The lateral recess of the third ventricle in teleosts: An electron microscopic and golgi study

Summary The ependyma lining the lateral recess of the third ventricle of the teleost inferior lobe has been studied by light and electron microscopy, including Golgi impregnation methods. As many as five different cell types appear to line the ventricle, but some of these may be similar cells in different stages of activity. One cell type contains small dense-cored vesicles and appears to have processes extending into deeper portions of the lobe. Golgi preparations reveal subependymal cells with apical processes extending to the ventricle and basal extensions which may reach the pial surface. The present observations are discussed in relation to similar studies in other fishes, amphibians and mammals. Possible functions for the various cells observed are suggested.     

Aspects of the dimorphism of Histoplasma farciminosum: a light and electron microscopic study.

Within 48h following the induction of mycelial to yeast-like phase conversion of Histoplasma farcininosum, randomly occurring hyphal cells were observed to contain multiple nuclei and markedly increased numbers of mitochondria. Yeast-like cells arose as buds from swollen tips of terminal hyphae, as sessile buds along the hyphae, and as buds from chlamydospores. Yeast-like cells were characterized by the presence of numerous buds over the surface of the mother cell. Bud scars were evident in the cell wall of the mother cell following abscission of the bud cell. Little similarity was noted between the fine structure of yeast-like H. farciminosum and that reported for H. capsulatum. The yeast-like cells of H. frciminosum underwent rapid transformation to the mycelial phase at 25 degrees C. The hyphal cell wall originated from the inner layer of cell wall of the yeast-like form. The cytoplasm of the hyphal cell usually contained a single nucleus, scattered mitochondria and occasional lipid storage bodies. Occasionally, Woronin bodies were observed at the septal pore.     

Transmission and scanning electron microscopic study of adepidermal granules of teleosts and amphibia

Summary Granules in the adepidermal space of larvae of Salmo irideus, Hynobius tokyoensis and Rhacophorus buergeri, were observed by transmission and scanning electron microscopy. Adepidermal granules of S. irideus were smooth and spherical structures, those of H. tokyoensis were smooth and spherical, or oval, while in R. buergeri these granules appeared as single or grouped tangled strand-like or starfish-like structures under the scanning electron microscope. These adepidermal granules were spread all over the basal lamina in every animal investigated. The different sizes of adepidermal granules of S. irideus and H. tokyoensis seen under the transmission electron microscope are not the result of differently sectioned faces of granules, but the granules themselves exhibit different sizes. The probable functions of these granules are discussed.     

The atrioventricular node and bundle in the ferret heart: a light and quantitative electron microscopic study.

The cells of the atrioventricular (AV) junction in the ferret heart were examined using light microscopy, a wax-model reconstruction and quantitative electron microscopy to determine their organization and characteristics. A series of subdivisions of the specialized tissues of the AV junction was apparent at both the light and electron microscopic levels. A transitional zone was observed interposed between the atrial muscle cells and the AV node. The AV node consisted of a coronary sinus portion, a superficial portion and a deep portion. The AV bundle had a segment above the anulus fibrosus, a segment which penetrated the right fibrous trigone, a non-branching segment below the anulus fibrosus and a branched segment. At the ultrastructural level the AV junctional conduction tissues had fewer irregularly oriented myofibrils than did working atrial myocardial cells. T-tubules, present in atrial muscle cells, were not observed in the modified muscle cells of the AV node and bundle. Conventional intercalated discs also were not observed between the cells of the AV node or the AV bundle. Atrial myocardial cells had the highest percentage of the plasma membrane occupied by desmosomes, fasciae adherentes and gap junctions. The AV bundle cells had the highest percentage of appositional surface membrane and a relatively large fraction of plasma membrane occupied by gap junctions. Cells of the superficial portion of the AV node had the smallest percentage of the plasma membrane composed of gap junctions, desmosomes or fasciae adherentes, as well as the smallest fraction of the cell membrane apposed to adjacent cells. The stereological data indicate that the most useful distinguishing characteristic between atrial muscle cells and conduction cells was that a smaller percentage of the conduction cell sarcoplasm was occupied by mitochondria and myofibrils. The most useful characteristics that could be used to differentiate between the regions of the AV junctional conduction tissues were the amounts and types of surface membrane specializations in the respective cell types.     

Thermotherapy for Harding-Passey melanoma: light and electron microscopic study

The changes of implanted Harding-Passey melanoma in C57Bl/6J mice following treatment with wholebody hyperthermia were studied. The treated tumours showed a progressive growth delay, cellular and architectural irregularities as well as cell injury characteristics. The presence of distended and irregular blood vessels, the peripheral localization of the melanosomes and the melanosome complexes were constant.     

Pseudocyanotic pigmentation of the skin induced by amiodarone: a light and electron microscopic study.

An unusual bluish discolouration of the nose was noticed in a woman 9 months after she had begun treatment with a coronary vasodilator, amiodarone hydrochloride. Cutaneous biopsies of the nose were obtained 6 and 9 months later for light and electron microscopic studies. In the dermis were histiocytes containing cytoplasmic yellow-brown granules with histochemical properties of melanin and lipofuscin. Ultrastructurally the granules appeared as lysosomal membrane-bound dense bodies similar to lipofuscin. Similar granules were observed at diascopy in both corneas. The pathogenesis is obscure. A storage disease involving the drug or its metabolites cannot be ruled out. Another possibility is that amiodarone accelerates the normal cellular autophagocytosis, resulting in increased production of lipofuscin, which then accumulates in lysosomes because of a deficiency in lipolytic enzymes.     

Morphology of mouse egg cylinder development in vitro: a light and electron microscopic study.

The endocrine control of yolk deposition in Drosophila melanogaster was studied by ligation and transplantation techniques. Endocrine events associated with the initiation of vitellogenesis were found to be synchronized with eclosion rather than the completion fo adult development. Decapitation experiments showed that a cephalic event occurring at about the time of eclosion is necessary for each animal to initiate vitellogenesis. The morphogenetic effect of the head could be replaced by a juvenile hormone analog (JHA). In addition to the cephalic event, a thoracic factor is required for each follicle to initiate vitellogenesis, since preparation of isolated abdomens before 16 hours after eclosion prevented vitellogenesis. In abdomens isolated after this time, no early vitellogenic stages were formed. The suppression of vitellogenesis in isolated abdomens was reversed by implanting corpora allata or by treating these preparations with JHA, but not by implanting corpora cardiaca. Ovaries that were artificially induced to mature by treating isolated abdomens with JHA still displayed the normal complement of ovarian proteins after electrophoresis in polyacrylamide gels. These results show that a circadian clock triggers vitellogenesis via a cephalic signal at eclosion, which in turn triggers events in the thorax or abdomen. The cephalic signal can be superseded by juvenile hormone, whose presence is necessary for each follicle to become vitellogenic.     

Calbindin-D immunolocalization in developing chick thyroid: a light and electron microscopic study

Antiserum to calbindin-D, a 28 KD vitamin D-dependent calcium binding protein, was used to localize the protein immunocytochemically in developing chick thyroid by both light and electron microscopy. The protein first appeared in future follicular cells of developing thyroid tissue from 8-day-old embryos. The number of calbindin-D-containing cells increased rapidly to a near-plateau level at day 10; this concentration was sustained until day 15, and then declined to an undetectable level just before hatching. The protein was distributed throughout organelle-free areas of the follicular cell cytoplasm and extended into the nucleus; it was not present in the follicular colloid. Comparison of the time course of changes in calbindin-D content with known differentiative changes taking place in follicular cells suggests that the protein may function in some yet to be determined mechanism related to normal development of the thyroid.     

The dorsal strand of Polyandrocarpa misakiensis (Protochordata: Ascidiacea): a light and electron microscopic study

The dorsal strand of a budding ascidian, Polyandrocarpa misakiensis , was studied by light and electron microscopy. The length and morphology of this organ vary even among zooids in the same colony. After curving between the paired posterior nerve trunks, the strand turns left and terminates in a dead end. The dorsal strand of this species is one of the simplest types among ascidians, since there is no branching, no extensive nerve plexus, and no neuronal or non-neuronal endocrine cells surrounding it. The strand mainly consists of a simple cuboidal epithelium, but has several variations, such as multilayered regions, and protrusions of a cellular chain. The strand cells usually have mitochondria, free ribosomes and a Golgi complex of dictyosomal type. There are many mitotic cells in the strand epithelium. The presence, between the cerebral ganglion and dorsal strand epithelium, of cells with morphology intermediate between the strand and neuronal cells suggests that the dorsal strand might supply cellular components, such as neurones, to the cerebral ganglion in adult zooids. At the caudal end, the strand cells show ultrastructural features suggesting active protein synthesis and secretion. These cells appear to be liberated from the epithelium to release the content of their granules.     

Development of the crayfish retina: A light and electron microscopic study

The development of the crayfish retina was examined in embryos and first, second and third instars with both and light and electron microscope. Light microscopic observations indicate that differentiation begins at the posterior portion of the optic disc and progresses in an anterior direction. Development of screening pigment, dioptric elements, and rhabdoms all parallel this posterior to anterior gradient in the retina. Tracer studies in early embryos reveal that the retina is separated from the proximal neuropil regions by a distinct vascular space. This observation suggests that the source of new cells for the retina may not be the more proximal cell proliferation zone as previously indicated. It is proposed that mitotic activity within the retina and/or differentiation of cells from the anterior surface layer of the eye may be sources for addition of new cells to the retina. Proto-ommatidial clusters of seven retinula cells occur very early at the posterior region of the embryonic retina. Initially the receptor cells extend throughout the entire thickness of the retina, but later they withdraw from beneath the cornea to occupy only the proximal portion of the retina. Microvilli of the rhabdom arise from the centrally opposed membranes of the retinula cells in each cell cluster. Each new microvillus contains a core of fine filaments which extend out into the cytoplasm at its base. As development of the microvilli continues, the core filaments appear to be lost or altered, but the cytoplasmic bundles at the base of the microvilli persist.     

A light and electron microscopic study of spinal ligament innervation

The innervation of the posterior ligamentous structures of the human lumbar spine was studied by light microscopy, scanning electron microscopy and transmission electron microscopy. Three types of nerve endings were recognized: free nerve endings, Paciniform corpuscles and Ruffini corpuscles. The free nerve endings, which are thought to act as nociceptors, were found in the superficial layers of all ligaments. A few free nerve endings were also identified within the supraspinous and interspinous ligaments. The Paciniform corpuscles were predominantly found in the supraspinous ligament. The Ruffini corpuscles were located in the interspinous and flaval ligaments. These findings suggest that the posterior ligamentous structures could be involved in the spinal control system.     

Histomorphologic and histochemical investigations in mannosidosis. A light and electron microscopic study.

Morphologic and histochemical studies have been performed at light and electron microscopic level on needle-liver biopsy specimens, circulating blood lymphocytes and fibroblast cultures from patients with mannosidosis. The findings demonstrated generalized storage phenomena of varying degrees in the various tissues examined. Histochemical findings were in agreement with the biochemical nature of the stored material. Enzyme histochemical methods indicated storage in the lysosomes, at least in the hepatocytes. The ultrastructural appearance of mannosidosis in itself has but a limited diagnostic significance since the morphology and distribution of vacuoles have characteristics in common with other storage diseases. Repeated liver biopsy disclosed extensive storage in the hepatic tissue. However, the progression of the disease was not accompanied by severe mechanical destruction or microcirculatory disturbances.     

Surface configuration of mesothelial cells in effusions. A comparative light microscopic and scanning electron microscopic study.

Surface configuration of mesothelial cells identified by light microscopy (LM) has been studied by scanning electron microscopy (SEM). It has been shown that mesothelial cells may have a variable SEM appearance. The surfaces of a small proportion of mesothelial cells are covered by regular microvilli (MV) and show openings of the pinocytotic vesicles. The surfaces of the majority of these cells are covered by vesicles or blebs. An intermediate population of mesothelial cells, i.e., cells displaying side-by-side blebs and MV, has also been observed. The latter cells no longer display pinocytotic vesicles. Occasional mesothelial cells have smooth surfaces. It has been shown by LM and transmission electron microscopy that cells with blebs are viable and capable of mitotic activity. It is concluded that mesothelial cells, detached from their epithelial setting, lose microvilli and pinocytotic vesicles and acquire surface blebs. The possible relationship between mesothelial cells and macrophages based on surface features has been discussed.     

Collagenous network in cartilage of human femoral condyles. A light microscopic and scanning electron microscopic study

To determine the spatial arrangement of collagen fibrils in articular cartilage of the human femoral head, three healthy femoral heads, obtained at necropsy, were examined by light microscopy and scanning electron microscopy. Light microscopic observations revealed no collagen fibril organization. Scanning electron microscopic observations showed a fine fibrillar texture throughout the articular cartilage. At the articular surface, smooth and fibrillated areas were detectable. Underneath the articular surface, the collagen network in the superficial zone showed a tighter appearance when compared with the homogeneous collagen network of the matrix in the deeper zones. The calcified cartilage zone was well demarcated from the uncalcified cartilage. The arcade model of Benninghoff [Z. Zellforsch. Mikrosk. Anat. 2: 783-862 (1925)] could not be confirmed. It was concluded that the organization of collagen fibrils in hyaline cartilage shows a three-dimensional network of randomly oriented fibrils.