CB-treated Cells Research Articles

Drastic Change of Surface Morphology of Cesium–Formamidinium Perovskite Solar Cells by Antisolvent Processing

Antisolvent method is one of the most common and efficient techniques used to prepare high-quality lead-halide perovskite film for perovskite solar cells (PSCs). Antisolvent method is crucial for improving the poor morphology of specific perovskite compositions, such as methylammonium (MA)-free perovskite, a promising PSC absorber that offers greater thermal stability. Here, we report the superior performance of di-iso-propyl ether (DIE) as an antisolvent for the fabrication of MA-free formamidinium (FA)-Cs perovskites. Conventionally used antisolvent, chlorobenzene (CB), often causes uneven morphology of FA-Cs perovskites due to the formation of millimeter-length walls that extend up to 2 μm in height, which penetrate the hole transport layer and make contact with the gold electrode. Scanning electron microscopy and X-ray diffraction measurements of as-prepared and thermal-annealed CB-treated films indicate that the walls appear during the antisolvent dripping process due to the strong solvent extraction property of the CB. CB-treated and DIE-treated, (FAPbI3)0.85(CsPbBr3)0.15-based, PSCs were fabricated by means of DIE and CB treatment. The DIE-treated cells yielded efficiency up to 18%, improvement on CB-treated cells due to increased fill factor (FF). These cells showed a longer shelf life than CB-treated cells under ambient storage conditions.

Multi-modal liquid biopsy platform for cancer screening: screening both cancer-associated rare cells and cancer cell-derived vesicles on the fabric filters for a reliable liquid biopsy analysis

Circulating tumor cells (CTCs) are receiving a great amount of scientific interest as a diagnostic biomarker for various types of cancer. Despite the recent progress in the development of highly sensitive CTC isolation devices, post-capture analysis of CTCs is still hindered by technical challenges associated with their rarity. Herein, we present a multi-modal CTC screening platform which is capable to analyze CTCs and CTC-derived extracellular vesicles (EVs), simultaneously from a single sample. Cytochalasin B (CB) treatment promotes cells to release large number of EVs from their surface, as demonstrated by CB-treated cells (5 µg/mL for 3 h) secreting 3.5-fold more EVs, compared to the non-treated cells. CB further generates 1.7-fold more EVs from the cells captured on our CTC filtration device (the fabric filter), compared to those from the cell culture flasks, owing to its multiple pore structure design which reduces the non-specific binding of EVs. Both CB-treated cancer cells and CB-induced EVs are found to overexpress tumor-associated markers, demonstrating a potential for the development of CTC dual-screening platform. Collectively, the results presented in this study reveal that our multi-modal cancer screening platform can synergistically improve the reliability and efficacy of the current CTC analysis systems.

Dynamic FtsA and FtsZ localization and outer membrane alterations during polar growth and cell division in Agrobacterium tumefaciens

Growth and cell division in rod-shaped bacteria have been primarily studied in species that grow predominantly by peptidoglycan (PG) synthesis along the length of the cell. Rhizobiales species, however, predominantly grow by PG synthesis at a single pole. Here we characterize the dynamic localization of several Agrobacterium tumefaciens components during the cell cycle. First, the lipophilic dye FM 4-64 predominantly stains the outer membranes of old poles versus growing poles. In cells about to divide, however, both poles are equally labeled with FM 4-64, but the constriction site is not. Second, the cell-division protein FtsA alternates from unipolar foci in the shortest cells to unipolar and midcell localization in cells of intermediate length, to strictly midcell localization in the longest cells undergoing septation. Third, the cell division protein FtsZ localizes in a cell-cycle pattern similar to, but more complex than, FtsA. Finally, because PG synthesis is spatially and temporally regulated during the cell cycle, we treated cells with sublethal concentrations of carbenicillin (Cb) to assess the role of penicillin-binding proteins in growth and cell division. Cb-treated cells formed midcell circumferential bulges, suggesting that interrupted PG synthesis destabilizes the septum. Midcell bulges contained bands or foci of FtsA-GFP and FtsZ-GFP and no FM 4-64 label, as in untreated cells. There were no abnormal morphologies at the growth poles in Cb-treated cells, suggesting unipolar growth uses Cb-insensitive PG synthesis enzymes.

Importance of cytoskeletal elements in volume regulatory responses of trout hepatocytes

The role of cytoskeletal elements in volume regulation was studied in trout hepatocytes by investigating changes in F-actin distribution during anisotonic exposure and assessing the impact of cytoskeleton disruption on volume regulatory responses. Hypotonic challenge caused a significant decrease in the ratio of cortical to cytoplasmic F-actin, whereas this ratio was unaffected in hypertonic saline. Disruption of microfilaments with cytochalasin B (CB) or cytochalasin D significantly slowed volume recovery following hypo- and hypertonic exposure in both attached and suspended cells. The decrease of net proton release and the intracellular acidification elicited by hypotonicity were unaltered by CB, whereas the increase of proton release in hypertonic saline was dramatically reduced. Because amiloride almost completely blocked the hypertonic increase of proton release and cytoskeleton disruption diminished the associated increase of intracellular pH (pH(i)), we suggest that F-actin disruption affected Na(+)/H(+) exchanger activity. In line with this, pH(i) recovery after an ammonium prepulse was significantly inhibited in CB-treated cells. The increase of cytosolic Na(+) under hypertonic conditions was not diminished but, rather, enhanced by F-actin disruption, presumably due to inhibited Na(+)-K(+)-ATPase activity and stimulated Na(+) channel activity. The elevation of cytosolic Ca(2+) in hypertonic medium was significantly reduced by CB. Altogether, our results indicate that the F-actin network is of crucial importance in the cellular responses to anisotonic conditions, possibly via interaction with the activity of ion transporters and with signalling cascades responsible for their activation. Disruption of microtubules with colchicine had no effect on any of the parameters investigated.

Dexamethasone Inhibits Maturation and Alters Function of Monocyte-Derived Dendritic Cells from Cord Blood

Critically ill infants are treated with dexamethasone (Dx) and other glucocorticoids to reduce inflammation and to promote lung and cardiac function. The neonatal immune system is immature, so neonatal dendritic cells (DCs) might be especially sensitive to glucocorticoid-mediated immunosuppression. To test this, we compared Dx treatment of monocyte-derived DCs from cord (CB) and adult blood (AB). Dx decreased CD1a levels on both AB and CB DCs. CB-treated cells also exhibited decreased expression of CD83 and increased expression of CD14, alterations not observed in AB DCs. Characteristic immature endocytic activity was sustained and enhanced in Dx-treated CB DCs, whereas AB DCs matured normally. Maintenance of endocytosis corresponded with CD14 expression. Dx markedly increased CB DC IL-10, a T cell helper 2 (Th2)-preferential cytokine, while reducing IL-12, a counterbalancing Th1 cytokine. AB DCs were also affected, but increases in IL-10 and decreases in IL-12 were more modest. Dx treatment also inhibited DC-induced T cell proliferation, but CB DCs were inhibited more. In short, neonatal DCs seemed to be especially sensitive to the immunosuppressive effects of Dx as indicated by altered phenotype, endocytic function, ability to stimulate T cells, and cytokine shift favoring Th2. These alterations in DC function are consistent with an increased risk for certain infections and atopic diseases.

Phorbor myristate acetate induces NADPH oxidase activity of cytochalasin B-primed neutrophils through the protein kinase C-independent pathway.

We examined the effect of cytochalasin B (CB) or granulocyte colony stimulating factor (GCSF) on superoxide radical (O2-) production of neutrophils by phorbor myristate acetate (PMA)-stimulation. It was observed that O2- generation of intact and GCSF-treated neutrophils by PMA-stimulation showed a lag during the early stage, and was largely inhibited by 1-(5-isoquinoline-sulfonyl)-3-methyl-piperazine (200 microm) or GF109203X (GFX) (0.2 microM), but not by ethanol (1%) and wortmannin (100 nM). In contrast, O2- generation of CB-pretreated neutrophils by PMA-stimulation did not show a lag, but was less than that of intact cells, and was only minimally depressed by the above inhibitors, but was markedly depressed by the simultaneous addition of GFX and ethanol or GFX and wortmannin. Although translocation of p47phox and p67phox to the membrane fraction by PMA-stimulation of intact and GCSF-treated neutrophils occurred in parallel with O2- production, that of CB-treated neutrophils by PMA-stimulation was not always proportional to O2- production. These findings suggest that pretreatment of neutrophils with CB dramatically alters the PMA response of the cells; that is, the protein kinase C-dependent pathway is largely depressed, and a phospholipase D-dependent one for NADPH oxidase activation appears in CB-treated cells.

Endothelin-induced cytoskeletal actin re-organization in cultured astrocytes: inhibition by C3 ADP-ribosyltransferase.

We investigated signal transduction mechanisms of endothelin (ET) receptor-mediated actin re-organization of rat cultured astrocytes. Staining of filamentous actin (F-actin) showed that stress fibers were a prominent cytoskeletal actin structure in protoplasmic astrocytes. A treatment with 0.5 mM dibutyryl cAMP (DBcAMP) caused cytoplasmic retraction and disappearance of stress fibers of astrocytes. A subsequent addition of 1 nM ET-3 after the DBcAMP treatment expanded the cytoplasm and stimulated stress fiber formation. ET-1, sarafotoxin S6b, and [Ala1,3,11,16]-ET-1 had similar effects. Pre-treatment with 0.1 microgram/ml pertussis toxin (PTX) and chelation of cytosolic Ca2+ did not affect astrocytic stress fiber formation by ET-3. ET-3 stimulated stress fiber formation in stellate astrocytes induced by 50 microM ML-9, 20 microM W-7, and 5 microM cytochalasin B (CB). Cytoplasmic microinjection of C3ADP-ribosyltransferase of C. botulinum (C3 enzyme), which impairs the interaction between rho proteins and the effectors, prevented ET-3-induced stress fiber formation and cytoplasmic expansion in DBcAMP-and CB-treated cells. Effects of ET-1 and sarafotoxin on stress fiber formation were also prevented by C3 enzyme. On the other hand, injection of C3 enzyme did not affect increase in cytoplasmic Ca2+ levels induced by ET-3. These results suggest that rho proteins are involved in the ET receptor-mediated actin re-organization of astrocytes.

Effects of cytochalasins B and D on Staphylococcus aureus adherence to and ingestion by mouse renal cells from primary culture.

Cytochalasin B (CB) and cytochalasin D (CD), inhibitors of microfilament function of host cell, were examined for their effects on Staphylococcus aureus Cowan I adherence to and ingestion by several types of the hyperosmolarity-tolerant (HOT) cells obtained from primary culture of mouse kidney. Staphylococcal adherence to the HOT cells with epithelial appearance was extraordinarily enhanced by the treatment of those cells with both 5 micrograms/ml of CB and CD. In particular, staphylococci adhered to the periphery rather than the center of each cytochalasin-treated cell. Staphylococcal ingestion by all types of the HOT cells was markedly inhibited by CD in spite of the enhanced adherence. Contrary to our expectation, inhibition by CB was incomplete, and the enhanced adherence of staphylococci to CB-treated cells resulted in the enhanced ingestion.

Fluorescence and electron microscopic study of intracellular F-actin in concanavalin A-treated and cytochalasin B-treated Ehrlich ascites tumor cells.

To investigate the involvement of actin filaments in concanavalin A (Con A)-induced cap formation and cytochalasin B (CB)-induced zeiotic knob migration, the distribution of F-actin was studied in Con A-treated and CB-treated Ehrlich ascites tumor cells (EATC) by fluorescence microscopy using heavy meromyosin conjugated with a fluorescent dye, N-(7-dimethylamino-4-methylcoumarinyl) maleimide, (DACM-HMM). In non-treated cells, the diffuse fluorescence of DACM-HMM was observed in the cytoplasm, particularly intensely under the plasma membrane and around the nucleus. In Con A- and CB-treated cells, the fluorescence was seen at Con A-induced-capped and CB-induced-knob-accumulated regions. This fluorescence was more intense in CB-treated cells. To study the actin filaments in these fluorescent regions more clearly, the soluble components of the cells were eliminated by treatment with Triton X-100 or saponin solution containing a low concentration of glutaraldehyde, and the detergent-treated and saponin-treated cells were observed under a transmission electron microscope. Concentrated actin filaments were observed directly beneath the Con A-induced capping area and CB-induced zeiotic knob-accumulation area. The area of concentrated actin filaments appeared to correspond to the electron dense area observed in the identical region in the cells fixed without detergent treatment. More actin filaments were observed in CB-treated cells than in Con A-treated ones.

Site-specific maturation of enveloped viruses in L cells treated with cytochalasin B.

Treatment of infected L cells with 10 micrograms/ml cytochalasin B (CB) was found to promote a rapid relocalization of viral glycoproteins on the cell surface. Whereas the vesicular stomatitis virus G protein and the influenza virus hemagglutinin were uniformly distributed on the surface of untreated cells, in CB-treated cells, they were strikingly concentrated at cell extremities in the regions of clustered blebs. Glycoprotein concentration at cell extremities was accompanied by preferential maturation of virus particles from the same sites; both vesicular stomatitis and influenza viruses budded predominantly from the vicinity of clustered blebs. This effect of CB was completely reversible. Removal of CB from the cell growth medium resulted in a return of viral glycoproteins to the uniform distribution characteristic of untreated cells and to uniform virus budding. The results of this study are interpreted in terms of a model that suggests that preferential budding of viruses from the regions of bleb clusters is due to the concentration of viral glycoproteins at these sites.

Effects of hexose starvation and the role of sialic acid in influenza virus release

We previously reported that growth of influenza virus in the presence of cytochalasin B (CB), a drug that disrupts microfilaments and blocks hexose transport, yields particles with glycoproteins that are heterogeneous and unlabeled by [ 3H]glucosamine. When the virus was grown in glucose-free medium, we observed reduced virus titers similar to those produced by CB. In contrast, treatment of cells with cytochalasin D (CD) and dihydrocytochalasin B (H 2CB), drugs which are known to inhibit microfilament function without affecting hexose transport, did not cause a reduction in virus titers or a change in the electrophoretic mobility of viral glycoproteins. Partial inhibition of glycosylation of viral glycoproteins resulting from either CB-induced inhibition of hexose transport or from glucose starvation resulted in the formation of aggregates of virions on cell surfaces. These aggregates can be dissociated by exogenous neuraminidase. Under these conditions the virions contained a functional hemagglutinin glycoprotein (HA) but an inactive neuraminidase glycoprotein (NA) which was not able to cleave sialic acid, the HA receptor, from viral glycoproteins, or from cellular glycoproteins and glycolipids. Neuraminidase treatment of membrane fractions of CB-treated cells did not cause a shift in the electrophoretic mobility of HA or in the gel elution profile of HA glycopeptides obtained after extensive pronase digestion from HA synthesized in glucose-free medium. These findings suggest that sialic acid is not present on labeled glycoproteins in either of these preparations. We obtained evidence that the sialic acid to which HA binds when NA is inactive is on glycoproteins and glycolipids of cellular origin. Our results support the idea that even when NA is functional, sialylated cellular components impede influenza virus release.

Cell Membrane Polarity in Dissociated Frog Urinary Bladder Epithelial Cells 12.

Localization of cell membrane markers in dissociated frog urinary bladder epithelial cells was studied. The bladder cells began to alter in shape immediately after dissociation and became spherical within 15 min at room temperature. The apical marker, dialyzed iron (DI), was found on the entire surface of dissociated and transformed cells, whereas the basolateral marker, horseradish peroxidase-glutaral-dehyde (HRP-GLA) staining, first gathered at one pole and then became distributed over a larger area. Thus the apparent loss of polarity was not parallel with the true surface uniformity. When bladder cells were dissociated in the presence of cytochalasin B (CB) or 2,4-dinitrophenol (DNP), the transformation was suppressed and the cells maintained structural polarity. DI and HRP-GLA were mostly confined to the original region in CB-treated cells, but both moved to the other membrane region in DNP-treated cells. The results indicated that an aerobic adenosine triphosphate supply, as well as the tight junction, is involved in maintaining regional differentiation of the cell membrane.

The response of chicken embryo dermal fibroblasts to cytochalasin B is altered by Rous sarcoma virus-induced cell transformation.

The drug cytochalasin B (CB), which disrupts the cellular microfilament network, allows the identification of as yet unclassified structural differences between normal and Rous sarcoma virus-transformed chicken embryo fibroblasts. When exposed to CB, normal chick fibroblasts attain an arborized or dendritic morphology. This results as the cytoplasm collapses upon the remaining structural and adhesive components of the cell. Rous sarcoma virus-transformed cells did not form or maintain these dendritic-like processes in the presence of CB and, as a result, rounded up but still remained attached to the substrate. With a temperature-sensitive mutant of Rous sarcoma virus, LA24A, it was possible to show that these effects are completely reversible and dependent on the expression of pp60src. The cytoskeleton in these CB-treated cells was examined by both immunofluorescence and electron microscopy. After exposure to CB, the microfilaments were found to be disrupted similarly throughout both the transformed and the nontransformed cells. In the nontransformed cells arborized by exposure to CB, the extended processes were found to contain intermediate filaments in an unusually high concentration and degree of organization. The distribution of these filaments in the central body of the arborized cells was random. This lower concentration and random distribution was similar to that seen throughout the transformed cells rounded up by exposure to CB. The failure of these transformed cells to arborize in CB indicates that the structural component(s) which is necessary for the formation or maintenance or both of the arborized state is altered by the expression of pp60src.

The response of chicken embryo dermal fibroblasts to cytochalasin B is altered by Rous sarcoma virus-induced cell transformation.

The drug cytochalasin B (CB), which disrupts the cellular microfilament network, allows the identification of as yet unclassified structural differences between normal and Rous sarcoma virus-transformed chicken embryo fibroblasts. When exposed to CB, normal chick fibroblasts attain an arborized or dendritic morphology. This results as the cytoplasm collapses upon the remaining structural and adhesive components of the cell. Rous sarcoma virus-transformed cells did not form or maintain these dendritic-like processes in the presence of CB and, as a result, rounded up but still remained attached to the substrate. With a temperature-sensitive mutant of Rous sarcoma virus, LA24A, it was possible to show that these effects are completely reversible and dependent on the expression of pp60src. The cytoskeleton in these CB-treated cells was examined by both immunofluorescence and electron microscopy. After exposure to CB, the microfilaments were found to be disrupted similarly throughout both the transformed and the nontransformed cells. In the nontransformed cells arborized by exposure to CB, the extended processes were found to contain intermediate filaments in an unusually high concentration and degree of organization. The distribution of these filaments in the central body of the arborized cells was random. This lower concentration and random distribution was similar to that seen throughout the transformed cells rounded up by exposure to CB. The failure of these transformed cells to arborize in CB indicates that the structural component(s) which is necessary for the formation or maintenance or both of the arborized state is altered by the expression of pp60src.

Alteration of a tumor cell distribution pattern by cytochalasin B

Cytochalasin B pretreatment of tumor cells alters the distribution pattern of metastases after i.v. injection. We now have studied Cytochalasin B cell pretreatment affects the i.v. distribution and elimination of 125IUDR-labeled TA3-Ha tumor cells. We found no differences between control and CB-treated cells in their initial distribution. but 4-8 hours after the injection, in the redistribution phase, there were more CB cells than control cells extrapulmonally. Rather than a consequence of CB paralysis, we interpret the results in terms of altered surface properties of CB cells during their recovery.

Effect of cytochalasin B on the maturation of enveloped viruses.

The maturation of two enveloped viruses, influenza and vesicular stomatitis, occurs in cells treated with cytochalasin B. Virions produced in the presence of 50 microgram/ml cytochalasin B (CB) appear to be as infectious as those from control cells, indicating that polymerized actin is not required for the assembly of functional viral components. CB inhibits the release of influenza virus from treated cells, a phenomenon which appears to be a result of the synthesis of an aberrant neuraminidase (NA) glycoprotein; virions grown in CB-treated cells had a 90% reduction in specific enzymatic activity. We found that both influenza viral glycoproteins (NA and Hemagglutinin glycoprotein) had faster electrophoretic mobilities and were more heterogeneous in CB-treated cells as compared with controls. We also observed complete inhibition of incorporation of labeled glucosamine into viral glycoproteins in the presence of the drug. It was of interest that CB-induced inhibition of glycosylation appeared to cause loss of neuraminidase function, whereas hemagglutinating activity was not noticeably impaired. The presence of altered glycoproteins did not significantly diminish the infectivity of either influenza virus or vesicular stomatitis virus. Our results indicate that no step in the maturation of enveloped viruses is dependent upon an intact cytoskeletal network.

Induction of hemoglobin synthesis in dimethylsulfoxide-treated friend erythroleukemic cells grown in the presence of cytochalasin B

The experiments reported here were designed to determine the necessity for nuclear and/or cell division for erythroid differentiation in the presence of the inducer, dimethylsulfoxide (Me 2SO). Murine erythroleukemic cells are induced to synthesize hemoglobin only when the cells are cultured at a density which allows them to replicate in the presence of Me 2SO. Hemoglobin is not detected in the cytoplasm of the cells prior to 48 h. Cells grown in the presence of inducer (Me 2SO)+cytochalasin B (CB) do not divide, but do undergo karyokinesis thereby increasing in size as they become multinucleated. Under these experimental conditions, the CB-treated cells are also capable of synthesizing hemoglobin. Measurements of the rate of hemoglobin synthesis suggest that induced CB-treated cells accumulate more hemoglobin per induced cell than do cells induced by Me 2SO alone. These results indicate that: (a) while cytokinesis is not required to induce hemoglobin synthesis, the ability of the cells to replicate their genomes is critical, and possibly allows Me 2SO to interact with the genome to initiate the erythroid cell program; (b) CB does not alter the time course of hemoglobin synthesis; and (c) the increased levels of hemoglobin in the CB-treated cells is probably related to the increased cell-size mediated by the mold metabolite, and not to the induction of a higher percentage of cells.

Subcellular effect of cytochalasin B and dimethylsulfoxide on Paramecium aurelia.

Paramecium aurelia syngen 4, stock 57 (sensitve) cultivated in Cerophyl infusion were exposed to cytochalasin B (CB) and dimethylsulfoxide (DMSO), the solvent for CB, to distinquish between the effects of these agents on a cellular system. DMSO significantly inhibited survival, fission rate,, [3H]leucine incorporation, and cell size. CB-treated cells generally and slower division and poorer survival rates than cells exposed to the equivalent DMSO concentration, although the [3H]leucine incorporation was generally greater at the lower CB concentrations than for DMSO alone. As seen by electron microscopy and a new glycerination technic for observing polysomes, DMSO caused nuclear (nucleolar, chromatin) abnormalities as well as membrane degradation and polysomal breakdown: CB caused the formation of aberrant membrane structures and ribosomal tetramers, crystals, and tubes.

Response of Cloudman S91 melanoma cells to melanocytestimulating hormone: enhancement by cytochalasin B.

Cloudmann S 91 mouse melanoma cells treated for 5 days with melanocyte-stimulating hormone (MSH), cytochalasin B (CB), or both, exhibited changes in cell volume, population, nucleation, and pigment production. Cells treated with CB or CB in combination with MSH were eight to nine times larger, rounder, multinucleated, and heavily pigmented. CB alone increased melanin and DNA per nucleus threefold. CB in combination with MSH increased melanin per nucleus 30-fold. Data on DNA per nucleus suggest that CB-treated cells remained in the G phase longer than did control cells. MSH alone caused a reduction in cell population and a fourfold increase in melanin per nucleus.

The dynamics of antibody-induced redistribution of viral envelope antigens in the plasma membranes of avian tumour virus-infected chick embryo fibroblasts

Avian tumour virus-infected chick embryo fibroblasts express new antigens, identical with the viral envelope antigens, in their plasma membranes. Electron-microscopic examination of carbon-platinum replicas of cells labelled with haemocyanin-marked antibody has shown the distribution of these antigens to be diffuse over the cell surface with an increased concentration on peripheral cell processes. However, antigen-antibody complexes (AAC), resulting from reaction with specific antibody, may be redistributed into a variety of patterns. Observation of the time course of antibody-induced antigen mobility revealed a rapid and a delayed phase of redistribution. During the rapid phase (10 min or less) some of the antigen-bearing cells reorganized AAC into patches, while the remainder maintained a diffuse distribution. A fraction of the cells with either diffuse or patchy distribution also redistributed AAC into a pattern of 'marginal redistribution (MR)', consisting of linear aggreagation of AAC, at the cell edge. During the 'late' phase of redistribution (after about 20 min), AAC began to condense into one or more foci of coalescence (FC) on each cell. As the number of cells with FC increased with time, the fraction of cells which were labelled decreased. Electron-microscopic observation of thin sections of ferritin-labelled specimens indicated that AAC were lost by endocytosis and that this process was probably related to FC formation. Inhibitors of oxidative phosphorylation, protein synthesis, RNA synthesis, or microtubule assembly had no significant effect on the patterns or the course of redistribution. Iodoacetic acid (IAA), which depletes cellular ATP, and cytochalasin B (CB), which is believed to depolymerize microfilaments, partially inhibited MR and completely prevented FC formation and endocytosis. Paradoxically, IAA or CB-treated cells lost AAC very rapidly by some alternate mechanism not involving FC formation but which may entail a centrifugal migration of complexes to the cell extremities during the process of AAC disposal.