Maxillary first premolars: I. Morphology of the apical constriction

Dishevelled-Associating Protein with a high frequency of LEucines (DAPLE) belongs to a group of unconventional activators of heterotrimeric G-proteins that are cytoplasmic factors rather than membrane proteins of the G-protein–coupled receptor superfamily. During neurulation, DAPLE localizes to apical junctions of neuroepithelial cells and promotes apical cell constriction via G-protein activation. While junctional localization of DAPLE is necessary for this function, the factors it associates with at apical junctions or how they contribute to DAPLE-mediated apical constriction are unknown. MPDZ is a multi-PDZ (PSD95/DLG1/ZO-1) domain scaffold present at apical cell junctions whose mutation in humans is linked to nonsyndromic congenital hydrocephalus (NSCH). DAPLE contains a PDZ-binding motif (PBM) and is also mutated in human NSCH, so we investigated the functional relationship between both proteins. DAPLE colocalized with MPDZ at apical cell junctions and bound directly to the PDZ3 domain of MPDZ via its PBM. Much like DAPLE, MPDZ is induced during neurulation in Xenopus and is required for apical constriction of neuroepithelial cells and subsequent neural plate bending. MPDZ depletion also blunted DAPLE-mediated apical constriction of cultured cells. These results show that DAPLE and MPDZ, two factors genetically linked to NSCH, function as cooperative partners at apical junctions and are required for proper tissue remodeling during early stages of neurodevelopment.

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Ex vivo accuracy of three electronic apex locators using different apical file sizes

Brazilian Dental Journal ◽

10.1590/s0103-64402012000300003 ◽

2012 ◽

Vol 23 (3) ◽

pp. 199-204 ◽

Cited By ~ 15

Author(s):

Bruno Carvalho de Vasconcelos ◽

Leonardo de Alencar Matos ◽

Elilton Cavalcante Pinheiro-Júnior ◽

Antônio Sérgio Teixeira de Menezes ◽

Nilton Vivacqua-Gomes

Keyword(s):

Root Canal ◽

Ex Vivo ◽

Chi Square ◽

Apical Constriction ◽

Visual Measurement ◽

Chi Square Test ◽

The Mean

This study evaluated the accuracy of three electronic apex locators (Root ZX, Novapex, and Justy II) in root canal length determinations using different apical file sizes, considering the apical constriction (AC) and the major foramen (MF) as anatomic references. The diameter of the apical foramina of 40 single-rooted teeth was determined by direct visual measurement and the master apical file was established. Electronic measurements were then performed using 3 instruments: the selected master apical file (adjusted file), one size smaller (intermediate file), and two sizes smaller (misfit file). The distances from the tip of files fixed in the canals to the MF and to the AC were measured digitally. Precision at AC and at MF for the misfit, intermediate and adjusted apical files was as follows: 80%/88%/83% and 78%/83%/95% (Root ZX); 80%/85%/80% and 68%/73%/73% (Novapex); and 78%/80%/78% and 65%/78%/70% (Justy II). Considering the mean discrepancies, statistically significant differences were found only for the adjusted file at MF, with Root ZX presenting the best results at MF. The chi-square test showed significant differences between the acceptable measurements at AC and at MF for the Justy II and Novapex (± 0.5 mm) regardless of file adjustment. Under the conditions of the present study, all devices provided acceptable electronic measurements regardless of file adjustment, except for Root ZX which had its performance improved significantly when the precisely fit apical file was used. Justy II and Novapex provided electronic measurements nearest to the AC.

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Mechanical competition alters the cellular interpretation of an endogenous genetic program

The Journal of Cell Biology ◽

10.1083/jcb.202104107 ◽

2021 ◽

Vol 220 (11) ◽

Author(s):

Sourabh Bhide ◽

Denisa Gombalova ◽

Gregor Mönke ◽

Johannes Stegmaier ◽

Valentyna Zinchenko ◽

...

Keyword(s):

Genetic Program ◽

Cell Behavior ◽

Mechanical Stimuli ◽

Apical Constriction ◽

Actin Reorganization ◽

Ductile Materials ◽

Nonlinear Mechanical ◽

A Cell ◽

Contractile Forces ◽

Strain Responses

The intrinsic genetic program of a cell is not sufficient to explain all of the cell’s activities. External mechanical stimuli are increasingly recognized as determinants of cell behavior. In the epithelial folding event that constitutes the beginning of gastrulation in Drosophila, the genetic program of the future mesoderm leads to the establishment of a contractile actomyosin network that triggers apical constriction of cells and thereby tissue folding. However, some cells do not constrict but instead stretch, even though they share the same genetic program as their constricting neighbors. We show here that tissue-wide interactions force these cells to expand even when an otherwise sufficient amount of apical, active actomyosin is present. Models based on contractile forces and linear stress–strain responses do not reproduce experimental observations, but simulations in which cells behave as ductile materials with nonlinear mechanical properties do. Our models show that this behavior is a general emergent property of actomyosin networks in a supracellular context, in accordance with our experimental observations of actin reorganization within stretching cells.

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Lulu Regulates Shroom-Induced Apical Constriction during Neural Tube Closure

PLoS ONE ◽

10.1371/journal.pone.0081854 ◽

2013 ◽

Vol 8 (11) ◽

pp. e81854 ◽

Cited By ~ 16

Author(s):

Chih-Wen Chu ◽

Emma Gerstenzang ◽

Olga Ossipova ◽

Sergei Y. Sokol

Keyword(s):

Neural Tube ◽

Neural Tube Closure ◽

Apical Constriction ◽

Tube Closure

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The accuracy of the auto-stop function of different endodontic devices in detecting the apical constriction

BMC Oral Health ◽

10.1186/s12903-017-0425-y ◽

2017 ◽

Vol 17 (1) ◽

Author(s):

David W. Christofzik ◽

Andreas Bartols ◽

Mahmoud Khaled ◽

Birte Größner-Schreiber ◽

Christof E. Dörfer

Keyword(s):

Apical Constriction

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An in vivo Evaluation of Different Methods of Working Length Determination

The Journal of Contemporary Dental Practice ◽

10.5005/jp-journals-10024-1378 ◽

2013 ◽

Vol 14 (4) ◽

pp. 644-648 ◽

Cited By ~ 4

Author(s):

Nitin Shah ◽

Sarita Singh ◽

Jyoti Mandlik ◽

Kalpana Pawar ◽

Paras Gupta ◽

...

Keyword(s):

Tactile Sensation ◽

Pulp Chamber ◽

In Vivo Evaluation ◽

Extraction Working ◽

Apical Constriction ◽

Working Length ◽

Length Measurements ◽

Length Determination ◽

Electronic Apex Locator

ABSTRACT Objective The purpose of this in vivo study was to compare the ability of digital tactile, digital radiographic and electronic methods to determine reliability in locating the apical constriction. Materials and methods Informed consent was obtained from patients scheduled for orthodontic extraction. The teeth were anesthetized, isolated and accessed. The canals were negotiated, pulp chamber and canals were irrigated and pulp was extirpated. The working length was then evaluated for each canal by digital tactile sensation, an electronic apex locator (The Root ZX) and digital radiography. The readings were then compared with post-extraction working length measurements. Results The percentage accuracy indicated that EAL method (Root ZX) shows maximum accuracy, i.e. 99.85% and digital tactile and digital radiographic method (DDR) showed 98.20 and 97.90% accuracy respectively. Clinical significance Hence, it can be concluded that the EAL method (Root ZX) produced most reliable results for determining the accurate working length. How to cite this article Mandlik J, Shah N, Pawar K, Gupta P, Singh S, Shaik SA. An in vivo Evaluation of Different Methods of Working Length Determination. J Contemp Dent Pract 2013;14(4):644-648.

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Neuralized regulates a travelling wave of Epithelium-to-Neural Stem Cell morphogenesis in Drosophila

10.1101/2020.06.02.129353 ◽

2020 ◽

Author(s):

Chloé Shard ◽

Juan Luna-Escalante ◽

François Schweisguth

Keyword(s):

Stem Cells ◽

Ubiquitin Ligase ◽

Epithelial To Mesenchymal Transition ◽

Optic Lobe ◽

E3 Ubiquitin Ligase ◽

Tissue Level ◽

Travelling Wave ◽

Cell Morphogenesis ◽

Apical Constriction ◽

Mesenchymal Transition

AbstractMany tissues are produced during development by specialized progenitor cells emanating from epithelia via an Epithelial-to-Mesenchymal Transition (EMT). Most studies have so far focused on cases involving single or isolated groups of cells. Here we describe an EMT-like process that requires tissue level coordination. This EMT-like process occurs along a continuous front in the Drosophila optic lobe neuroepithelium to produce neural stem cells (NSCs). We find that emerging NSCs remain epithelial and apically constrict before dividing asymmetrically to produce neurons. Apical constriction is associated with contractile myosin pulses and requires the E3 ubiquitin ligase Neuralized and RhoGEF3. Neuralized down-regulates the apical protein Crumbs via its interaction with Stardust. Disrupting the regulation of Crumbs by Neuralized led to defects in apical constriction and junctional myosin accumulation, and to imprecision in the integration of emerging NSCs into the transition front. Neuralized therefore appears to mechanically couple NSC fate acquisition with cell-cell rearrangement to promote smooth progression of the differentiation front.

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Mechanical bistability enabled by ectodermal compression facilitates Drosophila mesoderm invagination

10.1101/2021.03.18.435928 ◽

2021 ◽

Author(s):

Hanqing Guo ◽

Michael Swan ◽

Shicheng Huang ◽

Bing He

Keyword(s):

Myosin Ii ◽

Cell Sheet ◽

Apical Surface ◽

Apical Constriction ◽

Out Of Plane ◽

A Cell ◽

Plane Compression ◽

Contractile Forces ◽

Tissue Relaxation ◽

Muscle Myosin

Apical constriction driven by non-muscle myosin II (″myosin″) provides a well-conserved mechanism to mediate epithelial folding. It remains unclear how contractile forces near the apical surface of a cell sheet drive out-of-plane bending of the sheet and whether myosin contractility is required throughout folding. By optogenetic-mediated acute inhibition of myosin, we find that during Drosophila mesoderm invagination, myosin contractility is critical to prevent tissue relaxation during the early, ″priming″ stage of folding but is dispensable for the actual folding step after the tissue passes through a stereotyped transitional configuration, suggesting that the mesoderm is mechanically bistable during gastrulation. Combining computer modeling and experimental measurements, we show that the observed mechanical bistability arises from an in-plane compression from the surrounding ectoderm, which promotes mesoderm invagination by facilitating a buckling transition. Our results indicate that Drosophila mesoderm invagination requires a joint action of local apical constriction and global in-plane compression to trigger epithelial buckling.

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