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At least 19 recordsLinked to original sources
PubMed1977

Reversible inhibition of the motility of human spermatozoa by cytochalasin B.

Cytochalasin B inhibits the motility and metabolism of washed human spermatozoa at low concentrations (20 to 200 mum). Spermatozoal motility (primarily the frequency of flagellar contraction) declines slowly after addition of the antibiotic but is not abolished even after treatment for several hours. The addition of caffeine or dibutyrylcyclic adenosine 3' :5'-monophosphate to washed sperm suspensions increases the percentage of motile cells, the frequency of flagellar contraction, and the rate of glycolysis. These effects are blocked by cytochalasin B. However, cytochalasin B-treated spermatozoa regain their responsiveness to these agents when the antibiotic is washed out of supporting media. These effects are discussed in terms of an interaction of cytochalasin B with the sperm plasma membrane.

Bucladesine↗
PubMed1976

Prostaglandin production by methylcholanthrene-transformed mouse BALB/3T3: inhibition by cytochalasin B.

Cytochalasin B inhibits the production of prostaglandins by serum-, thrombin-, and bradykinin-stimulated MC5-5 cells. The serum-stimulated release of arachidonic acid from cellular phospholipids also is inhibited. Cytochalasin B does not affect the cells' prostaglandin synthetase activity when exogenous arachidonic acid is present. Deacylation of phospholipids may be the step affected by cytochalasin B possibly as a result of disruption of microfilament organization. Colchicine and vinblastine, two drugs that can disrupt microtubule organization, do not inhibit prostaglandin production by cells.

Animals↗
PubMed1981

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.

Animals↗
PubMed1972

Regulation of lymphocyte responses in vitro: potentiation and inhibition of rat lymphocyte responses to antigen and mitogens by cytochalasin B.

Cytochalasin B, at concentration between 0.02 and 0.2 mug/ml, was slightly stimulatory to lymph-node cells from normal rats and greatly potentiated their response to phytohemagglutinin and low concentrations of concanavalin A (mitogens for thymus-derived lymphocytes); it also potentiated the response of thymocytes to phytohemagglutinin. The response of lymphnode cells to lipopolysaccharide endotoxin (a mitogen for thymus-independent lymphocytes) was also enhanced, but only at concentrations in the usual inhibitory range, possibly by inhibition of a "suppressor T-cell" response. Sensitized lymphocytes responding to antigen were not stimulated at all, except at a very high cell density, where inhibition of a "suppressor cell" response was also considered likely. At concentrations of 5-10 mug/ml or higher, cytochalasin B inhibited all responses tested.

Animals↗
PubMed1977

The binding sites of cytochalasin D. II. Their relationship to hexose transport and to cytochalasin B.

Cytochalasin B (CB) was able to compete with tritiated cytochalasin D (3H-CD) for binding sites in HEp-2 cells. The pattern of inhibition suggested that CB associates with a low affinity class of CD binding sites. Glucose and maltose did not inhibit binding of 3H-CD to isolated HEp-2 plasma membrane. Inhibition of hexose transport by CD was negligible, but CD did not block the potent inhibition of this transport by CB. These results indicate that CD does not bind to the high affinity CB receptor reportedly associated with the hexose transport system, and that this receptor cannot mediate the morphological effects of CD. Both CD and CB induced contraction-zeoisis in HEp-2 cells; CB was less potent than CD, and their effects appeared to be additive. It was concluded that the high affinity binding sites for CD and CB are different, but that these congeners share a low affinity site. Both high and low affinity sites for CD appear to mediate its morphological effects; only the low affinity class appears to be involved for CB. Possible identification of the common low affinity binding site as actomyosin (detailed in Tannenbaum et al., '77) is further discussed.

Binding Sites↗
PubMed1984

Observations on the effects of cytochalasin B and cytochalasin D on ADP- and chymotrypsin-treated platelets.

Cytochalasin B has been reported to inhibit fibrinogen binding and aggregation of rabbit platelets in response to ADP. The present study was designed to ascertain whether cytochalasins B and D inhibit aggregation by interfering with the exposure of fibrinogen receptors or more directly by inhibiting binding to available receptors. Aspirin-treated, washed, human platelets stimulated with ADP or chymotrypsin were used for these studies. Neither cytochalasin B nor D significantly inhibited the binding of fibrinogen to chymotrypsin-treated platelets when these agents were added to platelet suspensions before (16 +/- 8% (mean +/- SD) inhibition, N = 8), or after (15 +/- 10% inhibition, N = 13) chymotrypsin treatment, i.e., before or after fibrinogen receptor exposure. This apparent lack of cytoskeletal involvement was consistent with the observation that chymotrypsin-treated platelets were unable to retract reptilase-induced fibrin clots, an activity that was restored by adding ADP. In contrast, incubating platelets with either cytochalasin B or D for 30 min before or after stimulation with ADP decreased fibrinogen binding by 42 +/- 16% (N = 13) and 27 +/- 11% (N = 8), respectively, compared to DMSO-treated controls. Platelets stimulated with ADP and incubated with DMSO for 30 min, however, became refractory and aggregated poorly in response to a second dose of ADP. In comparison, platelets stimulated with ADP, but incubated with cytochalasin B or D, aggregated more extensively when stimulated by a second dose of ADP despite diminished fibrinogen binding. The data suggest (1) microfilament polymerization is important not only for the exposure of fibrinogen receptors by ADP, but also for preserving the ability of exposed receptors to bind fibrinogen, (2) exposure of fibrinogen receptors by chymotrypsin is not accompanied by significant cytoskeletal activation, and (3) cytochalasins may impart partial protective effects against the development of ADP-induced refractoriness.

Adenosine Diphosphate↗
PubMed1975

Effects of cytochalasin B on the intrcellular bactericidal activity of human neutrophils.

Cytochalasin B (CB) is known to have some inhibitory effects on cytokinesis, single-cell movement, bacterial uptake by phagocytes, and many other processes. The effects of CB on intraleukocytic bactericidal activities in human leukocytes were studied, and the results were summarized as follows. (i) CB inhibited the early stage of the intracellular bactericidal activity of human leukocytes against Streptococcus pyogenes D58 (group A). The effect was rapidly eliminated by rinsing the CB solution. (ii) In the late stage of the intracellular bactericidal process, however, CB possessed no effect against S. pyogenes D58 (group A) and Staphylococcus aureus 209P. (iii) CB also inhibited the translocation of myeloperoxidase granules to the phagosomes of human neutrophils.

Bacteria↗
PubMed1982

"Pseudo-cap" formation in Ehrlich ascites tumor cells induced by cytochalasin B.

Cytochalasin B (CB) treatment induces or accelerates the capping phenomenon in some cells. In Ehrlich ascites tumor cells (EATC) CB treatment apparently induced the capping of Con A binding sites as observed under a fluorescent microscope. However, electron microscopic examinations revealed that the CB treatment did not induce a rearrangement of Con A binding sites, but rather it only induced a change in cell shape. On the contrary, CB treatment inhibited the capping phenomenon induced by treatment with Con A. Electron microscopic observations may give exact information on the distribution of lectin binding sites.

Animals↗
PubMed1980

Cytochalasin B and the structure of actin gels. II. Further evidence for the splitting of F-actin by cytochalasin B.

Cytochalasin B decreased the flow birefringence and s20,w and increased the extinction angle of actin filaments in salt solutions favoring polymerization of the protein. These changes occurred without a detectable increase in the equilibrium actin monomer concentration determined by a radioassay. These results complement earlier observations indicating that cytochalasin B shortens actin filaments without net depolymerization. Analyzed in terms of Flory's classical network theory, this shortening accounts for the marked effect of cytochalasin B in dissolving the gel structure of F-actin crosslinked by actin-binding protein concentrations near the critical concentration for incipient gelation. Cytochalasin B decreased the annealing rate of low concentrations of actin filament fragments prepared by sonic disruption. The result is consistent with the idea that cytochalasin B binds to the ends of actin filaments, and may explain how cytochalasin B causes filament shortening.

Actins↗
PubMed1991

Enhancement of redirected target cell lysis by cytotoxic T lymphocytes in the presence of cytochalasin B.

The cytochalasins are known secretogogues. Their function as such is examined in light of the granule exocytosis model for lymphocyte-mediated cytotoxicity. Cytochalasin B is found to enhance target cell lysis by cytotoxic T lymphocytes when antibody-coated polystyrene beads are used to bridge the cells. The pattern of lysis is found to be biphasic in its dependence on cytochalasin B. Secretion of the enzyme BLT-esterase from the effector cells parallels the cytochalasin concentration-dependent pattern of lysis. Cytochalasin D is also able to enhance lysis but at concentrations less than cytochalasin B. Cytochalasin B does not inhibit binding of breads to the effector cell. This is shown by the ability of fluorescent beads coated with antibody to bind with an appropriate specificity to cells. These studies indicate that cytochalasin B is not strictly inhibitory for the induction of target cell lysis but can enhance lymphocyte-mediated lysis at low drug concentrations. These results are compatible with the interpretation that target cell lysis is mediated through a secretion process from cytotoxic T lymphocytes.

Actin Cytoskeleton↗
PubMed1973

Selective release of lysosomal hydrolases from phagocytic cells by cytochalasin B.

1. Cytochalasin B (10mug/ml) enhances the release of rabbit polymorphonuclear leucocyte lysosomal acid hydrolases induced by retinol (vitamin A alcohol). 2. This effect is seen at doses of the vitamin that cause selective release of acid hydrolases and those causing more general enzyme release indicated by the loss of lactate dehydrogenase. 3. Cytochalasin B (2-50mug/ml) has no effect on the release of sedimentable acid hydrolases of intact granules obtained from disrupted polymorphonuclear leucocytes. 4. Cytochalasin B (2-10mug/ml) causes a time- and dose-dependent release of mouse peritoneal macrophage acid hydrolases. 5. This effect is selective at all doses of cytochalasin B used, since no release of lactate dehydrogenase, malate dehydrogenase and leucine 2-naphthylamidase was detected. 6. Treatment with cytochalasin B at doses of up to 10mug/ml for as long as 72h did not significantly change the total activities of any of the enzymes measured. 7. The lack of toxicity of cytochalasin B was shown by dye-exclusion tests and its failure to release radioactive colloidal gold stored in secondary lysosomes.

Animals↗
PubMed1976

Inhibition of antigen-induced B lymphocyte activation in vitro by cytochalasin B.

Cytochalasin B (CB), a fungal metabolite which disrupts microfilaments. and will inhibit capping and other events requiring membrane movement, suppressed the production of antibody-forming cells (AFC) in both mouse whole spleen cultures immunized with sheep erythrocytes (SRBC) and in mouse B lymphocyte cultures immunized with the thymic independent antigen DNP-Ficoll (DF). CB at a concentration of 1 mug/ml inhibited the AFC response by more than 90% in spleen cell cultures immunized with SRBC. This inhibition was completely reversible by removal of CB up to 24 hr after the start of culture. Spleen cells cultured in the presence of CB for the first 48 to 72 hr had a decreased AFC response similar to that of cultures in which SRBC had been withheld for thocyte the same period of time. Incubating whole spleen cell or B lymphocyte cultures immunized with DF for as short as 6 hr decreased the AFC response more than 60%. Antibody secretion, cell viability, and antigenicity of the SRBC and DF were not affected by CB. The results of these experiments favor the concept that movement of surface receptors is necessary in activating lymphocytes to differentiate into AFC. The differential response to CB observed in SRBC and DF stimulated cultures makes the technique employed a useful tool to study membrane events occuring between antigen interaction with surface receptor and the initiation of differentiative events.

Animals↗