The beads in the Golgi complex-endoplasmic reticulum region

Fine structural aspects on the web glue production in the golden orb-web spider Trichonephila clavata

The water-soluble glue substance of the capture threads in Trichonephila clavata is solely produced from two pairs of aggregate silk glands. During the web glue production, secretory vesicles were synthesized via the extensive rough endoplasmic reticulum of epithelial cells. Unlike the clearly described fibrous web production in spiders, the process of aqueous web glue production appears to involve either a condensing or a packaging step by the Golgi complex. In particular, the fine structure of secretory vesicles varies from cell to cell and may represent the secretory cycle. The electron-dense multivesicular bodies were clearly visible as discrete droplets, and the mature secretory product in the glandular epithelium appeared as a spherical vacuole grown by fusion with surrounding small vesicles. Our fine structural observation reveals that the secretion occurs when the release of secreted material involves the loss of part of the cytoplasm. The bleb along the luminal surface of the secretory cells and membrane-bound extracellular vesicles which pinched off from the cell suggests that the secretory product is released by the mechanism of apocrine secretion.

In Situ Detection of Neurotransmitters from Stem Cell-Derived Neural Interface at the Single-Cell Level via Graphene-Hybrid SERS Nanobiosensing

In situ quantitative measurements of neurotransmitter activities can provide useful insights into the underlying mechanisms of stem cell differentiation, the formation of neuronal networks, and neurodegenerative diseases. Currently, neurotransmitter detection methods suffer from poor spatial resolution, nonspecific detection, and a lack of in situ analysis. To address this challenge, herein, we first developed a graphene oxide (GO)-hybrid nanosurface-enhanced Raman scattering (SERS) array to detect dopamine (DA) in a selective and sensitive manner. Using the GO-hybrid nano-SERS array, we successfully measured a wide range of DA concentrations (10^-4 to 10^-9 M) rapidly and reliably. Moreover, the measurement of DA from differentiating neural stem cells applies to the characterization of neuronal differentiation. Given the challenges of in situ detection of neurotransmitters at the single-cell level, our developed SERS-based detection method can represent a unique tool for investigating single-cell signaling pathways associated with DA, or other neurotransmitters, and their roles in neurological processes.

Surface membranes, Golgi complexes, and vacuolar systems

In the absence of fossils, the cells of vertebrates are often described in lieu of a general animal eukaryote model, neglecting work on insects. However, a common ancestor is nearly a billion years in the past, making some vertebrate generalizations inappropriate for insects. For example, insect cells are adept at the cell remodeling needed for molting and metamorphosis, they have plasma membrane reticular systems and vacuolar ferritin, and their Golgi complexes continue to work during mitosis. This review stresses the ways that insect cells differ from those of vertebrates, summarizing the structure of surface membranes and vacuolar systems, especially of the epidermis and fat body, as a prerequisite for the molecular studies needed to understand cell function. The objective is to provide a structural base from which molecular biology can emerge from biochemical description into a useful analysis of function.

Rapid and transient phosphorylation of nuclear matrix proteins upon interferon-alpha treatment in Daudi lymphoma cells

Evidence for a rapid and transient hyperphosphorylation of a 45 kD protein in isolated nuclei from interferon-alpha-treated Daudi lymphoma cells is presented. Extraction of nuclear matrices from these nuclei has provided further evidence for the association of such a protein in the nuclear matrix structure. Because phosphorylation assays performed directly on nuclear matrices from interferon-treated cells have revealed rapid and transient increase of gamma 32P-ATP incorporation into this 45 kD band, an early involvement of the nuclear matrix in the response of the nucleus to the interferon antiproliferative message is suggested.

Golgi complex beads and the transition region

Secretory proteins and membranes move in transfer vesicles from the rough endoplasmic reticulum through the transition region to the outer saccule of the Golgi complex. In both arthropod and vertebrate cells, the GC beads are a characteristic structural component of the transitional region. The beads are particles about half the size of ribosomes arranged equidistantly from one another and the smooth face of the ER. In an active GC, the beads are in rings through which the ER membrane emerges to form transfer vesicles. The beads may be part of the energy-dependent step required for the movement of proteins along eht secretory pathway, since they lose their ring arrangement under conditions that lower cellular ATP. The beads are organizers for Golgi complexes in the sense that they are the first recognizable components of new GCs as they arise from ER. Arthropod GC beads, but not those of vertebrates, can be visualized through their reaction with bismuth in vivo and in fixed tissue. Useful paradigms for traffic between the ER and the GC need to combine structural and biochemical information. Insect fat body, with its readily resolvable bismuth-strained beads and easily fractionated cell components may have particular value for this problem.

Effects of tunicamycin and monensin on the distribution of highly phosphorylated proteins in cells infected with herpes simplex virus type 1

New aspects of the distribution of highly phosphorylated proteins in cells infected with herpes simplex virus type 1 (HSV-1) were investigated at the ultrastructural level by the use of drugs which inhibit the glycosylation of viral proteins. The highly phosphorylated proteins were localized by the bismuth tartrate procedure applied on sections of glutaraldehyde-fixed cells embedded in Lowicryl. The drugs employed were tunicamycin, which alters the glycosylation activity of the rough endoplasmic reticulum (RER), and monensin, which blocks the migration of vesicles of the Golgi apparatus (GA) thereby impairing the glycosylation function of the GA. Tunicamycin induced proliferation of RER and the accumulation of highly phosphorylated proteins on its membranes and also impaired GA vesicle maturation and inhibited the usual accumulation of phosphorylated proteins within them. Monensin induced proliferation of the nuclear envelope, including both outer and inner membranes, with bismuth bound to staggered segments of the latter, and also affected the GA in that bismuth-binding proteins were accumulated on the external surface of the swollen vesicles instead of the lumen. These data suggest that an injury of one membrane system, RER or GA, engenders consequential effects on the other. This also supports evidence for an interrelationship between post-translational glycosylation and phosphorylation of proteins in HSV infection.

The charge distribution in the rough endoplasmic reticulum/Golgi complex transitional area investigated by microinjection of charged tracers

The distribution of microinjected ferritin, ranging in charge from anionic to highly cationic, has been used to indicate differences in surface charge on the rough endoplasmic reticulum and the Golgi complex of intact cells. Highly cationic ferritins (HCF)(HCF1, pI 7.9-9.1; HCF2, pI 8.5-9.4; and HCF3.pI 9.5-10.1) were mostly bound and caused swelling of the rough endoplasmic reticulum. Cationic ferritin (CF) (pI 7.0-8.0) and anionic ferritin (AF) (pI 4.0-4.4) caused no changes in morphology. The distribution of these ferritins in the cytoplasmic space varied with their charge. Significantly more CF was bound to surfaces than was found in the free cytoplasmic space. Conversely, there was significantly more AF in the free cytoplasmic space than close to surfaces. Therefore, the intracellular surfaces are negatively charged. Comparison of the structures in the secretory pathway showed no differences in ferritin binding to transition vesicles, rough endoplasmic reticulum, Golgi saccules or secretory vesicles. The Golgi complex beads are not distinguished by their charge. It is therefore unlikely that charge differences play a role in regulating membrane-membrane interactions in this region of the secretory pathway.

Golgi complex beads in vertebrates and their relationship with clathrin coats

Addition of tannic acid to the primary glutaraldehyde fixative and the viewing of thin sections by stereo electron microscopy greatly simplifies the detection of vertebrate cell Golgi complex beads which are otherwise difficult to see since they do not stain with bismuth. These results confirm the generality of conclusions from experiments on arthropod beads which are easily observed because of their bismuth affinity. In vertebrate and arthropod cells, bead rings encircle the base of forming transition vesicles below the growing portion of the vesicle that is covered with a clathrin coat. Their unique position at such a sharp functional and structural boundary in intercompartmental transport suggests that the bead rings may specify a select region of rough endoplasmic reticulum devoid of ribosomes where clathrin coats can induce transition vesicle formation and prevent intermixing of the elements of a returning transition vesicle.

Bismuth chemistry and the glutaraldehyde insensitive staining reaction

The free metal ion, Bi3+, is the only chemical species of bismuth that stains a strongly bismuth-reactive molecule, polyarginine, in vitro. The bismuth solution specifically requires tartrate as a chelating agent for the reaction to occur between pH 7.4 and 8.0. Since Bi3+ reacts strongly with polyarginine, creatine and ATP fixed to cellulose acetate strips and DEAE-cellulose and P-cellulose, the free metal ion (Bi3+) may bind to phosphate or guanidyl groups, or both, after glutaraldehyde fixation.

The arrangement of the Golgi complex beads is not controlled by the cytoskeleton

Exposure of insect fat body to treatments which disrupt microtubules (colchicine, vinblastine sulfate and cold treatment) blocks intracellular transport between the Golgi complex and the plasma membrane but does not affect Golgi complex bead rings or transport from rough endoplasmic reticulum to the Golgi complex. Drugs which disrupt microfilaments (cytochalasins B and D) do not affect the bead rings or intracellular transport of secretory proteins at any level. Thus, intracellular transport between the rough endoplasmic reticulum and the Golgi complex and the arrangement of the beads in rings are both independent of the cytoskeleton. The ring arrangement is presumably maintained by interconnection(s) with rough endoplasmic reticulum membrane.

The correlation between bismuth and uranyl staining and phosphorus content of intracellular structures as determined by electron spectroscopic imaging

Four groups of intracellular structures can be recognized according to bismuth and uranyl staining and phosphorus content. (1) Those which contain phosphorus and stain strongly with uranyl acetate but not with bismuth (ribosomes, heterochromatin and mature ribosomal precursor granules), presumably because of their nucleic acid content. (2) Those which contain phosphorus and stain with uranyl acetate and bismuth (interchromatin granules, immature ribosomal precursor granules and mitochondrial granules), presumably because at least some of their phosphate is available to react with bismuth. (3) Those which contain little phosphorus but which stain strongly with bismuth and weakly with uranyl acetate (Golgi complex beads), perhaps because some ligand in addition to phosphate reacts with bismuth, and (4) those which do not contain phosphorus and stain with neither uranyl acetate nor bismuth (portasomes). Uranyl staining correlates strongly with the phosphorus content of nucleic acids, proteins and inorganic deposits. Bismuth will stain some phosphorylated molecules but not all. Thus only some phosphates stain with bismuth.

High resolution microanalysis for phosphorus in Golgi complex beads of insect fat body tissue by electron spectroscopic imaging

Golgi complex beads are 10 nm particles arranged in rings on the smooth forming face of the Golgi complex that stain specifically with bismuth in arthropod cells. In vitro experiments with biological molecules spotted on to cellulose acetate strips indicated that bismuth bound to the beads through phosphate groups. We could detect a weak phosphorus signal from the beads using a new technique called electron spectroscopic imaging that is capable of very high spatial resolution (0.3-0.5 nm) and sensitivity (50 atoms of phosphorus). Detection was not obscured by tissue staining with bismuth or uranyl acetate of by using an inorganic buffer (Na cacodylate). Localization of phosphorus was greatly improved by using colour-enhanced computer pictures of the electron spectroscopic images and quantitating the images. The results indicate that the phosphorus content of the beads is large enough to account for their bismuth reactivity.

Bead rings at the endoplasmic reticulum-Golgi complex boundary: morphological changes accompanying inhibition of intracellular transport of secretory proteins in arthropod fat body tissue

Golgi complex beads are 10-nm particles arranged in rings on the smooth surface of rough endoplasmic reticulum (ER) makind the forming face of the Golgi complex (GC). In arthropod cells they stain specifically with bismuth. Their morphology has been studied after treatment with reagents known to interfere with GC function. Inhibitors of oxidative phosphorylation (antimycin A, cyanide, and anoxia), but not an inhibitor of glycolysis (iodoacetate), both cause the bead rings to collapse and the GC saccules to round up, and inhibit transition vesicle (TV) formation. Cycloheximide blocks protein synthesis on ribosomes but does not stop TV formation or disrupt bead rings, even after prolonged treatment (6 h) to allow emptying of the rough ER cisternae. Thus the collapse of bead rings is not attributable to inhibition of protein synthesis, and the ring structure of beads does not require continued protein synthesis and secretion for its maintenance. Valinomycin has effects on the GC similar to those of antimycin A, but A23187, monensin, and lasalocid do not affect bead ring structure or TV formation. These results are consistent with valinomycin's secondarily uncoupling mitochondria, which collapses bead rings and prevents TV formation. Thus inhibitors of oxidative phosphorylation do not influence the beads through cation movement. Because mononsin and lasalocid block secretion at the level of the condensing vacuoles, bead rings are not influenced by blocks in secretion distal to them or by the backup of secretory material. These experiments are consistent with inhibitors of oxidative phosphorylation collapsing bead rings by decreasing intracellular ATP. The concomitant block to TV formation and the collapse of bead rings suggests that integrity of the bead rings is essential for the transport of secretory material from the rough ER to the GC.

Methods in ultrastructural cytochemistry of the cell nucleus

The electron microscopical study of the cell nucleus as observed in thin sections requires the use of cytochemical methods because of the intricate pattern of the nuclear components. The in situ techniques based on electron staining and enzymatic digestion are reviewed, excluding autoradiography, cytoenzymology and immunocytochemistry. A tentative classification has been adopted according to the chemical nature of the revealed component. Thus, the staining procedures for the nucleoproteins in general, for both nucleic acids, for the proteins, and finally for the deoxyribonucleoproteins and DNA are considered separately. 1--Stains for the nucleoproteins include simple reagents such as the uranyl and lead salts which are largely used in electron microscopy but are of limited specificity. 2--A variety of methods, some of them specific, is available for the simultaneous visualization of DNA and RNA which is based on common properties: basophilia, ability to bind diaminoacridines, presence of hydroxyl groups. However, due to the recent development of specific and preferential methods for each nucleic acid, we feel that among the older methods, only rapid and simple procedures for the detection of both nucleic acids remain of interest. 3--Proteins being ubiquitous, the useful techniques must reveal subsets within the total nuclear proteins. Apart from some endogeneous enzymes, basic proteins -- practically histones -- so far represent the only group for the detection of which reliable methods exist. 4--Several techniques developed recently are available for the specific detection of DNA. In favourable cases, methods derived from the Feulgen reaction allow its visualization at a molecular level. In addition, standard procedures for the preparation of mammalian cells and tissues are described. Each staining method is at least briefly discussed, but emphasis has been placed on a small number of techniques described in detail. They comprise the EDTA regressive stain for the ribonucleoproteins, several reactions of the basic proteins and the Feulgen-like osmium ammine reaction for DNA.

Nucleoprotein localization by bismuth staining

Experiments on isolated mouse liver muclei involving enzyme digestion, the crosslinking of amino groups and alkaline hydrolysis demonstrate that bismuth binds to nucleoproteins through amino and phosphate groups. Analysis of the nucleoproteins extracted with salt and acid solutions in conjunction with bismuth staining after these treatments suggests that: (1) a bismuth amino group interaction occurs on ribonucleo-protein particles, histones and perhaps some non-histone chromosomal proteins, and (2) bismuth phosphate binding is specific for one, or all, of three distinct species of non-histone proteins. These results suggest that histones not tightly bound to DNA through their amino groups are present on interchromatin granules, the presumed transcriptionally active regions of chromatin. Phosphorylated non-histone proteins are also localized at these sites. Staining with heavy metals such as bismuth may be the best method for high resolution localization of nucleoproteins involved with regulating gene activity and maintaining chromatin structure.

Granule release by polymorphonuclear leukocytes treated with the ionophore A23187

Polymorphonuclear leukocytes (PMN's) incubate three to eight minutes at 37 degrees C in medium containing 1 X 10(-6) M of the ionophore antibiotic A23187 released their cytoplasmic granules into the extracellular medium. Transmission electron microscopy of treated cells showed microfilament bundles extending between adjacent granules within the cytoplasm and between granules and the plasma membrane. Tiny dense projections (beads) 8-12 nm in diameter were observed along segments of the cytoplasmic surface of the plasma membrane with a periodicity of 20-30 nm. These beads were observed on the plasma membrane only in the vicinity of intra- or extracytoplasmic granules. The structural relationships of the beads with the plasma membrane microfilaments suggest they play a role in the process of ionophore-induced granule release from polymorphonuclear leukocytes.

Vertebrate Golgi complexes have beads in a similar position to those found in arthropods

Insects and other arthropods have bead-like structures in Golgi complexes from all cell types. They are arranged in rings at the base of transition vesicles located near the smooth surface of the rough endoplasmic reticulum making the forming face of the Golgi complex and are only seen easily after staining in bismuth salts. Procedures used to demonstrate the beads in arthropod Golgi complexes do not selectively stain any structures where they would be expected to occur in several mouse and tadpole tissues. However, a faint pattern similar to the arthropod GC beads can be made out in the large GCs concerned in the formation of acrosomes during mouse spermatogenesis. Uranyl staining shows particles of about the same size and spacing as the beads of arthropod GCs. We conclude that vertebrate GCs may have beads that differ from arthropods in their staining properties.