A Golgi study of the parvocellular neurons in the paraventricular nucleus of the domestic fowl

The present study was focussed on the typology of small and medium-sized neurons in the hypothalamic paraventricular nucleus (PVN) of the domestic fowl as revealed by means of Golgi impregnation. This region is provided with different systems of neurons that can be distinguished on the basis of their location and dendritic morphology. Intraependymal neurons and CSF-contacting nerve cells are found in the periventricular layer together with bipolar elements endowed with processes extending parallel to the surface of the third ventricle. The short axons of these neurons may contact the magnocellular elements. Numerous isodendritic neurons are scattered throughout the entire PVN; these nerve cells possessing short and branched axons may be considered as local-circuit neurons. The complex intrinsic organization of the PVN of the domestic fowl might provide the structural basis for local interactions among the neuronal elements of this hypothalamic region.     

Extrusion of the residual body in spermatids of Ancylostoma caninum (Nematoda, Strongyloidea)

Transmission electron microscopy reveals that the spermatocytes of the hookworm Ancylostoma caninum contain an abundance of Golgi complexes, ribosomes, specialized membranous organelles, and long strands of smooth endoplasmic reticulum. These organelles remain abundant until the early spermatid stage of sperm development, when they reach their maximum abundance and maturity and the production of new ones ceases. Golgi complexes, ribosomes, and excess SER, which are not functional after this stage, become segregated and confined to the posterior portion of the spermatid in a polar lobe. Later, the polar lobe together with excess cytoplasmic matrix is bound by a membrane and dissociated from the spermatid as a residual body. The spermatid is then devoid of Golgi complexes and ribosomes. Formation of residual bodies as sperm cells mature may be considered a type of cell excretion.     

Fine structure and its functional properties of the ependymal cell in the frog median eminence

Summary Intercellular canaliculi surrounded by several ependymal cells, having numerous microvilli and a few cilia on the apical surface, are present throughout the frog median eminence. The intercellular canaliculi penetrate deeply near the portal vessel from the third ventricle. They are separated from the pericapillary space only by the thin cytoplasm of the ependymal cell.The cytoplasmic protrusions containing a large number of clear vesicles are often found at the apical surface of ependymal cells facing the third ventricle or the lumen of intercellular canaliculus. The ependymal cell shows well developed Golgi apparatus and well developed rough endoplasmic reticulum in its cytoplasm. Dense granules of about 1200–1500 A diameter suggesting secretory materials are found in small number near the Golgi apparatus and abundantly in the ependymal process lying around the portal vessel.Synaptic contacts between the ependymal cell and two different types of the nerve endings, monoaminergic and peptidergic, are frequently observed. A few small flasklike caveolae suggesting micropinocytosis are found in the post-synaptic membrane as well as in the lateral and basal plasma membranes of the ependymal cell. The author consideres that the ependymal cell in this region has secretory and transport (absorption) activities.     

Effects of acute opiate-peptide administration on pro-opiomelanocortin cells of the intermediate lobe of the rat pituitary

Summary The effects of acute injections of synthetic opiate peptides into the lateral cerebral ventricle of young adult male rats on cells of the intermediate lobe of the pituitary were studied. Met-enkephalin (100/g) injected into anesthetized rats, or 20 g beta-endorphin administered via a previously implanted cannula to unanesthetized animals, will lead to cell degranulation and often to expanded Golgi zones and prominent regions of rough endoplasmic reticulum in secretory cells when tissue is fixed 45–60 min after peptide administration. Treatment of animals with the opiate antagonist naloxone hydrochloride prior to enkephalin injection appeared to prevent the cellular changes elicited with peptide alone. Observations suggest that opiate peptides administered to the cerebrospinal fluid may stimulate release of pro-opiomelanocortin-peptide from pituitary cells.     

The relationship between the folliculo-stellate network and the thyrotropic cells of the avian adenohypophysis

Summary The folliculo-stellate network of the avian adenohypophysis consists of stellate cells surrounding colloid-containing follicular cavities into which cilia and microvilli project. Other identifying criteria are agranularity, junctional complexes at the apical pole, presence of cytoplasmic processes ramifying between adjacent secretory cells, and close appositions of plasma membranes linking folliculo-stellate cells and presumptive thyrotropic cells.Transmission electron microscopy reveals that TRH and L-DOPA induce simultaneous ultrastructural changes in the folliculo-stellate network and in the thyrotropic cells. TRH transforms at cell of the cephalic lobe into a highly hypertrophic cell in which enlargement of cisterns of rough endoplasmic reticulum containing secretory granules, development of a large Golgi complex, presence of newly synthesized secretory granules, and granulation of the cytoplasm are the main features. In the meantime, the follicular cavities become dilated by large amounts of homogeneous colloid. The administration of L-DOPA also leads to the development of dilated cisterns in presumptive thyrotropic cells of the cephalic lobe. Intracisternal granules, immature secretory granules, and large Golgi complexes, however, are not observed. Degranulation of the cytoplasm is obvious. The follicular cavities of both cephalic and caudal lobes are enlarged and filled with colloid in which granular elements are noted.The ultrastructural changes observed in thyrotropic cells and in the folliculo-stellate network reflect functional changes induced by the experimental manipulation. These changes may be related, directly or indirectly, or completely independent.     

Lectin-labeled membrane is transferred to the Golgi complex in mouse pituitary cells in vivo

Labeling of the Golgi complex with the lectin conjugate wheat germ agglutinin-horseradish peroxidase (WGA-HRP), which binds to cell surface membrane and enters cells by adsorptive endocytosis, was analyzed in secretory cells of the anterior, intermediate, and posterior lobes of mouse pituitary gland in vivo. WGA-HRP was administered intravenously or by ventriculo-cisternal perfusion to control and salt-stressed mice; post-injection survival times were 30 min-24 hr. Peroxidase reaction product was identified within the extracellular clefts of anterior and posterior pituitary lobes through 24 hr but was absent in intermediate lobe. Endocytic vesicles, spherical endosomes, tubules, dense and multivesicular bodies, the trans-most saccule of the Golgi complex, and dense-core secretory granules attached or unattached to the trans Golgi saccule were peroxidase-positive in the different types of anterior pituitary cells and in perikarya of supraoptico-neurohypophyseal neurons; endoplasmic reticulum and the cis and intermediate Golgi saccules in the same cell types were consistently devoid of peroxidase reaction product. Dense-core secretory granules derived from cis and intermediate Golgi saccules in salt-stressed supraoptic perikarya likewise failed to exhibit peroxidase reaction product. The results suggest that in secretory cells of anterior and posterior pituitary lobes, WGA-HRP, initially internalized with cell surface membrane, is eventually conveyed to the trans-most Golgi saccule, in which the lectin conjugate and associated membrane are packaged in dense-core secretory granules for export and potential exocytosis of the tracer. Endoplasmic reticulum and the cis and intermediate Golgi saccules appear not to be involved in the endocytic/exocytic pathways of pituitary cells exposed to WGA-HRP.     

Morphological aspects of Culex quinquefasciatus salivary glands

The salivary glands of Culex quinquefasciatus female mosquitoes are paired organs composed of two lateral lobes with proximal and distal secretory portions, and a medial lobe. All portions comprise a simple epithelium that surrounds a salivary duct. In the apical portion of the medial lobe, non-secretory cells strongly resemble cells involved in ion and water transport. The general architecture of the secretory portions is similar between lobes. The appearance of the secretory material and the morphological aspect of the apical cell membrane are the most distinctive features among the three secretory portions. Cells in the lateral proximal lobe display thin membrane projections extending into a translucent and finely filamentous secretory product. At the lateral distal portion, the apical cell membrane forms an intricate meshwork that encloses a dark secretory product. Medial lobe secretory cells also contain secretory cavities surrounded by intracytoplasmic vesicles, all containing a very dark and uniform product. Scattered cells holding numerous vacuoles, some of them containing a small and electron-dense granule eccentrically located and resembling those of the diffuse endocrine system, are frequently observed in the periphery of all secretory portions. Immunofluorescence assays revealed that the distal portion of the lateral lobes contains apyrase, an enzyme putatively responsible for platelet aggregation inhibition, diffusely distributed in the cell cytoplasm.     

Actin filament disruption blocks cerebellar granule neurons at the unipolar stage of differentiation in vitro

Cerebellar granule neurons developing in vitro initially extend a single axon, with the Golgi apparatus and centrosome positioned at the base of this axon and then begin the transition to a bipolar morphology by rotating the Golgi-centrosome to the opposite pole of the cell and extending a secondary axon; granule cells reach a mature, complex morphology by extending multiple, short dendrites by 5-6 days in vitro. (Zmuda and Rivas, 1998. Cell Motil Cytoskel 41:18-38). To test the effects of actin depolymerization on this characteristic pattern of granule cell axonogenesis, cultured granule cells were treated with either cytochalasin D (CD) or latrunculin A (Lat A) to depolymerize filamentous actin. Although actin depolymerization did not inhibit initial axon extension, it prevented the cells from proceeding on to the transitional, bipolar, or complex stages of differentiation, effectively blocking the cells at the unipolar stage of differentiation. Although the Golgi apparatus resided at the base of the axon in nontreated unipolar cells, or at the opposite pole of the cell body in nontreated transitional cells, the Golgi was randomly localized within the cytoplasm of cells that had been treated with either CD or Lat A. These results show that the transition from the unipolar to the bipolar stage and on to more mature stages of granule cell differentiation is dependent on an intact actin cytoskeleton and suggest that the characteristic pattern of granule cell differentiation may be dependent on the repositioning of the Golgi-centrosome during morphological development.     

The relative thickness of intracellular membranes in epithelial cells of the ventral lobe of the rat prostate

Synopsis The relative thickness of intracellular membranes of epithelial cells in the ventral lobe of the rat prostrate was measured by a densitometric method. Glutaraldehyde perfusion followed by ruthenium tetroxide immersion fixation appeared to be the most suitable method for membrane thickness measurements. By thickness, the membranes could be roughly subdivided into three groups. The inner and outer membranes of the mitochondrion made up the thinnest membranes of the cell. The second group of membranes consisted of the membranes of the rough-surfaced endoplasmic reticulum and the Golgi apparatus, the different faces of the latter organelle, and the Golgi vesicles. The thickest group of membranes included those of the cell membrane, secretory granules, condensing vacuoles, lysosomes, autophagic vacuoles and multivesicular bodies. The differences in thickness of the membranes are probably due to the varying protein/lipid ratio, and the qualities and proportions of the different lipids in the membranes.     

The function of the golgi complex in transitional epithelium. Synthesis of the thick cell membrane

The superficial squamous cells of rat transitional epithelium are limited, on their luminal face, by an asymmetrically thickened membrane. Patches of similar thick membrane are found in the walls of the Golgi cisternae and it is suggested that the Golgi system is the site of assembly of the thick plasma membrane. This implies membrane flow from the Golgi apparatus to the cell surface, and there is indirect evidence that the membrane is transported in the form of fusiform vacuoles, derived from the Golgi cisternae, which fuse with, and become part of, the free cell membrane. Uptake of injected Imferon shows that similar, large, thick-walled vacuoles may be formed by invagination of the free cell surface. Some of these vacuoles are subsequently transformed into multivesicular bodies and autophagic vacuoles. The formation of other large heterogeneous bodies is described, and some of these are shown to have acid phosphatase activity.     

Endocytotic pathways in the melanotroph of the rat pituitary

Summary The internalization of the extracellular markers horseradish peroxidase (HRP) and cationized ferritin (CF) by the melanotrophs of the intermediate lobe of the rat pituitary was studied during short-time incubation of mechanically dissociated cells or in cell culture after 5 days. After a 30 min exposure, the tracers were found in electron-lucent granules or vacuoles of approximately the same size as the secretory granules, situated 200–500 nm from the cell membrane. In the cultured cells, which showed a higher rate of tracer uptake, internalization was followed for 1, 2 and 5 min after labelling and during 2 h of exposure. Initially, the label was seen only in coated pits and coated vesicles at the cell membrane. Larger vacuoles were first seen after 2–5 min of incubation. After 2 h of exposure the labelling pattern was distinctly different for the two tracers. CF was found in larger vacuoles of varying morphology, in dilatations at the base of cilia, within Golgi saccules and at the edge of the electron-dense core of forming secretory granules. HRP was found in an extensive array of tubulovesicular structures extending throughout the cytoplasm. The Golgi complex and forming granules were, however, not labelled with HRP. The study identifies part of the electron-lucent granules or vacuoles in the melanotroph as endosomes, and shows that the melanotrophs sort CF and HRP via diverting pathways after internalization, suggesting that granule membrane, and possibly its functional components, can be recycled in these cells.     

高原鼠兔松果体超微结构的研究

本文采用光镜和透射电镜对高原鼠兔松果体的形态结构进行了观察,并对其结构与功能的关系怍了初步探讨：1． 高原鼠兔的松果体与其他哺乳动物的基本相似, 包括深、浅两部分, 两部分的细胞构筑及其形态基本一致,主要由松果体细胞、胶质细胞、神经细胞、微细血管和神经纤维组成。松果体细胞有明、暗两种,两种细胞胞质内均有丰富的线粒体、高尔基复合体、粗面和滑面内质网,以及游离核糖体,还可见极少数微管和脂滴等。2． 松果体细胞内囊泡、微管和突触带的数量与细胞的分泌功能密切相关。3． 松果体分泌物主要通过二种方式释放：(1)通过扩散和胞吐作用,将分泌物释放到细胞外或血管周隙;(2)分泌物直接进入第三脑室。     

Structure of the ovotestis and evidence for heterosynthetic incorporation of yolk precursors in the oocytes of the nudibranch mollusc,Spurilla neapolitana

The ovotestis of Spurilla neapolitana consists of a series of spherical lobes, each of which is composed of radially arranged, sac-like acini or follicles. The male and female portions of each acinus are separated by ovarian follicle cells and testicular accessory cells. A thick basal lamina serves as a barrier between adjacent acini. The surface of each ovotestis lobe is covered by several layers of myoepithelial cells resting on a connective tissue layer. Developing oocytes are intimately associated with follicle cells except in the last stages of vitellogenesis. Follicle cells are characterized by the presence of extensive arrays of rough endoplasmic reticulum (RER) and Golgi complexes and may play a role in vitellogenesis. An ultrastructural analysis of vitellogenesis suggests that oocytes utilize both auto- and heterosynthetic mechanisms of yolk formation. Autosynthetsis is suggested by the activity of the Golgi complex and RER, while heterosynthesis is indicated by high levels of endocytotic activity by the oocyte. Follicle cell development and high endocytotic activity in the oocytes may be a reproductive adaptation to accelerate yolk synthesis, resulting in more rapid egg production.     

Ultrastructural and cytochemical studies of acid phosphatase and trimetaphosphatase in rat peritoneal mast cells developing in vivo

Summary The ultrastructural and cytochemical features of peritoneal mast cells of the rat were studied. Immature mast cells show specific cytoplasmic granules of different sizes, the smaller ones localized in the Golgi region. The rough endoplasmic reticulum and Golgi apparatus are well developed, and mitochondria are numerous. Nuclei show deep indentations. Acid phosphatase is present in the Golgi saccules, in GERL (Golgi apparatus-endoplasmic reticulumlysosome) and in some small granules. It is not present in mature granules. Trimetaphosphatase is present in the Golgi saccules, in GERL, in most immature granules and in some mature granules. These enzymes appear to be transported and packaged into granules by the Golgi apparatus, suggesting that the specific mast cell granules may be a form of lysosome. The results of this study are consistent with the hypothesis that peritoneal mast cells may be derived from macrophage-like precursors.     

Golgi apparatus cisternae of monensin-treated cells accumulate in the cytoplasm of liver slices

Protein transport via the endoplasmic reticulum Golgi apparatus-cell surface export route was blocked when slices (6-15 cells thick) of livers of 10-day-old rats were incubated with 1 microM monensin. Production of secretory vesicles by Golgi apparatus was reduced or eliminated and, in their place, swollen cisternae accumulated in the cytoplasm at the trans Golgi apparatus face. The swelling response was restricted to the six external cell layers of the liver slices, and the number of cells showing the response was little increased by either a greater concentration of monensin or by longer times of incubation. When monensin was added post-chase to the slices, flux of radioactive proteins to the cell surface was inhibited by about 80% as determined from standard pulse-chase analyses with isolated cell fractions. Radioactive proteins accumulated in both endoplasmic reticulum and Golgi apparatus and in a fraction that may contain monensin-blocked Golgi apparatus cisternae released from the stack. The latter fraction was characterized by galactosyltransferase/thiamine pyrophosphatase ratios similar to those of Golgi apparatus from control slices. The use of monensin with the tissue slice system may provide an opportunity for the cells to accumulate monensin-blocked Golgi apparatus cisternae in sufficient quantities to permit their isolation and purification by conventional cell fractionation methods.     

The optic lobe of Drosophila melanogaster. I. A Golgi analysis of wild-type structure

Summary Golgi studies of the neurons in the optic lobes of Drosophila melanogaster reveal a large number of neuronal cell types. These can be classified as either columnar or tangential. Columnar elements establish the retinotopic maps of the lamina, medulla, and lobula-complex neuropiles. They are classified according to the position of their cell bodies, the number, width, and level of their arborizations, and their projection areas. Tangential elements are oriented perpendicularly to the columns. The arborizations of different tangential neurons are restricted to different layers of the optic neuropiles, within such layers their dendritic fields may span the entire retinotopic field or only part of it. The abundance of cell types inside each of the columnar units of the optic lobe is discussed with regard to its possible functional significance. By means of their stratified arborizations the columnar neurons form what appear to be multiple sets of retinotopically organized parallel information processing networks. It is suggested that these parallel networks filter different kinds of visual information and thus represent structurally separated functional subunits of the optic lobe. Such a parallel organization of visual functions increases the sites for function-specific gene actions and may explain the behavioral phenotypes of recently isolated structural mutants of the optic lobe.     

The Endoplasmic Reticulum-Resident Chaperone Heat Shock Protein 47 Protects the Golgi Apparatus from the Effects of O-Glycosylation Inhibition

The Golgi apparatus is important for the transport of secretory cargo. Glycosylation is a major post-translational event. Recognition of O-glycans on proteins is necessary for glycoprotein trafficking. In this study, specific inhibition of O-glycosylation (Golgi stress) induced the expression of endoplasmic reticulum (ER)-resident heat shock protein (HSP) 47 in NIH3T3 cells, although cell death was not induced by Golgi stress alone. When HSP47 expression was downregulated by siRNA, inhibition of O-glycosylation caused cell death. Three days after the induction of Golgi stress, the Golgi apparatus was disassembled, many vacuoles appeared near the Golgi apparatus and extended into the cytoplasm, the nuclei had split, and cell death assay-positive cells appeared. Six hours after the induction of Golgi stress, HSP47-knockdown cells exhibited increased cleavage of Golgi-resident caspase-2. Furthermore, activation of mitochondrial caspase-9 and ER-resident unfolded protein response (UPR)-related molecules and efflux of cytochrome c from the mitochondria to the cytoplasm was observed in HSP47-knockdown cells 24 h after the induction of Golgi stress. These findings indicate that (i) the ER-resident chaperon HSP47 protected cells from Golgi stress, and (ii) Golgi stress-induced cell death caused by the inhibition of HSP47 expression resulted from caspase-2 activation in the Golgi apparatus, extending to the ER and mitochondria.     

Cellular distribution of beta-endorphin-like substance in the rat pituitary and brain.

β-endorphin was localized in the cytoplasm of most cells of the intermediate lobe and discrete cells of the anterior lobe of the rat pituitary. The cells of the posterior lobe were negative. Various regions of the rat brain including some ependymal cells of the third ventricle and discrete cells of the choroid plexus also displayed a granular reaction product. The distribution of the granules in the neurons appeared over the cell bodies whereas other positive cells displayed an intense reaction product in the cytoplasm.     

Golgi Tubule Traffic and the Effects of Brefeldin A Visualized in Living Cells

The Golgi complex is a dynamic organelle engaged in both secretory and retrograde membrane traffic. Here, we use green fluorescent protein–Golgi protein chimeras to study Golgi morphology in vivo. In untreated cells, membrane tubules were a ubiquitous, prominent feature of the Golgi complex, serving both to interconnect adjacent Golgi elements and to carry membrane outward along microtubules after detaching from stable Golgi structures. Brefeldin A treatment, which reversibly disassembles the Golgi complex, accentuated tubule formation without tubule detachment. A tubule network extending throughout the cytoplasm was quickly generated and persisted for 5–10 min until rapidly emptying Golgi contents into the ER within 15–30 s. Both lipid and protein emptied from the Golgi at similar rapid rates, leaving no Golgi structure behind, indicating that Golgi membranes do not simply mix but are absorbed into the ER in BFA-treated cells. The directionality of redistribution implied Golgi membranes are at a higher free energy state than ER membranes. Analysis of its kinetics suggested a mechanism that is analogous to wetting or adsorptive phenomena in which a tension-driven membrane flow supplements diffusive transfer of Golgi membrane into the ER. Such nonselective, flow-assisted transport of Golgi membranes into ER suggests that mechanisms that regulate retrograde tubule formation and detachment from the Golgi complex are integral to the existence and maintenance of this organelle.     

Distinct lobes of Limulus ventral photoreceptors. II. Structure and ultrastructure

The structure of Limulus ventral photoreceptors fixed in situ has been investigated using light and electron microscopy and computer-assisted reconstruction and planimetry. Photoreceptors occur singly and in clusters. All photoreceptors have two types of lobes. The rhabdomeral lobe (R lobe) appears to be specialized for light sensitivity, containing the rhabdomere, which completely covers its external surface and forms infoldings into the lobe. The structure of the external rhabdom differs from that within infoldings. The other main structures of the R lobe are the palisades along the rhabdom, multivesicular bodies, lamellar bodies, and mitochondria. The arhabdomeral lobe (A lobe) bears the axon and contains the nucleus, clusters of residual bodies, lamellar arrays of endoplasmic reticulum, masses of glycogen, lipid droplets, and Golgi complexes. The R lobe and A lobe are analogous to the outer and inner segments of vertebrae photoreceptors. In single photoreceptors A and R lobes are separated by an indentation filled with glial processes. Computer reconstructions of cell clusters reveal that each cell has both types of lobes and an axon. Most of the rhabdom is formed from abutting arrays of external rhabdom from the R lobes of different members of the cluster. Efferent fibers containing characteristic angular granules penetrate single cells and clusters in glial invaginations. The main, if not exclusive, target of the efferent fibers is the internal rhabdom.