Heterotopic allotransplantation of isolated aortic cells

Summary Smooth muscle cells were enzymatically isolated from the tunica media of the aorta of 5-day-old rats. Following in vitro exposure to colloidal thorium dioxide particles the cells displayed numerous lysosomes filled with these particles. Intramuscular injection of isolated cells into the tongues of young rats of the same strain, resulted in the formation by both freshly isolated and thorium dioxide-labeled cells of a characteristic tissue similar to that found in the intact aortic wall. Thus, the transplants consisted of typical smooth muscle cells surrounded by an extracellular matrix consisting of a microfibrillar network, patches and fibers of elastin, collagen fibrils and small polygonal granules believed to represent proteoglycans. This system can be used for experimental studies on the production of extracellular matrix components and on other functions of arterial smooth muscle cells growing outside the vascular wall.The technical assistance of Ms. Karin Blomgren and the secretarial assistance of Ms. Inger Åhrén are gratefully acknowledgedFinancial support was obtained from the Swedish Medical Research Council (proj. no. 12X-03355), the King Gustaf V 80th Birthday Fund, the M. Bergvall Foundation, the A.O. Swärd Foundation, and from the Funds of the Karolinska Institutet     

Electron microscopic studies on guinea pig rib cartilage

Summary The guinea-pig rib cartilage consists of chondrocytes dispersed in an intercellular substance composed of collagen fibrils, often characteristically cross-striated, and polygonal granules. Electron-dense membrane-bounded matrix vesicles are also observed intercellularly, especially in the central, partly calcified zone of the cartilage. With respect to their location in a cross-section of the rib, the chondrocytes differ in size, shape and intracellular fine structure. Thus, three separate types of cells are recognized. Peripheral chondrocytes have a flattened shape and are largely occupied by the nucleus. In the cytoplasm, the granular endoplasmic reticulum is the most extensive organelle. Intermediate chondrocytes are oval or round in shape. The endoplasmic reticulum and the Golgi complex are both prominent. Mitochondria and membrane-bounded cytoplasmic dense bodies are more numerous than in the peripheral cells. The ground cytoplasm often contains a few lipid droplets. In the central chondrocytes, such droplets sometimes fill the entire cytoplasm. Concomitantly, the nucleus is usually completely heterochromatic and the cells are therefore regarded as being metabolically inert.After preparations including ruthenium red staining en bloc, the general stainability of the chondrocytes is decreased. Intracellularly, positive ruthenium red staining of granular material within the Golgi vacuoles are to be observed. Extracellularly, the matrix granules are stained with this polyvalent, cationic dye. Extraction of the cartilage with 4 M guanidine-HCl removes all matrix granules and about 70% of the proteoglycans, measured as hexosamine, from the tissue. It is concluded that the matrix granules contain proteoglycan complexes.Financial support was received 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 Foundation, the C. B. Nathhorst Foundation, and from the funds of Karolinska Institutet.The skilled technical assistance of Mrs. Eva Lundberg and the secretarial assistance of Mrs. Inger Åhrén are gratefully acknowledged. The authors are indebted to Dr. S. Lohmander for helpful suggestions during the progress of the work.     

Bone formation in cartilage produced by transplanted epiphyseal chondrocytes

Summary Chondrocytes were isolated from rat epiphyseal cartilage, cultured in vitro, and exposed to exogenous tracers which accumulated in their lysosomes. The cells were then injected into the posterior tibial muscle of animals from the same outbred strain, where they reconstructed calcifying hyaline cartilage. The mineralization of the tissue was followed by ingrowth of blood capillaries from the host bed. Macrophage-like cells surrounding the vessels phagocytized degenerated chondrocytes and unmineralized matrix, whereas multinucleated chondroclasts removed some of the mineralized cartilage matrix. Mesenchyme-like cells accompanying the invading vessels attached to the remaining septa of calcified cartilage matrix and developed into osteoblasts depositing bone matrix on the surface of these septa. The apparent lack of inherent tracer labeling of the lysosomes in the different bone cells indicate that they were derived from the host. No signs of transformation of chondrocytes into bone cells were observed.When isolated rat epiphyseal chondrocytes were injected into the wall of the hamster cheek pouch, calcifying cartilage was reconstructed without signs of subsequent ossification. Transplantation of cartilage reconstructed in the hamster into the dorsal muscles of rats was, however, followed by formation of bone by a sequence analogous to that described above. Such an osteogenetic response was also obtained when the cartilage had been devitalized before transplantation.These experiments show that calcified cartilage, developing in or grafted into an intramuscular site, is able to induce and serve as a substrate for endochondral bone formation, similar to that occurring during normal development. They further indicate that bone induction by calcified cartilage does not require the presence of living chondrocytes.Financial support was obtained from the Swedish Medical Research Council (proj. no. 03355), the King Gustaf V 80th Birthday Fund, and from the funds of Karolinska Institutet. The authors thank Karin Blomgren for technical assistance and Inger Lohmander-Åhrén and Eva Pettersson for secretarial helpOn leave from the Department of Histology and Embryology, Medical Academy, Warsaw, Poland     

Isolation of a purified mitochondrial fraction from viable clonal insulin-producing cells (RINm5F) by percoll density gradient centrifugation

Summary A Percoll density gradient was employed for selecting large numbers of viable insulin-producing RINm5F cells. Homogenates of these cells were then subjected to gradient centrifugation and two clearly visible bands were obtained. The light fraction was essentially composed of mitochondria banded at a density of about 1.06 g/ml. The heavier fraction banded at 1.09 to 1.10 g/ml and contained lysosomes and a small number of secretory granules. The distribution of Percoll particles was restricted to the extracellular space and there was no adsorption to any membrane structures. The distribution pattern of marker enzymes for the mitochondria and lysosomes was similar to that of normal pancreatic β-cells. With the use of a Percoll density gradient it was thus possible to isolate a purified mitochondrial fraction from viable RINm5F cells. This work was supported by the Swedish Medical Research Council (03x-4, 12x-562, 12x-6240), the Swedish Diabetes Association, the Nordic Insulin Foundation, Syskonen Svenssons Foundation, and ?ke Wiberg’s Foundation. Per-Olof Berggren is a recipient of a postdoctoral fellowship from the Swedish Medical Research Council.     

Electron-dense precipitates in glomus cells of rat carotid body after fixation in glutaraldehyde and pyroantimonate-osmium tetroxide mixture as possible indicators of calcium localization

Summary An attempt was made to study the subcellular localization of calcium in carotid body glomus cells of adult rats using fixation with glutaraldehyde followed by treatment with a mixture of pyroantimonate and osmium tetroxide. Precipitates were seen as electron-dense particles (EDP) in the glomus cells, mostly within membrane-bound organelles, such as dense-cored vesicles, mitochondria, small clear vesicles, multivesicular bodies, and especially in lysosomes. However, EDP were also seen in the nuclei and in the free cytoplasm of the glomus cells and even outside them.Preincubation of carotid bodies in media containing calcium and either high potassium or calcium-ionophore A 23187 resulted in a marked increase in the general precipitation pattern, there being an increased amount of EDP both in the glomus cell nuclei and in the cytoplasm. Dense-cored vesicles more often showed precipitates than those in the controls. Some dense-cored vesicles contained multiple precipitates, typically located in the electron-lucent area between core and vesicle membrane.Extensive diffusion of ions probably occurred during fixation before precipitation, making the localization of calcium and other precipitating cations unreliable. However, it is possible that precipitates, which were regularly seen in the dense-cored vesicles, may reflect the content of bound calcium. The possible significance of calcium in glomus cell function is discussed, and the need for more adequate methods is emphasized.The present study has been supported by grants from the Finska Läkaresällskapet and the Sigrid Jusélius Foundation, Helsinki, FinlandWe wish to express our gratitude to Dr. Robert Hamill of Eli Lilly Co. for kindly providing us with the ionophore A 23187. Technical assistance by Mrs. S. Huhtaniitty and Mrs. T. Stjernvall is gratefully acknowledged     

Uptake of putrescine by Tetrahymena

Summary The uptake of the diamine ³H-putrescine by Tetrahymena pyriformis GL was studied in cultures which were synchronized by heat shocks. An inverse correlation was found between the uptake of putrescine and the acid stability of DNA, but there was also a parallelism between putrescine uptake and the intracellular amount of putrescine. There was no evidence for a transformation of the labeled putrescine to other amino compounds within the cells. Electronmicroscopical autoradiography showed a structure-bound radioactivity localized to nuclear and mitochondrial structures. In the nucleus, both the chromatin and the nucleoli showed labeling.The authors are indebted to fil. kand. Per Arlock, who participated in some preliminary experiments, and to Mrs Siv Nilsson and Mrs Annagreta Petersen for skilful technical assistance. The investigation was financially supported by the Swedish Natural Science Research Council, the Swedish Cancer Society and the C.-B. Nathhorst Scientific Foundation.     

Fine structural localization of acid phosphomonoesterase in the brush border region of osteoclasts

Summary The fine structural localization of acid phosphomonoesterase was studied in osteoclasts of fracture callus in the rat. In addition to being present in the Golgi apparatus and the lysosomes, reaction product was precipitated over tubular elements, vesicles, and vacuoles located subjacent to the brush border. The findings are compatible with the idea that the calcified matrix can be destroyed by the combined effects of absorption with subsequent intracellular digestions in osteoclasts, and actual secretion of lysosomal enzyme to the extracellular space.This study was supported by grants from the Swedish Medical Research Council (Project no. B72-12X-1006-07A) and Konung Gustav V:s åttioårsfond". The assistance of Miss Silwa Mengarelli and Mrs. Britt-Marie Åkerman is gratefully acknowledged.     

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.     

Extracellular matrix fibrils and cell contacts in the chick embryo

Summary The migration of neural crest and sclerotome cells and the extension of ventral root axons in chick embryos at stages 16–20 were studied by light microscopy as well as scanning and transmission electron microscopy at the leg bud level of fixed specimens. Extensive cellular movements take place in association with an extracellular matrix consisting of microfibrils. The neural crest and sclerotome cells migrate into the large matrix-filled extracellular space surrounding the neural tube and notochord, apparently using microfibril bundles as substratum. The cells exhibit pseudopodia which are closely associated with the matrix fibrils. The fibrils around the notochord show a spatial arrangement indicating that the sclerotome cells are contact-guided to their subsequent positions. Mutual cell contacts, including those established by cell processes, frequently show cytoplasmic electron dense plaques at adjacent membranes. These small plaque contacts might be correlated to contact inhibition of locomotion between the cells and participate in the guidance of cells. The growth cones of extending axons exhibit filopodia contacting both surrounding mesenchyme cells and extracellular fibrils. The orientation of the axons might thus be affected by contacts with cell surfaces as well as with extracellular material.Technical assistance was given by Mrs. Kerstin Ahlfors, Mrs. Charlotte Fällström, Mrs. Annika Kylberg and Mrs. Stine SöderströmSupported by grants from The Swedish Natural Science Research Council     

Enzyme activities and electronmicroscopic structure of rat milk fractions obtained after centrifugation

Summary LDH and MDH activities were found to increase after freeze-thawing of the cream and a non-fat fraction of rat milk isolated by centrifugation.Electronmicroscopy of these fractions revealed that cellular components occurred especially in association with milk fat globules but also in combination with secretion granules.The fat globule fraction represented only 20% of the milk volume but accounted for more than 50% of the LDH and 75% of the MDH activities in milk.The results show that in the rat mammary gland an apocrine secretion type occurs. The reason why the LDH and MDH activities increase in the milk during the lactation of the rat must be that increasing amounts of cellular material is passed into milk at secretion, containing increasing activities of LDH and MDH.This investigation was supported by grants from the Foundation of Magnus Bergwall and the Swedish Natural Science Research Council.The skillful technical assistance of Mrs Anna-Greta Petersen and Mrs Marie Adler-Maihofer and the secretarial help of Miss Marianne Andersson are gratefully acknowledged.     

Formation of primordial yolk granules in the avian oocyte

Summary Electron and light microscopical investigations of early oocytes (between 1.0 mm and 5.0 mm in diameter) from the ovary of 28–30 week-old chickens, suggested the formation of primordial yolk granules from cytoplasmic vesicles. These vesicles formed an aggregation which was observed to be surrounded by membranes, giving the aggregate a multivesicular body-like appearance. At a later stage the vesicles inside the membrane disintegrated and the multivesicular bodies acquired the appearance of primordial yolk granules. The contribution of other structures to the formation of yolk granules is discussed.For constructive criticism I am very grateful to Dr. Hadar Emanuelsson, Institute of Zoophysiology, Lund. The excellent technical assistance of Miss Inger Antonsson and Mrs. Annagreta Petersen is gratefully acknowledgedThis work was supported by Kungliga Fysiografiska Sällskapet, Lund     

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.     

Origin of the glial processes responsible for the spontaneous postnatal phagocytosis of boutons on cat spinal motoneurons

Summary Previous studies have demonstrated that astrocyte processes are responsible for a spontaneously occurring phagocytosis of boutons on cat spinal motoneurons during the second postnatal week. In the present investigation, the astrocytes and the astrocyte processes in contact with the motoneurons were studied qualitatively and quantitatively during the early postnatal period. It could be concluded that the cells responsible for the phagocytosis of boutons are immature astrocytes. These cells were present not only during the period of phagocytosis but also prior to this period. The type of process responsible for the phagocytosis was present not only during the period of phagocytosis but also prior to and after that period although the relative contribution of such processes to the glia-covered membrane area of the motoneurons was reduced in the older animals. On the basis of these results, the possible specificity of the immature astrocyte as the element responsible for the phagocytosis of boutons during normal development is discussed.The author is indebted to Miss Maj Berghman, Mrs. Anna-Stina Höijer and Mrs. Lillebil Stuart for excellent technical assistance. This work was supported by grants from Karolinska Institutet and the Swedish Medical Research Council (proj. 2886).     

The pars intermedia of the mink,Mustela vison

Summary The pars intermedia of intact and experimental female minks has been studied by light, electron and fluorescence microscopy. The general structure of the mink intermediate lobe is described. Two main cell types are recognized. One, termed glandular cell, predominates in number and is characterized by the presence of electron-dense granules about 200 nm in diameter and numerous large vesicles up to 300 nm in diameter. The other, termed stellate cell, is devoid of cytoplasmic vesicles and granules and possesses microfilaments, junctional complexes and elongated processes inserted between the glandular cells. Different treatments (photostimulation and administration of hypertonic saline and metopirone) induced morphological reactions in the glandular cells. The significance of these changes and the possibility of a functional relation between the pars intermedia and ACTH secretion are discussed.Numerous nerve fibres and axon terminals containing electron-dense granules (60–120 nm) and electron-lucent vesicles (30–40 nm) are observed throughout the pars intermedia.With the histochemical fluorescence method of Falck-Hillarp a rich system of delicate fluorescent varicose fibres, sometimes provided with irregular swellings or droplets, is observed in the pars intermedia and also in the pars nervosa. Microspectrofluorometrically these fibres exhibit the spectral characteristics of catecholamines. All the cells of the pars intermedia and a large number of cells in the pars distalis show a yellowish weak fluorescence, which becomes much stronger after combined formaldehyde-ozone treatment. This cellular fluorophore shows the same microspectrofluorometric characteristics as does the fluorophores of tryptamine and of certain peptides with NH₂-terminal tryptophan.Supported by the Swedish Fur Breeders' Association and the Swedish Natural Science Research Council (grant No. 2124). Thanks are due to Miss W. Carlsson and Miss Y. Lilliemarck for their helpful technical assistance.Supported by the Harald and Greta Jeanssons Stiftelse and by the Ford Foundation. The skilful technical assistance of Mrs. Eva Svensson and Miss Annika Borgelin is greatfully acknowledged.     

A human liposarcoma cell line

Summary The properties of a new cell line derived from a human retroperitoneal liposarcoma are described. The cells do not grow at low cell concentrations and contain in their cytoplasm large numbers of droplets that stain with Oil Red O. No indication of the presence of endogenous virus particles could be found. The mean chromosome number per cell is 36, with several constant markers, the most conspicuous of which is a large submetacentric marker due to a translocation between chromosomes 4 and 11, which is present in every cell. The liposarcoma cells show an enhanced uptake of [¹⁴C]acetate compared to normal human fibroblasts. This work was supported by funds from the Poliomyelitis Research Foundation, the National Cancer Association of South Africa, and the State health Department. The authors thank Mrs. D. Bower and Mrs. M. Orchard for their excellent technical assistance.     

Fluorescence histochemical evidence for axonal growth and secretion from transplanted adrenal medullary tissue

Summary Small pieces of rat adrenal medulla were homologously transplanted to the anterior chamber of the eye. The eyes were adrenergically denervated. Transplants became attached to and vascularized by the iris of the host eye. Transplants and irides were examined at various times postoperatively with the histochemical fluorescence method of Falck and Hillarp.It was shown that the adrenal medullary transplants were able to produce catecholamine-containing nerves that partly reinnervated the denervated host iris. The nerves derived at least partly from groups of highly fluorescent cells, similar to the adrenaline and/or noradrenaline cells of the normal adrenal medulla. The cells were thus not similar to sympathetic adrenergic nerve cells.Intravasal secretion of fluorescent material was observed in one case, indicating that the transplanted medullary tissue was also able to fullfill its normal endocrinological role of releasing hormones to the blood stream.This investigation was supported by grants from the Swedish Medical Research Council (B70-14x-714-05 and B70-14x-711-05B), Svenska Livförsäkringsbolags nämnd för medicinsk forskning, Ollie and Elof Ericssons Stiftelse and Stiftelsen Therese och Johan Anderssons Minne. The skilful technical assistance of Mrs. Ulla Flyger and Mrs. Barbro Norstedt is greatfully acknowledged.     

Production of specific-protein secretion granules by fat body cells of the blowfly,Calliphora erythrocephala

Summary During the first four days of the imaginai stage the fat cells of ovariectomized females of Calliphora develop a protein synthetic apparatus, and produce dense bodies (lysosomes) as do the fat cells of normal females, but apparently they cannot synthesize the protein secretion granules that characterize the productive phase of the fat cells of normal females and that we believe to represent vitellogenin. Injection of ovariectomized females with -ecdysone restored the ability of the fat cells to produce the secretion granules. It is suggested that the ovary gives off a factor which induces the production of the protein secretion granules by the fat cells, and that the factor from the ovary can be substituted by -ecdysone. This, we believe, is the first ultrastructural evidence for an effect of the ovary and of -ecdysone on the synthesis of specific protein.We are grateful to the Carlsberg Foundation and to the Danish Science Research Council for generous grants, and to the latter for placing an electron microscope at our disposal. It is a pleasure to thank Dr. Gareth Griffiths for valuable advice as to the preservation of the fat body tissue. We also thank Mrs. Lotte Bakhoj and Mrs. Elsebeth Lund for skilful technical assistance1896–1976     

Electron microscopical demonstration of acid phosphatase activity in the central nervous system

Summary A modified technique is described for the demonstration of acid phosphatase activity in the central nervous system by means of electron microscopy. Enzyme activity can be demonstrated in lysosomes, pigment bodies, and the Golgi zone of cortical neurons. Glial and endothelial cells also contain acid phosphatase active lysosomes. They are located in the pericarya, and in the processes of the glial cells, respectively.The authors express their sincere appreciation to FräuleinS. Luh and FräuleinW. Komp for their assistance and help.     

A catecholaminergic neuron connecting the first two optic neuropiles (Lamina ganglionaris and Medulla externa) of the crayfish Pacifastacus leniusculus

Summary The crustacean optic neuropiles, the lamina ganglionaris and especially the medulla externa, show a specific pattern of green fluorescence with the fluorescence histochemical method of Falck-Hillarp. Normally, only the terminals and the cell bodies fluoresce, but in reserpine-treated animals exogenous catecholamines are taken up by the whole adrenergic neuron and are thus visualized as a whole. Incubating crayfish optic neuropiles in dopamine or -methylnoradrenaline after reserpine treatment demonstrated a tangential neuron connecting the lamina and the medulla externa. The morphology of this tangential neuron differs from the two types of tangential neurons, Tan₁ and Tan₂, previously characterized with Golgi techniques. The catecholaminergic neuron thus constitutes a third tangential neuron type. Acknowledgement. The present study has been supported by the Swedish Natural Science Research Council, grant B 2760-009, the Magnus Bergvall foundation, and the Swedish Medical Research Council, grant 04X-712, the latter to Prof. Bengt Falck to whom we extend our gratitude. We are also indebted to Mrs. Rita Wallén and Miss Maria Walles for their skilled technical assistance. Reserpine (Serpasil^®) was generously given to us by Hässle-Ciba-Geigy AB     

Uptake and intracellular transport of cationic ferritin in the bronchiolar and alveolar epithelia of the rat

Summary Cationic ferritin was used as a marker to reveal the processes of endocytosis and intracellular transport in bronchiolar and alveolar epithelia. The marker was injected into the lung via the trachea, and ultrastructural observation of the distribution of ferritin particles in bronchiolar and alveolar epithelial cells was carried out at intervals of 5, 15, 30 and 60 min after the injection. The luminal surface of the airway and the alveolar epithelium showed diffuse labeling with cationic ferritin. In general, ferritin particles were observed in vesicles and vacuoles of the bronchiolar and alveolar epithelial cells within 5 min of injection; they appeared in multivesicular bodies within 15 min. Multivesicular bodies and secondary lysosomes containing ferritin particles, some of which showed a positive reaction for acid phosphatase, were seen in the basal cytoplasm within 30 min; ferritin particles appeared in the basal lamina below the Clara cells, ciliated cells and type 2 alveolar cells within 30 min. Ferritin particles were seen in ovoid granules of some Clara cells and in lamellar inclusion bodies of many type 2 alveolar cells. Brush cells and type 1 alveolar cells took up only a small quantity of ferritin particles.