Development of the filiform hairs on the cerci of Gryllus bimaculatus Deg. (Saltatoria,Gryllidae)

Summary The filiform hairs, mechanoreceptors of Gryllus, pass through six developmental stages during the last larval stage. The cytoplasm of their sense cells suggests intensive synthesis of protein for cellular metabolism and intercytoplasmic exchange of material via glial evaginations. Ultrahistochemical tests demonstrated acid phosphatase in the lysosomes as well as in components of the Golgi apparatus. There was no significant change in the appearance of the sense cell cytoplasm, indicating a maintained functional state also during molting. The new cuticular apparatus is formed after apolysis by the three enveloping cells. Formation of the replacement hairs is initiated by a cytoplasmic outgrowth of the trichogen cell. During morphogenesis of the new hair, the microtubules serve as a cytoskeleton and probably control the flow of vesicles, which contain phenol oxidase, also demonstrated in the Golgi apparatus, and are incorporated into the new cuticle. Bundles of microfibrils are involved in the surface sculpturing of the replacement hair. The trichogen cell also forms a number of structural elements, e.g. the cup and strut marked geometric peculiarities of which indicate that they are important in the spatial orientation of the dendrite and thus also in transduction. Reduction of the apical cell membrane of the tormogen cell after apolysis permits unrestricted growth of the new hair into the exuvial space. The tormogen cell participates in the formation of the joint membrane, parts of the socket and the articulation of the hair.Supported by the Deutsche Forschungsgemeinschaft. The author thanks Mrs. G. Thomas for drawing the diagrams, and Miss I. Grossman and Mrs. M. Ullmann for technical assistance     

Morphological alterations in mammalian neurons in vitro in response to hypertonic solutions

Summary Neurons in cultures of central nervous tissue exhibited marked structural changes when exposed to hypertonic solutions. Cellular reactions were described in living neurons as well as after fixation and staining in preparations observed with both the light and electron microscope. The structures involved in these changes were mainly the nucleolus, the nucleus and the Nissl substance.Nucleolus In living neurons, observed with phase contrast optics, the nucleolus became invisible in hypertonic medium. This change occurred within a few seconds, and it was reversible when the cells were brought back to isotonic solutions. Fixation of the cells while exposed to hypertonic solution caused the nucleolus to reappear as a granular body. In stained preparations it appeared as a more irregular body in contrast to the smoothly outlined nucleolus in normal cells. In electron microscopic preparations of neurons which were fixed while exposed to hypertonic solutions the nucleolus was visible only as nucleolar shadow, overlaid by a few small irregular bodies of higher electron density than other nuclear contents.Nucleus The nuclear membrane of living neurons exposed to hypertonic media lost much of its sharp definition and became rather hazy in outline. The nuclear diameter increased about 10% in hypertonic medium, and the nuclear space became somewhat denser when observed with the phase contrast microscope. In Nissl stained preparations the nuclear space was filled with many small granular or rod-shaped bodies in contrast to the clear vesicular appearance of the nuclei of untreated cells. In electron microscopic preparations the nuclear space exhibited a spotty appearance due to the presence of electron dense and light areas.Nissl Substance In living neurons immersed in hypertonic solutions the Nissl substance showed a slight increase in phase density, especially after repeated changes between hypertonic and isotonic solutions. Sometimes a distinct striation in the Nissl substance appeared. In Nissl stained preparations there was no marked change observed in comparison with normal cells. However, in the electron microscope, the Nissl substance of hypertonically treated cells exhibited a marked structural change. The membrane-bound spaces of the endoplasmic reticulum assumed a rather precise orientation parallel to the cell membrane so that in extreme cases a concentric arrangement of endoplasmic cisternae was observed. The normal arrangement of ribosomal granules in rosettes and clusters became disturbed and the granules were more uniformly distributed.The cells as whole units showed a distinct shrinkage in hypertonic solution which may account for the more crowded appearance of various organelles such as mitochondria and Golgi complexes. There was also a marked increase in agranular reticulum profiles and small membrane bound vesicles in treated cells. Vacuoles appeared frequently in the cytoplasm of treated cells; they disappeared upon re-immersion in isotonic medium.This investigation was supported by USPHS Grants NB 03114-04, NB 00690-11 and 5 T 1 GM 495 from the National Institutes of Health, Bethesda, Maryland.Acknowledgement. Mrs. Eleanor W. Morris and Mr. Edwin E. Pitsinger, Jr. gave indispensible aid with the management of the cultures and with photographic procedures.     

Qualitative and quantitative preservation of the fine structure of absorptive cells in cultured biopsies of human small-intestine

Summary The fine structure of the absorptive cells in human small-intestinal biopsies cultured for 6, 24, and 48 h was analyzed qualitatively and quantitatively. The findings show generally good preservation of the cultured absorptive cells and a normal distribution, size, and relative volume of their cell organelles, but there was a systematic decrease in the apical cell surface and an increase in the number of apical vesicles and tubules after culturing. Since the apical vesicles and tubules are thought to have a function in the transport of cell-coat material from the Golgi apparatus to the cell surface, these findings raise the question of whether a delayed transport or extrusion of cell surface material occurs.The diminished relative volume of the mitochondria and the increased signs of autophagy in some poorly preserved absorptive cells, are assumed to be an adaption to less favourable culture conditions.The authors acknowledge the help of Dr. A.S. Pena in the setting up of the organ culture technique, and also wish to thank Mrs. M.L. Bouwhuis for statistical advice and Mrs. M. de Gruil and Mr. L.D.C. Verschragen for technical assistance. The investigations were supported in part by the Foundation for Medical Research (FUNGO), which is subsidized by the Netherlands Organization for the Advancement of Pure Research (ZWO)     

Fine structure of nerve cells in a planarian

The fine structure of the nerve cell types in the white planarian Procotyla fluviatilis were described. Ganglion cells comprise the major portion of the brain. These cells are irregular in shape with several cytoplasmic processes and contain ribosomes, a sparse endoplasmic reticulum, microtubules, lysosomes, and a Golgi apparatus with numerous small vesicles. Granule-containing cells are situated in the peripheral regions of the brain and along the nerve cords. These cells contain ribosomes, rough-surfaced endoplasmic reticulum and a Golgi apparatus with associated dense granules. The granules occupy most of the cytoplasm and are ～ 750A in diameter with moderately dense contents, ～ 750A with opaque contents, and ～ 1000A with contents of medium density. These granules are similar to those in the nervous systems of higher animals that contain epinephrine, norepinephrine, and neurosecretory substance, respectively. Each cell contains predominantly one type of granule although there is some intermixing of granules and intermediate types between the three most abundant granules. Small clear vesicles, resembling cholinergic synaptic vesicles, and all types of dense granules occur in the neuropil and within nerve endings.     

Golgi apparatus respond to the antitumor sulfonylurea N-(4-methylphenylsulfonyl)-N′-(4-chlorophenyl)urea (LY 181984) in sulfonylurea-susceptible but not in resistant cell lines

Summary Cell lines susceptible or resistant to the active antitumor sulfonylurea [N-(4-methylphenylsulfonyl)-N-(4-chlorophenyl)-urea] (LY 181984) were treated with 100 M sulfonylurea for 1 or 3 h followed by monensin for 1 h. With cell lines where growth was inhibited by the active sulfonylurea, swollen Golgi apparatus cisternae following treatment were fewer and smaller than in untreated cells. Overall the volume of monensin-responsive trans cisternae was reduced by about 50% to 75% in cells lines where the antitumor sulfonylurea was growth inhibitory. The swelling response was unaffected by sulfonylurea in sulfonylurea-unresponsive cells. The antitumor-inactive sulfonylurea [N-(4-methylphenylsulfonyl)-N-(phenyl)urea] (LY 181985) was without effect on cisternal swelling with both susceptible and resistant cell lines. The results suggest a response of the trans Golgi apparatus to the active antitumor sulfonylurea that resulted in reduced acidification of the trans Golgi apparatus cisternae. This response appears to be restricted to susceptible cell lines where growth was inhibited by the active antitumor sulfonylurea but not in resistant cell lines where growth was unaffected by the active antitumor sulfonylurea.     

LYSOSOMES AND GERL IN NORMAL AND CHROMATOLYTIC NEURONS OF THE RAT GANGLION NODOSUM

The rat ganglion nodosum was used to study chromatolysis following axon section. After fixation by aldehyde perfusion, frozen sections were incubated for enzyme activities used as markers for cytoplasmic organelles as follows: acid phosphatase for lysosomes and GERL (a Golgi-related region of smooth endoplasmic reticulum from which lysosomes appear to develop) (31–33); inosine diphosphatase for endoplasmic reticulum and Golgi apparatus; thiamine pyrophosphatase for Golgi apparatus; acetycholinesterase for Nissl substance (endoplasmic reticulum); NADH-tetra-Nitro BT reductase for mitochondria. All but the mitochondrial enzyme were studied by electron microscopy as well as light microscopy. In chromatolytic perikarya there occur disruption of the rough endoplasmic reticulum in the center of the cell and segregation of the remainder to the cell periphery. Golgi apparatus, GERL, mitochondria and lysosomes accumulate in the central region of the cell. GERL is prominent in both normal and operated perikarya. Electron microscopic images suggest that its smooth endoplasmic reticulum produces a variety of lysosomes in several ways: (a) coated vesicles that separate from the reticulum; (b) dense bodies that arise from focal areas dilated with granular or membranous material; (c) "multivesicular bodies" in which vesicles and other material are sequestered; (d) autophagic vacuoles containing endoplasmic reticulum and ribosomes, presumably derived from the Nissl material, and mitochondria. The number of autophagic vacuoles increases following operation.     

Autoradiographic study of RNA synthesis in isolated cells in culture from chick embryo spinal ganglia

Summary Dissociated cells from 9, 12 and 15 day-old chick embryo spinal ganglia were cultivated in presence of total embryo-extract, brain embryo extract, or total embryo extract supplemented with purified nerve growth factor (NGF). The cells were maintained during 4 days in Maximow assembly and during 1 month in Rose chamber. Neurons showed growth of nerve fibres. The non-neural cells evolved to spindle cells, Schwann cells, or fibroblasts.Ribonucleic acid (RNA) synthesis was followed with tritiated uridine by autoradiography. Some nerve cells showed tritiated uridine incorporation. The highest incorporations for short-term cultures were at 15 hours in presence of NGF, at 48 hours in presence of total or brain extract, and for long-term cultures at 8 days. These periods corresponded to the highest growing activity of the nerve fibres. After 4 days all the non-neural cells incorporated tritiated uridine.The tritiated uridine was first incorporated into the RNA of the nucleus and, afterwards was found also in the cytoplasm. The presence of brain extract or of NGF stimulates the incorporation of labelled uridine into RNA. No labelling was found in the nerve fibres, even after 4 hours incubation.Chargée de Recherche au C.N.R.S.This communication is a part of the Doctorat és-Sciences thesis, presented by Mrs. J. Treska-Ciesielski.With the technical assistance of Mrs. M. F. Knoetgen and A. Bieth.     

Regeneration of the islets of Langerhans in the guinea pig

Summary The regeneration of the islets of Langerhans in the guinea pig was studied after intravenous injection of alloxan. A number of cells in the islets was destroyed within 24 h after alloxan, but after 48 h there was a rapid proliferation of the surviving cells of the islets. This depended on the dosage of the drug as well as the timing. Electron microscopy of the islet at 48 h showed that the dividing cells had small electron dense granules and resembled a subtype of normal A cells, whose function is not yet known. There were also many agranular cells in the islet. These two groups of cells seen in the regenerating islet could be precursor cells, which could differentiate into cells. There was no evidence for transformation of duct cells or acinar cells into islet cells. None of the guinea pigs became permanently diabetic. This was probably due to inadequate dosage which resulted in only partial degeneration of the cells followed by regeneration and recovery. There was also some regeneration of the liver, kidney and the adrenal cortex following alloxan.The author is grateful to Professor R. Barer for his guidance and for providing the facilities for this study. Thanks are also due to Mrs. D. Barraclough for technical assistance and to Mrs. M. Hollingsworth for assistance with the photographsThis work was financed by a grant from the Cystic Fibrosis Research Trust     

Synthesis of glycoproteins in the Golgi complex of the mouse gallbladder epithelium during fasting,refeeding, and gallstone formation

Summary The mouse gallbladder epithelium was studied with light microscopic autoradiography and quantitative electron microscopy during fasting, refeeding and experimental gallstone formation. To determine the intracellular pathway of glycoproteins, H³-galactose was injected at different time intervals into the mice. At 10, 25 and 40 min after an intraperitoneal injection the gallbladders were fixed and prepared for light microscopy. As early as 10 min after injection, label was observed in supranuclear cytoplasmic regions and at 25 min, an increased radioactivity was present throughout the apical cytoplasm. At 40 min, silver grains were mainly present at the cell surface. Autoradiographs processed 25 min after an intraperitoneal H³-galactose injection after fasting for 48 h showed decreased supranuclear and apical radioactivity. After refeeding (12 h) there was an enhanced activity in both these regions. Animals fed a lithogenic diet for one month showed a marked increase of radioactive label mainly in cells of crypts and invaginations of the mouse gallbladder mucosa.Morphometric measurements of the Golgi apparatus revealed that deprivation of food significantly diminished the volume density of the Golgi apparatus. Refeeding the animals restored the volume density values to normal levels. In the course of gallstone formation there was a further significant increase in the volume density of the Golgi complexes as compared to controls.     

Regional differences in the ultrastructure of Purkinje cells of the rat

Summary In the albino rat, perikaryal diameter, volume density of the granular endoplasmic reticulum and Golgi apparatus, and lumenal diameter of cisternae of the granular endoplasmic reticulum are larger in Purkinje cells of lobule Via (neocerebellum) than in those of lobule X (archicerebellum). In contrast, only the surface density of cisternae of the granular endoplasmic reticulum is larger in Purkinje cells of lobule X. The cisternae of granular endoplasmic reticulum are arranged into conspicuous Nissl bodies parallel to the nuclear membrane, but the content of ribosomes and polysemes is markedly less in lobule-X cells than in cells from lobule VI a. These results indicate qualitative and quantitative differences between the metabolically important organelles in Purkinje cells of the neo- and archicerebellum (cf. Larsell 1952).Supported by a grant from the Deutsche Forschungsgemeinschaft (La 184/7)     

Preparation and discharge of secretion in the subcommissural organ of the rat

Summary The secretion of the subcommissural organ (SCO) of the rat was studied by means of immunocytochemistry at the electron-microscopic level with the use of (1) the polar embedding medium Lowicryl K4M at -30° C, (2) the protein A-gold technique, and (3) a rabbit antiserum against bovine Reissner's fiber (see Sterba et al. 1981).Two different substructures of the ependymal and the hypendymal SCO-cells display a positive immunocytochemical reaction: (1) sacs containing flocculent secretion, which originate from the granular endoplasmic reticulum, and (2) vacuoles filled with fine granular secretion, which are pinched off from the Golgi apparatus. The secretory material of the sacs and the vacuoles is discharged both (i) apically into the cerebrospinal fluid and (ii) basally into intercellular spaces of the SCO-hypendyma. The apically released secretion is condensed to a lamina-like formation, which more caudally assumes the form of Reissner's fiber. The route of the basally released secretion remains, however, vague. The periodically striated bodies, which were thought to be morphological mediators of the discharge of the secretion into the capillaries, are never labeled by gold particles.Supported by grants from the Ministry for Science and Technology of the German Democratic RepublicThe expert technical assistance of Mrs. B. Wolff, Mrs. S. Mehnert, Mrs. E. Siebert, Mrs. Ch. Schneider, and Mrs. I. Seifert is gratefully acknowledged     

Reactions of neural elements of neocortex to action of hypoxia at the early neonatal period in rats

We studied reactions of neural elements from different neocortex regions (sensorimotor, visual, auditory) to acute normobaric hypoxia on the model of human incomplete pregnancy (the 2-day-old rat pups) and revealed similar and unidirectional reorganization in all these regions. The chosen parameters of hypoxia induced the earliest detectable changes as fast as in a day since exposure: a decrease in cell body size and cytoplasmic volume, intensification of apoptotic cell death. By the end of the neonatal period (day 5), several ultrastructural changes were observed by indicating deceleration of processes of nerve cell differentiation: arrest of complication of smooth and rough endoplasmic reticulum and Golgi apparatus, the reduced number of free ribosomes and polysomes in cytoplasm as well as of axonal and dendritic growth cones in neuropil, delayed and disordered myelination of nerve fibers. All these morphofunctional abnormalities may be the structural basis for development of neonatal encephalopathies.     

The frontal ganglion of Periplaneta americana L. (insecta)

Summary The frontal ganglion, part of the stomatogastric nervous system, contains about 60 to 80 neurons, 25 to 30 m in diameter. A well developed Golgi system, producing dense-core vesicles, lysosomes, multivesicular bodies and dense bodies are abundant. Glia elements are sparsely distributed. Many nerve fibres contain granules of different size and electron density. Five groups of fibres can be distinguished: Fibres with granules of about 200 nm (type A), fibres with granules of about 160 to 170 nm (type B), fibres with granules of about 80 to 100 nm (type C) and those with synaptic vesicles of 50 nm (type D) respectively. A fifth very small type contains neither vesicles nor granules. Special attention was paid to synaptic contacts. The divergent dyad seems to be the main type in the frontal ganglion. Frequently, neurosecretory endings are observed in presynaptic position. Immunocytochemical staining of neurosecretory material closely corresponds to the distribution of type A fibres, as observed electron microscopically. Immunoelectrophoresis of extracts from frontal ganglia with polyspecific anti-neurosecretion-serum reveals a single precipitation line, indicating that the immunocytochemical localization of neurosecretory material is due to reaction with a specific as well as a crossreagent antibody.Supported by the Ministerium für Wissenschaft und Technik der DDRThe authors wish to thank Mrs. B. Cosack and Mrs. A. Schmidt for excellent technical assistance     

THE FINE STRUCTURE OF THE PURKINJE CELL

This paper describes the fine structure of the Purkinje cell of the rat cerebellum after fixation by perfusion with 1 per cent buffered osmium tetroxide. Structures described include a large Golgi apparatus, abundant Nissl substance, mitochondria, multivesicular bodies, osmiophilic granules, axodendritic and axosomatic synapses, the nucleus, the nucleolus, and the nucleolar body. A new and possibly unique relationship between mitochondria and subsurface cisterns is described. Possible functional correlations are discussed.     

Inhibition of Golgi-apparatus function by brefeldin A in maize coleoptiles and its consequences on auxin-mediated growth,cell-wall extensibility and secretion of cell-wall proteins

Brefeldin A (BFA), a fungal metabolite causing dysfunction of the Golgi apparatus in plant and animal cells, was used to investigate the role of secretory processes at the plasma membrane in auxin-mediated elongation growth of maize (Zea mays L.) coleoptiles. In abraded coleoptile segments BFA produced, within less than 30 min, a decrease in the incorporation of [³H]leucine into tightly bound cell-wall proteins, accompanied by an increased incorporation into the intracellular pool of putative cell-wall glycoproteins. Total protein synthesis was not affected. Electron micrographs revealed striking morphological changes in dictyosomes (especially vesiculation of trans-cisternae), accumulation of Golgi vesicles and dilation of the endoplasmic reticulum. These effects are taken as indication that BFA interferes with the secretion of cell-wall components. Elongation growth of coleoptile segments in the presence and absence of auxin was inhibited by 80% in 20 mg·l^–1 BFA. If BFA was applied to segments growing in the presence of auxin, maximum inhibition was reached after about 30 min, indicating that the growth response depends on an uninterrupted supply of a cell-wall or plasma-membrane component (wall-loosening factor) delivered by the secretory pathway. After its secretion, this factor has a rather short growth-effective life time. The inhibition of auxin-mediated growth by BFA was accompanied by an elimination of auxin-induced cell-wall extensibility and by an inhibition of auxin-induced proton excretion. Fusicoccin-induced proton excretion was similarly affected by BFA. It is concluded that both the wall-loosening process underlying elongation growth as well as proton excretion depend on an intact secretory pathway from the Golgi apparatus to the cell wall; however, a causal relationship between these processes is not warranted by the data.Abbreviations BFA brefeldin A - FC fusicoccin - TCA trichloroacetic acid - WLF wall-loosening factor Supported by Deutsche Forschungsgemeinschaft (SFB 206). We thank Ms. B. Huvermann and Mrs. C. Plachy for conducting growth and proton excretion measurements.     

Ultrastructural localization of some phosphatases in the prothoracic gland of the insect Leucophaea Maderae

Summary The cytochemical localization of acid phosphatase and thiamine pyrophosphatase activity was studied by light and electron microscopy in prothoracic gland cells of the cockroach Leucophaea moderae. Nymphal and young adult animals were used.Prominent sites of acid phosphatase activity included large membrane-bounded dense bodies or lysosomes, and certain cisternae of the Golgi apparatus. The results suggest a possible difference in the enzymatic activity toward glycerophosphate and aromatic phosphates as substrates.Thiamine pyrophosphatase activity was localized in elements of the Golgi apparatus and endoplasmic reticulum, and in lysosome-like dense bodies. This latter activity was abolished by sodium fluoride treatment, whereas the phosphatase activity in the Golgi apparatus and endoplasmic reticulum is unaffected by such inhibition.The cytochemical results confirm through direct evidence the suggestions of Scharrer (1964), that the large dense bodies present in the prothoracic gland cells are lysosomes, and that their activity may be related to stages in the life history of the glands. Furthermore, the lysosomes or their derivative structures may play an essential role in the autolysis of the prothoracic glands toward the end of their active period.The enzymatic activity of the endoplasmic reticulum may indicate the involvement of this organelle in the metabolism of steroid-like precursor materials necessary for the synthesis of ecdysone.This study was supported by U.S.P.H.S. grants 5 T1-MH-6418 and NB-05219, and grant RO 1-AM-3984 to Dr. Berta Scharrer. I would like to express my appreciation to Dr. Scharrer for her encouragement and assistance during this study. I also wish to thank Mrs. Sarah Wurzelmann for her competent technical aid.     

Tubuloampullar structures associated with the endoplasmic reticulum in pancreatic B-cells

Summary Unusual aggregations of ampullar dilated tubules (tubuloampullar structures, TAS) were observed in pancreatic B-cells of rats and in one case of human malignant insulinoma. The TAS were invariably associated with dilated rough endoplasmic reticulum, but lacked ribosomes. They were frequently seen to be closely associated with the Golgi apparatus. Furthermore, TAS were located mainly in degranulated areas of B-cells.Dedicated to Prof. W. Graumann on the occasion of his 65th birthdayThe expert assistance of Mrs. M. Tölken is gratefully acknowledgedThis work was supported in part by the deutsche Forschungsgemeinschaft, Re 225/7 and Kl 426/1     

Relationships between membranous organelles in amoebae studied by electron microscopic cytochemical staining

Summary The intracellular location of a variety of enzymes was studied in Amoeba proteus with the use of electron microscopic cytochemical methods, in an attempt to assess the relationships between different membranous organelles. One group of enzymes, including nucleoside diphosphatases (IDPase, UDPase, GDPase, ADPase), carbamoyl phosphatase, alkaline phosphatase, and BAXD oxidase was localized mainly in the rough endoplasmic reticulum, nuclear envelope, and convex side of the Golgi apparatus. Esterase activity had a similar localization except that the Golgi apparatus was "stained" throughout most of its extent. A second group of enzymes was found in Golgi cisternae and vesicles, and in some vacuoles. This group included acid phosphatase, thiamine pyrophosphatase, and aryl sulfatase. Some enzymes previously detected in cytoplasmic membranes of other cells, including glucose-6-phosphatase, showed little or no activity in amoebae. The results suggest that there are chemical similarities and probable functional relationships between the rough endoplasmic reticulum, the nuclear envelope, and the convex side of the Golgi apparatus. On the other hand, the concave pole of the Golgi apparatus, aggregates of smooth tubules and vesicles, and the cell surface appear more closely related to one another than to the endoplasmic reticulum and the convex side of the Golgi apparatus. The cytochemical similarity between the Golgi apparatus and certain vacuoles such as food vacuoles may reflect the role of the Golgi apparatus in the formation of lysosomes. The locations of reaction products of the various enzymes in amoebae are compared with observations reported for other cell types.Supported by a research grant (VC-169) from the American Cancer SocietyThe author is indebted for technical assistance to Mrs. Sue Thompson and Mrs. Christine Folsom-Kovarik     

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     

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