Effects of an arteriovenous fistula stenosis prevention program in patients receiving hemodialysis.

BACKGROUND: To increase the efficiency of hemodialysis, an appropriate vascular pathway must be created, and its function must be maintained. This study aimed to identify the effects of an arteriovenous fistula (AVF) stenosis prevention program on upper muscular strength, blood flow, physiological indexes, and self-efficacy among patients receiving hemodialysis. METHODS: The participants were patients receiving hemodialysis at Keimyung University Dongsan Medical Center in Daegu, Republic of Korea. They were divided into experimental and control groups based on the day of the week they received hemodialysis at the outpatient department and included 25 participants each. The study was conducted for 8 weeks. RESULTS: The AVF stenosis prevention program was effective in improving upper extremity muscle strength (F=15.23, p<0.001) and blood flow rate (F=36.00, p<0.001). As a result of the program, the phosphorus index level, which is a physiological indicator in hemodialysis patients, decreased (F=8.64, p<0.001). Encouragement and support through text messages and practice lists also resulted in an increase in self-efficacy (F=18.62, p<0.001). CONCLUSION: The AVF stenosis prevention program in this study resulted in an increase in upper extremity muscle strength through grip strength exercises and was effective in preventing AVF stenosis by increasing the blood flow rate.

Tipping points of gastric pH regulation and energetics in the sea urchin larva exposed to CO2 -induced seawater acidification.

Sea urchin larvae reduce developmental rates accompanied by changes in their energy budget when exposed to acidified conditions. The necessity to maintain highly alkaline conditions in their digestive systems led to the hypothesis that gastric pH homeostasis is a key trait affecting larval energy budgets leading to distinct tipping points for growth and survival. To test this hypothesis, sea urchin (Strongylocentrotus purpuratus) larvae were reared for 10 days in different pH conditions ranging from pH 7.0 to pH 8.2. Survival, development and growth rates were determined demonstrating severe impacts < pH 7.2. To test the effects of pH on midgut alkalization we measured midgut pH and monitored the expression of acid-base transporters. While larvae were able to maintain their midgut pH at 8.9-9.1 up to an acidification level of pH 7.2, midgut pH was decreased in the lower pH treatments. The maintenance of midgut pH under low pH conditions was accompanied by dynamic changes in the expression level of midgut acid-base transporters. Metabolic rates of the larvae increased with decreasing pH and reached a threshold between pH 7.0 and pH 7.3 where metabolic rates decreased again. Methylation analyses on promoter CpG islands were performed for midgut acid-base transporter genes to test for possible epigenetic modifications after 10-day exposure to different pH conditions. This analysis demonstrated no correlation between methylation level and pH treatments suggesting low potential for epigenetic modification of acid-base transporters upon short-term exposure. Since a clear tipping point was identified at pH 7.2, which is much lower than near-future ocean acidification (OA) scenarios, this study suggests that the early development of the purple sea urchin larva has a comparatively high tolerance to seawater acidification with substantial acclimation capacity and plasticity in a key physiological trait under near-future OA conditions.

Variability in larval gut pH regulation defines sensitivity to ocean acidification in six species of the Ambulacraria superphylum.

The unusual rate and extent of environmental changes due to human activities may exceed the capacity of marine organisms to deal with this phenomenon. The identification of physiological systems that set the tolerance limits and their potential for phenotypic buffering in the most vulnerable ontogenetic stages become increasingly important to make large-scale projections. Here, we demonstrate that the differential sensitivity of non-calcifying Ambulacraria (echinoderms and hemichordates) larvae towards simulated ocean acidification is dictated by the physiology of their digestive systems. Gastric pH regulation upon experimental ocean acidification was compared in six species of the superphylum Ambulacraria. We observed a strong correlation between sensitivity to ocean acidification and the ability to regulate gut pH. Surprisingly, species with tightly regulated gastric pH were more sensitive to ocean acidification. This study provides evidence that strict maintenance of highly alkaline conditions in the larval gut of Ambulacraria early life stages may dictate their sensitivity to decreases in seawater pH. These findings highlight the importance of identifying and understanding pH regulatory systems in marine larval stages that may contribute to substantial energetic challenges under near-future ocean acidification scenarios.