Phase transitions in biological membranes

Native membranes of biological cells display melting transitions of their lipids at a temperature of 10-20 degrees below body temperature. Such transitions can be observed in various bacterial cells, in nerves, in cancer cells, but also in lung surfactant. It seems as if the presence of transitions slightly below physiological temperature is a generic property of most cells. They are important because they influence many physical properties of the membranes. At the transition temperature, membranes display a larger permeability that is accompanied by ion-channel-like phenomena even in the complete absence of proteins. Membranes are softer, which implies that phenomena such as endocytosis and exocytosis are facilitated. Mechanical signal propagation phenomena related to nerve pulses are strongly enhanced. The position of transitions can be affected by changes in temperature, pressure, pH and salt concentration or by the presence of anesthetics. Thus, even at physiological temperature, these transitions are of relevance. There position and thereby the physical properties of the membrane can be controlled by changes in the intensive thermodynamic variables. Here, we review some of the experimental findings and the thermodynamics that describes the control of the membrane function.Comment: 23 pages, 15 figure

The influence of anesthetics, neurotransmitters and antibiotics on the relaxation processes in lipid membranes

In the proximity of melting transitions of artificial and biological membranes fluctuations in enthalpy, area, volume and concentration are enhanced. This results in domain formation, changes of the elastic constants, changes in permeability and slowing down of relaxation processes. In this study we used pressure perturbation calorimetry to investigate the relaxation time scale after a jump into the melting transition regime of artificial lipid membranes. This time corresponds to the characteristic rate of domain growth. The studies were performed on single-component large unilamellar and multilamellar vesicle systems with and without the addition of small molecules such as general anesthetics, neurotransmitters and antibiotics. These drugs interact with membranes and affect melting points and profiles. In all systems we found that heat capacity and relaxation times are related to each other in a simple manner. The maximum relaxation time depends on the cooperativity of the heat capacity profile and decreases with a broadening of the transition. For this reason the influence of a drug on the time scale of domain formation processes can be understood on the basis of their influence on the heat capacity profile. This allows estimations of the time scale of domain formation processes in biological membranes.Comment: 12 pages, 6 figure

The importance of open emergency surgery in the treatment of acute mesenteric ischemia

OBJECTIVE: Acute mesenteric ischemia (AMI) is a complex disease with a high mortality rate. A patient’s chance of survival depends on early diagnosis and rapid revascularization to prevent progression of intestinal gangrene. We reviewed our experience with open surgery treatment in 54 cases of AMI. METHODS: A monocentric retrospective study was conducted between 01/01/2001 and 04/30/2014; 54 AMI patients with a mean age of 56.6 years underwent surgery (26 women and 28 men). Retrospectively, the risk factors, management until diagnosis, vascular therapy and follow-up were evaluated. RESULTS: The symptom upon admission was an acute abdominal pain event. The delay time from admission to surgery was, on average, 13.9 h (n = 34). The therapeutic procedures were open surgical operations. The complication rate was (53.7 %) (n = 29). The 30-day mortality was 29.6 % (n = 16). The late mortality rate was 24.1 % (n = 13), and the cumulative survival risk was 44.6 %. Survival was, on average, 60.54 months; however, in the over 70-year-old patient subgroup, the survival rate was 9.5 months (p = 0.035). The mortality rate was 27 % (n = 22) in the <12 h delay group, 20 % (n = 5) in the 12–24 h delay group, and 50 % (n = 7) in the > 24 h delay group. CONCLUSIONS: The form of therapy depends on the intraoperative findings and the type of occlusion. Although the mortality rate has decreased in the last decade, in patients over 70 years of age, a significantly worse prognosis was seen

Повышение конкурентноспособности продукции на основе эффективной системы управления качеством в организации

В процессе исследования проводились анализ и оценка конкурентоспособности предприятия и продукции и разработка мероприятий по повышению её конкурентоспособности.In the course of the research, the analysis and assessment of the competitiveness of the enterprise and products and the development of measures to increase its competitiveness were carried out

Pediatric Liver and Kidney Transplant Recipients Demonstrate Greater Serological Response to SARS-CoV-2 Vaccination Than Adults

Background. Adult solid organ transplant recipients (SOTRs) have decreased responsiveness to severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) vaccination and higher incidence of infection, but there are few data on the serological response in pediatric SOTR. The aim of this study was to determine serological response to SARS-CoV-2 vaccination in pediatric liver (LT) and kidney transplant (KT) recipients and compare it with adult SOTR. Methods. A European, prospective, multicenter study was performed. Samples were taken at 7 and 32 wk following COVID-19 vaccination and serological endpoints were measured by ELISA. Results. A total of 42 pediatric (16 post-LT and 26 post-KT) and 117 adult (all post-LT) were included. All pediatric participants and 94% adult participants received mRNA vaccines. Paediatric SOTR patients had significantly higher anti-Spike IgG levels than adult participants at week 7 (114 220.7 [59 285.92-220 058.55] versus 8756.7 [5643.69-13 586.71], P < 0.0001) and week 32 (46 113.2 [10 992.91-193 436.14] versus 8207.0 [3561.20-18 913.43], P = 0.0032). No significant difference in week 7 anti-Spike IgG response was found between pediatric LT and KT (129 434.4 [51 888.64-322 869.69] versus 105 304.5 [39 910.20-277 849.50], P = 0.9854). No differences were seen between children and adults in the rate of decline of anti-Spike IgG between weeks 7 and 32 (P = 0.8000). Male sex and hemolytic-uremic syndrome or postischemic kidney disease were associated with lower anti-Spike IgG levels at week 7 in pediatric SOTR. Conclusions. Paediatric SOTR demonstrate greater SARS-CoV-2 vaccine responses than comparable adult SOTR patients. These data support efficacy and safety of SARS-CoV-2 vaccination in child SOTR and may alleviate vaccine hesitancy in this patient group