Wave Propagation of Junctional Remodeling in Collective Cell Movement of Epithelial Tissue: Numerical Simulation Study

During animal development, epithelial cells forming a monolayer sheet move collectively to achieve the morphogenesis of epithelial tissues. One driving mechanism of such collective cell movement is junctional remodeling, which is found in the process of clockwise rotation of Drosophila male terminalia during metamorphosis. However, it still remains unknown how the motions of cells are spatiotemporally organized for collective movement by this mechanism. Since these moving cells undergo elastic deformations, the influence of junctional remodeling may mechanically propagate among them, leading to spatiotemporal pattern formations. Here, using a numerical cellular vertex model, we found that the junctional remodeling in collective cell movement exhibits spatiotemporal self-organization without requiring spatial patterns of molecular signaling activity. The junctional remodeling propagates as a wave in a specific direction with a much faster speed than that of cell movement. Such propagation occurs in both the absence and presence of fluctuations in the contraction of cell boundaries.

Role of Turnover in Active Stress Generation in a Filament Network

We study the effect of turnover of cross-linkers, motors, and filaments on the generation of a contractile stress in a network of filaments connected by passive cross-linkers and subjected to the forces exerted by molecular motors. We perform numerical simulations where filaments are treated as rigid rods and molecular motors move fast compared to the time scale of an exchange of cross-linkers. We show that molecular motors create a contractile stress above a critical number of cross-linkers. When passive cross-linkers are allowed to turn over, the stress exerted by the network vanishes due to the formation of clusters. When both filaments and passive cross-linkers turn over, clustering is prevented and the network reaches a dynamic contractile steady state. A maximum stress is reached for an optimum ratio of the filament and cross-linker turnover rates. Taken together, our work reveals conditions for stress generation by molecular motors in a fluid isotropic network of rearranging filaments.

Left-right asymmetric cell intercalation drives directional collective cell movement in epithelial morphogenesis

Morphogenetic epithelial movement occurs during embryogenesis and drives complex tissue formation. However, how epithelial cells coordinate their unidirectional movement while maintaining epithelial integrity is unclear. Here we propose a novel mechanism for collective epithelial cell movement based on Drosophila genitalia rotation, in which epithelial tissue rotates clockwise around the genitalia. We found that this cell movement occurs autonomously and requires myosin II. The moving cells exhibit repeated left–right-biased junction remodelling, while maintaining adhesion with their neighbours, in association with a polarized myosin II distribution. Reducing myosinID, known to cause counter-clockwise epithelial-tissue movement, reverses the myosin II distribution. Numerical simulations revealed that a left–right asymmetry in cell intercalation is sufficient to induce unidirectional cellular movement. The cellular movement direction is also associated with planar cell-shape chirality. These findings support a model in which left–right asymmetric cell intercalation within an epithelial sheet drives collective cellular movement in the same direction.

Coordinated epithelial movement during embryogenesis drives complex tissue formation, but how this movement is coordinated to maintain epithelial integrity is not clear. Here the authors show that left-right asymmetry in cell intercalation drives clockwise rotation of epithelia in Drosophila genital development.

Cell Chirality Induces Collective Cell Migration in Epithelial Sheets

During early development, epithelial cells form a monolayer sheet and migrate in a uniform direction. Here, we address how this collective migration can occur without breaking the cell-to-cell attachments. Repeated contraction and expansion of the cell-to-cell interfaces enables the cells to rearrange their positions autonomously within the sheet. We show that when the interface tension is strengthened in a direction that is tilted from the body axis, cell rearrangements occur in such a way that unidirectional movement is induced. We use a vertex model to demonstrate that such anisotropic tension can generate the unidirectional motion of cell sheets. Our results suggest that cell chirality facilitates collective cell migration during tissue morphogenesis.

Reversible hypopituitarism with pituitary tuberculoma

A 50-year-old woman presented with a headache and nausea. A sellar and suprasellar mass was detected on MRI; the tumor was heterogeneously enhanced with gadolinium, and the pituitary stalk was slightly thickened. Laboratory tests revealed severe growth hormone, luteinizing hormone, follicle-stimulating hormone and thyroid-stimulating hormone deficiencies. A pathological examination of the tumor showed scattered granulomas with central necrosis and Langhans giant cells. Tuberculin skin and QuantiFERON TB-Gold tests (QFT-2G) were positive. Accordingly, we diagnosed the patient with pituitary tuberculoma presenting with pituitary dysfunction. Following treatment with antituberculous drugs, the pituitary hormone function normalized and the pituitary tuberculoma disappeared.

Use of color Doppler ultrasonography to measure thyroid blood flow and differentiate graves' disease from painless thyroiditis

BACKGROUNDS

Color Doppler ultrasonography (CDU) has not yet been established as a method to investigate the pathogenesis of thyrotoxicosis.

OBJECTIVES

Our first objective was to determine whether the measurement of peak systolic blood-flow velocity in the superior thyroid artery (STV) and thyroid tissue blood flow (TBF) using CDU could differentiate Graves' disease (GD) from painless thyroiditis (PT). The second objective was to examine the factors mediating increased blood flow to the thyroid gland in GD.

METHODS

Recruited patients had untreated GD or PT and visited the Department of Internal Medicine (I), Osaka Medical College, between April 1, 2006 and May 31, 2010. Age, gender, blood pressure, pulse rate, thyroid-stimulating hormone, free thyroxine, tri-iodothyronine, TSH receptor antibody and thyroid volume were evaluated in patients. In addition, bilateral measurements of STV, TBF and peak systolic velocity in the common carotid artery (CCV) were also performed. TBF was quantified by calculating the ratio of blood-flow pixels to total pixels in the region of interest using sagittal section images of the thyroid gland. Receiver-operating characteristic curve analysis was performed to determine the ability of STV and TBF measurements to differentiate GD from PT.

RESULTS

For the average of STV measured on both sides, the area under the receiver-operating characteristic curve (AUC) was 0.956. For the average of TBF measured on both sides, the AUC was 0.920. At an average STV cut-off value of 43 cm/s, the sensitivity to discriminate GD from PT was 0.87 and the specificity was 1.00. At an average TBF cut-off value of 3.8%, the sensitivity was 0.71 and the specificity was 1.00. In the GD group, neither blood pressure nor pulse rate correlated with the average STV or TBF. Moreover, there was no correlation between STV and CCV or between TBF and CCV on either side. However, STV was correlated with TBF (right side: R = 0.47; left side: R = 0.52).

CONCLUSIONS

The results demonstrate that STV and TBF are useful for differentiating GD from PT. Furthermore, the increased STV and TBF found in GD are not related to hyperthyroidism-induced increases in systolic blood pressure, pulse rate or CCV.

Theoretical model for cell migration with gradient sensing and shape deformation

Amoeboid cells take various shapes during migration, depending on the cell type and its environment. Deformability of the cell shape can then affect the migrating behavior. In this article, we introduce a theoretical model of chemotactic cell migration with elliptical shape deformation. Based on the model, we calculate the stationary distributions of the migration directions analytically. As a result, we find that the distributions show different characteristics depending on the difference in the interdependence of the internal polarity, cell morphology and gradient sensing.

Effect of L-thyroxine replacement on apolipoprotein B-48 in overt and subclinical hypothyroid patients

Apolipoprotein B-48 (ApoB-48) is a constituent of chylomicrons and chylomicron remnants, and is thought to be one of the risk factors for atherosclerosis. We evaluated the effect of L-thyroxine (L-T(4)) replacement on serum ApoB-48 levels in patients with primary hypothyroidism. Eighteen patients with overt hypothyroidism (OH) and 18 patients with subclinical hypothyroidism (SH) participated in the study. The lipid profiles, including ApoB-48, were measured in patients with hypothyroidism before and 3 months after L-T(4) replacement. After L-T(4) replacement, the serum concentrations of all lipoproteins, exclusive of lipoprotein(a) (Lp(a)), were significantly decreased in patients with OH. In patents with SH, the serum levels of total cholesterol (TC), non-high-density lipoprotein cholesterol (non-HDL-C), remnant-like particle cholesterol (RLP-C), apolipoprotein B (ApoB), and ApoB-48 decreased significantly after L-T(4) replacement. The serum levels of triglycerides (TG), HDL-C, low-density lipoprotein cholesterol (LDL-C), apolipoprotein A1 (ApoA-1), and Lp(a) did not change significantly. In all 36 patients, the reduction in the ApoB-48 levels correlated significantly with the reduction in TSH levels (r = 0.39, P<0.05). This study showed clearly that L-T(4) replacement might reduce serum levels of ApoB-48 in both OH and SH patients. Such altered serum levels of ApoB-48 in patients with OH and SH may be related to the disturbed metabolism of chylomicron remnants in patients with hypothyroidism.

Directional sensing of deformed cells under faint gradients

We consider the physical limit of the directional sensing ability of living cells, as in chemotaxis, under a low concentration and shallow chemoattractant gradient. Elliptic cells sense the direction, which is a stochastic variable of a characteristic distribution with peaks at directions not necessarily to the gradient. The peak positions depend on the information of the gradient that cells use to infer the direction and also the shape and orientation of cells. Cells of different shapes may use different inference strategies to increase their directional sensing performance.

Deformable self-propelled domain in an excitable reaction-diffusion system in three dimensions

We derive a set of equations of motion for an isolated domain in an excitable reaction-diffusion system in three dimensions. In the singular limit where the interface is infinitesimally thin, the motion of the center of mass coupled with deformation is investigated near the drift bifurcation where a motionless domain becomes unstable and undergoes migration. This is an extension of our previous theory in two dimensions. We show that there are three basic motions of a domain, straight motion, rotating motion, and helical motion. The last one is a characteristic of three dimensions. The phase diagram of these three solutions is given in the parameter space of the original reaction-diffusion equations.

Hypopituitarism in a patient with transsphenoidal cephalocele: longitudinal changes in endocrinological abnormalities

We report a 21-year-old man with severe fatigue due to hypopituitarism. At the age of 6 years, he was diagnosed with short stature due to a GH deficiency accompanied by a sphenoid cystic lesion. Laboratory findings and provocative tests for pituitary hormone function revealed ACTH, LH, FSH, TSH, and GH deficiency. Computed tomography and magnetic resonance imaging revealed transsphenoidal cephalocele due to a defect in the floor of the sella turcica. At 6 years, he only had severe GH deficiency and poor response of LH to LHRH. Hypothalamic-pituitary dysfunction and pituitary herniation have progressed subsequently; we observed a longitudinal progression of hypothalamic-pituitary dysfunction caused by transsphenoidal cephalocele. This dysfunction requires the selection of a treatment that will not aggravate the condition further.

Linear viscoelasticity of a single semiflexible polymer with internal friction

The linear viscoelastic behaviors of single semiflexible chains with internal friction are studied based on the wormlike-chain model. It is shown that the frequency dependence of the complex compliance in the high frequency limit is the same as that of the Voigt model. This asymptotic behavior appears also for the Rouse model with internal friction. We derive the characteristic times for both the high frequency limit and the low frequency limit and compare the results with those obtained by Khatri et al.