Synthesis and material properties of elastomeric high molecular weight polycycloacetals derived from diglycerol and meso ‐erythritol

2019 ◽  
Vol 137 (23) ◽  
pp. 48780
Author(s):  
Ariah C. Law ◽  
Dakota S. Stankowski ◽  
Blake H. Bomann ◽  
Shanzay Suhail ◽  
Kyle H. Salmon ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Material Properties

Short-term creep and recovery behavior of medical grade ultra-high molecular weight polyethylene (UHMWPE)

2016 ◽  
Vol 78 (2) ◽  
pp. 65-70 ◽  
Author(s):  
F. Metin ◽  
M. Cengil
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Viscoelastic Material ◽  
Material Properties ◽  
Polymeric Materials ◽  
Tensile Creep ◽  
Short Term ◽  
Creep And Recovery ◽  
Ultra High Molecular Weight ◽  
Medical Grade

Purpose: In this study, short-term tensile creep and recovery behaviors of medical gradeultra-high molecular weight polyethylene (UHMWPE) were investigated to contributedeformation behaviour of UHMWPE components in knee and hip prosthesis during daily lifeactivities of patients.Design/methodology/approach: Tensile test specimens were machined fromcompression molded UHMWPE sheets having commercial brand name: Chirulen 1020 andthey were prepared according to ASTM 527-2. The tensile creep tests were performed atconstant stress levels of 5, 9, 13, 18 and 21 MPa as long as 1 hour for each test. Then, thespecimens were allowed to recover unloaded for 1 hour. Automatic extensometer was usedto measure the deformations precisely for each test.Findings: Results show that creep rate linearly increased with increasing the stress levels.Permanent deformations were observed after recovery. Recovery of the material becamedifficult with increasing the applied load at intended time interval.Research limitations/implications: UHMWPE components used in prosthesis havebeen subjected to complex loading conditions during service life. Polymeric materials showthe viscoelastic material properties like strain rate sensitivity, relaxation, creep and recoveryat room temperature. Because of the viscoelastic material properties of the UHMWPE,it makes difficult to predict the failure of the UHMWPE components in hip and knee prosthesis.Therefore, deformation behavior of medical grade UHMWPE should be investigated in manydifferent loading conditions.Practical implications: Medical grade ultra-high molecular weight polyethylene(UHMWPE) have been used commonly in total hip replacements as acetabular cup and intotal knee replacements as tibial insert since early 1960s.

Microtubule motors and other maps

1990 ◽  
Vol 48 (3) ◽  
pp. 1-1
Author(s):  
Richard B. Vallee
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Cytoplasmic Dynein ◽  
Organelle Transport ◽  
Structural Components ◽  
Microtubule Associated Proteins ◽  
Microtubule Motors ◽  
Associated Proteins ◽  
The Subject ◽  
Intracellular Motility

Microtubules are involved in a number of forms of intracellular motility, including mitosis and bidirectional organelle transport. Purified microtubules from brain and other sources contain tubulin and a diversity of microtubule associated proteins (MAPs). Some of the high molecular weight MAPs - MAP 1A, 1B, 2A, and 2B - are long, fibrous molecules that serve as structural components of the cytamatrix. Three MAPs have recently been identified that show microtubule activated ATPase activity and produce force in association with microtubules. These proteins - kinesin, cytoplasmic dynein, and dynamin - are referred to as cytoplasmic motors. The latter two will be the subject of this talk.Cytoplasmic dynein was first identified as one of the high molecular weight brain MAPs, MAP 1C. It was determined to be structurally equivalent to ciliary and flagellar dynein, and to produce force toward the minus ends of microtubules, opposite to kinesin.

Studies on the Functionality of Newly Synthesized Fibrinogen after Treatment of Acute Myocardial Infarction with Streptokinase, Increase in the Rate of Fibrinopeptide Release

1993 ◽  
Vol 70 (06) ◽  
pp. 0978-0983 ◽  
Author(s):  
Edelmiro Regano ◽  
Virtudes Vila ◽  
Justo Aznar ◽  
Victoria Lacueva ◽  
Vicenta Martinez ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Acute Myocardial Infarction ◽  
Molecular Weight ◽  
Steady State ◽  
High Molecular Weight ◽  
Coronary Arteries ◽  
Risk Index ◽  
Weight Fraction ◽  
High Molecular Weight Fraction ◽  
Fibrinopeptide A

SummaryIn 15 patients with acute myocardial infarction who received 1,500,000 U of streptokinase, the gradual appearance of newly synthesized fibrinogen and the fibrinopeptide release during the first 35 h after SK treatment were evaluated. At 5 h the fibrinogen circulating in plasma was observed as the high molecular weight fraction (HMW-Fg). The concentration of HMW-Fg increased continuously, and at 20 h reached values higher than those obtained from normal plasma. HMW-Fg represented about 95% of the total fibrinogen during the first 35 h. The degree of phosphorylation of patient fibrinogen increased from 30% before treatment to 65% during the first 5 h, and then slowly declined to 50% at 35 h.The early rates of fibrinopeptide A (FPA) and phosphorylated fibrinopeptide A (FPAp) release are higher in patient fibrinogen than in isolated normal HMW-Fg and normal fibrinogen after thrombin addition. The early rate of fibrinopeptide B (FPB) release is the same for the three fibrinogen groups. However, the late rate of FPB release is higher in patient fibrinogen than in normal HMW-Fg and normal fibrinogen. Therefore, the newly synthesized fibrinogen clots faster than fibrinogen in the normal steady state.In two of the 15 patients who had occluded coronary arteries after SK treatment the HMW-Fg and FPAp levels increased as compared with the 13 patients who had patent coronary arteries.These results provide some support for the idea that an increased synthesis of fibrinogen in circulation may result in a procoagulant tendency. If this is so, the HMW-Fg and FPAp content may serve as a risk index for thrombosis.

The Effect of Dextran of Various Molecular Weight on the Coagulation in Dogs

1961 ◽  
Vol 06 (01) ◽  
pp. 015-024 ◽  
Author(s):  
Sven Erik Bergentz ◽  
Oddvar Eiken ◽  
Inga Marie Nilsson
Keyword(s):  
Molecular Weight ◽  
Body Weight ◽  
High Molecular Weight ◽  
Bleeding Time ◽  
Factor Vii ◽  
Low Molecular Weight ◽  
Factor V ◽  
Coagulation Mechanism ◽  
Coagulation Defects

Summary1. Infusions of low molecular weight dextran (Mw = 42 000) to dogs in doses of 1—1.5 g per kg body weight did not produce any significant changes in the coagulation mechanism.2. Infusions of high molecular weight dextran (Mw = 1 000 000) to dogs in doses of 1—1.5 g per kg body weight produced severe defects in the coagulation mechanism, namely prolongation of bleeding time and coagulation time, thrombocytopenia, pathological prothrombin consumption, decrease of fibrinogen, prothrombin and factor VII, factor V and AHG.3. Heparin treatment of the dogs was found to prevent the decrease of fibrinogen, prothrombin and factor VII, and factor V otherwise occurring after injection of high molecular weight dextran. Thrombocytopenia was not prevented.4. In in vitro experiments an interaction between fibrinogen and dextran of high and low molecular weight was found to take place in systems comprising pure fibrinogen. No such interaction occurred in the presence of plasma.5. It is concluded that the coagulation defects induced by infusions of high molecular weight dextran are due to intravascular coagulation.

Rapid Isolation of High Molecular Weight Urokinase from Native Human Urine

1982 ◽  
Vol 47 (03) ◽  
pp. 197-202 ◽  
Author(s):  
Kurt Huber ◽  
Johannes Kirchheimer ◽  
Bernd R Binder
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Human Urine ◽  
Gel Filtration ◽  
Chain Structure ◽  
The Other ◽  
Single Chain ◽  
Apparent Homogeneity ◽  
Sequential Adsorption

SummaryUrokinase (UK) could be purified to apparent homogeneity starting from crude urine by sequential adsorption and elution of the enzyme to gelatine-Sepharose and agmatine-Sepharose followed by gel filtration on Sephadex G-150. The purified product exhibited characteristics of the high molecular weight urokinase (HMW-UK) but did contain two distinct entities, one of which exhibited a two chain structure as reported for the HMW-UK while the other one exhibited an apparent single chain structure. The purification described is rapid and simple and results in an enzyme with probably no major alterations. Yields are high enough to obtain purified enzymes for characterization of UK from individual donors.

The Contact Phase of Blood Coagulation in Diabetes Mellitus and in Patients with Vasculopathy

1984 ◽  
Vol 52 (03) ◽  
pp. 221-223 ◽  
Author(s):  
M Christe ◽  
P Gattlen ◽  
J Fritschi ◽  
B Lämmle ◽  
W Berger ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Molecular Weight ◽  
Blood Coagulation ◽  
High Molecular Weight ◽  
Negative Correlation ◽  
Factor Xii ◽  
C1 Inhibitor ◽  
High Molecular Weight Kininogen ◽  
Contact Phase ◽  
Α2 Macroglobulin

SummaryThe contact phase has been studied in diabetics and patients with macroangiopathy. Factor XII and high molecular weight kininogen (HMWK) are normal. C1-inhibitor and also α2-macroglobulin are significantly elevated in diabetics with complications, for α1-macroglobulin especially in patients with nephropathy, 137.5% ± 36.0 (p <0.001). C1-inhibitor is also increased in vasculopathy without diabetes 113.2 ± 22.1 (p <0.01).Prekallikrein (PK) is increased in all patients’ groups (Table 2) as compared to normals. PK is particularly high (134% ± 32) in 5 diabetics without macroangiopathy but with sensomotor neuropathy. This difference is remarkable because of the older age of diabetics and the negative correlation of PK with age in normals.

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