ABSTRACT
Collective cell migration plays crucial roles in tissue remodeling, wound healing, and cancer cell invasion. However, its underlying mechanism remains unknown. Previously, we showed that the RhoA-targeting guanine nucleotide exchange factor Solo (ARHGEF40) is required for tensile force-induced RhoA activation and proper organization of keratin-8/keratin-18 (K8/K18) networks. Here, we demonstrate that Solo knockdown significantly increases the rate at which Madin-Darby canine kidney cells collectively migrate on collagen gels. However, it has no apparent effect on the migratory speed of solitary cultured cells. Therefore, Solo decelerates collective cell migration. Moreover, Solo localized to the anteroposterior regions of cell-cell contact sites in collectively migrating cells and was required for the local accumulation of K8/K18 filaments in the forward areas of the cells. Partial Rho-associated protein kinase (ROCK) inhibition or K18 or plakoglobin knockdown also increased collective cell migration velocity. These results suggest that Solo acts as a brake for collective cell migration by generating pullback force at cell-cell contact sites via the RhoA-ROCK pathway. It may also promote the formation of desmosomal cell-cell junctions related to K8/K18 filaments and plakoglobin.
Subject(s)
Cell Movement/physiology , Signal Transduction/physiology , rho GTP-Binding Proteins/physiology , rho-Associated Kinases/physiology , Amides/pharmacology , Animals , Cell Polarity , Collagen , Cytoskeleton/physiology , Desmosomes/physiology , Dogs , Gels , Gene Knockdown Techniques , Keratin-18/antagonists & inhibitors , Keratin-18/genetics , Keratin-18/physiology , Keratin-8/antagonists & inhibitors , Keratin-8/genetics , Keratin-8/physiology , Madin Darby Canine Kidney Cells , Pyridines/pharmacology , RNA Interference , RNA, Small Interfering/genetics , RNA, Small Interfering/pharmacology , Stress, Mechanical , Time-Lapse Imaging , gamma Catenin/antagonists & inhibitors , gamma Catenin/genetics , gamma Catenin/physiology , rac1 GTP-Binding Protein/physiology , rho GTP-Binding Proteins/antagonists & inhibitors , rhoA GTP-Binding Protein/physiologyABSTRACT
In-situ transmission electron microscopy experiments are of great interest to nanoscience and nanotechnology. However, it is known that the electron beam can have a significant impact on the structure of the sample which makes it important to carefully interpret in-situ data. In this work, we studied the thermal stability of CTAB-stabilized gold nanorods under different gaseous environments in an environmental transmission electron microscope and compared the outcome to ex-situ heating experiments. We observed a remarkable influence of the electron beam: While the nanorods were stable under inert conditions when exposed to the electron beam even at 400°C, the same nanorods reshaped at temperatures as low as 100°C under ex-situ conditions. We ascribe the stabilizing effect to the transformation of the CTAB bi-layer into a thin carbon layer under electron beam irradiation, preventing the nanorods from deforming. When exposed to an oxidizing environment in the environmental transmission electron microscope, this carbon layer was gradually removed and the gold atoms became mobile allowing for the deformation of the rod. This work highlights the importance of understanding the phenomena taking place under electron beam irradiation, which can greatly affect in-situ experiments and conclusions drawn from these. It stresses that in-situ electron microscopy data, taken on measuring the temperature dependence of nanoparticle properties, should be carefully assessed and accompanied by ex-situ experiments if possible.
ABSTRACT
OBJECTIVE: We studied the effect of lamotrigine (LTG) in children/adults with severe mental retardation and behavioral problems. METHODS: We studied 10 cases with the following conditions: (1) severe or profound mental retardation, (2) various behavioral problems and troubles in daily life, (3) insufficient effects or side effects from antipsychotic drugs, (4) ongoing epileptic seizures or EEG indications of epilepsy, (5) no previous LTG administration, (6) the ability to provide informed consent. We began administering small doses and increased to a maximum dose of LTG in 50 mg/day. We determined the improvement of behavioral problems based on family and patient interviews or our medical examinations. RESULTS: Treatment (still ongoing) has resulted in 7 of the 10 cases showing effects of LTG. Also, 2 of the remaining 3 cases have discontinued medication due to evident changes of mood. Eight cases have showed effects with doses of 10 mg or less per day. We encountered one adult subject who seems to have realized the neuropsychological effect on recognition impairment. We speculated that this patient came to read other people's emotional changes and expected to be either criticized or directed. CONCLUSIONS: Small doses of LTG appear to improve behavioral problems in children/adults with severe mental retardation.
