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111.
We sought to determine whether hydrostatic pressure contributed to bradycardia and hypoventilation in hyperbaria. Eight men were studied during exercise at 50, 150, and 250 W while breathing 1) air at 1 bar, 2) helium-oxygen (He-O(2)) at 5.5 bar, 3) sulfur hexafluoride-oxygen (SF(6)-O(2)) at 1.3 bar, and 4) nitrogen-oxygen (N(2)-O(2)) at 5.5 bar. Gas densities were pairwise identical in 1) and 2), and 3) and 4), respectively. Increased hydrostatic pressure to 5.5 bar resulted in a modest but significant relative bradycardia on the order of 6 beats/min, in both the absence [1) vs. 2), P = 0. 0015] and presence [3) vs. 4), P = 0.029] of gases that are both denser than normal and mildly narcotic. In contrast, ventilatory responses appeared not to be influenced by hydrostatic pressure. Also, the combined exposure to increased gas density and mild-to-moderate inert gas narcosis at a given hydrostatic pressure [1) vs. 3), 2) vs. 4)] caused bradycardia (P = 0.032 and 0.061, respectively) of similar magnitude as 5.5-bar hydrostatic pressure. At the same time there was relative hypoventilation at the two higher workloads. We conclude that heart rate control, but not ventilatory control, is sensitive to relatively small increases in hydrostatic pressure. 相似文献
112.
K Tsuchida T Lind H Kitagawa U Lindahl K Sugahara K Lidholt 《European journal of biochemistry》1999,264(2):461-467
beta-N-Acetylgalactosaminyltransferase II and beta-glucuronyltransferase II, involved in chondroitin sulfate biosynthesis, transfer an N-acetylgalactosamine (GalNAc) and glucuronic acid (GlcA) residue, respectively, through beta-linkages to an acceptor chondroitin oligosaccharide derived from the repeating disaccharide region of chondroitin sulfate. They were copurified from fetal bovine serum approximately 2500-fold and 850-fold, respectively, by sequential chromatographies on Red A-agarose, phenyl-Sepharose, S-Sepharose and wheat germ agglutinin-agarose. Identical and inseparable chromatographic profiles of both glycosyltransferase activities obtained through the above chromatographic steps and gel filtration suggest that the purified enzyme activities are tightly coupled, which could imply a single enzyme with dual transferase activities; beta-N-acetylgalactosaminyltransferase and beta-glucuronyltransferase, reminiscent of the heparan sulfate polymerase reaction. However, when a polymerization reaction was performed in vitro with the purified serum enzyme preparation under the polymerization conditions recently developed for the chondroitin-synthesizing system, derived from human melanoma cells, each monosaccharide transfer took place, but no polymerization occurred. These results may suggest that the purified serum enzyme preparation contains both beta-N-acetylgalactosaminyltransferase II and beta-glucuronyltransferase II activities on a single polypeptide or on the respective polypeptides forming an enzyme complex, but is different from that obtained from melanoma cells in that it transfers a single GalNAc or GlcA residue but does not polymerize chondroitin. 相似文献
113.
114.
Water availability drives signatures of local adaptation in whitebark pine (Pinus albicaulis Engelm.) across fine spatial scales of the Lake Tahoe Basin,USA
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Brandon M. Lind Christopher J. Friedline Jill L. Wegrzyn Patricia E. Maloney Detlev R. Vogler David B. Neale Andrew J. Eckert 《Molecular ecology》2017,26(12):3168-3185
Patterns of local adaptation at fine spatial scales are central to understanding how evolution proceeds, and are essential to the effective management of economically and ecologically important forest tree species. Here, we employ single and multilocus analyses of genetic data (n = 116 231 SNPs) to describe signatures of fine‐scale adaptation within eight whitebark pine (Pinus albicaulis Engelm.) populations across the local extent of the environmentally heterogeneous Lake Tahoe Basin, USA. We show that despite highly shared genetic variation (FST = 0.0069), there is strong evidence for adaptation to the rain shadow experienced across the eastern Sierra Nevada. Specifically, we build upon evidence from a common garden study and find that allele frequencies of loci associated with four phenotypes (mean = 236 SNPs), 18 environmental variables (mean = 99 SNPs), and those detected through genetic differentiation (n = 110 SNPs) exhibit significantly higher signals of selection (covariance of allele frequencies) than could be expected to arise, given the data. We also provide evidence that this covariance tracks environmental measures related to soil water availability through subtle allele frequency shifts across populations. Our results replicate empirical support for theoretical expectations of local adaptation for populations exhibiting strong gene flow and high selective pressures and suggest that ongoing adaptation of many P. albicaulis populations within the Lake Tahoe Basin will not be constrained by the lack of genetic variation. Even so, some populations exhibit low levels of heritability for the traits presumed to be related to fitness. These instances could be used to prioritize management to maintain adaptive potential. Overall, we suggest that established practices regarding whitebark pine conservation be maintained, with the additional context of fine‐scale adaptation. 相似文献
115.
Lind MI Persbo F Johansson F 《Proceedings. Biological sciences / The Royal Society》2008,275(1638):1073-1080
The developmental threshold is the minimum size or condition that a developing organism must have reached in order for a life-history transition to occur. Although developmental thresholds have been observed for many organisms, inter-population variation among natural populations has not been examined. Since isolated populations can be subjected to strong divergent selection, population divergence in developmental thresholds can be predicted if environmental conditions favour fast or slow developmental time in different populations. Amphibian metamorphosis is a well-studied life-history transition, and using a common garden approach we compared the development time and the developmental threshold of metamorphosis in four island populations of the common frog Rana temporaria: two populations originating from islands with only temporary breeding pools and two from islands with permanent pools. As predicted, tadpoles from time-constrained temporary pools had a genetically shorter development time than those from permanent pools. Furthermore, the variation in development time among females from temporary pools was low, consistent with the action of selection on rapid development in this environment. However, there were no clear differences in the developmental thresholds between the populations, indicating that the main response to life in a temporary pool is to shorten the development time. 相似文献
116.
Influence of suspended clay on phosphorus uptake by periphyton 总被引:1,自引:0,他引:1
We investigated the effect of suspended clay upon the phosphorus uptake rate exhibited by lotic periphyton communities. Suspended
inorganic clays and periphyton are common to aquatic environments, and both can strongly influence physical and chemical water
conditions. We used replicated artificial stream channels to test the prediction that suspended clay particles would affect
the uptake of soluble reactive phosphorus (SRP) by periphyton. Commercially available kaolinite and bentonite clays were characterized
for their aqueous suspension behavior and affinities for SRP. Periphyton was grown in a recirculating stream system and subjected
to simultaneous suspended clay and SRP additions. SRP removal from solution, both in the presence and absence of suspended
clays, was used to quantify SRP uptake parameters by periphyton. Clay type and concentrations of 20, 80, and 200 mg l−1 had no significant effect upon SRP uptake rate exhibited by periphyton during three 90-min experiments. Less than 1% of SRP
removal was attributable to the suspended clay load or artificial stream construction materials, based on clay isotherm data
and material sorption studies, indicating that 99% of SRP removal was attributable to biotic uptake. Removal of SRP (as KH2PO4) was described by a first-order equation with rate constants ranging between 0.02 and 0.14 min−1. Our results suggest that high turbidity conditions caused by suspended mineral clays have little immediate effect upon SRP
removal from the water column by periphyton.
Handling editor: D. Ryder 相似文献
117.
Efe Sezgin Joanne M. Lind Sadeep Shrestha Sher Hendrickson James J. Goedert Sharyne Donfield Gregory D. Kirk John P. Phair Jennifer L. Troyer Stephen J. O’Brien Michael W. Smith 《Human genetics》2009,125(3):281-294
The host genetic basis of differential outcomes in HIV infection, progression, viral load set point and highly active retroviral
therapy (HAART) responses was examined for the common Y haplogroups in European Americans and African Americans. Accelerated
progression to acquired immune deficiency syndrome (AIDS) and related death in European Americans among Y chromosome haplogroup
I (Y-I) subjects was discovered. Additionally, Y-I haplogroup subjects on HAART took a longer time to HIV-1 viral suppression
and were more likely to fail HAART. Both the accelerated progression and longer time to viral suppression results observed
in haplogroup Y-I were significant after false-discovery-rate corrections. A higher frequency of AIDS-defining illnesses was
also observed in haplogroup Y-I. These effects were independent of the previously identified autosomal AIDS restriction genes.
When the Y-I haplogroup subjects were further subdivided into six I subhaplogroups, no one subhaplogroup accounted for the
effects on HIV progression, viral load or HAART response. Adjustment of the analyses for population stratification found significant
and concordant haplogroup Y-I results. The Y chromosome haplogroup analyses of HIV infection and progression in African Americans
were not significant. Our results suggest that one or more loci on the Y chromosome found on haplogroup Y-I have an effect
on AIDS progression and treatment responses in European Americans.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
118.
Aim
The updated mean HbA1c has been used in risk estimates of diabetic complications, but it does not take into account the temporal relationship between HbA1c and diabetic complications. We studied whether the updated mean HbA1c underestimated the risk of diabetic complications.Method
Continuous HbA1c curves for 10,000 hypothetical diabetes patients were simulated over an average of 7 years. Simulations were based on HbA1c values encountered in clinical practice. We assumed that each short time interval of the continuous HbA1c curves had a long-lasting effect on diabetic complications, as evidenced by earlier studies. We tested several different HbA1c variables including various profiles, e.g. different duration, of such a long-lasting effect. The predictive power of these variables was compared with that of the updated mean HbA1c.Results
The predictive power of the constructed HbA1c variables differed considerably compared to that of the updated mean HbA1c. The risk increase per standard deviation could be almost 100% higher for a constructed predictor than the updated mean HbA1c.Conclusions
The importance of good glycemic control in preventing diabetic complications could have been underestimated in earlier hallmark studies by not taking the time-dependent effect of HbA1c into account. 相似文献119.
Szpryngiel S Ge C Iakovleva I Georgiev A Lind J Wieslander A Mäler L 《Biochemistry》2011,50(21):4451-4466
Membrane lipid glycosyltransferases (GTs) in plants are enzymes that regulate the levels of the non-bilayer prone monogalactosyldiacylglycerol (GalDAG) and the bilayer-forming digalactosyldiacylglycerol (GalGalDAG). The relative amounts of these lipids affect membrane properties such as curvature and lateral stress. During phosphate shortage, phosphate is rescued by replacing phospholipids with GalGalDAG. The glycolsyltransferase enzyme in Arabidopsis thaliana responsible for this, atDGD2, senses the bilayer properties and interacts with the membrane in a monotopic manner. To understand the parameters that govern this interaction, we have identified several possible lipid-interacting sites in the protein and studied these by biophysical techniques. We have developed a multivariate discrimination algorithm that correctly predicts the regions in the protein that interact with lipids, and the interactions were confirmed by a variety of biophysical techniques. We show by bioinformatic methods and circular dichroism (CD), fluorescence, and NMR spectroscopic techniques that two regions are prone to interact with lipids in a surface-charge dependent way. Both of these regions contain Trp residues, but here charge appears to be the dominating feature governing the interaction. The sequence corresponding to residues 227-245 in the protein is seen to be able to adapt its structure according to the surface-charge density of a bilayer. All results indicate that this region interacts specifically with lipid molecules and that a second region in the protein, corresponding to residues 130-148, also interacts with the bilayer. On the basis of this, and sequence charge features in the immediate environment of S227-245, a response model for the interaction of atDGD2 with the membrane bilayer interface is proposed. 相似文献
120.
Pettersen FO Torheim EA Dahm AE Aaberge IS Lind A Holm M Aandahl EM Sandset PM Taskén K Kvale D 《Journal of virology》2011,85(13):6557-6566
Chronic HIV infection is characterized by chronic immune activation and dysfunctional T cells with elevated intracellular cyclic AMP (cAMP), which inhibits the T cell activation capability. cAMP may be induced by prostaglandin E(2) following lipopolysaccharide (LPS)-induced upregulation of cyclooxygenase type 2 (COX-2) in monocytes due to the elevated LPS levels in patients with chronic HIV infection. This hypothesis was tested using celecoxib, a COX-2 inhibitor, for 12 weeks in HIV-infected patients without antiretroviral treatment in a prospective, open, randomized exploratory trial. Thirty-one patients were randomized in the trial; 27 completed the study, including 13 patients on celecoxib. Celecoxib reduced chronic immune activation in terms of CD38 density on CD8(+) T cells (-24%; P = 0.04), IgA levels (P = 0.04), and a combined score for inflammatory markers (P < 0.05). Celecoxib further reduced the inhibitory surface receptor programmed death 1 (PD-1) on CD8(+) T cells (P = 0.01), including PD-1 on the HIV Gag-specific subset (P = 0.02), enhanced the number of CD3(+) CD4(+) CD25(+) CD127(lo/-) Treg or activated cells (P = 0.02), and improved humoral memory recall responses to a T cell-dependent vaccine (P = 0.04). HIV RNA (P = 0.06) and D dimers (P = 0.07) tended to increase in the controls, whereas interleukin-6 (IL-6) possibly decreased in the treatment arm (P = 0.10). In conclusion, celecoxib downmodulated the immune activation related to clinical progression of chronic HIV infection and improved T cell-dependent functions in vivo. 相似文献