Effect of dialysate volume on peritoneal dialysis kinetics

Effect of dialysate volume on peritoneal dialysis kinetics. The effect of peritoneal dialysate volume on the rates of transperitoneal urea and creatinine equilibration was determined over a 120-min sampling period. Equilibration half-time (t1/2) was prolonged when volume was increased from 1 to 2 to 3 liters. Some data suggest this delay was not attributable to a decrease in peritoneal permeability or blood flow. If that is true, our data indicate that slower urea equilibration with larger dialysate volumes is due to changes in volume/surface area relationships. Because solutes equilibrated more rapidly into 1 liter than into 2 liters, peritoneal clearances using an exchange schedule of 1 liter every 30 min were comparable to those obtained with 2 liters exchanged every 60 min. Therefore, patients susceptible to cardiopulmonary complications may be dialyzed without loss of efficiency by infusing 1 liter every 30 min instead of the usual 2 liters every 60 min.Effet du volume de dialyse sur la cinétique de la dialyse peritonéale. L'effet du volume du dialysat péritonéal sur les vitesses d'équilibration transpéritonéale de l'urée et de la créatinine a été étudié pendant une période de prélèvements de 120 min. Le temps de demi-équilibration (t1/2) est allongé quand le volume est augmenté de 1 à 2 et de 2 à 3 litres. Certains faits suggèrent que ce retard n'est pas attribuable à une diminution de la perméabilité ou du débit sanguin péritonéaux. Dans ce cas nos résultats indiqueraient que l'équilibration plus lente de l'urée, quand le volume de dialysat est plus grand, serait liée aux modifications du rapport volume/surface. Du fait que les substances dissoutes s'équilibrent plus rapidement dans 1 l que dans 2 l les clearances péritonéales sont comparables dans un programme d'échange d'un litre toutes les 30 minutes à celles obtennes dans un programme d'éxchange de 2 litres toutes les 60 minutes. Par conséquent il est possible de dialyser les malades exposés à des complications cardiopulmonaires sans perte d'efficacité, en injectant 1 litre toutes les 30 minutes au lieu des 2 litres habituels toutes les 60 minutes

Evolution of Stenophagy in Spiders (Araneae): Evidence Based on the Comparative Analysis of Spider Diets

Stenophagy (narrow diet breadth) represents an extreme of trophic specialization in carnivores, but little is known about the forces driving its evolution. We used spiders, the most diversified group of terrestrial predators, to investigate whether stenophagy (1) promoted diversification; (2) was phylogenetically conserved and evolutionarily derived state; and (3) was determined either by geographical distribution and foraging guild. We used published data on the prey of almost 600 species. Six categories of stenophagy were found: myrmecophagy, araneophagy, lepidopterophagy, termitophagy, dipterophagy, and crustaceophagy. We found that the species diversity of euryphagous genera and families was similar to stenophagous genera and families. At the family level, stenophagy evolved repeatedly and independently. Within families, the basal condition was oligophagy or euryphagy. Most types of stenophagy were clearly derived: myrmecophagy in Zodariidae; lepidopterophagy in Araneidae; dipterophagy in Theridiidae. In contrast, araneophagy was confined to basal and intermediate lineages, suggesting its ancestral condition. The diet breadth of species from the tropics and subtropics was less diverse than species from the temperate zone. Diet breadth was lower in cursorial spiders compared to web-building species. Thus, the evolution of stenophagy in spiders appears to be complex and governed by phylogeny as well as by ecological determinants

Evolution of Stenophagy in Spiders (Araneae): Evidence Based on the Comparative Analysis of Spider Diets

Stenophagy (narrow diet breadth) represents an extreme of trophic specialization in carnivores, but little is known about the forces driving its evolution. We used spiders, the most diversified group of terrestrial predators, to investigate whether stenophagy (1) promoted diversification; (2) was phylogenetically conserved and evolutionarily derived state; and (3) was determined either by geographical distribution and foraging guild. We used published data on the prey of almost 600 species. Six categories of stenophagy were found: myrmecophagy, araneophagy, lepidopterophagy, termitophagy, dipterophagy, and crustaceophagy. We found that the species diversity of euryphagous genera and families was similar to stenophagous genera and families. At the family level, stenophagy evolved repeatedly and independently. Within families, the basal condition was oligophagy or euryphagy. Most types of stenophagy were clearly derived: myrmecophagy in Zodariidae; lepidopterophagy in Araneidae; dipterophagy in Theridiidae. In contrast, araneophagy was confined to basal and intermediate lineages, suggesting its ancestral condition. The diet breadth of species from the tropics and subtropics was less diverse than species from the temperate zone. Diet breadth was lower in cursorial spiders compared to web-building species. Thus, the evolution of stenophagy in spiders appears to be complex and governed by phylogeny as well as by ecological determinants