Improving near-peer teaching quality in anatomy by educating teaching assistants: An example from Sweden.

Peer-assisted learning has gained momentum in a variety of disciplines, including medical education. In Gothenburg, Sweden, medical students who have finished their compulsory anatomy courses have the option of working as teaching assistants (TAs). Teaching assistants provide small group teaching sessions as a complement to lectures given by faculty. Previously, TAs were left to handle the role as junior teachers by themselves, but since 2011, a continuation course in anatomy has been developed with the aim of providing the TAs better anatomy knowledge and guidance for teaching. The course was designed to comprise 7.5 ECTS credits (equivalent to 5 weeks of full-time studies), and today all TAs are required to take this course before undertaking their own teaching responsibilities. This study aims to compare course evaluations of TA teaching before and after the introduction of the anatomy continuation course, in order to understand how students perceived teaching performed by self-learned versus trained TAs. The results of this study demonstrate that there was a trend towards better teaching performed by trained TAs. The variability in rankings decreased significantly after the introduction of the continuation course. This was mainly due to an improvement among the TAs with the lowest levels of performance. In addition to comparing student rankings, TAs were interviewed regarding their experiences and perceptions within the continuation course. The course was generally positively regarded. The TAs described a sense of cohesion and appreciation since the institute invested in a course dedicated specifically for them. Anat Sci Educ 11: 403-409. © 2018 American Association of Anatomists.

TRPA1 Mechanoreceptors Mediate the IL-6 Response to a Single PD Dwell in the Rat.

BACKGROUND: The development of modern, biocompatible peritoneal dialysis (PD) fluids has not entirely eliminated the local pro-inflammatory effects of PD fluid administration. The present study was performed in order to establish the importance of known signaling pathways connected to mechano-, osmo- and chemo-sensors of the transient receptor potential (TRP) family for the acute inflammatory response to PD. METHODS: Rats were exposed to a single 4-hour dwell of lactate-buffered, 2.5% glucose, filter-sterilized PD fluid through an implanted PD catheter. In some groups, the PD dwell was preceded by intravenous administration of blockers of TRPV1 (BCTC), TRPA1 (HC030031), or neurokinin 1 (NK1) (Spantide II) receptors. Cytokine messenger ribonucleic acid (mRNA) expressions were quantified in tissue biopsies (real-time polymerase chain reaction [qPCR]), and cytokine concentrations were quantified in dialysate samples by enzyme-linked immunosorbent assay (ELISA). Tissue expressions of TRPV1, TRPA1, and NK1 were evaluated immuno-histochemically. RESULTS: The PD dwell induced peritoneal synthesis of Il1b, Tnf, and Il6 and a secretion of interleukin-6 (IL-6) into the dialysate. The catheter implantation already induced the transcription of Il1b and Tnf but did not significantly affect Il6 transcription. The Il6 response to the PD dwell could be virtually eliminated by blocking TRPA1 but was not affected by TRPV1 blockade. Blocking the substance P receptor, NK1, produced an insignificant trend towards Il6 inhibition. TRPA1 and NK1 showed a stronger immuno-reactivity than TRPV1 on cells of the peritoneal tissue. CONCLUSION: The results show that IL-6 synthesis and secretion were connected to acute PD fluid exposure, and this response was triggered by TRPA1 receptors, possibly located to non-neuronal cells.

Erythrocytes as Volume Markers in Experimental PD Show that Albumin Transport in the Extracellular Space Depends on PD Fluid Osmolarity.

UNLABELLED: ♦ BACKGROUND: Macromolecules, when used as intraperitoneal volume markers, have the disadvantage of leaking into the surrounding tissue. Therefore, (51)Cr-labeled erythrocytes were evaluated as markers of intraperitoneal volume and used in combination with (125)I-labeled bovine serum albumin to study albumin transport into peritoneal tissues in a rat model of peritoneal dialysis (PD). ♦ METHODS: Single dwells of 20 mL of lactate-buffered filter-sterilized PD fluid at glucose concentrations of 0.5%, 2.5%, and 3.9% were performed for 1 or 4 hours. Tissue biopsies from abdominal muscle, diaphragm, liver, and intestine, and blood and dialysate samples, were analyzed for radioactivity. ♦ RESULTS: The dialysate distribution volume of labeled erythrocytes, measured after correction for lymphatic clearance to blood, was strongly correlated with, but constantly 3.3 mL larger than, drained volumes. Erythrocyte activity of rinsed peritoneal tissue biopsies corresponded to only 1 mL of dialysate, supporting our utilization of erythrocytes as markers of intraperitoneal volume. The difference between the distribution volumes of albumin and erythrocytes was analyzed to represent the albumin loss into the peritoneal tissues, which increased rapidly during the first few minutes of the dwell and then leveled out at 2.5 mL. It resumed when osmotic ultrafiltration turned into reabsorption and, at the end of the dwell, it was significantly lower for the highest osmolarity PD fluid (3.9% glucose). Biopsy data showed the lowest albumin accumulation and edema formation in abdominal muscle for the 3.9% fluid. ♦ CONCLUSION: Labeled erythrocytes are acceptable markers of intraperitoneal volume and, combined with labeled albumin, provided novel kinetic data on albumin transport in peritoneal tissues.

Neuropeptide release augments serum albumin loss and reduces ultrafiltration in peritoneal dialysis.

BACKGROUND: The triggers of the acute local inflammatory response to peritoneal dialysis (PD) fluid exposure remain unknown. In the present study, we investigated the effects of neurogenic inflammation and mast cell degranulation on water and solute transport in experimental PD. METHODS: Single 2-hour dwells in rats with PD catheters were studied. Histamine and the neuropeptides substance P and calcitonin gene-related peptide (CGRP) were measured in PD fluid samples by ELISA. Radiolabeled albumin ((125)I and (131)I respectively) was used as an intraperitoneal (IP) and intravascular tracer. Glucose and urea concentrations were measured in plasma and PD fluid. The effects of varying the volume and osmolarity of a lactate-buffered PD fluid were compared and related to the effects of pharmacologic intervention. RESULTS: Application of 20 mL 3.9% glucose PD fluid induced an IP histamine release during the first 30 minutes, blockable by the mast cell stabilizer doxantrazole and the substance P neurokinin-1 receptor (NK1R)-blocker spantide. Histamine release was also inhibited at a reduced PD volume (14 mL), but was not affected by normalizing the PD fluid osmolarity. Blockade of NK1R also reduced plasma albumin leakage to the peritoneal cavity. Inhibition of CGRP receptors by CGRP8-37 improved osmotic (transcapillary) and net ultrafiltration and reduced the dialysate urea concentration. Neuropeptide release was not clearly related to activation of the TrpV1 receptor, the classic trigger of neurogenic inflammation. CONCLUSIONS: Neuropeptide release exaggerated albumin loss and reduced ultrafiltration in this rat PD model. Intervention aimed at the neuropeptide action substantially improved PD efficiency.

Catheter patency and peritoneal morphology and function in a rat model of citrate-buffered peritoneal dialysis.

BACKGROUND: Single-dwell studies in rats and humans have shown that supplementing citrate for lactate in peritoneal dialysis (PD) fluids improves ultrafiltration (UF). ♢ METHODS: The long-term effects of citrate-substituted PD fluids on PD catheter patency, UF, and peritoneal morphology were evaluated in a rat model over 5 weeks of daily PD fluid exposure. A standard 2.5% glucose 40 mmol/L lactate PD fluid and a corresponding 10/30 mmol/L citrate/lactate PD fluid were compared. In a control group, rats with catheters received no PD fluid. ♢ RESULTS: The average patency time (% of 36 days) of silicone rubber PD catheters was significantly longer in the citrate PD group (98.8% ± 1.2%) and the control group (100% ± 0%) compared to the lactate PD group (54.7% ± 9.5%). In a separate experiment, heparin-coated polyurethane catheters were used to study peritoneal morphology and fluid transport. The citrate group had a higher net UF than the lactate group at the beginning and at the end of the 5 weeks. During the experiment, both fluid-treated groups suffered from UF loss; the control group showed the highest net UF at the end of the 5 weeks. Peritoneal vascular density and submesothelial thickness, indicators of angiogenesis and fibrosis, were not significantly different among the groups. Fibrosis was significantly negatively correlated to osmotic UF. ♢ CONCLUSION: A positive acute effect of citrate on UF was confirmed and conserved over time. Citrate PD strongly improved PD catheter patency time compared with lactate. Both citrate PD and lactate PD induced negative long-term effects on UF compared with control animals.

Substituting citrate for lactate in peritoneal dialysis fluid improves ultrafiltration in rats.

BACKGROUND: Exposure to peritoneal dialysis (PD) fluid induces an inflammatory response in the peritoneal cavity. Blockers of complement and coagulation have improved ultrafiltration in animal models of PD. Citrate is a clinically established anticoagulant that also blocks complement activation. OBJECTIVE: The aim of the present study was to evaluate the effects on ultrafiltration of a gradual substitution of citrate for lactate in an experimental model of PD. METHODS: Fractions (0, 5, 10, and 15 mmol/L) of the 40 mmol/L lactate buffer of filter-sterilized 2.5% glucose PD fluid were replaced by citrate. The modified fluids were compared in a rat model of single PD fluid exposure through an indwelling catheter. The initial kinetics of citrate and ionized calcium were evaluated in separate, single, short time dwell experiments. RESULTS: Replacing 10 and 15 mmol/L of the lactate buffer by sodium citrate significantly increased osmotic ultrafiltration (by 24.7%+/-7.7% at 10 mmol/L), net ultrafiltration, and glucose retention at 4 hours of dwell time in the rat model. Osmotic ultrafiltration was significantly correlated to citrate concentration and glucose concentration. Citrate was rapidly eliminated from the peritoneal cavity, concentrations falling to less than half in 1 hour and concentrations of calcium ions concomitantly normalized. CONCLUSIONS: Substituting citrate for lactate induced a dose-dependent increase in ultrafiltration. Mechanisms probably involve the relation between diffusion and ultrafiltration, leading to increased glucose retention. The increase in ultrafiltration was quantitatively important at a citrate concentration (10 mmol/L) that is compatible with clinical applications of citrate.

Citrate supplementation of PD fluid: effects on net ultrafiltration and clearance of small solutes in single dwells.

BACKGROUND: Inflammatory reactions affect the general performance as well as the technique survival of peritoneal dialysis (PD). Anti-inflammatory additives like heparin and sodium citrate have shown favourable results in these respects. The present study is the first to evaluate citrate-supplemented PD fluids (PDFs) in humans. METHODS: Crossover design was used to evaluate sodium citrate and heparin-supplemented Gambrosol Trio (2.5% glucose) in 28 stable outpatients from the PD unit. Comparisons were made between single dwells of each fluid. Citrate supplementation at 5 mM/L was compared with standard PDF, and citrate supplementation at 10 mM/L was compared with low-molecular-weight heparin (4500 units of tinzaparin) supplementation and standard PDF. The initial osmolarity of the fluids was equalized by adding sodium chloride. RESULTS: Citrate supplementation at 5 mM/L significantly increased net ultrafiltration, measured as drained volume gain, by 126 mL. Creatinine and phosphate clearance, but not glucose clearance, was significantly improved by supplementation with citrate or heparin. Heparin supplementation created an insignificant trend towards an increased ultrafiltration (P = 0.08). No negative side effects were reported for any of the treatments; however, citrate supplementation led to a small calcium loss by the drained PD fluid (0.4 mmol) and a transient fall in the plasma concentration (0.04 mM/L) of free calcium ions at 5 mM/L citrate. Effects on plasma bicarbonate concentration were insignificant. CONCLUSIONS: Citrate supplementation of PD fluid improved ultrafiltration and clearance of small solutes with only minor effects on calcium turnover. The mechanism is unknown and, according to the results, not related to complement inhibition.

The roles of complement factor C5a and CINC-1 in glucose transport, ultrafiltration, and neutrophil recruitment during peritoneal dialysis.

BACKGROUND: In a recent experimental study, we showed that low molecular weight heparin improved ultrafiltration and blocked complement activation and coagulation in a single peritoneal dialysis (PD) dwell. OBJECTIVE: The aim of the present study was to evaluate the possible contribution of the complement factor C5a and the potential interactions between C5a, the coagulation system, and cytokines of the interleukin (IL)-8 family (cytokine-induced neutrophil chemoattractant; CINC-1). METHODS: Nonuremic rats were exposed through an indwelling catheter to a single dose of 20 mL glucose-(2.5%) based filter-sterilized PD fluid, with or without the addition of anti-rat C5 antibody. The dwell fluid was analyzed 2 and 4 hours later concerning activation of the coagulation cascades, neutrophil recruitment, ultrafiltration volume; CINC-1, glucose, urea, and histamine concentrations; and ex vivo intraperitoneal chemotactic activity. RESULTS: The numbers of neutrophils and levels of thrombin-antithrombin complex (TAT) and CINC-1 increased significantly during the PD dwell. C5 blockade significantly reduced the levels of TAT and increased the ultrafiltration volumes at 2 hours. Glucose concentrations were significantly positively correlated to ultrafiltration volumes. CONCLUSIONS: Blockade of C5 leads to an increase in ultrafiltration, probably by a mechanism that involves a reduction in glucose transport. This effect may form a basis for improving PD efficiency in situations where high glucose transport limits ultrafiltration. Mechanisms connected to complement activation during PD may involve coagulation. Further studies of the intraperitoneal cascade systems under conditions of PD are indicated.

Peritoneal dialysis fluid-induced angiogenesis in rat mesentery is increased by lactate in the presence or absence of glucose.

Angiogenesis may be an important mechanism behind the functional deterioration of the peritoneum leading to ultrafiltration failure in peritoneal dialysis. The present study was designed to compare the angiogenic properties of lactate-, bicarbonate-, and pyruvate-buffered fluids, evaluated separately with and without glucose. Five different fluids (lactate and bicarbonate with and without 2.5% glucose and pyruvate without glucose) were studied for 5 weeks of twice-daily injections in rats. The respective buffers (40 mmol/l) were adjusted to pH 7.2, and sodium, chloride, calcium, and magnesium were present at standard concentrations. The mesenteric window model, based on observation of the translucent peritoneal sections of the small intestine mesentery, was used for immunohistochemical imaging of microvessels (RECA-1 antigen) and macrophages (ED1 and ED2 antigens). All fluids induced angiogenesis as compared with untreated controls. The lactate-buffered fluids induced larger vascularized zones than did their bicarbonate- and pyruvate-buffered counterparts. Angiogenesis was accompanied by a local recruitment of ED1 macrophages from blood. Addition of glucose to the lactate- and bicarbonate-buffered fluids did not seem to alter their pro-angiogenic properties. In conclusion, intraperitoneal exposure to lactate buffer, compared with bicarbonate, stimulates angiogenesis in the presence or absence of glucose.

Microvascular behavior and effects of sonazoid microbubbles in the cremaster muscle of rats after local administration.

OBJECTIVE: The purpose of this study was to observe Sonazoid perfluorobutane microbubbles (GE Healthcare, Amersham, Buckinghamshire, England) in and their effects on the cremaster capillary microcirculation of rats. METHODS: Sonazoid (0.3 x 10(9) microbubbles in 0.5 mL) was observed by intravital microscopy in the cremaster muscle after retrograde administration into the femoral artery of 6 animals. Microbubble and microvessel diameters and blood flow velocities and the overall mean and SD of the 1-minute volume flow through the microscopic field were calculated from the 2 to 4 capillaries observed in the field of each animal. Fluorescein isothiocyanate-dextran leakage was used to assess extravasation after microbubble passage. RESULTS: seconds, respectively, before they were released and capillary flow normalized. No microbubble size changes, damming, or coalescence of bubbles and no changes in microvessel diameter or microvascular blood flow velocities, volume flow, or perfusion heterogeneity occurred during or after the passage of the Sonazoid suspension or the vehicle. No fluorescein isothiocyanate-dextran leakage was observed. CONCLUSIONS: The passage of Sonazoid bubbles at concentrations higher than those expected after intravenous administration of the Sonazoid did not durably impair microvascular perfusion, structural integrity, or macromolecular retention in the rat cremaster muscle. The duration of discrete capillary obstructions was short and in all cases comparable with that of naturally occurring leukocyte plugging.

Low molecular weight heparin improves peritoneal ultrafiltration and blocks complement and coagulation.

OBJECTIVES: Clinical studies have demonstrated that the intraperitoneal (IP) complement and coagulation systems are activated in peritoneal dialysis (PD) patients. In animal models, low molecular weight heparin (LMWH) was seen to inhibit peritoneal angiogenesis, and related compounds have increased ultrafiltration volumes after repeated administration to PD patients. The present study evaluated the effects of LMWH on ultrafiltration, coagulation, and complement activation during a single PD dwell. DESIGN: Rats were exposed to a single dose of 20 mL 2.5% glucose-based, filter-sterilized PD fluid, with or without supplementation with LMWH. The PD fluid was administered either as an IP injection or as an infusion through an indwelling catheter. The dwell fluid was analyzed 2 hours later concerning activation of the complement and coagulation cascades, chemotactic activity, neutrophil recruitment, ultrafiltration volume, and glucose and urea concentrations. RESULTS: Exposure to PD fluid induced activation of IP complement [formation of C3a (desArg) and increase of C5a-dependent chemotactic activity] and coagulation (formation of thrombin-antithrombin complex) and recruitment of neutrophils. In the case of IP injection, neutrophil recruitment and complement activation were inhibited by LMWH. In both models, LMWH inhibited thrombin formation, reduced complement-dependent chemotactic activity, and increased the IP fluid volume, indicating an improved ultrafiltration. CONCLUSIONS: The acute inflammatory reaction to PD fluid involves the complement and coagulation cascades. Addition of LMWH to the PD fluid improves ultrafiltration, inhibits formation of thrombin, and potentially blocks C5a activity. The present results motivate further investigations of the IP cascade systems in PD.

Biocompatibility of peritoneal dialysis fluids: long-term exposure of nonuremic rats.

OBJECTIVES: Long-term peritoneal dialysis (PD) leads to structural and functional changes in the peritoneum. The aim of the present study was to investigate the long-term effects of PD fluid components, glucose and glucose degradation products (GDP), and lactate-buffered solution on morphology and transport characteristics in a nonuremic rat model. METHODS: Rats were subjected to two daily intraperitoneal injections (20 mL/day) during 12 weeks of one of the following: commercial PD fluid (Gambrosol, 4%; Gambro AB, Lund, Sweden), commercial PD fluid with low GDP levels (Gambrosol trio, 4%; Gambro AB), sterile-filtered PD fluid (4%) without GDP, or a glucose-free lactate-buffered PD fluid. Punctured and untreated controls were used. Following exposure, the rats underwent a single 4-hour PD dwell (30 mL, 4% glucose) to determine peritoneal function. Additionally, submesothelial tissue thickness, percentage of high mesothelial cells (perpendicular diameter > 2 microm), vascular density, vascular endothelial growth factor (VEGF), and transforming growth factor (TGF) beta1 mRNA expression were determined. Submesothelial collagen concentration was estimated by van Gieson staining. RESULTS: Submesothelial tissue thickness and vascular density, mediated by VEGF and TGFbeta production, in the diaphragmatic peritoneum increased significantly in rats exposed to any PD fluid. Gambrosol induced a marked increased fibrosis of the hepatic peritoneum. A significant increase in high mesothelial cells was observed in the Gambrosol group only. Net ultrafiltration was reduced in the Gambrosol and in the glucose-free groups compared to untreated controls. Small solute transport was unchanged, but all groups exposed to fluids showed significantly increased lymph flow. CONCLUSIONS: Our results show that long-term exposure to different components of PD fluids leads to mesothelial cell damage, submesothelial fibrosis, and neoangiogenesis. Mesothelial cell damage could be connected to the presence of GDP; the other changes were similar for all fluids. Peritoneal transport characteristics did not change in any consistent way and the neoangiogenesis observed was not paralleled by increased solute transport.