Prevalence of Chlamydophila psittaci in Fecal Droppings from Feral Pigeons in Amsterdam, The Netherlands

In many cities, the feral rock dove is an abundant bird species that can harbor Chlamydophila psittaci. We determined the prevalence and genotype of C. psittaci in fresh fecal samples from feral pigeons in Amsterdam, The Netherlands. The prevalence was 7.9% overall (26/331; 95% confidence interval, 5 to 11). Ten genotyped PCR-positive samples were all genotype B.     

High misses after odd flashes in oxygen evolution in thoroughly dark-adapted thylakoids from pea and Chenopodium album

In Photosystem II (PS II), water is oxidized to molecular oxygen and plastoquinone is reduced to plastoquinol. The oxidation of water requires the accumulation of four oxidizing equivalents, through the so-called S-states of the oxygen evolving complex; the production of plastoquinol requires the accumulation of two reducing equivalents on a bound plastoquinone, Q_B. It has been generally believed that during the flash-induced transition of each of the S-states (S_n S_n+1, where n=0, 1, 2 and 3), a certain small but equal fraction of the PS II reaction centers are unable to function and, thus, miss being turned over. We used thoroughly dark-adapted thylakoids from peas (Pisum sativum) and Chenopodium album (susceptible and resistant to atrazine) starting with 100% of the oxygen evolving complex in the S₁ state. Thylakoids were illuminated with saturating flashes, providing a double hit parameter of about 0.07. Our experimental data on flashnumber dependent oscillations in the amount of oxygen per flash fit very well with a binary pattern of misses: 0, 0.2, 0, 0.4 during S₀ S₁, S₁ S₂, S₂ S₃ and S₃ S₀ transitions. Addition of 2 mM ferricyanide appears to shift this pattern by one flash. These results are consistent with the bicycle model recently proposed by V. P. Shinkarev and C. A. Wraight (Oxygen evolution in photosynthesis: From unicycle to bicycle, 1993, Proc Natl Acad Sci USA 90: 1834–1838), where misses are due to the presence of P⁺ or Q_A ^- among the various equilibrium states of PS II centers.Abbreviations miss parameter - double hit parameter - PS II Photosystem II - Q_A primary one-electron acceptor of PS II, a plastoquinone molecule - Q_B secondary plastoquinone two-electron acceptor of PS II - S-states (S_n, where n=0, 1, 2, 3 or 4) redox states of the oxygen evolving complex     

Influence of photoinhibition on electron transport and photophosphorylation of isolated chloroplasts

The effects of a photoinhibition treatment (PIT) on electron transport and photophosphorylation reactions were measured in chloroplasts isolated from triazine-resistant and susceptible Chenopodium album plants grown under high and low irradiance. Electron transport dependent on photosystem I (PSI) alone was much less affected by PIT than that dependent on both photosystem II (PSII) and PSI. There was a smaller difference in susceptibility to PIT between the photophosphorylation activitity dependent on PSI alone and that dependent on both PSII and PSI. Because in all cases photophosphorylation activity decreased faster upon PIT than the rate of electron transport, we conclude that photoinhibition causes a gradual uncoupling of electron transport with phosphorylation. Since the extent of the light-induced proton gradient across the thylakoid membrane decreased upon PIT, it is suggested that photoinhibiton causes a proton leakiness of the membrane. We have found no significant differences to PIT of the various reactions measured in chloroplasts isolated from triazine-resistant and susceptible plants. We have also not observed any significant differences to PIT of the photophosphorylation reactions in chloroplasts of plants grown under low irradiance, compared with those grown under high irradiance. However, the electron transport reactions in chloroplasts from plants grown under low irradiance appeared to be somewhat less sensitive to PIT than those grown under high irradiance.     

The interaction between bicarbonate and the herbicide ioxynil in the thylakoid membrane and the effects of amino acid modification on bicarbonate action

Bicarbonate depletion of chloroplast thylakoids reduces the affinity of the herbicide, ioxynil, to its binding site in Photosystem (PS) II. This herbicide is found to be a relatively more efficient inhibitor of the Hill reaction when HCO^?₃ is added to CO₂-depleted thylakoids in subsaturating rather than in saturating concentrations. The reason for this dependence of the inhibitor efficiency on the HCO^?₃ concentration is that the inactive HCO^?₃-deficient PS II reaction chains bind less ioxynil than the active PS II electron-transport chains that have bound HCO^?₃, and, thus, after addition of a certain amount of ioxynil the concentration of the free herbicide increases when the HCO^?₃ concentration decreases. Therefore, the inhibition of electron transport by ioxynil increases at decreasing HCO^?₃ levels. Measurements on the effects of modification of lysine and arginine residues on the rate of electron transport are also presented: the rate of modification is faster in the presence than in the absence of HCO^?₃. Therefore, we suggest that surface-exposed lysine or arginine residues are not involved in binding of HCO^?₃ (or CO₂ or CO^2?₃) to its binding protein, but that HCO^?₃ influences the conformation of its binding environment such that the affinity for certain herbicides and the accessibility for amino acid modifiers are changed.     

Multiple functions of photosystem II

The most important function of photosystem II (PSII) is its action as a water-plastoquinone oxido-reductase. At the expense of light energy, water is split, and oxygen and plastoquinol are formed. In addition to this most important activity, PSII has additional functions, especially in the regulation of (light) energy distribution. The downregulation of PSII during photoinhibition is a protection measure. PSII is an anthropogenic target for many herbicides. There is a unique action of bicarbonate on PSII. Decrease in the activity of PSII is the first effect in a plant under stress; this decreased activity can be most easily measured with fluorescence. PSII is a sensor for stress, and induces regulatory processes with different time scales: photochemical quenching, formation of a proton gradient, state transitions, downregulation by photoinhibition and gene expression.     

Apolipoprotein C-III deficiency accelerates triglyceride hydrolysis by lipoprotein lipase in wild-type and apoE knockout mice

Previous studies with hypertriglyceridemic APOC3 transgenic mice have suggested that apolipoprotein C-III (apoC-III) may inhibit either the apoE-mediated hepatic uptake of TG-rich lipoproteins and/or the lipoprotein lipase (LPL)-mediated hydrolysis of TG. Accordingly, apoC3 knockout (apoC3(-/-)) mice are hypotriglyceridemic. In the present study, we attempted to elucidate the mechanism(s) underlying these phenomena by intercrossing apoC3(-/-) mice with apoE(-/-) mice to study the effects of apoC-III deficiency against a hyperlipidemic background. Similar to apoE(+/+) apoC3(-/-) mice, apoE(-/-)apoC3(-/-) mice exhibited a marked reduction in VLDL cholesterol and TG, indicating that the mechanism(s) by which apoC-III deficiency exerts its lipid-lowering effect act independent of apoE. On both backgrounds, apoC3(-/-) mice showed normal intestinal lipid absorption and hepatic VLDL TG secretion. However, turnover studies showed that TG-labeled emulsion particles were cleared much more rapidly in apoC3(-/-) mice, whereas the clearance of VLDL apoB, as a marker for whole particle uptake by the liver, was not affected. Furthermore, it was shown that cholesteryl oleate-labeled particles were also cleared faster in apoC3(-/-) mice. Thus the mechanisms underlying the hypolipidemia in apoC3(-/-) mice involve both a more efficient hydrolysis of VLDL TG as well as an enhanced selective clearance of VLDL cholesteryl esters from plasma. In summary, our studies of apoC3(-/-) mice support the concept that apoC-III is an effective inhibitor of VLDL TG hydrolysis and reveal a potential regulating role for apoC-III with respect to the selective uptake of cholesteryl esters.     

Influence of Inter-Training Intervals on Intermanual Transfer Effects in Upper-Limb Prosthesis Training: A Randomized Pre-Posttest Study

Improvement in prosthetic training using intermanual transfer (the transfer of motor skills from the trained, “unaffected” hand to the untrained, “affected” hand) has been shown in previous studies. The aim of this study is to determine the influence of the inter-training interval on the magnitude of the intermanual transfer effects. This was done using a mechanistic, randomized, single-blinded pretest-posttest design. Sixty-four able-bodied, right-handed participants were randomly assigned to the Short and Long Interval Training Groups and the Short and Long Interval Control Groups. The Short and Long Interval Training Groups used a prosthesis simulator in their training program. The Short and Long Interval Control Groups executed a sham training program, that is, a dummy training program in which the same muscles were trained as with the prosthesis simulator. The Short Interval Training Group and the Short Interval Control Groups trained on consecutive days, while the Long Interval Training Group and Long Interval Control Group trained twice a week. To determine the improvement in skills, a test was administered before, immediately after, and at two points in time after the training. Training was performed with the “unaffected” arm; tests were performed with the “affected” arm. The outcome measurements were: the movement time (the time from the beginning of the movement until completion of the task); the duration of maximum hand opening, (the opening of the prosthetic hand while grasping an object); and the grip-force control (the error from the required grip-force during a tracking task). Intermanual transfer was found in movement times, but not in hand opening or grip-force control. The length of the inter-training interval did not affect the magnitude of intermanual transfer effects. No difference in the intermanual transfer effect in upper-limb prosthesis training was found for training on a daily basis as compared to training twice a week.

Trial Registration

Nederlands Trial Register NTR3888     

Evidence for complete epistasis of null mutations in murine Fanconi anemia genes Fanca and Fancg

Fanconi anemia (FA) is a heritable disease characterized by bone marrow failure, congenital abnormalities, and cancer predisposition. The 15 identified FA genes operate in a molecular pathway to preserve genomic integrity. Within this pathway the FA core complex operates as an ubiquitin ligase that activates the complex of FANCD2 and FANCI to coordinate DNA repair. The FA core complex is formed by at least 12 proteins. However, only the FANCL subunit displays ubiquitin ligase activity. FANCA and FANCG are members of the FA core complex for which no other functions have been described than to participate in protein interactions. In this study we generated mice with combined null alleles for Fanca and Fancg to identify extended functions for these genes by characterizing the double mutant mice and cells.Double mutant a^−/−/g^−/− mice were born at near Mendelian frequencies without apparent developmental abnormalities. Histological analysis of a^−/−/g^−/− mice revealed a Leydig cell hyperplasia and frequent vacuolization of Sertoli cells in testes, while ovaries were depleted from developing follicles and displayed an interstitial cell hyperplasia. These gonadal aberrations were associated with a compromised fertility of a^−/−/g^−/− males and females. During the first year of life a^−/−/g^−/− did not develop malignancies or bone marrow failure. At the cellular level a^−/−/g^−/−, Fanca^−/−, and Fancg^−/− cells proved equally compromised in DNA crosslink and homology-directed repair. Overall the phenotype of a^−/−/g^−/− double knockout mice and cells appeared highly similar to the phenotype of Fanca or Fancg single knockouts. The lack of an augmented phenotype suggest that null mutations in Fanca or Fancg are fully epistatic, making additional important functions outside of the FA core complex highly unlikely.