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81.
Cheryl A. Kelley Brooke E. Nicholson Claire S. Beaudoin Angela M. Detweiler Brad M. Bebout 《Applied and environmental microbiology》2014,80(23):7316-7323
Methane production has been observed in a number of hypersaline environments, and it is generally thought that this methane is produced through the use of noncompetitive substrates, such as the methylamines, dimethylsulfide and methanol. Stable isotope measurements of the produced methane have also suggested that the methanogens are operating under conditions of substrate limitation. Here, substrate limitation in gypsum-hosted endoevaporite and soft-mat hypersaline environments was investigated by the addition of trimethylamine, a noncompetitive substrate for methanogenesis, and dried microbial mat, a source of natural organic matter. The δ13C values of the methane produced after amendments were compared to those in unamended control vials. At all hypersaline sites investigated, the δ13C values of the methane produced in the amended vials were statistically lower (by 10 to 71‰) than the unamended controls, supporting the hypothesis of substrate limitation at these sites. When substrates were added to the incubation vials, the methanogens within the vials fractionated carbon isotopes to a greater degree, resulting in the production of more 13C-depleted methane. Trimethylamine-amended samples produced lower methane δ13C values than the mat-amended samples. This difference in the δ13C values between the two types of amendments could be due to differences in isotope fractionation associated with the dominant methane production pathway (or substrate used) within the vials, with trimethylamine being the main substrate used in the trimethylamine-amended vials. It is hypothesized that increased natural organic matter in the mat-amended vials would increase fermentation rates, leading to higher H2 concentrations and increased CO2/H2 methanogenesis. 相似文献
82.
Cheryl Dambrot Stefan R. Braam Leon G. J. Tertoolen Matthew Birket Douwe E. Atsma Christine L. Mummery 《Journal of cellular and molecular medicine》2014,18(8):1509-1518
It has been known for over 20 years that foetal calf serum can induce hypertrophy in cultured cardiomyocytes but this is rarely considered when examining cardiomyocytes derived from pluripotent stem cells (PSC). Here, we determined how serum affected cardiomyocytes from human embryonic‐ (hESC) and induced pluripotent stem cells (hiPSC) and hiPSC from patients with hypertrophic cardiomyopathy linked to a mutation in the MYBPC3 gene. We first confirmed previously published hypertrophic effects of serum on cultured neonatal rat cardiomyocytes demonstrated as increased cell surface area and beating frequency. We then found that serum increased the cell surface area of hESC‐ and hiPSC‐derived cardiomyocytes and their spontaneous contraction rate. Phenylephrine, which normally induces cardiac hypertrophy, had no additional effects under serum conditions. Likewise, hiPSC‐derived cardiomyocytes from three MYBPC3 patients which had a greater surface area than controls in the absence of serum as predicted by their genotype, did not show this difference in the presence of serum. Serum can thus alter the phenotype of human PSC derived cardiomyocytes under otherwise defined conditions such that the effects of hypertrophic drugs and gene mutations are underestimated. It is therefore pertinent to examine cardiac phenotypes in culture media without or in low concentrations of serum. 相似文献
83.
Herpes simplex virus 1 (HSV-1) ICP8 is a single-stranded DNA-binding protein that is necessary for viral DNA replication and exhibits recombinase activity in vitro. Alignment of the HSV-1 ICP8 amino acid sequence with ICP8 homologs from other herpesviruses revealed conserved aspartic acid (D) and glutamic acid (E) residues. Amino acid residue D1087 was conserved in every ICP8 homolog analyzed, indicating that it is likely critical for ICP8 function. We took a genetic approach to investigate the functions of the conserved ICP8 D and E residues in HSV-1 replication. The E1086A D1087A mutant form of ICP8 failed to support the replication of an ICP8 mutant virus in a complementation assay. E1086A D1087A mutant ICP8 bound DNA, albeit with reduced affinity, demonstrating that the protein is not globally misfolded. This mutant form of ICP8 was also recognized by a conformation-specific antibody, further indicating that its overall structure was intact. A recombinant virus expressing E1086A D1087A mutant ICP8 was defective in viral replication, viral DNA synthesis, and late gene expression in Vero cells. A class of enzymes called DDE recombinases utilize conserved D and E residues to coordinate divalent metal cations in their active sites. We investigated whether the conserved D and E residues in ICP8 were also required for binding metal cations and found that the E1086A D1087A mutant form of ICP8 exhibited altered divalent metal binding in an in vitro iron-induced cleavage assay. These results identify a novel divalent metal cation-binding site in ICP8 that is required for ICP8 functions during viral replication. 相似文献
84.
Female songbirds use male songs as an important criterion for mate selection. Properties of male songs are thought to indicate the male's quality as a potential mate. Song preferences in female zebra finches are known to be influenced by two factors--early auditory experience and the acoustic characteristics of males' songs. Studies often investigate song preferences by priming females with estrogen. However, estrogenic influences on song preferences have not been studied. We investigated the relative influence of early auditory experience, acoustic features of songs, and estrogen availability on song responsiveness in female zebra finches. Juvenile female zebra finches were tutored for 10 days with 40 songs per day with one of three acoustically different song types--simple songs, long-bout songs or complex songs. A fourth group of females was untutored. Aside from this brief song exposure, females were raised and maintained without exposure to male songs. During adulthood, females' behavioral responses to the three song types were tested under three hormone conditions--untreated, estradiol-treated and 1,4,6-androstatriene-3,17-dione (ATD)-treated (to lower endogenous estrogen). Based on the results of our study, four conclusions can be drawn. First, song responsiveness in female zebra finches is strongly affected by minimal early acoustic experience. Second, inexperienced female zebra finches are inherently biased to respond more to complex songs over other song types Third, although female zebra finches are inherently biased to respond more to complex songs, early acoustic experience may either reinforce or weaken this inherent responsiveness to complex songs. Fourth, estrogen selectively accentuates song responsiveness in acoustically-experienced female zebra finches. 相似文献
85.
Nami Shrestha Palikhe Drew Nahirney Cheryl Laratta Vivek Dipak Gandhi Dilini Vethanayagam Mohit Bhutani Irvin Mayers Lisa Cameron Harissios Vliagoftis 《PloS one》2015,10(12)
Background
Protease-Activated Receptor-2 (PAR-2), a G protein coupled receptor activated by serine proteases, is widely expressed in humans and is involved in inflammation. PAR-2 activation in the airways plays an important role in the development of allergic airway inflammation. PAR-2 expression is known to be upregulated in the epithelium of asthmatic subjects, but its expression on immune and inflammatory cells in patients with asthma has not been studied.Methods
We recruited 12 severe and 24 mild/moderate asthmatics from the University of Alberta Hospital Asthma Clinics and collected baseline demographic information, medication use and parameters of asthma severity. PAR-2 expression on blood inflammatory cells was analyzed by flow cytometry.Results
Subjects with severe asthma had higher PAR-2 expression on CD14++CD16+ monocytes (intermediate monocytes) and also higher percentage of CD14++CD16+PAR-2+ monocytes (intermediate monocytes expressing PAR-2) in blood compared to subjects with mild/moderate asthma. Receiver operating characteristics (ROC) curve analysis showed that the percent of CD14++CD16+PAR-2+ in peripheral blood was able to discriminate between patients with severe and those with mild/moderate asthma with high sensitivity and specificity. In addition, among the whole populations, subjects with a history of asthma exacerbations over the last year had higher percent of CD14++CD16+ PAR-2+ cells in peripheral blood compared to subjects without exacerbations.Conclusions
PAR-2 expression is increased on CD14++CD16+ monocytes in the peripheral blood of subjects with severe asthma and may be a biomarker of asthma severity. Our data suggest that PAR-2 -mediated activation of CD14++CD16+ monocytes may play a role in the pathogenesis of severe asthma. 相似文献86.
DEAD-box proteins participate in various aspects of RNA metabolism in all organisms. These RNA-dependent ATPases are usually regarded as double-stranded RNA unwinding enzymes, though in vitro this activity has only been demonstrated for a subset of them. Given their high biological specificity, their equivocal unwinding activity may reflect the noncognate character of the substrates used in vitro. Here, we pinpoint other reasons for this elusiveness. We have compared the ATPase and helicase activities of three E. coli DEAD-box proteins, CsdA, RhlE and SrmB. Whereas the ATPase activity of all proteins is stimulated (albeit to various degree) by long RNAs, only RhlE is stimulated by short oligoribonucleotides. Consistently, all three proteins can unwind RNA duplexes with long single-stranded extensions, but only RhlE is effective when extensions are short or absent. Another critical constraint concerns the length of the duplex region: in the case of RhlE, the ratio (duplex unwound)/(ATP hydrolyzed) drops 1000-fold upon going from 11 to 14 base pairs, indicating a low processivity. Remarkably, allowing for these constraints, all three proteins can unwind substrates with either 5' or 3' extensions (or no extension in the case of RhlE). This behavior, which contrasts with that of well studied SF1 DNA helicases, is discussed in the light of available structural and biochemical data. 相似文献
87.
Human immunodeficiency virus type 1-hepatitis C virus coinfection: intraindividual comparison of cellular immune responses against two persistent viruses 总被引:7,自引:0,他引:7 下载免费PDF全文
Lauer GM Nguyen TN Day CL Robbins GK Flynn T McGowan K Rosenberg ES Lucas M Klenerman P Chung RT Walker BD 《Journal of virology》2002,76(6):2817-2826
Both human immunodeficiency virus type 1 (HIV-1) and hepatitis C virus (HCV) lead to chronic infection in a high percentage of persons, and an expanding epidemic of HIV-1-HCV coinfection has recently been identified. These individuals provide an opportunity for simultaneous assessment of immune responses to two viral infections associated with chronic plasma viremia. In this study we analyzed the breadth and magnitude of the CD8(+)- and CD4(+)-T-lymphocyte responses in 22 individuals infected with both HIV-1 and HCV. A CD8(+)-T-lymphocyte response against HIV-1 was readily detected in all subjects over a broad range of viral loads. In marked contrast, HCV-specific CD8(+)-T-lymphocyte responses were rarely detected, despite viral loads in plasma that were on average 1,000-fold higher. The few HCV-specific responses that were observed were relatively weak and limited in breadth. CD4-proliferative responses against HIV-1 were detected in about half of the coinfected subjects tested, but no proliferative response against any HCV protein was found in these coinfected persons. These data demonstrate a major discordance in immune responses to two persistent RNA viruses. In addition, they show a consistent and profound impairment in cellular immune responses to HCV compared to HIV-1 in HIV-1-HCV-coinfected persons. 相似文献
88.
The western arctic population of King Eiders (Somateria spectabilis) has declined by >50% in recent years. A health assessment was conducted for adult King Eiders breeding on the north slope of Alaska, USA, to evaluate body condition (n=90, 2002-2006) and baseline biochemical and hematologic values (n=20-30, 2005-2006). Body condition for males and females was excellent. Total protein, calcium, alkaline phosphatase, amylase, and globulin were significantly higher in females than in males, likely because of differences in reproductive physiology. These baseline health data can be used to promote conservation of King Eiders and other closely related species of concern. 相似文献
89.
Danielle Julie Carrier Cheryl A. Bock James E. Cunningham David R. Cyr David I. Dunstan 《In vitro cellular & developmental biology. Plant》1997,33(3):236-239
Summary Interior spruce (Picea glauca engelmannii complex) somatic embryos grown on 48 μmol (±)-ABA per L over a period of 42 d without transfer underwent precocious germination
by 49 d. Those transferred at 28 d to fresh medium with 48 μmol (±)-ABA continued embryo development until harvested at 56
d; the transfer at 28 d resulted in an increase in embryo lipid content after 42 d. Somatic embryos grown under this condition
contained 181.4±41.2, 116.0±42.4, and 91.8±33.6 ng (+)-ABA per mg of lyophilized tissue at 42, 49, and 56 d, respectively.
By comparison, embryos grown without the transfer at 28 d had 86.8±25.4 ng (+)-ABA per mg of lyophilized tissue at 42 d, just
prior to precocious germination. After 3 weeks’ storage in a drying chamber under high humidity, the (+)-ABA content of 56-d-old
transferred embryos decreased to 15.4 ± 4.4 ng (+)-ABA per mg of lyophilized tissue. The increased lipid content resulting
from embryo transfer and the reduction in internal (+)-ABA content during storage are factors which will contribute to improved
conversion of somatic embryos to plantlets. 相似文献