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41.
Adrian Ares Constance A. Harrington Thomas A. Terry Joseph M. Kraft 《Trees - Structure and Function》2008,22(5):603-609
The stable carbon (C) composition of tree rings expressed as δ13C, is a measure of intrinsic water-use efficiency and can indicate the occurrence of past water shortages for tree growth.
We examined δ13C in 3- to 5-year-old rings of Douglas-fir (Pseudotsuga menziesii (Mirb) Franco) trees to elucidate if decreased water supply or uptake was a critical factor in the observed growth reduction
of trees competing with understory herb and shrub vegetation compared to those growing without competition. We hypothesized
that there would be no differences in δ13C of earlywood in trees growing in plots with competing vegetation and those in plots receiving complete vegetation control
during 5 years because earlywood formed early in the growing season when soil water was ample. We also hypothesized that δ13C in latewood which was formed during the later half of the growing season when precipitation was low, would be greater (less
negative) in trees in plots without vegetation control. We then separated early and latewood from rings for three consecutive
years and analyzed their δ13C composition. No significant differences in earlywood δ13C in years 3–5 were observed for trees in the two vegetation control treatments. δ13C of untreated latewood separated from wood cores was greater in 4- and 5-year-old rings of trees growing with competing vegetation
compared to trees growing without vegetation competition (i.e., −25.5 vs. −26.3‰ for year 4, and −26.1 vs. −26.8‰ for year
5). Results suggest that water shortages occurred in Douglas-fir trees on this coastal Washington site in the latewood-forming
portion of the growing season of years 4 and 5 in the no-vegetation control treatment. We also compared δ13C from untreated wood, crude cellulose extracted with the Diglyme–HCl method, and holocellulose extracted with toluene–ethanol
to see if the extraction method would increase the sensitivity of the analysis. δ13C values from the two extraction methods were highly correlated with those from untreated samples (r
2 = 0.97, 0.98, respectively). Therefore, using untreated wood would be as effective as using crude cellulose or holocellulose
to investigate δ13C patterns in young Douglas-fir. 相似文献
42.
Terry Joe Sprinkle F. Arthur McMorris Jun Yoshino George H. De Vries 《Neurochemical research》1985,10(7):919-931
The relative levels of the central nervous system myelin marker enzyme 2:3-cyclic nucleotide 3-phosphodiesterase (EC 3.1.4.37, CNPase) were determined in neuroblastoma, astrocyte, oligodendrocyte and Schwann cell cultures and in freshly isolated human lymphocytes and platelets. The highest specific activities were associated with the cells that elaborate myelin membrane in the central and peripheral nervous system, oligodendrocytes and Schwann cells, respectively. Antiserum to bovine CNPase recognized both CNP1 and CNP2 in CNS myelin and human oligodendroglioma. In addition, a 53,000 dalton protein was evident on autoradiographs of immunoblotted PNS myelin and human oligodendroglioma proteins. Cultured rat oligodendrocyte, C6 and mouse NA neuroblastoma CNPase appear to share common determinants with the corresponding normal rat CNS enzyme. 相似文献
43.
Hilary A. Smith Ashleigh R. Burns Tonya L. Shearer Terry W. Snell 《Journal of experimental marine biology and ecology》2012
Heat shock proteins (HSPs) are important molecules in the stress response of organisms from prokaryotes to mammals, and thus may be useful biomarkers for environmental stress. Here we characterize the functional roles of genes belonging to four distinct families of HSPs (hsp40, hsp60, hsp70, and hsp90) in the monogonont rotifer Brachionus manjavacas. Because B. manjavacas inhabits ponds of varying thermal regimes, including ephemeral ponds that may experience temperature fluctuations, HSP-mediated thermotolerance likely is important to its survival and adaptation. Using interference RNA (RNAi), we provide the first conclusive evidence that HSPs are required for rotifer survival following heat stress. Effective RNAi-mediated suppression of all hsp genes except hsp90 was verified via quantitative PCR. Hsp40, hsp60, and hsp70 are required for rotifer thermotolerance (P < 0.05); however, our data do not indicate hsp90 is essential. Quantitative PCR further revealed immediate up-regulation of hsp40 mRNA following heat stress. Additionally, we demonstrated expression of hsp40 mRNA in multiple tissues using fluorescent in situ hybridization. Our characterization of mRNA expression and functional roles for four distinct hsp genes provides a baseline for molecular-level comparisons of the stress response of rotifers with other taxonomic groups, and the technique for in-depth studies of the role of specific genes in rotifer stress responses. Considering the potential for ambient temperatures to impact species survival, competitive interactions, and body size of individuals, thermotolerance may be an important influence on zooplankton community structure. 相似文献
44.
A. A. Galoyan B. Ya. Gurvits L. A. Shuvalova Michael T. Davis John E. Shively Terry D. Lee 《Neurochemical research》1992,17(8):773-777
A new class of stimulators of basal activity of a number of calmodulin-dependent enzymes have been previously isolated from bovine hypothalamus. One of these stimulators, denoted as C3, has been purified to homogeneity by reverse phase HPLC and tentatively identified as thymosin 4 (1–39) by mass spectrometry and Edman microsequence analysis. The stimulating effect of C3 on rabbit skeletal muscle MLCK basal activity was compared with that of thymosin 1 and thymosin 4 (16–38). Evidence is presented that all the indicated compounds are Ca2+-independent high-affinity MLCK stimulators. The potency of the stimulators in activating the enzyme was: C3>4>(CaM+Ca2+>1.This revised version was published online in June 2005 with corrections to the author name Gurvits. 相似文献
45.
Abstract: One-trial conditioning of the nudibranch mollusk Hermissenda produces short- and long-term changes in excitability (enhancement) of identified sensory neurons. To investigate the biochemical mechanisms underlying this example of plasticity, we have examined changes in protein phosphorylation at different times following the in vitro conditioning trial. Changes in the incorporation of 32 PO4 into proteins were determined using two-dimensional polyacrylamide gel electrophoresis, autoradiography, and densitometry. Conditioning resulted in increases in levels of several phosphoproteins, five of which, ranging in apparent molecular mass from 22 to 55 kDa, were chosen for analysis. The increased phosphorylation of the 46- and 55-kDa phosphoproteins detected 2 h postconditioning was significantly greater than the level of phosphorylation detected in an unpaired control group, indicating that long-term enhancement is pairing specific. Statistically significant increases in phosphorylation as compared with the control group that received only light were detected immediately after conditioning (5 min) for the 55-, 46-, and 22-kDa phosphoproteins, at 1 h for the 55- and 46-kDa phosphoproteins, and at 2 h for the 55-, 46-, and 22-kDa phosphoproteins. The 46- and 55-kDa phosphoproteins are putative structural proteins, and the 22-kDa phosphoprotein is proposed to be a protein kinase C substrate previously identified in Hermissenda following multitrial classical conditioning. Time-dependent increases in protein phosphorylation may contribute to the induction and maintenance of different memory stages expressed in sensory neurons after one-trial conditioning. 相似文献
46.
Terminal Restriction Fragment Length Polymorphism Data Analysis for Quantitative Comparison of Microbial Communities 总被引:12,自引:4,他引:12 下载免费PDF全文
Christopher B. Blackwood Terry Marsh Sang-Hoon Kim Eldor A. Paul 《Applied microbiology》2003,69(2):926-932
Terminal restriction fragment length polymorphism (T-RFLP) is a culture-independent method of obtaining a genetic fingerprint of the composition of a microbial community. Comparisons of the utility of different methods of (i) including peaks, (ii) computing the difference (or distance) between profiles, and (iii) performing statistical analysis were made by using replicated profiles of eubacterial communities. These samples included soil collected from three regions of the United States, soil fractions derived from three agronomic field treatments, soil samples taken from within one meter of each other in an alfalfa field, and replicate laboratory bioreactors. Cluster analysis by Ward's method and by the unweighted-pair group method using arithmetic averages (UPGMA) were compared. Ward's method was more effective at differentiating major groups within sets of profiles; UPGMA had a slightly reduced error rate in clustering of replicate profiles and was more sensitive to outliers. Most replicate profiles were clustered together when relative peak height or Hellinger-transformed peak height was used, in contrast to raw peak height. Redundancy analysis was more effective than cluster analysis at detecting differences between similar samples. Redundancy analysis using Hellinger distance was more sensitive than that using Euclidean distance between relative peak height profiles. Analysis of Jaccard distance between profiles, which considers only the presence or absence of a terminal restriction fragment, was the most sensitive in redundancy analysis, and was equally sensitive in cluster analysis, if all profiles had cumulative peak heights greater than 10,000 fluorescence units. It is concluded that T-RFLP is a sensitive method of differentiating between microbial communities when the optimal statistical method is used for the situation at hand. It is recommended that hypothesis testing be performed by redundancy analysis of Hellinger-transformed data and that exploratory data analysis be performed by cluster analysis using Ward's method to find natural groups or by UPGMA to identify potential outliers. Analyses can also be based on Jaccard distance if all profiles have cumulative peak heights greater than 10,000 fluorescence units. 相似文献
47.
ATP-dependent chromatin-remodeling complexes contribute to the proper temporal and spatial patterns of gene expression in mammalian embryos and therefore play important roles in a number of developmental processes. SWI/SNF-like chromatin-remodeling complexes use one of two different ATPases as their catalytic subunit: brahma (BRM, also known as SMARCA2) and brahma-related gene 1 (BRG1, also known as SMARCA4). We have conditionally deleted a floxed Brg1 allele with a Tie2-Cre transgene, which is expressed in developing hematopoietic and endothelial cells. Brg1(fl/fl):Tie2-Cre(+) embryos die at midgestation from anemia, as mutant primitive erythrocytes fail to transcribe embryonic alpha- and beta-globins, and subsequently undergo apoptosis. Additionally, vascular remodeling of the extraembryonic yolk sac is abnormal in Brg1(fl/fl):Tie2-Cre(+) embryos. Importantly, Brm deficiency does not exacerbate the erythropoietic or vascular abnormalities found in Brg1(fl/fl):Tie2-Cre(+) embryos, implying that Brg1-containing SWI/SNF-like complexes, rather than Brm-containing complexes, play a crucial role in primitive erythropoiesis and in early vascular development. 相似文献
48.
Terry J. Housh Herbert A. deVries Glen O. Johnson Sharon A. Evans Gerald D. Tharp Dona J. Housh Rommie J. Hughes 《European journal of applied physiology and occupational physiology》1990,60(5):391-394
The purpose of this investigation was to determine the effect of glycogen depletion and supercompensation on the physical working capacity at the fatigue threshold (PWCFT). Ten adult males (mean age 23 years, SD 3) volunteered as subjects for this study. During the first laboratory visit the subjects performed a maximal bicycle ergometer test for the determination of maximum oxygen consumption (VO2max). Between 48 and 72 h later, the subjects pedaled to exhaustion at a power output which corresponded to a mean of 76% of VO2max (range, 72-80%) for the purpose of glycogen depletion. For the next 3 days, the subjects were fed a 10.5 MJ.day-1 low carbohydrate diet which consisted of 7.5% carbohydrates, 22.0% protein and 70.5% fat. The subjects then performed an incremental cycle ergometer test to the onset of fatigue or PWCFT, which was estimated from integrated electromyographic voltages of the vastus lateralis muscle. For the next 3 days the subjects were fed a 10.5 MJ high carbohydrate diet which consisted of 72.2% carbohydrates, 12.4% protein and 15.4% fats for the purpose of glycogen supercompensation. The subjects then performed a second PWCFT test. A paired t-test indicated that there was no significant (p greater than 0.05) difference between the means of the PWCFT values (depletion 246 W, SD 30; supercompensation 265 W, SD 28) and they were highly correlated at r = 0.884. The results of this investigation suggested that the methods commonly used to affect glycogen depletion or supercompensation had no effect on PWCFT. 相似文献
49.
Thomas B. Thornley Krishna A. Agarwal Periklis Kyriazis Lingzhi Ma Vaja Chipashvili Jonathan E. Aker Sarantis Korniotis Eva Csizmadia Terry B. Strom Maria Koulmanda 《PloS one》2016,11(3)
The innate immune system critically shapes diabetogenic adaptive immunity during type 1 diabetes (T1D) pathogenesis. While the role of tissue-infiltrating monocyte-derived macrophages in T1D is well established, the role of their tissue-resident counterparts remains undefined. We now demonstrate that islet resident macrophages (IRMs) from non-autoimmune mice have an immunoregulatory phenotype and powerfully induce FoxP3+ Tregs in vitro. The immunoregulatory phenotype and function of IRMs is compromised by TLR4 activation in vitro. Moreover, as T1D approaches in NOD mice, the immunoregulatory phenotype of IRMs is diminished as is their relative abundance compared to immunostimulatory DCs. Our findings suggest that maintenance of IRM abundance and their immunoregulatory phenotype may constitute a novel therapeutic strategy to prevent and/or cure T1D. 相似文献
50.
James S. Wakeley Michael P. Guilfoyle Terry J. Antrobus Richard A. Fischer Wylie C. BarrowJr. Paul B. Hamel 《Wetlands Ecology and Management》2007,15(5):417-439
We used an ordination approach to identify factors important to the organization of breeding bird communities in three floodplains:
Cache River, Arkansas (AR), Iatt Creek, Louisiana (LA), and the Coosawhatchie River, South Carolina (SC), USA. We used 5-min
point counts to sample birds in each study area each spring from 1995 to 1998, and measured ground-surface elevations and
a suite of other habitat variables to investigate bird distributions and community characteristics in relation to important
environmental gradients. In both AR and SC, the average number of Neotropical migrant species detected was lowest in semipermanently
flooded Nyssa aquatica Linnaeus habitats and greatest in the highest elevation floodplain zone. Melanerpes carolinus Linnaeus, Protonotaria citrea Boddaert, Quiscalus quiscula Linnaeus, and other species were more abundant in N. aquatica habitats, whereas Wilsonia citrina Boddaert, Oporornis formosus Wilson, Vireo griseus Boddaert, and others were more abundant in drier floodplain zones. In LA, there were no significant differences in community
metrics or bird species abundances among forest types. Canonical correspondence analyses revealed that structural development
of understory vegetation was the most important factor affecting bird distributions in all three study areas; however, potential
causes of these structural gradients differed. In AR and SC, differences in habitat structure were related to the hydrologic
gradient, as indexed by ground-surface elevation. In LA, structural variations were related mainly to the frequency of canopy
gaps. Thus, bird communities in all three areas appeared to be organized primarily in response to repeated localized disturbance.
Our results suggest that regular disturbance due to flooding plays an important role in structuring breeding bird communities
in floodplains subject to prolonged inundation, whereas other agents of disturbance (e.g., canopy gaps) may be more important
in headwater systems subject to only short-duration flooding. Management for avian community integrity in these systems should
strive to maintain forest zonation and natural disturbance regimes. 相似文献