Artificial metaplasia of pigmented epithelium into retina in tadpoles and adult frogs

Development ◽  
1972 ◽  
Vol 28 (3) ◽  
pp. 521-546
Author(s):  
G. V. Lopashov ◽  
Alla A. Sologub
Keyword(s):  
Rana Temporaria ◽  
Cell Types ◽  
Control Mechanisms ◽  
General Control ◽  
Pigmented Epithelium ◽  
The Stability

The present work was aimed at investigating the possibility and conditions necessary for the artificial transformation of one tissue into another. Experiments were carried out with the pigmented epithelium of the eye in tadpoles and adult frogs of Rana temporaria. Following the removal of the mesenchyme envelopes (or their exfoliation during the experiment), pigmented epithelium transformed into retina under the influence of retina from tadpoles of the same species. This phenomenon was observed both under the cultivation of a piece of retina in a sandwich of pigmented epithelium and the transplantation of pigmented epithelium layers into the eye cavity of tadpoles. Such transformation did not occur in the absence of retinal influence. Metaplasia requires the removal of the mesenchyme envelopes, the action of the retinal agent, as well as preservation of the integrity of the pigmented epithelium layer and subsequent proliferation of its cells. The character of general control mechanisms both maintaining the stability of cell types and leading to their transformation into other cell types is discussed.

scholarly journals Laminin-binding integrins and their tetraspanin partners as potential antimetastatic targets

2010 ◽  
Vol 12 ◽  
Author(s):  
Christopher S. Stipp
Keyword(s):  
Plasma Membrane ◽  
Cell Types ◽  
Cell Junctions ◽  
Control Mechanisms ◽  
Membrane Domains ◽  
The Stability ◽  
Different Cell Types ◽  
Integrin Family ◽  
Laminin Binding

Within the integrin family of cell adhesion receptors, integrins α3β1, α6β1, α6β4 and α7β1 make up a laminin-binding subfamily. The literature is divided on the role of these laminin-binding integrins in metastasis, with different studies indicating either pro- or antimetastatic functions. The opposing roles of the laminin-binding integrins in different settings might derive in part from their unusually robust associations with tetraspanin proteins. Tetraspanins organise integrins into multiprotein complexes within discrete plasma membrane domains termed tetraspanin-enriched microdomains (TEMs). TEM association is crucial to the strikingly rapid cell migration mediated by some of the laminin-binding integrins. However, emerging data suggest that laminin-binding integrins also promote the stability of E-cadherin-based cell–cell junctions, and that tetraspanins are essential for this function as well. Thus, TEM association endows the laminin-binding integrins with both pro-invasive functions (rapid migration) and anti-invasive functions (stable cell junctions), and the composition of TEMs in different cell types might help determine the balance between these opposing activities. Unravelling the tetraspanin control mechanisms that regulate laminin-binding integrins will help to define the settings where inhibiting the function of these integrins would be helpful rather than harmful, and may create opportunities to modulate integrin activity in more sophisticated ways than simple functional blockade.

scholarly journals Automated analysis of filopodial length and spatially resolved protein concentration via adaptive shape tracking

2016 ◽  
Vol 27 (22) ◽  
pp. 3616-3626 ◽  
Author(s):  
Tanumoy Saha ◽  
Isabel Rathmann ◽  
Abhiyan Viplav ◽  
Sadhana Panzade ◽  
Isabell Begemann ◽  
...  
Keyword(s):  
Protein Concentration ◽  
Growth Dynamics ◽  
Automated Analysis ◽  
Cell Types ◽  
Control Mechanisms ◽  
Spatially Resolved ◽  
Novel Approach ◽  
Associated Proteins

Filopodia are dynamic, actin-rich structures that transiently form on a variety of cell types. To understand the underlying control mechanisms requires precise monitoring of localization and concentration of individual regulatory and structural proteins as filopodia elongate and subsequently retract. Although several methods exist that analyze changes in filopodial shape, a software solution to reliably correlate growth dynamics with spatially resolved protein concentration along the filopodium independent of bending, lateral shift, or tilting is missing. Here we introduce a novel approach based on the convex-hull algorithm for parallel analysis of growth dynamics and relative spatiotemporal protein concentration along flexible filopodial protrusions. Detailed in silico tests using various geometries confirm that our technique accurately tracks growth dynamics and relative protein concentration along the filopodial length for a broad range of signal distributions. To validate our technique in living cells, we measure filopodial dynamics and quantify spatiotemporal localization of filopodia-associated proteins during the filopodial extension–retraction cycle in a variety of cell types in vitro and in vivo. Together these results show that the technique is suitable for simultaneous analysis of growth dynamics and spatiotemporal protein enrichment along filopodia. To allow readily application by other laboratories, we share source code and instructions for software handling.

Identification of stable reference genes in differentiating human pluripotent stem cells

2015 ◽  
Vol 47 (6) ◽  
pp. 232-239 ◽  
Author(s):  
Gustav Holmgren ◽  
Nidal Ghosheh ◽  
Xianmin Zeng ◽  
Yalda Bogestål ◽  
Peter Sartipy ◽  
...  
Keyword(s):  
Gene Expression ◽  
Stem Cells ◽  
Gene Expression Data ◽  
Pluripotent Stem Cells ◽  
Reference Genes ◽  
Cell Types ◽  
Human Pluripotent Stem Cells ◽  
Expression Data ◽  
Large Variability ◽  
The Stability

Reference genes, often referred to as housekeeping genes (HKGs), are frequently used to normalize gene expression data based on the assumption that they are expressed at a constant level in the cells. However, several studies have shown that there may be a large variability in the gene expression levels of HKGs in various cell types. In a previous study, employing human embryonic stem cells (hESCs) subjected to spontaneous differentiation, we observed that the expression of commonly used HKG varied to a degree that rendered them inappropriate to use as reference genes under those experimental settings. Here we present a substantially extended study of the HKG signature in human pluripotent stem cells (hPSC), including nine global gene expression datasets from both hESC and human induced pluripotent stem cells, obtained during directed differentiation toward endoderm-, mesoderm-, and ectoderm derivatives. Sets of stably expressed genes were compiled, and a handful of genes (e.g., EID2, ZNF324B, CAPN10, and RABEP2) were identified as generally applicable reference genes in hPSCs across all cell lines and experimental conditions. The stability in gene expression profiles was confirmed by reverse transcription quantitative PCR analysis. Taken together, the current results suggest that differentiating hPSCs have a distinct HKG signature, which in some aspects is different from somatic cell types, and underscore the necessity to validate the stability of reference genes under the actual experimental setup used. In addition, the novel putative HKGs identified in this study can preferentially be used for normalization of gene expression data obtained from differentiating hPSCs.

Stabilization of the p53 transformation-related protein in mouse fibrosarcoma cell lines: effects of protein sequence and intracellular environment

1989 ◽  
Vol 9 (8) ◽  
pp. 3385-3392
Author(s):  
O Halevy ◽  
A Hall ◽  
M Oren
Keyword(s):  
Cell Lines ◽  
Primary Structure ◽  
P53 Protein ◽  
Cell Types ◽  
Stable Complex ◽  
Related Protein ◽  
Fibrosarcoma Cell ◽  
Mouse Tumors ◽  
Cellular Environment ◽  
The Stability

The transformation-related protein p53 is normally very labile. The stability of p53 is significantly increased in a number of fibrosarcoma cell lines derived from mouse tumors induced by treatment with physical or chemical agents. In many instances, p53 stabilization is correlated with the ability to form a stable complex with the heat shock protein cognate hsc70. We describe a line in which p53 is very stable yet has no detectable interaction with hsc70. The inability to form such a complex probably resides in the primary structure of the endogenous p53, since introduction of other p53 variants into those cells resulted in the appearance of a p53-hsc70 complex. The factors affecting p53 stability were investigated by stable transfection experiments. The results indicated that the primary structure of the p53 protein is a major determinant of its turnover rate; different p53 variants were degraded at distinct and characteristic rates in a number of transformed cell types. However, at least one p53 variant was degraded differently in nontransformed BALB/c-3T3 than in transformed fibrosarcoma cells, demonstrating that the specific cellular environment can also affect the stability of p53.

Formulation of “Stability Equations” and Derivation of New Constructions with Complete Systems of Design-formulae for Variable-speed Control Mechanisms

1953 ◽  
Vol 167 (1) ◽  
pp. 319-339
Author(s):  
M. S. Frenkel
Keyword(s):  
Nuclear Physics ◽  
Characteristic Curve ◽  
Mathematical Formulation ◽  
Control Mechanisms ◽  
Variable Speed ◽  
Speed Governor ◽  
Minimum Number ◽  
Order Of Magnitude ◽  
The Stability ◽  
Stable Characteristic

Requirements for stability are formulated mathematically and, through the “transformatory operations of mathematics”, yield a series of “stability equations” of ascending order which are generally applicable, for example to control mechanisms, electronics†, nuclear physics, etc. From these stability equations, the equation of the stable characteristic curve of a governor, and the differential equations of the oscillations of a governor-engine system, are derived. It emerges that the first part of the new oscillatory equation is identical with the whole of the differential equation in the literature to date (unchanged since Maxwell 1868)‡, while the important second part, which consists of terms of the same order of magnitude as the first part and which is the only one containing the equation of the stable characteristic curve, is lacking in literature. The stability equations classify all possible constructions of variable-speed governor according to “order of stability”, which signifies important operating properties. This classification accounts for the known shortcomings of conventional types. The stability equations, combined with the mathematical formulation of practical requirements (speed-adjustment with only one actuating motion, etc.), lead to new basic types of variable-speed governor, with complete systems of design equations. In addition to determining all unknown dimensions, this set of equations is important because it derives constructions of which the complexity increases with order of stability and, furthermore, a simple construction which provides any required high order of stability with the minimum number of adjustable components.

scholarly journals Knee mechanisms for through-knee prostheses

1983 ◽  
Vol 7 (2) ◽  
pp. 107-112 ◽  
Author(s):  
K. Öberg
Keyword(s):  
Stance Phase ◽  
Stability Diagram ◽  
Phase Control ◽  
Swing Phase ◽  
Control Mechanisms ◽  
Knee Prostheses ◽  
Heavy Duty ◽  
Linkage Mechanism ◽  
The Stability

The most widely used knee mechanisms for through-knee amputees can be characterized as three principal types of design. These types are metal side bars with heavy duty joints, conventional knee mechanisms for above-knee amputees and special polycentric linkage mechanisms for through-knee amputees. An investigation in Sweden in 1979 showed that over 50% of the fittings were using the special polycentric linkage mechanisms for through-knee amputees. The stability diagram illustrates how voluntary and involuntary stability can be utilized by using different polycentric linkage mechanisms for through-knee amputees. The polycentric linkage mechanism can be designed for different stance phase characteristics as well as incorporation of different swing phase control mechanisms. The cosmesis of the available designs is acceptable but there is need for lighter and more compact designs especially for the young and small amputee.

scholarly journals Interaction between Polycomb and SSX Proteins in Pericentromeric Heterochromatin Function and Its Implication in Cancer

Cells ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 226
Author(s):  
Simone Johansen ◽  
Morten Frier Gjerstorff
Keyword(s):  
Immune Deficiency ◽  
Tumor Biology ◽  
Pericentromeric Heterochromatin ◽  
Control Mechanisms ◽  
Malignant Cells ◽  
Polycomb Proteins ◽  
The Stability ◽  
Polycomb Bodies ◽  
Insight Into ◽  
Cancer Testis

The stability of pericentromeric heterochromatin is maintained by repressive epigenetic control mechanisms, and failure to maintain this stability may cause severe diseases such as immune deficiency and cancer. Thus, deeper insight into the epigenetic regulation and deregulation of pericentromeric heterochromatin is of high priority. We and others have recently demonstrated that pericentromeric heterochromatin domains are often epigenetically reprogrammed by Polycomb proteins in premalignant and malignant cells to form large subnuclear structures known as Polycomb bodies. This may affect the regulation and stability of pericentromeric heterochromatin domains and/or the distribution of Polycomb factors to support tumorigeneses. Importantly, Polycomb bodies in cancer cells may be targeted by the cancer/testis-related SSX proteins to cause derepression and genomic instability of pericentromeric heterochromatin. This review will discuss the interplay between SSX and Polycomb factors in the repression and stability of pericentromeric heterochromatin and its possible implications for tumor biology.

Multimaterial and Multiscale Three-Dimensional Bioprinter

2015 ◽  
Vol 6 (2) ◽  
Author(s):  
Jennifer Campbell ◽  
Ian McGuinness ◽  
Holger Wirz ◽  
Andre Sharon ◽  
Alexis F. Sauer-Budge
Keyword(s):  
Mammalian Cell Culture ◽  
Life Sciences ◽  
Three Dimensional ◽  
Cell Types ◽  
3D Bioprinting ◽  
Design And Implementation ◽  
Multiple Cell ◽  
Multiple Materials ◽  
Printed Materials ◽  
The Stability

We have developed a three-dimensional (3D) bioprinting system capable of multimaterial and multiscale deposition to enable the next generation of “bottom-up” tissue engineering. This area of research resides at the interface of engineering and life sciences. As such, it entails the design and implementation of diverse elements: a novel hydrogel-based bioink, a 3D bioprinter, automation software, and mammalian cell culture. Our bioprinter has three components uniquely combined into a comprehensive tool: syringe pumps connected to a selector valve that allow precise application of up to five different materials with varying viscosities and chemistries, a high velocity/high-precision x–y–z stage to accommodate the most rapid speeds allowable by the printed materials, and temperature control of the bioink reservoirs, lines, and printing environment. Our custom-designed bioprinter is able to print multiple materials (or multiple cell types in the same material) concurrently with various feature sizes (100 μm–1 mm wide; 100 μm–1 cm high). One of these materials is a biocompatible, printable bioink that has been used to test for cell survival within the hydrogel following printing. Hand-printed (HP) controls show that our bioprinter does not adversely affect the viability of the printed cells. Here, we report the design and build of the 3D bioprinter, the optimization of the bioink, and the stability and viability of our printed constructs.

scholarly journals Genome-Wide Analysis of Human MicroRNA Stability

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Yang Li ◽  
Zhixin Li ◽  
Shixin Zhou ◽  
Jinhua Wen ◽  
Bin Geng ◽  
...  
Keyword(s):  
Cell Types ◽  
Biological Molecules ◽  
Expression Level ◽  
Action Mode ◽  
Status Transition ◽  
Genome Wide ◽  
Mirna Expression Level ◽  
High Dynamics ◽  
The Stability ◽  
Slow Turnover

Increasing studies have shown that microRNA (miRNA) stability plays important roles in physiology. However, the global picture of miRNA stability remains largely unknown. Here, we had analyzed genome-wide miRNA stability across 10 diverse cell types using miRNA arrays. We found that miRNA stability shows high dynamics and diversity both within individual cells and across cell types. Strikingly, we observed a negative correlation between miRNA stability and miRNA expression level, which is different from current findings on other biological molecules such as proteins and mRNAs that show positive and not negative correlations between stability and expression level. This finding indicates that miRNA has a distinct action mode, which we called “rapid production, rapid turnover; slow production, slow turnover.” This mode further suggests that high expression miRNAs normally degrade fast and may endow the cell with special properties that facilitate cellular status-transition. Moreover, we revealed that the stability of miRNAs is affected by cohorts of factors that include miRNA targets, transcription factors, nucleotide content, evolution, associated disease, and environmental factors. Together, our results provided an extensive description of the global landscape, dynamics, and distinct mode of human miRNA stability, which provide help in investigating their functions in physiology and pathophysiology.

scholarly journals A novel method to enhance the sensitivity of marker detection using a refined hierarchical prior of tissue similarities

2015 ◽  
Author(s):  
Shahin Mohammadi ◽  
Ananth Grama
Keyword(s):  
Immune Cells ◽  
Statistical Approach ◽  
Signal To Noise Ratio ◽  
Cell Types ◽  
Detection Methods ◽  
Control Mechanisms ◽  
Tissue Specific ◽  
Cellular Machinery ◽  
Marker Detection ◽  
Brain Tissues

Identification of biochemical processes that drive the transformation of a totipotent cell into various cell types is essential to our understanding of living systems. This complex machinery determines how tissues differ in terms of their anatomy, physiology, morphology, and, more importantly, how various cellular control mechanisms contribute to the observed similarities/ differences. Tissue-selective genes orchestrate various aspects of cellular machinery in different tissues, and are known to be implicated in a number of tissue-specific pathologies. We propose a novel statistical approach that identifies and removes the effect of universally expressed genes in groups of tissues. This allows us to better characterize tissue similarities, as well as to identify tissue-selective genes. We use our method to construct a reliable hierarchy of tissue similarities. The groupings of tissues in this hierarchy are used to specify successively refined priors for identifying tissue-selective functions and their corresponding genes in the reduced subspace. We show that our refinement process enhances the signal-to-noise ratio in the identification of markers. Using case studies of immune cells and brain tissues, we show that our approach significantly outperforms the state-of-the-art methods, both in terms of coverage and reliability of the predicted tissue-selective genes. Our statistical approach provides a general framework for enhancing the sensitivity of marker detection methods, which can be used in conjunction with other techniques. Even in cases where the number of available expression datasets is limited, we show that our marker detection method outperforms existing techniques. We present detailed validation on immune cells and brain tissues in this paper. Our approach can be applied to construct similar datasets of other human tissues as well, for identifying tissue-specific genes. We demonstrate how these tissue-selective genes enhance our understanding of differentiating biochemical features of brain tissues, shed light on how tissue-selective pathologies progress, and help us identify specific biomarkers and targets for future interventions.

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