共查询到20条相似文献,搜索用时 15 毫秒
1.
Background
The ability of a bacterial strain to competitively exclude or displace other strains can be attributed to the production of narrow spectrum antimicrobials, the bacteriocins. In an attempt to evaluate the importance of bacteriocin production for Escherichia coli strain residence in the gastrointestinal tract, a murine model experimental evolution study was undertaken. 相似文献2.
Background
The lactase enzyme allows lactose digestion in fresh milk. Its activity strongly decreases after the weaning phase in most humans, but persists at a high frequency in Europe and some nomadic populations. Two hypotheses are usually proposed to explain the particular distribution of the lactase persistence phenotype. The gene-culture coevolution hypothesis supposes a nutritional advantage of lactose digestion in pastoral populations. The calcium assimilation hypothesis suggests that carriers of the lactase persistence allele(s) (LCT*P) are favoured in high-latitude regions, where sunshine is insufficient to allow accurate vitamin-D synthesis. In this work, we test the validity of these two hypotheses on a large worldwide dataset of lactase persistence frequencies by using several complementary approaches.Methodology
We first analyse the distribution of lactase persistence in various continents in relation to geographic variation, pastoralism levels, and the genetic patterns observed for other independent polymorphisms. Then we use computer simulations and a large database of archaeological dates for the introduction of domestication to explore the evolution of these frequencies in Europe according to different demographic scenarios and selection intensities.Conclusions
Our results show that gene-culture coevolution is a likely hypothesis in Africa as high LCT*P frequencies are preferentially found in pastoral populations. In Europe, we show that population history played an important role in the diffusion of lactase persistence over the continent. Moreover, selection pressure on lactase persistence has been very high in the North-western part of the continent, by contrast to the South-eastern part where genetic drift alone can explain the observed frequencies. This selection pressure increasing with latitude is highly compatible with the calcium assimilation hypothesis while the gene-culture coevolution hypothesis cannot be ruled out if a positively selected lactase gene was carried at the front of the expansion wave during the Neolithic transition in Europe. 相似文献3.
Angela Maria Cusano Ermenegilda Parrilli Gennaro Marino Maria Luisa Tutino 《Microbial cell factories》2006,5(1):40-8
Background
The final aim of recombinant protein production is both to have a high specific production rate and a high product quality. It was already shown that using cold-adapted bacteria as host vectors, some "intractable" proteins can be efficiently produced at temperature as low as 4°C. 相似文献4.
Amr A Saad Darren M Ashcroft Kath D Watson Kimme L Hyrich Peter R Noyce Deborah PM Symmons the British Society for Rheumatology Biologics Register 《Arthritis research & therapy》2009,11(2):R52
Introduction
Anti-TNF therapies represent a breakthrough in the treatment of severe psoriatic arthritis. However, little is known about long-term drug persistence with these treatments in patients with psoriatic arthritis in routine clinical practice. The aim of this study was to assess persistence with first-course and second-course treatment with anti-TNF agents in a prospective cohort of psoriatic arthritis patients and to identify factors associated with and reasons for drug discontinuation. 相似文献5.
Dalibor Antolovic Moritz Koch Inga Bohlmann Peter Kienle Markus Büchler Jürgen Weitz 《BMC biotechnology》2005,5(1):1
Background
Recombinant adenoviral vectors are highly efficient for in vitro and in vivo gene delivery. They can easily be produced in large numbers, transduce a wide variety of cell types and generate high levels of transgene expression. 相似文献6.
Jorge L. Salinas Jorge L. Alave Andrew O. Westfall Jorge Paz Fiorella Moran Danny Carbajal-Gonzalez David Callacondo Odalie Avalos Martin Rodriguez Eduardo Gotuzzo Juan Echevarria James H. Willig 《PloS one》2013,8(10)
Objectives
In developing nations, the use of operational parameters (OPs) in the prediction of clinical care represents a missed opportunity to enhance the care process. We modeled the impact of multiple measurements of antiretroviral treatment (ART) adherence on antiretroviral treatment outcomes in Peru.Design And Methods
Retrospective cohort study including ART naïve, non-pregnant, adults initiating therapy at Hospital Nacional Cayetano Heredia, Lima-Peru (2006-2010). Three OPs were defined: 1) Medication possession ratio (MPR): days with antiretrovirals dispensed/days on first-line therapy; 2) Laboratory monitory constancy (LMC): proportion of 6 months intervals with ≥1 viral load or CD4 reported; 3) Clinic visit constancy (CVC): proportion of 6 months intervals with ≥1 clinic visit.Three multi-variable Cox proportional hazard (PH) models (one per OP) were fit for (1) time of first-line ART persistence and (2) time to second-line virologic failure. All models were adjusted for socio-demographic, clinical and laboratory variables.Results
856 patients were included in first-line persistence analyses, median age was 35.6 years [29.4-42.9] and most were male (624; 73%). In multivariable PH models, MPR (per 10% increase HR=0.66; 95%CI=0.61-0.71) and LMC (per 10% increase 0.83; 0.71-0.96) were associated with prolonged time on first-line therapies.Among 79 individuals included in time to second-line virologic failure analyses, MPR was the only OP independently associated with prolonged time to second-line virologic failure (per 10% increase 0.88; 0.77-0.99).Conclusions
The capture and utilization of program level parameters such as MPR can provide valuable insight into patient-level treatment outcomes. 相似文献7.
Isao Oishi Sungtae Kim Kyoko Yoshii Concepcion Rodriguez Esteban Juan Carlos Izpisua Belmonte 《BMC biotechnology》2011,11(1):5
Background
A promoter capable of driving high-level transgene expression in oviduct cells is important for developing transgenic chickens capable of producing therapeutic proteins, including monoclonal antibodies (mAbs), in the whites of laid eggs. Ovalbumin promoters can be used as oviduct-specific regulatory sequences in transgenic chickens, but their promoter activities are not high, according to previous reports. 相似文献8.
Manuel Manchado Carlos Infante Esther Asensio Jose Pedro Ca?avate Susan E Douglas 《BMC evolutionary biology》2007,7(1):107
Background
Ribosomal proteins (RPs) are key components of ribosomes, the cellular organelle responsible for protein biosynthesis in cells. Their levels can vary as a function of organism growth and development; however, some RPs have been associated with other cellular processes or extraribosomal functions. Their high representation in cDNA libraries has resulted in the increase of RP sequences available from different organisms and their proposal as appropriate molecular markers for phylogenetic analysis. 相似文献9.
Anna-Karin Roos Fredrik Eriksson James A. Timmons Josefine Gerhardt Ulrika Nyman Lindvi Gudmundsdotter Andreas Br?ve Britta Wahren Pavel Pisa 《PloS one》2009,4(9)
Background
Electrical pulses have been used to enhance uptake of molecules into living cells for decades. This technique, often referred to as electroporation, has become an increasingly popular method to enhance in vivo DNA delivery for both gene therapy applications as well as for delivery of vaccines against both infectious diseases and cancer. In vivo electrovaccination (gene delivery followed by electroporation) is currently being investigated in several clinical trials, including DNA delivery to healthy volunteers. However, the mode of action at molecular level is not yet fully understood.Methodology/Principal Findings
This study investigates intradermal DNA electrovaccination in detail and describes the effects on expression of the vaccine antigen, plasmid persistence and the local tissue environment. Gene profiling of the vaccination site showed that the combination of DNA and electroporation induced a significant up-regulation of pro-inflammatory genes. In vivo imaging of luciferase activity after electrovaccination demonstrated a rapid onset (minutes) and a long duration (months) of transgene expression. However, when the more immunogenic prostate specific antigen (PSA) was co-administered, PSA-specific T cells were induced and concurrently the luciferase expression became undetectable. Electroporation did not affect the long-term persistence of the PSA-expressing plasmid.Conclusions/Significance
This study provides important insights to how DNA delivery by intradermal electrovaccination affects the local immunological responses of the skin, transgene expression and clearance of the plasmid. As the described vaccination approach is currently being evaluated in clinical trials, the data provided will be of high significance. 相似文献10.
Background
The suitability of the strain Rhodococcus erythropolis ATCC 25544 grown in a two-liter fermentor as a source of cholesterol oxidase has been investigated. The strain produces both cell-linked and extracellular cholesterol oxidase in a high amount, that can be extracted, purified and concentrated by using the detergent Triton X-114. 相似文献11.
Fabian Zanella Aranzazú Rosado Beatriz Garcia Amancio Carnero Wolfgang Link 《BMC cell biology》2009,10(1):14-10
Background
Independent luciferase reporter assays and fluorescent translocation assays have been successfully used in drug discovery for several molecular targets. We developed U2transLUC, an assay system in which luciferase and fluorescent read-outs can be multiplexed to provide a powerful cell-based high content screening method. 相似文献12.
Background
Inositol is a key cellular metabolite for many organisms. Cryptococcus neoformans is an opportunistic pathogen which primarily infects the central nervous system, a region of high inositol concentration, of immunocompromised individuals. Through the use of myo-inositol oxygenase C. neoformans can catabolize inositol as a sole carbon source to support growth and viability. 相似文献13.
Goforth Harold W.; Arnall Jr. David A.; Bennett Brad L.; Law Patricia G. 《Journal of applied physiology》1997,82(1):342-347
Goforth, Jr., Harold W., David A. Arnall, Brad L. Bennett,and Patricia G. Law. Persistence of supercompensated muscle glycogen in trained subjects after carbohydrate loading.J. Appl. Physiol. 82(1): 342-347, 1997.Several carbohydrate (CHO)-loading protocols have been used toachieve muscle glycogen supercompensation and prolong enduranceperformance. This study assessed the persistence of muscle glycogensupercompensation over the 3 days after the supercompensation protocol.Trained male athletes completed a 6-day CHO-loading protocol thatincluded cycle ergometer exercise and dietary manipulations. The 3-daydepletion phase began with 115 min of cycling at 75% peak oxygenuptake followed by 3 × 60-s sprints and included the subjectsconsuming a low-CHO/high-protein/high-fat (10:41:49%) diet. Subjectscycled 40 min at the same intensity for the next 2 days. During the3-day repletion phase, subjects rested and consumed ahigh-CHO/low-protein/low-fat (85:08:07%) diet, including aglucose-polymer beverage. A 3-day postloading phase followed, whichinvolved a moderately high CHO diet (60%) and no exercise. Glycogenvalues for vastus lateralis biopsies at baseline and postloadingdays 1-3 were 408 ± 168 (SD),729 ± 222, 648 ± 186, and 714 ± 196 mmol/kg dry wt,respectively. The CHO-loading protocol increased muscle glycogen by1.79 times baseline, and muscle glycogen remained near this levelduring the 3-day postloading period. Results indicate thatsupercompensated muscle glycogen levels can be maintained for at least3 days in a resting athlete when a moderate-CHO diet is consumed. 相似文献
14.
Uffe V Schneider Jette K Severinsen Imrich Géci Limei M Okkels Nina Jøhnk Nikolaj D Mikkelsen Teena Klinge Erik B Pedersen Henrik Westh Gorm Lisby 《BMC biotechnology》2010,10(1):4
Background
Melting temperature of DNA structures can be determined on the LightCycler using quenching of FAM. This method is very suitable for pH independent melting point (Tm) determination performed at basic or neutral pH, as a high throughput alternative to UV absorbance measurements. At acidic pH quenching of FAM is not very suitable, since the fluorescence of FAM is strongly pH dependent and drops with acidic pH. 相似文献15.
Nagafumi Doi Yoko Hoshi Masanari Itokawa Chie Usui Takeo Yoshikawa Hirokazu Tachikawa 《PloS one》2009,4(11)
Background
The central paradox of schizophrenia genetics is that susceptibility genes are preserved in the human gene-pool against a strong negative selection pressure. Substantial evidence of epidemiology suggests that nuclear susceptibility genes, if present, should be sustained by mutation-selection balance without heterozygote advantage. Therefore, putative nuclear susceptibility genes for schizophrenia should meet special conditions for the persistence of the disease as well as the condition of bearing a positive association with the disease.Methodology/Principal Findings
We deduced two criteria that every nuclear susceptibility gene for schizophrenia should fulfill for the persistence of the disease under general assumptions of the multifactorial threshold model. The first criterion demands an upper limit of the case-control difference of the allele frequencies, which is determined by the mutation rate at the locus, and the prevalence and the selection coefficient of the disease. The second criterion demands an upper limit of odds ratio for a given allele frequency in the unaffected population. When we examined the top 30 genes at SZGene and the recently reported common variants on chromosome 6p with the criteria using the epidemiological data in a large-sampled Finnish cohort study, it was suggested that most of these are unlikely to confer susceptibility to schizophrenia. The criteria predict that the common disease/common variant hypothesis is unlikely to fit schizophrenia and that nuclear susceptibility genes of moderate effects for schizophrenia, if present, are limited to ‘rare variants’, ‘very common variants’, or variants with exceptionally high mutation rates.Conclusions/Significance
If we assume the nuclear DNA model for schizophrenia, it should have many susceptibility genes of exceptionally high mutation rates; alternatively, it should have many disease-associated resistance genes of standard mutation rates on different chromosomes. On the other hand, the epidemiological data show that pathogenic genes, if located in the mitochondrial DNA, could persist through sex-related mechanisms. 相似文献16.
17.
Wee Tek Tay Gajanan T Behere Philip Batterham David G Heckel 《BMC evolutionary biology》2010,10(1):144
Background
Developing lepidopteran microsatellite DNA markers can be problematical, as markers often exhibit multiple banding patterns and high frequencies of non-amplifying "null" alleles. Previous studies identified sequences flanking simple sequence repeat (SSR) units that are shared among many lepidopteran species and can be grouped into microsatellite-associated DNA families. These families are thought to be associated with unequal crossing-over during DNA recombination or with transposable elements (TEs). 相似文献18.
Background
Working at high solids (substrate) concentrations is advantageous in enzymatic conversion of lignocellulosic biomass as it increases product concentrations and plant productivity while lowering energy and water input. However, for a number of lignocellulosic substrates it has been shown that at increasing substrate concentration, the corresponding yield decreases in a fashion which can not be explained by current models and knowledge of enzyme-substrate interactions. This decrease in yield is undesirable as it offsets the advantages of working at high solids levels. The cause of the 'solids effect' has so far remained unknown. 相似文献19.
Belén Vázquez Fernando Esperón Elena Neves Juan López Carlos Ballesteros María Jesús Muñoz 《Acta veterinaria Scandinavica》2010,52(1):45
Background
Pathogens with the zoonotic potential to infect humans, such as Campylobacter jejuni, Campylobacter coli and Chlamydophila psittaci, can be found in feral pigeons (Columba livia). Given the high density of these birds in the public parks and gardens of most cities, they may pose a direct threat to public health. 相似文献20.