Influence of colchicine and vinblastine on the golgi complex and matrix deposition in chondrocyte aggregates. An ultrastructural study

Dental and craniofacial alterations in long-term survivors of childhood head and neck rhabdomyosarcoma

OBJECTIVE

Rhabdomyosarcoma (RMS) represents the most common soft tissue sarcoma that affects children. Treatment involves chemoradiotherapy. This study aimed at evaluating the long-term alterations to teeth and cranial bones in children, teenagers, and young adults after oncologic treatment.

STUDY DESIGN

We conducted a cross-sectional study of patients undergoing treatment for head and neck RMS between 1988 and 2011. We evaluated demographic, clinical, and treatment data and performed panoramic radiography, cephalometry, and photography.

RESULTS

We evaluated 27 long-term survivors, most of whom had been treated between ages 0 to 5 years (51.9%). The total radiation dose applied was 50.4 Gy, and the chemotherapy combination included vincristine, actinomycin D, and cyclophosphamide in 51.9% of the cases. We observed 603 dental alterations, among which 377 (62.7%) occurred in patients ages 0 to 5 years, and root shortening was the most frequent alteration observed (24.2%). With regard to facial bones, 74% of the patients had some level of facial asymmetry, 70.4% had reduced facial depth, 48.4% had mandibles of short size, and 77.8% had reduced facial height.

CONCLUSIONS

Children submitted to RMS treatment involving chemotherapy and radiotherapy displayed significant dental and craniofacial alterations, especially when treatment occurred between ages 0 and 5 years.

Effects of Cytotoxic Chemotherapy on Dental Development

A histological study of 21 teeth from 9 patients who had received cytotoxic chemotherapy for malignant disease showed increased prominence of incremental lines in the dentine. The number and distribution of these lines corresponded to periods of intravenous therapy and vincristine appeared to be the most likely cause. This effect was probably due to temporary disturbance of microtubular function in the odontoblasts resulting in decreased secretion of collagenous dentine matrix. Calcification appeared to be unaffected.

A systematic review of dental late effects in survivors of childhood cancer

Survivors of childhood cancer are at risk for dental late effects. This systematic review summarizes associations between treatment exposures and dental late effects among survivors of childhood cancer. We included investigations with at least 20 study participants conducted for 2 or more years after completion of childhood, adolescent, or young adult cancer therapy. This review suggests both independent and additive effects of radiotherapy and chemotherapy on dental complications, and identifies vulnerable groups with specific host and treatment characteristics. This summary provides information that will assist clinicians to prevent, detect, and facilitate early intervention for dental late effects.

Cell polarity as a regulator of cancer cell behavior plasticity

Cell polarization is an evolutionarily conserved process that facilitates asymmetric distribution of organelles and proteins and that is modified dynamically during physiological processes such as cell division, migration, and morphogenesis. The plasticity with which cells change their behavior and phenotype in response to cell intrinsic and extrinsic cues is an essential feature of normal physiology. In disease states such as cancer, cells lose their ability to behave normally in response to physiological cues. A molecular understanding of mechanisms that alter the behavior of cancer cells is limited. Cell polarity proteins are a recognized class of molecules that can receive and interpret both intrinsic and extrinsic signals to modulate cell behavior. In this review, we discuss how cell polarity proteins regulate a diverse array of biological processes and how they can contribute to alterations in the behavior of cancer cells.

Primary cilia mediate mechanotransduction through control of ATP-induced Ca2+ signaling in compressed chondrocytes

We investigated the role of the chondrocyte primary cilium in mechanotransduction events related to cartilage extracellular matrix synthesis. We generated conditionally immortalized wild-type (WT) and IFT88(orpk) (ORPK) mutant chondrocytes that lack primary cilia and assessed intracellular Ca(2+) signaling, extracellular matrix synthesis, and ATP release in response to physiologically relevant compressive strains in a 3-dimensional chondrocyte culture system. All conditions were compared to unloaded controls. We found that cilia were required for compression-induced Ca(2+) signaling mediated by ATP release, and an associated up-regulation of aggrecan mRNA and sulfated glycosaminosglycan secretion. However, chondrocyte cilia were not the initial mechanoreceptors, since both WT and ORPK cells showed mechanically induced ATP release. Rather, we found that primary cilia were required for downstream ATP reception, since ORPK cells did not elicit a Ca(2+) response to exogenous ATP even though WT and ORPK cells express similar levels of purine receptors. We suggest that purinergic Ca(2+) signaling may be regulated by polycystin-1, since ORPK cells only expressed the C-terminal tail. This is the first study to demonstrate that primary cilia are essential organelles for cartilage mechanotransduction, as well as identifying a novel role for primary cilia not previously reported in any other cell type, namely cilia-mediated control of ATP reception.

Involvement of the cytoskeletal elements in articular cartilage homeostasis and pathology

The cytoskeleton of all cells is a three-dimensional network comprising actin microfilaments, tubulin microtubules and intermediate filaments. Studies in many cell types have indicated roles for these cytoskeletal proteins in many diverse cellular processes including alteration of cell shape, movement of organelles, migration, endocytosis, secretion, cell division and extracellular matrix assembly. The cytoskeletal networks are highly organized in structure enabling them to fulfil their biological functions. This review will primarily focus on the organization and function of the three major cytoskeletal networks in articular cartilage chondrocytes. Articular cartilage is a major load-bearing tissue of the synovial joint; it is well known that the cytoskeleton acts as a physical interface between the chondrocytes and the extracellular matrix in 'sensing' mechanical stimuli. The effect of mechanical load on cytoskeletal element expression and organization will also be reviewed. Abnormal mechanical load is widely believed to be a risk factor for the development of osteoarthritis. Several studies have intimated that the major cytoskeletal networks are disorganized or often absent in osteoarthritic cartilage chondrocytes. The implications and possible reasoning for this are more widely discussed and placed into context with their potential relevance to disease and therapeutic strategies.

Modifications of Golgi complex in chondrocytes from osteoarthrotic (OA) rat cartilage

The status of the Golgi complex in normal vs osteoarthrotic (OA) cartilage has not yet been studied. A monoclonal antibody, MAb 58-K-9, allowed scoring of Golgi labeling intensity. In addition, ultrastructural assessment enabled us to focus on the distribution and relation between the endoplasmic reticulum (ER) and Golgi membranes. The study was performed in both normal and partially menisectomized OA-induced rat cartilage 20 and 45 days after surgery. Comparing Golgi immunolabeling intensities (mean +/- SEM) revealed a highly significant difference between normal (9.98 +/- 1.25), 20-day (2.49 +/- 0.34), and 45-day (0.82 +/- 0.22) cartilage. Moreover, chondrocytes from normal cartilage displayed 71.18% of labeling intensity in contrast to OA cartilage, in which chondrocyte labeling intensities were 24.95% (20 days) and 8.11% (45 days). OA chondrocytes appeared to display an overall reduction in Golgi labeling intensity, suggesting disruption of this organelle as the OA damage progressed. Interestingly, many 20-day OA-induced chondrocytes exhibited bubble-like Golgi immunolabeling compartmentalizing the cytoplasm, concomitant with putative apoptotic nuclear changes. At the same time, OA chondrocytes with a typical ultrastructural apoptotic pattern revealed a prominent ER gathered together with Golgi vesicles and saccules, also appearing to compartmentalize chondrocyte cytoplasm. We speculate about the role of Golgi modifications and apoptosis in OA pathogenesis.

Microtubules are potential regulators of growth-plate chondrocyte differentiation and hypertrophy

Terminal differentiation of growth-plate chondrocytes is accompanied by the acquisition of a spherical morphology and a large increase in cell volume. These changes are likely to be associated with rearrangement of the cytoskeleton, but little information on this aspect of chondrocyte hypertrophy is available. We report a role for microtubules in the control of chondrocyte maturation and hypertrophy. Chick growth-plate chondrocytes were fractionated into five maturationally distinct populations by Percoll density gradient centrifugation, and agarose gel differential display analysis was performed. We identified a 1200 bp cDNA fragment derived from a transcript that was most highly expressed in the hypertrophic chondrocytes. After cloning and sequencing, FASTA and BLAST analysis revealed 100% identity to chick beta7-tubulin. Differential expression was confirmed in a reverse transcription-polymerase chain reaction (RT-PCR) assay using specific primers for a 343 bp fragment from the 3' untranslated region of beta7-tubulin. Beta7-tubulin was upregulated three-fold in fully hypertrophic chondrocytes compared with the other four fractions, which all had similar levels of expression. Immunocytochemical localization of beta-tubulin in chick growth-plate sections demonstrated little staining in the chondrocytes of the proliferating zone, but intense cytoplasmic staining was present in the large hypertrophic chondrocytes. In cell culture studies, the addition of colchicine (10(-6) mol/L) resulted in a higher rate of [3H]-thymidine uptake (36.0%; p < 0.001), but lower amounts of alkaline phosphatase activity (69.1%; p < 0.001), collagen (49.1%; p < 0.01), and glycosaminoglycan (43.3%; p < 0.01) accumulation within the cell-matrix layer. Further evidence for the involvement of microtubules in chondrocyte differentiation and hypertrophy was obtained by morphological assessment of colchicine-treated growth-plate explant cultures. A partial failure of chondrocyte hypertrophy was observed, although collagen type X immunoreactivity was noted within the interstitial matrix. Further studies are required to identify the exact role of microtubules in chondrocyte hypertrophy, but the results presented here suggest that upregulation of beta-tubulin may be required for increased microtubule synthesis during changes in cell size during the hypertrophic process. In addition, as cell-matrix interactions are required for chondrocyte maturation, microtubules may promote the differentiated phenotype as a result of their role in Golgi-mediated secretion of matrix proteins.

58K, a microtubule-binding Golgi protein, is a formiminotransferase cyclodeaminase

58K was previously identified as a rat liver protein that binds microtubules in vitro and is associated with the cytoplasmic surface of the Golgi apparatus in vivo (Bloom, G. S., and Brashear, T. A. (1989) J. Biol. Chem. 264, 16083-16092). We now report that 58K is a formiminotransferase cyclodeaminase (FTCD), a bifunctional enzyme that catalyzes two consecutive steps in the modification of tetrahydrofolate to 5,10-methenyl tetrahydrofolate. Comparative immunoblotting using several monoclonal antibodies made against 58K and a polyclonal antibody made against a chicken liver protein (p60) with similar properties (Hennig, D., Scales, S. J., Moreau, A., Murley, L. L., De Mey, J., and Kreis, T. E. (1998) J. Biol. Chem. 273, 19602-19611) demonstrated precise co-purification of protein recognized by all antibodies through multiple fractionation steps, including gel filtration and ion exchange chromatography, and sucrose gradient ultracentrifugation. Eight peptides derived from 58K showed high sequence identity to amino acid sequences predicted by full length cDNA for p60 and porcine liver FTCD. Furthermore, purified 58K was associated with formiminotransferase and cyclodeaminase activities. Based on these collective results, 58K was concluded to be a rat liver version of FTCD. Microtubules assembled from brain tubulin, but not from liver tubulin, were able to bind rat liver FTCD. Binding to brain microtubules is suspected to occur via polyglutamates that are added post-translationally to tubulin in brain, which was shown to contain very low levels of FTCD, but not to tubulin in liver, which was determined to be the richest tissue source, by far, of FTCD. The physiological significance of the microtubule binding activity of FTCD is thus called into question, but an association of FTCD with the Golgi apparatus has now been established.

Effects of vinca alkaloids on rat parotid and submandibular glands function in vivo

1. Vincristine (1 mg/kg) and vinblastine (2 mg/kg) were injected intraperitoneally into the rats, 24 hr before the experiments. 2. Animals were anesthetized with 50 mg/kg of sodium pentobarbital and saliva was collected from vincristine-treated, vinblastine-treated and control animals using 8 mg/kg of pilocarpine as secretagogue. 3. Parotid saliva was analyzed for protein, amylase and Ca2+ content, and submandibular saliva for flow rate, protein and Ca2+ concentration. 4. Saliva from two treated groups was significantly lower (P < 0.01) in flow rate, amylase and protein content than that of control group. Calcium level was significantly increased (P < 0.05) in treated animals. 5. It is concluded that the antisecretory effects of vinca alkaloids may be consistent with their actions on salivary cell microtubules.

Cytoskeleton of cartilage cells

The cytoskeleton of chondrocytes consists of microfilaments made of actin, microtubules made of tubulin, and intermediate filaments made of a variety of subunits. Actin filaments are not prominent in vivo but may form in vitro. In culture, changes in filament polymerisation are important in determining cell shape, initiating chondrogenesis, and maintaining the chondrogenic phenotype. Microtubules, besides their role in cell division, organise the distribution of organelles and are involved in secretory transport mechanisms in collagen and proteoglycan synthesis. A variety of intermediate filaments may be present, frequently forming large whorled aggregates. The filaments include vimentin, cytokeratins, and glial fibrillary acidic protein. These may occur at different depths in articular cartilage. Vimentin accumulates during development of some fibrocartilages with increased mechanical loading. Together with other elements of the cytoskeleton, intermediate filaments could form part of a mechanotransduction system by which cells respond to external forces and sense changes in their external environment.

The effect of vinblastine on the incorporation of [3H]-glycine into proteins of the periodontal ligament of impeded and unimpeded mouse incisors

The effect of vinblastine on the protein metabolism of the periodontal ligament of impeded and unimpeded mouse incisors was studied by [3H]-glycine labelling and radioautography. The silver-grain concentration was determined in areas adjacent to the tooth, areas adjacent to bone and, as an internal control, in the dentine matrix. From 1 to 12 h there was no difference between treated and control animals; thus the drug did not alter protein biosynthesis. Later, the silver-grain concentration was significantly higher in areas adjacent to both bone and tooth in vinblastine-treated animals, suggesting a longer half-life of the labelled proteins. No significant differences between normal or unimpeded erupting incisors of both groups were detected. Dentine matrix showed a possibly higher re-utilization of the labelled amino acid in vinblastine-treated animals. The amount of labelled protein removed by collagenase was similar in both groups, while the concentration of grains due to collagenase-resistant proteins was significantly higher in treated animals, particularly at 96 h after the injection of labelled glycine. The relation between the increased amount of non-collagenous proteins in the periodontal ligament and the decrease in the rate of eruption caused by vinblastine was not established. However, among these proteins, fibronectin and proteoglycans are thought to be important factors in tooth eruption.

An ultrastructural study of mitotic chondrocytes in the proliferative zone of the rat tibial growth plate

Mitotic chondrocytes containing fairly prominent cell organelles were observed in the proliferative zone of the rat tibial growth plate by electron microscopy. During the later stage of mitosis, the endoplasmic reticulum was mostly vacuolated, and the Golgi stacks were replaced by spherical and cylindrical vacuoles and small vesicles. The cytoplasmic division began at early telophase. However, the cytoplasmic cleavage furrow was so narrow that dividing chondrocytes looked as if they were partitioned by a slit. This is probably one reason for the appearance of the binuclear cells that are occasionally observed in the tibial growth plate.

Activation of microtubule-associated protein kinase by microtubule disruption in quiescent rat 3Y1 cells

Treatment of quiescent rat fibroblastic cells (3Y1) with colchicine, a microtubule-disrupting agent, which could induce the initiation of DNA synthesis [Y. Shinohara, E. Nishida, and H. Sakai (1989) Eur. J. Biochem. 183, 275-280], activated a serine/threonine-specific protein kinase activity in cell extracts that preferentially phosphorylated exogenous microtubule-associated protein 2 (MAP2). Vinblastine treatment also activated the kinase activity, and taxol pretreatment inhibited the colchicine-induced activation of this kinase activity. The detailed biochemical characterization indicated that this microtubule disruption-activated MAP2 kinase was very similar or identical to the mitogen-activated MAP kinase in the substrate specificity and chromatographic behaviors on phosphocellulose, DEAE-cellulose, gel filtration, and phenyl-Sepharose. Pretreatment of the cells with protein synthesis inhibitors did not prevent the MAP2 kinase activation by colchicine. Moreover, phosphatase treatment inactivated the colchicine-activated MAP2 kinase activity. These data suggest that microtubule disruption activates MAP kinase through phosphorylation.

Comparisons of Golgi structure and dynamics in plant and animal cells

The Golgi apparatus of both higher plant and animal cells sorts and packages macromolecules which are in transit to and from the cell surface and to the lysosome (vacuole). It is also the site of oligosaccharide and polysaccharide synthesis and modification. The underlying similarity of function of plant and animal Golgi is reflected in similar morphological features, such as cisternal stacking. There are, however, several fundamental differences between the Golgi of plant and animal cells, reflecting, in large part, the fact that the extracellular matrices and lysosomal systems differ between these kingdoms. These include 1) the form and replication of the Golgi during cell division; 2) the disposition of the Golgi in the interphase cell; 3) the nature of "anchoring" the Golgi in the cytoplasm; 4) the genesis, extent, and nature of membranes at the trans side of the stack; 5) targeting signals to the lysosome (vacuole); and 6) physiological regulation of secretion events (constitutive vs. regulated secretion). The degree of participation of the Golgi in endocytosis and membrane recycling is becoming clear for animal cells, but has yet to be explored in detail for plant cells.

Modulation of the endolymphatic sac function

A method for inducing a partial dysfunction of the endolymphatic sac and its effect was investigated. Acetazolamide as well as amiloride caused collapse of the lateral intercellular spaces in the endolymphatic sac epithelium and a subsequent mild endolymphatic hydrops. These changes indicate a decreased absorption rate of endolymph in the endolymphatic sac. Colchicine caused a disturbed secretory activity of the sac induced by glycerol. Animals treated with colchicine showed marked signs of inner ear malfunction after additional treatment with glycerol, which might indicate that the secretory activity in the sac is closely related to the regulation of inner ear fluid homeostasis and functional disturbance.

Influence of antimicrotubular drugs on the Golgi apparatus of stomach secretory mucoid cells and small intestine absorptive cells

The effects of vinblastine and colchicine on the Golgi apparatus of stomach surface mucoid and absorptive intestinal cells were compared by cytochemical analysis. The two epithelial cells were chosen because of their different specific functions in the formation of secretory granules, the production of lysosomes and the intensity of membrane traffic in the cytoplasm. For the analysis, adult mice were injected with 1 mg/100 g b.w. of vinblastine and 1 mg/100 g b.w. of colchicine. For the demonstration of cis and trans cisternae of the Golgi apparatus, prolonged osmification, thiamine pyrophosphatase and acid phosphatase activity identification were applied. After treatment with vinblastine or colchicine, polarity of stacks in the Golgi apparatus of surface mucoid cells is preserved although the number of cisternae with thiamine pyrophosphatase or acid phosphatase activity decreases. However, the Golgi apparatus of intestinal absorptive cells completely disintegrates and only a few separated cis or trans cisternae can be identified. The main effect seems to be a reduction of vesicles which can be cytochemically identified as parts of the Golgi apparatus and an accumulation of vesicles which probably originate from budding ER. Communication between the ER and the Golgi apparatus seems to be interrupted.

The endolymphatic sac and inner ear homeostasis. I: Effect of glycerol on the endolymphatic sac with or without colchicine pretreatment

The combined effects of glycerol and colchicine on the endolymphatic sac were investigated in mice. Glycerol induced signs of secretion from the epithelium with formation of secretory granules in the light epithelial cells. Other characteristics of the epithelial lining were also changed resulting in an increased widening of the lateral intercellular spaces, a partial collapse of the lumen and with a deposition of a stainable substance within the lumen. This reaction lasted from 30 min to 24 h following the injection. Pretreatment with colchicine was found to decrease or inhibit the glycerol-induced secretion of macromolecules into the sac. The lumen collapsed but frequently there was no presence of stainable substance. Animals treated with both glycerol and colchicine showed marked signs of inner ear malfunction which could indicate that the secretory activity in the sac might be closely related to the regulation of inner ear fluid homeostasis and that functional disturbances in this system may lead to disorders of inner ear function.

The endolymphatic sac and inner ear homeostasis. II: Effect of glycerol on the sensory end organs with or without colchicine pretreatment

The effects of glycerol and colchicine on the sensory end organs of the inner ear were investigated in mice. Glycerol alone induced a widening of the intercellular spaces lining vestibular dark and transitional cells as well as the marginal cells of the stria vascularis. This was noted within 30 min after the injection of glycerol and was normalized again within 4 h after the injection. Colchicine induced some morphological changes in the inner ear sensory cells, such as dissociation of Golgi complexes etc. These isolated glycerol or colchicine injections did not cause any signs of inner ear functional impairment. Treatment with glycerol following pretreatment with colchicine, however, induced marked inner ear dysfunction with impaired sense of balance and audition. The inner ear morphology revealed a combination of changes as compared with what was observed after isolated treatment with glycerol or colchicine i.e. edema of the stria vascularis, and vestibular dark and transitional cells as well as dissociation of Golgi complexes in the sensory cells. The cochlea showed moderate endolymphatic hydrops. These findings indicate that colchicine affects the inner ear fluid regulating mechanisms which may lead to severe functional derangement after additional glycerol treatment. It is conceivable that the present experiment may serve as a useful model for further studies on inner ear changes related to endolymphatic hydrops and Ménière's disease.

The long-term effects of treatment on the dental condition of children surviving malignant disease

Fifty-two long-term survivors of childhood leukemia or solid tumors had a clinical dental examination along with 49 of their sibling. The 52, with an additional 30 examined in a previous study, were studied radiologically with a panoramic tomogram. All children with leukemia had received chemotherapy for 2 or 3 years and irradiation on standard protocols and the solid tumor group had received chemotherapy for 6 to 24 months. There was no difference between siblings and patients for dental caries, gingivitis, and oral hygiene, mouth opening, overjet, and overbite. More solid-tumor patients had abnormal occlusion (P less than 0.02) and those with abnormalities tended to have been treated at an earlier age. Enamel opacities and hypoplasia were more common in patients than siblings and in the leukemia than in the solid tumor group. Sixty-five percent of the children had abnormalities on radiologic examination including failure of the tooth to develop, small crown, hypoplasia of the crown, and abnormal root development. In most cases the radiologic abnormality could be correlated in time with the patient's treatment and a knowledge of the normal time of tooth development. Three teeth extracted during the course of the study were examined histologically and these showed prominent incremental lines which could be correlated in time with vincristine treatment.

Pattern of secretion in thymic epithelial cells: ultrastructural studies of the effect of blockage at various levels

The observation of secretory phenomena in mouse thymic epithelial cells is disappointing since no real secretion image is found. An adequate technique for such a study is to block the secretion pathway and to observe by electron microscopy cells accumulating secretory products. For this purpose, we used three means of blocking secretion: Firstly, since the thymic epithelial cell is regulated by a feedback phenomenon, secretion was blocked by antibodies against thymulin, one of the hormones secreted by these cells. Secondly, colchicine was used to modify the intracellular transport of the secretory product. In both of these types of experiments, electron microscopy showed a great increase in the number of "clear vacuoles" and their granular contents in epithelial cells. In a third series of experiments, we used monensin at a concentration that blocks the intracellular transport of secretory proteins at the various levels of the Golgi apparatus. In this series, only an increased number of vacuoles was observed, but they appeared devoid of all granular content. It can be concluded that in the thymic epithelial cell, a discrete system of secretion directs the passage of the product, originating in the cisternae of the endoplasmic reticulum, into "clear vacuoles", the terminal element of the cellular secretory apparatus.

Two integral membrane proteins located in the cis-middle and trans-part of the Golgi system acquire sialylated N-linked carbohydrates and display different turnovers and sensitivity to cAMP-dependent phosphorylation

The localization and chemical characteristics of two Golgi integral membrane proteins (GIMPs) have been studied using monoclonal antibodies. The two proteins are segregated in different parts of the Golgi system and whereas GIMPc(130 kD) is located in the cis and medial cisternae, GIMPt (100 kD) is confined in the trans-most cisterna and trans-tubular network. Both GIMPs are glycoproteins that contain N- and O-linked carbohydrates. The N-linked carbohydrates were exclusively of the complex type. Although excluded from the trans-side of the Golgi system, where sialylation is believed to occur, GIMPc acquires sialic acid in both its N- and O-linked carbohydrates. Sialic acid was also detected in the N-linked carbohydrates of GIMPt. GIMPc is apparently phosphorylated in the luminal domain in vivo. Phosphorylation occurred exclusively on serine and was stimulated by dibutyryl cyclic AMP. GIMPc and GIMPt displayed half-lives of 20 and 9 h, respectively.

Secretion of egg white proteins in primary cultured oviduct cells of laying Japanese quail (Coturnix coturnix japonica)

Oviduct (magnum) cells of laying Japanese quails (Coturnix coturnix japonica) were isolated after digestion of the magnum portion by collagenase and dispase and cultured in Dulbecco's modified Eagle medium (DME) supplemented with 10% fetal calf serum. The cultured cells formed a monolayer. Immunoperoxidase staining with antiovalbumin and anticonalbumin antibodies elucidated that more than 90% of the total population of the cells contained ovalbumin and conalbumin within the cytoplasm. The result shows that the cultured cells are composed mainly of tubular gland cells. Cells secreted ovalbumin and conalbumin continuously for several days. Secretion of these egg white proteins was confirmed to be inhibited by colchicine and vinblastine, which means that the microtubular system is involved in the secretion pathway of the proteins, as is widely accepted. Tunicamycin, an inhibitor of glycosylation of proteins, blocked the glycosylation of nascent ovalbumin molecules at a concentration of 5 micrograms/mL in the medium. However, immunoreactive ovalbumin was secreted under these conditions, without being glycosylated. This suggests that the carbohydrate moiety of ovalbumin is not essential for the secretion of ovalbumin. The secretion of ovalbumin was inhibited by brefeldin A, which is supposed to inhibit the transport of proteins from the rough endoplasmic reticulum to the Golgi apparatus. The present method of cultivating egg white-secreting cells will be useful in investigations of mechanisms and regulation of the synthesis and secretion of egg white proteins in birds.

The role of microtubules in human natural killer cell-mediated cytotoxicity

The effect of four different microtubule (MT) inhibitors on the various stages of human natural killer (NK) cell-mediated cytotoxicity was studied. The MT-disrupting effect of the drugs was monitored by indirect immunofluorescence microscopy and transmission electron microscopy. All the drugs tested, vinblastine sulfate, demecolcine, nocodazole, and taxol, had only a slight inhibitory effect on NK activity. Cells with nonfunctional MT were capable of normal conjugate formation and polarization of actin-containing microfilaments. Natural killer cell cytotoxic factor (NKCF) activity produced by cells with nonfunctional MT was slightly diminished. MT disruption caused enlargement of Golgi cisternae, but did not, however, dissociate the overall structural organization of the Golgi complex. The results indicate that fresh human NK cells are capable of lytic activity without functional MT although MT play a small supportive role in production or secretion of NKCF and mediation of the lytic activity. Previous experiments by us and others have strongly suggested that NK cells mediate their cytolytic activity by directed secretion of toxic material. As NK cells with unfunctional microtubules are capable of close to normal secretion the results presented in this report are not inconsistent with the earlier suggested stimulus-secretion model.

Ultrastructure of the choroid plexus epithelium of pigeons treated with drugs: II. Effect of cytochalasin D and colchicine

A remarkable projection of bleblike protrusions, the expulsion of organelles into the protrusions formed on the apical surface, and the separation into the ventricular lumen of these protrusions was the general cellular response of choroidal epithelial cells to intravenous injection of cytochalasin D (CD). The compact microfilament mass and agglomeration of microtubules at the base of the cluster of protrusions reflect the results of cell contraction and displacement of microfilaments induced by CD. In earlier stages after intravenous injections of colchicine, an obvious increase in the number of various-sized vesicles, vacuoles, and lysosomes in the Golgi region was detected. In the later stages, these organelles were seen to accumulate in the basal portion of the epithelial cells. These changes were accompanied by an increase in vacuoles and the disorganization and displacement of the Golgi complex, and they coincided with a decrease in the number of microtubules in apical and basal cytoplasm. These findings suggest that the action of colchicine results in destruction of the three-dimensional architecture between cytoskeletal network and cell organelles. The present results suggest that the cytoskeletal network plays a role in the spatial coordination of the three-dimensional architecture of cell organelles. The study also indicates that the structural differences in the ventricles of the choroid plexus in drug-treated pigeons are manifestations of regional functional specialization in different parts of the ventricular system.

A microtubule-binding protein associated with membranes of the Golgi apparatus

A monoclonal antibody (M3A5), raised against microtubule-associated protein 2 (MAP-2), recognized an antigen associated with the Golgi complex in a variety of non-neuronal tissue culture cells. In double immunofluorescence studies M3A5 staining was very similar to that of specific Golgi markers, even after disruption of the Golgi apparatus organization with monensin or nocodazole. M3A5 recognized one band of Mr approximately 110,000 in immunoblots of culture cell extracts; this protein, designated 110K, was enriched in Golgi stack fractions prepared from rat liver. The 110K protein has been shown to partition into the aqueous phase by Triton X-114 extraction of a Golgi-enriched fraction and was eluted after pH 11.0 carbonate washing. It is therefore likely to be a peripheral membrane protein. Proteinase K treatment of an isolated Golgi stack fraction resulted in complete digestion of the 110K protein, both in the presence and absence of Triton X-100. A the 110K protein is accessible to protease in intact vesicles in vitro, it is presumably located on the cytoplasmic face of the Golgi membrane in vivo. The 110K protein was able to interact specifically with taxol-polymerized microtubules in vitro. These results suggest that the 110K protein may serve to link the Golgi apparatus to the microtubule network and so may belong to a novel class of proteins: the microtubule-binding proteins.

Microtubules and actin filaments are not critically involved in the biogenesis of epithelial cell surface polarity

We have studied the role of microtubules and actin filaments in the biogenesis of epithelial cell surface polarity, using influenza hemagglutinin and vesicular stomatitis G protein as model apical and basolateral proteins in infected Madin-Darby canine kidney cells. Addition of colchicine or nocodazole to confluent monolayers at concentrations sufficient to completely disassemble microtubules did not affect the asymmetric budding of influenza or vesicular stomatitis virus and only slightly reduced the typical asymmetric surface distribution of their envelope proteins, despite extensive cytoplasmic redistribution of the Golgi apparatus. Alteration of microtubular function by taxol or dissociation of actin filaments by cytochalasin D also failed to have a significant effect. Furthermore, neither colchicine nor cytochalasin D pretreatment blocked the ability of subconfluent Madin-Darby canine kidney cells to sustain polarized budding of influenza virus a few hours after attachment to the substrate. Our results indicate that domain-specific microtubule or actin filament "tracks" are not responsible for the vectorial delivery of apically or basolaterally directed transport vesicles. In conjunction with currently available evidence, they are compatible with a model in which receptors in the cytoplasmic aspect of apical or basolateral regions provide vectoriality to the transport of vesicles carrying plasma membrane proteins to their final surface localization.

Effects of antimicrotubule agents on phospholipid metabolism in rat hepatic subcellular membranes

Treatment of animals with antimicrotubule drugs has been shown to cause a perplexing variety of cellular changes which, theoretically, could be the result of changes in endomembrane biosynthesis, composition or flow. In the current study we have focused on this possibility by identifying antimicrotubule drug-induced changes in the phospholipid metabolism of hepatic subcellular membranes. Young adult rats were pretreated with radiolabeled [32 P]orthophosphate for 12 hr, and subsequently given saline, colchicine (2.5 mg/kg body wt) or vinblastine (20 mg/kg body wt) for 4 additional hr. Afterwards, the livers were homogenized, and separate microsomal and Golgi membrane fractions were prepared and subjected to phospholipid extraction and identification using two-dimensional thin-layer chromatography. The results show that colchicine and vinblastine given in vivo caused specific, rapid and in some cases, dramatic changes in phospholipid turnover in different membrane fractions of rat liver. The drugs specifically increased labeling of phosphatidylinositol-4-monophosphate and phosphatidylinositol-4,5-biphosphate and decreased the radioactivity associated with phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol in all fractions examined. In contrast, the antimicrotubule drugs produced a differential effect on the labeling pattern of sphingomyelin and lysophosphatidylcholine, i.e. they stimulated labeling of these phospholipids in microsomes, produced no changes in heavy Golgi fractions, and markedly increased their labeling in light Golgi fractions. These data suggest that antimicrotubule drugs restrict the incorporation of certain precursor phospholipids into forming membranes but do not affect the subsequent metabolism of these phospholipids. At the same time, the drugs appear to retard the flow of membranes from one cellular compartment to another.

Microtubules and the organization of the Golgi complex

Electron microscopic and cytochemical studies indicate that microtubules play an important role in the organization of the Golgi complex in mammalian cells. During interphase microtubules form a radiating pattern in the cytoplasm, originating from the pericentriolar region (microtubule-organizing centre). The stacks of Golgi cisternae and the associated secretory vesicles and lysosomes are arranged in a circumscribed juxtanuclear area, usually centered around the centrioles, and show a defined orientation in relation to the rough endoplasmic reticulum. Exposure of cells to drugs such as colchicine, vinblastine and nocodazole leads to disassembly of microtubules and disorganization of the Golgi complex, most typically a dispersion of its stacks of cisternae throughout the cytoplasm. These alterations are accompanied by disturbances in the intracellular transport, processing and release of secretory products as well as inhibition of endocytosis. The observations suggest that microtubules are partly responsible for the maintenance and functioning of the Golgi complex, possibly by arranging its stacks of cisternae three-dimensionally within the cell and in relation to other organelles and ensuring a normal flow of material into and away from them. During mitosis, microtubules disassemble (prophase) and a mitotic spindle is built up (metaphase) to take care of the subsequent separation of the chromosomes (anaphase). The breaking up of the microtubular cytoskeleton is followed by vesiculation of the rough endoplasmic reticulum and partial atrophy, as well as dispersion of the stacks of Golgi cisternae. After completion of the nuclear division (telophase), the radiating microtubule pattern is re-established and the rough endoplasmic reticulum and the Golgi complex resume their normal interphase structure. This sequence of events is believed to fulfil the double function to provide tubulin units and space for construction of the mitotic spindle and to guarantee an approximately equal distribution of the rough endoplasmic reticulum and the Golgi complex on the two daughter cells.

Associations of elements of the Golgi apparatus with microtubules

The intracellular spatial relationships between elements of the Golgi apparatus (GA) and microtubules in interphase cells have been explored by double immunofluorescence microscopy. By using cultured cells infected with the temperature-sensitive Orsay-45 mutant of vesicular stomatitis virus and a temperature shift-down protocol, we visualized functional elements of the GA by immunolabeling of the G protein of the virus that was arrested in the GA during its intracellular passage to the plasma membrane 13 min after the temperature shift-down. Complete disassembly of the cytoplasmic microtubules by nocodazole at the nonpermissive temperature before the temperature shift led to the dispersal of the GA elements, from their normal compact perinuclear configuration close to the microtubule-organizing center (MTOC) into the cell periphery. Washout of the nocodazole that led to the reassembly of the microtubules from the MTOC also led to the recompaction of the GA elements to their normal configuration. During this recompaction process, GA elements were seen in close lateral apposition to microtubules. In cells treated with nocodazole followed by taxol, an MTOC developed, but most of the microtubules were free of the MTOC and were assembled into bundles in the cell periphery. Under these circumstances, the GA elements that had been dispersed into the cell periphery by the nocodazole treatment remained dispersed despite the presence of an MTOC. In cells treated directly with taxol, free microtubules were seen in the cytoplasm in widely different, bundled configurations from one cell to another, but, in each case, elements of the GA appeared to be associated with one of the two end regions of the microtubule bundles, and to be uncorrelated with the locations of the vimentin intermediate filaments in these cells. These results are interpreted to suggest two types of associations of elements of the GA with microtubules: one lateral, and the other (more stable) end-on. The end-on association is suggested to involve the minus-end regions of microtubules, and it is proposed that this accounts for the GA-MTOC association in normal cells.

Influence of colchicine and vinblastine on the intracellular migration of secretory and membrane glycoproteins: III. Inhibition of intracellular migration of membrane glycoproteins in rat intestinal columnar cells and hepatocytes as visualized by light and electron-microscope radioautography after 3H-fucose injection

In the first paper of this series (Bennett et al., 1984), light-microscope radioautographic studies showed that colchicine or vinblastine inhibited intracellular migration of glycoproteins out of the Golgi region in a variety of cell types. In the present work, the effects of these drugs on migration of membrane glycoproteins have been examined at the ultrastructural level in duodenal villous columnar cells and hepatocytes. Young (40 gm) rats were given a single intravenous injection of colchicine (4.0 mg) or vinblastine (2.0 mg). At 10 min after colchicine and 30 min after vinblastine administration, the rats were injected with 3H-fucose. Control rats received 3H-fucose only. All rats were sacrificed 90 min after 3H-fucose injection and their tissues processed for radioautography. In duodenal villous columnar cells, 3H-fucose labeling of the apical plasma membrane was reduced by 51% after colchicine and by 67% after vinblastine treatment; but there was little change in labeling of the lateral plasma membrane. Labeling of the Golgi apparatus increased. This suggests that labeled glycoproteins destined for the apical plasma membrane were inhibited from leaving the Golgi region, while migration to the lateral plasma membrane was not impaired. In hepatocytes, labeling of the sinusoidal plasma membrane was reduced by 83% after colchicine and by 85% after vinblastine treatment. Labeling of the lateral plasma membrane also decreased, although not so dramatically. Labeling of the Golgi apparatus and neighboring secretory vesicles increased. This indicates that the drugs inhibited migration of membrane glycoproteins from the Golgi region to the various portions of the plasma membrane. Accumulation of secretory vesicles at the sinusoidal front suggests that exocytosis may also have been partially inhibited. In both cell types, microtubules almost completely disappeared after drug treatment. Microtubules may, therefore, be necessary for intracellular transport of membrane glycoproteins, although the possibility of a direct action of these drugs on Golgi or plasma membranes must also be considered.

Influence of colchicine and vinblastine on the intracellular migration of secretory and membrane glycoproteins: II. Inhibition of secretion of thyroglobulin in rat thyroid follicular cells as visualized by radioautography after 3H-fucose injection

Young (40 gm) rats were given a single intravenous injection of colchicine (4.0 mg) or vinblastine (2.0 mg). At 10 min after colchicine and 30 min after vinblastine administration, the rats were injected with 3H-fucose. Control rats received 3H-fucose only. All rats were sacrificed 90 min after 3H-fucose injection and their tissues processed for radioautography. In thyroid follicular cells of control animals, at this time interval, 57% of the total label was associated with colloid and secretory vesicles in the apical cytoplasm while 27% was localized in the Golgi apparatus and neighboring vesicles. In experimental animals, the proportion of label in colloid and apical vesicles was reduced by more than 69% after colchicine and more than 83% after vinblastine treatment. The proportion of label in the Golgi region, on the other hand, increased by more than 125% after colchicine and more than 179% after vinblastine treatment. Within the Golgi region, the great majority of the label was associated with secretory vesicles which accumulated adjacent to the trans face of the Golgi stacks. It is concluded that the drugs do not interfere with passage of newly synthesized thyroglobulin from the Golgi saccules to nearby secretory vesicles, but do inhibit intracellular migration of these vesicles to the cell apex. In most cells the number of vesicles in the apical cytoplasm diminished, but this was not always the case, suggesting that exocytosis may also be partially inhibited. The loss of microtubules in drug-treated cells suggests that the microtubules may be necessary for intracellular transport of thyroglobulin.

Role of microtubules in the organization and localization of the Golgi apparatus

Normal interphase PtK2 and A549 cells display long microtubules radiating from the microtubule-organizing center (MTOC) to the plasma membrane. Both MTOC and Golgi apparatus are contained in the same perinuclear area. Treatment of cells with 1 microM colcemid for 2 h results in microtubule depolymerization and fragmentation of the Golgi apparatus into elements scattered throughout the cytoplasm. Both normal microtubules and the Golgi apparatus assemble again following removal of colcemid. Injection of the alpha, beta-nonhydrolyzable GTP analog, guanosine 5'(alpha, beta-methylene)diphosphate [pp(CH2)pG], into interphase cells growing in normal medium results in the formation of microtubule bundles resistant to colcemid and prevents the fragmentation of the Golgi apparatus. Injection of pp(CH2)pG into cells incubated with colcemid results in substitution of tubulin ribbons for microtubules and has no effect on the Golgi-derived elements scattered throughout the cytoplasm. Removal of colcemid 1 h after the injection of pp(CH2)pG results in polymerization of large numbers of short, single randomly oriented microtubules, whereas the Golgi apparatus remains fragmented. Treatment of cells with 10 microM taxol for 3 h results both in polymerization of microtubule bundles without relation to the MTOC in the cell periphery and fragmentation of the Golgi apparatus. The Golgi-derived fragments are present exclusively in regions of the peripheral cytoplasm enriched in microtubules. The codistribution of microtubules and Golgi elements can be reversed in taxol-treated cells by injection of a monoclonal (YL 1/2) antibody reacting specifically with the tyrosylated form of alpha-tubulin. Cells incubated with colcemid after treatment with taxol have large numbers of Golgi-derived elements in close association with colcemid-resistant microtubule bundles. Incubation of cells with 50 microM vinblastine for 90 min results in microtubule dissembly, formation of tubulin paracrystals, and fragmentation of the Golgi apparatus into elements without relation to the tubulin paracrystals.

Immunological characterization of the major chick cartilage proteoglycan and its intracellular localization in cultured chondroblasts: a comparison with Type II procollagen

Polyclonal antibodies were raised in a rabbit against the major proteoglycan of chick sternal cartilage. A total of six antisera was obtained, three after the first booster injection (A1, A2, and A3) and three after the second booster injection (A4, A5, and A6). The A1 antiserum, which was characterized in most detail, immunoprecipitated native as well as chondroitinase ABC-digested or chondroitinase ABC/keratanase-digested cartilage proteoglycan synthesized by cultured chick chondroblasts, but failed to immunoprecipitate the major proteoglycan synthesized by chick skin fibroblasts. This antiserum was also able to immunoprecipitate the cartilage proteoglycan core protein newly synthesized by cultured chondroblasts, but no other major cell protein. However, the late bleed antisera obtained from the same rabbit after a second booster injection reacted with a new chondroblast-specific polypeptide(s) of approximately 60,000 mol wt in addition to the cartilage proteoglycan. By immunofluorescence procedures, the A1 antiserum stained the extracellular proteoglycan matrix of cultured chondroblasts but not that of skin fibroblasts. Following enzymatic removal of the extracellular matrix and cell membrane permeabilization, this antiserum stained primarily a large, juxtanuclear structure. Additional radioautographic evidence suggests that this structure represents the Golgi complex. Similar immunofluorescent staining with antibodies to the cartilage-characteristic Type II collagen revealed that type II procollagen was localized in numerous cytoplasmic, vacuole-like structures which were scattered throughout most of the chondroblast cytoplasm but were notably scanty in the Golgi complex area. In conclusion, our data suggest the transit of the major cartilage proteoglycan through the Golgi complex of cultured chondroblasts and possible differences in the intracellular distribution of newly synthesized cartilage proteoglycan and Type II procollagen.

A rat monoclonal antibody reacting specifically with the tyrosylated form of alpha-tubulin. II. Effects on cell movement, organization of microtubules, and intermediate filaments, and arrangement of Golgi elements

A rat monoclonal antibody against yeast alpha-tubulin (clone YL 1/2; Kilmartin, J. V., B. Wright, and C. Milstein, 1982, J. Cell Biol., 93:576-582) that reacts specifically with the tyrosylated form of alpha-tubulin and readily binds to tubulin in microtubules when injected into cultured cells (see Wehland, J., M. C. Willingham, and I. V. Sandoval, 1983, J. Cell Biol., 97:1467-1475) was used to study microtubule organization and function in living cells. Depending on the concentration of YL 1/2 that was injected the following striking effects were observed: (a) When injected at a low concentration (2 mg IgG/ml in the injection solution), where microtubules were decorated without changing their distribution, intracellular movement of cell organelles (saltatory movement) and cell translocation were not affected. Intermediate concentrations (6 mg IgG/ml) that induced bundling but no perinuclear aggregation of microtubules abolished saltatory movement and cell translocation, and high concentrations (greater than 12 mg IgG/ml) that induced perinuclear aggregation of microtubules showed the same effect. (b) YL 1/2, when injected at intermediate and high concentrations, arrested cells in mitosis. Such cells showed no normal spindle structures. (c) Injection of an intermediate concentration of YL 1/2 that stopped saltatory movement caused little or no aggregation of intermediate filaments and no dispersion of the Golgi complex. After injection of high concentrations, resulting in perinuclear aggregation of microtubules, intermediate filaments formed perinuclear bundles and the Golgi complex became dispersed analogous to results obtained after treatment of cells with colcemid. (d) When rhodamine-conjugated YL 1/2 was injected at concentrations that stopped saltatory movement and arrested cells in mitosis, microtubule structures could be visualized and followed for several hours in living cells by video image intensification microscopy. They showed little or no change in distribution and organization during observation, even though these microtubule structures appeared not to be stabilized by injected YL 1/2 since they were readily depolymerized by colcemid or cold treatment and repolymerized upon drug removal or rewarming to 37 degrees C, respectively. These results are discussed in terms of the participation of microtubules in cellular activities such as cell movement and cytoplasmic organization and in terms of the specificity of YL 1/2 for the tyrosylated form of alpha-tubulin.

Synthesis and secretion of proteoglycans by cultured chondrocytes. Effects of monensin, colchicine and beta-D-xyloside

Chondrocytes, isolated from elastic ear cartilage of young rabbits, were grown in monolayer cultures in Ham's F-12 medium. Synthesis and secretion of macromolecules were monitored by labelling with radioactive precursors and the effect of monensin and other experimental agents was investigated. Monensin caused an inhibition of the incorporation of precursors into macromolecular material and a moderate intracellular accumulation when used in higher concentrations. The effect was more pronounced for 35SO4 than for 3H-labelled glucose or proline. p-Nitrophenyl-beta-D-xyloside alleviated this inhibition to some extent, but there was a concomitant increase in the amount of intracellular labelled material. Colchicine and monensin together caused a severe inhibition of the incorporation of 35SO4 and a marked shift of the label to the intracellular compartment. Colchicine also increased the sensitivity of the cells to monensin, lowering the minimal effective concentration about one order of magnitude. The latter results are consistent with the idea that cytoplasmic microtubules have a stabilizing function on the secretory pathways and, that their removal by colchicine, causing a 'randomizing' of the Golgi complex, makes these pathways more vulnerable to monensin.

Morphological alterations in dorsal root ganglion neurons and supporting cells of organotypic mouse spinal cord-ganglion cultures exposed to taxol

Explants of 14-day fetal mouse spinal cord with attached dorsal root ganglia, which had become differentiated over 2-3 weeks in culture, were exposed to 1-2 microM taxol for up to 6 days. The culture medium was supplemented with nerve growth factor (300 units/ml) during exposure to the drug. By 3-6 days in taxol, unusually numerous microtubules were seen in peripheral perikaryal and proximal neuritic regions of ganglion neurons. Microtubules also engirdled massive aggregations of pleomorphic vesicular/cisternal elements in many neurons. These aggregates were visible as unusual 'clear' spheroidal regions in the living cells, and were often as large as the nuclei. Some of the elements comprising these striking vesicular/cisternal accumulations appeared to be portions of disrupted Golgi complexes normally polarized around the cytocentrum, as well as hypertrophied smooth endoplasmic reticulum formations. In other neuronal areas, Golgi complexes and other organelles were altered or disrupted to lesser degrees. Ordered microtubular arrays occurred along endoplasmic reticulum cisternae both in neuron somata and neurites. Over time, a plethora of microtubules assembled throughout the perikarya in various orientations apparently unrelated to microtubule organizing centers. Unlike the effects of other plant alkaloids that interact with tubulin, there was no discernible increase in filaments, although their distribution appeared altered. Concentric ordered microtubular-macromolecular lamellated complexes were seen only in neurites. Neuronal nuclei were misshapen, often displaced, and displayed fine structure reminiscent of chromatolysis. Satellite and Schwann cells contained atypically abundant microtubules, abnormal cisternae, disrupted Golgi complexes, and increased lysosomes. Some nuclei displayed abnormal chromatin, and in rare cases even microtubules. We suggest that taxol alters the distribution, integrity, and/or organization of organelle systems in dorsal root ganglion cells by engendering unusually abundant microtubules in abnormal groupings and aberrant locations in these cells.

Disparate effects of monensin and colchicine on intracellular processing of secretory proteins in cultured rat hepatocytes

We have studied the biosynthesis and intracellular processing of three major secretory proteins, albumin, alpha 1-protease inhibitor and alpha 2u-globulin, in cultured rat hepatocytes. The effect of secretion-blocking agents, monensin, a monovalent ionophore, and the microtubule-affecting agents colchicine and taxol was determined. In the control cells, alpha 1-protease inhibitor, a glycoprotein, was first synthesized as an endoglycosidase-H-sensitive form with Mr 51 000, and then processed to two endoglycosidase-H-resistant forms having Mr 51 000 and 56 000, the latter of which was secreted into the medium. Initially synthesized proalbumin was converted with chase to serum-type albumin, while no pro-type precursor was identified for alpha 2u-globulin. In the cells treated with colchicine or taxol, in which secretion was greatly inhibited, the fully processed alpha 1-protease inhibitor and albumin accumulated and were finally secreted into the medium. In the monensin-treated cells, however, most of the newly synthesized alpha 1-protease inhibitor and albumin were not processed to the final mature forms, resulting in accumulation of two 51 000-Mr forms and proalbumin, respectively. Moreover in treated cells, proalbumin and the endoglycosidase-H-resistant alpha 1-protease inhibitor were finally secreted into the medium. Such an effect was not caused by NH4Cl which also inhibited the secretion and is known to exert the similar effect as monensin on the receptor-mediated endocytosis pathway. Based on these results, the use of monensin may prove valuable for more detailed analysis of intracellular processing of various proteins.

Role of microtubules in the distribution of the Golgi apparatus: effect of taxol and microinjected anti-alpha-tubulin antibodies

Immunofluorescence microscopy reveals that both microtubule organizing center (MTOC) and Golgi apparatus are contained in the same perinuclear area of A549 cells in interphase. The cells display long microtubules stretching radially from the MTOC to the plasma membrane. Treatment of cells with taxol results in polymerization of microtubules without relation to the MTOC and formation of microtubule bundles predominantly localized in the cell periphery. After incubation with taxol, the Golgi apparatus is fragmented and is conspicuously present in areas of the cytoplasm enriched in microtubules. Incubation of cells with Colcemid results in complete depolymerization of microtubules and fragmentation of the Golgi into elements randomly distributed throughout the cytoplasm. Cells treated with taxol before being incubated with Colcemid contain large numbers of Golgi-derived elements in close association with Colcemid-resistant microtubules. Microtubule depolymerization by vinblastine also is followed by fragmentation of the Golgi apparatus. These Golgi-derived elements show no association with the atypical polymers of tubulin induced by vinblastine. The codistribution of Golgi-derived elements with taxol-induced microtubule bundles can be reversed by microinjection of a monoclonal (YL 1/2) antibody reacting specifically with the tyrosylated form of alpha-tubulin.

Effect of antimicrotubule agents on terminal glycosyltransferases and other enzymes associated with rat liver subcellular fractions

Previous studies have shown that anti microtubule agents disrupt Golgi complexes in hepatocytes and other cells, causing breakdown or vesiculation of Golgi cisternal membranes. Whether this change in the structure of the Golgi membranes is associated with changes in Golgi membrane function is not known. The present study was initiated to investigate this issue; i.e., to determine whether anti-microtubule agents that cause structural changes in Golgi membranes in vivo would, at the same time, affect characteristic enzyme functions of Golgi membranes. To this end, colchicine was given to young rats in vivo and various hepatic subcellular membranes were subsequently isolated and utilized for enzyme assays. Initially it was shown that colchicine (2.5 mg/kg body wt.) given for 5h significantly decreased the activities of the Golgi membrane associated enzymes galactosyl-, sialyl- and N-acetylglucosaminyl-transferases. More detailed experiments indicated that low doses of colchicine (0.8 mg/kg body wt.), although less effective than higher doses, decreased the activities of the terminal glycosylating enzymes maximally at 5h, with partial and complete recovery at 12 and 24h respectively. Treatment in vivo of rats with vinblastine (20 mg/kg body wt.) for 5h mimicked the action of colchicine. Two microsomal glycosylating enzymes (mannosyl and N acetylglucosaminyl transferases) were unaffected by the treatment with colchicine, as were various hepatic 'marker' enzymes such as 5' nucleotidase, glucose 6 phosphatase and succinate: 2-(p iodophenyl)-3-(p nitrophenyl)-5-phenyltetrazolium reductase (succinate dehydrogenase; EC 1.3.99.1), which were found to be enriched in plasma membrane, endoplasmic-reticulum and mitochondrial-membrane fractions respectively. These results show that anti-microtubule agents specifically suppress the activity of Golgi-associated glycosyltransferases in liver. Although it seems likely that these changes are related to the previously observed structural changes in hepatocyte Golgi complexes after colchicine treatment, to what extent the results are linked to the interaction of colchicine with microtubule protein remains to be clarified.

Studies on vinblastine-induced autophagocytosis in mouse liver. III. A quantitative study

The microtubule inhibitor vinblastine (25 mg/kg, i.p.) induces autophagocytosis in mouse hepatocytes. The formation of autophagic vacuoles, their contents, and other cellular changes after vinblastine injection in hepatocytes, were studied by light and electron microscopic morphometric analysis. The volume density of autophagic vacuoles increased significantly during the experimental period (24 h). This increase was due to the significant increase in their number, which was approximately 5-fold 4 h, 12 h and 24 h after vinblastine injection. The mean volume of the autophagic vacuoles increased significantly 1 h after vinblastine injection, at which time the formation of new autophagic vacuoles was at its greatest. There was an accumulation of single membrane-limited, obviously older autophagic vacuoles in the cytoplasm. Their volume density was at its maximum 12 h after injection, suggesting a retarded turnover of autophagic vacuoles. The segregation of cytoplasmic components into autophagic vacuoles may not be selective after vinblastine injection. The injurious effects of vinblastine were evident both in light and electron microscopic studies. In the parenchymal cells the Golgi cisternae were dilated and disorganized and the volume density of the Golgi apparatus was significantly decreased 12 h after vinblastine injection. The volume density of lysosomes was increased during the 12 h after vinblastine injection. Vesicles containing very low density lipoprotein particles accumulated in the cytoplasm so that their volume density was significantly increased during the entire experimental period. Vinblastine apparently interfered with the transport and secretion of the very low density lipoproteins from the parenchymal cells.

Microtubules and protein secretion in rat lacrimal glands: localization of short-term effects of colchicine on the secretory process

The pathway and kinetics of the secretory protein transport in rat lacrimal exorbital gland have been established by an in vitro time-course radioautographic study of pulse-labeled protein secretion. The colchicine-sensitive steps have been localized by using the drug at various times with respect to the pulse labeling of proteins. Colchicine (10 microM) does not block any step of the secretory protein transport, but when introduced before the pulse it decreases the transfer of labeled proteins from the rough endoplasmic reticulum to the Golgi area, suppressing their temporary accumulation in the Golgi area before any alteration of this organelle is detectable. Moreover, colchicine inhibits protein release only from the secretory granules formed in its presence because the peroxidase discharge is diminished 1 h after colchicine addition, and the secretion of newly synthesized proteins is strongly inhibited only when colchicine is introduced before secretory granule formation. Morphometric studies show that there is a great increase of secondary lysosomes, related to crinophagy, as early as 40-50 min after colchicine is added. However, changes in lysosomal enzymatic activities remained biochemically undetectable. We conclude that: (a) the labile microtubular system does not seem indispensable for protein transport in the rough endoplasmic reticulum-Golgi area but may facilitate this step, perhaps by maintaining the spatial organization of this area; and (b) in the lacrimal gland, colchicine inhibits protein release not by acting on the steps of secretion following the secretory granule formation, but by acting chiefly on the steps preceding secretory granule formation, perhaps by making the secretory granules formed in its presence incapable of discharging their content.

A monoclonal antibody that recognizes Golgi-associated protein of cultured fibroblast cells

We have obtained a hybridoma clone, JLJ5a, which secretes monospecific antibody directed against a 110-kdalton protein of gerbil fibroma cells, Rat-1 fibroblasts, and L6 myoblasts. It appears to be localized in the Golgi apparatus by the following criteria: (a) In double-staining experiments the localization of the 110-kdalton protein by the JLJ5a monoclonal antibody was coincident with the reaction products of thiamine pyrophosphatase (one of the enzyme markers of the Golgi apparatus; Novikoff and Goldfischer, 1961, Proc. Natl. Acad. Sci. U.S.A. 47:802-810) in the same cells. (b) The staining pattern of the JLJ5a monoclonal antibody became fragmented and dispersed into vacuoles after pretreatment of the cells with Colcemid or monensin.

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.

An electron microscopic radioautographic study of collagen secretion in periodontal ligament fibroblasts of the mouse: II. Colchicine-treated fibroblasts

Colchicine administered intravenously depolymerized microtubules and disrupted the normal organization of the Golgi apparatus in periodontal ligament fibroblasts. Radioautography with 3H-proline indicated that collagen secretion was completely inhibited during a period of approximately 4 hours following the onset of the colchicine effect. During this period of secretory inhibition, labeled collagen precursors were present within a variety of dense bodies, primarily located in a juxtanuclear location replacing the normal Golgi complex. The time course of 3H-proline labeling from 2 to 8 hours suggested that small, newly formed dense bodies fused to form larger dense bodies and pleomorphic structures (zebra bodies), within which collagen precursors appeared to undergo partial polymerization. Autophagosomes, many labeled with 3H-proline, also increased in number after colchicine administration. A gradual decline in 3H-proline label occurred from 4 to 24 hours, presumably due to exocytosis of dense bodies or by the digestion of labeled collagen precursors within autophagosomes. These results support the concept that an intact microtubular network is essential for the organized transport of collagen precursors, from the rough endoplasmic reticulum to the Golgi apparatus, and the eventual transport and exocytosis of collagen secretory granules.