Novel bioluminescent quantitative detection of nucleic acid amplification in real-time

Background

The real-time monitoring of polynucleotide amplification is at the core of most molecular assays. This conventionally relies on fluorescent detection of the amplicon produced, requiring complex and costly hardware, often restricting it to specialised laboratories.

Principal Findings

Here we report the first real-time, closed-tube luminescent reporter system for nucleic acid amplification technologies (NAATs) enabling the progress of amplification to be continuously monitored using simple light measuring equipment. The Bioluminescent Assay in Real-Time (BART) continuously reports through bioluminescent output the exponential increase of inorganic pyrophosphate (PP_i) produced during the isothermal amplification of a specific nucleic acid target. BART relies on the coupled conversion of inorganic pyrophosphate (PP_i) produced stoichiometrically during nucleic acid synthesis to ATP by the enzyme ATP sulfurylase, and can therefore be coupled to a wide range of isothermal NAATs. During nucleic acid amplification, enzymatic conversion of PP_i released during DNA synthesis into ATP is continuously monitored through the bioluminescence generated by thermostable firefly luciferase. The assay shows a unique kinetic signature for nucleic acid amplifications with a readily identifiable light output peak, whose timing is proportional to the concentration of original target nucleic acid. This allows qualitative and quantitative analysis of specific targets, and readily differentiates between negative and positive samples. Since quantitation in BART is based on determination of time-to-peak rather than absolute intensity of light emission, complex or highly sensitive light detectors are not required.

Conclusions

The combined chemistries of the BART reporter and amplification require only a constant temperature maintained by a heating block and are shown to be robust in the analysis of clinical samples. Since monitoring the BART reaction requires only a simple light detector, the iNAAT-BART combination is ideal for molecular diagnostic assays in both laboratory and low resource settings.     

Circulating Endothelial Progenitor Cells and Clinical Outcome in Patients with Aortic Stenosis

Background

Aortic stenosis (AS) is the most common valvular disease. Endothelial progenitor cells (EPCs) have a role in the repair of endothelial surfaces after injury. Reduced numbers of EPCs are associated with endothelial dysfunction and adverse clinical events, suggesting that endothelial injury in the absence of sufficient repair by circulating EPCs promotes the progression of vascular and possibly valvular disorders. The aim of this study was to assess EPC number in patients with AS and to study the predictive value of their circulating levels on prognosis.

Methods

The number of EPCs was determined by flow cytometry in 241 patients with AS and a control group of 73 pts. Thirty-eight, 52 and 151 patients had mild, moderate and severe AS, respectively. We evaluated the association between baseline levels of EPCs and death from cardiovascular causes during follow up.

Results

EPC level was significantly higher in patients with AS compared to the control group (p = 0.017). Two hundred and three patients with moderate and severe AS were followed for a median of 20 months. One hundred and twenty patients underwent an intervention. Thirty four patients died during follow up, 20 patients died due to cardiac causes. Advanced age, the presence of coronary artery disease, AS severity index (combination of high NYHA class, smaller aortic valve area and elevated pulmonary artery pressure) and a low EPC number were predictors of cardiac death in the univariate analysis. Multivariate logistic regression model identified low EPCs number and AS severity index as associated with cardiac death during follow up (p = 0.026 and p = 0.037, respectively).

Conclusions

EPC number is increased in patients with AS. However, in patients with moderate or severe AS a relatively low number of EPCs is associated with cardiac death at follow up. These results may help to identify AS patients at increased cardiovascular risk.     

Onion yield as affected by plant density,nitrogen level and loss of leaf area

Onion (Allium cepa) is an important horticulture crop because of its value as a food with a long shelf life being a relatively non-perishable product. It is very helpful to understand the growth response of the seeded onion crop to conduct appropriate field practices in attaining the highest or optimum yields. A three year field experiment was conducted using a variety of onion Valcatorce INTA, in a randomized block design with five replicates. Treatments were two plant densities and three rates of N application. The bulb growth followed a classical sigmoid curve. During the rapid growing period, the crop had the greatest leaf area (LA) with at least six leaves per plant. Increasing plant density increased yield in kg/ha, but decreased bulb size. Defoliating 40 to 60% of the LA had a significant impact on bulb production only at early growth stages. Late in the growing period, the remaining LA was apparently large enough for producing sufficient amounts of metabolites to feed new leaves, increasing their photosynthesis efficiency for the benefit of bulb production.     

Pregnancy success of lactating Holstein cows after a single administration of a sustained-release formulation of recombinant bovine somatotropin

Background

Results regarding the use of bovine somatotropin for enhancing fertility in dairy cattle are variable. Here, the hypothesis was tested that a single injection of a sustained-release preparation of bovine somatotropin (bST) during the preovulatory period would improve pregnancy success of lactating dairy cows at first service.

Results

The first experiment was conducted in a temperate region of Mexico. Cows inseminated following natural estrus or timed artificial insemination were given a single injection of bST or a placebo injection at insemination (n = 100 cows per group). There was no significant difference between bST and control groups in the proportion of inseminated cows diagnosed pregnant (29 vs 31% pregnant). The second experiment was performed during heat stress in Florida. Cows were subjected to an ovulation synchronization regimen for first insemination. Cows treated with bST received a single injection at 3 days before insemination. Controls received no additional treatment. As expected, bST did not increase vaginal temperature. Treatment with bST did not significantly increase the proportion of inseminated cows diagnosed pregnant although it was numerically greater for the bST group (24.2% vs 17.8%, 124–132 cows per group). There was a tendency (p = 0.10) for a smaller percent of control cows to have high plasma progesterone concentrations (≥ 1 ng/ml) at Day 7 after insemination than for bST-treated cows (72.6 vs 81.1%). When only cows that were successfully synchronized were considered, the magnitude of the absolute difference in the percentage of inseminated cows that were diagnosed pregnant between bST and control cows was reduced (24.8 vs 22.4% pregnant for bST and control).

Conclusion

Results failed to indicate a beneficial effect of bST treatment on fertility of lactating dairy cows.

     

Uterine position and the activation of male sexual activity in testosterone propionate-treated female guinea pigs

Fetal female guinea pigs were delivered surgically and their position within a uterine horn relative to male fetuses was noted. When adult they were ovariectomized, injected daily with testosterone propionate, and examined for male copulatory behaviors in response to the presence of a receptive female. Females that developed contiguous to a caudal male were functionally similar to those that had been situated between two males; both exhibited enhanced levels of mounting relative to females that were located contiguous to no males (with and without the presence of a caudal male) and to females contiguous to a cephalic male. Therefore, both contiguity and positioning of the male fetus are necessary conditions for prenatal masculinization of the female guinea pig. Lastly, four animals that had resided singly in the uterus displayed the lowest levels of copulatory behaviors.     

Enzyme replacement therapy for Mucopolysaccharidosis Type I among patients followed within the MPS Brazil Network

Mucopolysaccharidosis type I (MPS I) is a rare lysosomal disorder caused by deficiency of alpha-L-iduronidase. Few clinical trials have assessed the effect of enzyme replacement therapy (ERT) for this condition. We conducted an exploratory, open-label, non-randomized, multicenter cohort study of patients with MPS I. Data were collected from questionnaires completed by attending physicians at the time of diagnosis (T1; n = 34) and at a median time of 2.5 years later (T2; n = 24/34). The 24 patients for whom data were available at T2 were allocated into groups: A, no ERT (9 patients; median age at T1 = 36 months; 6 with severe phenotype); B, on ERT (15 patients; median age at T1 = 33 months; 4 with severe phenotype). For all variables in which there was no between-group difference at baseline, a delta of ≥ ± 20% was considered clinically relevant. The following clinically relevant differences were identified in group B in T2: lower rates of mortality and reported hospitalization for respiratory infection; lower frequency of hepatosplenomegaly; increased reported rates of obstructive sleep apnea syndrome and hearing loss; and stabilization of gibbus deformity. These changes could be due to the effect of ERT or of other therapies which have also been found more frequently in group B. Our findings suggest MPS I patients on ERT also receive a better overall care. ERT may have a positive effect on respiratory morbidity and overall mortality in patients with MPS I. Additional studies focusing on these outcomes and on other therapies should be performed.