Mysterious role of H3K56ac in embryonic stem cells.

Posttranslational modifications of histones belong to epigenetic mechanisms that regulate gene expression by chromatin structure changes. Generally, histone acetylation reduces its positive charge and consequently weakens the stability of the nucleosome. Acetylation of lysine 56 on histone H3 is implicated in the processes associated with loosened chromatin structure. H3K56ac is a mark for histones with high nucleosome turnover in the nuclear processes such as gene transcription, DNA replication and reparation in yeasts. During evolution, the main H3K56ac regulatory pathway was lost and the level of H3K56ac remained very low in mammalian cells. Moreover, the function of this modification still remains unclear. In this minireview, we summarize the recent knowledge of the ambiguous role of H3K56ac in mammalian embryonic stem cells.

Haematopoietic developmental potential of human pluripotent stem cell lines.

The generation of haematopoietic progenitors from human pluripotent stem cells (hPSCs) presents great promise for cell-replacement therapies. However, current protocols for haematopoietic differentiation of hPSCs suffer from low efficiency and functional defects in the derived cells. The technology is also limited by variable ability of hPSC lines to generate blood cells in vitro. To address this issue, methodologies for haematopoietic differentiation in feeder-free conditions were applied to available human embryonic stem cell (hESC) and human induced pluripotent stem cell (hiPSC) lines in this study. It was found that these cell lines did not generate haematopoietic progenitors to such an extent as did H1 and H9 hESC lines that were used for this purpose in the vast majority of relevant studies. These results suggest that for clinical application of blood cells derived from hPSCs, possibly from autologous hiPSCs, it is necessary to overcome the variability in the haematopoietic developmental potential of individual hPSC lines.

Isolation of granulocytes: which transcriptome do we analyse - neutrophils or eosinophils?

Isolation of granulocytes from blood is necessary for accurate study of changes in their expression. After gradient centrifugation, we obtain relatively pure granulocyte populations with different ratios of neutrophils and eosinophils. Unfortunately, in many studies in this field the expression results are not set according to the real variability of the granulocyte population. In many cases, the granulocyte population is marked simply as "neutrophils" and the residual population of eosinophils is not considered. Based on our recent study where we tracked the general transcription factor RNA polymerase II, we hypothesized that eosinophils are more transcriptionally active cells than neutrophils. We decided to test our hypothesis on isolated cells because its implications could change our view on many past expression analyses performed on granulocytes. In our experiments, we isolated neutrophils and eosinophils and measured their total RNA production. According to our results, eosinophils produce much more RNA than neutrophils. Therefore, relatively low numbers of highly active eosinophils can markedly affect the whole pool of granulocytic RNA. We want to emphasize that either a detailed description of the cell population or the use of a pure neutrophil population is necessary for the correct interpretation of neutrophil expression analysis results.

Combination of mRNA and protein microarray analysis in complex cell profiling.

UNLABELLED: This study combines mRNA and protein analysis using cDNA and antibody microarray techniques, respectively. These create a novel, integrated perspective into cellular molecular profiles. The aims of this study were to establish a reliable way of integrating these two approaches in order to obtain complex molecular profiles of the cell and to find suitable methods to normalize the data obtained using these approaches.

Antibody microarray and cDNA microarray techniques were used to study expression alterations in HL-60 cells that were differentiated into granulocytes using all-trans retinoic acid (ATRA). We selected this model to evaluate this combined profiling technique because the expression levels of most of the mRNA and protein species in these cells are not altered; therefore it is easier to track and define those species that are changed. The proteins whose levels were altered included c-myc, c-jun, Pyk2, FAK, PKC, TRF1, NF-kappaB and certain caspase types. These proteins are involved in apoptosis and hematopoietic differentiation pathways, and some have also been reported to have oncogenic potential. We compared the results obtained using the two methods, verified them by immunoblotting analysis, and devised normalization approaches.

This is one of the first demonstrations that a combination of antibody microarray and cDNA microarray techniques is required for complex molecular profiling of cells based on multiple parameters. This approach allows a more detailed molecular phenotype of the given sample to be obtained. The results obtained using a combination of the two profiling methods are consistent with those from previous studies that used more traditional methods.

Submuscular versus subcutaneous pectoral implantation of cardioverter-defibrillators: effect on high voltage pathway impedance and defibrillation efficacy.

Implantable cardioverter-defibrillator (ICD) pulse generators are now routinely positioned in a pectoral location, either submuscularly (under the pectoralis muscles) or subcutaneously (over the pectoralis muscles). Furthermore, in current ICDs, the generator shield usually participates in the defibrillation energy pathway ("hot can"). Consequently, the precise generator location could affect defibrillation system efficacy. To assess this issue, we compared high voltage pathway impedance and defibrillation threshold (DFT) in 20 patients undergoing submuscular and 46 patients undergoing subcutaneous pectoral implantation of an Angeion Sentinel ICD and an AngeFlex dual-coil defibrillation lead. Measurements were performed at time of ICD implant, pre-hospital discharge, and 1, 3 and/or 6 months later. Following induction of ventricular fibrillation, 569 biphasic waveform shocks were delivered between the generator shield and either the distal defibrillation coil (RV/can configuration) or both proximal and distal coils (RV/SVC/can configuration). Impedance differences between submuscular and subcutaneous implants were approximately 3-4 Ohms (p value of 0.132 to < 0.001 depending on time of follow-up and lead configuration). A significant increase in impedance over time was noted independent of implant location and lead configuration. The DFT at implant or pre-discharge was assessed in 27 individuals, and was 9.9 +/- 3.8 J in 8 patients in the submuscular group, and 7.4 +/- 3.3 J in 19 patients in the subcutaneous group (p = 0.057). In conclusion, anatomic location of a "hot can" ICD generator (submuscular versus subcutaneous) influences impedance to defibrillation current, but the impact is of small magnitude and does not appear to result in clinically important differences in DFT.

Element concentrations in livers and kidneys of ranch mink.

Reference ranges for element concentrations in livers and kidneys of "healthy" mink of known age, sex, and coat color and fed a conventional diet were determined. After euthanasia and removal of the pelts, liver and kidney samples were collected from 174 mink and analyzed for 22 elements using inductively coupled argon plasma emission spectroscopy. The diet of the mink was also analyzed for element concentrations. Descriptive statistics of element concentrations for livers and kidneys of the mink are given and compared with dietary element concentrations.