Electron microscopic and cytochemical studies of the mouse subcommissural organ

Summary In mice most of the ependymal cells of the subcommissural organ (SCO cells) are densely packed with dilated cisternae of the endoplasmic reticulum (ER) containing either finely granular or flocculent materials. The well developed supra-nuclear Golgi apparatus consists of stacks of flattened saccules and small vesicles; the two or three outer Golgi saccules are moderately dilated and exhibit numerous fenestrations; occasional profiles suggesting the budding of coated vesicles and formation of membrane-bound dense bodies from the ends of the innermost Golgi saccules are seen. A few coated vesicles and membrane-bound dense bodies of various sizes and shapes are also found in the Golgi region.The contents of the dilated ER cisternae are stained with periodic acid-silver methenamine techniques. In the Golgi complex the two or three inner saccules are stained as deeply as the dense bodies, and the outer saccules are only slightly stained. The stained contents of ER cisternae are more electron opaque than those of the outer but less opaque than those of the inner Golgi saccules and the dense bodies.Acid phosphatase activities are localized in the dense bodies, some of the coated vesicles in the Golgi region, and in the one or two inner Golgi saccules.On the basis of these results the following conclusions have been reached: (1) In mouse SCO cells the finely granular and the flocculent materials in the lumen of ER cisternae contain a complex carbohydrate(s) which is secreted into the ventricle to form Reissner's fiber; (2) the secretory substance is assumed to be synthesized by the ER and stored in its cisternae, and the Golgi apparatus might play only a minor role, if any, in the elaboration of the secretory material; (3) most of the dense bodies in the mouse SCO cells are lysosomal in nature instead of being so-called dark secretory granules.Sponsored by the National Science Council, Republic of China.     

Virus-neuron interactions in the mouse brain infected with Japanese encephalitis virus

The virus-host interactions between Japanese encephalitis (JE) virus and mouse brain neurons were analyzed by electron microscopy. JE virus replicated exclusively in the rough endoplasmic reticulum (RER) of neurons. In the early phase of infection, the perikaryon of infected neurons had relatively normal-looking lamellar RER whose cisternae showed focal dilations containing progeny virions and characteristic endoplasmic reticulum (ER) vesicles. The reticular RER, consisted of rows of ribosomes surrounding irregular-shaped, membrane-unbounded cisternae and resembled that observed in JE-virus-infected PC12 cells, were also seen adjacent to the lamellar RER. The appearance of the reticular RER indicated that RER morphogenesis occurred in infected neurons in association with the viral replication. The fine network of Golgi apparatus was extensively obliterated by fragmentation and dissolution of the Golgi membranes and their replacement by the electron-lucent material. As the infection progressed, the lamellar RER was increasingly replaced by the hypertrophic RER which had diffusely dilated cisternae containing multiple progeny virions and ER vesicles. The Golgi apparatus, at this stage, was seen as coarse, localized Golgi complexes near the hypertrophic RER. In the later phase of infection, RER of infected neurons showed a degenerative change, with the cystically dilated cisternae being filled with ER vesicles and virions. Small, localized Golgi complexes frequently showed vesiculation, vacuolation, and dispersion. The present study, therefore, indicated that during the viral replication the normal lamellar RER which synthesized neuronal secretory and membrane proteins was replaced by the hypertrophic RER which synthesized the viral proteins. The hypertrophic RER eventually degenerated into cystic RER whose cisternae were filled with viral products. The constant degenerative change which occurred in the Golgi apparatus during the viral replication suggested that some of the viral proteins transported from RER to the Golgi apparatus were harmful to the Golgi apparatus and that increasing damage to the Golgi apparatus during the viral replication played the principal role in the pathogenesis of JE-virus-infected neurons in the central nervous system.     

Immunoenzyme localization of cathepsins in the Golgi region of rat hepatocytes and renal tubule cells

Summary Localization of carboxyl proteinase (cathepsin D) and cysteine proteinases (cathepsins B, H, and L) in Golgi region was studied using an immunoenzyme technique. Rat livers and kidneys were used. The results obtained from the livers were similar to those from the kidneys. All cathepsins were detected in lysosomal compartments such as secondary lysosomes, multivesicular bodies (endosomes), and autophagosomes. Rough endoplasmic reticulum (rER), including nuclear envelope was focally stained. Most of Golgi cisternae were negative, but sometimes only one cisterna or the terminal portion of the cisterna were stained focally. Rarely, the trans Golgi network (TGN) was positive for the proteinases. Among numerous Golgi vesicles, only a few of them were stained. The positive vesicles were divided into two groups, one had a bristle coat and heavily stained, and other were smaller than 40 nm in diameter and weakly stained. The small vesicles seemed to bud from the ER and to fuse with the Golgi cisternae, while the large clathrin-coated vesicles seem to bud from the TGN. The results suggests that cathepsins are transported by vesicular system from the rER to lysosomes via Golgi apparatus. In addition, it is suggested that the small vesicles transport the proteinases from the ER to the Golgi cisternae and the large clathrin-coated vesicles from the Golgi cisternae to the lysosomes.     

The effect of castration upon the ultrastructure of the rat hypothalamus

Summary The neurosecretory hypothalamic nuclei and the inner zone of the median eminence of castrated rats were studied under the electron microscope. After one month of castration all the neurosecretory neurons of both nuclei show signs of hyperactivity characterized by dilated cisternae of the endoplasmic reticulum containing a macromolecular filamentous material and an increase in the number of ribosomes. After six months of castration, some neurosecretory neurons show an increased number of neurotubules and larger lysosomes than in the controls. Other neurons show a very significant hypertrophy of the endoplasmic reticulum, with large amounts of intracisternal filamentous material. These cells have few neurosecretory granules and in the adjacent synapses the number of granulated vesicles is increased. In the supraoptic nucleus there are two kinds of neurosecretory axons: the clear ones, which are similar to those that appear in control animals and the dark ones, which have smaller elementary granules. In the inner zone of the median eminence the axons show an increase in the number of neurosecretory granules with respect to the controls. After supplementary administration of sexual hormones, all the modifications produced by castration disappear. The ultrastructural changes observed in the neurosecretory nuclei after castration are discussed in relation to those previously described in the neurohypophysis under the same experimental conditions. A feedback regulatory action of sex hormones on hypothalamic neurosecretory neurons is postulated.Supported by grants from the Consejo Nacional de Investigaciones Científicas y Técnicas and by the Air Force Office of Scientific Research (AF-AFOSR 963-67).We are deeply indebted to Mrs. Defilippi-Novoa and Mr. Alberto Saenz for their skillful assistence.     

Immunoenzyme localization of cathepsins in the Golgi region of rat hepatocytes and renal tubule cells

Localization of carboxyl proteinase (cathepsin D) and cysteine proteinases (cathepsins B, H, and L) in Golgi region was studied using an immunoenzyme technique. Rat livers and kidneys were used. The results obtained from the livers were similar to those from the kidneys. All cathepsins were detected in lysosomal compartments such as secondary lysosomes, multivesicular bodies (endosomes), and autophagosomes. Rough endoplasmic reticulum (rER), including nuclear envelope was focally stained. Most of Golgi cisternae were negative, but sometimes only one cisterna or the terminal portion of the cisterna were stained focally. Rarely, the trans Golgi network (TGN) was positive for the proteinases. Among numerous Golgi vesicles, only a few of them were stained. The positive vesicles were divided into two groups, one had a bristle coat and heavily stained, and other were smaller than 40 nm in diameter and weakly stained. The small vesicles seemed to bud from the ER and to fuse with the Golgi cisternae, while the large clathrin-coated vesicles seem to bud from the TGN. The results suggests that cathepsins are transported by vesicular system from the rER to lysosomes via Golgi apparatus. In addition, it is suggested that the small vesicles transport the proteinases from the ER to the Golgi cisternae and the large clathrin-coated vesicles from the Golgi cisternae to the lysosomes.     

Cytomembranes in first cleavage xenopus embryos

Summary The ultrastructure and interrelationships of the Golgi body, endoplasmic reticulum and lipid droplets have been studied in the first cleavage Xenopus embryos. Lipid droplets, usually spherical or sometimes multilobed, did not have a discernible limiting membrane, although some had an incomplete electron dense partition. The Golgi bodies and endoplasmic reticulum were seen continuous with lipid droplets and the profiles indicated a probable formation of these membranes from lipid droplet material. Rough endoplasmic reticulum (ER) mainly consisted of paired tubular cisternae and vesicles containing filamentous material that gave a fringed appearance. The relationships of paired cisternae with the Golgi body suggested a transformation of ER membranes into the Golgi body membranes. In addition, paired ER cisternae showed a close apposition with the limiting membrane of the yolk platelet. Lone ER cisternae that contained moderately electron dense material instead of filaments were also present and showed numerous associated vesicles near the Golgi body. The Golgi body showed several morphological forms including a single fenestrated cisterna, two to four flat or cup-shaped cisternae, or up to seven cisternae, some of which were dilated and similar to fringed ER in appearance. These forms could be different developmental stages of the organelle. Coated vesicles were seen continuous with the cisternae of the Golgi body. A probable route for the assembly of the cell surface material has been proposed.This work was supported by a grant from the Medical Research Council of Canada to one of us (E.J.S.).     

Evidence for local corticotropin releasing factor (CRF)-immunoreactive neuronal circuits in the paraventricular nucleus of the rat hypothalamus

Summary The interrelationships of corticotropin-releasing factor (CRF) immunoreactive neuronal cell bodies and processes have been examined in the paraventricular nucleus (PVN) of adrenalectomized-dexamethesone treated rats. Antisera generated against ovine CRF (oCRF) were used in the peroxidase-anti-peroxidase-complex (PAP)-immunocytochemical method at both the light and electron microscopic levels. In this experimental model, a great number of CRF-immunoreactive neurons were detected in the parvocellular subdivisions of the PVN and a few scattered labelled parvocellular neurons were also observed within the magnocellular subunits. Characteristic features of immunolabeled perikarya included hypertrophied rough endoplasmic reticulum with dilated endoplasmic cisternae, well developed Golgi complexes and increased numbers of neurosecretory granules. These features are interpreted to indicate accelerated hormone synthesis as a result of adrenalectomy. Afferent fibers communicated with dendrites and somata of CRF-immunoreactive neurons via both symmetrical and asymmetrical synapses. Some neurons exhibited somatic appendages and these structures were also observed to receive synaptic terminals. Within both the PVN and its adjacent neuropil, CRF-immunoreactive axons demonstrated varicosites which contained accumulations of densecore vesicles. CRF-containing axons were observed to branch into axon collaterals. These axons or axon collaterals established axo-somatic synapses on CRF-producing neurons in the parvocellular regions of the PVN, while in the magnocellular area of the nucleus they were found in juxtaposition with unlabeled magnocellular neuronal cell bodies or in synaptic contact with their dendrites. The presence of CRF-immunoreactive material in presynaptic structures suggests that the neurohormone may participate in mechanisms of synaptic transfer.These ultrastructural data indicate that the function of the paraventricular CRF-synthesizing neurons is adrenal steroid hormone dependent. They also provide morphological evidence for the existence of a neuronal ultrashort feedback mechanism within the PVN for the regulation of CRF production and possibly that of other peptide hormones contained within this complex.Supported by NIH grant NS 19266 to WKP     

Evidence for local corticotropin releasing factor (CRF)-immunoreactive neuronal circuits in the paraventricular nucleus of the rat hypothalamus. An electron microscopic immunohistochemical analysis

The interrelationships of corticotropin-releasing factor (CRF) immunoreactive neuronal cell bodies and processes have been examined in the paraventricular nucleus (PVN) of adrenalectomized-dexamethasone treated rats. Antisera generated against ovine CRF (oCRF) were used in the peroxidase-anti-peroxidase-complex (PAP)-immunocytochemical method at both the light and electron microscopic levels. In this experimental model, a great number of CRF-immunoreactive neurons were detected in the parvocellular subdivisions of the PVN and a few scattered labelled parvocellular neurons were also observed within the magnocellular subunits. Characteristic features of immunolabeled perikarya included hypertrophied rough endoplasmic reticulum with dilated endoplasmic cisternae, well developed Golgi complexes and increased numbers of neurosecretory granules. These features are interpreted to indicate accelerated hormone synthesis as a result of adrenalectomy. Afferent fibers communicated with dendrites and somata of CRF-immunoreactive neurons via both symmetrical and asymmetrical synapses. Some neurons exhibited somatic appendages and these structures were also observed to receive synaptic terminals. Within both the PVN and its adjacent neuropil, CRF-immunoreactive axons demonstrated varicosites which contained accumulations of densecore vesicles. CRF-containing axons were observed to branch into axon collaterals. These axons or axon collaterals established axo-somatic synapses on CRF-producing neurons in the parvocellular regions of the PVN, while in the magnocellular area of the nucleus they were found in juxtaposition with unlabeled magnocellular neuronal cell bodies or in synaptic contact with their dendrites. The presence of CRF-immunoreactive material in presynaptic structures suggests that the neurohormone may participate in mechanisms of synaptic transfer. These ultrastructural data indicate that the function of the paraventricular CRF-synthesizing neurons is adrenal steroid hormone dependent. They also provide morphological evidence for the existence of a neuronal ultrashort feed-back mechanism within the PVN for the regulation of CRF production and possibly that of other peptide hormones contained within this complex.     

Localization of fucosyl residues in cellular compartments of rat duodenal absorptive enterocytes and goblet cells

We have determined the subcellular distribution of fucosyl residues in rat duodenal absorptive enterocytes and goblet cells, using the binding affinity of the lectin I of Ulex europaeus (UEA I). In absorptive enterocytes, UEA I-lectin gold complexes were detected at the brush border and at the basolateral plasma membrane; pits of the plasma membrane were labeled, as were small vesicles, multivesicular bodies, lysosomes, and the Golgi apparatus. In the Golgi stacks, about half of the cisternae showed gold marker particles: accessible fucosyl residues were sparse in the cis subcompartment, the cismost cisterna mostly remaining negative; more intense label was found in medial cisternae; reactions were concentrated in the trans and transmost Golgi subcompartments. Cisternae, tubules and vesicles located at the trans Golgi side were the most constantly and intensely stained Golgi elements. In goblet cells, mucin granules and trans Golgi cisternae were labeled. Rarely, UEA I-gold bound to cisternae of the medial subcompartment; the cis subcompartment remained unstained. In part, UEA I-gold particles were restricted to dilated portions of the transmost Golgi cisterna and to secretory granules.     

Ultrastructure of the pea cotyledon Golgi apparatus: Origin of dense vesicles and the action of brefeldin A

Summary We have followed the action of brefeldin A (BFA) on the Golgi apparatus of developing pea cotyledons, the cells of which are actively engaged in the synthesis and deposition of storage proteins. The Golgi apparatus of normal cells is characterized by the presence of three different types of vesicle: smooth-surfaced secretory vesicles, dense vesicles which carry the storage proteins, and clathrin-coated vesicles (CCV). The dense vesicles originate at the cis cisternae and undergo a maturation as they pass through the Golgi stack, presumably as a result of cisternal progression. CCV bud off from dense and smooth vesicles, which may be attached to one another, at the trans pole of the Golgi apparatus. BFA eliminates the CCV and leads, initially, to an increase in the number and length of the cisternae. Dense vesicles are still to be seen, and many show an increase in diameter. Longer BFA treatments result in a trans-driven vesiculation and an accumulation of vesicles within the vicinity of single cisternae. The vesicles were sometimes seen to be connected to one another via a network of tubules. As judged by immunocytochemistry with gold-coupled legumin and vicilin antisera, some of the dilated vesicles originate directly from dense vesicles by swelling whereas others probably arise by dilation of Golgi cisternae since they possess a layer of flocculent storage proteins at their periphery. By contrast the centre of the dilated vesicles labels positively with antibodies against complex glycans, indicating that the ability to segregate storage proteins from cell wall or lytic vacuole glycoproteins is lost during extended BFA treatment. The effects of BFA are reversible when cotyledons are further incubated on Gamborg's medium for 5 h without the inhibitor.Dedicated to Professor R. Kollmann on the occasion of his 65th birthday.     

Effects of castration and of oestradiol treatment on the subcellular structure of the mouse seminal vesicles, with particular reference to the function of the Golgi apparatus and the lysosomes

Synopsis A number of changes were observed in the ultrastructure of seminal vesicles from castrated mice fed continuously with oestradiol. Treatment for two weeks was accompanied in the epithelial cells by the disappearance of secretion droplets, swelling of the Golgi structures and the appearance of many dense bodies and vesicles of various sizes. Subsequently, there was a decrease in the amount of rough endoplasmic reticulum followed by the disappearance of the vesicles. These changes were paralleled by a decrease in size and, finally, disappearance of the dense bodies, and by the appearance of abnormal nuclei. Ultimately, the epithelial cells became packed with free ribosomes and keratinization of the epithelium ensued.These metaplastic phenomena in the epithelium were accompanied by thickening and infolding of the basement membrane and by the formation of several layers of smooth muscle cells. The latter cells were very abnormal in that they contained prominent Golgi apparatuses and a vesiculated cytoplasm.When vesiculation occurred, both in the epithelium and in the cells of the basal areas of the acini (myoepithelial, basal and muscle cells), the vesicles, the Golgi bodies and the dense bodies (lysosomes) contained acid naphthol-AS-phosphatase activity. This enzyme was different from the more commonly described lysosomal acid -glycerophosphatase in that it was not inhibited by either sodium fluoride or sodium molybdate; in certain instances its activity in the cisternae of the endoplasmic reticulum could be shown to be enhanced by these compounds. The significance of these findings is discussed.     

Effects of colchicine on axonal transport and ultrastructure of the hypothalamo-neurohypophyseal system of the rat

Summary The effect of colchicine on the transport of proteins in the hypothalamo-neurohypophyseal tract of the rat was studied after injection of (³⁵S) cysteine into the supraoptic nucleus (SON) region. Colchicine, dissolved in distilled water and administered subarachnoidally, inhibited the axonal transport of labelled proteins into the neurohypophysis: the radioactivity that was recovered in neurohypophyseal TCA precipitable material was markedly decreased and hardly any radioactivity was found in the neurohypophyseal proteins which were separated by polyacrylamide gel disc electrophoresis.As revealed by electron microscopy the SON cell bodies showed marked changes after treatment with colchicine: a deeply folded nucleolemma; a pronounced, granular nucleolus; a dispersed chromatin; a zonal distribution of cell organelles with mitochondria and lysosomes accumulated at the periphery, crowded ribosomes, often arranged as polyribosomes and richly branching short profiles of endoplasmic reticulum filled with filamentous material forming an inner perinuclear zone separated by enlarged Golgi complexes.The profiles of elongated Herring bodies in the infundibulum were increased. The axon terminals were filled with heavily osmiophilic neurosecretory granules. The neurofilaments were slightly or moderately increased in number. No apparent changes were observed with regard to the neurotubuli in the SON neurons. The glial cells of the supraopticoneurohypophyseal tract showed reactive changes with a proliferation of filamentous elements. The biochemical and ultrastructural findings are discussed especially with respect to the mechanisms of transport and release of neurosecretory granules.     

Ultrastructural alterations of the paraventriculo-infundibular Corticotropin Releasing Factor (CRF)-immunoreactive neuronal system in long term adrenalectomized rats

The corticotropin releasing factor (CRF)-immunoreactive paraventriculo-infundibular neuronal system of long-term adrenalectomized and adrenalectomized-short term dexamethasone treated rats was analyzed at the ultrastructural level using the preembedding peroxidase anti-peroxidase complex (PAP)-immunohistological method. In both groups of animals, parvocellular neurons located in the medial and dorsal subnuclei of the paraventricular nucleus (PVN) showed CRF-like immunoreactivity. The perikarya contained hypertrophied rough endoplasmic reticulum (rER) with dilated cisternae, active Golgi-complexes and numerous neurosecretory granules. The majority of the neurosecretory granules measured 80–120 nm. Dendrites of CRF-immunoreactive neurons contained labeled vesicles, secretory granules, bundles of microtubules, a well-developed smooth endoplasmic reticulum (sER) complex and free ribosomes. Unlabeled terminal boutons of axons were observed to synapse on dendrites and somata of CRF-neurons. In addition, CRF perikarya were found in direct somato-somatic apposition with both CRF-immunopositive and immunonegative parvocellular cells. Retraction of glial processes and the existence of puncta adherentia between the cell membranes characterized these appositions. Varicose CRF axons within the median eminence contained hypertrophied sER, labeled vesicles and neurosecretory granules. The preterminal portions of the CRF-axons were dilated and possessed many labeled 80–120 nm diameter granules. CRF-terminals were greatly enlarged and established direct neurohemal contacts with the external limiting basal lamina of portal vessels without the interposition of tanycytic ependymal foot-processes. These tanycytes were not CRF immunopositive. CRF positive terminals contained clusters of microvesicles, labeled small vesicles and multivesicular bodies, but fewer granular elements than were observed within the preterminals. Many of the labeled organelles were attached to tubules of sER. Occasionally, CRF-axons were observed within the pericapillary space adjacent to portal vessels. The ultrastructural features of CRF-neurons, obtained from adrenalectomized and adrenalectomized plus short-term dexamethasone treated rats did not differ significantly from each other. The hormone content of the entire CRF-neuron was greater in the steroid treated group. Adrenocorticotrophic hormone (ACTH) synthesizing cells in the pars distalis of adrenalectomized-dexamethasone treated rats also showed increased numbers of immunopositive secretory granules (150–320 nm in diameter). These ultrastructural morphological results provide evidence that the function of the paraventriculo-infundibular CRF-system is adrenal steroid hormone dependent and suggest the participation of glial and ependymal elements in the regulation of the system in this hyperfunctional state. The observed membrane specializations are indicative of ephaptic interactions between CRF-neurons and may serve a synchronizing function in adrenalectomized animals.     

Effects of Brefeldin A on the Golgi complex, endoplasmic reticulum and viral envelope glycoproteins in murine erythroleukemia cells

This report concerns the effects of Brefeldin A (BFA): i) on the Golgi complex and the ER of retrovirus-transformed murine erythroleukemia (MEL) cells and, ii) on the viral proteins these cells express. Golgi complexes were extensively disorganized by BFA. Within 5 min, most stacked cisternae were converted to vesicles scattered throughout the centrosphere region. By 30 min, the Golgi complexes were completely disassembled. Only clusters of small vesicles ("Golgi remnants") persisted in the vicinity of the centrioles and microtubule-organizing centers. Some of these small vesicles had a simple coat structure on their membranes. Over the next 1 to 2 h of BFA treatment, the number of vesicles in the Golgi area decreased concomitantly with the expansion of a predominantly smooth membrane portion of the ER, consisting of a network of dilated tubules in continuity with regular RER cisternae, annulate lamellae and the nuclear envelope. By electron microscopy, viral glycoproteins appeared to accumulate on the membranes of this network, and immature virions were found to bud preferentially into its cisternal space. Viral accumulations increased with time under BFA. The rest of the RER appeared normal, apparently unaffected by the drug. Preferential virion budding suggests that this expanding network is a chemically differentiated part of the ER. By immunofluorescence, antibodies to viral envelope proteins gave a punctate staining at the surface of control cells, presumably in the areas of virion budding, whereas relatively large intracellular masses of antigens were found in BFA-treated cells. We assume that these masses represent the differentiated parts of the ER. Taken together, these findings suggest that BFA blocks intracellular transport of newly synthesized cellular and viral proteins immediately distal to the distinct compartment of the ER in which virion budding preferentially occurs. BFA effects are rapidly and fully reversible. Within 1 min of the removal of the drug, stacks of Golgi cisternae began to reappear in the vicinity of the centrioles, and by 30 min, Golgi complexes regained their normal structural appearance.     

Postnatal development of the Mongolian gerbil uterus

The postnatal development of the gerbil uterus has been investigated. Special attention has been paid to the luminal surface epithelium. In the newborn gerbil, the uterus contains already some fluid and the uterine luminal epithelium seems to possess mechanisms for the regulation of the fluid contents. Among them are apical protrusions and microvilli, endo- and exocytotic vesicles of different nature, highly active Golgi complexes and dilated rER vesicles and also very distinct junctional complexes between the cells in the apical areas.     

Cytochemical ultrastructural study of the glycoproteins in the rat hypothalamo-post-pituitary complex]

The results obtained with various methods applied to the cytochemical detection of carbohydrates at an ultrastructural level, confirm the existence of glycoproteins in neurosecretory material in the neurohypophysis as well as in the hypothalamic magnocellular nuclei. This glycoproteic component, however, is not present in all the secretory granules and, according to their cytochemical behaviour, it is possible to distinguish two types of neurosecretory fibres: one where all the granules respond negatively; the other where most of the granules are reactive. The existence of two types of neurons corresponding to these two fibres cannot yet be asserted, but seems very likely, perhaps connected with the hormonal duality of the magnocellular nuclei. The reactions are also positive on the Golgi apparatus, in accordance with its function in glycoprotein synthesis. But the difference of reactivity between the Golgi cisternae and the neurosecretory product suggests that glycoprotein synthesis is still going on in the neurosecretory granules outside the Golgi area.     

The cytology of the testaceous rhizopod Lesquereusia spiralis (Ehrenberg) Penard. I. Ultrastructure and shell formation

Ultrastructure and shell formation in the testaceous ameba, Lesquereusia spiralis, were investigated with both scanning and transmission electron microscopy and X-ray microanalysis. The nucleus, surrounded by a fibrous lamina, contains multiple nucleoli. The cytoplasm, containing a well developed granular endoplasmic reticulum, also contains remnants of starch granules in stages of digestion. Spherical aggregates of ribosome-like particles may be seen. Golgi complexes seem to produce both a nonordered fibrous material and an electron dense vesicle. Only the latter appears to bleb off from the Golgi complex. X-ray microanalysis demonstration of silicon in Golgi vesicles and in some dense vesicles suggests that the fibrous component of the cisternae may take up and concentrate silica to form the electron-dense component of the vesicles. Membrane-bound siliceous crystals are often seen adjacent to the Golgi, suggesting either a Golgi origin or platelet formation in vesicles after release from the Golgi complex. Both electron-dense bodies and siliceous platelets are released from the cell by a process similar to apocrine secretion and may be seen outside the cell in route to the shell during shell morphogenesis. Shell development involves fusion of electron-dense bodies to form a matrix, positioning of siliceous platelets in this matrix parallel to the shell surface, and development of a system of matrix chambers. A particulate glycoconjugate is released to the shell surface upon rupture of the matrix chamber.     

Influence of gonadotropic hormones on the ultrastructure of rat pinealocytes

Summary The influence of gonadotropic hormones on the ultrastructure of rat pinealocytes was studied. Human chorionic gonadotropin (HCG) as well as pregnant mare serum gonadotropin (PMSG) caused a marked activation of pinealocytes. It is characterised by a conspicuous proliferation of the granular endoplasmic reticulum and Golgi apparatus as well as an increase in number of dense core vesicles, mitochondria, dense bodies, subsurface cisternae and vesicles in the terminal buds of pinealocyte processes. The changes after HCG administration were more pronounced than after PMSG.Supported by a grant from the Polish Academy of Sciences, No. 10.4.2.01.5.6     

Variations in the axon reaction after different types of nerve lesion. Light and electron microscopic studies on the facial nucleus of the rat

The retrograde nerve cell reaction was studied after evulsion, transection and crush lesion of the facial nerve in rats. Crush lesion caused barely discernible light and electron microscopic changes. The Nissl bodies became slightly smaller than normal and the arrangement of the granular endoplasmic reticulum (rER) somewhat more irregular. The crush lesions were followed by complete functional and morphologic recovery. After nerve evulsion, the cells showed severe chromatolysis, nuclear caps, nuclear eccentricity, and folding of the nuclear membrane. Ultrastructurally there was a dispersion of the rER and formation of laminated dense bodies. Lager, the rER was partly degranulated and some of the polyribosomes dissociated. These neurons ultimately disappeared. Transection of the nerve caused an intermediate axon reaction and a moderate loss of neurons. It is concluded that certain neurons may regenerate after axotomy in spite of minimal light and electron microscopic changes in the nerve cell bodies, and that the same neurons may show the typical axon reaction after more severe nerve injuries. Mechanisms which may be involved in the regulation of the retrograde nerve cell reaction after axotomy are briefly discussed.     

Annulate lamellae and whorl bodies in the diffuse supraoptic nucleus of the hamster

The ultrastructure of neurons of the diffuse supraoptic nucleus of the hamster has been studied. These neurons show two specializations of the endoplasmic reticulum: annulate lamellae and whorl bodies. From one to three whorl bodies are found in the same neuron. The annulate lamellae and the whorl body cisterns are continuous with the cisterns of the rough endoplasmic reticulum. These neurons present an extraordinarily developed rough endoplasmic reticulum, small mitochondria, neurosecretory vesicles and a Golgi complex filled with electron-dense material. Astrocytic processes of different thickness surround the neurosecretory cells.