scholarly journals A novel flatworm-specific gene family implicated in reproduction in Macrostomum lignano

2017 ◽  
Author(s):  
Magda Grudniewska ◽  
Stijn Mouton ◽  
Margriet Grelling ◽  
Anouk H. G. Wolters ◽  
Jeroen Kuipers ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Stem Cells ◽  
Gene Family ◽  
Model Organisms ◽  
Future Research ◽  
Specific Gene ◽  
Free Living ◽  
Ultrastructural Studies ◽  
Conserved Genes ◽  
High Fraction

AbstractFree-living flatworms, such as the planarian Schmidtea mediterranea, are extensively used as model organisms to study stem cells and regeneration. The majority of studies in planarians so far focused on broadly conserved genes. However, investigating what makes these animals different might be equally informative for understanding its biology. Here, we present a re-analysis of neoblast and germline transcriptional signatures in the flatworm M. lignano and combine it with the whole-animal electron microscopy atlas (nanotomy) as a reference platform for ultrastructural studies in M. lignano. We show that germline-enriched genes have a high fraction of flatworm-specific genes and identify Mlig-sperm1 gene as a member of a novel gene family conserved only in free-living flatworms and essential for producing healthy spermatozoa. This work demonstrates that investigation of flatworm-specific genes is crucial for understanding flatworm biology and establishes a basis for future research in this direction in M. lignano.

scholarly journals Tendon Stem/Progenitor Cells and Their Interactions with Extracellular Matrix and Mechanical Loading

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Chuanxin Zhang ◽  
Jun Zhu ◽  
Yiqin Zhou ◽  
Bhavani P. Thampatty ◽  
James H-C. Wang
Keyword(s):  
Stem Cells ◽  
Extracellular Matrix ◽  
Progenitor Cells ◽  
Mechanical Loading ◽  
Gene Knockout ◽  
Deep Understanding ◽  
Future Research ◽  
Specific Gene

Tendons are unique connective tissues in the sense that their biological properties are largely determined by their tendon-specific stem cells, extracellular matrix (ECM) surrounding the stem cells, mechanical loading conditions placed on the tendon, and the complex interactions among them. This review is aimed at providing an overview of recent advances in the identification and characterization of tendon stem/progenitor cells (TSPCs) and their interactions with ECM and mechanical loading. In addition, the effects of such interactions on the maintenance of tendon homeostasis and the initiation of tendon pathological conditions are discussed. Moreover, the challenges in further investigations of TSPC mechanobiology in vitro and in vivo are outlined. Finally, future research efforts are suggested, which include using specific gene knockout models and single-cell transcription profiling to enable a broad and deep understanding of the physiology and pathophysiology of tendons.

Electron microscopy of endocardial cell populations

1978 ◽  
Vol 36 (2) ◽  
pp. 486-487
Author(s):  
T. G. Sarphie ◽  
C. R. Comer ◽  
D. J. Allen
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Cellular Transformation ◽  
Cell Populations ◽  
Cell Surfaces ◽  
Kb Cells ◽  
Dna Viruses ◽  
Cell Cycles ◽  
Ultrastructural Studies ◽  
Endocardial Cell

Previous ultrastructural studies have characterized surface morphology during norma cell cycles in an attempt to associate specific changes with specific metabolic processes occurring within the cell. It is now known that during the synthetic ("S") stage of the cycle, when DNA and other nuclear components are synthesized, a cel undergoes a doubling in volume that is accompanied by an increase in surface area whereby its plasma membrane is elaborated into a variety of processes originally referred to as microvilli. In addition, changes in the normal distribution of glycoproteins and polysaccharides derived from cell surfaces have been reported as depreciating after cellular transformation by RNA or DNA viruses and have been associated with the state of growth, irregardless of the rate of proliferation. More specifically, examination of the surface carbohydrate content of synchronous KB cells were shown to be markedly reduced as the cell population approached division Comparison of hamster kidney fibroblasts inhibited by vinblastin sulfate while in metaphase with those not in metaphase demonstrated an appreciable decrease in surface carbohydrate in the former.

Selection and Preparation of Specific Tissue Regions For Tem Using Large Epoxy-Embedded Blocks

1973 ◽  
Vol 31 ◽  
pp. 324-325 ◽  
Author(s):  
P. M. Lowrie ◽  
W. S. Tyler
Keyword(s):  
Electron Microscopy ◽  
Anatomical Structures ◽  
Ultrastructural Studies ◽  
Transmission Electron ◽  
Microscopic Evaluation ◽  
Embedded Blocks ◽  
Specific Tissue ◽  
Definition Of ◽  
Areas Of Interest ◽  
Selection Of

The importance of examining stained 1 to 2μ plastic sections by light microscopy has long been recognized, both for increased definition of many histologic features and for selection of specimen samples to be used in ultrastructural studies. Selection of specimens with specific orien ation relative to anatomical structures becomes of critical importance in ultrastructural investigations of organs such as the lung. The uantity of blocks necessary to locate special areas of interest by random sampling is large, however, and the method is lacking in precision. Several methods have been described for selection of specific areas for electron microscopy using light microscopic evaluation of paraffin, epoxy-infiltrated, or epoxy-embedded large blocks from which thick sections were cut. Selected areas from these thick sections were subsequently removed and re-embedded or attached to blank precasted blocks and resectioned for transmission electron microscopy (TEM).

Adenomatoid Tumor of the Testis, A Mesonephric Hamartoma

1971 ◽  
Vol 29 ◽  
pp. 318-319
Author(s):  
Raoul Fresco ◽  
Mary Chang-Lo
Keyword(s):  
Electron Microscopy ◽  
Epithelial Cells ◽  
Fibrous Tissue ◽  
Salient Feature ◽  
Luminal Surface ◽  
Adenomatoid Tumor ◽  
Ultrastructural Studies ◽  
Epithelial Origin ◽  
Brush Borders ◽  
Cell Processes

Confusion surrounds the nature of the “adenomatoid tumor” of the testis, as evidenced by the large number of synonyms which have been ascribed to it. Various authors have considered the tumor to be of endothelial, mesothelial or epithelial origin. There appears to be no controversy as to the stromal elements of the tumor, which consists mainly of smooth muscle and fibrous tissue. It is the irregular gland-like spaces which have given rise to the numerous theories as to its histogenesis, and even recent ultrastructural studies fail to agree on the origin of these structures.Electron microscopy of a typical intrascrotal adenomatoid tumor showed the gland-like spaces to be lined by epithelial cells (Fig. 1), rich in cytoplasmic tonofibrils and united to each other by numerous desmosomes (Fig. 2). The most salient feature of these epithelial cells was the presence on their luminal surface of numerous long and repeatedly branching microvillous structures of the type known as stereocilia (Fig. 3). These are extremely long slender cell processes which are as much as three to four times the length of those in brush borders.

Ultrastructural studies of the relationship between actin filaments and secretory granules

1990 ◽  
Vol 48 (3) ◽  
pp. 458-459
Author(s):  
Ellen Holm Nielsen
Keyword(s):  
Electron Microscopy ◽  
Colloidal Gold ◽  
Actin Filaments ◽  
Secretory Granules ◽  
Secretory Cells ◽  
Ultrastructural Studies ◽  
Transmission Electron ◽  
Granule Membrane ◽  
Ultrathin Sections ◽  
Lowicryl K4m

In secretory cells a dense and complex network of actin filaments is seen in the subplasmalemmal space attached to the cell membrane. During exocytosis this network is undergoing a rearrangement facilitating access of granules to plasma membrane in order that fusion of the membranes can take place. A filamentous network related to secretory granules has been reported, but its structural organization and composition have not been examined, although this network may be important for exocytosis.Samples of peritoneal mast cells were frozen at -70°C and thawed at 4°C in order to rupture the cells in such a gentle way that the granule membrane is still intact. Unruptured and ruptured cells were fixed in 2% paraformaldehyde and 0.075% glutaraldehyde, dehydrated in ethanol. For TEM (transmission electron microscopy) cells were embedded in Lowicryl K4M at -35°C and for SEM (scanning electron microscopy) they were placed on copper blocks, critical point dried and coated. For immunoelectron microscopy ultrathin sections were incubated with monoclonal anti-actin and colloidal gold labelled IgM. Ruptured cells were also placed on cover glasses, prefixed, and incubated with anti-actin and colloidal gold labelled IgM.

Conformational characterization of nucleosome structure by Electron Microscopy

1993 ◽  
Vol 51 ◽  
pp. 194-195
Author(s):  
Gregory J. Czarnota
Keyword(s):  
Electron Microscopy ◽  
Structural Changes ◽  
Physiological State ◽  
Gene Activation ◽  
Three Dimensional ◽  
Macromolecular Complex ◽  
Ultrastructural Studies ◽  
Ionic Environment ◽  
Nucleosome Structure ◽  
Dimensional Reconstruction

Chromatin structure at the fundamental level of the nucleosome is important in vital cellular processes. Recent biochemical and genetic analyses show that nucleosome structure and structural changes are very active participants in gene expression, facilitating or inhibiting transcription and reflecting the physiological state of the cell. Structural states and transitions for this macromolecular complex, composed of DNA wound about a heterotypic octamer of variously modified histone proteins, have been measured by physico-chemical techniques and by enzyme-accessibility and are recognized to occur with various post-translational modifications, gene activation, transformation and with ionic-environment. In spite of studies which indicate various forms of nucleosome structure, all current x-ray and neutron diffraction studies have consistently resulted in only one structure, suggestive of a static conformation. In contrast, two-dimensional electron microscopy studies and three-dimensional reconstruction techniques have yielded different structures. These fundamental differences between EM and other ultrastructural studies have created a long standing quandary, which I have addressed and resolved using spectroscopic electron microscopy and statistical analyses of nucleosome images in a study of nucleosome structure with ionic environment.

CRYO-Electron Microscopy of the Acto-Myosin-ATP Complex

1990 ◽  
Vol 48 (1) ◽  
pp. 248-249
Author(s):  
John Trinickt ◽  
Howard White
Keyword(s):  
Electron Microscopy ◽  
Atp Hydrolysis ◽  
Myosin Head ◽  
Bound State ◽  
Cross Linking ◽  
Weakly Bound ◽  
Cryo Electron Microscopy ◽  
Myosin Subfragment 1 ◽  
Attached State ◽  
High Fraction

The primary force of muscle contraction is thought to involve a change in the myosin head whilst attached to actin, the energy coming from ATP hydrolysis. This change in attached state could either be a conformational change in the head or an alteration in the binding angle made with actin. A considerable amount is known about one bound state, the so-called strongly attached state, which occurs in the presence of ADP or in the absence of nucleotide. In this state, which probably corresponds to the last attached state of the force-producing cycle, the angle between the long axis myosin head and the actin filament is roughly 45°. Details of other attached states before and during power production have been difficult to obtain because, even at very high protein concentration, the complex is almost completely dissociated by ATP. Electron micrographs of the complex in the presence of ATP have therefore been obtained only after chemically cross-linking myosin subfragment-1 (S1) to actin filaments to prevent dissociation. But it is unclear then whether the variability in attachment angle observed is due merely to the cross-link acting as a hinge.We have recently found low ionic-strength conditions under which, without resorting to cross-linking, a high fraction of S1 is bound to actin during steady state ATP hydrolysis. The structure of this complex is being studied by cryo-electron microscopy of hydrated specimens. Most advantages of frozen specimens over ambient temperature methods such as negative staining have already been documented. These include improved preservation and fixation rates and the ability to observe protein directly rather than a surrounding stain envelope. In the present experiments, hydrated specimens have the additional benefit that it is feasible to use protein concentrations roughly two orders of magnitude higher than in conventional specimens, thereby reducing dissociation of weakly bound complexes.

Stem Cell-Based Therapies: A New Ray of Hope for Diabetic Patients

2019 ◽  
Vol 14 (2) ◽  
pp. 146-151 ◽  
Author(s):  
Junaid Khan ◽  
Amit Alexander ◽  
Mukta Agrawal ◽  
Ajazuddin ◽  
Sunil Kumar Dubey ◽  
...  
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Drug Therapy ◽  
Type I Diabetes ◽  
Embryonic Stem ◽  
Health Concern ◽  
Future Research ◽  
Diabetic Patients ◽  
Successful Implementation ◽  
Type I

Diabetes and its complications are a significant health concern throughout the globe. There are physiological differences in the mechanism of type-I and type-II diabetes and the conventional drug therapy as well as insulin administration seem to be insufficient to address the problem at large successfully. Hypoglycemic swings, frequent dose adjustments and resistance to the drug are major problems associated with drug therapy. Cellular approaches through stem cell based therapeutic interventions offer a promising solution to the problem. The need for pancreatic transplants in case of Type- I diabetes can also be by-passed/reduced due to the formation of insulin producing β cells via stem cells. Embryonic Stem Cells (ESCs) and induced Pluripotent Stem Cells (iPSCs), successfully used for generating insulin producing β cells. Although many experiments have shown promising results with stem cells in vitro, their clinical testing still needs more exploration. The review attempts to bring into light the clinical studies favoring the transplantation of stem cells in diabetic patients with an objective of improving insulin secretion and improving degeneration of different tissues in response to diabetes. It also focuses on the problems associated with successful implementation of the technique and possible directions for future research.

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