The energetic difference between synthesis of correct and incorrect base pairs accounts for highly accurate DNA replication

To better understand the energetics of accurate DNA replication, we directly measured ΔG(o) for the incorporation of a nucleotide into elongating dsDNA in solution (ΔG(o)(incorporation)). Direct measurements of the energetic difference between synthesis of correct and incorrect base pairs found it to be much larger than previously believed (average ΔΔG(o)(incorporation) = 5.2 ± 1.34 kcal mol(-1)). Importantly, these direct measurements indicate that ΔΔG(o)(incorporation) alone can account for the energy required for highly accurate DNA replication. Evolutionarily, these results indicate that the earliest polymerases did not have to evolve sophisticated mechanisms to replicate nucleic acids; they may only have had to take advantage of the inherently more favorable ΔG(o) for polymerization of correct nucleotides. These results also provide a basis for understanding how polymerases replicate DNA (or RNA) with high fidelity.

Developmental delay of infants and young children with and without fetal alcohol spectrum disorder in the Northern Cape Province, South Africa

OBJECTIVE

To describe the extent and nature of developmental delay at different stages in childhood in a community in South Africa, with a known high rate of Fetal Alcohol Spectrum Disorder (FASD).

METHOD

cohort of infants, clinically examined for FASD at two time periods, 7-12 months (N= 392; 45 FASD) and 17-21 months of age (N = 83, 35 FASD) were assessed using the Griffiths Mental Developmental Scales (GMDS).

RESULTS

Infants and children with FASD perform worse than their Non-FASD counterparts over all scales and total developmental quotients. Mean quotients for both groups decline between assessments across subscales with a particularly marked decline in the hearing and language scale at Time 2 (scores dropping from 110.6 to 83.1 in the Non-FASD group and 106.3 to 72.7 in the FASD group; P = 0.004). By early childhood the developmental gap between the groups widens with low maternal education, maternal depression, high parity and previous loss of sibling/s influencing development during early childhood.

CONCLUSION

The FASD group show more evidence of developmental delay over both time points compared to their Non-FASD counterparts. Demographic and socio-economic factors further impact early childhood. These findings are important in setting up primary level psycho-educational and national prevention programmes especially in periurban communities with a focus on early childhood development and FASD.

[Obesity and male infertility]

The authors present a review on the effects of obesity on male fertility. Current scientific findings suggest an elevated risk of infertility among couples in which the male partner is obese. In obese men can be found reduced serum levels of androgens and SHBG and increased estrogen levels without compensatory increase in FSH. Among other impacts of male obesity that may contribute to increased risk of infertility are altered retention and metabolism of environmental toxins, lifestyle, sexual dysfunction, genetic factors, excessive secretion of hormones derived from adipose tissue, oxidative stress, sperm specific proteomic changes or elevated levels of cytokines. The increasing prevalence of obesity calls for greater clinical awareness of its impact on male fertility.

Measurement of the proton-air cross section at √s=57 TeV with the Pierre Auger Observatory

We report a measurement of the proton-air cross section for particle production at the center-of-mass energy per nucleon of 57 TeV. This is derived from the distribution of the depths of shower maxima observed with the Pierre Auger Observatory: systematic uncertainties are studied in detail. Analyzing the tail of the distribution of the shower maxima, a proton-air cross section of [505±22(stat)(-36)(+28)(syst)] mb is found.

Heart transplantations at the Heart Center IKEM, Prague, Czech Republic

The heart transplant program at the Institute for Clinical and Experimental Medicine in Prague was established on January 31, 1984. Through November 2012, 881 orthotopic cardiac transplantations have been performed, with an annual rate of about 40 procedures. Current legislation concerning solid organ transplantations in the Czech Republic is described. Like other centers, we have noticed an increasing age of donors, and, reflecting the shortage of grafts, we have expanded our selection criteria for heart transplantation. The advent of a mechanical circulatory support program at our center in April 2003 has given us another valuable tool in the management of chronic heart failure patients. Currently, around half of our patients are transplanted from mechanical support. Nonischemic etiology of heart failure is a leading cause of transplantation at our center, followed by ischemic cardiomyopathy, valvular heart lesions, and adult congenital heart diseases. Our current immunosupression protocol, including induction therapy, is outlined in detail and survival rates, as well as most common complications and our treatment strategies, are also discussed.

B family DNA polymerases asymmetrically recognize pyrimidines and purines

We utilized a series of pyrimidine analogues modified at O(2), N-3, and N(4)/O(4) to determine if two B family DNA polymerases, human DNA polymerase α and herpes simplex virus I DNA polymerase, choose whether to polymerize pyrimidine dNTPs using the same mechanisms they use for purine dNTPs. Removing O(2) of a pyrimidine dNTP vastly decreased the level of incorporation by these enzymes and also compromised fidelity in the case of C analogues, while removing O(2) from the templating base had more modest effects. Removing the Watson-Crick hydrogen bonding groups of N-3 and N(4)/O(4) greatly impaired polymerization, both of the resulting dNTP analogues and of natural dNTPs opposite these pyrimidine analogues when present in the template strand. Thus, the Watson-Crick hydrogen bonding groups of a pyrimidine clearly play an important role in enhancing correct dNTP polymerization but are not essential for preventing misincorporation. These studies also indicate that DNA polymerases recognize bases extremely asymmetrically, both in terms of whether they are a purine or pyrimidine and whether they are in the template or are the incoming dNTP. The mechanistic implications of these results with regard to how polymerases discriminate between right and wrong dNTPs are discussed.

[Spontaneous rupture of uterine vessels during pregnancy in a patient with previous endometriosis]

Spontaneous rupture of the utero-ovarian vessels during pregnancy is a rare condition that can be life-threatening. Endometriosis is one of the factors associated with this complication of the pregnancy. Location of the pain as well as the course of this complication can simulate various diseases that must be dealt with. We describe the case associated with haemoperitoneum and hemorrhagic shock.

Simulation of beta radiator handling procedures in nuclear medicine by means of a movable hand phantom

In nuclear medicine therapies, people working with beta radiators such as (90)Y may be exposed to non-negligible partial body doses. For radiation protection, it is important to know the characteristics of the radiation field and possible dose exposures at relevant positions in the working area. Besides extensive measurements, simulations can provide these data. For this purpose, a movable hand phantom for Monte Carlo simulations was developed. Specific beta radiator handling scenarios can be modelled interactively with forward kinematics or automatically with an inverse kinematics procedure. As a first investigation, the dose distribution on a medical doctor's hand injecting a (90)Y solution was measured and simulated with the phantom. Modelling was done with the interactive method based on five consecutive frames from a video recorded during the injection. Owing to the use of only one camera, not each detail of the radiation scenario is visible in the video. In spite of systematic uncertainties, the measured and simulated dose values are in good agreement.

Theoretical assessment of whole body counting performances using numerical phantoms of different gender and sizes

A goal of whole body counting (WBC) is the estimation of the total body burden of radionuclides disregarding the actual position within the body. To achieve the goal, the detectors need to be placed in regions where the photon flux is as independent as possible from the distribution of the source. At the same time, the detectors need high photon fluxes in order to achieve better efficiency and lower minimum detectable activities. This work presents a method able to define the layout of new WBC systems and to study the behaviour of existing ones using both detection efficiency and its dependence on the position of the source within the body of computational phantoms.

Simulating Makrofol as a detector for neutron-induced recoils

The response of solid-state nuclear track detector is extremely dependent on incident angles of neutrons, which determine the angular distribution of secondary particles. In this paper, the authors present a method to investigate the angular response of Makrofol detectors. Using the C++-based Monte-Carlo tool-kit Geant4 in combination with SRIM and our MATLAB codes, we simulated the angular response of Makrofol. The simulations were based on the restricted energy loss model, and the concept of energy threshold and critical angle. Experiments were carried out with (252)Cf neutrons to verify the simulation results.

[Technique of implantation and experience with temporary mechanical cardiac support in right ventricular failure]

AIM

Severe right heart failure remains unfrequent but fatal complication of cardiac surgical procedures. Implantation of temporary right ventricular assist device may be life-saving procedure in various situations of right heart failure as: heart transplantation, LVAD therapy and post-cardiotomy failure. The aim of the study is an introduction of the implantation technique and retrospective review of current experience with the method.

MATERIAL AND METHODS

Since January 2007 isolated right ventricular assist device Levitronix CentriMag has been implanted in 16 patients. Patients were divided into 3 groups: post transplantation (post-Tx), post LVAD implantation (post-LVAD) and other cardiac procedures (OCP). Success rate of weaning from RVAD, 30-days mortality and major complications has been assessed.

OUTCOMES

Distribution of implants in groups was: post-Tx 5 pts (31%), post-LVAD 6 pts (38%) and 5 in OCP group (31%). The mean support time was 12 days. Off-pump implantation was achieved in 9 pts. The device was successfully weaned in 13 (81%) patients. 30-days mortality occurred in 1 case only.

CONCLUSION

Presented outcomes are encouraging for broader acceptance of the therapy. Excellent success rate has been reached in post-Tx and post-LVAD. This study emphasises decesive role of proactive approach in early indication of RVAD implantation for achieving satisfactory results.