Cellular Hydraulics Suggests a Poroelastic Cytoplasm Rheology

The cytoplasm represents the largest part of the cell by volume and hence its rheology sets the rate at which cellular shape change can occur. Recent experimental evidence suggests that cytoplasmic rheology can be described using a poroelastic formulation in which the cytoplasm is considered a biphasic material constituted of a porous elastic solid meshwork (cytoskeleton, organelles, macromolecules) bathed in an interstitial fluid (cytosol). In this picture, the rate of cellular deformation is limited by the rate at which intracellular water can redistribute within the cytoplasm. Though this is a conceptually attractive model, direct supporting evidence has been lacking. Here we present such evidence and directly validate this concept to explain cellular rheology at physiologically relevant time-scales using microindentation tests in conjunction with mechanical, chemical and genetic treatments. Our results show that water redistribution through the solid phase of cytoplasm (cytoskeleton and crowders) plays a fundamental role in setting cellular rheology.Engineering and Applied Science

The cytoplasm of living cells behaves as a poroelastic material

The cytoplasm is the largest part of the cell by volume and hence its rheology sets the rate at which cellular shape changes can occur. Recent experimental evidence suggests that cytoplasmic rheology can be described by a poroelastic model, in which the cytoplasm is treated as a biphasic material consisting of a porous elastic solid meshwork (cytoskeleton, organelles, macromolecules) bathed in an interstitial fluid (cytosol). In this picture, the rate of cellular deformation is limited by the rate at which intracellular water can redistribute within the cytoplasm. However, direct supporting evidence for the model is lacking. Here we directly validate the poroelastic model to explain cellular rheology at physiologically relevant timescales using microindentation tests in conjunction with mechanical, chemical and genetic treatments. Our results show that water redistribution through the solid phase of the cytoplasm (cytoskeleton and macromolecular crowders) plays a fundamental role in setting cellular rheology

Retained Surgical Foreign Bodies after Surgery

The problem of retained surgical bodies (RSB) after surgery is an issue for surgeons, hospitals and the entire medical team. They have potentially harmful consequences for the patient as they can be life threatening and usually, a further operation is necessary. The incidence of RSB is between 0.3 to 1.0 per 1,000 abdominal operations, and they occur due to a lack of organisation and communication between surgical staff during the process. Typically, the RSB are surgical sponges and instruments located in the abdomen, retroperitoneum and pelvis

OPEN STOMATA3 - an ABC transporter implicated in ABA signalling, drought and light response

Mutants sensitive to progressive water deficit are characterized by excessive transpiration due to the failure of stomatal closure and can therefore be detected as cold plants (Fig. 1 blue) by remote infrared imaging (Merlot et al., 2002). Among the signalling mutants, three are collectively named open stomata (ost). The corresponding OST1 and OST2 genes encode an ABA-activated kinase and a P-type H+-ATPase, respectively (Mustilli et al., 2002; Merlot et al., 2007). The current work deals with OST3 which encodes an ATP-binding cassette (ABC) transporter. There are over 120 members of the ABC protein in the superfamily of Arabidopsis thaliana. Most of them are membrane-bound proteins that transport a diverse range of substances across the phospholipid bilayer. Characterisation of the mutant phenotype confirmed that ost3 transpires excessively (Fig. 1, 2). We have also shown that the ost3 mutations reduce seed dormancy (Fig. 3) but seed sensitivity to exogenous ABA seems unaffected (data not shown). The guard cells of ost3 are impaired in responses to ABA and light (Fig. 4), but are normal with respect to low level of CO2 which stimulates stomatal opening (data not shown). OST3 is expressed mainly in leaves, particularly in guard cells (Fig. 5), but it is low in root tissues. Transgenic expression of the OST3 protein fused to GFP in the ost3 mutant can rescue the phenotype and moreover, the fusion protein is targeted exclusively to the plasma membrane (Fig. 6) suggesting that it has a role in intercellular transport required for ABA signal perception. We found that OST3 interacts with OST2 (Fig. 8) and OST1 (Fig. 8 + 9). The last observation is also consistent with the fact that OST3 can be phosphorylated by OST1 in vitro (Fig. 7). Therefore we suggest that the trio of proteins identified by our genetic screen may function in the same signalling complex in mediating stomatal response

The GRAVITY young stellar object survey: VIII. Gas and dust faint inner rings in the hybrid disk of HD141569

Stars and planetary system

The Diagnostic Role of Hyperbilirubinemia in Complicated and Non -complicated Appendicitis.

Background: Acute appendicitis is one of the most frequent causes of abdominal pain. Early diagnosis is the key to success for the surgeon, followed by the treatment with operation or conservative treatment as a new approach, before the stage of gangrenous appendicitis or perforation occurs. Aim: This study aims to establish he role of hyperbilirubinemia as a laboratory marker in prediction of acute appendicitis in the early diagnosis. Materials and methods: This is a cross-sectional study; it included 201 patients admitted in the emergency ward with suspicion for acute appendicitis. All patients that participated in this study have been subject to appendectomy. The blood samples were taken from all patients in order to analyze the level of total/direct bilirubin. Results: The study samples of 201 patients consisted of 67.7% with complicated appendicitis and 32.3% with non-complicated appendicitis. The sensitivity, specificity, PPV, NPV for laboratory marker, as predictor for complicated vs non-complicated cases of appendicitis was as follows: Total bilirubin; specificity (72.3%), sensitivity (54.4%), PPV (80.4%), NPV (43.1%), Conclusion: Elevation of total/direct bilirubin level in patients with clinical signs of acute appendicitis might predict the stage of acute appendicitis, such prediction may help surgeons to provide accurate treatment of the disease without delay in the diagnosis. This accuracy can be further supplemented by using Alvarado scoring model during the clinical approach

Global Competition and Regional Governance in Pearl River Delta Region

Knowing the setting of roller compacted concrete (RCC) is an essential element within the framework of the building of multi-layered structures such as dams

Mesenteric Meckel’s diverticulum or intestinal duplication cyst: A case report with review of literature

Introduction: A Meckel’s diverticulum (MD) is the most common congenital anomaly of the gastrointestinal (GI) tract. They arise from the middle-to-distal ileum. Contrary to MD, intestinal duplication cyst (IDC) is uncommon congenital anomaly of GI, but can occur anywhere from the tongue to the anus. Presentation of case: Here we report an 18-year-old male who presented to the department of abdominal surgery with chronic abdominal pain, frequent vomiting and mild abdominal distension. Following radiological investigation, a laparotomy was performed with the preoperative diagnosis of a mesenteric cyst. Intraoperativelly it became apparent that the cystic mass was on the mesenteric aspect of the small bowel without intestinal communication. Resection of the cyst was performed. Histological examination of the specimen revealed the presence of gastric tissue, which resembles MD. Although, the exact diagnosis of this cystic mass is ambiguous between MD and IDC, because of similar clinical signs, their complications and presence of gastric mucosa, however surgical treatment is gold standard of both. Conclusion: This case report underlines the necessity of how to differentiate between MD and IDC, although, surgical management is recommended for both

Stick-slip dynamics of cell adhesion triggers spontaneous symmetry breaking and directional migration of mesenchymal cells on one-dimensional lines

International audienceDirectional cell motility relies on the ability of single cells to establish a front-rear polarity and can occur in the absence of external cues. The initiation of migration has often been attributed to the spontaneous polarization of cytoskeleton components, while the spatiotemporal evolution of cell-substrate interaction forces has yet to be resolved. Here, we establish a one-dimensional microfabricated migration assay that mimics the complex in vivo fibrillar environment while being compatible with high-resolution force measurements, quantitative microscopy, and optogenetics. Quantification of morphometric and mechanical parameters of NIH-3T3 fibro-blasts and RPE1 epithelial cells reveals a generic stick-slip behavior initiated by contractility-dependent stochastic detachment of adhesive contacts at one side of the cell, which is sufficient to trigger cell motility in 1D in the absence of pre-established polarity. A theoretical model validates the crucial role of adhesion dynamics, proposing that front-rear polarity can emerge independently of a complex self-polarizing system