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81.
82.
Viral load and CD4 T-cell counts in patients infected with the human immunodeficiency virus (HIV) are commonly used to guide clinical decisions regarding drug therapy or to assess therapeutic outcomes in clinical trials. However, random fluctuations in these markers of infection can obscure clinically significant change. We employ a Monte Carlo simulation to investigate contributing factors in the expected variability in CD4 T-cell count and viral load due solely to the stochastic nature of HIV infection. The simulation includes processes that contribute to the variability in HIV infection including CD4 and CD8 T-cell population dynamics as well as T-cell activation and proliferation. The simulation results may reconcile the wide range of variabilities in viral load observed in clinical studies, by quantifying correlations between viral load measurements taken days or weeks apart. The sensitivity of variability in T-cell count and viral load to changes in the lifetimes of CD4 and CD8 T-cells is investigated, as well as the effects of drug therapy. 相似文献
83.
84.
The epidemiology of acute infections is strongly influenced by the immune status of individuals. In-host models can provide quantitative predictions of immune status and can thus offer valuable insights into the factors that influence transmission between individuals and the effectiveness of vaccination protocols with respect to individual immunity. Here we develop an in-host model of measles infection. The model explicitly considers the effects of immune system memory and CD8 T-cells, which are key to measles clearance. The model is used to determine the effects of waning immunity through vaccination and infection, the effects of booster exposures or vaccines on the level of immunity, and the immune system characteristics that result in measles transmission (R(0)>1) even if an individual has no apparent clinical symptoms. We find that the level of immune system CD8 T-cells at the time of exposure to measles determines whether an individual will experience a measles infection or simply a boost in immunity. We also find that the infected cell dynamics are a good indicator of measles transmission and the degree of symptoms that will be experienced. Our results indicate that the degree of immunity in adults is independent of the source of exposure in early childhood, be it vaccine or natural infection. 相似文献
85.
Kevin S Heffernan Jacob J Sosnoff Christopher A Fahs Kevin K Shinsako Sae Young Jae Bo Fernhall 《Journal of applied physiology》2008,105(1):109-113
With aging and disease, there is a breakdown of the natural fractal-like organization of heart rate (HR). Fractal-like correlation properties of HR can be assessed with detrended fluctuation analysis (DFA). A short-time scaling exponent (alpha(s)) value of 1 is associated with healthy HR dynamics, whereas values that deviate away from 1, in either direction, indicate fractal collapse. The purpose of this study was to examine the effect of resistance exercise training (RT) on fractal correlation properties of HR dynamics. Resting ECG was collected at baseline, following a 4-wk time control period and 6 wk of RT (3 days per wk) in 34 men (23 +/- 1 years of age). Fractal properties of HR were assessed with DFA. There was no change in alpha(s) following either the time control period or RT (1.01 +/- 0.06 to 0.98 +/- 0.06 to 0.93 +/- 0.04, P > 0.05). Given the potential bidirectional nature of fractal collapse, subjects were retrospectively separated into two groups (higher alpha(s) and lower alpha(s)) on the basis of the initial alpha(s) by using cluster analysis. An interaction was detected for alpha(s) following RT (P < 0.05). There was no change in alpha(s) in either group following the time control, but alpha(s) increased following RT in the lower alpha(s) group (n = 18; 0.73 +/- 0.04 to 0.69 +/- 0.04 to 0.88 +/- 0.04) and alpha(s) decreased following RT in the higher alpha(s) group (n = 16; 1.20 +/- 0.04 to 1.24 +/- 0.04 to 0.98 +/- 0.04). In conclusion, RT improves fractal properties of HR dynamics. 相似文献
86.
E Martinez-Jaramillo R Garza-Morales MJ Loera-Arias O Saucedo-Cardenas R Montes-de-Oca-Luna LR McNally 《Biotechnic & histochemistry》2017,92(3):167-174
Fluorescent proteins are useful reporter molecules for a variety of biological systems. We present an alternative strategy for cloning reporter genes that are regulated by the nisin-controlled gene expression (NICE) system. Lactoccocus lactis was genetically engineered to express green fluorescent protein (GFP), mCherry or near-infrared fluorescent protein (iRFP). The reporter gene sequences were optimized to be expressed by L. lactis using inducible promoter pNis within the pNZ8048 vector. Expression of constructions that carry mCherry or GFP was observed by fluorescence microscopy 2 h after induction with nisin. Expression of iRFP was evaluated at 700 nm using an infrared scanner; cultures induced for 6 h showed greater iRFP expression than non-induced cultures or those expressing GFP. We demonstrated that L. lactis can express efficiently GFP, mCherry and iRFP fluorescent proteins using an inducible expression system. These strains will be useful for live cell imaging studies in vitro or for imaging studies in vivo in the case of iRFP. 相似文献
87.
N6‐methyladenine is the most widespread mRNA modification. A subset of human box C/D snoRNA species have target GAC sequences that lead to formation of N6‐methyladenine at a key trans Hoogsteen‐sugar A·G base pair, of which half are methylated in vivo. The GAC target is conserved only in those that are methylated. Methylation prevents binding of the 15.5‐kDa protein and the induced folding of the RNA. Thus, the assembly of the box C/D snoRNP could in principle be regulated by RNA methylation at its critical first stage. Crystallography reveals that N6‐methylation of adenine prevents the formation of trans Hoogsteen‐sugar A·G base pairs, explaining why the box C/D RNA cannot adopt its kinked conformation. More generally, our data indicate that sheared A·G base pairs (but not Watson–Crick base pairs) are more susceptible to disruption by N6mA methylation and are therefore possible regulatory sites. The human signal recognition particle RNA and many related Alu retrotransposon RNA species are also methylated at N6 of an adenine that forms a sheared base pair with guanine and mediates a key tertiary interaction. 相似文献
88.
Alomá Moreno O y MJ Freuler 《Phyton》2015,84(2):466-472
The present study of the Orchidaceae family was carried out in Guamuahaya’s mountain range, from 2000 to March 2013. Fifteen districts were explored after 33 expeditions in the Province of Cienfuegos. Ninety two plant species were identified in the studied area, taking into account the ecological parameters of the mountainous areas of Cienfuegos and Cumanayagua municipalities. 相似文献
89.
Intraspecific DNA sequence variation of the mitochondrial control region of white sturgeon (Acipenser transmontanus) 总被引:3,自引:0,他引:3
Intraspecific sequence variation in the D-loop region of mtDNA in white
sturgeon (Acipenser transmontanus), a relict North American fish species,
was examined in 27 individuals from populations of the Columbia and Fraser
rivers. Thirty-three varied nucleotide positions were present in a
462-nucleotide D-loop sequence, amplified using the polymerase chain
reaction. Bootstrapped neighbor-joining and maximum- parsimony trees of
sequences from 19 haplotypes suggest that the two populations have recently
diverged. This is consistent with the hypothesis that the Columbia River, a
Pleistocene refugium habitat, was the source of founders for the Fraser
River after the last glacial recession. On the basis of a divergence time
of 10-12 thousand years ago, the estimated substitution rate of the white
sturgeon D-loop region is 1.1-1.3 x 10(-7) nucleotides/site/year, which is
comparable to rates for hypervariable sequences in the human D-loop region.
Furthermore, the ratio of mean percent nucleotide differences in the D-
loop (2.27%) to that in whole mtDNA (0.54%, as estimated from
restriction-enzyme data) is 4.3, which is similar to the fourfold-to-
fivefold-higher substitution rate estimated for the human D-loop. The high
nucleotide substitution rate of the hypervariable region indicates that the
vertebrate D-loop has potential as a genetic marker in molecular population
studies.
相似文献
90.
Ancient large-scale genome duplications: phylogenetic and linkage analyses shed light on chordate genome evolution 总被引:12,自引:4,他引:8
Pebusque MJ; Coulier F; Birnbaum D; Pontarotti P 《Molecular biology and evolution》1998,15(9):1145-1159
Paralogous genes from several families were found in four human chromosome
regions (4p16, 5q33-35, 8p12-21, and 10q24-26), suggesting that their
common ancestral region underwent several rounds of large- scale
duplication. Searches in the EMBL databases, followed by phylogenetic
analyses, showed that cognates (orthologs) of human duplicated genes can be
found in other vertebrates, including bony fishes. In contrast, within each
family, only one gene showing the same high degree of similarity with all
the duplicated mammalian genes was found in nonvertebrates (echinoderms,
insects, nematodes). This indicates that large-scale duplications occurred
after the echinoderms/chordates split and before the bony vertebrate
radiation. It has been suggested that two rounds of gene duplication
occurred in the vertebrate lineage after the separation of Amphioxus and
craniate (vertebrates + Myxini) ancestors. Before these duplications, the
genes that have led to the families of paralogous genes in vertebrates must
have been physically linked in the craniate ancestor. Linkage of some of
these genes can be found in the Drosophila melanogaster and Caenorhabditis
elegans genomes, suggesting that they were linked in the triploblast
Metazoa ancestor.
相似文献