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21.
An in vitro study of the liver 25-hydroxylation of vitamin D2 and the kidney 1- and 24-hydroxylations of 25-hydroxyvitamin D2 was undertaken in order to determine whether the discrimination against vitamin D2 seen in chicks in vivo is the result of a block of one or more of the steps in the activation of the vitamin D2 molecule. Vitamin D2 hydroxylation reactions in the chick are virtually identical with those observed with the vitamin D3 series. It is, therefore, concluded that the chick possesses the required enzymatic machinery to synthesize 1,25-dihydroxyvitamin D2 and that the discrimination must be because of some unknown metabolic reaction of the vitamin D2 compounds, to a defect in the transport of vitamin D2 metabolites, or to target organ discrimination. 相似文献
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Persistence and Expression of the Herpes Simplex Virus Genome in the Absence of Immediate-Early Proteins 总被引:6,自引:13,他引:6 下载免费PDF全文
The immediate-early (IE) proteins of herpes simplex virus (HSV) function on input genomes and affect many aspects of host cell metabolism to ensure the efficient expression and regulation of the remainder of the genome and, subsequently, the production of progeny virions. Due to the many and varied effects of IE proteins on host cell metabolism, their expression is not conducive to normal cell function and viability. This presents a major impediment to the use of HSV as a vector system. In this study, we describe a series of ICP4 mutants that are defective in different subsets of the remaining IE genes. One mutant, d109, does not express any of the IE proteins and carries a green fluorescent protein (GFP) transgene under the control of the human cytomegalovirus IE promoter (HCMVIEp). d109 was nontoxic to Vero and human embryonic lung (HEL) cells at all multiplicities of infection tested and was capable of establishing persistent infections in both of these cell types. Paradoxically, the genetic manipulations that were required to eliminate toxicity and allow the genome to persist in cells for long periods of time also dramatically lowered the level of transgene expression. Efficient expression of the HCMVIEp-GFP transgene in the absence of ICP4 was dependent on the ICP0 protein. In d109-infected cells, the level of transgene expression was very low in most cells but abundant in a small subpopulation of cells. However, expression of the transgene could be induced in cells containing quiescent d109 genomes weeks after the initial infection, demonstrating the functionality of the persisting genomes. 相似文献
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Gentili F Nilsson MC Zackrisson O DeLuca TH Sellstedt A 《Journal of experimental botany》2005,56(422):3121-3127
Cyanobacteria colonizing the feather moss Pleurozium schreberi were isolated from moss samples collected in northern Sweden and subjected to physiological and molecular characterization. Morphological studies of isolated and moss-associated cyanobacteria were carried out by light microscopy. Molecular tools were used for cyanobacteria identification, and a reconstitution experiment of the association between non-associative mosses and cyanobacteria was conducted. The influence of temperature on N2 fixation in the different cyanobacterial isolates and the influence of light and temperature on N2-fixation rates in the moss were studied using the acetylene reduction assay. Two different cyanobacteria were effectively isolated from P. schreberi: Nostoc sp. and Calothrix sp. A third genus, Stigonema sp. was identified by microscopy, but could not be isolated. The Nostoc sp. was found to fix N2 at lower temperatures than Calothrix sp. Nostoc sp. and Stigonema sp. were the predominant cyanobacteria colonizing the moss. The attempt to reconstitute the association between the moss and cyanobacteria was successful. The two isolated genera of cyanobacteria in feather moss samples collected in northern Sweden differ in their temperature optima, which may have important ecological implications. 相似文献
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Background and aims
The feather moss Pleurozium schreberi (Brid.) Mitt. is colonized by cyanobacteria, which fix substantial amounts of atmospheric nitrogen (N) in pristine and N-poor ecosystems. Cyanobacterial N2 fixation is inhibited by N deposition. However, the threshold of N input that leads to the inhibition of N2 fixation has not been adequately investigated. Further, the ability of N2 fixation to recover in mosses from high N deposition areas has not been studied to date.Methods
We conducted two laboratory studies in which we (1) applied a range of concentrations of N as NH4NO3 to mosses from low N-deposition areas, and (2) we deprived mosses from a high N-deposition area of N to test their ability to recover N2 fixation.Results
Higher addition rates (up to 10 kg N ha?1) did not systematically inhibit N2 fixation in P. schreberi. Conversely, upon weeks of N deprivation of mosses from a high N environment, N2 fixation rates increased.Conclusions
The threshold of total N deposition above which N2 fixation in P. schreberi is inhibited is likely to be > 10 kg N ha?1. Further, cyanobacteria are able to recover from high N inputs and are able to fix atmospheric N2 after a period of N deprivation. 相似文献27.
JG Hansen W Gao J Dupuis GT O’Connor W Tang M Kowgier A Sood SA Gharib LJ Palmer M Fornage SR Heckbert BM Psaty SL Booth SUNLIGHT Consortium Patricia A Cassano 《Respiratory research》2015,16(1)
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. 相似文献28.
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Joel Ralston Lydia Lorenc Melissa Montes William V. DeLuca Jeremy J. Kirchman Bradley K. Woodworth Stuart A. Mackenzie Amy Newman Hilary A. Cooke Nikole E. Freeman Alex O. Sutton Lila Tauzer D. Ryan Norris 《Ecology and evolution》2019,9(15):8840-8855
Migratory behaviors such as the timing and duration of migration are genetically inherited and can be under strong natural selection, yet we still know very little about the specific genes or molecular pathways that control these behaviors. Studies in candidate genes Clock and Adcyap1 have revealed that both of these loci can be significantly correlated with migratory behaviors in birds, though observed relationships appear to vary across species. We investigated geographic genetic structure of Clock and Adcyap1 in four populations of blackpoll warblers (Setophaga striata), a Neotropical–Nearctic migrant that exhibits geographic variation in migratory timing and duration across its boreal breeding distribution. Further, we used data on migratory timing and duration, obtained from light‐level geolocator trackers to investigate candidate genotype–phenotype relationships at the individual level. While we found no geographic structure in either candidate gene, we did find evidence that candidate gene lengths are correlated with five of the six migratory traits. Maximum Clock allele length was significantly and negatively associated with spring arrival date. Minimum Adcyap1 allele length was significantly and negatively associated with spring departure date and positively associated with fall arrival date at the wintering grounds. Additionally, we found a significant interaction between Clock and Adcyap1 allele lengths on both spring and fall migratory duration. Adcyap1 heterozygotes also had significantly shorter migration duration in both spring and fall compared to homozygotes. Our results support the growing body of evidence that Clock and Adcyap1 allele lengths are correlated with migratory behaviors in birds. 相似文献
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