Meticillin-resistant Staphylococcus aureus (MRSA) infections have been confirmed in hospitalised Thoroughbred racehorses at the hospitals of two training centres in Japan since 2009. To investigate ...the source of infection, the authors examined the rate of nasal MRSA colonisation in 600 healthy Thoroughbred racehorses, 53 veterinarians and 16 office staff at the racehorse hospitals of the two training centres. MRSA was not isolated from healthy Thoroughbred racehorses or hospital office staff. However, MRSA was isolated from 16 veterinarians (30.1 per cent), and the colonisation rate was significantly higher in veterinarians than in the office staff of the same hospitals. Also, 10 of the 16 MRSA strains (62.5 per cent) isolated from veterinarians were classified as type II by staphylococcal cassette chromosome mec (SCCmec) typing and ST5 by multilocus sequence typing. Pulsed-field gel electrophoresis analysis demonstrated that these 10 MRSA strains of SCCmec type II and ST5 were genetically identical or very similar to 9 MRSA strains isolated from infected horses hospitalised at these hospitals between 2009 and 2013. These results indicate that SCCmec type II and ST5 MRSA strains were probably transmitted between veterinarians and infected horses.
We hypothesized that cyclic electron flow around photosystem I (CEF-PSI) participates in the induction of non-photochemical quenching (NPQ) of chlorophyll (Chl) fiuorescence when the rate of ...photosynthetic linear electron flow (LEF) is electron-acceptor limited. To test this hypothesis, the relationships among photosynthesis rate, electron fluxes through both PSI and PSII Je(PSI) and Je(PSII)l and Chl fluorescence parameters were analyzed simultaneously in intact leaves of tobacco plants at several light intensities and partial pressures of ambient C02 (Ca). At low light intensities, decreasing Ca lowered the photosynthesis rate, but Je(PSI) and Je(PSII) remained constant. Je(PSl) was larger than Je(PSII), indicating the existence of CEF-PSI. Increasing the light intensity enhanced photosynthesis and both Je(PSI) and Je (PSII). Je(PSI)/Je(PSII) also increased at high light and at high light and low Ca combined, showing a strong, positive relationship with NPQ of Chl fluorescence. These results indicated that CEF-PSI contributed to the dissipation of photon energy in excess of that consumed by photosynthesis by driving NPQ of Chl fiuorescence. The main physiological function of CEF-PSI in photosynthesis of higher plants is discussed.
We tested the hypothesis that plants grown under high light intensity (HL-plants) had a large activity of cyclic electron flow around PSI (CEF-PSI) compared with plants grown under low light ...(LL-plants). To evaluate the activity of CEF-PSI, the relationships between photosynthesis rate, quantum yields of both PSII and PSI, and Chl fluorescence parameters were analyzed simultaneously in intact leaves of tobacco plants which had been grown under different light intensities (150 and 1,100 mumol photons m(-2) s(-1), respectively) and with different amounts of nutrients supplied. HL-plants showed a larger value of non-photochemical quenching (NPQ) of Chl fluorescence at the limited activity of photosynthetic linear electron flow. Furthermore, HL-plants had a larger activity of CEF-PSI than LL-plants. These results suggested that HL-plants dissipated the excess photon energy through NPQ by enhancing the ability of CEF-PSI to induce acidification of the thylakoid lumen.
Non-photochemical quenching (NPQ) of Chl fluorescence is a mechanism for dissipating excess photon energy and is dependent on the formation of a DeltapH across the thylakoid membranes. The role of ...cyclic electron flow around photosystem I (PSI) (CEF-PSI) in the formation of this DeltapH was elucidated by studying the relationships between O sub(2)-evolution rate V(O sub(2)), quantum yield of both PSII and PSI Phi(PSII) and Phi(PSI), and Chl fluorescence parameters measured simultaneously in intact leaves of tobacco plants in CO sub (2)-saturated air. Although increases in light intensity raised V(O sub (2)) and the relative electron fluxes through both PSII and PSI Phi(PSII)x PFD and Phi(PSI)x PFD only Phi(PSI)x PFD continued to increase after V(O sub (2)) and Phi(PSII)x PFD became light saturated. These results revealed the activity of an electron transport reaction in PSI not related to photosynthetic linear electron flow (LEF), namely CEF-PSI. NPQ of Chl fluorescence drastically increased after Phi(PSII)x PFD became light saturated and the values of NPQ correlated positively with the relative activity of CEF-PSI. At low temperatures, the light-saturation point of Phi(PSII)x PFD was lower than that of Phi(PSII)x PFD and NPQ was high. On the other hand, at high temperatures, the light-dependence curves of Phi(PSII)x PFD and Phi(PSI)x PFD corresponded completely and NPQ was not induced. These results indicate that limitation of LEF induced CEF-PSI, which, in turn, helped to dissipate excess photon energy by driving NPQ of Chl fluorescence.
We tested the hypothesis that ferredoxin (Fd) limits the activity of cyclic electron flow around PSI (CEF-PSI) in vivo and that the relief of this limitation promotes the non-photochemical quenching ...(NPQ) of Chl fluorescence. In transplastomic tobacco (Nicotiana tabacum cv Xanthi) expressing Fd from Arabidopsis (Arabidopsis thaliana) in its chloroplasts, the minimum yield(Fsub(o)) of Chl fluorescence was higher than in the wild type. Fsub(o) was suppressed to the wild-type level upon illumination with far-red light, implying that the transfer of electrons by Fd-quinone oxidoreductase (FQR) from the chloroplast stroma to plastoquinone was enhanced in transplastomic plants. The activity of CEF-PSI became higher in transplastomic than in wild-type plants under conditions limiting photosynthetic linear electron flow. Similarly, the NPQ of Chl fluorescence was enhanced in transplastomic plants. On the other hand, pool sizes of the pigments of the xanthophyll cycle and the amounts of PsbS protein were the same in all plants. AII these results supported the hypothesis strongly. We conclude that breeding plants with an NPQ of Chl fluorescence increased by an enhancement of CEF-PSI activity might lead to improved tolerance for abiotic stresses, particularly under conditions of low light use efficiency.
We evaluated the H2O2-scavenging activity of the water-water cycle (WWC) in illuminated intact chloroplasts isolated from tobacco leaves. Illumination under conditions that limited photosynthesis red ...light (640 nm), 250 micromol photons/square m/s in the absence of HCO3sup(-) caused chloroplasts to take up O2 and accumulate H2O2. Concomitant with the O2 uptake, both ascorbate peroxidase (APX) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) lost their activities. However, superoxide dismutase (SOD), monodehydroascorbate radical reductase (MDAR), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) activities remained unaffected. The extent to which the photosynthetic linear electron flow decreased was small compared with the decline in APX activity. Therefore, the loss of APX activity lowered the electron flux through the WWC, as evidenced by a decrease in relative electron flux through PSII Phi(PSII)xPFD. To verify these interpretations, we created a transplastomic tobacco line in which an H2O2-insensitive APX from the red alga, Galdieria partita, was overproduced in the chloroplasts. In intact transplastomic chloroplasts which were illuminated under conditions that limited photosynthesis, neither O2 uptake nor H2O2 accumulation occurred. Furthermore, the electron flux through the WWC and the activity of GAPDH were maintained. The present work is the first report of APX inactivation by endogenous H2O2 in intact chloroplasts.
In this paper, we focus on forwarding obstruction attacks in structured overlay networks, and evaluate the impacts of the attacks through computer simulations, and finally propose countermeasures. ...One countermeasure is duplicating the network, and we show the improvement in the successful search rate. Also by examining the network in biased forwarding situations, the existence of nodes handling most of the search queries is verified. Approximately 80% of all search queries reaches a Hub node by the third hop in the search route.
Although H.264/AVC offers major improvements in the coding efficiency and "network friendliness" in terms of flexible mapping to transport layers, it does not offer any security features. ...Authentication schemes to ensure data integrity and sender authentication for H.264/AVC streams are therefore needed. Existing stream authentication schemes carry out authentication at a packet level and thus take away the flexibility of H.264/AVC. We propose SANAL, a stream authentication scheme which carries out authentication procedures at the Network Abstraction Layer (NAL) to make it possible to handle H.264/AVC-specific data without interfering with the H.264/AVC features. We implemented a SANAL prototype and carried out comparative evaluations on playout rate and communication overhead. We show an improvement of about 40% in the playout rate compared to existing schemes.
PDF
