Acclimation of Chlamydomonas reinhardtii to extremely strong light

Photosynthesis Research - Most photosynthetic organisms are sensitive to very high light, although acclimation mechanisms enable them to deal with exposure to strong light up to a point. Here we...     

Anonymous nuclear DNA markers in the American oyster and their implications for the heterozygote deficiency phenomenon in marine bivalves

A puzzling population-genetic phenomenon widely reported in allozyme surveys of marine bivalves is the occurrence of heterozygote deficits relative to Hardy-Weinberg expectations. Possible explanations for this pattern are categorized with respect to whether the effects should be confined to protein-level assays or are genomically pervasive and expected to be registered in both protein- and DNA-level assays. Anonymous nuclear DNA markers from the American oyster were employed to reexamine the phenomenon. In assays based on the polymerase chain reaction (PCR), two DNA-level processes were encountered that can lead to artifactual genotypic scorings: (a) differential amplification of alleles at a target locus and (b) amplification from multiple paralogous loci. We describe symptoms of these complications and prescribe methods that should generally help to ameliorate them. When artifactual scorings at two anonymous DNA loci in the American oyster were corrected, Hardy-Weinberg deviations registered in preliminary population assays decreased to nonsignificant values. Implications of these findings for the heterozygote-deficit phenomenon in marine bivalves, and for the general development and use of PCR-based assays, are discussed.      

The study of telomerase activity in gastric cancer

Telomerase activity was examined in tissue specimens from patients with gastric adenocarcinomas and gastric lymphoma using a modified TRAP (telomeric repeat amplification protocol) assay. Telomerase activity was found in 16 of 18 (89%) patients with gastric adenocarcinomas and gastric lymphoma, whereas it was not detected in a patient with noncancerous gastric mucosa. Almost all analyzed specimens had “high” and “very high” levels of telomerase activity. Telomerase is almost certainly associated with the process of malignant transformation and it can be an important marker for diagnostics of gastric cancer.     

实验动物皮肤病原真菌检测方法的改良

目的对实验动物皮肤病原真菌2种培养方法进行了比较。方法将采集到的3只皮肤真菌感染病兔样品经由沙氏平皿法和沙氏试管斜面培养法分别进行培养。结果在3只真菌感染病兔中应用试管斜面法我们只检测到1例皮肤病原真菌阳性,而采用沙氏平皿法3例阳性全部检出。结论结合临床检测经验,我们认为本研究的沙氏平皿法优于沙氏试管斜面法,在实验动物皮肤病原真菌常规检测中具有推广应用价值。     

Oxygen reduction in chloroplast thylakoids results in production of hydrogen peroxide inside the membrane

Hydrogen peroxide production in isolated pea thylakoids was studied in the presence of cytochrome c to prevent disproportionation of superoxide radicals outside of the thylakoid membranes. The comparison of cytochrome c reduction with accompanying oxygen uptake revealed that hydrogen peroxide was produced within the thylakoid. The proportion of electrons from water oxidation participating in this hydrogen peroxide production increased with increasing light intensity, and at a light intensity of 630 micromol quanta m(-2) s(-1) it reached 60% of all electrons entering the electron transport chain. Neither the presence of a superoxide dismutase inhibitor, potassium cyanide or sodium azide, in the thylakoid suspension, nor unstacking of the thylakoids appreciably affected the partitioning of electrons to hydrogen peroxide production. Also, osmolarity-induced changes in the thylakoid lumen volume, as well as variation of the lumen pH induced by the presence of Gramicidin D, had negligible effects on such partitioning. The flow of electrons participating in lumen hydrogen peroxide production was found to be near 10% of the total electron flow from water. It is concluded that a considerable amount of hydrogen peroxide is generated inside thylakoid membranes, and a possible mechanism, as well as the significance, of this process are discussed.     

Effect of exogenous histidine on restoration of electron transfer on the donor side of Photosystem II depleted of Mn

It is shown that restoration of photoinduced electron flow with added Mn²⁺ (measured by photoreduction of DCPIP and photoinduced change of chlorophyll fluorescence yield) in Mn-depleted Photosystem II (PS II) membrane fragments isolated from spinach chloroplasts, is considerably increased by exogenous histidine (His). The stimulating effect of His is not observed if other electron donors (NH₂OH or diphenylcarbazide) are used instead of Mn²⁺. His added alone does not induce electron transfer in Mn-depleted PS II preparations. Investigation of pH dependence of the stimulating effect of 2 mM His shows that the effect is observed only at pH > 5.0, it gives a 50% activation around pH 6.0 and saturates at pH 7.0–7.5. Nearly 200 μM His is required for a 50 effect at pH 7.0. It is suggested that the added His can be involved in stimulation of electron transfer on the donor side of PS II through direct interaction of Mn²⁺ with deprotonated form(s) of His resulting in formation of Mn–His complexes capable of efficient electron donation to PS II (though it is not excluded that His serves as a base that takes part in proton exchange coupled with redox reactions on the donor side of PS II or as an electron donor to the oxidized Mn).     

Association of 25-Hydroxyvitamin D status and genetic variation in the vitamin D metabolic pathway with FEV1 in the Framingham Heart Study

Background

Vitamin D is associated with lung function in cross-sectional studies, and vitamin D inadequacy is hypothesized to play a role in the pathogenesis of chronic obstructive pulmonary disease. Further data are needed to clarify the relation between vitamin D status, genetic variation in vitamin D metabolic genes, and cross-sectional and longitudinal changes in lung function in healthy adults.

Methods

We estimated the association between serum 25-hydroxyvitamin D [25(OH)D] and cross-sectional forced expiratory volume in the first second (FEV₁) in Framingham Heart Study (FHS) Offspring and Third Generation participants and the association between serum 25(OH)D and longitudinal change in FEV₁ in Third Generation participants using linear mixed-effects models. Using a gene-based approach, we investigated the association between 241 SNPs in 6 select vitamin D metabolic genes in relation to longitudinal change in FEV₁ in Offspring participants and pursued replication of these findings in a meta-analyzed set of 4 independent cohorts.

Results

We found a positive cross-sectional association between 25(OH)D and FEV₁ in FHS Offspring and Third Generation participants (P = 0.004). There was little or no association between 25(OH)D and longitudinal change in FEV₁ in Third Generation participants (P = 0.97). In Offspring participants, the CYP2R1 gene, hypothesized to influence usual serum 25(OH)D status, was associated with longitudinal change in FEV₁ (gene-based P < 0.05). The most significantly associated SNP from CYP2R1 had a consistent direction of association with FEV₁ in the meta-analyzed set of replication cohorts, but the association did not reach statistical significance thresholds (P = 0.09).

Conclusions

Serum 25(OH)D status was associated with cross-sectional FEV₁, but not longitudinal change in FEV₁. The inconsistent associations may be driven by differences in the groups studied. CYP2R1 demonstrated a gene-based association with longitudinal change in FEV₁ and is a promising candidate gene for further studies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-015-0238-y) contains supplementary material, which is available to authorized users.     

Reconstitution of the water-oxidizing complex in manganese-depleted photosystem II preparations using synthetic Mn complexes: a fluorine-19 NMR study of the reconstitution process

Reconstitution of Mn-depleted photosystem II (PSII) particles was examined with synthetic trinuclear Mn complexes of newly developed tripod ligands. Rates of the electron transfer and oxygen evolution were up to 74-86 and 52-56% of those measured in native PSII. These values are higher than those for the PSII reconstituted by MnCl(2). The role of the tripod ligands during the reconstitution process was examined by (19)F NMR. Due to the high NMR sensitivity of the (19)F nucleus and the low abundance of fluorine atoms in natural PSII, it was possible to selectively observe the fluorine atoms on the tripod ligand. It was shown that the tripod ligands were released from the Mn complex after the reconstitution. We propose that the primary step in the reconstitution process is the prebinding of the Mn complex to the hydrophobic part of the PSII particle.