scholarly journals Thrombosis: A Function of Surface Charge and/or Chemistry of Collagen

1977 ◽  
Author(s):  
P. Sawyer ◽  
B. Stanczewskl ◽  
R. Stillman ◽  
D. Kirschenbaum ◽  
S. Sivakoff ◽  
...  
Keyword(s):  
Physical Examination ◽  
Surface Charge ◽  
Thrombus Formation ◽  
Human Umbilical Cord ◽  
Neutral Surface ◽  
Cell Type ◽  
Improved Performance ◽  
And Function ◽  
Charge Configuration

Examination of porcine prosthesis and bovine heterografts using histologic, SEM and physical examination revealed that ; (1) they have a measurable half life in terms of function; (2) the areas of failure are predictable; (3) the structure of the observed thrombus is unusual.A number of collagen and human umbilical cord prostheses were prepared by bonding a variety of aliphatic acids to the helical polypetide collagen side chains to produce a repeating surface chemistry. The control (fresh or ficin digested collagen) was compared to (i) glutaraldehyde tanned (GT)(-) charged, (ii) GT plus (+) charged and (iii) GT neutral surface. These resulting tubular grafts were implanted in dog carotid and femoral arteries.The results indicate the most important factor in long term patency and function is a coval-ently bonded, GT (-) surface.Histologic examination reveals that manipulation of the surface charge of collagen results in bizarre thrombus formation with aggregation of a singie cell type or protein element.The (-) charged grafts were free from thrombus. Control collagen grafts contained classical fibrinogen and cellular thrombus. The (+) charged grafts had a pseudo-thrombus i.e. increased fibrinogen fragments (& B) monomers plus trapped cell deposition. The neutral grafts had a less dense, branched fibrinogen deposit with some celluiar elements.In summary, the structural, chemical and surface charge configuration of collagen can be manipulated to produce a biological cardiovascular prosthesis with improved performance.

scholarly journals Cellularized small-caliber tissue-engineered vascular grafts: looking for the ultimate gold standard

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Adrien Fayon ◽  
Patrick Menu ◽  
Reine El Omar
Keyword(s):  
Vascular Tissue ◽  
Vascular Grafts ◽  
Cell Types ◽  
Cell Type ◽  
Critical Approach ◽  
Promising Solution ◽  
Intimal Layer ◽  
And Function ◽  
The Ideal

AbstractDue to the lack of efficacy of synthetic vascular substitutes in the replacement of small-caliber arteries, vascular tissue engineering (VTE) has emerged as a promising solution to produce viable small-caliber tissue-engineered vascular grafts (TEVG). Previous studies have shown the importance of a cellular intimal layer at the luminal surface of TEVG to prevent thrombotic events. However, the cellularization of a TEVG seems to be a critical approach to consider in the development of a TEVG. To date, no standard cellularization method or cell type has been established to create the ideal TEVG by promoting its long-term patency and function. In this review, advances in VTE are described and discussed with a particular focus on the construction approaches of cellularized small-caliber TEVGs, the cell types used, as well as their preclinical and clinical applications.

Clues for Understanding the Structure and Function of a Prototypic Human Integrin: The Platelet Glycoprotein IIb/IIIa Complex

1994 ◽  
Vol 72 (01) ◽  
pp. 001-015 ◽  
Author(s):  
Juan J Calvete
Keyword(s):  
Structure Function ◽  
Thrombus Formation ◽  
Platelet Glycoprotein ◽  
Primary Role ◽  
Clot Retraction ◽  
Inhibitory Peptide ◽  
Rgd Sequence ◽  
Platelet Receptor ◽  
Adhesive Proteins ◽  
And Function

SummaryThe glycoprotein (GP) IIb/IIIa, a Ca2+-dependent heterodimer, is the major integrin on the platelet plasma membrane. On resting platelets GPIIb/IIIa is maintained in an inactive conformation and serves as a low affinity adhesion receptor for surface-coated fibrinogen, whereas upon platelet activation signals within the cytoplasma alter the receptor function of GPIIb/IIIa (inside-out signalling), which undergoes a measurable conformational change within its exoplasmic domains, and becomes a competent receptor for soluble fibrinogen and some other RGD sequence-containing plasma adhesive proteins. Upon ligand binding, further structural alterations trigger the association of receptor-occupied GPIIb/IIIa complexes with themselves within the plane of the membrane. The simultaneous binding of dimeric fibrinogen molecules to GPIIb/IIIa clusters on adjacent platelets leads to platelet aggregation, which promotes attachment of fibrinogen-GPIIb/IIIa clusters to the cytoskeleton (outside-in signalling). This, in turn, provides the necessary physical link for clot retraction to occur, and generates a cascade of intracellular biochemical reactions which result in the formation of a multiprotein signalling complex at the cytoplasmic domains of GPIIb/IIIa. Glycoprotein IMIIa, also called αIIbβ3 in the integrin nomenclature, plays thus a primary role in both platelet adhesion and thrombus formation at the site of vascular injury. In addition, the human glycoprotein Ilb/IIIa complex is the most thoroughly studied integrin receptor, its molecular biology and major features of its primary structure having been elucidated mainly during the last six years. Furthermore, localization of functionally relevant monoclonal antibody epitopes, determination of the cross-linking sites of inhibitory peptide ligands, proteolytic dissection of the isolated integrin, and analysis of natural and artificial GPIIb/IIIa mutants have recently provided a wealth of information regarding structure-function relationships of human GPIIb/IIIa. The aim of this review is to summarize these many structural and functional data in the perspective of an emerging model. Although most of the interpretations based on structural elements of this initial biochemical model require independent confirmation, they may help us to understand the structure-function relationship of this major platelet receptor, and of other members of the integrin superfamily, as well as to perform further investigations in order to test current hypotheses.

Platelet Suruival and Function in Rats with Enhanced Thrombotic Tendency

1985 ◽  
Vol 54 (04) ◽  
pp. 739-743 ◽  
Author(s):  
Federica Delaini ◽  
Elisabetta Dejana ◽  
Ine Reyers ◽  
Elisa Vicenzi ◽  
Germana De Bellis Vitti ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Nephrotic Syndrome ◽  
Platelet Function ◽  
Laboratory Tests ◽  
Thrombus Formation ◽  
The Other ◽  
Mean Survival Time ◽  
The Mean ◽  
And Function ◽  
Thrombotic Tendency

SummaryWe have investigated the relevance of some laboratory tests of platelet function in predicting conditions of thrombotic tendency. For this purpose, we studied platelet survival, platelet aggregation in response to different stimuli, TxB2 and 6-keto-PGFlα production in serum of rats bearing a nephrotic syndrome induced by adriamycin. These animals show a heavy predisposition to the development of both arterial and venous thrombosis. The mean survival time was normal in nephrotic rats in comparison to controls. As to aggregation tests, a lower aggregating response was found in ADR-treated rats using ADP or collagen as stimulating agents. With arachidonic acid (AA) we observed similar aggregating responses at lower A A concentrations, whereas at higher AA concentrations a significantly lower response was found in nephrotic rats, despite their higher TxB2 production. Also TxB2 and 6-keto-PGFlα levels in serum of nephrotic rats were significantly higher than in controls. No consistent differences were found in PGI2-activity generated by vessels of control or nephrotic rats.These data show that platelet function may appear normal or even impaired in rats with a markedly increased thrombotic tendency. On the other hand, the significance of high TxB2 levels in connection with mechanisms leading to thrombus formation remains a controversial issue.

Bleaching optimization at WestRock mill in Covington, Virginia

TAPPI Journal ◽  
2016 ◽  
Vol 15 (9) ◽  
pp. 581-586 ◽  
Author(s):  
RICARDO B. SANTOS ◽  
PETER W. HART ◽  
DOUGLAS C. PRYKE ◽  
JOHN VANDERHEIDE
Keyword(s):  
Hydrogen Peroxide ◽  
Sodium Hydroxide ◽  
Chlorine Dioxide ◽  
Capital Expenditures ◽  
Equipment Repair ◽  
Optimization Program ◽  
Hardwood Pulp ◽  
Improved Performance

The WestRock mill in Covington, VA, USA, initiated a long term diagnostic and optimization program for all three of its bleaching lines. Benchmarking studies were used to help identify optimization opportunities. Capital expenditures for mixing improvement, filtrate changes, equipment repair, other equipment changes, and species changes were outside the scope of this work. This focus of this paper is the B line, producing southern hardwood pulp in a D(EP)DD sequence at 88% GE brightness. The benchmarking study and optimization work identified the following opportunities for improved performance: nonoptimal addition of caustic and hydrogen peroxide to the (EP) stage, carryover of D0 filtrate to the (EP) stage, and carryover of (EP) filtrate to the D1 stage. As a result of actions the mill undertook to address these opportunities, D0 kappa factor decreased about 5%, sodium hydroxide consumption in the (EP) stage decreased about 35%, chlorine dioxide consumption in the D1 stage decreased about 25%, and overall bleaching cost decreased about 15%.

scholarly journals Differential Regulation of Gonadotropins as Revealed by Transcriptomes of Distinct LH and FSH Cells of Fish Pituitary

2021 ◽  
Vol 22 (12) ◽  
pp. 6478
Author(s):  
Lian Hollander-Cohen ◽  
Matan Golan ◽  
Berta Levavi-Sivan
Keyword(s):  
Follicle Stimulating Hormone ◽  
Differential Regulation ◽  
Receptor Expression ◽  
Hormone Regulation ◽  
Fish Reproduction ◽  
Cell Type ◽  
Conserved Genes ◽  
Transgenic Tilapia ◽  
And Function ◽  
Direct Regulation

From mammals to fish, reproduction is driven by luteinizing hormone (LH) and follicle-stimulating hormone (FSH) temporally secreted from the pituitary gland. Teleost fish are an excellent model for addressing the unique regulation and function of each gonadotropin cell since, unlike mammals, they synthesize and secrete LH and FSH from distinct cells. Only very distant vertebrate classes (such as fish and birds) demonstrate the mono-hormonal strategy, suggesting a potential convergent evolution. Cell-specific transcriptome analysis of double-labeled transgenic tilapia expressing GFP and RFP in LH or FSH cells, respectively, yielded genes specifically enriched in each cell type, revealing differences in hormone regulation, receptor expression, cell signaling, and electrical properties. Each cell type expresses a unique GPCR signature that reveals the direct regulation of metabolic and homeostatic hormones. Comparing these novel transcriptomes to that of rat gonadotrophs revealed conserved genes that might specifically contribute to each gonadotropin activity in mammals, suggesting conserved mechanisms controlling the differential regulation of gonadotropins in vertebrates.

scholarly journals Engineering Sr-doping for enabling long-term stable FAPb1−xSrxI3 quantum dots with 100% photoluminescence quantum yield

2021 ◽  
Vol 9 (5) ◽  
pp. 1555-1566
Author(s):  
Andrés F. Gualdrón-Reyes ◽  
David F. Macias-Pinilla ◽  
Sofia Masi ◽  
Carlos Echeverría-Arrondo ◽  
Said Agouram ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Quantum Yield ◽  
Toxic Metals ◽  
Environmentally Friendly ◽  
Photoluminescence Quantum Yield ◽  
Improved Performance ◽  
Pb Substitution

The Pb substitution in quantum dots (PQDs) with lesser toxic metals has been widely searched to be environmentally friendly, and be of comparable or improved performance compared to the lead-perovskite.

scholarly journals Climate Mobility and Development Cooperation

2021 ◽  
Author(s):  
Robert Stojanov ◽  
Sarah Rosengaertner ◽  
Alex de Sherbinin ◽  
Raphael Nawrotzki
Keyword(s):  
Climate Adaptation ◽  
Human Mobility ◽  
Climate Impacts ◽  
Development Cooperation ◽  
Climate Variability And Change ◽  
Policy Frameworks ◽  
And Migration ◽  
And Function ◽  
Role And Function

AbstractDevelopment cooperation actors have been addressing climate change as a cross-cutting issue and investing in climate adaptation projects since the early 2000s. More recently, as concern has risen about the potential impacts of climate variability and change on human mobility, development cooperation actors have begun to design projects that intentionally address the drivers of migration, including climate impacts on livelihoods. However, to date, we know little about the development cooperation’s role and function in responding to climate related mobility and migration. As such, the main aim of this paper is to outline the policy frameworks and approaches shaping development cooperation actors’ engagement and to identify areas for further exploration and investment. First, we frame the concept of climate mobility and migration and discuss some applicable policy frameworks that govern the issue from various perspectives; secondly, we review the toolbox of approaches that development cooperation actors bring to climate mobility; and third, we discuss the implications of the current Covid-19 pandemic and identify avenues for the way forward. We conclude that ensuring safe and orderly mobility and the decent reception and long-term inclusion of migrants and displaced persons under conditions of more severe climate hazards, and in the context of rising nationalism and xenophobia, poses significant challenges. Integrated approaches across multiple policy sectors and levels of governance are needed. In addition to resources, development cooperation actors can bring data to help empower the most affected communities and regions and leverage their convening power to foster more coordinated approaches within and across countries.

scholarly journals Epigenetic reprogramming of cell identity: lessons from development for regenerative medicine

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Amitava Basu ◽  
Vijay K. Tiwari
Keyword(s):  
Regenerative Medicine ◽  
Cell Types ◽  
Direct Conversion ◽  
Cellular Reprogramming ◽  
Specific Cell ◽  
Cell Type ◽  
Pathological Conditions ◽  
Gene Regulatory ◽  
Induced Pluripotent ◽  
And Function

AbstractEpigenetic mechanisms are known to define cell-type identity and function. Hence, reprogramming of one cell type into another essentially requires a rewiring of the underlying epigenome. Cellular reprogramming can convert somatic cells to induced pluripotent stem cells (iPSCs) that can be directed to differentiate to specific cell types. Trans-differentiation or direct reprogramming, on the other hand, involves the direct conversion of one cell type into another. In this review, we highlight how gene regulatory mechanisms identified to be critical for developmental processes were successfully used for cellular reprogramming of various cell types. We also discuss how the therapeutic use of the reprogrammed cells is beginning to revolutionize the field of regenerative medicine particularly in the repair and regeneration of damaged tissue and organs arising from pathological conditions or accidents. Lastly, we highlight some key challenges hindering the application of cellular reprogramming for therapeutic purposes.

scholarly journals Nanoemulsions for the Encapsulation of Hydrophobic Actives

Cosmetics ◽  
2021 ◽  
Vol 8 (2) ◽  
pp. 45
Author(s):  
Eduardo Guzmán ◽  
Laura Fernández-Peña ◽  
Lorenzo Rossi ◽  
Mathieu Bouvier ◽  
Francisco Ortega ◽  
...  
Keyword(s):  
Surface Charge ◽  
Long Term Stability ◽  
Promising Tool ◽  
Oil In Water ◽  
Nanometric Range ◽  
Negative Surface ◽  
Negative Surface Charge ◽  
Highly Hydrophobic ◽  
Technological Interest

This work analyzes the dispersion of two highly hydrophobic actives, (9Z)-N-(1,3-dihydroxyoctadecan-2-yl)octadec-9-enamide (ceramidelike molecule) and 2,6-diamino-4-(piperidin-1-yl)pyrimidine 1-oxide (minoxidil), using oil-in-water nanoemulsions with the aim of preparing stable and safe aqueous-based formulations that can be exploited for enhancing the penetration of active compounds through cosmetic substrates. Stable nanoemulsions with a droplet size in the nanometric range (around 200 nm) and a negative surface charge were prepared. It was possible to prepare formulations containing up to 2 w/w% of ceramide-like molecules and more than 10 w/w% of minoxidil incorporated within the oil droplets. This emulsions evidenced a good long-term stability, without any apparent modification for several weeks. Despite the fact that this work is limited to optimize the incorporation of the actives within the nanoemulsion-like formulations, it demonstrated that nanoemulsions should be considered as a very promising tool for enhancing the distribution and availability of hydrophobic molecules with technological interest.

Sign in / Sign up

Export Citation Format

Share Document