An infectious disease model considering the age of infection

Development of a model based on integro-differential equations to improve the prediction od disease dynamics at change points

An infectious disease model considering the age of infection

Development of a model based on integro-differential equations to improve the prediction od disease dynamics at change points

Effect of Apheresis for ABO and HLA Desensitization on Anti-Measles Antibody Titers in Renal Transplantation

Desensitization strategies for ABO-incompatible renal transplants with plasma exchange (PE) or specific immunoadsorption (IA) decrease immunoglobulin levels. After recent measles outbreak and decreasing vaccination rates, we studied the impact of apheresis on anti-measles antibodies. Anti-measles antibodies were measured before desensitization, before transplantation and during followup in 12 patients with ABO incompatibility (2x PE only, 8x IA only, and 2x IA and PE) and 3 patients with donor-specific HLA antibodies (all PE). Patients received rituximab, IVIG, and standard immunosuppressive therapy. All patients had detectable anti-measles antibodies before desensitization (mean 3238 mU/l, range 560–8100). After 3–6 PE sessions, titers decreased significantly to 1710 mU/l (P < 0.05), in one patient to nondetectable values, while IA only maintained protective titers. After a median followup of 64 days, anti-measles antibodies returned to baseline in all patients. Immunity against measles was temporarily reduced by apheresis but remained detectable in most patients at time of transplantation. Desensitization maintains long-term protective immunity against measles

State Transitions in the Green Alga Scenedesmus Obliquus Probed by Time-Resolved Chlorophyll Fluorescence Spectroscopy and Global Data Analysis

Decay-associated fluorescence spectra of the green alga Scenedesmus obliquus have been measured by single-photon timing with picosecond resolution in various states of light adaptation. The data have been analyzed by applying a global data analysis procedure. The amplitudes of the decay-associated spectra allow a determination of the relative antenna sizes of the photosystems. We arrive at the following conclusions: (a) The fluorescence kinetics of algal cells with open PS II centers (F(0) level) have to be described by a sum of three exponential components. These decay components are attributed to photosystem (PS) I (τ ≈ 85 ps, λ(max)(em) ≈ 695-700 nm), open PS II α-centers (τ ≈ 300 ps, λ(max)(em) = 685 nm), and open PS II β-centers (τ ≈ 600 ps, λ(max)(em) = 685 nm). A fourth component of very low amplitude (τ ≈ 2.2-2.3 ns, λ(max)(em) = 685 nm) derives from dead chlorophyll. (b) At the F(max) level of fluorescence there are also three decay components. They originate from PS I with properties identical to those at the F(0) level, from closed PS II α-centers (τ ≈ 2.2 ns, λ(max)(em) = 685 nm) and from closed PS β-centers (τ ≈ 1.2 ns, λ(max)(em) = 685 nm). (c) The major effect of light-induced state transitions on the fluorescence kinetics involves a change in the relative antenna size of α- and β-units brought about by the reversible migration of light-harvesting complexes between α-centers and β-centers. (d) A transition to state II does not measurably increase the direct absorption cross-section (antenna size) of PS I. Our data can be rationalized in terms of a model of the antenna organization that relates the effects of state transitions and light-harvesting complex phosphorylation with the concepts of PS II α,β-heterogeneity. We discuss why our results are in disagreement with those of a recent lifetime study of Chlorella by M. Hodges and I. Moya (1986, Biochim. Biophys. Acta., 849:193-202)

Mineral quantification of a Jordan Cretaceous outcrop (Section GM3, Ghawr Al Mazar, Ghor al Mazrar)

Cyclic fluctuations in global sea level during epochs of warm greenhouse climate have remained enigmatic, because absence or subordinate presence of polar ice during these periods precludes an explanation by glacio-eustatic forcing. An alternative concept suggests that the water-bearing potential of groundwater aquifers is equal to that of ice caps and that changes in the dynamic balance of aquifer charge versus discharge, as a function of the temperature-related intensity of the hydrological cycle, may have driven eustasy during warm climates. However, this idea has long been neglected for two reasons: 1) the large storage potential of subsurface aquifers was confused with the much smaller capacity of rivers and lakes and 2) empirical data were missing that document past variations in the hydrological cycle in relation to eustasy. In the present study we present the first empirical evidence for changes in precipitation, continental weathering intensity and evaporation that correlate with astronomically (long obliquity) forced sea-level cycles during the warmest period of the Cretaceous (Cenomanian-Turonian). We compare sequence-stratigraphic data with changes in the terrigenous mineral assemblage in a low-latitude marine sedimentary sequence from the equatorial humid belt at the South-Tethyan margin (Levant carbonate platform, Jordan), thereby avoiding uncertainties from land-ocean correlations. Our data indicate covariance between cycles in weathering and sea level: predominantly chemical weathering under wet climate conditions is reflected by dominance of weathering products (clays) in deposits that represent sea-level fall (aquifer charge > discharge). Conversely, preservation of weathering-sensitive minerals (feldspars, epidote and pyroxenes) in transgressive sediments reflects decreased continental weathering due to dryer climate (aquifer discharge > charge). Based on our results we suggest that aquifer-eustasy represents a viable alternative to glacio-eustasy as a driver of cyclic 3rd-order sea-level fluctuations during the middle Cretaceous greenhouse climate, and it may have been a pervasive process throughout Earth history

Carbonate content and δ¹³C record of a Jordan Cretaceous outcrop (Section GM3 (Ghawr Al Mazar (Ghor al Mazrar))

An evaluation of the global synchronicity and duration of "3rd-order" sea-level fluctuations during the Cretaceous greenhouse has been hampered by poor constraints on potential climatic and tectonic drivers, and limitations of geochronology and chronostratigraphic correlation. To provide insight into the nature of such sea-level fluctuations, here we present a new Late Cretaceous record from the Jordanian Levant Platform, comprising a detailed physical-, bio-, chemo- and sequence stratigraphy. Carbonate content of these strata reflects overall sequence stratigraphic development, and demonstrates a dramatic 3rd-order-scale cycle that is also apparent in the d°C record. Updated radioisotopic constraints and astrochronologic testing provide support for the inference of an ~1 million year long sea-level oscillation associated with this 3rd-order cycle, which likely reflects a long-period obliquity (1.2 Myr) control on eustasy and stratigraphic sequence development, linked to the global carbon cycle. The observation of cyclic sea-level fluctuations on this time scale suggests sustained global modulation of continental fresh-water-storage. The hypothesized link between astronomical forcing and sea-level forms a baseline approach in the global correlation of sequence boundaries

The biological significance of lipogenesis in Nasonia vitripennis

Parasitic wasps have long been thought to be unable to synthesize fatty acids de novo, but recent C-13-labelling studies have challenged this view. It remained unclear, however, whether the reported biosynthesis rates are of biological relevance. Here, we show in Nasonia vitripennis that ageing females with partly depleted lipid reserves produce biologically relevant amounts of fatty acids de novo. Females with varying oviposition history (0-48 h) prior to feeding 20% C-13-labelled glucose solution showed C-13-incorporation rates of (mean +/- SEM) 30 +/- 2%, 50 +/- 2%, 49 +/- 3% and 21 +/- 2% in palmitic, stearic, oleic and linoleic acid, respectively. The absolute amounts of fatty acids synthesized de novo across treatments corresponded to 28 +/- 3 egg lipid equivalents. Females incorporated de novo synthesized fatty acids into their eggs, and glucose-fed females laid more eggs than water-fed control females. The number of eggs laid prior to glucose feeding did not correlate with the degree of lipogenesis, but the amounts of de novo synthesized fatty acids correlated with constitutive (not synthesized de novo) fatty acids. Hence, glucose feeding has a twofold effect on the fatty acid status of N. vitripennis females by decelerating the catabolism of existing fat reserves and partially replenishing ebbing fat reserves by lipogenesis

Studies on Chromophore Coupling in Isolated Phycobiliproteins: II. Picosecond Energy Transfer Kinetics and Time-Resolved Fluorescence Spectra of C-Phycocyanin from Synechococcus 6301 as a Function of the Aggregation State

The fluorescence kinetics of C-Phycocyanin in the monomeric, trimeric, and hexameric aggregation states has been measured as a function of the emission wavelength with picosecond resolution using the single-photon timing technique. All the decay curves measured at the various emission wavelengths were analyzed simultaneously by a global data analysis procedure. A sum of four exponentials was required to fit the data for the monomers and trimers. Only in the case of the hexamers, a three-exponential model function proved to be nearly sufficient to describe the experimental decays. The lifetime of those fluorescence components reflecting energy transfer decreased with increasing aggregation. This is due to the increased number of efficient acceptor molecules next to a donor in the higher aggregates. In all aggregates the shortest-lived component, ranging from 50 ps for monomer to 10 ps for hexamers, is observed as a decay term (positive amplitude) at short emission wavelength. At long emission wavelength it turns into a rise term (negative amplitude). The lifetime of a second ps-component ranges from 200 ps for monomers to 50 ps for hexamers. The long-lived (ns) fluorescence is inhomogeneous in monomers and trimers, showing two lifetimes of ∼0.6 and 1.3 ns. The latter one carries the larger amplitude. The amplitudes of the kinetic components in the fluorescence decays are presented as time-resolved component spectra. A theoretical model has been derived to rationalize the observed fluorescence kinetics. Using symmetry arguments, it is shown that the fluorescence kinetics of C-Phycocyanin is expected to be characterized by three exponential kinetic components, independent of the aggregation state. An analytical expression is derived, which allows us to gain a detailed understanding of the origin of the different kinetic components and their associated time-resolved spectra. Numerical calculations of time-resolved spectra are compared with the experimental data