocular albinism appears to be a multiple defect at the molecular and ultrastructural levels.
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  • 137
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    Cell & tissue research 156 (1975), S. 253-265 
    ISSN: 1432-0878
    Keywords: Smooth muscle (Helix pomatia) ; Contractile apparatus, Functional states ; Thick myofilaments ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Summary The ultrastructure of the isolated glycerinated penis retractor muscle (PRM) of Helix pomatia was investigated. The diameter distributions of thick myofilaments from fibre cross sections in the relaxed, phasic contracted, tonic contracted, and in the catch states show that a characteristic filament spectrum is formed in the catch state and its preceding active state. The significant structural differences are discussed in relation to earlier hypotheses related to the catch state.
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  • 138
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    Keywords: Metaphyseal bone (Guinea pig) ; Osteogenic cells ; Lysosomes ; Alkaline phosphatase ; Electron microscopy
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    Topics: Biology , Medicine
    Notes: Summary A transmission electron microscopic study of demineralized, methaphyseal bone of the young guinea pig is presented. Special attention is paid to the lysosomal system of the different cell types. Visualization of acid phosphatase and aryl sulfatase activity was used to identify tissue components as belonging thereto. The distribution of alkaline phosphatase activity, a plasma membrane marker, was also examined. Osteoblasts were distinguished by a marked development of the granular endoplasmic reticulum and the Golgi complex. Perivascular cells type A, morphologically resembled the osteoblasts, and are believed to represent an early stage in the specialization of the latter. A few lysosomes were normally found in the osteoblasts; they were less common in the type A cells. In contrast to their regular occurrence in guinea pig epiphyseal cartilage, dense bodies of lysosomal nature (“type I vesicles”) were only rarely seen in the bone matrix. Structures analogous to the type II vesicles in cartilage were, however, normally present. Their membrane showed activity of alkaline phosphatase. Possible functions of lysosomes and matrix vesicles in osteogenesis are discussed. Perivascular cells type B and chondroclasts both contained a prominent Golgi complex and large numbers of free ribosomes, mitochondria and lysosomes. In the type B cells, inclusion material of varying appearance often occurred in the lysosomes and in endocytic vesicles. The chondroclasts sometimes presented a ruffled border, with associated vacuoles and lysosomes in the subjacent cytoplasm. It is suggested that both cell types participate in the resorption of the epiphyseal cartilage. Chondroclasts presumably arise by fusion of type B cells and/or monocytic precursors from the peripheral blood. The skilled technical assistance of Mrs. Eva Lundberg and the secretarial assistance of Mrs. Inger Åhrén are gratefully acknowledged. The authors are indebted to Dr. Stanislaw Moskalewski for constructive criticism of the manuscript.
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    Cell & tissue research 156 (1975), S. 301-315 
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    Keywords: Metaphyseal bone (Guinea pig) ; Osteogenic cells ; Endocytosis ; Lysosomes ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Guinea pig metaphyseal bone was exposed to horse spleen ferritin in vitro and to colloidal thorium dioxide in vivo. The cellular uptake and intracellular accumulation of these marker particles were studied ultrastructurally. In vitro, the ferritin molecules were found to spread evenly throughout the tissue. After 1–2 hours ferritin was mainly found in plasma membrane invaginations and in endocytic vesicles of varying size. At 4–6 hours a successive accumulation of the marker in secondary lysosomes could be observed. In addition to ferritin, the lysosomes and the large endocytic vesicles often contained other inclusions. In vivo, the pattern of intracellular accumulation of the marker particles was identical to that in vitro. Moreover, the presence within the cells of similar amounts of thorium dioxide after 1 and 4 days suggested that these indigestible molecules are stored intracellularly for a considerable time. In accordance therewith there were no definite signs of extrusion of labeled bodies or secretion of the exogenous marker by exocytosis. Ferritin and thorium dioxide were taken up by all cell types in the metaphysis. Both in vitro and in vivo perivascular cells type B ingested large amounts of marker particles, whereas chondroclasts, endothelial cells, perivascular cells type A and osteohlasts showed a more restricted endocytizing ability. On the basis of these observations, the functional significance of different cell types in the resorption of the epiphyseal cartilage and the formation of bone is discussed. The skilled technical assistance of Mrs. Eva Lundberg and the secretarial assistance of Mmes. Ulla Linder and Diane Setchell are gratefully acknowledged. The author is also indebted to Dr. Ulf Friberg and Dr. Stanislaw Moskalewski for constructive criticism of the manuscript.
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  • 140
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    Cell & tissue research 156 (1975), S. 463-474 
    ISSN: 1432-0878
    Keywords: Embryonic cleavage ; Drosophila embryo ; Membrane growth ; Electron microscopy
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    Topics: Biology , Medicine
    Notes: Summary During blastoderm formation, the Drosophila embryo produces a large area of new membrane to accommodate the simultaneous demands of approximately four thousand newly cleaved cells. The embryo was examined with the electron microscope at various stages during cleavage in order to investigate the high membrane forming capacity of these cells. Embryos were subjected to the histochemical procedure for the demonstration of thiamine pyrophosphatase. The enzyme was present in the cisternae of the endoplasmic reticulum, Golgi bodies and the nuclear envelope. No activity could be demonstrated on the furrow surface or at the furrow tip despite closely adjacent reactive cisternae. It is concluded that the endoplasmic reticulum and Golgi bodies are not major contributors to the new surface. Lamellar bodies were frequently observed in the cytoplasm of all stages examined. The bodies showed a lamellar periodicity of approximately 3.5 nm, and were ultrastructurally similar in appearance after a variety of fixation procedures. The distribution of these bodies was markedly related to the stage of blastoderm formation. Before the commencement of cleavage, lamellar bodies were very prominent within a region 4–5 μm. below the cell surface. As cleavage progressed, the bodies became sparse or absent from this region but were apparent at the base of the blastoderm cells or in the sub-blastoderm region, where they were not previously present. Lamellar bodies with leaflets closely associated with, or in apparent continuity with, the cleavage furrow membrane were frequently observed. In these regions the lamellar periodicity was the same as the thickness of the membrane laminae. It is suggested that these bodies play a role in the synthesis of new membrane in the furrow. Intercellular contact specializations between the developing membranes of the furrow were restricted to incipient desmosones and point contacts where the intercellular gap was reduced to 3 nm or less.
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  • 141
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    Keywords: Neurohypophysis ; Neurosecretion ; Neurophysin ; Neurohypophysia hormones ; Electron microscopy ; Autoradiography
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    Topics: Biology , Medicine
    Notes: Summary Electron-microscope autoradiographs have been prepared from the neural lobes of the pituitary glands of rats which had received intracisternal injections of [35S] cysteine at various times before gland removal. The rate of appearance and disappearance of autoradiographically demonstrable radioactivity in the neural lobe closely paralleled that previously determined, biochemically, for radioactive hormones and neurophysins. Radioactivity was appreciably associated with the undilated parts of neurosecretory axons only during the first few hours after injection of the label. The axonal dilations were subdivided into those in which small vesicles could be seen (“endings”) and those in which no small vesicles could be seen (“swellings”). Radioactivity appeared first in “endings” and then in progressively larger and larger profiles of “swellings”. It appeared that newly arrived granules were found close to the limiting membrane of the nerve swelling and that as time progressed they moved deeper and deeper into the swelling. On the basis of the results, suggestions were made for an anatomical explanation of the readily-releasable pool of hormone which has been demonstrated pharmacologically.
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  • 142
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    Cell & tissue research 157 (1975), S. 73-91 
    ISSN: 1432-0878
    Keywords: Eye (Sheep) ; Tapetum ; Collagen ; Microfibrils ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The structure of the tapetum of the sheep's eye has been examined by transmission electron microscopy. It consists of regularly arranged layers of collagen fibrils, estimated from the hydroxyproline content to make up about 60% of the dry weight of the tissue. There are several hundred of these layers in the whole depth, a majority being orientated in the same direction. The collagen is associated with strands of microfibrillar material as well as with cells of both fibrocyte and smooth muscle types.
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  • 143
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    Cell & tissue research 170 (1976), S. 89-94 
    ISSN: 1432-0878
    Keywords: “C” cells ; Endoplasmic reticulum ; Electron microscopy
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    Notes: Summary Multiple rough endoplasmic cisternae were found in “C” cells of the adult rat, at interphase. They are considered to be normal constituents of “C” cells. Their morphological relation to rough endoplasmic reticulum and their close proximity to mitochondria, Golgi dictyosomes and secretory granules suggest that they may have a role in the secretory activity of this endocrine cell.
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  • 144
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    Cell & tissue research 158 (1975), S. 111-120 
    ISSN: 1432-0878
    Keywords: Iris ; Rana pipiens ; M. dilatator, sphincter pupillae ; Electron microscopy ; Photosensitivity
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Summary The iris of the grass frog Rana pipiens, can respond to light even when isolated from the remainder of the animal. The iris is a three-layered structure, comprising a stromal layer and two layers of pigment epithelium. The sphincter pupillae, which is composed of pigmented smooth muscle cells, is embedded between the two layers of pigment epithelium. There is no dilator pupillae in this species. We have been unable to find any cells or any organelles in the iris which are anatomically specialized for photoreception in any obvious way.
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  • 145
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    Cell & tissue research 158 (1975), S. 333-337 
    ISSN: 1432-0878
    Keywords: Spirochete ; Artemia ; Brine shrimp ; Electron microscopy
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    Notes: Summary When tissues of spirochete-infected brine shrimp (Artemia salina) were examined by electron microscopy, tubular structures were often seen closely associated with intracytoplasmic spirochete profiles. These tubules were never observed in association with spirochetes found in the haemocoel or other extracellular spaces. Since the trilaminar layer comprising the wall of the tubules was identical in ultrastructure to the outer envelope of the spirochete, these structures were interpreted to be finger-like extensions of the spirochete outer envelope.
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  • 146
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    Cell & tissue research 158 (1975), S. 363-373 
    ISSN: 1432-0878
    Keywords: Skin pigmentation ; Melanocytes ; Melanophores ; Lungfish ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The integumental melanophores of Australian lungfish, Neoceratodus forsteri, were examined by light and electron microscopy and found to possess essentially the same structural characteristics observed in other vertebrates. The epidermal melanophores are located in the intermediate epidermis and possess round perikarya and slender dendrites extending into nearby intercellular spaces. The dermal melanophores are found immediately below the basement membrane as well as in the deeper dermis. These cells possess flattened nuclei and dendrites running parallel to the basement membrane. Each melanophore contains numerous oval or elliptical, intensely electron-dense melanosomes, relatively large mitochondria, systems of vacuolar endoplasmic reticulum, groups of free RNP particles, and some microfilaments. Only a few, short microtubules could be demonstrated in the perinuclear cytoplasm of the dermal melanophore, while a relatively large number of late premelanosomes are found both in perikarya and dendritic processes of epidermal melanophores. These premelanosomes exhibit a particulate internal structure in cross section. Both melanosomes and premelanosomes occur singly in the cytoplasm of epidermal cells, thereby confirming the existence of the epidermal melanin unit in the lowest vertebrates thus far examined electron microscopically.
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  • 147
    ISSN: 1432-0878
    Keywords: Skin pigmentation ; Melanocytes ; Melanophores ; Electron microscopy ; Lungfish
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Summary The integumental melanophores of two genera of lungfish, Lepidosiren paradoxa and Protopterus sp. were examined by light and electron microscopy. Both species possess both epidermal and dermal melanophores with fine structural characteristics basically similar to those of other vertebrates. The epidermal melanophores of both species are located in the intermediate epidermis, and possess thin perikarya containing round nuclei, and slender dendrites extending into the nearby intercellular spaces. The dermal melanophores occur immediately beneath the basement membrane, and possess flat perikarya and dendrites running horizontally between the collagen fibers of the dermis. The integument of both species does not possess an epidermal melanin unit or a dermal chromatophore unit. As in other vertebrates, each melanophore contains numerous oval, electron-opaque melanosomes, relatively large mitochondria, vacuolar endoplasmic reticula, and groups of RNP particles. Although micro filaments running randomly between other organelles occur regularly, microtubules were not demonstrated. Premelanosomes at various stages of differentiation were best illustrated in the dermal melanophores of Protopterus, and it is concluded from the observation of their fine structure that the morphological development of lungfish melanosomes closely parallels that of higher vertebrates. On the basis of melanophore morphology, Lepidosiren and Protopterus appear to be more closely related to each other than to Neoceratodus.
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  • 148
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    Cell & tissue research 158 (1975), S. 481-496 
    ISSN: 1432-0878
    Keywords: Gastric epithelium ; Ascidia (Botryllus schlosseri) ; Ciliated mucous, endocrine and plicated cells ; Structure and function ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The following five cell types have been recognized and defined on the basis of their fine structure in the gastric epithelium of B. schlosseri: vacuolated and zymogenic cells (described in a previous paper); ciliated mucous, endocrine and plicated cells. The ciliated mucous cells are distributed at the apex and the bottom of the gastric folds and along the dorsal groove. The mucus droplets appear to form from the Golgi complex as secretory granules of variable density and texture, which are released from the cell after fusion of their membranes with the apical plasma membrane. Holocrine or apocrine secretion has not been observed. The endocrine cells are scattered and are characterized by electron dense granules, especially numerous in the basal region of the cell. Finally, the plicated cells, present in the pyloric caecum, show rod-like microvilli, a well developed Golgi complex and abundant, deep infoldings of the basal plasma membrane, which are associated with numerous mitochondria. The possible role of the gastric cell types is discussed taking into account information concerning morphologically similar cells in other animals, as well as previously reported data on the biochemistry and physiology of digestion and excretion in ascidians.
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    Cell & tissue research 158 (1975), S. 517-541 
    ISSN: 1432-0878
    Keywords: Pericytes and Microglia ; Neonatal rabbit ; Forebrain ; Golgi method ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Three types of pericytes outline the vascular bed in Golgi preparations of the newborn rabbit brain. Elongate cells (Type I) are restricted to capillaries, elements resembling smooth muscle cells (Type II) surround vessels of intermediate size, and large flat forms (Type III) cover the surface of arterioles and venules. Electron microscopy shows all types to be located within a well defined perivascular basement membrane. It also reveals the presence of filaments in the cytoplasm of some pericytes resembling the myofilaments of smooth muscle cells. It suggests the possibility that some pericytes are capable of contraction and may participate in regulating blood flow in small vessels. Microglia cells bear no resemblance to pericytes in terms of their shape, distribution or staining characteristics. Microglia cells are located outside the vascular basement membrane (external basal lamina) in the brain parenchyma, and they vary in form according to their location and the character of the surrounding extracellular space. This study does not support the hypothesis that microglia cells arise from pericytes but indicates that they originate either by in situ division or from hematogenous elements that enter the brain by crossing the vessel wall.
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  • 150
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    Cell & tissue research 159 (1975), S. 205-212 
    ISSN: 1432-0878
    Keywords: Microtubules ; Prolactin cells ; Anterior pituitary gland ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The intracellular distribution of microtubules was studied using serial sections of prolactin cells in anterior pituitary glands from lactating rats. Numerous microtubules were present in these cells following fixation with glutaraldehyde and osmium tetroxide. The greatest number of microtubules were present in the Golgi complex, situated around the perimeter and in association with the cisternae, vesicles and developing secretory granules. Microtubules were found in channels between groups of parallel cisternae of rough surfaced endoplasmic reticulum and in close proximity to small vesicles. They were also located adjacent to mitochondria, the plasmalemma, the nuclear envelope, and among mature secretory granules. Due to their orientation within the cell, it is suggested that the microtubules may act to direct the movement of organelles from one region of the cell to another and to give internal support to the cell.
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  • 151
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    Cell & tissue research 170 (1976), S. 549-551 
    ISSN: 1432-0878
    Keywords: Optic gland ; Octopus ; Uptake of ferritin ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Horse spleen ferritin, injected into the blood of the octopus, leaves the capillaries via pericyte junctions and windows. One hour after the administration, ferritin has entered the optic gland main cells; three hours later, it is accumulated in dense-bodies. The evidence for resorption supports earlier papers reporting that the ultrastructure of the organ is unusual for an endocrine gland.
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  • 152
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    Keywords: Rat posterior pituitary ; Neurophysin-vasopressinergic and neurophysin-oxytocinergic fibres ; Immunocytochemistry ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary By means of the unlabeled antibody peroxidase-antiperoxidase (PAP) technique at the electron microscopic level, it was demonstrated that the hormones of the neural lobe of the rat hypophysis are located in separate neurophysin-vasopressinergic and neurophysin-oxytocinergic nerve fibres. These observations confirm the results of our previous immunocytochemical studies at the light microscopic level.
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  • 153
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    Keywords: Intracisternal polycylinders ; Endoplasmic reticulum ; Arion empiricorum ; Electron microscopy
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    Notes: Summary Study of the digestive organs of the slug Arion empiricorum with the electron microscope has revealed cytoplasmic structures that we call intracisternal polycylinders (ICPC). They consist of cylinders of cytoplasm (about 550 Å in diameter) arranged in sheafs within cisterns of the endoplasmic reticulum. They appear in different cell types, being most common in the digestive epithelium of the midgut. Their morphology and apparent association with other cytoplasmic organelles such as mitochondria, peroxisomes, multivesicular and residual bodies suggests that the ICPC might be involved in exchange, transport and oxidation processes, contributing to the excretory function at a subcellular level.
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  • 154
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    Cell & tissue research 159 (1975), S. 445-457 
    ISSN: 1432-0878
    Keywords: Tentacles ; Coelenterata ; Cytology ; Microtubules, Cilia ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Calpasoma dactyloptera, a tentacled form of minute, freshwater coelenterate, has been investigated by light and electron microscopy and time-lapse cinematography. Each tentacle consists of a protrusion from a single ectodermal epithelial cell termed a tentaculocyte. hin tentaculocyte vesicles which represent invaginations of the plasma membrane. A cnidocil protrudes into the external medium. The bottom of each nematocyte is elongated as a stalk which extends to the tentacle base, coursing through tubular membrane lined channels within the tentaculocyte. A network of fibers and microtubules, originating in the cnidocil, extends to the base of the nematocyte stalk.
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  • 155
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    Cell & tissue research 160 (1975), S. 139-153 
    ISSN: 1432-0878
    Keywords: Arcuate nucleus, cat ; Dense-cored vesicles ; Dopamine ; 5-Hydroxydopamine treatment ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The arcuate nucleus of normal cats and of cats treated with 5-hydroxydopamine (5-OHDA) was investigated by electron microscopy. The neurons of the arcuate nucleus were classified into three types, clear, intermediate and dark, according to their fine structure. The clear type contained numerous dense-cored vesicles and well developed cell organelles. All three types were frequently seen to be partially surrounded by glial processes. Many axo-somatic and axo-dendritic synapses mostly small in diameter were also observed around the neurons. Synaptic contacts were demonstrated between axon endings and axonal processes which contained elementary granules. After administration of 5-OHDA small and large dense-cored vesicles appeared in the nerve endings surrounding the neurons. The relationship between the dense-cored vesicles in the perikarya and dopamine was briefly discussed.
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  • 156
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    Cell & tissue research 160 (1975), S. 177-191 
    ISSN: 1432-0878
    Keywords: Glomerulus ; Human and rat kidney ; Cell junctions ; Filtration barrier ; Electron microscopy ; Freeze-fracturing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Glomeruli isolated from rat and human kidneys were studied using the freeze fracture technique. Discontinuous zonulae occludentes and gap junctions were found in the replicas of the split plasma membrane of the endothelial cells. A diaphragm across the endothelial pores was not demonstrated. The central layer of the basement membrane, corresponding to the lamina densa described in thin sections, revealed a coarse substructure. A slit membrane between the pedicles of the podocytes was not detectable; however, its position was indicated by the different texture of the replica, which abruptly changed at the transition of the basement membrane to the primary urinary space. Furthermore, at the level of the slit membrane arrays of particles were present within the cleaved membrane of the pedicles, probably representing the attachment points of the slit membrane. Isolated strands of a zonula occludens as well as gap junctions were seen on the split plasma membrane of the podocytes. The mesangial cells could be identified by their contiguity to the endothelial cells and by their numerous gap junctions.
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  • 157
    ISSN: 1432-0878
    Keywords: Prothoracic gland cells ; Insect hormones ; Galleria mellonella (Lepidoptera) ; Electron microscopy
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    Topics: Biology , Medicine
    Notes: Summary The prothoracic glands of the last instar of Galleria mellonella undergo characteristic alterations of their cellular fine structure closely related to cellular activity. During progressive secretory activity of the gland cells there are extensive plasmalemmal infoldings and formation of a pronounced lacunar system. Mitochondria of the active cell phase are characterized by a specific increase in size and paler colour of the matrix. In contrast to the alterations, nuclei, ER and Golgi cisterns do not undergo any submicroscopic changes during the different phases of cellular activity. The relationships between the substructural phenomena and the specific phases of cellular activity are discussed.
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  • 158
    ISSN: 1432-0878
    Keywords: Tetrabenazine ; Noradrenaline ; Constricted nerves ; Noradrenaline depletion in vitro ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The accumulation of noradrenaline proximal to a constriction applied to cat hypogastric nerves in vitro has been studied in preparations treated with tetrabenazine. The accumulation of amine was almost completely abolished by the drug. Evidence is presented which suggests that tetrabenazine exerts a direct noradrenaline-depleting effect on the intraneuronal storage vesicles. Recovery of noradrenaline levels after the removal of the drug was rapid and was effected by the biosynthesis of new noradrenaline within the axon.
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  • 159
    ISSN: 1432-0878
    Keywords: Cholecystokinin-pancreozymin (CCK-PZ) ; Glycoprotein secretion ; Mouse gallbladder ; Exo-endocytosis ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Structural changes in the gallbladder epithelial cells of the mouse were studied following in vivo and in vitro stimulation of the gallbladder with the gastrointestinal hormone cholecystokinin-pancreozymin (CCK-PZ). Signs of increased secretory activity were observed within the first 2–3 min after hormone administration. At the ultrastructural level, best visualized with the PA-CrA-silver technique, granule discharge was observed, as was an overall increase in size of the granules. After prolonged in vitro incubation or repeated in vivo stimulation, there was an almost total depletion of secretory granules. This phenomenon is accompanied by an enhanced uptake of extracellular thorium dioxide by endocytotic vesicles at the apical cell surface. An exocytosisendocytosis coupling mechanism may be important for membrane conservation in the gallbladder epithelial cells. The findings establish that the hormone CCK-PZ stimulates the secretion of glycoproteins from the mouse gallbladder epithelium.
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  • 160
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    Cell & tissue research 161 (1975), S. 11-24 
    ISSN: 1432-0878
    Keywords: Median eminence ; Hypothalamo-hypophysial system ; Frog, Rana catesbeiana ; Electron microscopy
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    Notes: Summary The fine structure of the hypothalamic floor was studied in the frog, Rana catesbeiana. The regions slightly anterior and posterior to the swollen hypothalamic floor part, which has been classically designated as the median eminence, contained neurosecretory axon terminals abutting on the capillary walls. The region relatively far anterior to the swollen part did not show neurosecretory axons terminating on capillary walls. The neural stalk contiguous to the rostral border of the pars intermedia had few neurosecretory axon terminals which end on the terminal portions of the ependymal processes covering the capillary wall. The functional significance of the regional differentiation of the frog neurohypophysis is discussed in connection with the regional differentiation of various secretory cells in the adenohypophysis.
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  • 161
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    Cell & tissue research 161 (1975), S. 55-70 
    ISSN: 1432-0878
    Keywords: Human fetal testis ; Gonocytes ; Fetal spermatogonia ; Electron microscopy
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    Topics: Biology , Medicine
    Notes: Summary Electron microscopic studies of the testis were performed on 12 human embryos and fetuses between 9 and 30 weeks post conceptionem. According to their ultrastructural features, the fetal germ cells could be divided into the following three stages of differentiation: 1) gonocytes, 2) intermediate cells, and 3) fetal spermatogonia. Sertoli cells were present among the germ cells in all the testes studied. The gonocytes showed the highest nucleo-cytoplasmic ratio. Their round nucleus contained a centrally located, prominent nucleolus. The cytoplasm displayed a well developed Golgi apparatus, lipid droplets and parallel arrays of short cisternae of the rough surfaced endoplasmic reticulum (rER). Microfilaments were numerous, particularly just beneath the cell membrane. The intermediate cells were found to extend several cytoplasmic processes and to contain a moderate number of long, branched and/or widened rER cisternae which were frequently connected to the perinuclear cisterna. Intermediate cells were often connected to one another by intercellular cytoplasmic bridges. The fetal spermatogonia also displayed cytoplasmic bridges. These cells showed the lowest nucleo-cytoplasmic ratio and a more condensed nuclear chromatin. The mitochondria were situated close to the nucleus. Many of them were connected by a cementing substance. Lipid droplets and rER cisternae were rare in these cells. Infoldings of the inner nuclear membrane were often present in the gonocytes and in the intermediate cells, but were rarely observed in the fetal spermatogonia. Glycogen particles, polyribosomes, and chromatoid bodies (“nuage”) were present in all the three germ cell types. With the maturation of the fetus, the number of gonocytes was found to decrease, whereas the number of fetal spermatogonia increased. The Sertoli cells also changed their ultrastructure, showing an increase in the number of rER cisternae, as well as of microfilaments, lipid droplets, and secondary lysosomes.
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  • 162
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    Cell & tissue research 161 (1975), S. 103-117 
    ISSN: 1432-0878
    Keywords: Tissue culture ; Chromaffin cells ; Frog ; Classification ; Phase contrast microscopy ; Fluorescence microscopy ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Extra-adrenal chromaffin cells from adult frogs were grown in tissue culture and their morphology and behaviour observed with both light and electron microscopy. 2. Two types of chromaffin cells were distinguished: Type A cells contain large, electron dense vesicles (2000–6000 Å) and are equated to Type I chromaffin cells seen in vivo, i.e. they contain noradrenaline; Type B cells contain smaller vesicles (700–2000 Å) which are incompletely filled with an electron dense material and are equated to Type III chromaffin cells seen in vivo, i.e. cells depleted of their catecholamines by stimulation. No cells comparable to Types II and IV cells in vivo were seen. 3. Close associations between the cultured chromaffin cells and sympathetic neurons were observed with the light microscope, but no examples of synaptic structures were seen in the material examined with electron microscopy in this study.
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  • 163
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    Cell & tissue research 160 (1975), S. 515-524 
    ISSN: 1432-0878
    Keywords: Ureteric innervation ; Mammals ; Interspecies differences ; Electron microscopy
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    Topics: Biology , Medicine
    Notes: Summary The distribution and structure of the ureteric nerves in a small series of mammals was compared with that previously demonstrated in the rat. There was marked interspecies variation in the extent to which the nerves penetrated the wall of the ureter and in the degree of development of the deep submucous plexus. In animals with a highly developed deep submucous plexus, terminal arterioles frequently passed through the muscle coat before breaking up into capillaries. These vessels were surrounded by a fine periarteriolar plexus and were accompanied in their course through the muscle coat by one or more branches of the adventitial nerves. Intramuscular nerves not related to arterioles contained few axons with terminals classifiable as either adrenergic or cholinergic, and in animals in which the muscle cells were arranged in fascicles rather than in sheets, the nerves were typically interfascicular in position. As in the rat, only the periarteriolar plexuses contained large numbers of adrenergic axons. Cholinergic axons were generally few, but were not uncommon in the deep submucous plexus when this was well-developed. The majority of the terminals encountered in the intramural nerves contained variable and usually small numbers of both clear and large dense-cored vesicles. The relationship between these terminals and those defined in the submucous nerves of the rat ureter was discussed and it was suggested that the marked variations in the diameter of the axons in the terminal areas and in the number of vesicles in the terminals were related to the effects of the mechanical and other derangements which occur during processing.
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  • 164
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    Keywords: Capillary endothelium ; (Retina) ; Tight junction artefact ; Sodium ions ; Streptozotocin ; Diabetes ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Retinal capillary junctions were analysed in normal and diabetic rats and in a human retina with the electron microscope. Diabetes mellitus was induced with Streptozotocin. The retinae were fixed in Palade's osmium tetroxide containing sodium or calcium ions and block-stained in uranyl acetate. With Ca-fixation, no significant difference in interendothelial cleft width was detected between retinal layers or between normal and diabetic retinae. Diabetes caused a narrowing of the clefts in the Na-fixed tissue (X±SE, n=375; Normal: 78.6±3.00 Å; Diabetic: 57.7 ±2.42 Å; p≪0.001). A significant correlation was found between cleft width and the length of the tight junctions or zonulae occludentes (p〈0.001). In the nerve fibre layer of the Nadiabetio retina, where cleft narrowing was greatest, there was an increase in length of the zonulae occludentes from 22.8±2.2% to 41.6±3.7% (p〈0.001). Ca-fixation prevented these changes, indicating that at least some zonulae occludentes were interendothelial extraction artefacts. In the normal retina, endothelial cell membrane thickness was greater with Ca-than Na-fixation (p〈0.001). Diabetes caused a decrease in membrane thickness of Ca-fixed tissue (p〈0.001). The diabetic decrease in membrane thickness may explain the increased fragility and increased permeability of diabetic capillaries. Calcium binding by endothelial cell membranes is of primary importance in anticoagulation which is defective in diabetes.
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  • 165
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    Cell & tissue research 161 (1975), S. 421-430 
    ISSN: 1432-0878
    Keywords: Sensory cilia ; Retinal rods (rat) ; Comparison with kinocilia ; Freeze fracture ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The connecting cilium of rat retinal rods was studied by freeze-fracture and thin-sectioning techniques. Transverse strands of intramembranous particles could be observed on fracture face B of the ciliary plasma membrane. The strands were essentially similar to those found at the transitional zone of motile cilia (“ciliary necklace”). The large number of intramembranous particles obscured the pattern on fracture face A of the membrane. On longitudinal sections of the cilia, beads showing a periodicity similar to the necklace strands were observed. Each bead consisted of two structures apposed to both sides of the plasma membrane. Transverse sections of the cilia revealed radial Y-shaped structures that connected each ciliary doublet with the plasma membrane. Axial tubules, central sheath, radial spokes and dynein arms were missing in the connecting cilium. Comparing the fine structure of the retinal cilia with that of motile cilia it becomes evident that the connecting cilium is analogous in structure with the transitional zone of motile cilia. The present observations suggest that periodic membrane beads along the plasma membrane on thin sections correspond to strands of necklace particles as observed on freeze-fractured membranes. The arrangement of the particles in transverse strands is probably ensured by the radial connecting structures.
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  • 166
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    Cell & tissue research 161 (1975), S. 485-495 
    ISSN: 1432-0878
    Keywords: Intestinal epithelium ; Mucosal immunity ; Chicken ; Electron microscopy
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    Topics: Biology , Medicine
    Notes: Summary The intraepithelial lymphoid cells of chicken small intestine were studied by light microscopy using 1 μ Epon sections, and by electron microscopy. Three cell types were found: small lymphocytes, large lymphoid cells, and granular cells. These cells correspond to the theliolymphocytes and globule leucocytes of previous authors. The numbers of all cell types increased with age. Correlation was found between the number of small lymphocytes and large lymphoid cells, but not between granular cells and either of the other two. A hypothesis is proposed, assigning these cells with a function in mucosal immunity.
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  • 167
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    Cell & tissue research 162 (1975), S. 107-118 
    ISSN: 1432-0878
    Keywords: Basal disk ; Gastrodermis ; Mesoglea ; Hydra ; Electron microscopy
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    Topics: Biology , Medicine
    Notes: Summary The gastrodermis and mesoglea of the basal disk of Hydra were investigated to conclude a three-part series of papers. The gastrodermis is composed of digestive cells (most predominant cell type), mucous and nerve cells (both immature and fully differentiated). The principal function of the digestive cells appears to be storage of protein, lipid and glycogen reserves which are utilized by neighboring cells. Mucous cells apparently use some of the reserves to synthesize their secretions which lubricate cells and prevent cell damage during egestion of waste through the aboral pore. The function of the gastrodermal nerve cells is uncertain. The mesoglea of the basal disk, contains the same structural components as seen in other regions of the polyp. It is reasonable to assume that it maintains the same function of cell adhesion and migration. As the mesoglea converges on the aboral pore, it loses its structural integrity and cells are sloughed off the column.
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  • 168
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    Cell & tissue research 162 (1975), S. 357-365 
    ISSN: 1432-0878
    Keywords: Catfish ; Endocrine pancreas ; Cell types ; Innervation ; Electron microscopy
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    Topics: Biology , Medicine
    Notes: Summary The endocrine pancreas of the bullhead catfish, Ictalurus nebulosus, and the channel catfish, I. punctatas was studied by light and electron microscopy. In addition to the usual A, B and D cells, a fourth endocrine cell type was consistently observed in the electron microscope. All endocrine cell types were innervated. The vesicles of most of the nerve endings were ultrastructurally different from typical adrenergic and cholinergic vesicles, strongly suggesting the possibility of a third autonomic neurotransmitter serving as a regulator of catfish islet secretion.
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  • 169
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    Cell & tissue research 162 (1975), S. 411-417 
    ISSN: 1432-0878
    Keywords: Subradular organ ; Lepidochitona cinereus ; Cell types ; Chemoreception ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Summary Electron microscopy of the subradular organ of the chiton Lepidochitona cinereus (L) reveals at least three cell types, microvillous, ciliated and mucus-secreting, situated in a single epithelium. The base of the epithelium is abundantly innervated and supplied with muscle cells. The fine structure is consistent with a chemosensory function for the subradular organ.
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  • 170
    ISSN: 1432-0878
    Keywords: Ultimobranchial body ; Parathyroid gland ; Amphibia ; Gymnophiona ; Innervation ; Electron microscopy ; Histochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Fine structural and enzyme histochemical observations on ultimobranchial body and parathyroid gland of the caecilian Chthonerpeton are presented. The cell clusters and follicles of the ultimobranchial body consist mainly of granulated cells which are termed C-cells and obviously belong to the APUD cell series. In the larger follicles additional possibly exhausted degranulated cells and replacement cells occur. A rich supply of nerve fibres has been found in this gland. Frequently nerve terminals were observed to come into synaptic contact with the C-cells. Two categories of nerve fibres occur: a) fibres containing large polymorphic electron dense granules (probably purinergic fibres), b) fibres containing small electron transparent vesicles and a few electron dense granules (probably cholinergic fibres). The parathyroid gland consists of elongated cells (one cell type) poor in organelles and often containing fields of glycogen and lipid droplets. The cells are further characterized by fair amounts of lysosomal enzymes; they are interconnected by maculae adhaerentes and occludentes. No nerves and blood vessels have been found in the parathyroid gland of Chthonerpeton.
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  • 171
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    Cell & tissue research 164 (1975), S. 133-144 
    ISSN: 1432-0878
    Keywords: Bladder body ; Mammals ; Musculature ; Innervation ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The distribution and structure of the nerves supplying the muscle of the body of the bladder in mammals such as the mouse, guinea-pig, rabbit, cat and dog was compared with that previously demonstrated in the rat. The muscle of the arterioles located between the muscle bundles is innervated by a fine perivascular plexus and the nerves forming the muscular plexus can be divided into inter-and intra-fascicular components. Terminals containing variable but usually small numbers of clear and large dense-cored vesicles are particularly numerous in the interfascicular nerves and the intrafascicular nerves are characterised by large numbers of terminals with the features of those of cholinergic axons. In addition to many small clear vesicles, the cholinergic terminals contained some small dense-cored vesicles, and it is suggested that, as in the rat, these contain a second transmitter which is released with acetylcholine at the terminals during impulse transmission. Adrenergic terminals are more common in the muscular plexuses of the guinea-pig, dog and cat than in those of the other animals studied and there is evidence for the presence of two types of such terminal in the nerves. Of these, one contains a much smaller proportion of small vesicles with dense cores and many more large dense-cored vesicles than the second, and the possibility of a relationship between such terminals and those of short adrenergic neurones and neurones associated with non-adrenergic patterns of impulse transmission is discussed.
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    Cell & tissue research 164 (1975), S. 201-213 
    ISSN: 1432-0878
    Keywords: Kidney ; Myxine glutinosa ; Cell junctions ; Electron microscopy ; Freeze-fracturing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fine structure of the kidney (glomerulus and archinephric duct) of the hagfish, Myxine glutinosa (L.) was studied in thin sections and by freeze-fracture technique. The glomerular filtration barrier is similar to that of mammalian kidneys. However, endothelial fenestrations are relatively scanty and the basement membranes of endothelial cells and podocytes always appear separated by a layer of collagen fibrils and microfibrils often surrounding numerous and extended mesangial cells. Between podocytes and their processes maculae occludentes and peculiar junctions of another type occur. The zonulae occludentes between epithelial cells of the archinephric duct are composed of five or more strands, occasionally of only one or two. Supported in part by Deutsche Forschungsgemeinschaft (SFB 146, STO B4) and NIH (ISOI-RR 05764).
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    Cell & tissue research 164 (1975), S. 261-269 
    ISSN: 1432-0878
    Keywords: Pancreatic B cell ; Microtubules ; Secretory Process ; Electron microscopy
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    Topics: Biology , Medicine
    Notes: Summary The distribution of microtubules has been studied in pancreatic B cells of normal rats and in animals infused with glucose for various periods of time. An array of microtubules extends from the outer nuclear membrane to the plasma membrane coursing in all directions of the cytoplasmic space. Microtubules are found between profiles of the endoplasmic reticulum, cisternae of the Golgi complex and in close proximity to mitochondria and secretion granules. Insertion of microtubules in the plasma membrane is best studied in tangential sections through the plane of the membrane, the fixation of microtubules might involve microfilaments and desmosomes. The possible role of microtubules in the different phases of the secretory process is discussed.
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    Cell & tissue research 164 (1975), S. 309-329 
    ISSN: 1432-0878
    Keywords: Central nervous system ; Leptomeningeal tissue ; Junctions ; Blood-brain barrier ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The leptomeningeal tissue of the choroid plexuses and of the brain surfaces have been studied by means of the freeze-etching technique. The pia-arachnoid membrane and the subdural neurothel represent the morphological barrier between the extracerebral tissue and the cerebrospinal compartment. The freeze-etch findings indicate that the arachnoid and neurothelial cells are coupled by extensive zonulae occludentes which seem to represent the structural basis of the barrier mechanism provided by these cell layers. Furthermore, it became evident that gap junctions of considerable structural heterogeneity occur on the pial and arachnoid cells of the interstitial choroidal compartment and of the free brain surfaces. The structural heterogeneity of the nexuses is taken as an indication of the plasticity of the leptomeningeal tissue. The different morphological characteristics of the nexal formations are discussed with respect to their probable functional meaning.
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  • 175
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    Keywords: Median eminence ; Rat ; Monoamine ; ZIO reaction ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Summary The reaction of nerve endings in the median eminence of the rat to zinc iodide-osmium tetroxide (ZIO) staining was examined electron microscopically under normal and experimental conditions. The experimental condition of catecholamine exhaustion in the nerve endings was induced by the administration of H44/68 and reserpine. Vesicles in the terminals of catecholaminergic nerves reacted similarly to ZIO staining in both normal and experimental material. The majority of synaptic vesicles in various terminals gave a positive ZIO reaction. The neurosecretory elementary granules, however, failed to react with ZIO. On the other hand, some nerve terminals in the external layer of the median eminence showed a strong positive reaction in the cytoplasmic matrix, in mitochondria as well as in synaptic vesicles. These findings strongly suggest that the ZIO-positive substance in nerve terminals is not the transmitter itself, i.e. the monoamine, but rather represents a range of substances commonly found in various kinds of synaptic vesicles and is probably proteinaceous in nature. A brief discussion is also given on the difference in ZIO reactivity between neurosecretory elementary granules and small vesicles in the hypothalamo-hypophyseal tract.
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    Cell & tissue research 165 (1976), S. 141-156 
    ISSN: 1432-0878
    Keywords: Basilar papilla ; Lizard (Calotes versicolor) ; Innervation ; Sensory cells ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The basilar papilla of the lizard Calotes versicolor contains about 225 sensory cells. These are of two types: the short-haired type A cells in the ventral (apical) part of the organ, and the type B cells with long hair bundles, in the dorsal (basal) part of the organ. The type A cells are unidirectionally oriented and are covered by a tectorial membrane while the type B cells lack a covering structure and their hair bundles are oriented bidirectionally. Apart from those differences, the type A and type B cells are similar. They are columnar, and display the features common to most sensory cells in inner ear epithelia. The sensory cells are separated by supporting cells, which have long slender processes that keep the sensory cells apart. Close to the surface of the basilar papilla a “terminal bar” of specialized junctions interlocks adjacent cells. Below this, adjacent supporting cells are linked by an occluding junction. The cochlear nerve enters from the medial (neural) aspect. The fibres of the nerve lose their myelin sheaths as they enter the basilar papilla. Each sensory cell is associated with several nerve endings. All the nerves identified were afferent. Marked variations were seen between nerve endings in the basilar papilla, but no morphological equivalents of any functional differences were observed.
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  • 177
    ISSN: 1432-0878
    Keywords: Thyroid gland ; Temperature-dependent changes ; Electron microscopy ; Histochemistry ; Thyroxine, triiodothyronine ; Amphibia, Gymnophiona
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The thyroid gland of the tropical amphibian Chthonerpeton is markedly stimulated when the animal is exposed for two days to relatively high temperatures (36° C). Control animals were kept at 20° C. The stimulated gland exhibits collapsed follicles and a very tall follicular epithelium. At the ultrastructural level the activated epithelial cells were characterized by an increased number of apical microvilli, increased amounts of rough endoplasmic reticulum, an extended Golgi apparatus and a high number of various granular and vesicular inclusions. These differences in histology and fine structure were not paralleled by quantitative results, which were approximately the same in both groups of animals. The values of these determinations were relatively high.
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    Cell & tissue research 165 (1976), S. 467-475 
    ISSN: 1432-0878
    Keywords: Thyroid gland ; Temperature-dependent changes ; Thyroxine ; Electron microscopy ; Amphibia, Urodela
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The influence of temperature on the thyroid gland of the Caucasian salamander, Mertensiella caucasica has been studied (1) with the light- and electron microscopes, (2) with enzyme histochemical and quantitative methods. Animals which had been kept for years at 16° C were exposed for 48 hrs to 4° C or 27° C. At 4° C the follicular epithelium consisted of cuboidal cells with well-developed rough ER, occasional distended cisternae of the rough endoplasmic reticulum (ER) filling most of the cytoplasm, a relatively small Golgi apparatus and numerous round or oval shaped lysosomes. In animals kept at 27° C the follicular wall was composed of markedly taller epithelial cells, the apices of which bulged into the follicular lumen. Compared to the animals at 4° C, there appeared to be a decrease in the rough ER. The Golgi apparatus did not exhibit clear differences. The lysosomes increased in number and showed various shapes among which elongated ones with pointed ends were particularly striking. In the apical cytoplasm colloid droplets appeared indicating hormone release. The apical microvilli increased in number. The measurements of total T4 have shown that the hormone level in animals kept at 27° C was about twice as high as in animals kept at 4° C.
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  • 179
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    Cell & tissue research 165 (1976), S. 545-553 
    ISSN: 1432-0878
    Keywords: Neurophysine-containing vesicles ; Neurosecretory system ; Vertebrates ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A new method described in the present paper allows identification of neurophysine-containing (NP) vesicles of the magnocellular neurosecretory system of vertebrates. After oxidation of ultrathin sections, the content of NP vesicles can be dissolved specifically in an alkaline medium. This procedure marks NP vesicles selectively in all portions of the classical neurosecretory system.
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  • 180
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    Cell & tissue research 175 (1976), S. 1-15 
    ISSN: 1432-0878
    Keywords: Rete testis ; Human ; Epithelial cell types ; Smooth muscle cells ; Histophysiology ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructure of the normal human rete testis was analyzed. The rete testis cavities are irregularly shaped and contain virtually no spermatozoa. Smooth muscle cells often surround the cavities. In the epithelial lining, two cell types are distinguishable. Flat, dark cells exhibit numerous slender microvilli, and numerous apical and basal microvesicles. Prismatic, lighter cells have more cell organelles, mostly polarized towards a supranuclear position. Both cell types contain variable amounts of glycogen and fat, and an occasional cilium. All cells display intricate lateral cell surfaces that possess different cell-to-cell attachment devices. Intermediate cell types are frequently found. On a morphological basis, the epithelial cells seem to be involved in the release of substances into the lumen and probably also in transport towards the base. Connective tissue elements are found subjacent to the epithelium. Scattered among the fibrocytes are typical smooth muscle cells. Expansions of some smooth muscle cells are connected to the epithelial basement membrane by a network of microfibrillar material. The smooth muscle cells may be involved in changing the shape of the rete testis channels, thus promoting the flux of the rete testis fluid. Different types of nerve fibre bundles are distinguished in the connective tissue of the rete testis which may correspond to autonomic and sensory nerves or sensory receptors.
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  • 181
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    Cell & tissue research 175 (1976), S. 59-72 
    ISSN: 1432-0878
    Keywords: Retina ; Xenopus ; Rods ; Cones ; Hemicholinium-3 ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Hemicholinium-3 (HC-3), a drug which prevents synthesis of acetylcholine in neurons, when injected intraperitoneally in doses as low as 2×5 mg/kg produces marked ultrastructural changes and damage in rod but not in cone photoreceptors. In rods it causes a reduction in cytoplasmic back-ground density, swelling of the endoplasmic reticulum, ballooning of the outer membrane of the nucleus, leaching of the nucleoplasm and clumping of the nuclear chromatin. In dark-adapted rods HC-3 produces some loss of cytoplasmic synaptic vesicles but no reduction in numbers of those vesicles which lie adjacent to the synaptic ribbons. In light-adapted rods the drug does not cause such an apparent reduction of synaptic vesicles but does induce a considerable reduction in numbers of vesicles associated with the ribbons. These structural changes are discussed in the light of what is known about the pharmacology of HC-3 and neurotransmitter release from vertebrate photoreceptors.
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  • 182
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    Cell & tissue research 166 (1976), S. 219-234 
    ISSN: 1432-0878
    Keywords: Electron microscopy ; Byssus ; Collagen ; Mytilus galloprovincialis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructure of the byssus of Mytilus galloprovincialis was analysed by transmission electron microscopy in thin sections of either embedded or frozen samples. All parts of the byssus (stem core laminae, stem outer laminae, threads proximal and distal parts) appear to be formed by the same basic filamentous components organized in different ways at the submicroscopic level and embedded in a variable quantity of matrix. The filaments appear to consist of a central electron-lucent zone (3 nm in diameter), surrounded by an electron-dense rim (total diameter 7 nm). The matrix has a granular or microfilamentous structure. The stem and the threads differ greatly in their submicroscopic organization, but their basic constituents (filaments and matrix) are similar. Peculiar filamentous banded elements (FBE) were found mainly in the stem outer laminae. A relation between the ultrastructure and mechanical properties of the different parts of the byssus was established. The presence of collagen is discussed; since no morphological evidence of any of the known forms of collagen organization was revealed by electron microscopy, it is suggested that byssus collagen may be localized in the matrix and in the FBE.
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  • 183
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    Cell & tissue research 166 (1976), S. 235-240 
    ISSN: 1432-0878
    Keywords: Pituitary ; Pars distalis ; Chromophobe ; Reptile ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Chromophobes of the pars distalis in young Chelydra serpentina have sparse cytoplasm with no specific granules; however, many cytoplasmic filaments are present. The chromophobes are connected to the other cell types by desmosomes, while different types of junctional specializations occur between adjacent chromophobes. Cytoplasmic filaments traverse the cytoplasm in a random manner and terminate on both the junctional complexes and the nuclear envelope. It is proposed that, in addition to providing a structural framework, the chromophobes may be involved in integrating cellular responses of the parenchyma to changes in the endocrine milieu.
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  • 184
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    Keywords: Muscle ; Diabetes mellitus ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructure of fast-twitch-oxidative-glycolytic (FOG), fasttwitch-glycolytic (FG) and slow-twitch-oxidative (SO) fibers in plantaris and soleus muscles of normal and streptozotocin-diabetic rats was studied. In the diabetic animals, the mitochondria of FOG and SO fibers showed a loss of cristae and an increase in electron-dense granules. There was also an increased number of lipid droplets in close proximity to the mitochondria and the nuclei, and a separation of individual muscle nuclei to form satellite cells. Higher incidences of surface projections and sarcoplasmic splittings at the nuclear region were noticed in SO fibers. The FG fibers showed some disorientation of the T-tubular system. It is concluded that streptozotocin-diabetes has differential effects on the fine structure of the three fiber types of rat skeletal muscle.
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  • 185
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    Cell & tissue research 166 (1976), S. 489-496 
    ISSN: 1432-0878
    Keywords: Cerebellar cortex (Rhesus monkey, cat) ; Supraganglionic plexus ; Myelinated parallel fibers ; Regional distribution ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In the cerebellar cortex of the Rhesus monkey and the cat, the supraganglionic plexus in the molecular layer exhibits regional differences. The plexus is very well developed in the vermal parts of the anterior lobe, but only poorly developed in the nodulofloccular lobe. Most of the fibers of this plexus are myelinated parallel fibers, which synapse in the typical manner with dendritic thorns of Purkinje cells. Only very few fibers of this plexus are recurrent collaterals of Purkinje cells. Their distribution throughout the cerebellar cortex does not display regional differences. These findings agree with physiological data on the disinhibition of Purkinje cells in different parts of the cerebellar cortex.
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  • 186
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    Cell & tissue research 166 (1976), S. 521-530 
    ISSN: 1432-0878
    Keywords: Ependyma ; Fish ; Third ventricle ; Hypothalamus ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ependyma lining the lateral recess of the third ventricle of the teleost inferior lobe has been studied by light and electron microscopy, including Golgi impregnation methods. As many as five different cell types appear to line the ventricle, but some of these may be similar cells in different stages of activity. One cell type contains small dense-cored vesicles and appears to have processes extending into deeper portions of the lobe. Golgi preparations reveal subependymal cells with apical processes extending to the ventricle and basal extensions which may reach the pial surface. The present observations are discussed in relation to similar studies in other fishes, amphibians and mammals. Possible functions for the various cells observed are suggested.
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  • 187
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    Cell & tissue research 169 (1976), S. 233-245 
    ISSN: 1432-0878
    Keywords: Isocortex (Man) ; Non-pyramidal cells ; Interneurons ; Lipofuscin pigment ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary With the aid of a newly developed technique for the successive examination of both the Golgi and pigment picture of individual neurons (Braak, 1974a) Braak (1974b) demonstrated that within lamina II and upper lamina III of the human isocortex, heavily pigmented non-pyramidal cells are distributed irregularly and sparsely. The lipofuscin pigment granules serve as excellent internal markers to identify these non-pyramidal cells in ultrathin sections. This favourable circumstance facilitates the study of these interneurons in the electron microscope. The heavily pigmented non-pyramidal cells are small, spherical to ovoid with diameters of about 12–15 μm. One pole of the cell comprising a large cytoplasmic area gives rise to a few dendrites, while the other pole is occupied by the nucleus and in some cases is in close apposition to another nerve cell body. The nucleus is deeply invaginated by the large cytoplasmic area and occasionally displays nuclear inclusions. Among the usual organelles distributed within the large cytoplasmic area the mitochondria with a moderately electron dense matrix are abundant and the coarse lipofuscin pigment granules are the most striking elements. The latter contain densely packed filamentous or tubular material and a single vacuole. The perikaryon rarely receives more than 3 type I and type II synapses per section per cell, whereas the dendrites receive numerous synapses of both type I and type II. Within the apposition zone to another nerve cell body (which in no case is a heavily pigmented non-pyramidal cell) puncta adhaerentia occur and also contacts in which the cleft of 8 nm is intersected by a dense stratum. Some of the ultrastructural findings are summarized in the schematic drawing of Figure 15.
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  • 188
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    Cell & tissue research 169 (1976), S. 395-403 
    ISSN: 1432-0878
    Keywords: Taste buds ; Fishes ; Electron microscopy ; Nucleolus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Taste buds occur in the epithelium of the catfish barbel along its entire length. Two major cell types, light and dark cells, occupy the upper two-thirds of the taste bud. A third cell type, the basal cell, lies on the basal lamina and is essentially separated from the light and dark cells by a plexus of unmyelinated nerve fibers. The dark cells have branching processes, both apically and basally whereas the light cells have a single apical process and many basal processes. The apical processes of dark cells contain secretory granules, while the apical processes of light cells contain an abundant agranular endoplasmic reticulum. Light cell nuclei contain bundles of 10 nm filaments, often arranged in the shape of a cup or ring, but nucleoli are rarely seen. It is suggested that this morphology indicates a low degree of RNA synthesis by light cells. The basal cells contain large numbers of vesicles, about 60 nm in diameter, which are sometimes seen in clumps in relation to an adjacent nerve fiber in a configuration resembling a synapse. Curiously, although basal cells present a large surface to the basal lamina, there are no hemidesmosomes. This suggests that the basal cell does not originate from the epidermis.
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  • 189
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    Cell & tissue research 176 (1977), S. 407-416 
    ISSN: 1432-0878
    Keywords: Chick embryo ; Electron microscopy ; Glial differentiation ; Neuron differentiation ; Reaggregation cultures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Dissociation and reaggregation cultures from different portions of the chick embryo neural tube were made, and the resulting aggregates were fixed for electron microscopy after 1, 5, 8, 14, 16 and 22 days in vitro. All cultures (pure aggregates of telencephalon, optic lobe or neural retina, and combined aggregates made from mixtures of optic lobe plus neural retina or optic lobe plus telencephalon) show a common timing of neuronal and glial morphological differentiation. During the first week in vitro, some cells developed neuronal characteristics in the absence of morphological evidence of glial differentiation. Numerous axonic processes usually formed fascicles with all the fibers running parallel to each other. Axonic growth cones were abundant and a few immature synapses were also present. The second week in culture was characterized by the disappearance of growth cones and the increase in number and morphological maturation of synapses. Morphologically detectable glial differentiation began by the end of this week, and during the third week almost every neuronal element, including the axonic fascicles, became associated with glial cells showing astrocytic features.
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  • 190
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    Keywords: Gastric mucous cells ; Differentiation ; 3H-thymidine incorporation ; Histochemistry ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Gastric surface mucous cells (SMC), mucous neck cells (MNC) and their undifferentiated and immature precursors were studied by light and electron microscopic histochemistry. The secretory granules of SMC were smaller, more electron dense and more reactive to PAS and its analogues than those of MNC. Alcian blue demonstrated that the mucus of SMC was acidic and that of MNC was neutral. The periodic acid —thiocarbohydrazide —silver proteinate method revealed the presence of carbohydrates in the Golgi apparatus, condensing vacuoles, secretory granules, apical vesicles and tubules and cell coat. Maturation of SMC during their migration towards the free surface was reflected by an increase in size and number of secretory granules, an increase of RER and microfilaments, and a decrease of microvilli and apical vesicles and tubules. The secretory granules of older SMC were less acidic and possessed a proteinaceous core. Most MNC were fully differentiated, but some immature MNC containing only a few granules were found. Furthermore, undifferentiated cells and intermediates between SMC and MNC were also observed. The presence of both transitional and intermediate forms indicates that both SMC and MNC arise from the same population of undifferentiated cells. Incorporation of 3H-thymidine revealed that undifferentiated cells, isthmic SMC, MNC and intermediate cells are proliferative. No proliferative activity was found in foveolar SMC, parietal, chief, fibrillovesicular or endocrine cells.
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  • 191
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    Cell & tissue research 168 (1976), S. 247-259 
    ISSN: 1432-0878
    Keywords: Tendons ; Connective tissue ; Collagen ; Human ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A variety of human tendons have been studied at the electron microscope level. The fibers of these tendons are composed of collagen fibrils that average 1,750 Å and 600 Å in diameter. A third population that measures 100 Å in diameter may represent immature collagen or filaments that are incorporated into tendon elastic fibers. The larger collagen fibrils vary in ratio with respect to one another, and are connected by interfibrillar bridges which in some cases appear to extend through the substance of the fibril. The collagen fibrils of the paratenon are less-well organized than those of the tendon proper and average 600 Å in diameter. Tendons that exhibit the property of lateral stretch (plantaris and palmaris) were compared at the ultrastructural level with tendons that do not have this property. No differences between the two tendon types could be determined in normal or spread preparations, indicating that the differences in physical characteristics are a result of fiber rather than fibril organization.
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  • 192
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    Cell & tissue research 168 (1976), S. 271-275 
    ISSN: 1432-0878
    Keywords: Corpus vitreum, ox ; Central part ; Ruthenium-red ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The central part of the corpus vitreum in the ox possesses a relative firmness. Electron microscopically it has been shown to consist of collagen fibrils with interfibrillar spaces containing 8 nm thick granules. The granules are made up of chains of macromolecules (hyaluronic acid in an oligomer state) 130–200 nm in length and of an oval shape. The collagen fibrils are tightly covered with 8.5 nm thick macromolecules which represent highly polymerized hyaluronic acid. These macromolecules can be stained with ruthenium-red.
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    Cell & tissue research 168 (1976), S. 507-525 
    ISSN: 1432-0878
    Keywords: Lymph node microvasculature ; Ultrastructure ; Permeability ; Horseradish peroxidase ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The microvasculature of lymph nodes and Peyer's patches consists of arterioles, capillaries and venules. The postcapillary segment comprises high-endothelial venules (HE venules) as well as ordinary venules. In order to study the ultrastructure of the microvasculature, particularly with respect to the nature of intercellular junctions, lanthanum and ruthenium red were used as tracers. Furthermore, to evaluate the permeability properties of the different segments of the microvasculature, intravenously injected horseradish peroxidase (HRP; MW: 40,000) was used. All segments of the microvasculature are permeable to HRP. However, the mechanism of transport across the vascular wall varies in the different segments, apparently correlated with a gradual decrease in number of transport vesicles and a gradual attenuation in the sealing of the endothelial cells. Tight junctions are present in arterioles, and it is assumed that HRP reach the basal lamina exclusively by vesicular transport. Incomplete or focal tight junctions are present in the capillaries, and both intercellular and vesicular pathways are observed. In the venules the intercellular pathway seems to be the dominant one, while vesicular transfer is negligible. However, some micropinocytic vesicles in the HE venule endothelial cells probably represent the initial stage of an intracellular digestion.
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  • 194
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    Keywords: Graafian follicle (Rabbit) ; Ovulation ; Ovarian surface epithelium ; Lysosomes ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fine structure of the surface epithelium over preovulatory rabbit follicles was examined parallel with visualization of acid phosphatase at the electron microscopical level. Small enzyme positive vesicles were pinched off from the Golgi cisternae and similar vesicles fused and got incorporated into larger lysosomes of dense body type. Some lysosomes appeared in direct continuity with tubular enzyme positive structures. Other possible ways of increase of the lysosomal pool are indicated and discussed. As in previous studies a maximal accumulation of lysosomes was found in the apical epithelium at 8 h after an ovulatory dose of human chorionic gonadotrophin (HCG); thereafter a gradual loss of lysosomes ensued. Before the lysosomes disappeared from the surface epithelium they changed in character. They became more electron-lucent and revealed a fine-fibrillar matrix. Dense bodies deep in the cell interior appeared to communicate with each other and with the extracellular space below the surface epithelium. Openings were never seen towards the peritoneal cavity. The loss of lysosomal content from the apical surface epithelium before follicle rupture appeared in many respects similar to the histamine release process in mast cells. The findings support our working hypothesis that the surface epithelium over Graafian follicles is an essential source of proteolytic enzymes and that these may be released extracellularly and actively contribute to the dissolution of the follicular apex before rupture.
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  • 195
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    Keywords: Luteinizing hormone-releasing hormone ; Median eminence ; Electron microscopy ; Immunocytochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary LH-RH was localized at the ultrastructural level in axons and nerve terminals of the median eminence of the male guinea pig. LH-RH positive neuronal profiles were most concentrated in the medial-dorsal aspect of the infundibular stalk and in the post-infundibular median eminence at the level immediately following separation of the stalk from the base of the brain. LH-RH containing axon profiles were most abundant in the palisade zone; nerve terminals in contact with the hypophysial portal vasculature were relatively rare. The hormone was present within granules that measured 900–1,200 Å in axons of the palisade zone and 400–800 Å in nerve terminals abutting on the portal plexus. The differently sized granules represent heterogeneous populations.
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    Cell & tissue research 169 (1976), S. 323-334 
    ISSN: 1432-0878
    Keywords: Babesia ; Merozoite ; Mechanism of invasion ; Role of host and parasite ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Intracellular sporozoan parasites invade the host cell through the invagination of the plasma membrane of the host and a vacuole is formed which accommodates the entering parasite. The vacuole may disappear and the invaginated membrane of the host then becomes closely apposed to that of the parasite's own membrane. As a result the parasite is covered by two membranes. Members of the class Piroplasmea differ from other Sporozoa in that their trophozoites are covered by a single membrane. By screening numerous sections of intraerythrocytic Babesia microti belonging to the class Piroplasmea, it was found that merozoites of Babesia enter the erythrocytes of hamsters in the same way as those of other Sporozoa. When a merozoite touches the red blood cell with its anterior end it becomes attached to the membrane of the host, which starts to invaginate and a parasitophorous vacuole is formed. The vacuolar space disappears rapidly and the membrane of the vacuole and that of the parasite become closely adjacent. At this stage the parasite is surrounded by two plasma membranes. The outer membrane derived from the invaginated host membrane disintegrates quickly and the parasite is left with a single membrane throughout its life span.
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    Cell & tissue research 169 (1976), S. 415-418 
    ISSN: 1432-0878
    Keywords: Synovial membrane (Cat) ; Free nerve endings ; Pacinian corpuscles ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Results of investigations on the occurrence of nerve fibres and endings in the synovial membrane of the knee and elbow joint in the cat are reported. The stratum synoviale contains only autonomic fibres, running in the adventitia of arteries. Free nerve endings are lacking in the stratum synoviale. Simple Pacinian corpuscles with an inner core are occasionally observed in the border zone between the stratum synoviale and fibrosum. The ultrastructure of these endorgans resembles that of Pacinian corpuscles in the hairless and hairy skin of the cat.
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    Cell & tissue research 169 (1976), S. 515-529 
    ISSN: 1432-0878
    Keywords: Graafian follicle (sheep) ; Atresia ; Ovum ; Capillaries ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The structural changes that characterize primary, secondary and tertiary atresia in sheep Graafian follicles have been studied by means of histological, histochemical and ultrastructural techniques. In primary atresia vacuoles representing swollen endoplasmic reticulum are prominent along the antral border together with disorganized granulosa cells containing pyknotic nuclei. Phagocytic cells, which increase in number as atresia progresses, were seen within the membrana granulosa and are considered to be transformed granulosa cells. Even in follicles classified as nonatretic, a few antral vacuoles and occasional pyknotic nuclei are present. During secondary atresia there is a large increase in the number of cells with pyknotic nuclei; many of these nuclei had been extruded and had fused to form the characteristic Feulgen-positive atretic bodies found along the edge of the antral cavity. These bodies usually have a diameter of up to 15 μm but occasionally reached as much as 400 μm. A second area of degeneration is frequently present in the membrana granulosa, two or three cell layers from the basal lamina, and it is at this level that exfoliation of granulosa cells occurs in tertiary atresia. In contrast to the membrana granulosa, there are during secondary atresia, only slight indications of degeneration in the cumulus. In tertiary atresia the membrana granulosa is highly disorganized; the atretic bodies are often fewer in number than at earlier stages. The basal lamina remains essentially intact. It is at this stage that the first clear signs of degeneration occur in the theca interna. Despite some disintegration of the cumulus, the integrity of the oocyte is maintained and its nucleus remains vesicular. Changes in the thecal microcirculation may play a key role in atresia: adjacent to the basal lamina of non-atretic follicles, there is a well-developed capillary network which is significantly reduced as atresia progresses.
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    Cell & tissue research 157 (1975), S. 367-390 
    ISSN: 1432-0878
    Keywords: Isocortex (Man) ; External glial layer ; Neuroglia ; Astrocytes ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The surface of the external glial layer of the isocortex in the human temporal lobe is generally slightly undulated, with a few protrusions and indentations. The surface is formed by an uninterrupted basement membrane which is continuous over the surface no matter how tortuous it becomes. The overall thickness of the glial layer is generally 15 to 25 μm, but diminishes to about 5 μm immediately beneath blood vessels. It consists mainly of a variable number of stacked glial cell processes. Two groups of cell bodies are encountered particularly in the middle and lower levels of the glial layer. Most of the cells are specialized fibrous astrocytes. They are characterized by eccentrically placed, rounded nuclei with homogeneously dispersed chromatin, and electron-lucent cytoplasm rich in filaments. Lipofuscin pigment granules occupy large areas of the perikaryon. The astroglial cells give rise to four types of processes: foot-processes, tangential and radial processes, and processes irregular in outline. The foot-processes ascend towards the cortical surface and terminate as flat expansions spreading out immediately beneath the basement membrane. Contiguous terminal expansions are connected by gap junctions. The individual profiles are irregular in form and fit together like in a jig-saw puzzle. The plasmalemma beneath the basement membrane is underlined by a fuzzy material, which is penetrated by glial filaments. In the terminal expansions individual or groups of mitochondria are abundant. The tangential processes are straight and slender and form a lattice within the middle and deep level of the external glial layer. They contain numerous filaments, evenly distributed or fasciculated. The remainder of the lattice is filled up by a considerable number of processes irregular in outline and varying greatly in size. They contain fewer filaments than the tangential processes, coursing in all directions, and glycogen particles. In both types of processes only a few mitochondria are present. These processes are also connected by gap junctions and desmosomes, too. Large cytoplasmic areas of astroglial cells localized in the deepest portion of the glial layer protrude into the neuropil of the molecular layer, giving rise to several radiate processes, which extend deeper into the cortex. The second, heterogeneous group of cell bodies is characterized by elongated nuclei, ovoid or irregular in outline, which are smaller than those of astroglial cells, and contain blocks of condensed chromatin; a thin cytoplasmic rim generating a few appendages surrounds the nucleus. The first sub-type is characterized by a nucleus with large chromatin blocks bordering the inner nuclear membrane and a medium-dense cytoplasmic matrix. The second sub-type displays smaller chromatin condensations at the inner nuclear membrane and many microtubules are scattered throughout an electron-lucent cytoplasm.
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    Cell & tissue research 157 (1975), S. 535-540 
    ISSN: 1432-0878
    Keywords: Cerebral perivascular spaces ; Peroxidase ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Horseradish peroxidase, perfused into the lateral ventricle of chick brain, freely and slowly diffuses through the cerebral extracellular spaces. The layer of astrocytic end-feet surrounding blood capillaries does not constitute a barrier to the tracer which permeates the basal lamina, diffuses between the pericytic cells and finally accumulates in the intercellular space beneath the tight junctions between contiguous endothelial cells. No evidence was found for transport by micropinocytotic vesicles from the cerebral parenchyma to the capillary lumen.
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