Heterogeneous identity, stiffness and growth characterise the shoot apex of Arabidopsis stem cell mutants.

Stem cell homeostasis in the shoot apical meristem involves a core regulatory feedback loop between the signalling peptide CLAVATA3 (CLV3), produced in stem cells, and the transcription factor WUSCHEL, expressed in the underlying organising centre. clv3 mutant meristems display massive overgrowth, which is thought to be caused by stem cell overproliferation, although it is unknown how uncontrolled stem cell divisions lead to this altered morphology. Here, we reveal local buckling defects in mutant meristems, and use analytical models to show how mechanical properties and growth rates may contribute to the phenotype. Indeed, clv3 mutant meristems are mechanically more heterogeneous than the wild type, and also display regional growth heterogeneities. Furthermore, stereotypical wild-type meristem organisation, in which cells simultaneously express distinct fate markers, is lost in mutants. Finally, cells in mutant meristems are auxin responsive, suggesting that they are functionally distinguishable from wild-type stem cells. Thus, all benchmarks show that clv3 mutant meristem cells are different from wild-type stem cells, suggesting that overgrowth is caused by the disruption of a more complex regulatory framework that maintains distinct genetic and functional domains in the meristem.

Systemic inflammatory syndrome in COVID-19-SISCoV study: systematic review and meta-analysis.

BACKGROUND: There has been a recent upsurge in the cases of Multisystem inflammatory syndrome in children (MIS-C) associated with Coronavirus disease (COVID-19). We performed a systematic review and meta-analysis on the demographic profile, clinical characteristics, complications, management, and prognosis of this emerging novel entity. METHODS: Using a predefined search strategy incorporating MeSH terms and keywords, all known literature databases were searched up till 10th July 2020. The review was done in accordance with PRISMA guidelines and registered in PROSPERO (CRD4202019757). RESULTS: Of the 862 identified publications, 18 studies comprising 833 patients were included for meta-analysis. The socio-demographic profile showed male predilection (p = 0.0085) with no significant racial predisposition. A higher incidence of gastrointestinal symptoms (603/715, 84.3%), myocarditis (191/309, 61.8%), left ventricular dysfunction (190/422, 45.0%), pericardial (135/436, 31.0%) and neurological symptoms (138/602, 22.9%) was reported. Serological evidence of SARS-CoV-2 had higher sensitivity compared to rtPCR (291/800, 36.4% vs 495/752, 65.8%; p < 0.001). Coronary artery anomaly (CAA) was reported in 117/681 in 9 publications (17.2%). A total of 13 (1.6%) fatalities were reported. CONCLUSION: Clinicians need to be vigilant in identifying the constellation of these symptoms in children with clinical or epidemiologic SARS-CoV-2 infection. Early diagnosis and treatment lead to a favorable outcome. IMPACT: Key message This review analyses the demographic profile, clinical spectrum, management strategies, prognosis, and pathophysiology of MIS-C among children with SARS-CoV-2 infection. The stark differences of MIS-C from Kawasaki disease with respect to demographics and clinical spectrum is addressed. Over-reliance on rtPCR for diagnosis can miss the diagnosis of MIS-C. New addition to existing literature The first systematic review and meta-analysis of published literature on MIS-C associated with COVID-19. IMPACT: The article will serve to spread awareness among the clinicians regarding this emerging novel entity, so that diagnosis can be made early and management can be initiated promptly.

TGF-ß induces changes in breast cancer cell deformability.

Mechanical properties of cells are shown to regulate cell behaviors leading to phenotypic changes that may aid in the development and progression of disease. In this study, we used atomic force microscopy (AFM) indentation with a spherical probe to characterize the elastic and viscoelastic properties of invasive (MDA-MB-231) and noninvasive (MCF-7) breast cancer cells treated with transforming growth factor-ß (TGF-ß). We also used confocal fluorescence imaging to investigate the sub-membrane cytoskeletal structure of the cells. Results showed significant alterations in moduli of both cell types after 24 h TGF-ß treatment which had a context dependent response; moduli for MDA-MB-231 decreased whereas MCF-7 demonstrated stiffening response. Stress relaxation tests showed increased fluid-like nature of MDA-MB-231 following TGF-ß treatment and lower fluidity for MCF-7 cells. We also observed significant alterations in the expression and orientation of actin stress fibers with TGF-ß treatment which correlated with the changes in cell mechanics. Less invasive MCF-7 cells had a delayed overall increase in cell deformability after 48 h exposure to TGF-ß; a similar trend was observed for MDA-MB cells. These changes may be important to facilitate migration, for instance, during metastasis of cancer cells through submicron sized spaces.

Pneumatic Non-Equibiaxial Cell Stretching Device With Live-Cell Imaging.

OBJECTIVE: Adherent cell behavior is influenced by a complex interplay of factors, including chemical and mechanical signals. In vitro experiments that mimic the mechanical environment experienced by cells in vivo are crucial for understanding cellular behavior and the progression of disease. In this study, we developed and validated a low-cost pneumatically-controlled cell stretcher with independent control of strain in two directions of a membrane, enabling unequal biaxial stretching and real-time microscopy during actuation. METHODS: The stretching was achieved by two independent pneumatic channels controlled by electrical signals. We used finite element simulations to compute the membrane's strain field and particle tracking algorithms based on image processing techniques to validate the strain fields and measure the cell orientation and morphology. RESULTS: The device can supply uniaxial, equibiaxial, and unequal biaxial stretching up to [Formula: see text] strain in each direction at a frequency of [Formula: see text], with a strain measurement error of less than 1%. Through live cell imaging, we determined that distinct stretching patterns elicited differing responses and alterations in cell orientation and morphology, particularly in terms of cell length and area. CONCLUSION: The device successfully provides a large, uniform, and variable strain field for cell experiments, while also enabling real-time, live cell imaging. SIGNIFICANCE: This scalable, low-cost platform provides mechanical stimulation to cell cultures by independently controlling strains in two directions. This could contribute to a deeper understanding of cellular response to bio-realistic strains and could be useful for future in vitro drug testing platforms.

Substrate Stiffness Modulates TGF-ß Activation and ECM-Associated Gene Expression in Fibroblasts.

Transforming growth factor-ß (TGF-ß) is a multifunctional cytokine that regulates the expression of ECM-associated genes during early injury. Tissue fibrosis development is driven by synergistic cues between the evolving biochemical and mechanical milieu. Few studies have addressed the role of substrate stiffness on TGF-ß activity and extracellular matrix (ECM)-associated genes. We used a commercial formulation of polydimethylsiloxane (PDMS) to fabricate substrates of 40 kPa, 300 kPa, and 1.5 MPa stiffness, and cultured the HMF3S fibroblasts on substrates. We quantified TGF-ß protein secreted by HMF3S cells on different substrates using a TGF-ß responsive promoter reporter assay. We also tested for variations in gene expression levels on the substrates using RT-PCR and Western blotting and determined the MMP-2 and MMP-9 activities with gelatin zymography. The results showed that TGF-ß protein activation was significantly compromised at lower stiffnesses. The expression of integrin α5 decreased on lower stiffness substrates and correlated with inefficient TGF-ß protein activation. Collagen I, collagen III, and MMP-2 expression levels were lower on softer substrates; there was little MMP-9 activity on all substrates. Cell and nuclear morphologies were more rounded on compliant substrates, correlating with increased tubulin expression. Proliferations were higher on stiffer substrates, whereas cells on softer substrates showed cell cycle arrest. These results demonstrated critical feedback mechanisms between substrate stiffness and ECM regulation by fibroblasts, relevant in fibrosis.

Delayed Presentation of Mandibular Osteonecrosis Following Herpes Zoster Infection - A Case Report.

Rationale: Apart from the usual presentation of herpes zoster (HZ) infection (HZI), reports of spontaneous teeth exfoliation and osteonecrosis are infrequent and sporadic. Patient Concerns: A 51-year-old male patient presented with spontaneous exfoliation of multiple teeth and subsequent pathological fracture on the right side of the lower jaw after three months of HZI. Diagnosis: Biopsy was taken from the alveolar bone of the oedematous region, which revealed the presence of trabeculae of dead bone with empty lacunae. Intervention: Necrosed part of the alveolar bone was excised under local anaesthesia and antibiotic coverage, which was followed by open reduction and internal fixation of the pathological fracture under general anaesthesia. Outcomes: The patient was followed up for one year without any evidence of recurrences. Take-away Lessons: Presentation of osteonecrosis following HZI is unique but rare and should be diagnosed at the earliest.

Atypical peripheral actin band formation via overactivation of RhoA and nonmuscle myosin II in mitofusin 2-deficient cells.

Cell spreading and migration play central roles in many physiological and pathophysiological processes. We have previously shown that MFN2 regulates the migration of human neutrophil-like cells via suppressing Rac activation. Here, we show that in mouse embryonic fibroblasts, MFN2 suppresses RhoA activation and supports cell polarization. After initial spreading, the wild-type cells polarize and migrate, whereas the Mfn2-/- cells maintain a circular shape. Increased cytosolic Ca2+ resulting from the loss of Mfn2 is directly responsible for this phenotype, which can be rescued by expressing an artificial tether to bring mitochondria and endoplasmic reticulum to close vicinity. Elevated cytosolic Ca2+ activates Ca2+/calmodulin-dependent protein kinase II, RhoA, and myosin light-chain kinase, causing an overactivation of nonmuscle myosin II, leading to a formation of a prominent F-actin ring at the cell periphery and increased cell contractility. The peripheral actin band alters cell physics and is dependent on substrate rigidity. Our results provide a novel molecular basis to understand how MFN2 regulates distinct signaling pathways in different cells and tissue environments, which is instrumental in understanding and treating MFN2-related diseases.

Stress fiber growth and remodeling determines cellular morphomechanics under uniaxial cyclic stretch.

Stress fibers in the cytoskeleton are essential in maintaining cellular shape and influence cellular adhesion and migration. Cyclic uniaxial stretching results in cellular reorientation orthogonal to the applied stretch direction. The mechanistic cues underlying changes to cellular form and function to stretch stimuli are currently underexplored. We show stretch-induced stress fiber lengthening, their realignment, and increased cortical actin in NIH 3T3 fibroblasts stretched over varied amplitudes and durations. Higher amounts of actin and stress fiber alignment were accompanied with an increase in the effective elastic modulus of cells. Microtubules did not contribute to the measured stiffness or reorientation response but were essential to the nuclear reorientation. We used a phenomenological growth and remodeling law, based on the experimental data, to model stress fiber elongation and reorientation dynamics based on a nonlinear, orthotropic, fiber-reinforced continuum representation of the cell. The model predicts the changes observed fibroblast morphology and increased cellular stiffness under uniaxial cyclic stretch which agrees with experimental results. Such studies are important in exploring the differences underlying mechanotransduction and cellular contractility under stretch.

AI-CoV Study: Autoimmune Encephalitis Associated With COVID-19 and Its Vaccines-A Systematic Review.

BACKGROUND AND PURPOSE: Autoimmune encephalitis (AIE) following coronavirus disease 2019 (COVID-19) is an underexplored condition. This study aims to systematically review the clinico-investigational and pathophysiologic aspects of COVID-19 and its vaccines in association with AIE, and identify the factors predicting neurological severity and outcomes. METHODS: Relevant data sources were searched using appropriate search terms on January 15, 2022. Studies meeting the criteria for AIE having a temporal association with COVID-19 or its vaccines were included. RESULTS: Out of 1,894 citations, we included 61 articles comprising 88 cases: 71 of COVID-19-associated AIE, 3 of possible Bickerstaff encephalitis, and 14 of vaccine-associated AIE.There were 23 definite and 48 possible seronegative AIE cases. Anti-NMDAR (N-methyl-D-aspartate receptor; n=12, 16.9%) was the most common definite AIE. Males were more commonly affected (sex ratio=1.63) in the AIE subgroup. The neurological symptoms included alteredmental state (n=53, 74.6%), movement disorders (n=28, 39.4%), seizures (n=24, 33.8%), behavioural (n=25, 35.2%), and speech disturbances (n=17, 23.9%). The median latency to AIE diagnosis was 14 days (interquartile range=4-22 days). Female sex and ICU admission had higherrisks of sequelae, with odds ratio (OR) of 2.925 (95% confidence interval [CI]=1.005-8.516)and 3.515 (95% CI=1.160-10.650), respectively. Good immunotherapy response was seen in42/48 (87.5%) and 13/13 (100%) of COVID-19-associated and vaccine-associated AIE patients, respectively. Sequelae were reported in 22/60 (36.7%) COVID-19 associated and 10/13 (76.9%) vaccine-associated cases. CONCLUSIONS: The study has revealed diagnostic, therapeutic, and pathophysiological aspects of AIE associated with COVID-19 and its vaccines, and its differences from postinfectious AIE. SYSTEMATIC REVIEW REGISTRATION: PROSPERO registration number CRD42021299215.

Role of Fiber Orientations in the Mechanics of Bioinspired Fiber-Reinforced Elastomers.

Fiber reinforcement is a crucial attribute of soft-bodied muscular hydrostats that have the ability to undergo large deformations and maintain their posture. Helically wound fibers around the cylindrical worm body help control the tube diameter and length. Geometric considerations show that a fiber winding angle of 54.7°, called the magic angle, results in a maximum enclosed volume. Few studies have combined both experimental and theoretical techniques to explore the effects of fiber winding at varied angles on the large deformation mechanics of fiber-reinforced elastomers (FRE). We fabricated FRE materials in transversely isotropic layouts varying from 0° to 90° using a custom filament winding technique and characterized the nonlinear stress-strain relationships using uniaxial and equibiaxial experiments. We used these data within a continuum mechanical framework to propose a novel constitutive model for incompressible FRE materials with embedded extensible fibers. The model includes individual contributions from the matrix and fibers in addition to coupled terms in strain invariants, I1 and I4. The deviatoric stress components show inversion at fiber orientation angles near the magic angle in the FRE composites. These results are useful in soft robotic applications and in the biomechanics of fiber-reinforced tissues such as the myocardium, arteries, and skin.

Intraoral Management of Latrogenic Tooth Displacement: A Report of Two Cases and a Brief Review of Literature.

Iatrogenic displacement of a tooth or tooth fragment is a rare but well-recognized complication that occurs during exodontia. The most common sites of dislodgment of a mandibular third molar fragment are the sublingual, submandibular, and pterygomandibular and lateral pharyngeal spaces. Removal of a displaced tooth from these spaces may be complex due to poor visualization and limited access. A thorough evaluation of all significant risk factors along with precise localization of the tooth by clinical and radiographic means should be performed to prevent untoward complications. This paper reports two cases of iatrogenic displacement of mandibular third molar teeth, in the sublingual space and lingual pouch. Both the cases were managed intraorally under general anesthesia, and the postoperative healing was satisfactory and uncomplicated. A brief review of literature is also provided in this paper.

Note: Development of a cryocooler based high efficiency cryosorption pump.

In this communication, we report the development of a cryosorption pump, whose pumping speeds are higher at least by a factor of 1.5 compared to the commercial pumps in specific pressure ranges. This uses a material of high adsorbing capacity along with an adhesive of high thermal conductivity. The measured pumping speeds of these pumps for different gases such as nitrogen, argon, hydrogen, and helium are higher than the commercial cryopumps in the pressure range from 5 × 10-6 mbar to 5 × 10-5 mbar. The developed pump will be quite useful for fusion applications.

Single Injection Technique Prolotherapy for Hypermobility Disorders of TMJ Using 25 % Dextrose: A Clinical Study.

INTRODUCTION: Hypermobility disorders of the Temporomandibular joint (TMJ) can be treated by both conservative and surgical approaches. Conservative approaches should be considered as first line treatment for such disorders. Prolotherapy with 25 % dextrose being injected into the posterior pericapsular tissues is one such treatment modality with favorable outcomes. AIM: To study the efficacy of single injection of 25 % dextrose in pericapsular tissues in the management of hypermobility joint disorders of TMJ as first line treatment. PATIENTS AND METHODS: We have studied a total of 23 patients suffering from either chronic recurrent dislocation or subluxation of the TMJ who were treated with the single injection technique prolotherapy with 25 % dextrose into the pericapsular tissues along with auriculotemporal nerve block and found encouraging results. RESULTS: Overall success rate in our study was 91.3 % (21/23) with a minimum follow up period of 13.9 months. Number of successfully treated patients requiring one injection was 7 (30.4 %), two injections was 8 (34.7 %) and requiring three injections was 6 (26.1 %). There were no permanent complications. CONCLUSION: Hence the use of 25 % dextrose as a proliferant to treat hypermobilty disorders of the TMJ is recommended by us as a first line treatment option as it is safe, economical and an easy procedure associated with minimal morbidity.