Identification of a polymer growth process with an equilibrium multi-critical collapse phase transition: the meeting point of swollen, collapsed and crystalline polymers

We have investigated a polymer growth process on the triangular lattice where the configurations produced are self-avoiding trails. We show that the scaling behaviour of this process is similar to the analogous process on the square lattice. However, while the square lattice process maps to the collapse transition of the canonical interacting self-avoiding trail model (ISAT) on that lattice, the process on the triangular lattice model does not map to the canonical equilibrium model. On the other hand, we show that the collapse transition of the canonical ISAT model on the triangular lattice behaves in a way reminiscent of the $\theta$-point of the interacting self-avoiding walk model (ISAW), which is the standard model of polymer collapse. This implies an unusual lattice dependency of the ISAT collapse transition in two dimensions. By studying an extended ISAT model, we demonstrate that the growth process maps to a multi-critical point in a larger parameter space. In this extended parameter space the collapse phase transition may be either $\theta$-point-like (second-order) or first-order, and these two are separated by a multi-critical point. It is this multi-critical point to which the growth process maps. Furthermore, we provide evidence that in addition to the high-temperature gas-like swollen polymer phase (coil) and the low-temperature liquid drop-like collapse phase (globule) there is also a maximally dense crystal-like phase (crystal) at low temperatures dependent on the parameter values. The multi-critical point is the meeting point of these three phases. Our hypothesised phase diagram resolves the mystery of the seemingly differing behaviours of the ISAW and ISAT models in two dimensions as well as the behaviour of the trail growth process

Oxysterols Increase Inflammation, Lipid Marker Levels and Reflect Accelerated Endothelial Dysfunction in Experimental Animals

Objective. Oxidized cholesterol derivatives are thought to exert atherogenic effect thus adversely affecting vascular endothelium. The aim of the study was to assess the effect of 5α,6α-epoxycholesterol on experimentally induced hypercholesterolemia in rabbits, and the levels of homocysteine (HCY), asymmetric dimethylarginine (ADMA), paraoxonase-1 (PON-1), and inflammatory parameters (IL-6, TNF-α, CRP). Material and methods. The rabbits were divided into 3 groups, 8 animals each, and fed with basic fodder (C), basic fodder plus cholesterol (Ch) or basic fodder plus 5α,6α-epoxycholesterol, and unoxidized cholesterol (ECh). Serum concentrations of studied parameters were determined at 45-day intervals. The study was continued for six months. Results. We demonstrated that adding 5α,6α-epoxycholesterol to basic fodder significantly affected lipid status of the experimental animals, increasing total cholesterol and LDL cholesterol levels, as well as HCY and ADMA levels, whilst leaving the PON-1 activity unaffected. Additionally, the ECh group presented with significantly higher concentrations of inflammatory biomarkers (IL-6, TNF-α, and CRP). In the Ch group, lower yet significant (as compared to the C group) changes of levels of studied parameters were observed. Conclusion. Exposure of animals with experimentally induced hypercholesterolemia to 5α,6α-epoxycholesterol increases dyslipidaemia, endothelial dysfunction, and inflammatory response

5α,6α-Epoxyphytosterols and 5α,6α-Epoxycholesterol Increase Nitrosative Stress and Inflammatory Cytokine Production in Rats on Low-Cholesterol Diet

Objective. Oxidized cholesterol derivatives are compounds with proven atherogenic and mutagenic effects. However, little is known about the effect of oxidized plant sterol derivatives (oxyphytosterols), whose structure is similar to the one of oxycholesterols. Our previous studies indicate that they have a similar profile of action, e.g., both exacerbate disorder of lipid metabolism and oxidative stress in experimental animals. The aim of the present study was to assess the effect of epoxycholesterol and epoxyphytosterols (mainly sitosterol) on the severity of nitrosative stress and the concentration of selected proinflammatory cytokines in blood and liver tissue of rats on a low-cholesterol diet. Material and Methods. Forty-five male Wistar rats were fed with feed containing 5α,6α-epoxyphytosterols (ES group, n: 15), 5α,6α-epoxycholesterol (ECh group, n: 15), and oxysterol-free feed (C group, n: 15) for 90 days (daily dose of oxysterols: 10 mg/kg). At the end of the experiment, nitrotyrosine, TNF-α, IL-1β, IL-6, and lipid metabolism parameters were determined in blood serum. Furthermore, nitrotyrosine, TNF-α, cholesterol, and triglyceride content were determined in liver homogenates. Results. Serum nitrotyrosine, IL-1β, and TNF-α concentrations as well as TNF-α content in the liver were significantly higher in both groups exposed to oxysterols (ECh and ES groups) as compared to the C group. The serum IL-6 level and nitrotyrosine content in the liver were significantly higher in the ECh group, as compared to the C and ES groups. There was evidence to support the dyslipidemic effect of studied compounds. Conclusions. The results indicate that oxidized plant sterols have a similar toxicity profile to that of oxycholesterols, including nitrosative stress induction, proinflammatory effect, and impaired lipid metabolism

5α,6α-Epoxyphytosterols and 5α,6α-Epoxycholesterol Increase Oxidative Stress in Rats on Low-Cholesterol Diet

Objective. Cholesterol oxidation products have an established proatherogenic and cytotoxic effect. An increased exposure to these substances may be associated with the development of atherosclerosis and cancers. Relatively little, though, is known about the effect of phytosterol oxidation products, although phytosterols are present in commonly available and industrial food products. Thus, the aim of the research was to assess the effect of 5α,6α-epoxyphytosterols, which are important phytosterol oxidation products, on redox state in rats. Material and Methods. The animals were divided into 3 groups and exposed to nutritional sterols by receiving feed containing 5α,6α-epoxyphytosterols (ES group) and 5α,6α-epoxycholesterol (Ech group) or sterol-free feed (C group). The levels of malondialdehyde (MDA), conjugated dienes (CD), and ferric reducing antioxidant potential (FRAP) were assayed in the plasma; anti-7-ketocholesterol antibodies and activity of paraoxonase-1 (PON1) were determined in serum, whereas the activity of catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx), S-glutathione transferase (GST), and superoxide dismutase (SOD) were assayed in RBCs. Results. During the experiment, the levels of lipid peroxidation products increased, such as CD and anti-7-ketocholesterol antibodies. At the same time, the plasma levels of FRAP and serum activity of PON1 decreased alongside the reduced activity of GPx, GR, and SOD in RBCs. There was no effect of the studied compounds on the plasma MDA levels or on the activity of CAT and GST in RBCs. Conclusions. Both 5α,6α- epoxyphytosterols and 5α,6α-epoxycholesterols similarly dysregulate the redox state in experimental animal model and may significantly impact atherogenesis

Winding angle distributions for two-dimensional collapsing polymers

9 pages, 5 figures, (this version: email address corrected

Analysis of postural disorders using a stabilometric platform in patients with rheumatic diseases

Wstęp W przebiegu reumatoidalnego zapalenia stawów (RZS) ważnym problemem wpływającym na stabilność oraz symetrię obciążenia kończyn dolnych jest globalne upośledzenie motoryki stopy spowodowane jej płasko-koślawą deformacją, a także występowanie licznych zmian w obrębie stawów stóp. W zesztywniającym zapaleniu stawów kręgosłupa (ZZSK) dochodzi ostatecznie do trwałego ograniczenia ruchomości kręgosłupa co prowadzi do zaburzeń prawidłowego obciążania kończyn dolnych i równowagi ciała. W twardzinie układowej (TU) ból i przykurcze stawowe negatywnie oddziałują na prawidłową postawę i stabilność ciała oraz prawidłowe obciążenie kończyn dolnych. Metodyka Badanie balansu ciała oraz stabilności i symetrii obciążenia kończyn dolnych wykonano na komputerowej dwupłytowej platformie stabilometrycznej. Badanie składało się z dwóch prób – pierwszej z otwartymi i drugiej z zamkniętymi oczami. Wyniki Ogółem przebadano 50 chorych z ZZSK, 68 chorych z RZS oraz 53 chorych z TU. Nie wykazano istotnych statystycznie różnic między badanymi grupami z uwzględnieniem badania z oczami otwartymi jak i zamkniętymi. W każdej grupie badanej wykazano istotnie statystycznie wyższe wartości całkowitej drogi, którą przebył środek nacisku stóp chorego w ciągu badania, ocenianego przy zamkniętych oczach względem ocenianego przy otwartych oczach. Dyskusja Analizowane w pracy grupy stanowią trzy odrębne funkcjonalnie choroby tkanki łącznej, charakteryzujące się zajęciem innych składowych elementu ruchu. Twardzina układowa jawi się jako choroba o zupełnie odmiennym wzorcu ruchu charakteryzującego się zmniejszeniem wychylenia środka nacisku stóp zarówno w badaniu z zamkniętymi jak i otwartymi oczami. Wnioski W chorobach reumatycznych powszechnie występują zaburzenia postawy i prawidłowego utrzymania równowagi, a wzorzec zaburzeń ruchowych jest zależny od danej choroby.Background: In the course of rheumatoid arthritis (RA), an important problem that affects the stability and symmetry of lower limb loading is the global motor impairment of the foot due to its planovalgus deformity, as well as the occurrence of numerous lesions in the foot joints. In ankylosing spondylitis (AS), there is eventually a permanent limitation of spinal mobility, which results in impaired lower limb loading and body balance. In systemic sclerosis (SSc), pain and joint contractures negatively affect the proper posture and stability of the body and the normal lower limb loading. Material and methods:Tests of body balance, stability and symmetry of lower limb loading were performed on a computerised two-plate stabilometric platform. The testing consisted of two trials — the first performed with eyes open (open-eye test) and the second performed with eyes closed (closed-eye test). Results: There were a total of 50 AS patients, 68 RA patients and 53 SSc patients examined. There were no statistically significant differences between the study groups including the open-eye test and the closed-eye test. Each study group revealed statistically significant higher values for the total distance travelled by the patient's centre of pressure of the feet over the course of testing as assessed using the closed-eye test compared to the open-eye test. Discussion: The groups analysed in this paper represent three functionally distinct connective tissue diseases that are marked by involvement of different constituents of the motor system component. Systemic sclerosis (SSc) presents itself as a disease with a completely different movement pattern that is marked by a reduction in the amplitudes of the centre of pressure (CoP) in both the closed-eye test and the open-eye test. Conclusions: Postural and balance disorders are common in rheumatic diseases, and the pattern of movement disorders is disease-specific.

The Effects of Duodenojejunal Omega Switch in Combination with High-Fat Diet and Control Diet on Incretins, Body Weight, and Glucose Tolerance in Sprague-Dawley Rats

Background: Despite excellent results of bariatric surgery in the treatment of type 2 diabetes and weight loss in human subjects, some patients do not obtain desired results. One of the reasons for this is that not all patients follow caloric intake recommendations. Aim: The aim of this study was to investigate the effect of duodenojejunal omega switch (DJOS) surgery on body weight, glucose tolerance, and incretins in rats. Methods: DJOS and SHAM surgery were performed on rats maintained for 8 weeks on high-fat diet (HF) and control diet (CD), respectively. After surgery, four groups were kept on the same diet as before the surgery, and four groups had a changed diet (CD vs. HF and HF vs. CD) for the next 8 weeks. Glucose tolerance, insulin tolerance, glucose-stimulated insulin, glucagon-like peptide-1 (GLP-1) and gastric inhibitory polypeptide/glucose-dependent insulinotropic polypeptide (GIP) secretion, food intake, and body weight were measured. Results: A change of diet after surgery resulted in reduced glucose tolerance. Plasma insulin levels were lowered between DJOS and SHAM surgeries for the HF/HF and CD/HF groups. DJOS surgery did not reduce body weight in the studied groups, irrespective of diet. In the HF/HF group, ΔGLP-1 was lower for DJOS surgery in comparison with other groups. Differences of weight changes were observed for groups HF/HF and HF/CD. After DJOS surgery, ΔGIP was lower in the CD/HF group compared with HF/HF. Conclusions: Our results show that applications of different types of diets, before and after surgery, is a sensitive method for studies of mechanism of glucose intolerance after DJOS surgery