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  • 1980-1984  (542)
  • Ultrastructure  (541)
  • Nuclear reactions
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 169 (1984), S. 1-8 
    ISSN: 1432-0568
    Keywords: Serotonin ; Primary visual cortex ; Monkey ; Ultrastructure ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A quantitative and immunoelectronmicroscopical analysis of serotonin nerve fibers in the primary visual cortex of the monkey (Macaca fuscata) was made using a sensitive immunoperoxidase method for serotonin. The overall numerical density of serotonin-containing varicosities in the primate striate cortex was approximately 770,000/mm3 and the highest concentration of immunore-active varicosities (ca. 1,400,000/mm3) was observed in the upper portion of layer IVc, the next highest concentration being in layer IVb (ca. 1,180,000/mm3). At the ultrastructural level, the electron dense immunoreactive products were observed in the small granules (10–65 nm in diameter). The varicosities were usually small (0.5–1.0 μm in diameter) and made contact with both stellate and pyramidal cells. Serotonin fibers were often in close apposition to the poorly myelinated axons in layers IVb, V, and VI, and they rarely formed distinct synaptic structures with unlabelled neuronal elements.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 169 (1984), S. 205-208 
    ISSN: 1432-0568
    Keywords: Rat uterus ; Epithelium ; Aging ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary By scanning electron microscopy uterine luminal epithelium of the rat was studied to determine whether aging alters ovarian hormone stimulated ultrastructural changes in that portion of the endometrial surface into which implantation takes place in the younger animal. Results show that in the aged rat this surface differentiates in response to ovarian hormones in a manner qualitatively similar to that which occurs in the young animal. Epithelial cells of ovariectomized rats, both young and aged, were polygonal in outline, flattened, or even somewhat concave, and had short microvilli. Following estrogen treatment cells of both groups were round or oval and bulged into the lumen. Cells of young rats were covered with long microvilli. Most cells of aged rats had microvilli of equal or greater length; a small number of epithelial cells had fewer and shorter microvilli. Cells of progesterone-treated young and aged animals both were covered with short microvilli and bore membrane protrusions. The protrusions varied in size, shape and numbers both within and between age groups. These findings suggest that differences in the surface ultrastructure of the aged uterus reflect age-related changes in hormone levels.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 170 (1984), S. 107-112 
    ISSN: 1432-0568
    Keywords: Ultrastructure ; Cumulus ; Oocyte complex ; Human egg
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The cumulus cell mass enclosing a penetrated human egg was studied. The egg, recovered from the Fallopian tube approximately 80 h after luteinizing hormone peak and 35 h after insemination, was surrounded by a large, expanded and dissociated cumulus. Dispersions of the outermost cumulus cell layers occurred during processing, the innermost cell layers remained attached enclosing the egg. The photomicrographs showed that the follicular cells were embedded in an intercellular matrix and contact via gap-junction-like structures between neighboring cells existed. Cumulus cell processes traversing the zona pellucida were not found. Two types of follicular cells coexisted within the cumulus, light and dark cells. These cellular types, were different in morphology and size. Light cells displayed cytoplasmic organelles normally associated with protein synthesis and steroidogenesis. Dark cells with long cytoplasmic processes were involved in sperm phagocytosis. It is suggested from the characteristics of the cytoplasmic organclles that dark cells seem to be modified light follicular cells.
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  • 4
    ISSN: 1432-0568
    Keywords: Monoamine ; X-ray microanalysis ; Ultrastructure ; Brain stem ; Chicken
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary X-ray microanalysis after aldehyde-chromatedichromate treatment served to confirm the presence of monoaminergic terminals in the nucleus tegmentalis dorsalis (NTD) of the chicken. The monoaminergic terminals were represented as neuronal elements with electron-dense vesicles (EDVs) of several different shapes as seen in Eponembedded semi-thin sections. Conventional electron microscopic observations of the adjacent ultra-thin sections showed the EDVs to be comprised of spherical medium-sized (about 80 nm in diameter), large dense-cored (about 120 nm) and elongated granular vesicles (100–220 nm) in the same nerve varicosities. It is probable that the NTD, being a center of catecholaminergic efferent projections, may also receive direct monoaminergic inputs from an unknown area of the brain and/or from recurrent collaterals of the same catecholamine-containing neurons in the NTD.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 63 (1984), S. 269-275 
    ISSN: 1432-0533
    Keywords: Neurofibromatosis ; Cell culture ; Cell surface ; Cytoskeleton ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Structural proteins of cultured neurofibromatosis (NF) tumor and skin cells were studied with reference to control skin fibroblasts. In polyacrylamide gel electrophoresis (PAGE)/fluorography the banding patterns of the cell lysates were markedly similar. NF tumor cells, however, produced a 60 kD band with a stronger and a 48 kD band with a lighter protein staining and metabolic labeling intensity. Furthermore, skin cells were also characterized by a 26 kD protein and the tumor cells by a 22 kD protein with high metabolic labeling intensity. Neuraminidase/galactose oxidase/NaB3H4-labeled NF skin and control skin cells possessed a 220 kD protein that was less intensively labeled in the tumor cells. The banding pattern of the skin cells was also characterized by a protein with slightly lower molecular weight (86 kD) than that of the tumor cell lysates (90 kD). In all cell lines studied indirect immunofluorescence stainings revealed bright arrays of vimentin type intermediary filaments but no desmin, cytokeratin, glial fibrillary acidic protein (GFAP), or neurofilament proteins. NF skin and control skin cells possessed well developed actin-containing bundles of microfilaments, while those of the tumor cells lacked a typical stress-fiber organization. The general morphology of the tumor cell cultures was also irregular. Transmission electron microscopy revealed no basic differences in the structure of intermediary filaments or microfilaments. The present data provide basic knowledge of neurofibromatosis skin and tumor cells and demonstrate that cultured cells originating from neurofibromas are defective in both their intracellular and extracellular organization.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 65 (1984), S. 41-45 
    ISSN: 1432-0533
    Keywords: Colloid cyst ; Third ventricle ; Ultrastructure ; Pathogenesis ; Rathke's cyst
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The case involves a colloid cyst of the third ventricle in a 20-year-old man. The lining epithelia of the cyst were composed of two different types of epithelial cells; stratified squamous cells and mucincontaining columnar cells. The presence of both squamous and glandular cells in the cyst wall supports the contention that the colloid cyst in the present case derived from an non-neuroepithelial source. The clinico-pathology of this cystic tumor is compared here with other epithelial cysts of the central nervous system (CNS), especially Rathke's cyst.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 64 (1984), S. 81-84 
    ISSN: 1432-0533
    Keywords: Ganglioneuroma ; Cytoplasmic tubular inclusion ; Smooth endoplasmic reticulum ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Unusual tubular inclusions were observed in the cytoplasm of ganglion cells of a mediastinal ganglioneuroma in a boy of 7 years. The inclusions consisted of an aggregation of about 100-nm-sized tubular structures resembling ‘honeycomb-like’ tubular structures in the axoplasm of rats and mice and suggested to be derived from dilated rough endoplasmic reticulum. These structures differ from profiles reported in normal and pathologic conditions and seem to be related to the neoplastic character of the ganglion cells.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 64 (1984), S. 308-318 
    ISSN: 1432-0533
    Keywords: Angiogenesis ; Cerebellar hemangioblastoma ; Degranulation ; Heparin ; Mast cell ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The topographic distribution, population density, and ultrastructural features of mast cells were studied in six cases of cerebellar capillary hemangioblastoma. The vascular area of tumor tissue contained large numbers of mast cells (6.3 cells/high power field, ×400) in comparison with hyalinized area (0.3 cell) and adjacent cerebellar tissue (〈0.1 cell). Close association of mast cells with endothelial cells and stromal cells was found. The morphology of mast cell granules and their degranulation through dissolution of granule contents and exocytosis were illustrated. The findings suggest that an increased number of mast cells may represent one of the characteristic histological features of capillary hemangioblastoma, and continuous degranulation of mast cell granules with release of heparin may play an important pathophysiologic role in the vascular proliferation and expansion of the tumor.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 64 (1984), S. 282-296 
    ISSN: 1432-0533
    Keywords: Blood-nerve Barrier ; Perineurial barrier ; Leprosy neuropathy ; Ultrastructure ; Ferritin ; Ageing ; Drug treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Onset and nature of ultrastructural changes in endoneurial vasa nervorum during the pathogenesis of leprosy neuropathy and possibly associated alterations in the “blood-nerve barrier” were investigated, together with perineurial barrier functioning, in mice infected 20–28 months previously withMycobacterium leprae and in (ageing) non-infected mice. Barriers were tested by i.v. administration of markers (Trypan blue and ferritin) 1–4 days before killing the mice. Twenty-eight months after infection, histopathology of sciatic nerves was comparable to that seen in sensory nerves in clinically early human (borderline-) lepromatous leprosy. Schwann cells and endoneurial macrophages were bacillated, endothelia of endoneurial vessels not, and the perineurium rarely. Many infected mice and all (ageing) controls possessed ultrastructurally and functionally normal endoneurial vessels. Their continuous endothelium with close junctions had prevented marker passage, even when surrounding endoneurial tissue cells were quite heavily bacillated. The perineurium was also normal. By contrast, in infected mice showing hind limb paralysis serious histopathologic involvement and large globi of bacilli intrafascicularly in sciatic nerves, endoneurial blood vessels were abnormal. Open endothelial junctions, extreme attenuation, fenestrations, and luminal protrusions were all features comparable to neural microangiopathy encountered in leprosy patients (Boddingius 1977a, b). The “blood-nerve barrier” clearly had become defective allowing excessive exudation of Trypan blue and ferritin, via four pathways from the vessel lumen, deep into surrounding endoneurial tissues but halted by a normal perineurial barrier. Markers in such “blue” nerves were not found in bacillated or non-bacillated Schwann cells, thus denying significant phagocytotic and lysosomal activities of Schwann cells at this stage of neuropathy. Possible implications of barrier performances for anti-leprosy drug treatment of patients are discussed.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 65 (1984), S. 163-165 
    ISSN: 1432-0533
    Keywords: Human pinealomas ; Ultrastructure ; Paired twisted filaments ; Paired helical filaments ; Cytoskeleton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Paired twisted filaments (PTF) forming helices are described in tumor cells of three human pine-alomas. Each filament was 8.11±1.55 nm wide. The maximal width of the helix was 16.62±2.62 nm. The periodicity of the constrictions was 26.63±4.49 nm. These characteristics appeared original, suggesting protein, filaments possibly specific of pinealocytes. The similarities and discrepancies between PTF and Alzheimer's paired helical filaments (PHF) are discussed.
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 62 (1984), S. 225-229 
    ISSN: 1432-0533
    Keywords: Dandy-Walker syndrome ; Dandy-Walker cyst ; Ependymal cell ; Ultrastructure ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The ultrastructure of the wall of the Dandy-Walker cyst has been described rarely. A boy aged 2 years was confirmed clinically, neuroradiologically, and operatively as having a Dandy-Walker cyst in the posterior fossa. The cyst wall obtained during surgery consisted of an outer arachnoid cell layer, intermediate interwoven neuroglial strands, and an inner layer of cells which lacked the characteristic appearance of ependyma. An unusual finding was a small, buried island of ependymal cells in the intermediate layer of the neuroglial tissue. Ultrastructural study of the cyst wall provides a better understanding of the pathogenesis of the Dandy-Walker syndrome.
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  • 12
    ISSN: 1432-0533
    Keywords: Anti-acetylcholine receptor antibody ; Experimental autoimmune myasthenia gravis ; Monoclonal antibody ; Myasthenia gravis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To investigate pathogenic mechanisms in experimental autoimmune myasthenia gravis (EAMG) and myasthenia gravis (MG), we studied the acute and chronic effects in rats of injection of rat monoclonal antibodies (MCABs) directed against the acetylcholine receptor (AChR). Animals were severely weak 12 h after a single injection, at which time macrophages were found invading endplate regions of muscle and cholinesterase-stained regions were separted from the underlying muscle fibers. Ultrastructural studies showed findings identical to the acute phase of EAMG: degenerating postsynaptic membranes and invasion and phagocytosis of endplate regions by macrophages. Animals receiving sublethal doses of MCAB recovered clinically by 4–5 days after injection. Recovery was accompanied by a progressive decrease in the number of macrophages associated with endplates and reapposition to the myofibers of the cholinesterasestained regions. Animals injected once, or repeatedly over several months, remained clinically and electromyographically normal after recovery from the initial episode of weakness, but their endplate ultrastructure was highly simplified with blunted or absent synaptic folds and shallow or absent secondary synaptic clefts. These studies demonstrate that anti-AChR MCABs can induce the changes of both acute and chronic EAMG. There is good correlation between the inflammatory changes and the acute clinical disease but poor correlation between morphological and clinical parameters in the chronic syndrome. The latter observation suggests that severe ultrastructural changes, similar to those seen in chronic EAMG and MG, cannot account, at least in rats, for the clinical and electrophysiologic abnormalities of MG.
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  • 13
    ISSN: 1432-0738
    Keywords: Trialkylphosphorothioates ; Rat ; Lung ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The oral administration of an LD50 dose (25 mg/kg) of O,S,S-trimethyl phosphorodithioate to rats induced immediate, cholinergic symptoms. A delayed respiratory crisis followed, 3–4 days later, involving a pronounced increase in lung weight and extensive injury to the alveolar epithelium. This compound also induced the immediate liberation of secretory granules from the Clara cells. Minor changes in the surface appearance of these cells were also observed but no signs of injury were found in any cells of the bronchiolar epithelium. The complement of secretory granules was monitored, by the morphometric analysis of ultrathin sections. Clara cells from control animals were found to contain 9.55±1.16 (SEM) granules per cell profile. The Clara cells from dosed animals were largely devoid of granules until the 3rd day after administration. Many of these agranular cells were arranged in clusters and often showed signs of mitotic division. In surviving animals the subsequent replacement of granules resulted in a large increase in the numbers present and many exhibited abnormal morphology. Over twice the normal complement of granules, 22.45±0.42 (SEM) per cell profile, was found 6 days after dosing. The complement of granules subsequently returned to normal levels and the clusters of Clara cells were resolved within 14 days of dosing.
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Archives of dermatological research 276 (1984), S. 170-177 
    ISSN: 1432-069X
    Keywords: Penile apocrine cystadenoma ; Ultrastructure ; Filamentous fuzzy coat ; Epidermoid metaplasia ; Peridermlike cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Two cystadenomas occurring near the frenulum of the penis revealed a predominantly secretory pseudostratified columnar epithelium with PAS-reactive dome-shaped cytoplasmic protrusions at the luminal cellular parts. The content of secretory vacuoles was discharged into the cyst lumen by an exocytotic (eccrine) and ballooning type of extrusion. There were no indications of a real apocrine extrusion mechanism. No histogenetic derivation of these penile cystadenomas from apocrine sweat glands could be proved. An antennalike filamentous fuzzy coat on the luminal cytoplasmic membrane was most remarkable. Regionally, an epidermoid differentiation had developed. Morphologically, this process had begun just above the basal cell layer which had remained unchanged and led to the establishment of a stratified epithelium.Hyalin lamellarlike flattened cells at the luminal part displayed necrobiotic features and resembled periderm cells. There was no keratin pattern. Luminal cells of epidermoid differentiation still revealed a filamentous fuzzy coat which indicated that the undifferentiated cuboidal basal cells basically had a prospective secretory meaning and probably represented the target cells in the process of metaplasia.
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 36 (1984), S. 550-555 
    ISSN: 1432-0827
    Keywords: Enamel crystals ; Length ; Shape ; Apatite ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary An original method for fractionating and preparing isolated crystals of homogeneous size was developed. It was demonstrated that enamel apatite crystals are at least 100 µm long. The flexibility of the very long crystallites was demonstrated. Crystal curvatures, accounting for the irregular course of the prisms through the enamel thickness, were visualized and measured. It was shown that in the deep forming enamel layer, lateral branches may grow out of the crystals and crystal fusing often occurs, inducing the crystallites to assume pyramidal shapes with their wide bases pointing toward the dentino-enamel junction and one or two tops toward Tomes' processes. During the maturation process, the two tops of the still immature crystals also fuse so that the mature crystals acquire a rodlike aspect, with parallel faces and steplike graduations along thec axis, allowing a close contact between the crystals. These results support the hypothesis that the crystallites would be continuous from the dentino-enamel junction to the surface.
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  • 16
    ISSN: 1432-072X
    Keywords: Methanogenium tatii ; Ultrastructure ; Physiology ; Glycoproteins ; DNA-DNA Homology ; Taxonomy ; Archaebacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A new coccoid methanogen, Methanogenium tatii, was isolated and characterized. The mesophilic isolate can grow on and produce methane from H2:CO2 and formate. For growth acetate is strictly required. The cell shape, the G+C content of 54 mol% and DNA-DNA homology data suggest it to be a Methanogenium species.
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  • 17
    ISSN: 1432-072X
    Keywords: Nitrobacter hamburgensis ; Nitrite oxidoreductase ; Nitrate reductase ; Molybdenum iron-sulfur protein ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrite oxidoreductase, the essential enzyme complex of nitrite oxidizing membranes, was isolated from cells of the nitrifying bacterium Nitrobacter hamburgensis. The enzyme system was solubilized and purified in the presence of 0.25% sodium deoxycholate. Nitrite oxidoreductase oxidized nitrite to nitrate in the presence of ferricyanide. The pH optimum was 8.0, and the apparent K m value for nitrite amounted to 3.6 mM. With reduced methyl-and benzylviologen nitrite oxidoreductase exhibited nitrate reductase activity with an apparent K m value of 0.9 mM for nitrate. NADH was also a suitable electron donor for nitrate reduction. The pH optimum was 7.0. Treatment with SDS resulted in the dissociation into 3 subunits of 116,000, 65,000 and 32,000. The enzyme complex contained iron, molydbenum, sulfur and copper. A c-type cytochrome was present. Isolated nitrite oxidoreductase is a particle of 95±30 Å in diameter.
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  • 18
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 138 (1984), S. 229-232 
    ISSN: 1432-072X
    Keywords: Actinomycetes ; Streptomyces torulosus ; Morphology ; Ultrastructure ; Verrucate spores ; Knobby ornamentation ; Sheath
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The type strain of Streptomyces torulosus Lyons and Pridham (1971) was studied by scanning- and transmission electron microscope. Spore chains were formed in spirals by aerial mycelium. The spores were connected by nozzles in which small channels could be observed. The knobby ornamentations of the spores arised on a thin fibrous sheath, enveloping the spore chains. These irregular blunt projections, called knobs, had varying diameters of 100 to 250 nm. The base of the knob, consisting of globose to flattened electron dense material, was sitting directly on the sheath. It was covered by several small vesicles of the same material. Each hollow vesicle beared a thin bowlshaped shell of electron transparent material. In general, the cupular bowls and their supporting vesicles became easily depressed on their base, but not detached from the surface of the spores. This type of knobby spore ornamentation was suggested to be designated as a verrucate spore type.
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  • 19
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 57 (1984), S. 22-32 
    ISSN: 1432-1106
    Keywords: Ultrastructure ; Synaptology ; Hypoglossal nucleus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The purpose of this study was to define the types and distribution of synaptic terminals in the hypoglossal nucleus (XII) of the rat. Based on differences in bouton and vesicle size and shape, synaptic specializations and association with postsynaptic organelles, five types of terminals were identified in XII. In order of decreasing frequency they were: 1) S-boutons (spherical vesicles with an asymmetrical synapse); 2) F-boutons (flattened vesicles with a symmetrical synapse); 3) P-boutons (pleomorphic admixture of flattened and spherical vesicles with a symmetrical synapse); 4) C-boutons (pleomorphic vesicles with a subsynaptic cistern); and 5) Tboutons (spherical vesicles with an asymmetrical synapse and subsynaptic dense bodies). S-boutons were the predominant type found on dendrites, while boutons containing flattened vesicles were more prevalent on motoneuron somata. C-boutons were restricted exclusively to cell bodies and large dendrites, and T-boutons were seen primarily on smaller dendritic profiles. These results are, in general, comparable to those previously described in the ventral horn and cranial nerve motor nuclei in several species. However, differences were noted. Specifically, large M-boutons and axo-axonic synapses were not observed in the present study. The functional significance of these findings are discussed in relation to oro-lingual behaviour.
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  • 20
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 54 (1984), S. 385-389 
    ISSN: 1432-1106
    Keywords: Synaptosome ; 4-Aminopyridine ; Ultrastructure ; Exocytosis ; Recycling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Pinched-off nerve terminals (synaptosomes) from rat cerebral cortex were depolarized with 60 mM KCl and treated with 20 mM 4-aminopyridine in order to evaluate ultrastructural alterations. The empty presynaptic terminals were counted and their number was given as a percentage of the normal terminals. The proportion of empty terminals increased from 10.47±1.56% to 32.45±1.88% (P 〈 0.001) following treatment with 20 mM 4-aminopyridine. This effect of 4-aminopyridine depended on the presence of Ca++ in the incubation medium. The results are discussed in terms of facilitation by 4-aminopyridine of exocytotic transmitter release. We think that the increase of the empty synaptosomes was due to the exhaustion or inhibition of the synaptic vesicle recycling mechanism.
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  • 21
    ISSN: 1432-2307
    Keywords: Acromegaly ; hyperprolactinemia ; McCune-Albright syndrome ; pathology ; Pituitary ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary An 11-year-old girl, with the McCune-Albright syndrome, exhibited fibrous dysplasia of several bones, skin pigmentation, precocious puberty, growth hormone hypersecretion, acromegaly and hyperprolactinemia. Histologic, immunocytologic and ultrastructural investigation of the surgically-removed pituitary showed massive mammosomatotroph hyperplasia. Since no adenoma was found, the abundance of these bihormonal cells, capable of producing both growth hormone and prolactin, was implicated in the causation of growth hormone and prolactin excess. Somatoliberin overproduction and/or somatostatin and dopamine deficiency could not account for the hypophysial abnormality, since changes in secretory rates of these hypothalamic hormones would lead to proliferation of mature somatotrophs and lactotrophs, rather than mammosomatotrophs. In our patient, a congenital hypothalamic malfunction might have been accompanied by hypersecretion of an unidentified releasing factor, resulting in pathologic differentiation of the pituitary and mammosomatotroph hyperplasia. Alternatively, mammosomatotroph hyperplasia may have been due to an inherent genetic or embryonic defect affecting primarily the pituitary. According to this interpretation, the pituitary lesion represented yet another developmental error in the setting of the McCune-Albright syndrome.
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  • 22
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    Electronic Resource
    Springer
    Virchows Archiv 404 (1984), S. 177-185 
    ISSN: 1432-2307
    Keywords: Oesophagitis ; Herpetic cell change ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Ultra-thin sections obtained from routine biopsy specimens and cytological smears of 3 cases, together with one autopsy case suggestive of herpes oesophagitis, clearly demonstrate herpes viruses. The infected epithelial cells reveal different stages of virus replication and propagation. Cowdry A type inclusion bodies, however, representing early alterations in the course of infection are less frequent. Ground-glass looking nuclei of light microscopical balloon cells and infected multinuclear giant cells of epithelial origin are characteristic changes of the late ulcerative stage of herpes oesophagitis usually seen at the time of detection. These typical virus induced cell changes are mostly to be found at the ulcers edge.
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  • 23
    Electronic Resource
    Electronic Resource
    Springer
    Virchows Archiv 404 (1984), S. 253-263 
    ISSN: 1432-2307
    Keywords: Ameloblastic fibrosarcoma ; Histogenesis ; Histopathology ; Ultrastructure ; Fatal case
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This report presents a fatal case of ameloblastic fibrosarcoma arising from an ameloblastic fibroma, originating in the maxilla of 19-year-old Japanese male. An analysis of previously reported fatal cases of ameloblastic fibrosarcoma is included. In the course of the disease, the mesenchymal component of ameloblastic fibroma showed a dramatic histopathological transformation into sarcoma following multiple recurrence and the patient died of uncontrollable local infiltration of the cranial base. Although many cases have seemed to show disappearance of the epithelial component as malignant transformation progressed, many benign appearing ameloblastoid epithelial masses were scattered throughout the sarcomatous area even in the fatal stage in the present case. No distant metastases were found at autopsy. During multiple recurrences of the lesion, a little dysplastic dentin which was closely associated with both epithelial and mesenchymal components was found, though it could not be observed in autopsy material. Ultrastructural findings in autopsy material showed that the mesenchymal component consisted of undifferentiated mesenchymal cells, fibroblastic and fibrocytic cells with marked cellular and nuclear pleomorphism and that the epithelial component closely resembled the enamel organ.
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  • 24
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    Virchows Archiv 403 (1984), S. 361-376 
    ISSN: 1432-2307
    Keywords: Neurofibrosarcomas ; Neurogenic sarcomas ; Von Recklinghausen's disease ; Malignant schwannomas ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Thirteen soft tissue neurogenic sarcomas from twelve patients with neurofibromatosis (Von Recklinghausen's disease) were ultrastructurally examined. Electron microscopic studies revealed a wide spectrum of morphological manifestations varying from schwannian to fibroblastic, histiocytic, fibrohistiocytic and relatively undifferentiated cellular proliferations. A similar variation on light microscopic appearances has been previously reported in these neurogenic sarcomas. Neurogenic sarcomas occurring in patients with neurofibromatosis (Von Recklinghausen's disease), represent a heterogenous group of neoplasms with various patterns of differentiation identified ultrastructurally. The morphologic expressions of these neurogenic neoplasms can be conceptualized as a disorderly growth of the various peripheral nerve cellular components, or, as has been previously suggested, as a result of the multipotential nature and metaplastic ability of Schwann cells. S-100 protein immunohistochemistry was only positive in those neoplasms ultrastructurally proven to represent schwannian cellular proliferations. This study serves to document the range of fine structure that may be found in neurogenic sarcomas, to correlate the ultrastructural findings with the light microscopic appearance of these tumors, to determine the specificity of the electron microscopic findings, and immunohistochemistry for S-100 protein and assess their possible value in differential diagnosis.
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  • 25
    ISSN: 1432-2307
    Keywords: Localized fibrous tumour of the pleura ; Benign mesothelioma ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Five localized fibrous tumours of the pleura (benign mesothelioma) were studied ultrastructurally in order to elucidate their histogenesis. The histological subtypes of this benign fibrous lesion of the visceral pleura, i.e. the cellular, the collagenous, and the hyaline, were separately analysed. The tumours are composed of undifferentiated mesenchymal cells, intermediate and differentiated fibroblasts as well as collagenous interstitial tissue. The varying distribution of these cell elements account for the various histological subtypes. Morphological similarities between the mesenchymal tumour cells and the superficial mesothelial cells, which are always separated from the true tumour tissue by an intact basement membrane, were not observed. The different cellular elements can be regarded as parts of a continuous spectrum of cytodifferentiation, in which the mature fibroblasts are derived via intermediate forms from the undifferentiated cells. It is concluded that the localized fibrous tumours of the pleura arise from immature mesenchymal stem cells, which seems to be normally found in the submesothelial layer of the visceral pleura.
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  • 26
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    European archives of oto-rhino-laryngology and head & neck 239 (1984), S. 49-59 
    ISSN: 1434-4726
    Keywords: Glycerol ; Inner ear ; Ultrastructure ; Cellular and paracellular transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect has been studied of intravenously administered glycerol on paracellular and cellular transport of macromolecular HRP tracer in the lateral cochlear wall. The findings indicate osmotically induced diffusion phenomena by the opening of shunt pathways through junctional complexes in the stria vascularis. Vesicular transport is accelerated, direction of transport however is not affected by the changed osmolality.
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  • 27
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    Diabetologia 27 (1984), S. 397-402 
    ISSN: 1432-0428
    Keywords: Ultrastructure ; heart muscle ; streptozotocin ; short-term diabetes ; insulin treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The ultrastructure of myocardium was examined in short-term diabetic rats. Morphometric analysis showed the volume of myocytic mitochondria, sarcoplasmic reticulum and lipid droplets to be significantly increased compared with those of control animals. Further measurements of mitochondria and sarcoplasmic reticulum indicated that the augmentation of these compartments was accountable by the enlargement of pre-existing mitochondria, which were swollen, and of pre-existing tubules of sarcoplasmic reticulum, the lumen of which was dilated. After insulin treatment the morphological changes were returned to normal which indicates that they were not due to the toxic effect of streptozotocin but were caused by the diabetic state per se. This suggestion is further supported by the finding that experimentally induced metabolic acidosis without diabetes did not cause any morphologically detectable changes in the heart muscle. It is concluded that short-term diabetes in the rat causes mitochondrial swelling, dilatation of sarcoplasmic reticulum and accumulation of lipid in cardiac myocytes, and that these changes are preventable with insulin treatment. We suggest that insulin may have an important role in the maintenance of metabolism in heart muscle.
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  • 28
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    Virchows Archiv 402 (1984), S. 331-336 
    ISSN: 1432-2307
    Keywords: Carcinoid ; Uterine cervix ; Histopathology ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A case of carcinoid tumor of the uterine cervix is reported. The patient was a 76-year-old Japanese woman with a complaint of vaginal bleeding. She was clinically diagnosed as stage IVb carcinoma of the uterine cervix. Light microscopically, the tumor was characterized by formation of solid cell nests and, in limited areas, glandular structures. The tumor cells in solid cells nests showed positive argyrophil reaction but were negative for argentaffin reaction. At the ultrastructural level, the cytoplasm of the tumor cells contain numerous neurosecretory granules, microfilaments and well-developed Golgi complexes. On the bases of histochemical and electron microscopic features of tumor cells, the tumor was diagnosed as carcinoid tumor of the uterine cervix.
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  • 29
    ISSN: 1432-2307
    Keywords: Mesothelioma ; Histogenesis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary During an ultrastructural review of 30 diffuse and 10 localized mesotheliomas, it was apparent that some micrographs showed various stages in the developmental processes involved in the formation of histological patterns in diffuse mesotheliomas and a histogenetic link between diffuse and localized mesotheliomas. Cells in the stromal or sarcomatous regions of diffuse mesothelioma often show varying degrees of mesothelial differentiation and a gradual transition to cells with typical mesothelial characteristics that organize into structures recapitulating the surface layer of serosal membranes. Tumor cells in localized mesotheliomas had many similarities to the “stromal” cells in the diffuse counterpart including intercellular junctions, rare microvilli and occasional foci of basal lamina. It is postulated that diffuse and localized mesotheliomas share a common histogenetic origin as a result of neoplastic induction of specialized submesothelial cells. In this concept, tumor cells in diffuse mesotheliomas reflect stages in the differentiation and organization of normal serosal membranes and localized mesotheliomas mirror the earliest phases of this process.
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  • 30
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    Virchows Archiv 402 (1984), S. 439-450 
    ISSN: 1432-2307
    Keywords: Atypical germ cells ; Carcinoma in situ of the testis ; Normal germ cells ; Ultrastructure ; Differential diagnosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary It is uncertain whether the so called intratubular atypical germ cells (carcinoma in situ cells) demonstrable in the testicular tissue around different germ cell tumors and in testicular biopsies of patients with impaired fertility are identical with regard to their morphology and further development. Thus atypical germ cells of 18 patients with testicular germ cell tumors and of 3 patients with atypical germ cells in testicular biopsies without tumor were studied by electron microscopy and/or by immunohistochemistry. The atypical germ cells show characteristic alterations distinguishing them from normal germ cells, especially spermatogonia. However, there are no differences between atypical germ cells in the above mentioned groups. Immunohistochemical reactions are negative with anti-alpha-fetoprotein and anti-beta-human-chorionic-gonadotropin, but 6 of the 15 cases are positive with antiferritin. However, this positive reaction occurs in cases in different diagnostic groups. Atypical germ cells of the different groups cannot be distinguished by electron microscopy or immunohistochemical methods, but further investigations vestigations, including cell cultures, may provide more information.
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  • 31
    ISSN: 1432-2307
    Keywords: Proximal tubule ; Atrophy ; Cortical interstitium ; Human nephropathy ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A systematic ultrastructural analysis of proximal tubule atrophy and cortical interstitial changes was carried out in human chronic nephropathy. The investigation was based on human hydronephrotic kidneys, which had been surgically removed and subsequently perfusion-fixed for light and electron microscopy. Normal kidney tissue, which was derived from nephrectomy specimens with pathological changes confined to part of the kidney or to the renal pelvis, was used for control material. A slight degree of proximal tubule atrophy was characterized by reduction of mitochondria and basolateral membranes, enlargement of large endocytic vacuoles and increased numbers of lysosomes containing lamellar material. In moderate atrophy these changes were further accentuated, and in addition there was an increasing loss of microvilli and a reduction of endocytic invaginations and small endocytic vacuoles. In severe atrophy all types of organelles were sparse and the architecture of the tubule cells greatly simplified. A distinctive feature of atrophic tubules was the presence in the tubule cells of large bundles of actin-like filaments, which were often associated with outpouchings of basal cell parts and basement membrane. The reduction of mitochondria and basolateral cell membranes and the changes of endocytic vacuoles and lysosomes indicate that proximal tubule atrophy also in early stages may be associated with impairment of tubular transport processes. Comparisons with previous observations in various types of experimentally induced tubule cell degeneration and with the ultrastructure of regenerating proximal tubule cells provide some evidence that degenerative changes as well as imperfect regeneration of tubule cells may contribute to the alterations of ultrastructure in tubular atrophy. It is suggested that changes of the cortical interstitium may be of pathogenic importance for the progression of tubular atrophy by altering the spatial relationships between tubules and capillaries.
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  • 32
    ISSN: 1432-234X
    Keywords: Ultrastructure ; Gills ; Epithelial cells ; Polychaeta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ultrastructure of gill epidermal cells of Diopatra neapolitana and their relationship with blood spaces are described. The existence of a basal infolding complex, related to the blood spaces, is also reported. A possible involvement of these cells in osmoregulation and ion interchange, apart from their well-known role in respiration, is suggested.
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  • 33
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    Journal of cancer research and clinical oncology 107 (1984), S. 183-194 
    ISSN: 1432-1335
    Keywords: Collagen ; Stereology ; Oral carcinogenesis ; Inflammation ; Ultrastructure ; Lamina propria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Stereological point-counting methods were used to determine the volumetric alterations in collagen from the lamina propria immediately beneath the epithelial-connective tissue junction in hamster check-pouch mucosa treated with the chemical carcinogen DMBA. In addition, a non-neoplastic inflammatory control was evaluated in which a delayed hypersensitivity reaction was induced by the contact-sensitising agent DNCB. DMBA-treated tissues were assigned to histopathologically defined hyperplasia, dysplasia and carcinoma stages. The volume densities of collagen present in unit volume of extracellular lamina propria were found to decrease progressively and significantly in DMBA-treated tissues when compared with values obtained from normal untreated mucosa. Values from the inflammatory control were comparable with those from the dysplasia stage of carcinogenesis. The mechanisms responsible for these decreases in collagen volume density are unknown, but contributory factors might include collagen destruction by enzymes originating in either the epithelium or the cells of the inflammatory infiltrate, dilution of collagen produced by inflammatory oedema or alterations in the synthetic capabilities of fibroblasts.
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  • 34
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    Theoretical and applied genetics 68 (1984), S. 305-309 
    ISSN: 1432-2242
    Keywords: Impatiens ; Microspore mitosis ; Plastid distribution ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This paper describes the unequal distribution of plastids in the developing microspores of Impatiens walleriana and Impatiens glandulifera which leads to the exclusion of plastids from the generative cell. During the development from young microspore to the onset of mitosis a change in the organization of the cytoplasm and distribution of organelles is gradually established. This includes the formation of vacuoles at the poles of the elongate-shaped microspores, the movement of the nucleus to a position near the microspore wall in the central part of the cell, and the accumulation of the plastids to a position near the wall at the opposite side of the cell. In Impatiens walleriana, the accumulated plastids are separated from each other by ER cisterns, and some mitochondria are also accumulated. In both Impatiens species, the portion of the microspore in which the generative cell will be formed is completely devoid of plastids at the time mitosis starts.
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  • 35
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    Virchows Archiv 404 (1984), S. 7-16 
    ISSN: 1432-2307
    Keywords: Fibroadenoma ; Stromal cells ; Actin ; Ultrastructure ; Myofibroblast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Fourteen fibroadenomas of the human breast were examined by light and electron microscopy, and by immunohistochemistry for actin. They were classified into 3 groups according to their stromal patterns; myxoid, fibrous-cellular and sclerotic. Actin immunohistochemistry revealed that the stromal areas were strongly positive in the fibrous-cellular group and weakly positive in the myxoid and sclerotic groups. By electron microscopy the stromal cells in most cases of the myxoid and fibrous-cellular groups were fibroblasts, containing varying amounts of microfilaments, 5–7 nm in diameter (actin type filaments). However, a dense body was not usually present suggesting these stromal cells were variants of myofibroblasts. The amount of microfilaments in fibroblasts was greater in the fibrous-cellular group than in the myxoid group. This was consistent with the results of actin immunohistochemistry. In 3 cases of the fibrous-cellular group peculiar structures simulating Z-lines of striated muscles were noted in some stromal cells. Since no myosin filaments were detected, they were regarded as intermediate structures between Z-lines of striated muscles and dense bodies of smooth muscles. In the sclerotic group, stromal fibroblasts were sparse and had fewer organelles.
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  • 36
    ISSN: 1432-2307
    Keywords: Morphometry ; Human bladder tumour ; Human chronic cystitis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Transmission (TEM) and scanning electron microscopic (SEM) observations were performed on well-differentiated tumours and chronic cystitis in the human urinary bladder. SEM showed that the pleomorphic microvilli were present not only on the luminal surface of the tumour but also on the surface of inflammatory mucosa. The ultrastructure of six tumours and 5 cases of chronic cystitis was evaluated morphometrically. Bladder tumour and inflammatory mucosa were divided into several layers, namely outermost cells (S), subsurface cells just beneath these (S1), subsurface cells of 2 or 3 layers below (S23), intermediate cells of 2 or 3 layers above the basal cells (123), intermediate cells just above the basal cells (I1) and basal cells (Ba). Areas of nucleus, cytoplasm and cytoplasmic organelles, numbers of nucleoli, nuclear bodies, mitochondria and lysosomes together with irregularity of the cell and nucleus were estimated according to the methods of Weibel. A multi-variate analysis of variance on these variables showed that the above subdivision of layers was necessary for the comparison of tumour and inflammation. Discriminant analysis showed various differences between tumour and inflammatory mucosa. The results indicated that the Ba layer is the most effective site for differentiating the tumour from inflammation. Ba cells with large and irregular cytoplasm with an enlarged Golgi area, accompanied by many vacuolar structures, may be indicative of tumour rather than inflammation.
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  • 37
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    Virchows Archiv 405 (1984), S. 41-53 
    ISSN: 1432-2307
    Keywords: Fibromatosis ; Dupuytren's contracture ; Myofibroblast ; Ultrastructure ; Histochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Forty three cases of palmar fibromatosis were studied by light and electron microscopy, enzyme histochemistry, and ultrastructural immunohistochemistry. By electron microscopy most of the cells composing the nodules in both the proliferative and the involutional stages were identical to myofibroblasts. The myofibroblasts in the involutional nodules often possessed microfilament aggregates probably representing contraction of micro(actin)fllaments in the cytoplasm. The proliferative nodules revealed small perivascular haemorrhages and haemosiderin deposits accompanied by accumulation of macrophages and some lymphocytes; these inflammatory cells possibly secrete a certain growth factor inducing proliferation of genetically abnormal fibroblasts and myofibroblasts. Diaminopeptidase IV was detected in myofibroblasts and fibroblasts by enzyme histochemistry and ultrastructural immunohistochemistry; the enzyme may play a role in the metabolism of intercellular substances. Some perivascular mesenchymal cells, interpreted as variants of myofibroblasts, had moderate activity of alkaline phosphatase.
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  • 38
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    Urological research 12 (1984), S. 187-192 
    ISSN: 1434-0879
    Keywords: Gossypol ; Bull spermatozoa ; Motility ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Gossypol acetic acid in a concentration of 1,000 μg/ml solvent is able to immobilize 1 ml of native bull semen (sperm concentration: 8.5×108/ml; motility rate: 87.4%) within 30 min. After GAA treatment the spermatozoa show severe morphological damage on the membrane system, on the acrosomal complex and on the tubular complex of the end piece. The working mechanism of GAA can be assumed to be inactivation of enzyme activities or in direct reactions with plasma membrane material.
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  • 39
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    European archives of oto-rhino-laryngology and head & neck 239 (1984), S. 133-144 
    ISSN: 1434-4726
    Keywords: Esthesioneuroblastoma ; Intermediate filaments ; Secretory granules ; Ultrastructure ; Immunohistology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A case of esthesioneuroblastoma, the pathological diagnosis of which almost always causes great difficulties, was investigated ultrastructurally, biochemically, and immunohistologically, using antibodies against the five known types of intermediate filaments [keratin, vimentin, desmin, glial fibrillary acidic protein (GFAP) and neurofilaments]. The tumour cells did not react with antibodies against any of the five intermediate filament proteins. Ultrastructural investigations showed dense cored secretory granules in the cytoplasm and cell processes. Thus, immunohistology offers by “exclusion” a differential diagnosis to avoid often misdiagnosed tumours (undifferentiated carcinomas, embryonal rhabdomyosarcomas, and malignant lymphomas), since carcinomas react with antikeratin, embryonal rhabdomyosarcomas with antibodies to desmin and malignant lymphomas show immunofluorescence with antibodies to vimentin. The biological behaviour (age distribution, tendency to metastasize), the normal values of biochemical parameters, homovanillic acid and vanilmandelic acid (HVA, VMA), and the absence of neurofilaments distinguish this type of tumour from the peripheral sympathetic neuroblastoma.
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  • 40
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    International orthopaedics 7 (1984), S. 215-221 
    ISSN: 1432-5195
    Keywords: Experimental arthrosis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé Les auteurs ont réalisé une arthrose expérimentale chez le chien en injectant dans une articulation le liquide obtenu par ponction d'une autre articulation du même animal, dont le cartilage a été préalablement scarifié de façon aseptique. L'examen des surfaces articulaires en microscopie électronique montre des altérations dégénératives progressives au niveau de la matrice extra-cellulaire, des chondrocytes et de la membrane péri-cellulaire. Ces modifications augmentent après des injections répétées de liquide synovial. Dans une autre série d'animaux, on a injecté soit le culot de centrifugation, soit le surnageant et on a comparé les effets obtenus vis-à-vis des structures cellulaires et extra-cellulaires.
    Notes: Summary Experimental arthrosis was induced in previously healthy joints in a group of dogs by injection of fluid aspirated from another joint of the same animal previously damaged by trauma under sterile conditions. Using electron microscopy progressive degenerative changes were observed at the surface of the joint, in the extracellular matrix, in the chondrocytes and in the pericellular band. The changes increased following serial injections of the joint fluid. In another series, the joints were injected either with the centrifuged concentrate or the supernatant fluid and a comparison made of the contrasting effects upon the cellular and extracellular structures.
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  • 41
    ISSN: 1573-5036
    Keywords: Actinorhizae ; Datisca cannabina ; Frankia ; Nitrogen fixation ; Root nodules ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The fine structures of the microsymbiont inside the root nodules ofDatisca cannabina have been studied by light, by transmission- and by scanning-electron microscopy. The endophyte is prokaryotic and actinomycetal in nature. The hyphae are septate and branched, diameter 0.3–0.5 μm. The tips of hyphae are swollen to form electron-dense, clubshaped to filamentous vesicles, ranging in diameter: 0.4–1.4 μm. The endophyte penetrates through walls of the cortial cells. The infected zone is kidney shaped and confined to one side of the acentric stele. The orientation of infection is reversed from other actinorhizae exceptCoriaria. The hyphae are near the host cell wall and vesicles are directed towards the central vacuole. Vesicles are aseptate and no collapsing of the vesicle cell wall (void area) has been observed. Vesicle clusters structures are globular with an opening at one side of the cluster. The host cell is multinucleate or contains a lobed nucleus. Groups of mitochondria are located in between the hyphae, suggesting a strong association between the host and the endophyte for energy supply and amino acid production. The consequences of the inability to separate the mitochondria from the vesicle clusters in nodule homogenates in physiological studies have been discussed. Isolated vesicles clusters showed dehydrogenase activity, indicated by the presence of formazan crystals, after incubation with NADH and NBT. Strongest reducing activity was found within the vesicles. The possible role of filamentous vesicles in nitrogen fixation has been discussed.
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  • 42
    ISSN: 1573-5036
    Keywords: Aeration status ; Microorganisms ; Mucilage ; Rhizosphere ; Ultrastructure ; Wheat root
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Outer layers of wheat roots grown in aerated and unaerated nutrient solutions were studied by transmission electron microscopy. Root growth was considerably impaired in unaerated nutrient solution. In contrast to aerated roots, no mucilaginous layer but dense bacterial colonization were observed on the root caps of unaerated roots. The root cap mucilage had apparently been decomposed by the microorganisms. The peripheral root cap cells of the unaerated roots appeared to contain less cell organelles than those of the aerated roots, while the central cap cells and the meristematic cells of the root tip seemed not to be affected by lack of aeration. The bacterial population in the elongation, root hair, and lateral root zones, was also remarkably higher on roots grown in unaerated nutrient solution. In the lateral root zone of unaerated roots, even the cortical cells were invaded by bacteria.
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  • 43
    ISSN: 1573-5036
    Keywords: Alnus Hippophaë ; Mycorrhiza ; Myrica ; Nitrogenase ; Phosphate ; Triple symbiosis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The roots ofHippophaë rhamnoides which regularly bear actinomycete induced nodules when growing on Scottish sand dunes have also been found to support an endomycorrhizal association withGlomus fasciculatus. Ultrastructural and cytochemical studies carried out on the indigenous infections of establishedHippophaë mycorrhizal roots would support the postulate that transport is indeed occurring between the fungal symbiont and the host plant and vice versa in respect of phosphate and carbohydrate. Experiments using various inoculation regimes, demonstrated the significant improvement in the mycorrhizal/nodulated plants compared to the nodulated-only and the mycorrhizal-only plants with respect to plant growth, uptake of phosphate and nitrogenase activity, when grown in a medium poor in combined nitrogen and soluble phosphate. Preliminary work onAlnus andMyrica species growing in Central Scotland indicates that the mycorrhizae associated with these nodulated root systems exhibit a different interaction pattern which may be dependent on habitat type and associated angiosperm species.
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  • 44
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    European journal of applied physiology 52 (1984), S. 266-271 
    ISSN: 1439-6327
    Keywords: Human ; Endurance exercise ; Muscles ; Fibre types ; Histocytochemistry ; Ultrastructure ; Morphometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The main fibre types ofM. vastus lateralis of 10 trained or untrained male individuals (25–35 years) were quantitatively determined by morphological techniques; the fibre types being defined according to the M-band appearance. The volume density of mitochondria (Vmit) was higher in endurance-trained muscles.Vmit was higher in Type 1 than in Type 2 fibres, there being no difference between subtypes of Type 2 fibres. The volume density of lipid droplets (Vli) showed a wide range of values both with respect to degree of training and between fibre types. Z-band width was not influenced by endurance training, but was considerably larger in Type 1 than in Type 2 fibres. Discriminant analysis showed that 46% of the fibres, preclassified according to the M-band appearance, would have been correctly allocated on basis of theVmit. The corresponding value for lipid droplets was 42% and for the Z-band width, 62%. It is concluded thatVmit is not a satisfactory criterion for discriminating between fibre types, especially between Type 2A and Type 2B in trained subjects. The study also shows that endurance training reduces the relative importance of individual-dependent factors in comparison with muscle fibre properties when concerningVmit.
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  • 45
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    Plant systematics and evolution 147 (1984), S. 189-203 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Ericaceae ; Onagraceae ; Mimosaceae ; Musaceae ; Ultrastructure ; function of pollen connecting threads and viscin threads ; palynology ; pollination ecology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Viscin threads and other pollen connecting threads of some angiosperm families were investigated, especially those ofEricaceae. According to the definition adopted, viscin threads are ± long exinous processes which consist of exinous material and connect pollen grains or tetrads. Such viscin threads are found within theOnagraceae, Caesalpiniaceae, Ericaceae, andMimosaceae only. While they differ in structure and composition, they always consist of sporopollenin and exhibit a very strong stickiness, even after all viscid substances have been removed by acetolysis. In contrast, the pollen connecting scleroprotein threads ofOrchidaceae and the cellular threads ofStrelitzia reginae Aiton. (Musaceae) are not connected with the exine surface, are destroyed by acetolysis, and thus do not correspond to viscin threads.
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  • 46
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    Protoplasma 119 (1984), S. 55-61 
    ISSN: 1615-6102
    Keywords: Rhodophyta ; Nitophyllum ; Membranous body ; Plastid ; Red algae ; Thylakoidal origin ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The fine structure of plastids in the early stages of differentiation has been studied during the carposporogenesis of the red algaNitophyllum punctatum (Stackh.) Grev. A membranous body has been found in the plastidial matrix, which shows connections either with thylakoids, or with the plastidial genophore. More than one membranous body may be present and in some instances they show a morphological relationship also with the plastidial limiting membranes. The presence of such bodies has been observed also in fully differentiated plastids in a number of other red algae currently under study. It has been shown that the plastidial envelope may release in the matrix vesicles that give rise to the single thylakoids typical of the red algal plastids.
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  • 47
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    Protoplasma 120 (1984), S. 61-71 
    ISSN: 1615-6102
    Keywords: Fungus ; Spindle pole body ; Entomophthoraceae ; Erynia neoaphidis ; Ultrastructure ; Replication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A detailed account of the ultrastructure and behaviour of the spindle pole body (SPB) of the entomophthoraceous fungusErynia neoaphidis is presented for the first time. The SPB consists of extranuclear (ENC) and intranuclear (INC) components. The ENC is a “saucepan-shaped” structure which lies in a pocket of the nuclear envelope. It is composed of a forked, fibrillar “handle” and a shallow, cylindrical “pan”. The “pan” has a wall of two layers, both of which are thickened with a regular periodicity so that they appear to be “beaded”. It is postulated that the “pan“ is formed from rough endoplasmic reticulum and that it synthesizes the amorphous, electron-dense material coating the ENC. The INC is a “saucer-shaped”, electron-dense plaque in which the ends of the spindle microtubules terminate. During metaphase, a “clear zone” separates the INC from the nuclear envelope and persists until telophase. The roles of the amorphous, electron-dense material and the “clear zone” as well as the method of SPB replication are discussed.
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  • 48
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    Protoplasma 120 (1984), S. 72-83 
    ISSN: 1615-6102
    Keywords: Fungus ; Mitosis ; Entomophthoraceae ; Erynia neoaphidis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary An account of mitosis in the aphid-pathogenic, entomophthoraceous fungusErynia neoaphidis is presented. The mitotic apparatus is characterized by a closed, intranuclear, polarized spindle. Chromosomes are permanently attached by kinetochore microtubules (kcMTs) to the poles during mitosis. The spindle develops as the spindle pole bodies migrate and separate. At metaphase the eccentric spindle contains only kcMTs and is located in a relatively chromatinfree zone. Paired sister kinetochores are arranged in a broad metaphase plate. During anaphase kcMTs shorten, astral and nonchromosomal microtubules develop and elongate and the interpolar distance increases.
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  • 49
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    Protoplasma 121 (1984), S. 65-76 
    ISSN: 1615-6102
    Keywords: Blastocladiales ; Chytridiomycetes ; Coelomomyces ; Cytoplasmic cleavage ; Gametogenesis ; Mosquito-copepodpathogen ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ultrastructure of gametogenesis was studied inCoelomomyces dodgei Couch (Blastocladiales, Chytridiomycetes), an obligate parasite of anopheline mosquito larvae and the copepod,Acanthocyclops vernalis. In infected copepods reared under a 16/8 hours light/dark photoperiod at 25 +2 °C., the gametophyte develops over a period of approximately seven days, and gametogenesis is triggered by the onset of the dark period during the last day of development. The initial step of gametogenesis is the elongation of the centriole to form the kinetosome, and measuring time from the onset of the final dark period (0 hours), this occurs prior to the beginning of the light period (8 hours). Subsequently, small vesicles that appear to originate from elements of the rough endoplasmic reticulum (rER) fuse at the distal end of the kinetosome forming the flagellar vesicle into which the axonemal microtubules elongate to form the flagellum (8–12 hours). Similar small vesicles apparently also derived from rER align in planes and fuse to form cleavage furrows which delineate the gamete initials (12–14 hours). As the gamete initials begin forming, the mitochondria within each initial fuse to form a single mitochondrion that associates with the lipid globules and microbodies forming the microbody-lipid globule complex (12–16 hours). The time elapsed between the formation of the flagellar vesicle to the release of mature gametes from the copepod host is about 8.5 hours. No differences were observed in the processes or timing of gametogenesis in male and female gametophytes.
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  • 50
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    Protoplasma 121 (1984), S. 77-86 
    ISSN: 1615-6102
    Keywords: Blastocladiales ; Coelomomyces ; Gametes ; Mosquitocopepod pathogen ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary As part of an investigation on the developmental biology ofCoelomomyces dodgei Couch (Blastocladiales, Chytridiomycetes), the ultrastructure of the male and female gametes was studied. The nucleus is central and conical in shape except for a basal spur that curves back towards the large plate-like mitochondrion. A nuclear cap of ribosomes sits on the flat anterior end of the nucleus. Approximately seven lipid globules are partially embedded in the mitochondrion and are interconnected by membrane cisternae. The lipid globules are covered by a single fenestrated microbody and a backing membrane lies between the microbody and the gamete plasma membrane. The kinetosome is at the base of the nucleus and is connected to a single, posterior, whiplash flagellum. A nonkinetosomal centriole is absent. In the peripheral cytoplasm of both mating types there is a paracrystalline body of unknown composition and function. No significant ultrastructural differences were found between the male and female gametes.
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  • 51
    ISSN: 1615-6102
    Keywords: Plastid greening ; Zea mays ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effects of light intensity and cell age on the greening of etioplasts were studied in seedlings of maize. We could see that in the youngest tissues examined by us the etioplast greening is very fast and occurs according to a particular pattern which is characterized by the contemporary presence of grana and large non crystalline prolamellar bodies. On the contrary, in the oldest examined tissues the etioplast greening is slow and the formation of grana appears to be delayed and subsequent to the using up of the prolamellar bodies. In the young tissues the intensity of the light mainly affects the duration of the lag-phase preceding the chlorophyll accumulation, while in the old tissues it also affects the total amount of chlorophyllous pigments, the restraining effect of the light appearing amplified by a concomitant restraining effect of cell age.
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  • 52
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    Protoplasma 121 (1984), S. 199-208 
    ISSN: 1615-6102
    Keywords: Psychotria ; Leaf nodules ; Calyx nodules ; Symbiosis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The occurrence and structure of calyx nodules in the flowers of two leaf nodulated rubiaceous speciesPsychotria punctata Vatke andPsychotria kirkii Hiern. has been described for the first time at the ultrastructural level. Bacteria, resident in colleter-secreted mucilage in the space between calyx and corolla, invade stomatal pores which develop on the calyx protoderm. The bacteria proliferate in the substomatal cavity and then invade the calyx mesophyll. This invasion is most pronounced inP. punctata where the bacteria even penetrate and enter the cells of the vascular tissue. Although no sheath forms around the calyx nodules, the calyx mesophyll cells surrounded by the bacteria become identical in shape, size and secretory function to the invasive mesophyll cells of leaf nodules. The functional and evolutionary significance of calyx nodulation is discussed.
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  • 53
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    Protoplasma 122 (1984), S. 203-221 
    ISSN: 1615-6102
    Keywords: Actinia fragacea ; Granular amoebocytes ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The structure of granular amoebocytes of the intertidal sea anemoneActinia fragacea (Cnidaria: Anthozoa) has been investigated using the electron microscope. Cells from the gonads of large, intact individuals were studied in most detail, but other regions of the anemone were also examined. The amoebocytes are cells of variable appearance which are widely distributed both in the mesogloea and in the epithelial cell layers. They contain numbers of characteristic dense granules, which may enclose spherical cores of greater or lesser electron density. They also contain rough endoplasmic reticulum, Golgi apparatus and a range of inclusions, some of which may have lysosomal origins. They may contain extensive deposits of glycogen, and usually smaller quantities of lipid droplets. They may take on a variety of forms, depending partly on their location within the various types of mesogloea and epithelia. The amoebocytes appear to be motile and phagocytic, and may also be involved in the storage and transport of glycogen. They are involved with gametogenesis, both during the development of the oocytes and spermatogenic cysts and during the resorption of degenerating gametes. Their possible role in the secretion or maintenance of the mesogloea remains uncertain. No evidence of amoebocytes differentiating into other cell types was obtained.
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  • 54
    ISSN: 1615-6102
    Keywords: Chromosome fragments ; Holokinetic chromosomes ; Karyomeres ; Nucleolar material ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Chromosomes and nucleoli in the karyomeres of cleavage eggs of the arrhenotokous spidermiteTetranychus urticae Koch were treated with a silver-staining procedure for nucleolar material to establish the number of nucleoli and of the chromosomes that produce them. Each of the three holokinetic chromosomes of the haploid chromosome complement produces nucleolar material. This is confirmed by observations on the ultrastructure of karyomeres in serial sections of interphase cleavage divisions. These findings are thought to be in agreement with facts from previous radiation research and may help to explain the fate of induced fragments in holokinetic chromosomes.
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  • 55
    ISSN: 1615-6102
    Keywords: Freeze-fracture ; Isolated rye protoplasts ; Osmotic contraction ; Plasma membrane-derived vesicles ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Following osmotic contraction of isolated rye protoplast (Secale cereale L. cv. Puma) that results in nearly a 50% reduction in volume, the plasma membrane was smooth, with no folding or pleating. Instead, deletion of plasma membrane occurred and numerous cytoplasmic vesicles were observed. As a result, the area of the plasma membrane was reduced by approximately 40%. Thin sections revealed that the cytoplasmic vesicles were membrane bound and not merely voids in the cytoplasm. High resolution video microscopy revealed the extent of vesiculation showing large clusters of cytoplasmic vesicles following osmotic contraction. Labeling the plasma membrane with fluorescein-Con-A prior to hypertonic contraction suggested that the cytoplasmic vesicles were derived from the plasma membrane. Freeze-fracture particle density on both the protoplasmic (PFp) and exoplasmic face (EFp) of the plasma membrane remained unchanged following contraction, which is consistent with a unit-membrane deletion into cytoplasmic vesicles. Upon partial re-expansion of the protoplasts, thin sections showed that the vesicles remained in the cytoplasm. These results using osmotic manipulation confirm earlier observations of isolated protoplasts at the light microscope level. Upon contraction plasma membrane is deleted into cytoplasmic vesicles, which are not readily reincorporated into the plasma membrane upon expansion. Lysis occurs before the original volume and surface area are regained.
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  • 56
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    Keywords: Entomophaga aulicae ; Fungi ; Mitosis ; Nucleus associated organelle ; Taxonomy ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Nuclei in protoplasts ofEntomophaga aulicae contain abundant condensed chromatin and a large central nucleolus. The metaphase spindle occupies a small eccentric area of the nucleus while the remainder of the nucleus is filled with condensed chromatin. Small portions of condensed chromatin are aligned along a broad metaphase plate and connected to the spindle poles by kinetochore microtubules. The nucleus associated organelle (NAO) is a solid barlike structure which lies at the spindle poles and is closely associated with the outer membrane of the nuclear envelope. Comparison of the nuclear characteristics ofE. aulicae with those of other members of theEntomophthorales supports the separation of theEntomophthoraceae from theBasidiobolaceae andAncylistaceae. Further comparison of details of nuclear division in theEntomophthoraceae, specifically NAO morphology, may be useful in helping to delineate evolutionary lines within the family.
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  • 57
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    Protoplasma 123 (1984), S. 104-115 
    ISSN: 1615-6102
    Keywords: Constrictive binary fission ; Cyanobacteria ; Development ; Multiple fission ; Septate binary fission ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary An ultrastructural examination of cell division in two baeocyte producing cyanobacteria,Pleurocapsa minor andDermocarpa violaceae, reveals two distinct patterns of binary (transverse) fission. Septate binary fission, inPleurocapsa minor, involves centripetal synthesis and deposition of the mucopolymer cell wall layer (L 2). The ingrowth of the cytoplasmic membrane and L 1 cell wall layer, along with the synthesis of the L 2 cell wall layer, results in the formation of a prominent septum. Partitioning of the cell occurs by the constriction of the outer cell wall layers (L 3 and L 4) through the septum. InDermocarpa violaceae, constrictive binary fission occurs by the simultaneous ingrowth or constriction of the cytoplasmic membrane and all cell wall layers (L1, L2, L3, L4). Septate and constrictive binary fission may proceed symmetrically (medially) or asymmetrically (nonmedially). Multiple fission occurs regularly inDermocarpa violaceae and provides for a rapid means of reproduction when compared to binary fission. Successive radial and tangential divisions of the protoplast result in formation of many small daughter cells (baeocytes). The process of multiple fission is similar to septate binary fission with reduced septa being formed. However, constriction of the outer cell wall layers, through the septa, proceeds concurrently with septum formation.
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  • 58
    ISSN: 1615-6102
    Keywords: Cold acclimation ; Exocytotic extrusions ; Freeze-fracture ; Isolated rye protoplasts ; Lipid bodies ; Osmotic contraction ; Plasma membrane ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Osmotic contraction of protoplasts isolated from cold acclimated leaves ofSecale cereale L. cv. Puma results in the formation of exocytotic extrusions of the plasma membrane. Numerous knobs or polyps were observed on the surface of the protoplasts with scanning electron microscopy. In thin sections, the extrusions were bounded by the plasma membrane with a densely osmiophilic interior. Cross-fracturing of the extrusions revealed aparticulate bodies within, a further indication that the interior of the extrusions was predominantly lipid material. Freeze-fracture of the plasma membrane suggests a possible source of this lipid material. Following osmotic contraction, the particle density on the plasma membrane protoplasmic face (PFp) increased, being reflected in both a substantial increase in paracrystalline arrays and an increase in the particle density in non-crystalline regions. This increase in particle density indicates that lipid material is preferentially lost from the plasma membrane during contraction. The density on the exoplasmic face (EFp) did not change. Together, these findings suggest that during hypertonic contraction of acclimated protoplasts, lipid material is preferentially subducted from the plasma membrane and sequestered into lipid bodies (the osmiophilic regions). The formation of lipid bodies and extrusions was readily reversible. Following osmotic expansion of acclimated protoplasts, the extrusions were retracted back into the plane of the plasma membrane.
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  • 59
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    Plant systematics and evolution 146 (1984), S. 145-162 
    ISSN: 1615-6110
    Keywords: Chlorophyceae ; Spermatozopsis similis ; Ultrastructure ; green flagellate ; flagellar apparatus ; function ; phylogeny
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ultrastructure of the flagellar apparatus of the naked, biflagellate green algaSpermatozopsis similis Preisig & Melkonian has been studied in detail using an absolute configuration analysis. The two basal bodies are displaced by 350 nm in the 1/7 o'clock direction and do not overlap proximally. They are interconnected by a principal distal connecting fibre consisting of a bundle of 5–8 nm filaments and possibly two proximal striated connecting fibres. The flagellar root system is cruciate (5-2-5-2 or 4-2-4-2 system) and contains a prominent continuous system I fibre overlying the two opposite two-stranded roots. A system II fibre is absent. Pronounced structural differences have been observed in the flagellar apparatus ultrastructure at two types of flagella orientation: During backward swimming basal bodies are parallel, the distal connecting fibre is extremely contracted; during forward swimming basal bodies assume various angles (from 20° to 180°) and the connecting fibre is about five times longer compared to the contracted state. The function of the connecting fibre as a contractile organelle and the mechanism of its contraction are discussed. On the basis of the flagellar apparatus ultrastructure,Spermatozopsis similis is related toChlamydomonas-type green algae.
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  • 60
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    Cell & tissue research 237 (1984), S. 123-129 
    ISSN: 1432-0878
    Keywords: Pancreas, exocrine (rat) ; Ultrastructure ; Morphometry ; Development, ontogenetic ; Zymogen granules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Pancreatic acinar cells of rats obtained at 1,2, 3, 5, 7 and 14 days of age were examined using fine structural and morphometric techniques. From 5 days of age onwards, the acinar cells were analysed twice per day, at 20.00 h and 08.00 h. The present study demonstrates changes in the average volume of the cell, nucleus and cytoplasm, and volume densities of various cytoplasmic organelles during the first two weeks after birth. During early postnatal life, the volume density of rER increases, whereas that of zymogen granules decreases. From 5 days of age onwards, the volume densities of these two organelles differ significantly at 20.00 h and 08.00 h. During the first 2–3 days after birth, inclusion body-like structures appear in the cytoplasm of acinar cells; they contain aggregated zymogen granules and, sometimes, amorphous structures or cytoplasmic organelles. These structures also occur in interstitial cells and cells located in the intercalated region between acinar and ductal epithelial cells. Serum level of α-amylase activity is high at birth, compared with other stages during the first three weeks. Degenerating acinar cells and cell debris can be seen in the acinar and ductal lumina during these stages, a feature suggesting holocrine secretion. Cellular polarity appears to be incomplete during the first two or three days after birth.
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  • 61
    ISSN: 1432-0878
    Keywords: Epididymis (marsupials) ; Ultrastructure ; Sperm maturation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ductus epididymidis of the tammar is lined by an epithelium composed of principal, mitochondria-rich, apical and basal cells, and intraepithelial leucocytes. The epithelium is structurally differentiated into 6 zones referred to as the initial segment, middle segment (3 subdivisions) and terminal segment (2 subdivisions). The occurrence of the initial, middle and terminal segments corresponds quite closely to the anatomical differentiation of the epididymis into a head, body and tail. The initial segment epithelium in the tammar is lower and has shorter and more slender stereocilia than in other mammals which have been described. Otherwise, the structure of the epithelium has similar characteristics in the tammar to that described in other mammals. Spermatozoa begin to develop the capacity for motility within the initial segment, but only show structural signs of maturation in the middle segment. The sperm head rotates through 90 degrees in the proximal subdivision of the middle segment. The cytoplasmic droplet is detached and spermatozoa develop the capacity for motility in the middle subdivision of the middle segment. The cytoplasmic droplets are phagocytosed by the epididymal epithelium of the middle segment. Sperm storage appears to be the main function of the terminal segment.
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  • 62
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    Cell & tissue research 238 (1984), S. 497-502 
    ISSN: 1432-0878
    Keywords: D2 glycoprotein ; Adrenal gland ; Immunocytochemistry ; Ultrastructure ; Cell adhesion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructural localization of the glycoprotein D2 in rat adrenal gland was investigated using immunohistochemical methods, and D2 localization in cultures of adult bovine chromaffin cells was studied by immunofluorescence. D2 was found to be situated on nerve fibers passing through the adrenal cortex and in the medulla zone, and also on the surface of all chromaffin cells. In addition, it was strongly expressed on the surface of glial (Schwann) cells. Cortical cells were unreactive to the antiserum. In cultures, all adrenalin and noradrenalin [dopamine-β-hydroxylase (DBH)-positive] cells were surface labelled for D2. A less frequent second cell type was recognized in vitro which was DBH negative but D2 positive. Such cells were presumed to be Schwann cells. These data are discussed in terms of the developmental origin of the cells and with regard to the putative functional rôle of D2 in cell adhesion phenomena.
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  • 63
    ISSN: 1432-0878
    Keywords: Lymphocytes ; Phytohemagglutinin stimulation ; Nucleolar organizer region ; Three-dimensional reconstruction ; Ultrastructure ; Guinea pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructural changes in the spatial organization of nucleolar DNA in lymphocytes during phytohemagglutinin (PHA) stimulation was studied in guinea pigs by means of oxidized diaminobenzidine (DAB) at low pH as a differentially contrasting stain for nucleic acids and by the use of reconstruction of serial sections. The extended DNA filaments situated inside the fibrillar area originate from a large aggregation of heterochromatin, which is closely associated with the nucleolus, and from the perinucleolar shell of condensed chromatin. It is suggested that these two distinct regions of chromatin might be associated with different functions.
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  • 64
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    Cell & tissue research 235 (1984), S. 309-318 
    ISSN: 1432-0878
    Keywords: Ascidian ; Gut ; Cell involution ; Ultrastructure ; Phagocytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Degenerative changes in the digestive tract of zooids of Botryllus schlosseri were studied by light and electron microscopy. Three main processes occurred in the tissues: contraction, involution and phagocytosis. The contraction of epidermis and peribranchial epithelium in which cytoplasmic microfilaments probably participate, seemed to have a special role in compressing the underlying organs. During contraction most of the body cavities collapsed, the branchial walls disintegrated and the fragments were rapidly taken up by large phagocytes. The gut epithelium retained its apparent continuity longer, though isolated phagocytes infiltrated it to eliminate single cells. Cell degeneration came about chiefly either through swelling and lysis of cells or through loss of water and condensation of cytoplasm and nucleus. The fate of all regressed tissues was to be engulfed and digested by wandering phagocytes. However, it was also observed that numerous cells of different epithelia could act as fixed phagocytes by engulfing cell debris and entire cells into heterophagic vacuoles.
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  • 65
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    Cell & tissue research 235 (1984), S. 295-301 
    ISSN: 1432-0878
    Keywords: Tfm/Y mouse ; Submandibular gland ; Sexual ; dimorphism ; Androgens ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fine structure of the submandibular gland of the mouse with testicular feminization (Tfm/Y) was studied by light and electron microscopy. The architecture of the Tfm/Y gland proved to be rather similar to that of the normal female mouse in both tubular ratio and structure. Granular convoluted tubular cells in Tfm/Y mice characteristically had fewer secretory granules and increased cytoplasmic vacuoles than normal littermates, suggesting an altered synthesis of secretory granules in this cell type of the Tfm/Y mouse. Moreover, there were differences in the ultrastructure of submandibular glands between Tfm/Y and normal female mice. In the gland of the Tfm/Y mouse, basal striations of the striated secretory tubular cells were not so developed and granular intercalated duct cells were less than those of normal females. These findings support the evidence that the secretory tubule of the mouse submandibular gland responds to androgens, resulting in accentuated development in the male, while also suggesting the possibility that the mouse submandibular gland is regulated by other factors which lead to the prominent sexual dimorphism observed in this gland.
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  • 66
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    Cell & tissue research 235 (1984), S. 691-693 
    ISSN: 1432-0878
    Keywords: Plasma cells ; Ultrastructure ; Immunology ; Myxinoids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Hagfishes, the most primitive vertebrates, are of special interest for the evolution of immune responses. Eptatretus stoutii, the Pacific hagfish, is able to mount cellular and humoral immune responses but all attempts to demonstrate in them the presence of plasma cells have failed. In the present study we demonstrate for the first time plasma cells identifiable by ultrastructural criteria in the pronephros, a primitive lymphohaemopoietic organ, of Myxine glutinosa, the Atlantic hagfish.
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  • 67
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    Cell & tissue research 236 (1984), S. 171-180 
    ISSN: 1432-0878
    Keywords: Immunocytochemistry ; Ultrastructure ; Supraoptic nucleus ; Neuropil ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The neuropil located ventral to the SON was investigated by the use of immunoperoxidase staining for neurophysins, oxytocin and vasopressin, and electron miroscopy. The study was performed in six groups of rats: 1) control; 2) infusion of isotonic saline into the CSF; 3) infusion of hypertonic saline into the CSF; 4) drinking hypertonic saline for 4 days; 5) same as group 4 but injection of colchicine into the CSF on second day of dehydration; 6) salt loading for 3 months. In the control rats the ventral neuropil contained a few immunoreactive processes, the general morphology of which was completely different from that of the neurosecretory axons emerging from the SON at its dorsal aspect. In rats of groups 3 to 6 the ventral processes (VP) became loaded with neurosecretory granules, whereas the perikarya and axons were depleted. Based on their general morphology and reactivity pattern it is suggested that the VP are dendrites. Most of these “dendrites” were embedded in a glial cushion formed by the processes of a particular type of marginal glia. Some of these “dendrites” enveloped an arteriole penetrating the optic tract. All VP were rich in synaptic contacts. The possibility that the VP of neurosecretory cells may be functionally related to the subarachnoid CSF and the arteriolar blood flow is discussed.
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  • 68
    ISSN: 1432-0878
    Keywords: Peripolar cells ; Juxtaglomerular apparatus ; Newborn sheep ; Dexamethasone ; Ultrastructure ; Cytoplasmic granules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In the renal juxtaglomerular region of newborn sheep, it was found that glomerular peripolar cells and their granules were very much larger than those found in fetal lambs or adult sheep. Similar peripolar cell hypertrophy was triggered in fetal lambs treated in utero with intraperitoneal injections of dexamethasone. Ultrastructurally, granules of peripolar cells from newborn lambs resembled closely the enlarged zymogen granules described in the pancreas of newborn rats. Such peripolar cell hypertrophy may reflect a functional adaptation of the kidney to immediate postnatal life.
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  • 69
    ISSN: 1432-0878
    Keywords: Development ; Enterocytes ; Fish ; Mitosis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The processes of proliferation, cell division and differentiation of intestinal epithelial cells have been studied during development of the fish, Barbus conchonius. On the 3rd day, nearly all cells of the presumptive gut proliferate. Once the intestinal epithelium begins to differentiate, a decreasing percentage of proliferative cells can be found. On the 7th day, when intestinal folds start to develop, the proliferative cells become restricted to the future basal parts of the folds. Ultrastructural examination of 3H-thymidine-labeled cells and mitotic cells of 6-day-old larvae shows that functional enterocytes are proliferative. The same feature is suggested for older fish. Proliferating undifferentiated “dark” cells, characterized by many free ribosomes and a few organelles, are also present in the intestinal epithelium of larval fish; they are considered to be stem cells, mainly for goblet cells. Proliferating goblet cells and enteroendocrine cells were not observed. The latter cell type is scarce and has a long turnover time. A common feature of all these dividing cells is the presence of isolated spherical to cylindrical lamellar structures which may have lost contact with the cell membrane during prophase; they probably regain this contact by fusion with the cell membrane at the end of mitosis.
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    Cell & tissue research 236 (1984), S. 393-397 
    ISSN: 1432-0878
    Keywords: Smooth muscle ; Salamander, Amphiuma ; Ultrastructure ; Stereology ; Volume: surface area ratio
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary An ultrastructural and stereological examination was performed on stomach smooth muscle of the salamander Amphiuma. This tissue has very large cells, ranging up to 12×1500 μm when relaxed. The extracellular space is 31% of the tissue volume, and the tissue contains 84.6% water. These values are similar to those of other amphibian and mammalian gastrointestinal smooth muscle. The cells possess the usual smooth muscle organelles. Thick, thin and intermediate filaments are present, along with membrane-associated and cytoplasmic dense regions. There is a well-developed sarcoplasmic reticulum and many microtubules. Caveolae are found in rows along the cellular surface; the caveolae increase the cellular surface area by about 70%. The ratio mean volume: surface area of the cells is 1.26 μm. This tissue appears to be typical of gastrointestinal smooth muscle, with the exception of the very large size of the cells.
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    Cell & tissue research 237 (1984), S. 277-284 
    ISSN: 1432-0878
    Keywords: Swimbladder ; Teleost ; Cholinergic nerves ; Adrenergic nerves ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The general structure, ultrastructure and innervation of the swimbladder of the smooth toadfish, Tetractenos glaber, were examined with light-microscopic, fluorescence-histochemical, and transmission electron-microscopic techniques. The structure of the swimbladder is similar to that of other euphysoclists. Fluorescence histochemistry showed adrenergic fibres in both the secretory and resorptive areas of the swimbladder. Transmission electron microscopy revealed two morphologically distinct axon profiles type-I profiles containing many small, flattened vesicles; type-II profiles containing both large, granular vesicles and rounded, small clear vesicles in varying proportions. The gas-gland cells and surrounding muscularis mucosae are innervated by both type-I and type-II fibres. Type-I fibres also innervate pre-rete arteries. The rete- and gas-gland capillaries do not appear to be innervated. Arteries running to the resorptive area are innervated by type-I fibres. Both type-I and type-II profiles make contact with the muscularis mucosae in the resorptive area. Only type-I fibres innervate the radial dilator muscle in the oval sphincter region, whereas only type II fibres innervate the circular muscle of the oval sphincter. Type-I fibres took up α-methyl-noradrenaline, and could not be found after pre-treatment with 6-hydroxydopamine. They are, therefore, assumed to be adrenergic. Type-II fibres were tentatively identified, by exclusion, as cholinergic.
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  • 72
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    Cell & tissue research 237 (1984), S. 537-547 
    ISSN: 1432-0878
    Keywords: Scale ; Regeneration ; Ultrastructure ; Cichlid ; Hemichromis bimaculatus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Scale regeneration has been studied in Hemichromis bimaculatus. The removed scale, which serves as a control, is covered by its surrounding scleroblasts as can be seen with scanning electron microscopy. Subsequently, during regeneration, a population of scleroblasts arises in the empty dermal pocket as shown with transmission electron microscopy. At first, an elongated papilla of regeneration forms, probably from the differentiation of dermal fibroblasts. A scale anlage composed of the osseous layer appears in the middle of the papilla, which becomes a regenerating bag. All the surrounding large scleroblasts are involved in scale formation, although later three populations of scleroblasts specialize according to their location around the scale. Superficial scleroblasts flatten when the final thickness of the osseous layer of the scale is attained; the deep scleroblasts are responsible for the formation of the basal plate whereas marginal scleroblasts increase the diameter of the osseous layer of the scale. During scale regeneration, scleroblasts are more numerous and larger than during scale ontogenesis. In particular, deep scleroblasts form a columnar epithelium when the basal plate is laid down, a feature which is not found during scale ontogenesis. Moreover, the regenerated basal plate exhibits an orthogonal “plywood” arrangement that is never seen in the embryonic scale where the “plywood” is of the intermediate type.
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  • 73
    ISSN: 1432-0878
    Keywords: Pituitary gland, pars anterior (distalis) ; Gonadotrops ; Thyrotrops ; Ultrastructure ; Immunolabeling ; Teleosts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Pituitaries of the African catfish (Clarias lazera) were studied with immunocytochemical methods, at the light-microscopic and ultrastructural levels, for the characterization and localization of gonadotropic and thyrotropic cells. Two immunostaining procedures with the use of different markers were carried out: (i) with peroxidase-antiperoxidase, (ii) with protein A-gold. In routinely stained sections for light microscopy two types of basophils were identified in the proximal pars distalis: (1) large, round, purple cells, and (2) small, angular, light-blue cells. Both types were immunolabeled with antibodies against Clarias α,β-gonadotropin (GTH) and salmon G100-GTH. Only the large basophils were immunolabeled with anti-carp β-GTH, whereas the small basophils were the only cells immunolabeled with anti-human thyrotropin beta subunit (anti-h TSH-β). It was concluded that the large basophils represent the gonadotrops and the small basophils the thyrotrops. At the ultrastructural level the immunostaining of the GTH-cells was confined to three types of inclusions: (i) secretory vesicles, (ii) globules, and (iii) electron-dense, membrane-bound irregular masses. Especially the protein A- gold method, in combination with the use of a highly diluted homologous antiserum, resulted in a distinct localization of GTH. The presence of two types of nerve fibres, synaptically contacting the gonadotrops, is discussed with regard to the presence of a peptidergic (stimulatory) and an aminergic (inhibitory) control of GTH-secretion.
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  • 74
    ISSN: 1432-0878
    Keywords: Peptidergic neurotransmission ; Lymnaea stagnalis ; Immunocytochemistry ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Three neuronal systems of the pond snail Lymnaea stagnalis were immunocytochemically investigated at the ultrastructural level with the unlabeled peroxidase-antiperoxidase technique. Preliminary electrophysiological and cell-filling investigations have shown that a cluster of neurons which reacts positively with an antiserum against the molluscan cardio-active peptide FMRFamide, sends axons to the penis retractor muscle. In this muscle anti-FMRF-amide (aFM) positive axons form neuro-muscular synapses with (smooth) muscle fibers. The morphological observations suggest the aFM immunoreactive system to be involved in peptidergic neurotransmission. In the right parietal ganglion a large neuron (LYAC) is penetrated by aFM positive axons which form synapse-like structures (SLS) with the LYAC. The assumption that the SLS represent the morphological basis for peptidergic transmission is sustained by the observation that iontophoretical application of synthetic FMRFamide depolarizes the LYAC. The axons of a group of pedal anti-vasopressin (aVP) positive cells run in close vicinity to the cerebral ovulation (neuro-)-hormone producing cell system (CDC system) Synapses or SLS between the two systems were not observed. The fact that (bath) application of arg-vasopressin induces bursting in the CDC, may indicate that the vasopressin-like substance of the aVP cells is released non-synaptically.
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  • 75
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    Cell & tissue research 238 (1984), S. 565-575 
    ISSN: 1432-0878
    Keywords: Pineal organ teleost ; Tissue culture ; Ultrastructure ; Indoles ; High performance liquid chromatography (HPLC)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructure and biochemistry of the goldfish pineal organ were examined in expiants cultured for 1, 3, and 6 days. All four cell types (photoreceptor, supportive, ganglion, phagocytic) were identified; they exhibited many of the characteristics of these cells in vivo. Exceptions included a gradual disorganization of the outer segments and reduction of synaptic ribbons in photoreceptors with time in culture. In addition, there was a marked proliferation of endoplasmic reticulum in both photoreceptor and supportive cells. The indoles 5-hydroxytryptophan, serotonin, 5-hydroxyindoleacetic acid, 5-methoxytryptophol, and melatonin were separated in expiants by high performance liquid chromatography using electrochemical detection. Serotonin levels could be depleted by p-chlorophenylalanine and elevated by nialamide or by adding 5-hydroxytryptophan to the culture medium. These findings suggest that organ culture may be a useful model for study of regulatory processes related to the photoneuroendocrine functions of the teleost pineal organ.
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  • 76
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    Cell & tissue research 238 (1984), S. 621-626 
    ISSN: 1432-0878
    Keywords: Catecholamines ; Pituitary innervation ; Radioautography ; Ultrastructure ; Goldfish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The monoaminergic innervation of the goldfish pituitary gland was studied by means of light- and electronmicroscopic radioautography after in vitro administration of 3H-dopamine. The tracer was specifically incorporated and retained by part of the type-B fibers innervating the different lobes of the pituitary. In the rostral pars distalis labeled fibers were most frequently observed in contact with the basement membrane separating the neurohypophysis and the adenohypophysis. In the proximal pars distalis and the pars intermedia, labeled profiles were detected in the neural tissue and in direct contact with the different types of secretory cells. According to the previous data concerning the uptake and retention of tritiated catecholamines in the central nervous system, it is assumed that the labeled fibers are mainly catecholaminergic (principally dopaminergic). This study provides morphological evidence for a neuroendocrine function of catecholamines in the goldfish.
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  • 77
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    Cell & tissue research 238 (1984), S. 635-642 
    ISSN: 1432-0878
    Keywords: Liver ; Endothelium ; Kupffer cells ; Peroxidase ; Cytochemistry ; Ultrastructure ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Rat liver fixed by perfusion with low glutaraldehyde concentrations was incubated in diaminobenzidine-containing medium to stain for peroxidase. Endogenous peroxidatic activity was found not only in Kupffer cells but also in the endothelial cells lining the sinusoids and central veins. The reaction product was localized in the nuclear envelope and endoplasmic reticulum. The peroxidatic activity in endothelial cells showed a concentration-dependent sensitivity to glutaraldehyde: in liver samples fixed with 0.25% glutaraldehyde, approx. 23% of the sinusoidal endothelial cells and 65% of central vein endothelium were peroxidase-positive; with 0.5% glutaraldehyde, only approx. 8% of the sinusoidal endothelial cells contained detectable amounts of the reaction product; with 1.5% glutaraldehyde all endothelial cells were consistently peroxidase-negative. No peroxidatic activity could be found in liver endothelial cells following isolation by centrifugal elutriation. Endothelial cell peroxidase may possibly be involved in defense responses of liver and/or, as a part of prostaglandin synthase system, in prostanoid production.
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  • 78
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    Cell & tissue research 235 (1984), S. 347-356 
    ISSN: 1432-0878
    Keywords: Blastocyst ; Ultrastructure ; Pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Between days 8 and 11 of pregnancy spherical blastocysts from 0.3 to 10 mm in diameter were flushed from the uterine horns of Dutch Landrace pigs. A description of their ultrastructure is given, and the uptake of horseradish peroxidase and ferritin is demonstrated. The ultrastructure of the trophoblast was similar at all ages studied. The trophoblast which has many apical microvilli is able to take up and digest the macromolecules which were offered in the in vitro incubation medium. The hypoblast consists of flattened cells. In blastocysts 2 mm and larger, compact cells bearing microvilli are found below the embryoblast. Cell organelles indicating protein synthesis are found within hypoblast cells of such blastocysts. In the embryoblast, local concentrations of cell organelles are visible, indicating that differentiation has started. After the disappearance of Rauber's layer, which takes place when the blastocyst reaches a diameter of about 2 mm, superficial embryoblast cells develop short microvilli. The cells do not absorb ferritin or peroxidase but are dependent on the trophoblast for their food requirements. All cell layers in the blastocyst contain mitochondria that have characteristics of those found in steroidproducing cells. The significance of the uptake and digestion of macromolecules by trophoblast cells, the synthesis of protein by hypoblast cells and the possible synthesis of steroids is discussed with respect to the relationship between the cell layers of the blastocyst and in the context of conceptomaternal relationships.
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  • 79
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    Cell & tissue research 235 (1984), S. 463-466 
    ISSN: 1432-0878
    Keywords: Endocytosis ; Kidney (rat) ; Proximal tubule ; Apical vacuoles ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Following perfusion fixation of the rat kidney with glutaraldehyde the proximal tubule cells display small apical vacuoles, large apical vacuoles, and apical vacuoles in which a part of the limiting membrane is invaginated into the vacuole. These invaginated apical vacuoles occur more frequently in proximal convoluted tubules than in proximal straight tubules. One tubular cell may contain apical vacuoles of different sizes and stages of invagination, ranging from larger vacuoles with a wide lumen and a small area of invaginated membrane to smaller elements with no apparent lumen and a large area of invaginated membrane. Invaginated apical vacuoles lie either singly in the cytoplasm or close to the membranes of other apical vacuoles, but never in contact with the cell membrane or the membranes of lysosomes, endoplasmic reticulum, Golgi apparatus, mitochondria and peroxisomes. These findings suggest that the invaginated apical vacuoles are not fixation artifacts, but rather develop in living state in cells of the proximal tubule from spherical endocytotic elements.
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  • 80
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    Cell & tissue research 236 (1984), S. 87-97 
    ISSN: 1432-0878
    Keywords: Iodination ; Membrane shedding ; Peroxidase ; Thyroid follicle cell ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Clusters of luminal dense bodies, limited by a triple-layered membrane, were found in all follicle lumina in thyroid glands of mice. After thyroxine treatment the number of luminal dense bodies increased, especially in the periphery of the lumen, where the intraluminal bodies often displayed a striking resemblance to microvilli. In hyperplastic goiters, obtained by feeding mice with propylthiouracil, luminal dense bodies were replaced by intraluminal vesicles. During goiter involution the vesicles were gradually replaced by luminal dense bodies; the presence of intermediate forms suggests that vesicles and dense bodies are basically the same formations. Luminal dense bodies were observed in colloid droplets indicating their removal by endocytosis. As demonstrated by electron-microscopic cytochemistry, luminal dense bodies contain a membranebound peroxidase, and electron-microscopic autoradiography after administration of 125I indicate that they possess an iodinating capacity. Our observations on mouse thyroid glands suggest that the luminal dense bodies, which appear as vesicles in hyperplastic glands, are formed by shedding of the apical plasma membrane of the follicle cell. The shedding process might be of importance for the turnover of plasma-membrane material.
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  • 81
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    Cell & tissue research 236 (1984), S. 365-372 
    ISSN: 1432-0878
    Keywords: Skeletal muscles ; Myofibrils ; Ultrastructure ; Exertion ; Man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fine structure of muscle fibres from m. vastus lateralis of nine healthy males (mean age 26 years) was investigated. Four individuals constituted non-exercised controls while five subjects participated in a two-months eccentric muscular training program. Specimens from the controls showed a well-preserved, regular myofibrillar band pattern while changes in the myofibrillar architecture were constantly found in specimens taken after the training program. These changes consisted of Z-band alterations, Z-bands being out of register, extra sarcomeres, Z-band extensions and bisected Z-bands. Between the separated Z-band halves, thin and thick myofilaments as well as abundant glycogen particles and/or ribosomes, were observed. Type-2 (fast-twitch) fibres were predominantly affected. Contrary to the controls the trained individuals constantly showed a greater variation in sarcomere lengths in Type-2 fibres than in Type-1 fibres. It is concluded that muscular work of high tension can induce fine-structural alterations. When repeated over a long period of time, extreme tension demands seem to initiate reorganization in the muscle fibres, predominantly in the, ultrastructurally defined, Type-2 fibres. This adaptation probably results in a better stretchability of the muscle fibres, reduces the risk for mechanical damage and brings about an optimal overlap between actin and myosin filaments.
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  • 82
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    Cell & tissue research 236 (1984), S. 339-343 
    ISSN: 1432-0878
    Keywords: Moulting ; Mechanosensory hair ; Chordotonal organ ; Ultrastructure ; Crustacea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fine structure of hair mechanoreceptors in crayfish during moulting was investigated with special attention to the interface apparatus between cuticular hairs and sensory cells: the chorda. The chordae are lost with old exuviae at every moulting. They are drawn out from a moulting canal at the tip of the new hair. The chordae are regenerated from a material secreted by sheath cells after moulting. Therefore, the chorda is an inward projection of the cuticular exoskeleton, and it has direct contact with the sensory element, the scolopidium. The scolopidium has been found in both hair mechanoreceptors and subcuticular chordotonal organs in crustaceans, and is thought to be a primitive type of mechano-sensory transducing element. The present observation gives additional evidence for the homology of two sensory elements in arthropods, i.e., the cuticular hair sensilla and subcuticular chordotonal organs.
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  • 83
    ISSN: 1432-0878
    Keywords: Ultrastructure ; Autoradiography ; Oocytes ; Nucleolus-like bodies ; Teleost
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Cytoplasmic granulo-fibrillar masses, usually termed nucleolus-like bodies (NLB) or nuages, have been described in several different cell types. They are sometimes associated with a mitochondrial arrangement, this association often being marked during certain phases of the oocyte cycle. In Xiphophorus helleri, NLB consist of fibrillar and granular material that gradually becomes more granular during meiotic prophase I, and is associated with mitochondrial arrangements during diplotene and dictyate of meiosis. Autoradiographic studies of uridine incorporation into the nucleolus and subsequently into NLB suggest that the latter represent a reserve of ribonucleoproteins that is later used in ribosomal maturation during vitellogenesis.
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  • 84
    ISSN: 1432-0878
    Keywords: Subcommissural organ ; Secretory granules ; Secretory process ; Ultrastructure ; Natrix maura (Reptilia, Ophidia)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Two different types of ependymal cells were found in the subcommissural organ (SCO) of Natrix maura. Most secretory cells showed morphological features resembling the general structure and ultrastructure of cells in the SCO of other vertebrates. This report describes a second population of cells lining a portion of the dorsal groove of the SCO. These cells were not selectively stained by chromalum-hematoxylin and, under the electron microscope, they were characterized by scarce surface differentiations, sparse apical cytoplasm and short basal processes. Flat, parallel cisternae of the rough endoplasmic reticulum produced vesicles that appeared to be transported to the well-developed Golgi apparatus. Dense secretory granules about 200 nm in diameter were found in the Golgi region. Similar granules were seen in the vicinity of the apical plasma membrane; some of them opened toward the ventricle. All these characteristics clearly differentiate this cell group from the other secretory cells lining the SCO laterally and ventrally.
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  • 85
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    Keywords: Granular endoplasmic reticulum ; Ultrastructure ; Pinealocyte ; Mole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Ten or more straight tubules, each of which consists of a double unit membrane of granular endoplasmic reticulum with a cylindrical profile, are joined side by side in a raft-like configuration in the cytoplasm of the pinealocytes of Japanese moles. They measure about 60 nm and 100 nm in their inner and outer diameters, respectively, and are often partially connected to unspecialized granular endoplasmic reticulum. Cisterns held between the inner and outer unit membranes with cylindrical profiles vary from 15 nm to 30 nm in width. Ensheathed portions of the cytoplasm are contiguous with cytoplasm outside the tubular units. The inner unit membranes of the tubules bear fewer ribosomal particles than the outer ones.
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    Cell & tissue research 236 (1984), S. 431-438 
    ISSN: 1432-0878
    Keywords: Satellite cells ; Satellite fibres ; Tail muscle ; Urodela ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The incidence and ultrastructure of satellite cells in the tail muscles of urodelan larvae were examined during development during which the number of satellite cells is gradually reduced. They are found more frequently in red than in the white fibres in all four stages examined (stage 53, 64, 66+ and juvenile). As development proceeds, intercellular space between satellite cell and muscle fibre is in general gradually extended and is mostly filled with basal lamina. Small muscle cells, satellite fibres, which are situated under the basal lamina of the parent fibre, are morphologically similar to satellite cells but contain a small amount of myofibrils. Three types of satellite fibres are distinguishable on the basis of differences in K2-EDTA-treated ATPase activity, width of Z line, and parent fibre type. Neuromuscular junctions are visible in satellite fibres.
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    Cell & tissue research 236 (1984), S. 465-470 
    ISSN: 1432-0878
    Keywords: Tendon ; Collagen fibrils ; Morphometry ; Ultrastructure ; Loading ; Mouse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary This study was designed to gain more detailed morphological information on skeletal tendons in the course of adaptation to physical loading. The effect on collagen fibrils was investigated in 6-week-old mice by means of electron microscopy. Physical loading was performed on a treadmill 5 days a week for 1, 3, 5, 7 and 10 weeks. Morphometric analysis of collagen fibrils revealed the mean diameter, the diameter distribution, the number and the cross-sectional area. The principal observations included: 1. After one week of physical loading an increase in mean fibril diameter (30%, p≦0.01), in number (15%, p≦ 0.05), and in cross-sectional area (15%, p≦0.05), as well as a change in mean fibril diameter distribution. 2. From the third to the seventh week a fall under the level of the controls in mean diameter (26%, p≦0.01), in number (26%, p≦0.01), and a reduced cross-sectional area (17%, p≦0.01), accompanied by signs of splitting of individual collagen fibrils. 3. In the long-term study an increase in fibril number (29%, p≦0.01), a fall in mean diameter from 189 nm in the controls to 179 nm (p≦0.05) but no statistically significant change in the relative cross-sectional area (32%) per unit in comparison to unloaded tendons. The possible physiological implications of the findings are discussed in the light of several regulatory mechanisms known to appear during the course of physical loading in connective tissues.
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    Cell & tissue research 236 (1984), S. 619-628 
    ISSN: 1432-0878
    Keywords: Gastrotricha, freshwater ; Sperm, reduced ; Ultrastructure ; Spermatogenesis ; Temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Spermatogenesis and spermiogenesis in Lepidodermella squammata are confined to the postparthenogenic phase of the life cycle and coincide with developmental changes in the bilateral female gonads. Male stages are bilateral but asynchronous, in the lateral abdomen anterior to the female gonads. Maximum observed sperm production is two packets per side, or 64 sperm. Sperm formation occurs more rapidly at 27° C than at 20° C (p〈0.001), requiring as little as 1 day. Two spermatogonial mitotic divisions produce a clone of four primary spermatocytes connected by bridges (stage 1). Centrioles are absent. Development occurs within a cyst. Meiotic divisions produce 16 spermatids (stage 2), each containing a dense, elongate, tapered nucleus. Cytoplasmic membranes enclose one end of the nuclear rod, excluding all other organelles. Completion of this process results in stage 3, a packet of 16 sperm associated with one dense sphere, a modified ‘residual body’ containing cytoplasmic debris. The residual body then disappears, leaving the sperm packet of stage 4. Each mature sperm is a dense nuclear rod with surrounding membranes, lacking acrosome, mitochondrion, centrioles, and flagellum. Function of sperm has not been demonstrated. The spermatozoa are of a reduced type not previously described.
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    Cell & tissue research 236 (1984), S. 629-636 
    ISSN: 1432-0878
    Keywords: Oocytes, primary ; Gastrotricha, freshwater ; Ultrastructure ; Synaptonemal complex ; X-body
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Six small cells are present in each of the bilateral gonads of parthenogenically reproductive Lepidodermella squammata. Early in the extended postparthenogenic phase of the life history, these cells undergo limited proliferation followed by differentiation. Primary oocytes of three types are present 0.3 days after deposition of the final parthenogenic egg: small oocytes with presynaptic nuclei; intermediate oocytes with nuclei containing synaptonemal complexes; and larger oocytes with a germinal vesicle. Oocytes persist without further development at least until day four of the postparthenogenic phase. Older isolated animals may contain and even deposit an enlarged egg, but successful progeny does not result. Oocytes are located at the anterior pole of each of the bilateral gonads, adjacent to developing male tissues producing sperm. More posterior cells in the gonad are initially undifferentated in the postparthenogenic phase. Dorsal and central cells first show specialization for secretory activity, and by day four contain peripheral layers of RER and central accumulations of polymorphic secretion droplets. The posterior and ventral cells produce secretion droplets that aggregate into an enlarging bilobed structure called the X-body. Two or three cells in each gonad contribute secretions to the X-body, which is intracellular in a secondary syncytium formed by the contributing cells. Functions for the postparthenogenic gametes and for the X-body are not yet demonstrated.
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  • 90
    ISSN: 1432-0878
    Keywords: Steroids ; Vitellogenesis ; Metabolism ; Ultrastructure ; Teleosts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Estradiol injections increase serum level of calcium, amino acid, glucose, protein, ammonia and creatinine in immature Epinephelus akaara, and also increase levels of total lipid, cholesterol, phospholipid and esterified fatty acids. Hepatic protein, glycogen and lipid concentrations also rise after estradiol treatment, and some hepatic enzymes participating in the metabolism of nitrogen, lipid and carbohydrate, show increased activity. Serum vitellogenin levels are increased. Testosterone treatment increases serum protein, total lipid, cholesterol, amino acid and ammonia levels, and also hepatic glycogen content, but in contrast to estradiol treatment, testosterone does not change serum vitellogenin, glucose, calcium, phospholipid, esterified fatty acid and creatinine levels, nor the hepatic lipid and protein content. A small number of hepatic enzymes shows an increased activity. Vitellogenic fish show biochemical changes similar to that of estradiol-treated fish, but are different from those of immature fish. Estradiol treatment induces ultrastructural changes in the hepatocytes of immature fish that are similar to those found in vitellogenic fish. These include a proliferation of rough endoplasmic reticulum and Golgi apparatus, and an increase in glycogen and lipid, all indicative of enhanced metabolic activity.
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    Cell & tissue research 236 (1984), S. 677-683 
    ISSN: 1432-0878
    Keywords: Interneuron ; Synaptology ; Ultrastructure ; Horseradish peroxidase ; Helix pomatia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The morphology, axonal arborization and ultrastructure of synaptic connections of the V21 giant neuron in the visceral ganglion of the snail Helix pomatia has been investigated following intracellular labelling with horseradish peroxidase. The V21 neuron establishes several afferent and efferent axo-axonic connections, mainly along the first half of the primary axon. Collaterals of 200–300 μm length originate from the primary axon, which shows further arborization, and both afferent and efferent synaptic contacts are formed on these fine axon profiles. Afferent and efferent contacts of the cell occur within very short distances of a few micrometers. On the basis of ultrastructure and vesicle and granule content, several afferent terminals can be distinguished on V21 labelled axon profiles. The majority of these afferent terminals resembles peptidergic-(neurosecretory)-like terminals. This finding supports the possible transmitter role of neuropeptides in the central nervous system of gastropods. Our results are consistent with and provide morphological evidence for recent electrophysiological observations suggesting that, in addition to integrating input, the V21 neuron functions as an interneuron in Helix central nervous system.
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    Cell & tissue research 236 (1984), S. 693-697 
    ISSN: 1432-0878
    Keywords: Intermediate filaments ; Microtubules ; Caveolae ; Bullfrog ; Arachnoid mater ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In the bullfrog, the meninges surrounding the central nervous system include an arachnoid mater that contains layers of cells with abundant intermediate filaments (IFs) having unique organizational characteristics. This membrane contains an inner lamina of cells that resemble fibroblasts and an outer lamina of flattened cells that are almost filled with IFs. The IFs of the outer arachnoid are arranged in compact, arching bundles that lie parallel to the outer surface of the central nervous system. Thus, sections cut tangentially to the membrane reveal bending of filament bundles, whereas transverse sections do not. In some cells bordering the subdural space, bundles of filaments are organized into highly-ordered spiral arrays. Attachments to the numerous desmosomes and, apparently, to the nuclear envelope suggest anchoring of cytoplasmic structures by the IF system. Microtubules occur primarily near the plasma membrane and the nucleus. Numerous caveolae also are associated with the plasma membrane. The unusual abundance, organization, and cytoplasmic relations of IFs in the bullfrog arachnoid suggest that this membrane may serve as an important model for study of fundamental cytoskeletal relations and function.
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    Cell & tissue research 237 (1984), S. 357-362 
    ISSN: 1432-0878
    Keywords: Leydig-Sertoli cell interaction ; FSH stimulation ; Ultrastructure ; Pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Interactions between Leydig and Sertoli cells, as well as a stimulatory effect of FSH on Leydig cell activity, have been reported in many studies. In order to investigate these interactions, the ultrastructure of immature pig Leydig cells under different culture conditions has been studied. When cultured alone in a chemically defined medium, there is a marked regression of the Leydig cell smooth endoplasmic reticulum and a swelling of the mitochondria. Addition of FSH or hCG does not prevent these phenomena. Co-culturing of Leydig cells with Sertoli cells from the same animal maintains the smooth endoplasmic reticulum at the level seen in vivo and in freshly isolated Leydig cells. The addition of FSH to the co-culture stimulates its development and increases Leydig cell activity, as assessed by an increase in hCG binding sites and an increased steroidogenic response to hCG. These results suggest that Sertoli cells exert a trophic effect on Leydig cells, and that the stimulatory effect of FSH on Leydig cell function is mediated via the Sertoli cells. These results reinforce the concept of a local regulatory control of Leydig cell steroidogenesis.
    Type of Medium: Electronic Resource
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  • 94
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    Springer
    Cell & tissue research 238 (1984), S. 1-12 
    ISSN: 1432-0878
    Keywords: Lung ; Amphibia ; Ultrastructure ; Smooth muscle ; Extracellular matrix
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The lung of the giant salamander, Amphiuma tridactylum, is divided into respiratory alveoli by muscular septa that increase the surface area of the lung as well as provide a mechanism for its almost complete collapse during exhalation. The epithelium of the internal surface is of two types: respiratory, composed of a single layer of pneumocytes overlying anastomosing capillaries, and non-respiratory, composed of ciliated cells and mucus-secreting goblet cells. Non-respiratory epithelium covers the apical edges of the septa, whereas the respiratory epithelium lines the alveoli. The smooth muscle of the septa and walls of the lung was studied in preparations of uninflated and acetylcholine-contracted lung. The muscle cells are ultrastructurally similar to other types of smooth muscle but are surrounded by extraordinary amounts of extracellular matrix, containing collagen and elastic fibers and numerous fine fibrils of unknown composition. Smooth muscle in isolated lung strips contracted in a dose-dependent manner when treated with acetylcholine or methacholine; contraction was blocked by atropine. Responses of lung strips to adrenergic agents were limited; only high doses of adrenalin caused slight relaxation of previously contracted muscle. These observations support the hypothesis that contraction of pulmonary smooth muscle is responsible for the ventilatory efficiency of the lung.
    Type of Medium: Electronic Resource
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  • 95
    ISSN: 1432-0878
    Keywords: Photoperiods ; Pituitary gland, pars tuberalis ; Ultrastructure ; Phodopus sungorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Conspicuous cytological differences are found between specific secretory cells of the hypophysial pars tuberalis of Djungarian hamsters exposed to long and short photoperiods. The cells differ with respect to the shapes of perikarya and nuclei and show diverse amounts of secretory granules, lysosome-like bodies and glycogen.
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  • 96
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    Cell & tissue research 238 (1984), S. 221-230 
    ISSN: 1432-0878
    Keywords: Fiber type ; Ultrastructure ; Stereology ; Stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary When fast-twitch skeletal muscles of the adult rabbit are subjected to continuous low-frequency activity by electrical stimulation of the corresponding motor nerves, the fibers undergo an ultrastructural transformation, so that after 6 weeks they have acquired an appearance typical of slow-twitch fibers. In the present study, stimulation was discontinued at this stage in order to follow the reverse transformation, in which the fibers recovered their original morphological characteristics under conditions of normal endogenous activity. Stereological techniques were used to assess the time course of this process over a period of 20 weeks in terms of fiber cross-sectional area, extent of T-system, thickness of the Z-band, and volume fraction of mitochondria in the fiber core. Fibers of transformed muscles were smaller than those of control muscles, but the differences were no longer evident after 9 weeks of recovery. After 2 weeks the T-system was still of limited extent, as is characteristic of slow-twitch fibers; it increased toward the amount typical of fast-twitch fibers between 2 and 4 weeks, and had reached its full extent by 12 weeks. The wide Z-bands characteristic of slow-twitch fibers were retained for 4 weeks, but the thickness had begun to decrease by 8 weeks and recovery was complete by 12 weeks. The mitochondrial volume did not increase during recovery, in contrast to the large increases which had been observed to take place between 2 and 6 weeks during the fast-to-slow transformation. Overall, the recovery of fast-twitch ultrastructural characteristics was complete, but followed a more extended time course, and involved less myofibrillar disruption at an intermediate stage, than the original fast-to-slow transformation.
    Type of Medium: Electronic Resource
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  • 97
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    Springer
    Cell & tissue research 238 (1984), S. 271-288 
    ISSN: 1432-0878
    Keywords: Compound eye ; Ultrastructure ; Grass shrimp, Palaemonetes pugio ; Light adaptation ; Dark adaptation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The cone cells and corneagenous cells possess extensive networks of smooth tubular endoplasmic reticulum that may be involved in optical reflectance and light-adaptational responses, respectively. The extracellular basal lamina of the basement membrane is confluent with glial cell capillary walls and may prove to be a viaduct for the transmission of hemolymph-borne substances to the retina or of retinal degradation products to the hemolymph. In addition to dense pigment granules, the distal pigment cells are shown for the first time to contain migratory reflecting platelets that are usually polymorphic in light-adapted eyes but are rectangular in dark-adapted eyes. In the latter these plates become aligned against the crystalline cones and presumably contribute to the reflection superposition optics of the grass shrimp. Dark-adapted retinular cells possess well-developed perirhabdomal cisternae, oblong or ovoid mitochondria, generally vesicular rough endoplasmic reticulum, and occasional, spherical, calcium-like intrarhabdomal inclusions. Light-adapted retinular cells possess poorly developed perirhabdomal cisternae, lamelliform rough endoplasmic reticulum, and condensed mitochondria frequently associated with lipid droplets and pigment granules. The cytoplasmic boundaries of the reflecting pigment cells expand into the extracellular spaces between individual ommatidial retinular cells during dark adaptation and recede to the interommatidial extracellular spaces during light adaptation. Cytoplasmic microfilament bundles found only at the bases of partially light-adapted rhabdomeric microvilli may be involved in microvillar shortening.
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  • 98
    ISSN: 1432-0878
    Keywords: Innervation ; Smooth muscle ; Fish ; Kidney ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fine structure of the collecting tubules of the trout and killifish kidney was studied. These tubules are surrounded by layers of smooth muscle cells which are commonly innervated. The nerve terminals contain synaptic vesicles and, occasionally, a few dense-cored granules as well. Capillaries occur in the connective tissue space between these smooth muscle cells and the collecting tubule. Epithelial cells of the collecting tubules contain abundant mitochondria and a well developed membrane system displaying parallel arrays, and were considered to be actively involved in the transport of materials. In the trout, the collecting tubules contain peculiar cells in addition to regular tubule cells. The fine structure of these peculiar cells is highly reminiscent of that of gill chloride cells. The significance of these findings may be summarized as follows: If the smooth muscles around the collecting tubule contract under neural influence, intratubular pressure may be increased and, thus affect glomerular filtration rate. The contraction of these muscles may also cause the collapse of peritubular capillaries, affecting the transport activity of tubule cells.
    Type of Medium: Electronic Resource
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  • 99
    ISSN: 1432-0878
    Keywords: Teeth (Macropodinae) ; Enamel (opaque, translucent) ; Ultrastructure ; Enamel hardness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Teeth of three macropod species, M. giganteus, W. bicolor and P. concinna, have been studied using the techniques of light microscopy, scanning- and transmission-electron microscopy and hardness measurement. Light microscope observations showed that the teeth of these species had a translucent enamel region close to the dentine and an outer opaque enamel region at the tooth's surface. These regions were not related to the presence or absence of tubules which are a characteristic feature of marsupial enamel. Hardness tests showed that the opaque enamel was softer than the translucent enamel. Scanning electron microscope observations revealed that there was no correlation between any particular prism packing or orientation and the opaque and translucent enamel regions. Transmission electron microscope observations showed that the translucent enamel region consisted of well defined prisms and well packed, lath-like crystals, whereas the opaque enamel was disrupted by voids (which ranged in size from enlarged micropores to about 2 μm in diameter in extreme cases) between crystals and some randomly oriented, loosely packed crystals. This disruption within the opaque enamel region was more common at prism boundaries but pockets of disrupted enamel were also found within prisms and interprismatic regions. The opacity of the enamel was caused by scattering of light from the voids. The ultrastructure of the opaque enamel region indicated that this region was hypomineralized; hardness tests and polarized light microscope observations were consistent with these results.
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  • 100
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 235 (1984), S. 177-186 
    ISSN: 1432-0878
    Keywords: Retinal pigment epithelium ; Myeloid bodies ; Diurnal variation ; Morphometrics ; Ultrastructure ; Lipid metabolism ; Endoplasmic reticulum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Myeloid bodies (MBs) occur in the newt (Notophthalmus viridescens) retinal pigment epithelium (RPE) and are similar to areas of specialized endoplasmic reticulum found in a variety of other cell types. The function of these structures is unknown, although a role in lipid metabolism has been strongly suggested. Random samples from conventionally-fixed and sectioned newt RPE, obtained over a 24-hr cycle (LD 12∶12), were examined by electron microscopy. Myeloid bodies appear as stacks of flattened endoplasmic reticulum-associated saccules which increase in length and number as the RPE accumulates shed outer segment material, prior to increase in the amount of stored lipid. Associations of MBs with the nuclear envelope can be related to this increased length. Myeloid bodies decrease numerically in the cell as phagosomes are removed from the cytoplasm, but a decrease in mean sectional MB area, seen in the light phase, is counteracted in darkness where individual MBs are larger than those found in the light. The total sectional area of MBs within a cell and their mean length varied depending on the lighting condition; differences were also found between eyes after extended periods of continuous light and dark. Ribosomes were found in association with the surfaces of both flattened and circular MBs, but they were consistently more densely associated with the shorter concave surfaces of curved regions. A new hypothesis for MB function is presented, which is concerned with their role in isolating toxic lipids such as retinoids, which are accumulated during phagocytosis of shed outer segment tips, and which are capable of disrupting membrane-bound systems necessary for their eventual metabolism and safe storage.
    Type of Medium: Electronic Resource
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