Showing papers by "University of Kiel published in 1998"

Klebsiella spp. as Nosocomial Pathogens: Epidemiology, Taxonomy, Typing Methods, and Pathogenicity Factors

Abstract: Bacteria belonging to the genus Klebsiella frequently cause human nosocomial infections. In particular, the medically most important Klebsiella species, Klebsiella pneumoniae, accounts for a significant proportion of hospital-acquired urinary tract infections, pneumonia, septicemias, and soft tissue infections. The principal pathogenic reservoirs for transmission of Klebsiella are the gastrointestinal tract and the hands of hospital personnel. Because of their ability to spread rapidly in the hospital environment, these bacteria tend to cause nosocomial outbreaks. Hospital outbreaks of multidrug-resistant Klebsiella spp., especially those in neonatal wards, are often caused by new types of strains, the so-called extended-spectrum-β-lactamase (ESBL) producers. The incidence of ESBL-producing strains among clinical Klebsiella isolates has been steadily increasing over the past years. The resulting limitations on the therapeutic options demand new measures for the management of Klebsiella hospital infections. While the different typing methods are useful epidemiological tools for infection control, recent findings about Klebsiella virulence factors have provided new insights into the pathogenic strategies of these bacteria. Klebsiella pathogenicity factors such as capsules or lipopolysaccharides are presently considered to be promising candidates for vaccination efforts that may serve as immunological infection control measures.

von Willebrand Factor–Cleaving Protease in Thrombotic Thrombocytopenic Purpura and the Hemolytic–Uremic Syndrome

Abstract: Background Thrombotic thrombocytopenic purpura and the hemolytic–uremic syndrome are severe microvascular disorders of platelet clumping with similar signs and symptoms. Unusually large multimers of von Willebrand factor, capable of agglutinating circulating platelets under high shear stress, occur in the two conditions. We investigated the prevalence of von Willebrand factor–cleaving protease deficiency in patients with familial and nonfamilial forms of these disorders. Methods Plasma samples were obtained from 53 patients with thrombotic thrombocytopenic purpura or hemolytic–uremic syndrome. Von Willebrand factor–cleaving protease was assayed in diluted plasma samples with purified normal von Willebrand factor as the substrate. The extent of the degradation of von Willebrand factor was assessed by electrophoresis in sodium dodecyl sulfate–agarose gels and immunoblotting. To determine whether an inhibitor of von Willebrand factor–cleaving protease was present, we measured the protease activity in normal ...

Ink and Vinegar, a Simple Staining Technique for Arbuscular-Mycorrhizal Fungi

Abstract: We developed a reliable, inexpensive, and simple method for staining arbuscular-mycorrhizal fungal colonizations in root tissues. Apart from applications in research, this nontoxic, high-quality staining method also could be of great utility in teaching exercises. After adequate clearing with KOH, an ink-vinegar solution successfully stained all fungal structures, rendering them clearly visible.

Molecular Basis for the Generation in Pigs of Influenza A Viruses with Pandemic Potential

Abstract: Genetic and biologic observations suggest that pigs may serve as “mixing vessels” for the generation of human-avian influenza A virus reassortants, similar to those responsible for the 1957 and 1968 pandemics. Here we demonstrate a structural basis for this hypothesis. Cell surface receptors for both human and avian influenza viruses were identified in the pig trachea, providing a milieu conducive to viral replication and genetic reassortment. Surprisingly, with continued replication, some avian-like swine viruses acquired the ability to recognize human virus receptors, raising the possibility of their direct transmission to human populations. These findings help to explain the emergence of pandemic influenza viruses and support the need for continued surveillance of swine for viruses carrying avian virus genes.

Effect of the formation of the Isthmus of Panama on Atlantic Ocean thermohaline circulation

Abstract: The Late Cenozoic closure of the seaway between the North andSouth American continents is thought to have caused extensive changes in ocean circulation and Northern Hemisphere climate1,2 But the timing and consequences of the emergence of the Isthmus of Panama, which closed the seaway, remain controversial1,2,3,4,5 Here we present stable-isotope and carbonate sand-fraction records from Caribbean sediments which, when compared to Atlantic and Pacific palaeoceanographic records, indicate that the closure caused a marked reorganization of ocean circulation starting 46 million years ago Shallowing of the seaway intensified the Gulf Stream and introduced warm and saline water masses to high northern latitudes These changes strengthened deep-water formation in the Labrador Sea over the next million years — as indicated by an increased deep-water ventilation and carbonate preservation in the Caribbean Sea — and favoured early Pliocene warming of the Northern Hemisphere The evaporative cooling of surface waters during North Atlantic Deep Water formation would have introduced moisture to the Northern Hemisphere Although the pronounced intensification of Northern Hemisphere glaciation between 31 and 25 million years ago substantially lagged the full development of North Atlantic Deep Water formation, we propose that the increased atmospheric moisture content was a necessary precondition for ice-sheet growth, which was then triggered by the incremental changes in the Earth's orbital obliquity

Development of PCR primer systems for amplification of nitrite reductase genes (nirK and nirS) to detect denitrifying bacteria in environmental samples.

Abstract: A system was developed for the detection of denitrifying bacteria by the amplification of specific nitrite reductase gene fragments with PCR. Primer sequences were found for the amplification of fragments from both nitrite reductase genes (nirK and nirS) after comparative sequence analysis. Whenever amplification was tried with these primers, the known nir type of denitrifying laboratory cultures could be confirmed. Likewise, the method allowed a determination of the nir type of five laboratory strains. The nirK gene could be amplified from Blastobacter denitrificans, Alcaligenes xylosoxidans, and Alcaligenes sp. (DSM 30128); the nirS gene was amplified from Alcaligenes eutrophus DSM 530 and from the denitrifying isolate IFAM 3698. For each of the two genes, at least one primer combination amplified successfully for all of the test strains. Specific amplification products were not obtained with nondenitrifying bacteria or with strains of the other nir type. The specificity of the amplified products was confirmed by subsequent sequencing. These results suggest the suitability of the method for the qualitative detection of denitrifying bacteria in environmental samples. This was shown by applying one generally amplifying primer combination for each nir gene developed in this study to total DNA preparations from aquatic habitats.

Correlation between Arabian Sea and Greenland climate oscillations of the past 110,000 years

Abstract: Palaeoclimate studies have revealed the general high-frequency instability of Late Pleistocene climate—for example, the so-called Dansgaard–Oeschger and Heinrich events—on timescales of a few millennia, centuries or even decades1,11. Here we present evidence for a general relationship between low-latitude monsoonal climate variability and the rapid temperature fluctuations of high northern latitudes that are recorded in the Greenland ice records. Sediment cores from the northeastern Arabian Sea show laminated, organic-carbon-rich bands, reflecting strong monsoon-induced biological productivity, that correlate with the mild interstadial climate events in the northern North Atlantic region. In contrast, periods of lowered southwest monsoonal intensity, indicated by bioturbated, organic-carbon-poor bands, are associated with intervals of high-latitude atmospheric cooling and the injection of melt water into the North Atlantic basin. Our records suggest that Dansgaard–Oeschger and Heinrich events are strongly expressed in low-latitude (monsoonal) climate variability, suggesting the importance of common forcing agents such as atmospheric moisture and other greenhouse gases.

Gender Differences in Human Sepsis

Abstract: Background: In animal studies, gender differences were related to hormonal and immunologic changes that were associated with an increased susceptibility to sepsis in males. Objective: In a prospective study, gender differences in patients with surgical sepsis were evaluated in terms of survival, sex hormones, and proinflammatory as well as anti-inflammatory mediators. Setting: Surgical intensive care unit of a university hospital. Patients: Fifty-two patients (19 women and 33 men) with surgical sepsis. Measurements and Main Results: In a prospective study, tumor necrosis factor a and interleukin 6 bioactivity and plasma levels of interleukin 10 (using enzyme-linked immunosorbent assay), total testosterone, and 17-β estradiol (using radioimmunoassay) were determined on days 1, 3, 5, 7, 10, and 14 after diagnosis of sepsis. There were no differences in characteristics of patients in age (mean age, 55.4 years for women and 53. years for men) or cause and severity of sepsis (Acute Physiology and Chronic Health Evaluation II score, 17.3 for women and 18.5 for men; multiple organ dysfunction score, 9.9 vs 10.8, respectively). Although no difference could be found in the multiple organ dysfunction score from day 1 to day 28, the prognosis of sepsis was significantly different in women compared with men. Hospital-mortality rate was 70% (23 of 33 patients) in male and 26% (5 of 19) in female patients (P<.008, log-rank test). Bioactivity of tumor necrosis factor continuously increased in men after diagnosis of sepsis, with significantly elevated levels on day 10 (P<.05, Mann-Whitney U test with Bonferroni correction), whereas no difference was found for interleukin 6 bioactivity. Women displayed enhanced interleukin 10 levels compared with men from day 1 to day 10 that reached a significant difference on days 3 and 5 (P<.05). Total testosterone levels were below the normal range for men, and estradiol levels were initially increased in both men and postmenopausal women, with higher levels for women. Conclusions: In this prospective study, gender differences were confirmed in human sepsis, with a significantly better prognosis for women, which may be related to increased levels of anti-inflammatory mediators. The hypothetical different ratio of proinflammatory and anti-inflammatory mediators may be important for further therapeutic interventions in sepsis.

A competitive genetic algorithm for resource-constrained project scheduling

Abstract: In this paper we consider the resource-constrained project scheduling problem (RCPSP) with makespan minimization as objective. We propose a new genetic algorithm approach to solve this problem. Subsequently, we compare it to two genetic algorithm concepts from the literature. While our approach makes use of a permutation based genetic encoding that contains problem-specific knowledge, the other two procedures employ a priority value based and a priority rule based representation, respectively. Then we present the results of our thorough computational study for which standard sets of project instances have been used. The outcome reveals that our procedure is the most promising genetic algorithm to solve the RCPSP. Finally, we show that our genetic algorithm yields better results than several heuristic procedures presented in the literature. © 1998 John Wiley & Sons, Inc. Naval Research Logistics 45: 733–750, 1998

Eddy-induced enhancement of primary production in a model of the North Atlantic Ocean

Abstract: In steady state, the export of photosynthetically fixed organic matter to the deep ocean has to be balanced by an upward flux of nutrients into the euphotic zone1. Indirect geochemical estimates2 of the nutrient supply to surface waters have been substantially higher than direct biological and physical measurements3, particularly in subtropical regions. A possible explanation for the apparent discrepancy is that the sampling strategy of the direct measurements has under-represented episodic nutrient injections forced by mesoscale eddy dynamics, whereas geochemical tracer budgets integrate fluxes over longer time and space scales. Here we investigate the eddy-induced nutrient supply by combining two methods potentially capable of delivering synoptic descriptions of the ocean's state on a basin scale. Remotely sensed sea-surface height data from the simultaneous TOPEX/Poseidon and ERS-1 satellite missions are assimilated into a numerical eddy-resolving coupled ecosystem–circulation model of the North Atlantic Ocean. Our results indicate that mesoscale eddy activity accounts for about one-third of the total flux of nitrate into the euphotic zone (taken to represent new production) in the subtropics and at mid-latitudes. This contribution is not sufficient to maintain the observed primary production in parts of the subtropical gyre, where alternative routes of nitrogen supply will have to be considered.

Anastrozole versus Megestrol Acetate in the Treatment of Postmenopausal Women with Advanced Breast Carcinoma Results of a Survival Update Based on a Combined Analysis of Data from Two Mature Phase III Trials

Abstract: BACKGROUND. This report presents the results of a survival update based on the combined data from two studies that compared the efficacy and tolerability of anastrozole (1 or 10 mg once daily), a selective, nonsteroidal aromatase inhibitor administered orally, and megestrol acetate (40 mg 4 times daily) in the treatment of postmenopausal women with advanced breast carcinoma whose disease had progressed after treatment with tamoxifen. METHODS. Two randomized, parallel-group, multicenter trials were conducted, involving a total of 764 patients. The two trials were identical in design; both were double blind for anastrozole and open label for megestrol acetate. Overview analyses were conducted with the intent of strengthening the interpretation of results from each trial. The median follow-up duration for this survival update was 31 months. RESULTS. At the clinical dose of 1 mg daily, anastrozole demonstrated a statistically significant survival advantage over megestrol acetate, with a hazard ratio of 0.78 (P , 0.025)(0.60 , 97.5% confidence interval [CI] ,1.0). The 1 mg anastrozole group also had a longer median time to death (26.7 months) compared with 22.5 months for the megestrol acetate group. The 10 mg anastrozole group also had a survival benefit over the megestrol acetate group, with a hazard ratio of 0.83 (P 5 0.09, not significant)(0.64 , 97.5% CI , 1.1). Higher 2-year survival rates were observed for both anastrozole treatment groups than for the megestrol acetate group (56.1%, 54.6%, and 46.3% for the groups given 1 mg anastrozole, 10 mg anastrozole, and megestrol acetate, respectively).

AT2 Receptor Stimulation Increases Aortic Cyclic GMP in SHRSP by a Kinin-Dependent Mechanism

Abstract: In the present study we tested the hypothesis whether an angiotensin AT2 receptor-mediated stimulation of the bradykinin (BK)/nitric oxide (NO) system can account for the effects of AT1 receptor antagonism on aortic cGMP described previously in SHRSP. Adult SHRSP were treated for 4 hours with angiotensin II (ANG II) (30 ng/kg per min IV) or vehicle (0.9% NaCl I.V.). Animals were pretreated with vehicle, losartan (100 mg/kg P.O.), PD 123319 (30 mg/kg I.V.), losartan plus PD 123319, icatibant (500 microg/kg I.V.), N(G)-nitro-L-arginine methyl ester (L-NAME; 1 mg/kg I.V.), or minoxidil (3 mg/kg I.V.). Mean arterial blood pressure (MAP) was continuously monitored over the 4-hour experimental period, and plasma ANG II and aortic cGMP were measured by RIA at the end of the study. ANG II infusion over 4 hours raised MAP by about 20 mm Hg. Losartan alone or losartan plus ANG II as well as minoxidil plus ANG II markedly reduced blood pressure when compared to vehicle-treated or ANG II-treated animals, respectively. Plasma levels of ANG II were increased 2-fold by ANG II infusion alone or by ANG II in combination with icatibant, L-NAME, or minoxidil. The increase in plasma ANG II levels was even more pronounced after losartan treatment. Aortic cGMP content was significantly increased by ANG II, losartan, losartan plus ANG II, and minoxidil plus ANG II by 60%, 45%, 68%, and 52%, respectively (P<.05). The effects of ANG II and of losartan plus ANG II on aortic cGMP content were both blocked by cotreatment with the AT2 receptor antagonist PD 123319. Icatibant and L-NAME abolished the effects of ANG II on aortic cGMP. Our results demonstrate the following: (1) ANG II increases aortic cGMP by an AT2 receptor-mediated action because the effect could be prevented by an AT2 receptor antagonist; (2) the effect of ANG II was not secondary to blood pressure increase because it remained under reduction of MAP with minoxidil; (3) losartan increased aortic cGMP most likely by increasing plasma ANG II levels with a subsequent stimulation of AT2 receptors; and (4) the effects of AT2 receptor stimulation are mediated by BK and, subsequently, NO because they were abolished by B2 receptor blockade as well as by NO synthase inhibition.

The cold event 8200 years ago documented in oxygen isotope records of precipitation in Europe and Greenland

Abstract: Stable oxygen isotope ratios of ostracod valves in Late Glacial and Holocene sediments of core AS 92-5 from deep lake Ammersee (southern Germany) reflect variations of mean oxygen isotope ratios in past atmospheric precipitation. The record reconfirms the strong similarity of climate evolution in Europe and Greenland during the last deglaciation. For the first time in Europe, we find a 200-year-long negative δ18O-excursion, which is contemporaneous with the strongest negative δ18O-excursion in the Greenland ice around 8.2 ky before present. The 8.2 ky isotopic event on both sides of the North Atlantic ocean is interpreted as a cold period, most probably induced by a perturbation of the North Atlantic thermohaline circulation. We discuss two possible triggering mechanisms: (1) weak forcing (as proposed by Alley et al.), and (2) forcing by a strong and sudden freshwater pulse from the collapse of the Hudson Ice Dome.

Structure, function and metabolism of sialic acids

Abstract: Sialic acids represent a family of sugar molecules with an unusual and highly variable chemical structure that are found mostly in the terminal position of oligosaccharide chains on the surface of cells and molecules. These special features enable them to fulfil several important and even diametrical biological functions. Because of the great importance of sialic acids, it is also worth having a look at their metabolism in order to get an idea of the intimate connection between structure and function of these fascinating molecules and the often serious consequences that result from disturbances in the balance of metabolic reactions. The latter can be due to genetic disorders that result in the absence of certain enzyme activity, leading to severe illness or even to death.

Collagenous fibril texture of the human knee joint menisci.

Abstract: Anatomical and clinical literature describes the arrangement of collagen fibrils in the human meniscus as being "arcade-like". The "arcade-like" orientation, mainly running in a radial direction in the internal circumference and in a circular direction in the external circumference, was found in polarization light microscopic studies. This, however, does not provide a mechanical explanation for the direction of meniscus tears. In view of this contradiction collagen fibrils in the menisci of adults aged from 18 to 85 years were exposed layer-by-layer to study their arrangement by scanning electron microscopy. The results obtained by this procedure were compared to the path of the split lines. Scanning electron microscopy reveals three distinct layers in the meniscus cross section: (1) The tibial and femoral sides of the meniscus surfaces are covered by a meshwork of thin fibrils with a diameter of approximately 30 nm. (2) Beneath the superficial network there is a layer of lamellalike collagen fibril bundles on the tibial and femoral surface. In the area of the external circumference of the anterior and posterior segments the bundles of collagen fibrils are arranged in a radial direction. In all other parts the collagen fibril bundles intersect at various angles. (3) The main portion of the meniscus collagen fibrils are located in the central region between the femoral and the tibial surface layers. Everywhere in the central main portion of the meniscus the bundles of collagen fibrils are orientated in a circular manner. The split lines in the region of the internal circumference of the menisci are arranged in a circular manner, generally running in a radial direction in the portions adjacent to the base. Scanning electron microscopy reveals that the direction of the split lines depends on the orientation of the collagen fibrils in the superficial lamellar layer. The arcade-like path of the collagen fibrils described in the literature can not be confirmed either by scanning electron microscopy or by the course of the split lines. The circular arrangement of collagen fibrils in the central portion of the meniscus provides a functional explanation for the longitudinal orientation of the majority of tears in the meniscus tissue.

Crystal structure of human arylsulfatase A: the aldehyde function and the metal ion at the active site suggest a novel mechanism for sulfate ester hydrolysis.

Abstract: Human lysosomal arylsulfatase A (ASA) is a prototype member of the sulfatase family. These enzymes require the posttranslational oxidation of the −CH2SH group of a conserved cysteine to an aldehyde...

IL-4 Induces Eotaxin: A Possible Mechanism of Selective Eosinophil Recruitment in Helminth Infection and Atopy

Abstract: A common feature of some parasitic infections and allergic and atopic skin diseases is the involvement of Th2 lymphocytes and the dermal appearance of eosinophils (Eos). Because Th2 lymphocytes apparently do not release Eo attractants, we addressed the question of whether the Th2 cytokine IL-4 induces its production in dermal fibroblasts. We therefore stimulated fibroblasts with IL-4. HPLC investigation of supernatants revealed a single Eo chemotactic protein, which was purified to homogeneity giving a single 13-kDa band upon SDS-PAGE analyses. Peptide mapping with subsequent amino acid sequencing revealed an Eo-selective chemotaxin, which consists of a mixture of N-terminally truncated and O-glycosylated forms of the chemokine eotaxin. Other chemokines such as RANTES, MCP-3, MCP-4, or MIP-1alpha were not detected as Eo chemotaxins under these conditions. Using reverse transcriptase-PCR techniques, we found that IL-4 dose and time dependently induces eotaxin mRNA in dermal fibroblasts. Stimulation with IL-4 and TNF-alpha caused a 10- to 20-fold increase of the release of three biochemically different eotaxin forms, each consisting of a mixture of N-terminally truncated and O-glycosylated variants having the same backbone amino acid sequence but different specific activities. Our findings support the hypothesis that eosinophil recruitment seen in IL-4-mediated skin reactions, at least in part, may be due to Th2 cytokine-mediated induction of eotaxin in dermal fibroblasts.

Allogeneic bone marrow transplantation vs filgrastim-mobilised peripheral blood progenitor cell transplantation in patients with early leukaemia: First results of a randomised multicentre trial of the European Group for Blood and Marrow Transplantation

Abstract: In a multicentre trial involving 20 transplant centres from 10 countries haematopoietic stem cells were obtained either from the bone marrow of 33 sibling donors or from the peripheral blood of 33 such donors after administration of filgrastim (10 μg/kg/day). The haematopoietic stem cells were infused into their HLA-identical recipients suffering from acute leukaemias in remission or chronic myeloid leukaemia in chronic phase. PBPC donors tolerated filgrastim administration and leukapheresis well with the most frequent side-effects being musculoskeletal pain, headache, and mild increases of LDH, AP, Gamma-GT or SGPT. Pain and haematoma at the harvest site and mild anaemia were the most frequent complaints of BM donors. Severe or life-threatening complications were not seen with any type of harvest procedure. Time to platelet recovery greater than 20 × 109/l was 15 days (95% confidence interval (CI) 13–16 days) in the PBPCT group and 19 days (CI 16–25) in the BMT group. Time to neutrophil recovery greater than 0.5 × 109/l was 14 days (CI 12–15 days) in the PBPCT group as compared to 15 days (CI 15–16 days) in the BMT group. The numbers of platelet transfusions administered to PBPCT and BMT patients were 12 (range: 1–28) and 10 (range: 3–39), respectively. Sixteen patients (48%) transplanted with bone marrow and 18 patients (54%) transplanted with PBPC developed acute GVHD of grades II–IV; acute GVHD of grades III or IV developed in six (18%) and seven (21%) patients, respectively. Kaplan–Meier plots for transplant-related mortality until day 100 and leukaemia-free survival at a median of 400 days after BMT or PBPCT showed no significant differences. Administration of filgrastim and leukapheresis in normal donors were feasible and well tolerated. The number of days with restricted activity and of nights spent in hospital was lower in donors of PBPC. Transplantation of PBPC to HLA-identical siblings with early leukaemia resulted in earlier platelet engraftment. The incidence of moderate to severe acute GVHD, transplant-related mortality, and leukaemia-free survival did not show striking differences. Further investigation of allogeneic PBPCT as a substitute for allogeneic BMT is warranted.

Genomes, genes and junk: the large-scale organization of plant chromosomes

Abstract: Plants from wide taxonomic groupings have similar genes and ordering of genes along the chromosomes. However, the repetitive DNA, much of no known function and often constituting the majority of the genome, varies extensively from species to species in absolute amount, sequence and dispersion pattern. Despite this, it is known that families of repeated DNA motifs each have a characteristic genomic location within a genus, and that there are different constraints on the evolution of repetitive DNA and genes. There are now enough data about different types of repetitive DNA—from sequencing, Southern analysis and in situ hybridization—to build a model of the organization of a typical plant genome, and apply it to gene cloning, evolutionary studies and gene transfer.

Stabilization of emulsions by heterocoagulation of clay minerals and layered double hydroxides

Abstract: Paraffin/water emulsions were stabilized by colloidal particles without surface active agents. Mixtures of two types of particles with opposite signs of charge were used: a layered double hydroxide (the hydroxide layers carry positive charges) and the clay mineral montmorillonite (the silicate layers carry negative charges). The emulsions were very stable and did not separate a coherent oil phase. The stability of the emulsion (no oil coalescence after centrifugation) was independent of the mixing ratio of both the compounds when the total solid content was >0.5%. Solid contents up to 2.0% were optimal. In contrast to stability, flow behavior of the emulsion was dependent on the mass fraction χ of the hydroxide. The maxima of viscosity and yield value were observed at χ≈0.2–0.3; the emulsion showed pronounced antithixotropic behavior. Weak thixotropic properties, smaller viscosities and yield values were observed at χ≤0.2 and ≥0.5. In the absence of the clay mineral, the double hydroxide particles stabilize by forming envelopes around the oil droplets. Addition of bentonites creates a three-dimensional network of particles with high elasticity which impedes coalescence of the oil droplets.

Diffusion of metals in polymers

Abstract: First information on metal diffusion in polymers resulted from surface spectroscopies which mainly provided insight into chemical interactions of metals at polymer surfaces and into their growth mode. Medium energy ion scattering, electron microscopy, atomic force microscopy, and second-harmonic generation revealed a strong tendency of metals of low and intermediate reactivity to form clusters when deposited onto polymers. The interplay of diffusion and aggregation was also studied by Monte Carlo simulations. Metal diffusivities were obtained from radiotracer and Rutherford backscattering measurements. The available results show that reactive metals do not have any long-range mobility and are effective diffusion barriers. In contrast, isolated atoms of less reactive metals diffuse deep into polymers at elevated temperatures. However, the very pronounced aggregation tendency of these metals effectively impedes diffusion unless they are deposited at rates of the order of monolayers per minute or lower. Nevertheless, traces of noble metals always diffuse into polymers during the early stages of metal deposition, whereas no significant diffusion occurs from a continuous metal film. Even noble metal diffusivities are many orders of magnitude smaller than diffusivities of non-reactive gas molecules and largely decoupled from polymer dynamics. This is attributed to a pronounced reduction in the local chain mobility near metal atoms, e.g., by temporary metal-atom-induced crosslinking.