Lipid Polymorphism and Membrane Function

1985 ◽  
pp. 131-204 ◽  
Author(s):  
B. de Kruijff ◽  
P. R. Cullis ◽  
A. J. Verkleij ◽  
M. J. Hope ◽  
C. J. A. Van Echteld ◽  
...  
Keyword(s):  
Membrane Function ◽  
Lipid Polymorphism

The structure of membranes and membrane proteins embedded in amorphous ice

1992 ◽  
Vol 50 (1) ◽  
pp. 432-433
Author(s):  
Uwe Lücken ◽  
Joachim Jäger
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Membrane Proteins ◽  
Phase Transition Temperature ◽  
Lipid Vesicles ◽  
Freezing Stress ◽  
Amorphous Ice ◽  
Different Temperatures ◽  
Band Pass ◽  
Lipid Polymorphism

TEM imaging of frozen-hydrated lipid vesicles has been done by several groups Thermotrophic and lyotrophic polymorphism has been reported. By using image processing, computer simulation and tilt experiments, we tried to learn about the influence of freezing-stress and defocus artifacts on the lipid polymorphism and fine structure of the bilayer profile. We show integrated membrane proteins do modulate the bilayer structure and the morphology of the vesicles.Phase transitions of DMPC vesicles were visualized after freezing under equilibrium conditions at different temperatures in a controlled-environment vitrification system. Below the main phase transition temperature of 24°C (Fig. 1), vesicles show a facetted appearance due to the quasicrystalline areas. A gradual increase in temperature leads to melting processes with different morphology in the bilayer profile. Far above the phase transition temperature the bilayer profile is still present. In the band-pass-filtered images (Fig. 2) no significant change in the width of the bilayer profile is visible.

scholarly journals Longitudinal membrane function in functionally anuric patients treated with APD: Data from EAPOS on the effects of glucose and icodextrin prescription

2005 ◽  
Vol 67 (4) ◽  
pp. 1609-1615 ◽  
Author(s):  
Simon J. Davies ◽  
Edwina A. Brown ◽  
Niels E. Frandsen ◽  
Anabela S. Rodrigues ◽  
Ana Rodriguez-Carmona ◽  
...  
Keyword(s):  
Membrane Function

scholarly journals Serum CA125 a potential marker of volume status for peritoneal dialysis patients?

2021 ◽  
pp. 039139882110168
Author(s):  
Dilushi Wijayaratne ◽  
Vasantha Muthu Muthuppalaniappan ◽  
Andrew Davenport
Keyword(s):  
Heart Failure ◽  
Peritoneal Dialysis ◽  
Left Ventricular ◽  
Volume Status ◽  
Left Ventricular Ejection ◽  
Cancer Antigen 125 ◽  
Membrane Function ◽  
Ventricular Ejection Fraction ◽  
Potential Marker ◽  
Ultrafiltration Failure

Introduction: Serum cancer antigen 125(SeCA125) has been reported to be increased in patients with heart failure and correlate with both extracellular water (ECW) overload and poor prognosis. Ultrafiltration failure and ECW overload are a major cause of peritoneal dialysis (PD) technique failure. We wished to determine whether SeCA125 could also be a marker of volume status in PD patients. Methods: We contemporaneously measured SeCA125, serum N terminal brain natriuretic peptide (NTproBNP) and ECW by bioimpedance in adult PD patients attending for outpatient assessment of peritoneal membrane function. Results: The median SeCA125 was 19 (12–33) U/mL in 489 PD patients, 61.3% male, median age 61.5 (interquartile range 50–75) years. SeCA125 was positively associated with the ratio of ECW/total body water (TBW) ( r = 0.29, p < 0.001), 4-h peritoneal dialysate to serum creatinine ratio ( r = 0.23, p < 0.001), NTproBNP) ( r = 0.18, p < 0.001), and age ( r = 00.17, p = 0.001) and negatively with 24-h PD ultrafiltration volume ( r = −0.28, p < 0.001) serum albumin ( r = −0.22, p < 0.001), and echocardiographic left ventricular ejection fraction ( r = −0.20, p < 0.001), but not with residual renal function or C-reactive protein. Patients with above the median SeCA125, had greater median ECW/TBW 0.403(IQR 0.394–0.410) vs 0.395(0.387–0.404), p < 0.001 and NTproBNP (6870 (IQR 1936–20096) vs 4069 (1345–12291) vs) pg/mL, p = 0.03. Conclusion: Heart failure studies have reported SeCA125 is a marker of ECW overload. Our retrospective analysis suggests that SeCA125 is also associated with ECW volume in PD patients. Further studies are required to determine whether serial measurements of SeCA125 trend with changes in ECW status in PD patients and can be used to aid volume assessments.

Taking Peritoneal Dialysis beyond the Year 2000

1999 ◽  
Vol 19 (3_suppl) ◽  
pp. 35-42 ◽  
Author(s):  
Ram Gokal
Keyword(s):  
Peritoneal Dialysis ◽  
Peritoneal Membrane ◽  
Membrane Function ◽  
Fluid Removal ◽  
The Past ◽  
First Choice ◽  
Year 2000 ◽  
Economic Considerations ◽  
Appropriate Prescription ◽  
Better Than

Over the past 25 years, peritoneal dialysis (PD) has steadily improved so that now its outcomes, in the form of patient survival, are equivalent to, and at times better than, those for hemodialysis. We now have a better understanding of the pathophysiology of peritoneal membrane function and damage and the importance of appropriate prescription to meet agreed-upon targets of solute and fluid removal. In the next millennium, greater emphasis will be put on prescription setting and subsequent monitoring. This will entail an increase in automated PD, especially for lifestyle reasons as well as for patients with a hyperpermeable peritoneal membrane. To improve outcomes, dialysis should be started earlier than is currently the case. It is easy to do this with PD, where an incremental approach is made easier by the introduction of icodextrin for long-dwell PD. In the future, solutions will be tailored to be more biocompatible and to provide improved nutrition and better cardiovascular outcomes. Finally, economic considerations favor PD, which is cheaper than in-centre hemodialysis. Thus, for many, PD has become a first-choice therapy, and with further improvements this trend will continue.

Effect of Small Increments in Plasma Calcium Concentration on the Responsiveness of Forearm Resistance Vessels to Verapamil in Normal Subjects

1984 ◽  
Vol 67 (6) ◽  
pp. 613-618 ◽  
Author(s):  
B. F. Robinson ◽  
R. J. W. Phillips
Keyword(s):  
Calcium Concentration ◽  
Venous Blood ◽  
Normal Subjects ◽  
Plasma Calcium ◽  
Calcium Handling ◽  
Membrane Function ◽  
Resistance Vessels ◽  
Initial Control ◽  
Plasma Calcium Concentration ◽  
Small Increments

1. The effect of a small increase in local plasma calcium concentration on the responsiveness of the forearm resistance vessels to verapamil has been examined in normal subjects, by using a plethysmographic method with infusion of calcium and other agents into the brachial artery. 2. Infusion of calcium at a rate which increased the concentration in forearm venous blood by about 0.5 mmol/l caused basal blood flow to fall by 19% and the dilator response to verapamil to fall by 35% (n = 8; P<0.02). 3. When, after 46 min, the infusion of calcium was discontinued, the dilator response to verapamil increased to reach a level 53% higher than the initial control (n = 8; P<0.02). 4. Infusion of calcium had no effect on the dilator response to sodium nitroprusside. 5. Infusion of noradrenaline at a rate which caused a greater reduction in basal flow than that induced by calcium had no effect on the response to verapamil. 6. It is concluded that the dilator response to verapamil, which is thought to reflect activity of the potential operated system for calcium entry, is selectively depressed by a small elevation of plasma calcium concentration, but subsequently becomes elevated. These findings point to an important role for calcium in the regulation of membrane function in the resistance vessels and support the view that altered calcium handling may contribute to the development of primary hypertension.

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