Cytochalasin B Treatment Research Articles

Gelsolin inhibits autophagy by regulating actin depolymerization in pancreatic ductal epithelial cells in acute pancreatitis

Gelsolin (GSN) can sever actin filaments associated with autophagy. This study investigated how GSN-regulated actin filaments control autophagy in pancreatic ductal epithelial cells (PDECs) in acute pancreatitis (AP). AP was produced in a rat model and PDECs using caerulein (CAE). Rat pancreatic duct tissue and HPDE6-C7 cells were extracted at 6, 12, 24, and 48 h after CAE treatment. HPDE6-C7 cells in the presence of CAE were treated with cytochalasin B (CB) or silenced for GSN for 24 h. Pancreatic histopathology and serum amylase levels were analyzed. Cellular ultrastructure and autophagy in PDECs were observed by transmission electron microscopy after 24 h of CAE treatment. The expression of GSN and autophagy markers LC3, P62, and LAMP2 was evaluated in PDECs by immunohistochemistry and western blotting. Actin filaments were observed microscopically. Amylase levels were highest at 6 h of AP, and pancreatic tissue damage increased over time. Mitochondrial vacuolization and autophagy were observed in PDECs. CAE increased GSN expression in these cells over time, increased the LC3-II/LC3-I ratio and LAMP2 expression at 24 and 6 h of treatment, respectively, and decreased P62 expression at all time points. CB treatment for 24 h decreased the LC3-II/LC3-I ratio and LAMP2 expression, increased P62 levels, but had no impact on GSN expression in CAE-treated PDECs. CAE induced actin depolymerization, and CB potentiated this effect. GSN silencing increased the LC3-II/LC3-I ratio and LAMP2 expression and reduced actin depolymerization in CAE-treated PDECs. GSN may inhibit autophagosome biogenesis and autophagosome-lysosome fusion by increasing actin depolymerization in PDECs in AP.

Mitochondrial aggregation caused by cytochalasin B compromises the efficiency and safety of three-parent embryo.

It is widely accepted that cytochalasin B (CB) is required in enucleation of the oocyte in order to stabilize the cytoplasm. However, CB treatment results in the uneven distribution of mitochondria, with aggregation towards the nucleus, which might compromise the efficiency and safety of a three-parent embryo. Here, we demonstrated that CB treatment affected mitochondrial dynamics, spindle morphology and mitochondrial DNA carryover in a concentration-dependent manner. Our results showed that mouse oocytes treated with over 1 μg/ml CB exhibited a more aggregated pattern of mitochondria and diminished filamentous actin expression. Abnormal fission of mitochondria together with changes in spindle morphology increased as CB concentration escalated. Based on the results of mouse experiments, we further revealed the practical value of these findings in human oocytes. Chip-based digital PCR and pyrosequencing revealed that the mitochondrial carryover in reconstituted human embryos was significantly reduced by modifying the concentration of CB from the standard 5 μg/ml to 1 μg/ml before spindle transfer and pronuclear transfer. In conclusion, our findings provide an optimal manipulation for improving the efficiency and safety of mitochondrial replacement therapy.

Cytochalasin B Modulates Nanomechanical Patterning and Fate in Human Adipose-Derived Stem Cells.

Cytoskeletal proteins provide architectural and signaling cues within cells. They are able to reorganize themselves in response to mechanical forces, converting the stimuli received into specific cellular responses. Thus, the cytoskeleton influences cell shape, proliferation, and even differentiation. In particular, the cytoskeleton affects the fate of mesenchymal stem cells (MSCs), which are highly attractive candidates for cell therapy approaches due to their capacity for self-renewal and multi-lineage differentiation. Cytochalasin B (CB), a cyto-permeable mycotoxin, is able to inhibit the formation of actin microfilaments, resulting in direct effects on cell biological properties. Here, we investigated for the first time the effects of different concentrations of CB (0.1–10 μM) on human adipose-derived stem cells (hASCs) both after 24 h (h) of CB treatment and 24 h after CB wash-out. CB influenced the metabolism, proliferation, and morphology of hASCs in a dose-dependent manner, in association with progressive disorganization of actin microfilaments. Furthermore, the removal of CB highlighted the ability of cells to restore their cytoskeletal organization. Finally, atomic force microscopy (AFM) revealed that cytoskeletal changes induced by CB modulated the viscoelastic properties of hASCs, influencing their stiffness and viscosity, thereby affecting adipogenic fate.

Cytochalasin B Treatment and Osmotic Pressure Enhance the Production of Extracellular Vesicles (EVs) with Improved Drug Loading Capacity.

Extracellular vesicles (EVs) have been highlighted as novel drug carriers due to their unique structural properties and intrinsic features, including high stability, biocompatibility, and cell-targeting properties. Although many efforts have been made to harness these features to develop a clinically effective EV-based therapeutic system, the clinical translation of EV-based nano-drugs is hindered by their low yield and loading capacity. Herein, we present an engineering strategy that enables upscaled EV production with increased loading capacity through the secretion of EVs from cells via cytochalasin-B (CB) treatment and reduction of EV intravesicular contents through hypo-osmotic stimulation. CB (10 µg/mL) promotes cells to extrude EVs, producing ~three-fold more particles than through natural EV secretion. When CB is induced in hypotonic conditions (223 mOsm/kg), the produced EVs (hypo-CIMVs) exhibit ~68% less intravesicular protein, giving 3.4-fold enhanced drug loading capacity compared to naturally secreted EVs. By loading doxorubicin (DOX) into hypo-CIMVs, we found that hypo-CIMVs efficiently deliver their drug cargos to their target and induce up to ~1.5-fold more cell death than the free DOX. Thus, our EV engineering offers the potential for leveraging EVs as an effective drug delivery vehicle for cancer treatment.

Autotriploid and allotriploid abalone larvae (Haliotis discus hannai and H. discus hannai ♀ × Haliotis fulgens ♂) produced by two chemical methods

Two types of abalone larvae, Haliotis discus hannai and H. discus hannai ♀ × Haliotis fulgens ♂, were produced by inhibiting polar body II (PB2) via treatment with two chemicals: cytochalasin-B (CB) and 6-dimethylaminopurine (6-DMAP). After 70 % of the fertilized eggs released polar body I, the zygotes and hybrid zygotes were treated with four CB (1, 1.25, 1.5, and 1.75 mg L−1) or 6-DMAP concentrations (10, 20, 30, and 40 mg L−1) for 10, 15, and 20 min. The hatching indices of embryo, including cleavage and hatching of fertilized eggs, were evaluated, and composite ploidy was determined using flow cytometry at 24 h after fertilization. Our results showed that hatching rate and triploid rate of autotriploid and allotriploid larvae were significantly affected by the CB and 6-DMAP concentration and treatment duration, respectively (P < 0.05), except for the effect of 6-DMAP treatment duration on allotriploid and triploid rate of autotriploid larvae (P> 0.05). Higher triploid rate induced a low hatching rate and vice versa. Combining both high rates of triploidy and reasonable hatching, the optimal treatment combination for triploid induction in autotriploid abalone was 1.75 mg L−1 CB for 15 min and 40 mg L−1 6-DMAP for 10 min, and optimization of triploidy induction in allotriploid abalone was achieved using CB (1.75 mg L−1) for 15 min and 6-DMAP (30 mg L−1) for 20 min. The hatching rate and triploid rate were 73.11–85.20 % and 91.66–100.00 %, respectively. This study confirmed the improvements in the effectiveness of 6-DMAP and CB in inducing autotriploid larvae in H. discus hannai and established an improved procedure for inducing triploidy in hybrid of H. discus hannai female and H. fulgens male using chemical methods. These methods will likely be useful for production of triploid strains in abalone aquaculture.

Melanin Distribution in Human Skin: Influence of Cytoskeletal, Polarity, and Centrosome-Related Machinery of Stratum basale Keratinocytes.

Melanin granules cluster within supra-nuclear caps in basal keratinocytes (KCs) of the human epidermis, where they protect KC genomic DNA against ultraviolet radiation (UVR) damage. While much is known about melanogenesis in melanocytes (MCs) and a moderate amount about melanin transfer from MC to KC, we know little about the fate of melanin once inside KCs. We recently reported that melanin fate in progenitor KCs is regulated by rare asymmetric organelle movement during mitosis. Here, we explore the role of actin, microtubules, and centrosome-associated machinery in distributing melanin within KCs. Short-term cultures of human skin explants were treated with cytochalasin-B and nocodazole to target actin filaments and microtubules, respectively. Treatment effects on melanin distribution were assessed by the Warthin–Starry stain, on centrosome-associated proteins by immunofluorescence microscopy, and on co-localisation with melanin granules by brightfield microscopy. Cytochalasin-B treatment disassembled supra-nuclear melanin caps, while nocodazole treatment moved melanin from the apical to basal KC domain. Centrosome and centriolar satellite-associated proteins showed a high degree of co-localisation with melanin. Thus, once melanin granules are transferred to KCs, their preferred apical distribution appears to be facilitated by coordinated movement of centrosomes and centriolar satellites. This mechanism may control melanin’s strategic position within UVR-exposed KCs.

Calcium-Free and Cytochalasin B Treatment Inhibits Blastomere Fusion in 2-Cell Stage Embryos for the Generation of Floxed Mice via Sequential Electroporation.

The generation of conditional knockout mice using the Cre-loxP system is advantageous for the functional analysis of genes. Flanked by two loxP sites (floxed) mice can be directly obtained from fertilized eggs by the CRISPR/Cas9 genome editing system. We previously reported that sequential knock-in (KI) of each loxP site by electroporation (EP) at the 1- and 2-cell embryonic stages increases the number of mice with floxed alleles compared with simultaneous KI. However, EP at the 2-cell stage frequently induced blastomere fusion. These fused embryos cannot develop to term because they are tetraploidized. In this study, we examined the following three conditions to inhibit blastomere fusion by EP at the 2-cell stage: (1) hypertonic treatment, (2) Calcium (Ca2+)-free treatment, and (3) actin polymerization inhibition. Hypertonic treatment of 2-cell stage embryos prevented blastomere fusion and facilitated blastocyst development; however, KI efficiency was decreased. Ca2+-free treatment and actin polymerization inhibition by cytochalasin B (CB) reduced fusion rate, and did not have negative effects on development and KI efficiency. These results suggest that Ca2+-free and CB treatment at the 2-cell stage is effective to generate floxed mice in combination with a sequential EP method.

Effect of Cytochalasin B Treatment on the Improvement of Survival Rate in Vitrified Pig Oocyte.

To improve survival rates of vitrified pig oocytes, the treatment of cytoskeletal stabilizer on an appropriate time is one of the possible approaches. However, the exact treatment timing and effect of cytoskeletal stabilizer such as cytochalasin B (CB) is not well known during oocyte vitrification procedures. Thus, the present study was conducted to determine optimal treatment timing of CB during vitrification and warming procedures. In experiment 1, the survival rates of the post-warming pig oocytes were analyzed by fluorescein diacetate (FDA) assays with 4 classifications. In results, post-warming oocytes showed significantly (p<0.05) decreased number of alive oocytes (31.8% vs. 86.4%) compared to fresh control. In detail, the significant difference (p<0.05) was found only in strong fluorescence (18.2% vs. 70.5%) not in intermediate fluorescence groups (13.6% vs. 15.9%). In experiment 2, CB was treated before (CB-Vitri) and after (Vitri-CB) vitrification. In results, group of Vitri-CB showed significantly (p<0.05) higher (91.6%) survival rates compared to group of CB-Vitri (83.7%), significantly (p<0.05) and comparable with group of Vitri Control (88.7%) by morphological inspection. In FDA assay results, group of Vitri-CB showed significantly (p<0.05) higher (44.2%) survival rates compared to groups of CB-Vitri (36.7%) and Vitri Control (35.1%). In conclusion, the increased survival rates of post-warming pig oocyte treated with Vitri-CB method are firstly described here. The main finding of present study is that the CB treatment during recovery could be helpful to refresh the post-warming pig oocyte resulting its improved survival rates.

Cytochalasin B Treatment of Apple (Malus pumila Mill.) Pollen Tubes Alters the Cytoplasmic Calcium Gradient and Causes Major Changes in the Cell Wall Components

It is well established that the actin cytoskeleton is absolutely essential to pollen germination and tube growth. In this study we investigated the effects of cytochalasin B (CB), which affects actin polymerization by binding to the barbed end of actin filaments, on apple (Malus pumila Mill.) pollen tube growth. Results showed that CB altered the morphology of pollen tubes, which had a larger diameter than control tubes beside inhibiting pollen germination and tube growth. Meantime CB also caused an abnormal distribution of actin filaments in the shank of the treated pollen tubes. Fluo-3/AM labeling indicated that the gradient of cytosolic calcium ([Ca2+]c) in the pollen tube tip was abolished by exposure to CB, which induced a much stronger signal in the cytoplasm. Cellulose and callose distribution in the tube apex changed due to the CB treatment. Immunolabeling with different pectin and arabinogalactan protein (AGP) antibodies illustrated that CB induced an accumulation of pectins and AGPs in the tube cytoplasm and apex wall. The above results were further supported by Fourier-transform infrared (FTIR) analysis. The results suggest the disruption of actin can result in abnormal growth by disturbing the [Ca2+]c gradient and the distribution of cell wall components at the pollen tube apex.

Effects of anticancer drugs on glia–glioma brain tumor model characterized by acoustic impedance microscopy

An ultrasonic microscope is a useful tool for observing living tissue without chemical fixation or histochemical processing. Two-dimensional (2D) acoustic impedance microscopy developed in our previous study for living cell observation was employed to visualize intracellular changes. We proposed a brain tumor model by cocultivating rat glial cells and C6 gliomas to quantitatively analyze the effects of two types of anticancer drugs, cytochalasin B (CyB) and temozolomide (TMZ), when they were applied. We reported that CyB treatment (25 µg/ml, T = 90 min) significantly reduced the acoustic impedance of gliomas and has little effect on glial cells. Meanwhile, TMZ treatment (2 mg/ml, T = 90 min) impacted both cells equally, in which both cells’ acoustic impedances were decreased. As CyB targets the actin filament polymerization of the cells, we have concluded that the decrease in acoustic impedance was in fact due to actin filament depolymerization and the data can be quantitatively assessed for future studies in novel drug development.

Effects of cytochalasin B on DNA methylation and histone modification in parthenogenetically activated porcine embryos.

DNA methylation and histone modification play important roles in the development of mammalian embryos. Cytochalasin B (CB) is an actin polymerization inhibitor that can significantly affect cell activity and is often used in studies concerning cytology. In recent years, CB is also commonly being used in in vitro experiments on mammalian embryos, but few studies have addressed the effect of CB on the epigenetic modification of embryonic development, and the mechanism underlying this process is also unknown. This study was conducted to investigate the effects of CB on DNA methylation and histone modification in the development of parthenogenetically activated porcine embryos. Treatment with 5 μg/mL CB for 4 h significantly increased the cleavage rate, blastocyst rate and total cell number of blastocysts. However, the percentage of apoptotic cells and the expression levels of the apoptosis-related genes BCL-XL, BAX and CASP3 were significantly decreased. Treatment with CB significantly decreased the expression levels of DNMT1, DNMT3a, DNMT3b, HAT1 and HDAC1 at the pronuclear stage and promoted the conversion of 5-methylcytosine (5mC) into 5-hydroxymethylcytosine (5hmC). After CB treatment, the level of AcH3K9 was upregulated and the level of H3K9me3 was downregulated. When combined with Scriptaid and 5-Aza-Cdr, CB further improved the embryonic development competence and decreased the expression of BCL-XL, BAX and CASP3 In conclusion, these results suggest that CB could improve embryonic development and the quality of the blastocyst by improving the epigenetic modification during the development of parthenogenetically activated embryos.

Distinctive Effects of Cytochalasin B in Chick Primary Myoblasts and Fibroblasts.

Actin-based structures play fundamental roles in cellular functions. However it remains controversial how cells cope with the absence of F-actin structures. This report focuses on short- and long-term effects of cytochalasin B (CB) on actin-complexes in fibroblasts and myoblasts. Thirty min of CB treatment dispersed subplasma actin cortices, lamellipodia, ruffled membranes, stress fibers and adhesion plaques into actin patches in fibroblasts and muscle cells. In contrast, 72 hrs CB treatment showed distinct morphological effects. Fibroblasts became giant multinucleated-finger shaped with 5 to 10 protrusions, 3–8 μm in width, and >200 μm in length. They lacked cortical actin, stress fibers, adhesion plaques and ruffled membranes but contained immense lamelliopodia with abnormal adhesion plaque protein complexes. Muscle cells transformed into multinucleated globular-shaped but contained normal I-Z-I and A-bands, indicating that CB did not interfere with the assembly of myofibrils. Within 30 min after CB removal, finger-shaped fibroblasts returned to their original shape and actin-containing structures rapidly reappeared, whereas muscle cells respond slowly to form elongated myotubes following CB washout. The capacity to grow, complete several nuclear cycles, assemble intermediate filaments and microtubules without a morphologically recognizable actin cytoskeleton raises interesting issues related to the role of the actin compartments in eukaryotic cells.

Stability of the cytoskeleton of matured buffalo oocytes pretreated with cytochalasin B prior to vitrification

Stabilizing the cytoskeleton system during vitrification can improve the post-thaw survival and development of vitrified oocytes. The cytoskeleton stabilizer cytochalasin B (CB) has been used in cryopreservation to improve the developmental competence of vitrified oocytes. To assess the effect of pretreating matured buffalo oocytes with CB before vitrification, we applied 0, 4, 8, or 12 μg/mL CB for 30 min. The optimum concentration of CB treatment (8 μg/mL for 30 min) was then used to evaluate the distribution of microtubules and microfilaments, the expression of the cytoskeleton proteins actin and tubulin, and the developmental potential of matured oocytes that were vitrified-warmed by the Cryotop method. Western blotting demonstrated that vitrification significantly decreased tubulin expression, but that the decrease was attenuated for oocytes pretreated with 8 μg/mL CB before vitrification. After warming and intracytoplasmic sperm injection, oocytes that were pretreated with 8 μg/mL CB before vitrification yielded significantly higher 8-cell and blastocyst rates than those that were vitrified without CB pretreatment. The values for the vitrified groups in all experiments were significantly lower (P < 0.01) than those of the control groups. In conclusion, pretreatment with 8 μg/mL CB for 30 min significantly improves the cytoskeletal structure, expression of tubulin, and development capacity of vitrified matured buffalo oocytes.

Substrate-induced PC12 cell differentiation without filopodial, lamellipodial activity or NGF stimulationa.

Nanoscale gradients in energy of adhesion are physical cues from the extracellular environment that can significantly affect cell functions and enhance the neuronal differentiation of PC12 cells. How such surface effects can trigger differentiation and initiate neurite outgrowth, remains to be elucidated. Here we used surface modification, atomic force microscopy and immunofluorescence to analyze PC12 cells. We studied the kinetics of neurites growth under cytochalasin-B treatment, known as an inhibitor of actin polymerization. We found that neither filopodia nor lamellipodia are involved in detecting the surface effects that induce the differentiation of PC12 cells. This finding suggests that the solution to this problem lies beyond identifying a precise cytoskeleton-associated cell-substrate intermediate. Thus, a more comprehensive model is probably required to identify the mechanism by which cell-substrate interactions are eventually translated into a differentiation signal.

Cytochalasin B inhibits the proliferation of human glioma U251 cells through cell cycle arrest and apoptosis.

Cytochalasin B (CB) is known to inhibit a number of cancer types, but its effects on gliomas are unknown. We examined the in vitro effects of CB on the proliferation of human glioma U251 cells, as well as determined its mechanism of action. Cell proliferation was determined using CCK-8. The effect of CB on U251 cell morphology was observed under a transmission electron microscope. Cell cycle distribution was assessed using propidium iodine and Giemsa staining, and cell apoptosis was determined by annexin V-fluorescein isothiocyanate/propidium iodide. Cell cycle-related proteins were determined by Western blot. CB effectively inhibited U251 cell proliferation in a dose- and time-dependent manner. The 24, 48, 72, and 96 h IC50 values were 6.41 x 10(-2), 9.76 x 10(-4), 2.57 x 10(-5), and 2.08 x 10(-5) M, respectively. CB increased the proportion of cells in the G2/M phase in a dose-dependent manner, thus increasing the mitotic index and decreasing cdc2 and cyclin B1 protein levels. CB induced morphological changes in the cytoskeleton. Additionally, 10(-5) M CB induced apoptosis in 23.4 ± 0.5% of U251 cells (P < 0.05 vs control group). Caspase-3, -8, and -9 activities were increased after CB treatment. CB inhibited U251 glioma cell proliferation by damaging the microfilament structure. CB also induced glioma cell apoptosis, suggesting that it may be an effective therapeutic agent against gliomas.

Increased cleavage rate of human nuclear transfer embryos after 5-aza-2′-deoxycytidine treatment

As an abundant source that involves fewer ethical considerations, human abnormally fertilized zygotes are superior to oocytes as therapeutic cloning recipients of nuclear transfer. However, more effective manipulation conditions should be developed for somatic cell nuclear transfer (SCNT) studies using human abnormally fertilized zygotes as recipients. The present study found that the use of cytochalasin B was not necessary for, and even harmful to, the enucleation of human zygotes. This study also decreased the DNA methylation levels in reconstructed embryos using a DNA methyltransferase inhibitor, 5-aza-2′-deoxycytidine (5-aza-dC), in an attempt to correct the abnormalities in DNA methylation that might play an important role in the failure of embryo development. After 5-aza-dC treatment and nuclear transfer (NT-Aza group), 32.7% of reconstructed embryos developed to the 8-cell stage, which is a much higher percentage than that of the nuclear transfer only (NT) group (11.1%). The DNA methylation level in the NT-Aza group was significantly lower than that of the NT group, as determined by 5-methylcytosine immunodetection. Based on the present results, this study recommends performing the enucleation procedure without cytochalasin B treatment and using 5-aza-dC in the culture of reconstructed embryos in human SCNT studies.As an abundant source that involves fewer ethical considerations, human abnormally fertilized zygotes are superior to oocytes as therapeutic cloning recipients of nuclear transfer. However, more effective manipulation conditions should be developed for somatic cell nuclear transfer (SCNT) studies using human abnormally fertilized zygotes as recipients. In the present study, the effects of cytochalasin B (CB) treatment on the survival rate of the manipulated zygotes and the effects of 5-aza-2′-deoxycytidine (5-aza-dC) treatment on the cleavage rate of the reconstructed embryos were observed. Human polyspermic zygotes were enucleated in metaphase with or without CB treatment and injected with human cumulus cells. The reconstructed embryos were cultured in medium supplemented with or without 5-aza-dC for developmental potential comparison. The DNA methylation levels of the embryos were determined using 5-methylcytosine immunodetection. CB treatment lowered the survival rate of manipulated zygotes. After the 5-aza-dC treatment (NT-Aza group), 32.7% of the reconstructed embryos developed to the 8-cell stage, a much higher percentage than that of the nuclear transfer only (NT) group (11.1%). The DNA methylation level in the NT-Aza group was significantly lower than that in the NT group. Based on the present results, we recommend performing the enucleation procedure without CB treatment and using 5-aza-dC in the culture of reconstructed embryos in human SCNT studies.

Development of a novel liquid crystal based cell traction force transducer system

Keratinocyte traction forces play a crucial role in wound healing. The aim of this study was to develop a novel cell traction force (CTF) transducer system based on cholesteryl ester liquid crystals (LC). Keratinocytes cultured on LC induced linear and isolated deformation lines in the LC surface. As suggested by the fluorescence staining, the deformation lines appeared to correlate with the forces generated by the contraction of circumferential actin filaments which were transmitted to the LC surface via the focal adhesions. Due to the linear viscoelastic behavior of the LC, Hooke's equation was used to quantify the CTFs by associating Young's modulus of LC to the cell induced stresses and biaxial strain in forming the LC deformation. Young's modulus of the LC was profiled by using spherical indentation and determined at approximately 87.1±17.2kPa. A new technique involving cytochalasin-B treatment was used to disrupt the intracellular force generating actin fibers, and consequently the biaxial strain in the LC induced by the cells was determined. Due to the improved sensitivity and spatial resolution (∼1μm) of the LC based CTF transducer, a wide range of CTFs was determined (10–120nN). These were found to be linearly proportional to the length of the deformations. The linear relationship of CTF-deformations was then applied in a bespoke CTF mapping software to estimate CTFs and to map CTF fields. The generated CTF map highlighted distinct distributions and different magnitude of CTFs were revealed for polarized and non-polarized keratinocytes.

Cytochalasin B treatment of mouse oocytes during intracytoplasmic sperm injection (ICSI) increases embryo survival without impairment of development

Intracytoplasmic sperm injection (ICSI) is a technique commonly used in clinical and research settings. In mouse oocytes, conventional ICSI has a poor survival rate caused by a high level of lysis. Cytochalasin B (CB) is a toxic microfilament-inhibiting agent that is known to relax the cytoskeleton and enhance the flexibility of oocytes. CB has been used widely in nuclear transfer experiments to improve the success rate of the micromanipulation, however information describing the use of CB in ICSI is limited. Here, we demonstrated that the addition of 5 μg/ml CB to the manipulation medium of ICSI procedure significantly improved the survival rate of the ICSI embryos (80.74% vs. 89.50%, p < 0.05), and that there was no harm for the in vitro or in vivo development. The birth rates and birth weights were not significantly different between the CB-treated and -untreated groups. Interestingly, the microfilaments of the ICSI embryos were almost undetectable immediately after CB treatment; however, they gradually re-appeared and had fully recovered to the normal level 2 h later. Moreover, CB did not disturb spindle rotation, second polar body formation or pronuclei migration, and had no effect on the microtubules. We thus conclude that ICSI manipulation in CB-containing medium results in significantly improved survival rate of mouse ICSI embryos, and that short-term treatment with CB during ICSI manipulation does not have adverse effects on the development of ICSI embryos.

Effects of interval between fusion and activation, cytochalasin B treatment, and number of transferred embryos, on cloning efficiency in goats

To improve the efficiency of somatic cell nuclear transfer (SCNT) in goats, we evaluated the effects of the interval between fusion and activation (1 to 5 h), cytochalasin B (CB) treatment after electrofusion, and the number of transferred embryos on the in vivo and in vitro development of cloned caprine embryos. The majority of the reconstructed embryos had condensed chromosomes and metaphase-like chromosomes at 2 and 3 h after fusion; cleavage and blastocyst rates from those two groups were higher (P < 0.05) than those of embryos activated 1, 4, or 5 h after fusion. Treatment with CB between fusion and activation improved in vitro and in vivo development of nuclear transfer (NT) goat embryos by reducing the fragmentation rate (P < 0.05). Although there were no significant differences in NT efficiency, pregnancy rate and kids born per recipient were increased by transfer of 20 or 30 embryos per recipient compared with 10 embryos. We concluded that CB treatment for 2 to 3 h between fusion and activation was an efficient method for generating cloned goats by somatic cell NT. In addition, increasing the number of embryos transferred to each recipient resulted in more live offspring from fewer recipients.

Enucleation of Demecolcine-Treated Bovine Oocytes in Cytochalasin-Free Medium: Mechanism Investigation and Practical Improvement

Demecolcine-assisted/induced enucleation has been used in nuclear transfer cloning procedures for many species, yet its mechanism of action remains unclear. Primarily because oocytoplasm protrusion induced by demecolcine is inhibited by the presence of cytochalasin, its use has had limited application. In this experiment, we investigated the microtubule and microfilament alterations in bovine oocytes after demecolcine and/or cytochalasin B (CB) treatments by immunocytochemical staining. We also examined mechanical enucleation of demecolcine-treated oocytes in cytochalasin-free medium. The results showed that demecolcine-treatment disrupts the balance between microtubule/microfilament interactions primarily by deleting microtubules and with little effect on the microfilaments that we believe accounts for the membrane protrusion. The CB treatment reduced the amount of microfilaments but had little effect on the microtubules. Most demecolcine-induced membrane protrusions disappeared when exposed to CB. Western blotting showed that CB treatment increases G-actin, which indicates a decrease in the microfilaments. High oocyte enucleation, survival, and developmental rates occurred when demecolcine-assisted enucleation was carried out in a CB-free solution. Higher blastocyst development rates and blastocyst cell numbers were achieved compared to control, indicating that CB is not necessary in the enucleation procedure of bovine oocytes. This study provides a clearer understanding of the mechanism for the demecolcine-induced oocyte membrane protrusion, and substantiates the practical use of demecolcine-assisted enucleation in a CB-free environment.