Photocontrol of anthocyanin formation in turnip seedlings

Summary The substitution of far-red for the first six hours of a prolonged irradiation with red light resulted in a large increase in anthocyanin yield, which was greater than the combined yields from far-red and red when the two treatments were given separately. When intermittent far-red irradiation was followed by a single short exposure to red, a considerable amount of anthocyanin was formed, although each treatment given separately had little effect. Four hours continuous far-red alone yielded some anthocyanin and also resulted in a further large increase in the effect of a short red treatment; this terminal red effect was fully reversible by a subsequent brief exposure to far-red. It is concluded that at least two photochemical reactions are involved in the responses to red and far-red, the first leading to the formation of substrate(s) used in the second reaction.When red light preceded exposure to the far-red/red irradiation sequence, the far-red enhancement effect was almost entirely lost and the anthocyanin yield approached that in red light. The effect of the red pre-irradiation treatment is attributed to destruction of phytochrome and it is suggested that phytochrome is the only pigment mediating anthocyanin synthesis in red and far-red. A possible interpretation is that the high-energy reaction in far-red and the low energy red/far-red reversible reaction are mediated by different forms of phytochrome.The substitution of blue for the first six hours of a prolonged irradiation with red light also resulted in a synergistic increase in anthocyanin yield; the enhancement effect of blue light was, however, not prevented by prior exposure to red. It is concluded that phytochrome is not the only pigment mediating the reactions occurring in blue light. The synergism between blue and red suggests that the high-energy reaction in blue light may lead to the production of substrates for phytochrome action.

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Zusammenfassung Die Substitution der ersten 6 Std einer Hellrot-Dauerbestrahlung durch Dunkelrot führte zu einem starken Anstieg im Anthocyangehalt, der höher war als die Summe aus Dunkelrot und Hellrot, wenn beide Bestrahlungen getrennt gegeben wurden. Folgte auf intermittierende Dunkelrot-Bestrahlung eine einmalige Dosis Hellrot, bildete sich eine beträchtliche Menge Anthocyan, obwohl jede Bestrahlung für sich kaum wirksam war. 4 Std Dauerdunkelrot induzierten bereits meßbare Anthocyanbildung, die durch kurze Hellrot-Bestrahlung weiter gesteigert werden konnte; der Effekt dieser terminalen Dosis Hellrot konnte durch nachfolgende kurze Dunkelrot-Bestrahlung wieder rückgängig gemacht werden. Daraus wird geschlossen, daß wenigstens zwei photochemische Reaktionen bei Bestrahlung mit Hellrot und Dunkelrot ablaufen, wobei die erste Substrat(e) für die zweite produziert.Wurde vor einer Dunkelrot-Hellrot-Sequenz mit Hellrot bestrahlt, ging die fördernde Wirkung von Dunkelrot fast vollständig verloren und der Anthocyangehalt entsprach annähernd dem in Hellrot. Der Effekt der Hellrot-Vorbestrahlung wird auf die Destruktion von Phytochrom zurückgeführt und es wird vermutet, daß Phytochrom das einzige Pigment ist, das bei der Anthocyansynthese in Hellrot und Dunkelrot beteiligt ist. Eine mögliche Interpretation wäre, daß die Hochenergiereaktion in Dunkelrot und die Hellrot-Dunkelrot reversible Niederenergiereaktion durch verschiedene Formen von Phytochrom vermittelt werden.Die Substitution der ersten 6 Std einer Dauerbelichtung mit Hellrot durch Blau ergab ebenfalls eine synergistische Zunahme im Anthocyangehalt. Der fördernde Effekt von Blaulicht konnte jedoch durch Vorbestrahlung mit Hellrot nicht verhindert werden. Daraus wird geschlossen, daß Phytochrom nicht das einzige Pigment sein kann, das die Reaktionen in Blaulicht vermittelt. Der Synergismus zwischen Blau und Hellrot läßt vermuten, daß die Hochenergiereaktion in Blau zur Produktion von Substrat führt, mit dem Phytochrom reagieren kann.

     

Cooperative Binding of Annexin A2 to Cholesterol- and Phosphatidylinositol-4,5-Bisphosphate-Containing Bilayers

Biological membranes are organized into dynamic microdomains that serve as sites for signal transduction and membrane trafficking. The formation and expansion of these microdomains are driven by intrinsic properties of membrane lipids and integral as well as membrane-associated proteins. Annexin A2 (AnxA2) is a peripherally associated membrane protein that can support microdomain formation in a Ca²⁺-dependent manner and has been implicated in membrane transport processes. Here, we performed a quantitative analysis of the binding of AnxA2 to solid supported membranes containing the annexin binding lipids phosphatidylinositol-4,5-bisphosphate and phosphatidylserine in different compositions. We show that the binding is of high specificity and affinity with dissociation constants ranging between 22.1 and 32.2 nM. We also analyzed binding parameters of a heterotetrameric complex of AnxA2 with its S100A10 protein ligand and show that this complex has a higher affinity for the same membranes with K_d values of 12 to 16.4 nM. Interestingly, binding of the monomeric AnxA2 and the AnxA2-S100A10 complex are characterized by positive cooperativity. This cooperative binding is mediated by the conserved C-terminal annexin core domain of the protein and requires the presence of cholesterol. Together our results reveal for the first time, to our knowledge, that AnxA2 and its derivatives bind cooperatively to membranes containing cholesterol, phosphatidylserine, and/or phosphatidylinositol-4,5-bisphosphate, thus providing a mechanistic model for the lipid clustering activity of AnxA2.     

Mode of action of phosphonoformate as an anti-herpes simplex virus agent

Phosphonoformate inhibited the replication of Herpes simplex virus (HSV) type 1 and type 2 in culture. The concentration required to inhibit the replication of both types of virus by 2 logs at 28 h post-infection was approximately 150 microM. It was more potent than phosphonoacetate against the growth of both virus types. A virus mutant which is resistant to phosphonoacetate was cross-resistant to phosphonoformate. Arsonoacetate, at 300 microM, had no antivirus activity. Phosphonoformate also inhibited HeLa and KB cell growth; at a concentration of about 500 microM, cell growth was inhibited by 50%. The anti-cell growth effects of the drug were completely reversible. The antivirus effect of phosphonoformate was partially reversible, depending on the time and duration of exposure of infected cultures to the drug. To obtain the maximum antivirus effect, phosphonoformate had to be added within the first 3 h post-virus-infection and be continuously present for at least 18 h. Phosphonoformate, added at 0 h post-infection, suppressed the induction of virus-specific DNA polymerase and DNAase activities. dTMP incorporation into DNA was preferentially inhibited in nuclei isolated from infected cells compared to uninfected cells, and the degree of inhibition varied with the ionic strength of the assay. Phosphonoformate was a potent inhibitor of the purified HSV-1 and HSV-2 DNA polymerases, inhibiting DNA polymerase activity by 50% at a concentration of 3 microM and ionic strength of 0.2.     

A computational framework for modeling cell–matrix interactions in soft biological tissues

Biomechanics and Modeling in Mechanobiology - Living soft tissues appear to promote the development and maintenance of a preferred mechanical state within a defined tolerance around a so-called set...     

Synopsis of the CASIROZ case study: carbon sink strength of Fagus sylvatica L. in a changing environment--experimental risk assessment of mitigation by chronic ozone impact

Databases are needed for the ozone (O(3)) risk assessment on adult forest trees under stand conditions, as mostly juvenile trees have been studied in chamber experiments. A synopsis is presented here from an integrated case study which was conducted on adult FAGUS SYLVATICA trees at a Central-European forest site. Employed was a novel free-air canopy O(3) fumigation methodology which ensured a whole-plant assessment of O(3) sensitivity of the about 30 m tall and 60 years old trees, comparing responses to an experimental 2 x ambient O(3) regime (2 x O(3), max. 150 nl O(3) l (-1)) with those to the unchanged 1 x ambient O(3) regime (1 x O(3)=control) prevailing at the site. Additional experimentation on individual branches and juvenile beech trees exposed within the forest canopy allowed for evaluating the representativeness of young-tree and branch-bag approaches relative to the O(3) sensitivity of the adult trees. The 2 x O(3) regime did not substantially weaken the carbon sink strength of the adult beech trees, given the absence of a statistically significant decline in annual stem growth; a 3 % reduction across five years was demonstrated, however, through modelling upon parameterization with the elaborated database. 2 x O(3) did induce a number of statistically significant tree responses at the cell and leaf level, although the O(3) responsiveness varied between years. Shade leaves displayed an O(3) sensitivity similar to that of sun leaves, while indirect belowground O(3) effects, apparently mediated through hormonal relationships, were reflected by stimulated fine-root and ectomycorrhizal development. Juvenile trees were not reliable surrogates of adult ones in view of O(3) risk assessment. Branch sections enclosed in (climatized) cuvettes, however, turned out to represent the O(3) sensitivity of entire tree crowns. Drought-induced stomatal closure decoupled O(3) intake from O(3) exposure, as in addition, also the "physiologically effective O(3) dose" was subject to change. No evidence emerged for a need to lower the "Critical Level for Ozone" in risk assessment of forest trees, although sensitive tree parameters did not necessarily reflect a linear relationship to O(3) stress. Exposure-based concepts tended to overestimate O(3) risk under drought, which is in support of current efforts to establish flux-related concepts of O(3) intake in risk assessment.     

Cholesterol as a Risk Factor for Subarachnoid Hemorrhage: A Systematic Review

BackgroundThe role played by total cholesterol (TC) in risk for subarachnoid hemorrhage (SAH) is unclear because studies report both high and low TC each as a risk factor. We performed a systematic review to clarify associations between lipid profile and SAH.MethodsOur literature search comprised Pubmed, Scopus, and Cochrane Library databases with no language, publication year, or study type limitations. The Preferred Reporting Items for Systematic reviews and Meta-analyses (PRISMA) checklist guided our reporting. Data forms adapted from the Critical Appraisal Skills Program (CASP), and Cochrane Collaboration guidelines provided a platform for risk-of-bias evaluation. We used a random effects model to calculate pooled estimates and assessed heterogeneity with I²-statistics.ResultsOf the final 21 studies reviewed, 12 were prospective and 9 retrospective. All studies assessed TC, four assessed HDL, and none LDL in risk for SAH. Heterogeneity among all, retrospective, and Asian studies was high (I² = 79.5%, I² = 89.0%, and I² = 84.3%) and considerable in prospective (I² = 46.0%). We therefore focused on qualitative analysis and found that only two studies had a low risk of bias. According to these studies high TC increases risk for SAH in men, whereas the role of HDL remained unclear.ConclusionThe low-risk-of-bias studies suggest that elevated TC levels elevate risk for SAH in men. Due to the high prevalence of hypercholesterolemia, population attributable risk (PAR) of hypercholesterolemia may exceed the PARs of smoking and hypertension in men. Apart from diabetes and obesity, the risk-factor profile of SAH seems to resemble that of other cerebrovascular diseases, at least in men.     

Association of Epstein-Barr virus early antigen diffuse component and virus-specified DNA polymerase activity.

The role of Epstein-Barr virus (EBV) early antigen diffuse component (EA-D) and its relationship with EBV DNA polymerase in EBV genome-carrying cells are unclear, EBV-specified DNA polymerase was purified in a sequential manner from Raji cells treated with phorbol-12,13-dibutyrate and n-butyrate by phosphocellulose, DEAE-cellulose, double-stranded DNA-cellulose, and blue Sepharose column chromatography. Four polypeptides with molecular masses of 110,000, 100,000, 55,000, and 49,000 daltons were found to be associated with EBV-specified DNA polymerase activity. A monoclonal antibody which could neutralize the EBV DNA polymerase activity was prepared and found to recognize 55,000- and 49,000-dalton polypeptides. An EA-D monoclonal antibody, R3 (G. R. Pearson, V. Vorman, B. Chase, T. Sculley, M. Hummel, and E. Kieff, J. Virol. 47:183-201, 1983), was also able to recognize these same two polypeptides associated with EBV DNA polymerase activity. It was concluded that EBV EA-D polypeptides, as identified by R3 monoclonal antibody, are critical components of EBV DNA polymerase.