The magic spot ppGpp influences in vitro the molecular and functional properties of the elongation factor 1α from the archaeon Sulfolobus solfataricus

Guanosine tetra-phosphate (ppGpp), also known as "magic spot I", is a key molecule in the stringent control of most eubacteria and some eukarya. Here, we show that ppGpp affects the functional and molecular properties of the archaeal elongation factor 1α from Sulfolobus solfataricus (SsEF-1α). Indeed, ppGpp inhibited archaeal protein synthesis in vitro, even though the concentration required to get inhibition was higher than that required for the eubacterial and eukaryal systems. Regarding the partial reactions catalysed by SsEF-1α the effect produced by ppGpp on the affinity for aa-tRNA was lower than that measured in the presence of GTP but higher than that for GDP. Magic spot I was also able to bind SsEF-1α with an intermediate affinity in comparison to that displayed by GDP and GTP. Furthermore, ppGpp inhibited the intrinsic GTPase of SsEF-1α with a competitive behaviour. Finally, the binding of ppGpp to SsEF-1α rendered the elongation factor more resistant to heat treatment and the analysis of the molecular model of the complex between SsEF-1α and ppGpp suggests that this stabilisation arises from the charge optimisation on the surface of the protein.     

Effects of Slow Deep Breathing at High Altitude on Oxygen Saturation,Pulmonary and Systemic Hemodynamics

Slow deep breathing improves blood oxygenation (Sp_O2) and affects hemodynamics in hypoxic patients. We investigated the ventilatory and hemodynamic effects of slow deep breathing in normal subjects at high altitude. We collected data in healthy lowlanders staying either at 4559 m for 2–3 days (Study A; N = 39) or at 5400 m for 12–16 days (Study B; N = 28). Study variables, including Sp_O2 and systemic and pulmonary arterial pressure, were assessed before, during and after 15 minutes of breathing at 6 breaths/min. At the end of slow breathing, an increase in Sp_O2 (Study A: from 80.2±7.7% to 89.5±8.2%; Study B: from 81.0±4.2% to 88.6±4.5; both p<0.001) and significant reductions in systemic and pulmonary arterial pressure occurred. This was associated with increased tidal volume and no changes in minute ventilation or pulmonary CO diffusion. Slow deep breathing improves ventilation efficiency for oxygen as shown by blood oxygenation increase, and it reduces systemic and pulmonary blood pressure at high altitude but does not change pulmonary gas diffusion.     

Rationale and design of the Edwards SAPIEN-3 periprosthetic leakage evaluation versus Medtronic CoreValve in transfemoral aortic valve implantation (ELECT) trial

Background and objectives

Periprosthetic aortic regurgitation (PPR) after transcatheter aortic valve implantation (TAVI) remains an important issue associated with impaired long-term outcomes. The current randomised study aims to evaluate potential differences between the balloon-expandable Edwards SAPIEN-3 and the self-expanding Medtronic CoreValve system with the main focus on post-TAVI PPR by means of novel imaging endpoints, and an additional focus on other clinical endpoints.

Endpoints

The primary endpoint of this study is quantitative assessment of the severity of post-procedural PPR using cardiac magnetic resonance imaging. Several other novel imaging modalities (X-ray contrast angiography, echocardiography) are used as secondary imaging modalities for the assessment of PPR following TAVI. Secondary objectives of the study include clinical outcomes such as cerebral and kidney injury related to TAVI, and quality of life.

Methods and design

The ELECT study is a single-centre, prospective, two-armed randomised controlled trial. For the purpose of this study, 108 consecutive adult patients suitable for transfemoral TAVI will be randomly allocated to receive the SAPIEN-3 (n = 54) or the CoreValve system (n = 54).

Discussion

The ELECT trial is the first randomised controlled trial to quantitatively compare the extent of post-TAVI PPR between the SAPIEN-3 and CoreValve. Furthermore, it will evaluate potential differences between the two prostheses with regard to mid-term clinical outcome and quality of life.

     

Sperm protein 17 is expressed in human somatic ciliated epithelia.

It was once believed that sperm protein 17 (Sp17) was expressed exclusively in the testis and that its sole function was to bind to the oocyte during fertilization. However, immunohistochemistry of the human respiratory airways and reproductive systems show that it is abundant in ciliated cells but not in human cells with stereocilia and microvilli. The high degree of sequence conservation throughout its N-terminal half, and the presence of an A-kinase anchoring protein (AKAP)-binding motif within this region, suggest that Sp17 plays a regulatory role in a PKA-independent AKAP complex in both male germinal and ciliated somatic cells.     

Archaeal elongation factor 1α from <Emphasis Type="Italic">Sulfolobus solfataricus</Emphasis> interacts with the eubacterial antibiotic GE2270A

The thiazolyl-peptide antibiotic GE2270A, an inhibitor of the elongation factor Tu from Escherichia coli (EcEF-Tu), was used to study the effects produced in the biochemical properties of the archaeal functional analogue elongation factor 1 from Sulfolobus solfataricus (SsEF-1). GE2270A did not substantially affect the poly(U)-directed-poly(Phe) incorporation catalyzed by SsEF-1 and the formation of the ternary complex SsEF-1·GTP·Phe-tRNA^Phe. On the other hand, the antibiotic was able to increase the GDP/GTP exchange rate of SsEF-1; nevertheless, this improvement was not associated with an increase in the catalytic activity of the enzyme. In fact, GE2270A inhibited both the intrinsic GTPase of SsEF-1 (GTPase^Na) and that stimulated by ribosomes. Interestingly, GTPase^Na of both intact and C-terminal-deleted SsEF-1 resulted in a greater sensitivity to the antibiotic with respect to SsEF-1 lacking both the M- and C-terminal domains. This result suggested that, similar to what is found for EcEF-Tu, the M domain of SsEF-1 is the region of the enzyme most responsible for the interaction with GE2270A. The different behavior observed in the inhibition of protein synthesis with respect to EcEF-Tu can be ascribed to the different adaptive structural changes that have occurred in SsEF-1 during evolution.     

Breastfeeding duration, milk fat composition and developmental indices at 1 year of life among breastfed infants

The associations of breastfeeding duration and milk fat composition with the developmental outcome at 1 year of age were measured within 44 infants exclusively breastfed for 3 months, out of 95 recruited at birth. Pooled breast milk (hindmilk) of the mothers was analysed at colostrum, 1, 3, 6, 9, and 12 months for total fat and fatty acid content. Infants were examined at 12 months by means of the Bayley test. There was a progressive reduction of the number of breastfed babies after the introduction of solids to 29 (6 months), 17 (9 months) and 10 (12 months). After adjusting for major confounders, infants breastfed for 6 months or longer showed a trend to have an advantage at the Bayley psychomotor developmental index compared to those breastfed >3 and <6 months (95% CI for difference: - 0.6, 13.8; P= 0.07) while the Bayley mental developmental index (MDI) was just 2.1 points higher. Among the milk fat components considered for each time-point, the total fat content at 6 months showed the strongest association with the MDI at 12 months (r=0.59, P=0.001). Prolonging breastfeeding during the weaning process may result in a better developmental performance at 12 months, possibly due to the supply of fats affecting brain composition.     

Phage display of a CTL epitope elicits a long-term in vivo cytotoxic response

The Ovalbumin(257-264) CTL epitope on the major coat protein of the filamentous bacteriophage in different antigen formulations was displayed and the immune response in C57BL6/J mice studied. The display of single cytotoxic epitope on the surface of the virion is sufficient to induce priming and sustain long-term major histocompatibility complex class I restricted cytotoxic T lymphocytes response in vivo. The filamentous bacteriophage is a versatile carrier able to display simultaneously either single or multiple epitopes and can elicit a cellular response carrying very little peptide (<1.5 microg).