Electron microscopic studies on the uptake of colloidal thorium dioxide particles by isolated fetal guinea-pig chondrocytes and the distribution of labeled lysosomes in cartilage formed by transplanted chondrocytes

Summary Chondrocytes isolated from fetal, guinea-pig epiphyses were grown in monolayer culture, exposed to thorium dioxide particles, and studied ultrastructurally after varying intervals. The exogenous marker was ingested by endocytosis and subsequently accumulated in lysosomes. After intramuscular injection into young guinea pigs, the thorium dioxidelabeled chondrocytes formed a typical hyaline cartilage. This consisted mainly of rounded or polygonal cells with large, eccentrically located nuclei. The cytoplasm showed an extensive granular endoplasmic reticulum and a well-developed Golgi complex, suggesting active synthesis and secretion of matrix components. Among the other cytoplasmic organelles, lysosomes containing variable amounts of marker particles were observed. After 2–3 weeks the transplants showed signs of cellular degeneration and disintegration. During these processes, lysosomes remained structurally intact and, furthermore, retained the incorporated marker. Thus, thorium dioxide-labeled bodies were found in former chondrocyte lacunae and in the intercellular substance proper. In the latter location labeled bodies could be observed in close proximity to early mineral deposits. These results are discussed with special reference to the cellular origin and lysosomal nature of matrix vesicles in calcifying cartilages.The skilled technical assistance of Mrs. Eva Lundberg and Miss Karin Askfors and the secretarial assistance of Mrs. Ingrid Wäälma are gratefully acknowledged.Financial support was obtained from the Swedish Medical Research Council (proj. no. 12X-3355), the Swedish Cancer Society (proj. no. 100-K71-05XK), the King Gustaf V 80th Birthday Fund, the Harald and Greta Jeansson Foundations, the C. B. Nathhorst Foundation, the A. O. Swärd Foundation, and from the Funds of Karolinska Institutet.     

Electron microscopic study on the thyroid gland of the salamander Hynobius nebulosus in the breeding season

Summary The thyroid gland of adult salamanders, Hynobius nebulosus, in the breeding season was studied by electron microscopy. The follicular cells are different in cell height and fine structures; the taller cells with many cell organelles and granules and the lower cells with a few cell organelles and granules are both present in the same follicle. In the cytoplasm, three types of membrane-bounded granules, namely, cytosomes, colloid droplets, and vacuolar bodies and circular membrane complexes occur. The vacuolar bodies are subdivided into two types; the ordinary type having loosely distributed particles and the specific type containing tubules and/or closely packed filaments, crystalloid structures, except for the particles. The chromophobe colloids within the Bensley-cells correspond to extremely large, ordinary type vacuolar bodies, while the Langendorff-colloid cells possess increased numbers of granular cisternae of endoplasmic reticulum and a ribosome-rich, dense cytoplasmic matrix but not extremely large colloid. The intracytoplasmic circular membrane complexes appear in the Golgi area of cytosome-rich cells. It is suggested that they originate from the Golgi apparatus which was activated to produce many cytosomes. Intranuclear inclusions consisting of microtubules and filaments and tight junctions between two adjacent lateral plasma membranes are occasionally encountered.     

CHONDROGENESIS, STUDIED WITH THE ELECTRON MICROSCOPE

The role of the cells in the fabrication of a connective tissue matrix, and the structural modifications which accompany cytodifferentiation have been investigated in developing epiphyseal cartilage of fetal rat by means of electron microscopy. Differentiation of the prechondral mesenchymal cells to chondroblasts is marked by the acquisition of an extensive endoplasmic reticulum, enlargement and concentration of the Golgi apparatus, the appearance of membrane-bounded cytoplasmic inclusions, and the formation of specialized foci of increased density in the cell cortex. These modifications are related to the secretion of the cartilage matrix. The matrix of young hyaline cartilage consists of groups of relatively short, straight, banded collagen fibrils of 10 to 20 mµ and a dense granular component embedded in an amorphous ground substance of moderate electron density. It is postulated that the first phase of fibrillogenesis takes place at the cell cortex in dense bands or striae within the ectoplasm subjacent to the cell membrane. These can be resolved into sheaves of "primary" fibrils of about 7 to 10 mµ. They are supposedly shed (by excortication) into the matrix space between the separating chondroblasts, where they may serve as "cores" of the definitive matrix fibrils. The diameter of the fibrils may subsequently increase up to threefold, presumably by incorporation of "soluble" or tropocollagen units from the ground substance. The chondroblast also discharges into the matrix the electrondense amorphous or granular contents of vesicles derived from the Golgi apparatus, and the mixed contents of large vacuoles or blebs bounded by distinctive double membranes. Small vesicles with amorphous homogeneous contents of moderate density are expelled in toto from the chondroblasts. In their subsequent evolution to chondrocytes, both nucleus and cytoplasm of the chondroblasts undergo striking condensation. Those moving toward the osteogenic plate accumulate increasingly large stores of glycogen. In the chondrocyte, the enlarged fused Golgi vesicles with dense contents, massed in the juxtanuclear zone, are the most prominent feature of the cytoplasm. Many of these make their way to the surface to discharge their contents. The hypertrophied chondrocytes of the epiphyseal plate ultimately yield up their entire contents to the matrix.     

Effects of isoproterenol on the fine structure of the hamster parathyroid gland

Ultrastructural changes of the parathyroid glands of isoproterenol-treated golden hamsters were investigated. Many chief cells in the parathyroid glands after 5 and 10 minutes of administration of isoproterenol contain well-developed Golgi complexes and granular endoplasmic reticulum, numerous prosecretory granules, and many secretory granules in the peripheral cytoplasm as compared with the control animals. Many chief cells in the parathyroid glands after 1, 3, 6 and 12 hours of administration have poorly-developed Golgi complexes, granular endoplasmic reticulum, many secretory granules and numerous lipid droplets as compared with the control animals. The morphology of the parathyroid gland after 30 minutes and 24 hours of administration resembles that of the control animals. It is considered that isoproterenol affects the secretory activity of the parathyroid gland.     

Electronmicroscopical observations on yolk and yolk formation in Ophryotrocha labronica LaGreca and Bacci

Summary In Ophryotrocha labronica LaGreca & Bacci mature yolk granules are found only in the ovocyte. Other typical yolk elements are lipid droplets, small vesicular bodies, multivesicular bodies and dense bodies. The two last-mentioned also appear in the accompanying nurse cell and from there obviously pass over unchanged into the ovocyte through a specific intercellular bridge, the fusome.The mature yolk granules are considered as aggregates of mitochondrial, endoplasmic and Golgi material, to which also is added pinocytotically incorporated external material. Mitochondria apparently play a fundamental role in the process, as the multivesicular bodies, most likely the direct precursors to the yolk granules, in all probability represent transformed mitochondria.Labelling with ³H-thymidine during vitellogenesis reveals presence of DNA in the yolk granules. From the labelling pattern, which shows DNA-synthesis both in the ovocyte and the nurse cell nucleus, it is concluded that the labelled material present in the cytoplasm of both cells — most of it in yolk granules and dense bodies — is of nuclear origin. The possible mitochondrial nature of yolk granule DNA is discussed.The author is indebted to Dr. Bertil Åkesson, Zoological Institute, Lund, for kindly supplying the initital material for the Ophryotrocha cultures. The excellent technical assistance of Mrs. Mariann Carleson is gratefully acknowledged. My thanks are also due to Mrs. Siv Nilsson for skilful assistance with the photography. This work has been supported by the Swedish Natural Science Research Council and Kungliga Fysiografiska Sällskapet, Lund.     

Ultrastructure of elastic cartilage in the rat external ear

Summary The structure of elastic cartilage in the external ear of the rat was investigated by transmission and scanning electron microscopy.The narrow subperichondrial, boundary zone contains predominantly ovoid cells rich in cell organelles: mitochondria, Golgi complex, granular endoplasmic reticulum and small (40–100 nm) vesicles. Scarce glycogen granules and bundles of 6–7 nm cytoplasmic filaments are also present. Deeper in the boundary zone, one or more cytoplasmic lipid droplets appear and cytofilaments become more abundant.Fully differentiated chondrocytes in the central zone of the cartilage plate resemble white adipose cells. They are globular and contain a single, large cytoplasmic lipid droplet. The cytoplasm is reduced to a thin peripheral rim; it contains a flattened nucleus, few cytoplasmic organelles and abundant, densely packed, cytoplasmic filaments.The intercellular matrix is very sparse. The pericellular ring consists of collagen fibrils about 20 nm in diameter and a proteoglycan cartilage matrix in the form of a stellate reticulum. The complex of these two structures appears in the scanning electron micrographs as a network of randomly oriented, ca 100 nm thick fibrils. Spaces between pericellular rings of matrix also contain thick elastic fibers or plates, apparently devoid of microfibrils. In scanning electron micrographs elastic fibers could be detected only in a few areas, in which they were not obscured by other constituents of the matrix. Immature forms of elastic fibers, oxytalan (pre-elastic) and elaunin fibers, were found in the perichondrial and boundary zones.     

Electron microscopic study of condylar cartilage of rat mandible stained with ruthenium red: proteoglycans and hypertrophic chondrocytes

Ultrastructure of hypertrophic chondrocytes and extracellular matrix in condylar cartilage of rat mandible was studied in conjunction with ruthenium red staining. Special care was given to the preservation of proteoglycans in the extracellular matrix. Ruthenium red-positive granules were observed in the pericellular matrix of condylar chondrocytes, and their size and number increased around the hypertrophic cells. However, these granules disappeared in the lowest hypertrophic zone, in which uncalcified cartilage matrix was also disintegrated prior to initiation of ossification. Moreover, hypertrophic chondrocytes observed at the lowest zone appeared intact in their ultrastructural features, i.e., containing numbers of lysosomes and coated vesicles in the cytoplasm facing the blood capillaries. The results strongly suggest that the lowest hypertrophic chondrocytes in rat condylar cartilage may have an active role in the degradation and resorption of the pericellular matrix, especially proteoglycans, and uncalcified matrix, which changes seem an essential step for the initiation of endochondral ossification.     

Ultrastructural, histochemical and cytochemical characterization of intestinal epithelial cells in Aplysia depilans (Gastropoda, Opisthobranchia)

To improve the current knowledge about the digestive system in opisthobranchs, light and electron microscopy methods were used to characterize the epithelial cells in the mid‐intestine of Aplysia depilans. This epithelium is mainly formed by columnar cells intermingled with two types of secretory cells, named mucous cells and granular cells. Columnar cells bear microvilli on their apical surface and most of them are ciliated. Mitochondria, multivesicular bodies, lysosomes and lipid droplets are the main components of the cytoplasm in the region above the nucleus of these cells. Peroxisomes are mainly found in middle and basal regions, usually close to mitochondria. Mucous cells are filled with large secretory vesicles containing thin electron‐dense filaments surrounded by electron‐lucent material in which acidic mucopolysaccharides were detected. The basal region includes the nucleus, several Golgi stacks and many dilated rough endoplasmic reticulum cisternae containing tubular structures. The granular cells are characterized by very high amounts of flat rough endoplasmic reticulum cisternae and electron‐dense spherical secretory granules containing glycoproteins. Enteroendocrine cells containing small electron‐dense granules are occasionally present in the basal region of the epithelium. Intraepithelial nerve fibres are abundant and seem to establish contacts with secretory and enteroendocrine cells.     

Effects of melatonin on the ultrastructure of the golden hamster parathyroid gland.

Ultrastructural changes of the parathyroid glands of melatonin-treated golden hamsters were studied. Many chief cells in the parathyroid glands after 1 hour of administration of melatonin contained poorly-developed Golgi complexes associated with a few prosecretory granules and numerous lipid droplets as compared with those of the control animals. The morphology of the parathyroid glands after 5 hours of administration resembled that of the control animals. Many chief cells in the parathyroid glands after 24 hours of administration had well-developed Golgi complexes and cisternae of the granular endoplasmic reticulum, numerous prosecretory granules, a few lipid droplets and many secretory granules in the peripheral cytoplasm as compared with those of the control animals. The ultrastructure of the parathyroid glands after 48 hours of administration was almost similar to that of the control animals. It is considered that melatonin affects the secretory activity of the parathyroid gland.     

Seasonal ultrastructural variations in pinealocytes of the woodchuck,Marmota monax

The ultrastructure of the pinealocyte in the woodchuck, Marmota monax, was studied during the four seasons of the year. Fall cells have a fairly uniform cytoplasmic density, organelles consistent with synthetic and/or secretory activity and rather extensive pericapillary and intercellular spaces. Many winter pinealocytes are nearly devoid of ribosomes and granular endoplasmic reticulum but contain lipid droplets associated with mitochondria. Pericapillary and intercellular spaces are minimal. Spring glands have the greatest variation in cytoplasmic density with intercellular and pericapillary spaces similar to that seen in fall glands. Cells containing electron dense cytoplasm have Golgi zone associated, secretory granules, free ribosomes, short sections of granular endoplasmic reticulum and dense bodies. Cells with a more electron lucent cytoplasm are similar to the most frequently observed summer pinealocytes which have numerous Golgi zones but few associated secretory granules. Microtubules are prominent in the cytoplasm of these cells, the plasma membranes are smooth and intercellular and pericapillary spaces are minimal. A yearly rhythm or cyclic activity of the pinealocyte is suggested.     

Cartilaginous metaplasia of the thoracic aorta of control turkeys and exacerbation by beta-aminopropionitrile

Seventeen of sixty distal extremities of the thoracic aortas of 12-week-old control male turkeys and 37 of 40 distal extremities of the aortas of turkeys fed 0.07% beta-aminopropionitrile (BAPN) from 4 to 12 weeks of age contained areas of cartilaginous metaplasia when examined by light microscopy. The cartilaginous areas were generally elongated and located in the subendothelium of control turkeys, but a roundish area of cartilage was occasionally evident in the deep media. The magnitude of chondroplasia was enhanced by feeding BAPN; the extensive lesion usually extended from the subendothelium to deep in the media. Regardless of treatment, chondrocytes were pleomorphic, contained vacuoles, and had cytoplasmic processes. The cells were separated by pools of proteoglycans and connective tissue. The ultrastructure of chondrocytes in the aortas of both treatment groups was typical of this cell type. They had undulations or projections of the cell membranes. The cisternae of endoplasmic reticulum were dilated and contained electron-translucent material which was similar to extracellular proteoglycans. Golgi apparatus, free ribosomes, mitochondria, glycogen granules, filaments, and a centriole also were present in the cytoplasm. The extracellular matrix, which included collagenous and elastic fibers and also delicate fibrils and interconnecting matrix granules, separated adjacent chondrocytes by spaces of varying size.     

The ultrastructure of mammary explants from virgin ovariectomized goats during hormone-induced lactogenesis

The effect of insulin (I), cortisol (F) and prolactin (P) on the ultrastructural morphology of epithelial cells of cultured mammary explants from virgin ovariectomized (OV-X) goats were studied. The epithelial cells showed little structural organization and were devoid of fat droplets and secretory protein granules at zero time of culture. The cytoplasm contained few profiles of smooth and rough endoplasmic reticulum and the Golgi apparatus was rudimentary. After being cultured in Waymouth's medium without added hormones the epithelial cells were indistinguishable from epithelial cells of uncultured explants. The addition of I induced changes mainly in the appearance of nucleoli. The nucleoli were enlarged and fibrillogranular areas with light spaces were observed. The most obvious cytological changes of epithelial cells of explants cultured in the presence of I and F are translocation of the nucleus into the basal cytoplasm, increase of rough endoplasmic reticulum, an increase in the size of the Golgi apparatus, presence of one or two lipid droplets and in some cells vacuoles with protein granules were present. Mitochondria were more abundant. The epithelial cells of explants cultured in the presence of I, F and P were characterized by the polarization of organelles within the cytoplasm and by the formation and release of protein granules and small and large fat droplets. The cell nucleus was in the basal cytoplasm, the Golgi apparatus was supranuclear. The rough endoplasmic reticulum was extensively developed and formed large sacs. Golgi vacuoles contained protein granules.(ABSTRACT TRUNCATED AT 250 WORDS)     

Control of the pars intermedia of the lizard,Anolis carolinensis

Summary The ultrastructure of the intermediate lobe of the hypophysis was studied in Anolis carolinensis with the use of a threefold aldehyde fixative. Lizards with a brown skin were selected. The possibility of two types of secretory cells is discussed; neither cell type is innervated. Type I cells are rarely found and contain dense granules approximately 0.3 m in diameter; Type II cells vary widely in secretory activity. Most of the Type II cells contain a large number of dense secretory granules (up to about 1.3 m in diameter) almost filling the cytoplasm. Rough endoplasmic reticulum (RER), Golgi apparatus and mitochondria are poorly developed. Only some of these cells show signs suggesting a high secretory activity, namely a well developed RER, Golgi apparatus and numerous mitochondria. In these cells the RER sometimes forms large intracisternal droplets (up to 7 m in diameter). Two of the animals exhibited a more uniform, high secretory activity. Large (about 2 m in diameter), pale vacuoles, probably of extracellular character, were found mostly in the vicinity of the perivascular septum. Their role in the release of MSH is discussed. The present data, which are discussed with reference to earlier findings (Forbes, 1972), form the morphological basis for an experimental study on regulation of MSH release (Larsson et al., 1979).Supported by grants from the Swedish Natural Science Research Council (to P. Meurling) and the Royal Physiographic Society of LundThe authors are indebted to Mrs. Ingrid Hallberg, Mrs. Kirsten Thörneby and Mrs. Lena Sandell for valuable technical assistance and to Miss Inger Norling for photographic aid     

四种淡水养殖鱼类血细胞的细微结构

四种淡水鱼的血细胞形态基本相似。红血球形态与其他低等脊椎动物基本相似。淋巴球绝大部分是小淋巴球:单核球数量较少;四种鱼的嗜中性白血球形态结构差不多,胞核多为蚕豆形,很少见分叶核,分叶一般也只有二叶,这与哺乳类显然不同;嗜酸性白血球的形态结构与其他脊椎动物基本相似;在少数血涂片中看到了嗜碱性白血球。       

Structure of taste buds in foliate papillae of the rhesus monkey, Macaca mulatta

Taste buds in foliate papillae of the rhesus monkey were examined by electron microscopy. Three distinct cell types were identified. Type I cells were narrow elongated cells containing an oval nucleus, bundles of intermediate filaments, several Golgi bodies, and characteristic apical membrane-bounded dense granules. These cells exhibited morphological variations: some had a moderately dense cytoplasm, perinuclear free ribosomes, and flattened sacs of rough endoplasmic reticulum; others had a more lucent cytoplasm, dilated irregular rough endoplasmic reticulum, lysosome-like dense bodies, and lipid droplets. Type II cells typically contained a spherical, pale nucleus, a prominent nucleolus, supranuclear and infranuclear Golgi bodies, mitochondria with tubular cristae, and one or two centrioles. This cell type, too, showed some variation in the relative amounts of ribosomes and smooth endoplasmic reticulum, which varied inversely with each other. Type III cells were characterized by a clear apical cytoplasm essentially devoid of ribosomes and containing microtubules. In a few type III cells, the peri- and infranuclear regions contained many ribosomes and some rough endoplasmic reticulum. In most Type III cells, there were large numbers of dense and clear vesicles in the peri- and infranuclear regions; some of the vesicles were grouped in synapse-like arrangements with adjacent nerves. The morphological variations exhibited by all three cell types could be accounted for by age differences in each of the cells. This would be consistent with the notion that cell renewal occurs in each of the three cell populations.     

Modifications of Golgi complex in chondrocytes from osteoarthrotic (OA) rat cartilage.

The status of the Golgi complex in normal vs osteoarthrotic (OA) cartilage has not yet been studied. A monoclonal antibody, MAb 58-K-9, allowed scoring of Golgi labeling intensity. In addition, ultrastructural assessment enabled us to focus on the distribution and relation between the endoplasmic reticulum (ER) and Golgi membranes. The study was performed in both normal and partially menisectomized OA-induced rat cartilage 20 and 45 days after surgery. Comparing Golgi immunolabeling intensities (mean +/- SEM) revealed a highly significant difference between normal (9.98 +/- 1.25), 20-day (2.49 +/- 0.34), and 45-day (0.82 +/- 0.22) cartilage. Moreover, chondrocytes from normal cartilage displayed 71.18% of labeling intensity in contrast to OA cartilage, in which chondrocyte labeling intensities were 24.95% (20 days) and 8.11% (45 days). OA chondrocytes appeared to display an overall reduction in Golgi labeling intensity, suggesting disruption of this organelle as the OA damage progressed. Interestingly, many 20-day OA-induced chondrocytes exhibited bubble-like Golgi immunolabeling compartmentalizing the cytoplasm, concomitant with putative apoptotic nuclear changes. At the same time, OA chondrocytes with a typical ultrastructural apoptotic pattern revealed a prominent ER gathered together with Golgi vesicles and saccules, also appearing to compartmentalize chondrocyte cytoplasm. We speculate about the role of Golgi modifications and apoptosis in OA pathogenesis.     

Immunocytochemical localization of pleurocidin to the cytoplasmic granules of eosinophilic granular cells from the winter flounder gill

The teleost gill is considered to be of significant immunological importance, as it is one of the first tissues exposed to environmental or pathogenic challenge and thus should be well equipped to mount an effective immune response. This study characterizes ultrastructurally and immunocytochemically a tissue granulocyte (eosinophilic granular cell) from the winter flounder gill that was previously determined to be involved in the gene expression and synthesis of a known antimicrobial peptide (pleurocidin). The cell is irregular in shape with a cytoplasm characterized by numerous large, electron-dense, membrane-bounded granules. The nucleus is euchromatic and closely associated with a prominent rough endoplasmic reticulum. The cytoplasm typically contains two to three mitochondria and a centralized Golgi apparatus surrounded by numerous electron-lucent vesicles. Immunogold staining of the cells with an anti-pleurocidin antibody shows large number of gold particles in direct association with the electron-dense granules. These data provide the first evidence definitively showing storage of an antimicrobial peptide in the cytoplasmic granules of an eosinophilic granule cell resident in gill tissue.     

Schistosoma mansoni: Development of acetabular glands of cercaria at ultrastructural level

Cercariae of Schistosoma mansoni in daughter sporocysts in Biomphalaria glabrata were studied with the electron microscope to observe the maturing process of their acetabular glands. The undifferentiated acetabular gland displays its enlarged basal area (fundus) and extended narrow process (duct) before other organ systems are recognized. Its fundus contains a prominent nucleus and subcellular organelles typical of active secretory cells.The secretory granules of the postacetabular glands are formed in a milieu of dilated rough endoplasmic reticulum and Golgi. Two morphologically different secretory granules are produced: (1) homogeneously granular ones, and (2) other granular ones with electron dense bodies in their matrices. Mostly, the homogeneously granular ones are produced first in the fundus and are forced into the ducts as the other type is formed.The secretory granules of preacetabular glands are formed from translucent vacuoles which arise from an environment of endoplasmic reticulum and Golgi. Two morphologically different secretory granules are produced: (1) one type has a homogeneous dense matrix, and (2) the other type has a less dense matrix containing electron-lucid bodies.The duct of an undifferentiated acetabular gland has either filamentous material or microtubules dispersed in its cytoplasm. Once microtubules are formed, they persist during the life of the cercaria. The microtubules are believed to have possibly two functions: (1) to support the long duct, and (2) to assist the movement of the secretory granules into the channels of the ducts where they remain until released during host penetration.Few of the subcellular organelles associated with secretory granules formation are seen in the duct except the area in close proximity to the fundus; thus, the few secretory granules produced in the duct are in this region.     

Effects of two mitosis inhibitors (Colchicine and Vinblastine) on the distribution and axonal transport of noradrenaline storage particles,studied by fluorescence and electron microscopy

Summary The lumbar sympathetic ganglia and the interganglionic interconnecting nerves of untreated rats and rats treated with Colchicine (COL) or Vinblastine (VIN) were studied with the help of the Falck-Hillarp fluorescence technique and electron microscopy. Both in untreated and drug treated rats there was a good correlation between the distribution of noradrenaline (NA) specific fluorescence and granular vesicles supporting the previous view that the granular vesicles represent the main intraneuronal NA storage sites. The granular vesicles were present both in the cell bodies—mainly in the peripheral part of the cytoplasm— and in the axons of untreated rats. After local application of COL or VIN on the ganglia there was a marked increase in fluorescence intensity and number of granular vesicles in many cell bodies. Often increased number of granular vesicles were found in the neighbourhood of the Golgi apparatus, in which region only few such vesicles are found in untreated rats. In some cell bodies high numbers of granular vesicles could be found all over the cytoplasm.When applied locally to axons the mitosis inhibitors caused a marked accumulation of fluorescence and granular vesicles—and other cell organelles like mitochondria and tubules of the endoplasmic reticulum-proximal to the site of application.A prominent feature both in cell bodies and axons of drug treated rats were large bundles of neurofilaments running through the cytoplasm. In the axons these filaments were often localized to the central part of the axon and surrounded by vesicles and tubules. Microtubules, on the other hand, which are rather numerous in cell bodies and axons of untreated rats seemed to be reduced in number after COL or VIN treatment, especially in those axons in which large amounts of subcellular organelles had accumulated.The present findings are discussed with respect to intraneuronal transport of NA and possible mechanisms behind this transport. It is suggested that the accumulation of fluorescence and granular vesicles after application of mitosis inhibitors is due to an interruption of the centrifugal transport of NA granules. The increased numbers of granular vesicles in the neighbourhood of the Golgi apparatus suggest that granular vesicles are produced in this part of the cytoplasm. This does not exclude a local formation of granular vesicles in other parts of the neuron. Furthermore, the possibility is discussed that the interruption of the transport is related to the increased number of neurofilaments and a possible decrease or disarrangement of microtubules. This discussion is based on previous suggestions that microtubules are involved in intracellular transport mechanisms and on recent findings that COL and VIN bind to proteins specific for microtubules.This study has been supported by grants from the Swedish Medical Research Council (B70-14X-2887-01; B71-14X-2887-02A; B71-14P-3262-01 A; B70-14X-2207-04; B71-14X-2207-05A; K70-40P-3045-01A), from Magnus Bergwalls Foundation, from Wilhelm and Martina Lundgrens Foundation, from the Medical Faculty, University of Göteborg.For generous supply of vinblastine (Velbe^®) we thank Eli Lilly Ltd.The skilful technical assistance of Mrs Kirsten Collin, Mrs Waldraut Hiort and Mr Pär-Anders Larsson is gratefully acknowledged.     

Ultrastructural features of supramedullary neurons in Crenilabrus quinquemaculatus

The ultrastructural study of the supramedullary neurons in Crenilabrus quinquemaculatus shows that these cells are engaged in intense synthetic activity as is testified by the nuclear morphology, the plentiful rough endoplasmic reticulum and polysomes, and finally the remarkably developed Golgi complexes, many of them active. Moreover the cytoplasm of the supramedullary neurons shows numerous membrane-bounded bodies (1,800-4,000 A) containing electron dense material, more or less finely granular. Research is presently being carried out to establish the meaning of these electron dense bodies.