Ecosystem engineers in the extreme: The modest impact of marmots on vegetation cover and plant nitrogen and phosphorus content in a cold, extremely arid mountain environment.

Burrowing mammals strongly impact plant communities. One of the main effects is accelerating nutrient cycling and thus promoting plant growth. This mechanism is well-studied in grasslands and alpine habitats, but less is known about this phenomenon in arid, cold mountain environments. We studied ecosystem engineering by long-tailed marmots (Marmota caudata) by measuring the content of plant nitrogen and phosphorus, as well as nitrogen stable isotopes in plant biomass and marmot feces in a distance gradient up to 20 m from marmot burrows in an extremely arid glacier valley in Eastern Pamir, Tajikistan. We also captured aerial images of the area inhabited by marmots to study the spatial distribution of vegetation. There was a weak relationship between the presence of burrows and vegetation cover on soil not covered by burrow material. Burrow mounds were not colonized by plants, as opposed to other studies, where mounds are often microhabitats that enhance plant diversity. A significant increase in N and P in aboveground green plant biomass in the proximity of burrows was found in one out of six studied plant species. Contrary to our expectations, stable N isotopes did not give further insight into N routing. We assume that plant growth is strongly limited by water availability, which prevents them from utilizing the local increase in nutrients, certainly provided by marmot activity. The results are contrary to numerous studies, which showed that the role of burrowing animals as ecosystem engineers increases with increasing abiotic stress, including aridity. This shows a lack of this type of study at the end of the gradient of abiotic factors.

Results of liver transplantation in the Department of General, Transplant and Liver Surgery at the Medical University of Warsaw in patients with chronic hepatitis B and C viruses infection.

INTRODUCTION: Cirrhosis related to hepatitis C virus (HCV) and hepatitis B virus (HBV) infection is the most frequent indication for liver transplantation worldwide. Progress in prophylaxis of posttransplant HBV recurrence has led to major improvements in long-term outcomes of patients after liver transplantation. Conversely, impaired posttransplant survival of patients with HCV infection was reported in several studies, mainly due to recurrence of viral infection. The purpose of this study was to compare long-term results of liver transplantation between patients with HBV monoinfection, HCV monoinfection and HBV/HCV coinfection. MATERIAL AND METHODS: A total of 1090 liver transplantations were performed in the Department of General, Transplant and Liver Surgery in cooperation with the Department of Immunology, Internal Medicine, and Transplantology at the Transplantation Institute Medical University of Warsaw between December 1994 and May 2012. After exclusion of patients with cirrhosis of non-viral etiology, patients with malignant tumors, and patients with acute liver failure, the final study cohort comprised 209 patients with HBV (HBV+/HCV- subgroup; n = 56) or HCV (HBV-/HCV+ subgroup; n = 119) monoinfection or HBV/HCV coinfection (HBV+/HCV+; n = 34). These subgroups of patients were compared in terms of long-term results of transplantations, defined by 5-year patient and 5-year graft survival estimates. RESULTS: Overall and graft survival rates after 5-years for the whole study cohort were 74.5% and 72.6%, respectively. Five-year overall survival was 70.4% for patients within the HBV+/HCV- subgroup, 77.8% for patients within the HBV-/HCV+ subgroup, and 68.5% for patients within the HBV+/HCV+ subgroup. The corresponding rates of graft survival were 67.0%, 76.3%, and 68.5% for patients within the HBV+/HCV-, HBV-/ HCV+, and HBV+/HCV+ subgroups, respectively. Observed differences were non-significant, both in terms of overall (p = 0.472) and graft (p = 0.461) survival rates. CONCLUSIONS: Both overall and graft survival rates after liver transplantations performed in the Department of General, Transplant and Liver Surgery in cooperation with the Department of Immunology, Internal Medicine, and Transplantology at the Transplantation Institute Medical University of Warsaw in patients with HBV and HCV infection are comparable to those reported by other European and American centers. In contrast to other studies, obtained results do not confirm the negative impact of HCV infection on long-term outcomes of patients.

1000 liver transplantations at the Department of General, Transplant and Liver Surgery, Medical University of Warsaw--analysis of indications and results.

THE AIM OF THE STUDY: was to analyze indications and results of the first one thousand liver transplantations at Chair and Clinic of General, Transplantation and Liver Surgery, Medical University of Warsaw. MATERIAL AND METHODS: Data from 1000 transplantations (944 patients) performed at Chair and Clinic of General, Transplantation and Liver Surgery between 1994 and 2011 were analyzed retrospectively. These included 943 first transplantations and 55 retransplantations and 2 re-retransplantations. Frequency of particular indications for first transplantation and retransplantations was established. Perioperative mortality was defined as death within 30 days after the transplantation. Kaplan-Meier survival analysis was used to estimate 5-year patient and graft survival. RESULTS: The most common indications for first transplantation included: liver failure caused by hepatitis C infection (27.8%) and hepatitis B infection (18%) and alcoholic liver disease (17.7%). Early (< 6 months) and late (> 6 months) retransplantations were dominated by hepatic artery thrombosis (54.3%) and recurrence of the underlying disease (45%). Perioperative mortality rate was 8.9% for first transplantations and 34.5% for retransplantations. Five-year patient and graft survival rate was 74.3% and 71%, respectively, after first transplantations and 54.7% and 52.9%, respectively, after retransplantations. CONCLUSIONS: Development of liver transplantation program provided more than 1000 transplantations and excellent long-term results. Liver failure caused by hepatitis C and B infections remains the most common cause of liver transplantation and structure of other indications is consistent with European data.