Upgrade of the ultracold neutron source at the pulsed reactor TRIGA Mainz

The performance of the upgraded solid deuterium ultracold neutron source at the pulsed reactor TRIGA Mainz is described. The current configuration stage comprises the installation of a He liquefier to run UCN experiments over long-term periods, the use of stainless steel neutron guides with improved transmission as well as sputter-coated non-magnetic $^{58}$NiMo alloy at the inside walls of the thermal bridge and the converter cup. The UCN yield was measured in a `standard' UCN storage bottle (stainless steel) with a volume of 32 litres outside the biological shield at the experimental area yielding UCN densities of 8.5 /cm$^3$; an increase by a factor of 3.5 compared to the former setup. The measured UCN storage curve is in good agreement with the predictions from a Monte Carlo simulation developed to model the source. The growth and formation of the solid deuterium converter during freeze-out are affected by the ortho/para ratio of the H$_2$ premoderator.Comment: 12 pages, 7 figure

Pre-Transplant Heavy Smoking Is Associated with Reduced Survival After Heart Transplantation Due to Infection and Malignancy

Background: Tobacco smoking is a known risk factor for adverse cardiovascular events. Many patients after heart transplantation (HTX) have a history of smoking, but the prognostic role of pre-transplant smoking remains uncertain. We thus investigated the effects of pre-transplant heavy smoking (≥20 pack-years) on outcomes after HTX. Methods: This observational retrospective single-centre study included 639 patients receiving HTX at Heidelberg Heart Center between 1989 and 2019. Patients were stratified by intensity of pre-transplant smoking (<20 pack-years or ≥20 pack-years). Analysis covered donor and recipient demographics, post-transplant medications, mortality including causes of death after HTX, and early post-transplant atrial fibrillation (AF) after HTX. Results: A total of 219 of the 639 HTX recipients (34.3%) had a pre-transplant history of heavy smoking (≥20 pack-years). These patients showed an increased 5-year post-transplant mortality (44.3% versus 28.6%, p < 0.001) and had a higher percentage of death due to infection/sepsis (21.5% versus 12.1%, p = 0.002) as well as due to malignancy (5.5% versus 1.7%, p = 0.007). Multivariate analysis demonstrated pre-transplant heavy smoking (≥20 pack-years) as an independent risk factor for five-year mortality after HTX (HR: 2.173, 95% CI: 1.601–2.950, p < 0.001). Analysis of secondary outcomes also showed a significantly higher rate of 30-day post-transplant AF (17.8% versus 11.7%, p = 0.032) in patients with a pre-transplant history of heavy smoking (≥20 pack-years). Conclusions: Pre-transplant heavy smoking is associated with early post-transplant AF, lung cancer, infection, and reduced survival after HTX

Endothelium-derived hyperpolarizing factor-mediated renal vasodilatory response is impaired during acute and chronic hyperhomocysteinemia

BACKGROUND: Endothelial dysfunction is an early event in the development of vascular complications in hyperhomocysteinemia. Endothelial cells release a number of vasodilators, including NO and prostacyclin. Several lines of evidence have indicated the existence of a third vasodilator pathway, mediated by endothelium-derived hyperpolarizing factor (EDHF). EDHF is a major determinant of vascular tone in small resistance vessels. The influence of hyperhomocysteinemia on EDHF is unknown. The present in vivo study evaluates the integrity of the EDHF pathway in the renal microcirculation of rats with acute and chronic hyperhomocysteinemia. METHODS AND RESULTS: EDHF-mediated vasodilation was evaluated as the renal blood flow (RBF) response to intrarenal acetylcholine during systemic NO synthase and cyclooxygenase inhibition. Acute hyperhomocysteinemia induced by intravenous homocysteine did not affect EDHF-mediated vasodilation. In contrast, intravenous methionine with subsequent hyperhomocysteinemia impaired the EDHF-mediated RBF response. When the methionine infusion was preceded by adenosine periodate oxidized to prevent the cleavage of S-adenosylhomocysteine to homocysteine and adenosine, a similar impairment of EDHF was observed, but with normal homocysteine levels. Animals with chronic hyperhomocysteinemia induced by a high-methionine, low-B vitamin diet during 8 weeks had a severely depressed EDHF-mediated vasodilation compared with those on a standard diet. Endothelium-independent vasodilation to deta-NONOate and pinacidil was not affected in acute and chronic hyperhomocysteinemia, demonstrating intact vascular smooth muscle reactivity. CONCLUSIONS: EDHF-dependent responses are impaired in the kidney of hyperhomocysteinemic rats. Because EDHF is a major regulator of vascular function in small vessels, these findings have important implications for the development of microangiopathy in hyperhomocysteinemia

Early Pacemaker Dependency After Heart Transplantation Is Associated with Permanent Pacemaker Implantation, Graft Failure and Mortality

Aims: Patients after heart transplantation (HTX) often experience post-transplant bradycardia, but little is known about the outcomes of early pacemaker dependency after HTX. We compared post-transplant mortality, graft failure, and the requirement for the permanent pacemaker implantation of patients with and without early pacemaker dependency after HTX. Methods: We screened all adult patients for early pacemaker dependency after HTX (defined as immediately after surgery) who underwent HTX at Heidelberg Heart Center between 1989 and 2022. Patients were stratified by diagnosis and type of early pacemaker dependency after HTX (sinoatrial or atrioventricular conduction disturbance). Results: A total of 127 of 699 HTX recipients (18.2%) had early pacemaker dependency after HTX, including 52 patients with sinoatrial conduction disturbances (40.9%) and 75 patients with atrioventricular conduction disturbances (59.1%). Patients with early pacemaker dependency after HTX showed both increased 1-year overall mortality after HTX (55.9% vs. 15.2%, p p p p p < 0.001) permanent pacemaker implantation after HTX compared to patients without early pacemaker dependency after HTX. Conclusions: Patients with early pacemaker dependency after HTX had a significantly higher rate of post-transplant mortality, graft failure, and the requirement for permanent pacemaker implantation