Engineered heart tissue grafts improve systolic and diastolic function in infarcted rat hearts

The concept of regenerating diseased myocardium by implantation of tissue-engineered heart muscle is intriguing, but convincing evidence is lacking that heart tissues can be generated at a size and with contractile properties that would lend considerable support to failing hearts. Here we created large (thickness/diameter, 1-4 mm/15 mm), force-generating engineered heart tissue from neonatal rat heart cells. Engineered heart tissue formed thick cardiac muscle layers when implanted on myocardial infarcts in immune-suppressed rats. When evaluated 28 d later, engineered heart tissue showed undelayed electrical coupling to the native myocardium without evidence of arrhythmia induction. Moreover, engineered heart tissue prevented further dilation, induced systolic wall thickening of infarcted myocardial segments and improved fractional area shortening of infarcted hearts compared to controls (sham operation and noncontractile constructs). Thus, our study provides evidence that large contractile cardiac tissue grafts can be constructed in vitro, can survive after implantation and can support contractile function of infarcted hearts.     

Two-dimensional mapping of photopigment distribution and activity of Chloroflexus-like bacteria in a hypersaline microbial mat

Pigment analysis in an intact hypersaline microbial mat by hyperspectral imaging revealed very patchy and spatially uncorrelated distributions of photopigments Chl a and BChl a/c, which are characteristic photopigments for oxygenic (diatoms and cyanobacteria) and anoxygenic phototrophs (Chloroflexaceae). This finding is in contrast to the expectation that these biomarker pigments should be spatially correlated, as oxygenic phototrophs are thought to supply the Chloroflexaceae members with organic substrates for growth. We suggest that the heterogeneous occurrence is possibly due to sulfide, whose production by sulfate-reducing bacteria may be spatially heterogeneous in the partially oxic photic zone of the mat. We furthermore mapped the near-infra-red-light controlled respiration of Chloroflexaceae under light and dark conditions and found that Chloroflexaceae are responsible for a major part of oxygen consumption at the lower part of the oxic zone in the mat. The presence of Chloroflexaceae was further confirmed by FISH probe and 16S rRNA gene clone library analysis. We assume that species related to the genera Oscillochloris and 'Candidatus Chlorothrix', in contrast to those related to Chloroflexus and Roseiflexus, depend less on excreted photosynthates but more on the presence of free sulfide, which may explain their presence in deeper parts of the mat.     

DNA sequence analysis of the tellurite-resistance determinant from clinical strain of Escherichia Coli and identification of essential genes

The tellurite-resistant Escherichia coli strain KL53 was found during testing of the group of clinical isolates for antibiotics and heavy metal ion resistance (Burian et al. 1990). Determinant of the tellurite resistance of the strain was located on the large conjugative plasmid pTE53 and cloned into pACYC184. Three different Te^r clones harboring pLK2, pLK18 and pLK20 were isolated (Burian et al. 1998). The smallest functional Te^r clone harboring pLK18 was chosen for further analysis. Plasmid pLK18 have been subcloned to obtain convenient DNA fragments for sequencing of tellurite-resistance determinant. Sequencing of this DNA fragments provided complete DNA sequence of the determinant, 5250 bp in size. The sequence has been compared with nucleotide and protein databank (BLAST programs) and significant homology with the three known operons coding for tellurite resistance has been found (determinat on plasmid pR478 from Serratia marcescens, on plasmid pMER610 from Alcaligenes sp. and chromosomal tellurite resistance genes from Proteus mirabilis). We identified 5 ORFs coding for 5 genes named terB to terF. The clone harboring pLK18 was subjected to the transposition with Tn1737Km to disrupt determinant of the tellurite resistance. Plasmid DNA of several clones containing pLK18 with Tn1737Km was isolated to locate the target site of Tn1737Km. Analyses showed, the genes terB, terC, terD and terE are essential for conservation of the resistance whereas the gene terF is not important in this respect.     

Heteroplasmy analysis in the Polish patients with 11778A mutation responsible for Leber hereditary optic neuropathy

We have analysed the heteroplasmy level in 11 individuals from 3 families harbouring the mitochondrial 11778A mutation responsible for Leber hereditary optic neuropathy using last cycle hot PCR. The mutation level exceeded 90% both in affected and in unaffected individuals. We also checked whether any of the families belonged to the J haplogroup of mitochondrial DNA and obtained a negative result.     

Anoxygenic Photosynthesis Controls Oxygenic Photosynthesis in a Cyanobacterium from a Sulfidic Spring

Before the Earth''s complete oxygenation (0.58 to 0.55 billion years [Ga] ago), the photic zone of the Proterozoic oceans was probably redox stratified, with a slightly aerobic, nutrient-limited upper layer above a light-limited layer that tended toward euxinia. In such oceans, cyanobacteria capable of both oxygenic and sulfide-driven anoxygenic photosynthesis played a fundamental role in the global carbon, oxygen, and sulfur cycle. We have isolated a cyanobacterium, Pseudanabaena strain FS39, in which this versatility is still conserved, and we show that the transition between the two photosynthetic modes follows a surprisingly simple kinetic regulation controlled by this organism''s affinity for H₂S. Specifically, oxygenic photosynthesis is performed in addition to anoxygenic photosynthesis only when H₂S becomes limiting and its concentration decreases below a threshold that increases predictably with the available ambient light. The carbon-based growth rates during oxygenic and anoxygenic photosynthesis were similar. However, Pseudanabaena FS39 additionally assimilated NO₃⁻ during anoxygenic photosynthesis. Thus, the transition between anoxygenic and oxygenic photosynthesis was accompanied by a shift of the C/N ratio of the total bulk biomass. These mechanisms offer new insights into the way in which, despite nutrient limitation in the oxic photic zone in the mid-Proterozoic oceans, versatile cyanobacteria might have promoted oxygenic photosynthesis and total primary productivity, a key step that enabled the complete oxygenation of our planet and the subsequent diversification of life.     

The Discovery of Stromatolites Developing at 3570 m above Sea Level in a High-Altitude Volcanic Lake Socompa,Argentinean Andes

We describe stromatolites forming at an altitude of 3570 m at the shore of a volcanic lake Socompa, Argentinean Andes. The water at the site of stromatolites formation is alkaline, hypersaline, rich in inorganic nutrients, very rich in arsenic, and warm (20–24°C) due to a hydrothermal input. The stromatolites do not lithify, but form broad, rounded and low-domed bioherms dominated by diatom frustules and aragonite micro-crystals agglutinated by extracellular substances. In comparison to other modern stromatolites, they harbour an atypical microbial community characterized by highly abundant representatives of Deinococcus-Thermus, Rhodobacteraceae, Desulfobacterales and Spirochaetes. Additionally, a high proportion of the sequences that could not be classified at phylum level showed less than 80% identity to the best hit in the NCBI database, suggesting the presence of novel distant lineages. The primary production in the stromatolites is generally high and likely dominated by Microcoleus sp. Through negative phototaxis, the location of these cyanobacteria in the stromatolites is controlled by UV light, which greatly influences their photosynthetic activity. Diatoms, dominated by Amphora sp., are abundant in the anoxic, sulfidic and essentially dark parts of the stromatolites. Although their origin in the stromatolites is unclear, they are possibly an important source of anaerobically degraded organic matter that induces in situ aragonite precipitation. To the best of our knowledge, this is so far the highest altitude with documented actively forming stromatolites. Their generally rich, diverse and to a large extent novel microbial community likely harbours valuable genetic and proteomic reserves, and thus deserves active protection. Furthermore, since the stromatolites flourish in an environment characterized by a multitude of extremes, including high exposure to UV radiation, they can be an excellent model system for studying microbial adaptations under conditions that, at least in part, resemble those during the early phase of life evolution on Earth.     

The spliceosome-associated protein Nrl1 suppresses homologous recombination-dependent R-loop formation in fission yeast

The formation of RNA–DNA hybrids, referred to as R-loops, can promote genome instability and cancer development. Yet the mechanisms by which R-loops compromise genome instability are poorly understood. Here, we establish roles for the evolutionarily conserved Nrl1 protein in pre-mRNA splicing regulation, R-loop suppression and in maintaining genome stability. nrl1Δ mutants exhibit endogenous DNA damage, are sensitive to exogenous DNA damage, and have defects in homologous recombination (HR) repair. Concomitantly, nrl1Δ cells display significant changes in gene expression, similar to those induced by DNA damage in wild-type cells. Further, we find that nrl1Δ cells accumulate high levels of R-loops, which co-localize with HR repair factors and require Rad51 and Rad52 for their formation. Together, our findings support a model in which R-loop accumulation and subsequent DNA damage sequesters HR factors, thereby compromising HR repair at endogenously or exogenously induced DNA damage sites, leading to genome instability.     

Hyperfractionated high-dose rate brachytherapy in the treatment of oral tongue cancer

Background

Low-dose rate brachytherapy is a well established treatment modality of oral cancer. Data about high-dose rate (HDR) brachytherapy are still sparse with various fractionation schedules and heterogeneous results.

Aim

The aim of our retrospective study was to evaluate the results of HDR brachytherapy with doses of 3 Gy twice daily.

Patients and methods

Twenty patients with squamous cell tongue cancer were treated in the years 2001–2009 by exclusive HDR BT 18 × 3 Gy twice daily. The plastic tube technique was used. Median follow up was 47 months (7.8–118) since brachytherapy.

Results

The local and locoregional control was 85% and 68%, respectively. Bone necrosis developed in one case treated without mandibular shielding and soft tissue necrosis in 2 cases.

Conclusion

It can be concluded that HDR brachytherapy with 18 × 3 Gy twice daily is safe with promising local control. The risk of nodal recurrences is substantial.