Reconstitution of the DNA base excision—repair pathway

Background: The base excision–repair pathway is the major cellular defence mechanism against spontaneous DNA damage. The enzymes involved have been highly conserved during evolution. Base excision–repair has been reproduced previously with crude cell-free extracts of bacterial or human origin. To further our understanding of base excision–repair, we have attempted to reconstitute the pathway in vitro using purified enzymes.Results We report here the successful reconstitution of the base excision–repair pathway with five purified enzymes from Escherichia coli: uracil-DNA glycosylase, a representative of the DNA glycosylases that remove various lesions from DNA; the AP endonuclease IV that specifically cleaves at abasic sites; RecJ protein which excises a 5′ terminal deoxyribose-phosphate residue; DNA polymerase I; and DNA ligase. The reaction proceeds with high efficiency in the absence of additional factors in the reconstituted system. Four of the enzymes are absolutely required for completion of the repair reaction. An unusual feature we have discovered is that the pathway branches after enzymatic incision at an abasic DNA site. RecJ protein is required for the major reaction, which involves replacement of only a single nucleotide at the damaged site; in its absence, an alternative pathway is observed, with generation of longer repair patches by the 5′ nuclease function of DNA polymerase I.Conclusion Repair of uracil in DNA is achieved by a very short-patch excision–repair process involving five different enzymes. No additional protein factors seem to be required. There is a minor, back-up pathway that uses replication factors to generate longer repair patches.     

Alginate/chitosan hydrogels as perspective transport systems for cefotaxime

This work reports synthesis of pH-responsive alginate/chitosan hydrogel spheres with the average diameter of 2.0 ± 0.05 mm, which contain cefotaxime that is an antibiotic of the cefalosporine group. The spheres provided the cefotaxime encapsulation efficiency of 95 ± 1%. An in vitro release of cefotaxime from the spheres in the media that simulate human biological fluids in peroral delivery conditions was found to be a pH-dependent process. The analysis of cefotaxime release kinetics by the Korsmeyer–Peppas model revealed a non-Fickian mechanism of its diffusion, which may be related to intermolecular interactions occurring between the antibiotic and chitosan. Conductometry, UV spectroscopy, and IR spectroscopy were used to study complexation of chitosan with cefotaxime in aqueous media with varied pH, characterize the composition of the complexes, and calculate their stability constants. The composition of the cefotaxime–chitosan complexes was found to correspond to the 1.0:4.0 and 1.0:2.0 molar ratios of the components at pH 2.0 and 5.6, respectively. Quantum chemical modeling was used to evaluate energy characteristics of chitosan–cefotaxime complexation considering the influence of a solvent.     

Isoelectric spectra of human serum albumin in healthy subjects and in ischemic heart disease

Isoelectric spectra of serum albumins isolated from blood of patients with heart ischemia were studied using isoelectric focusing in borate-polyolic systems in a polyacrylamide gel. In patients with heart ischemia the amount of fractions with pI 4.3-4.9 and 5.2-7.4 is found to increase with a simultaneous decrease in the fraction with pI 4.9-5.2 as compared with these indices in healthy people from the control group. Especially pronounced changes in isoelectrophoregrams were observed for blood albumins of patients with transmural myocardium infraction.     

Effect of ethanol and probenecid on the excretory function of the cerebral choroid plexus in rats

Probenecid at a dose 100 and 200 mg/kg, i.v. has been found to decrease in a dose-dependent manner the level of radioactivity of cerebrospinal fluid (CSF) measured at 1, 15, 30 and 60 min. after the intravenous injection of 14C-tyrosine, 14C-tryptophan and 14C-DOPA. Ethanol at a dose 2 and 4 g/kg, i. p. has not changed the level of radioactivity of the CSF. It is suggested that mentioned in the literature an increased accumulation of the labeled tyrosine, tryptophan and DOPA in the brain structures after their intravenous injection is not related to the inhibitory effect of ethanol on the excretory function of the choroid plexus of the brain. On the other hand, it is concluded that probenecid is able to inhibit the excretion from the brain of some acid compounds including tyrosine, tryptophan and DOPA.     

Molecular complexation of α-hederin with hederasaponin C

The molecular complexation of triterpene glycosides α-hederin (hederagenin 3-O-α-L-rhamnopyranosyl-(1 → 2)-O-α-L-arabinopyranoside) with hederasaponin C (hederagenin 3-O-α-L-rhamnopyranosyl-(1 → 2)-O-α-L-arabinopyranosyl-28-O-α-L-rhamnopyranosyl-(1 → 4)-O-β-D-glucopyranosyl-(1 → 6)-O-β-D-glucopyranoside) was investigated for the first time using the methods of IR- and electrospray ionization mass spectroscopy. The glycosides form a complex in the 1: 1 molar ratio. The influence of complex on Avena sativa seeds germination and its ichthyotoxicity against Poecilia reticulata were studied.     

The Impact of a Line Probe Assay Based Diagnostic Algorithm on Time to Treatment Initiation and Treatment Outcomes for Multidrug Resistant TB Patients in Arkhangelsk Region,Russia

BackgroundIn the Arkhangelsk region of Northern Russia, multidrug-resistant (MDR) tuberculosis (TB) rates in new cases are amongst the highest in the world. In 2014, MDR-TB rates reached 31.7% among new cases and 56.9% among retreatment cases. The development of new diagnostic tools allows for faster detection of both TB and MDR-TB and should lead to reduced transmission by earlier initiation of anti-TB therapy.MethodsA culture-based diagnostic algorithm used prior to LPA implementation was compared to an LPA-based algorithm that replaced BacTAlert and Löwenstein Jensen (LJ) for drug sensitivity testing. A total of 295 MDR-TB patients were included in the study, 163 diagnosed with the culture-based algorithm, 132 with the LPA-based algorithm.ResultsAmong smear positive patients, the implementation of the LPA-based algorithm was associated with a median decrease in time to MDR-TB treatment initiation of 50 and 66 days compared to the culture-based algorithm (BacTAlert and LJ respectively, p<0.001). In smear negative patients, the LPA-based algorithm was associated with a median decrease in time to MDR-TB treatment initiation of 78 days when compared to the culture-based algorithm (LJ, p<0.001). However, several weeks were still needed for treatment initiation in LPA-based algorithm, 24 days in smear positive, and 62 days in smear negative patients. Overall treatment outcomes were better in LPA-based algorithm compared to culture-based algorithm (p = 0.003). Treatment success rates at 20 months of treatment were higher in patients diagnosed with the LPA-based algorithm (65.2%) as compared to those diagnosed with the culture-based algorithm (44.8%). Mortality was also lower in the LPA-based algorithm group (7.6%) compared to the culture-based algorithm group (15.9%). There was no statistically significant difference in smear and culture conversion rates between the two algorithms.ConclusionThe results of the study suggest that the introduction of LPA leads to faster time to MDR diagnosis and earlier treatment initiation as well as better treatment outcomes for patients with MDR-TB. These findings also highlight the need for further improvements within the health system to reduce both patient and diagnostic delays to truly optimize the impact of new, rapid diagnostics.     

Fauna of bumblebees (Hymenoptera: Apidae: Bombus Latreille) in the mainland part of Arkhangelsk Region,NW Russia

The focus of this study is to present bumblebee fauna of Arkhangelsk Region (north-western Russia). This research is based on the museum collections and materials collected by the authors. Collecting localities and data of faunistic records are given in the species list. We include 34 species in the fauna of bumblebees of Arkhangelsk Region. The regional fauna is dominated by Transpalaearctic species. Bumblebee fauna in the study region has low specificity. The recent distribution of bumblebee species in the study region is a result of post-glacial immigration.     

Novel protein from larval sponge cells,ilborin, is related to energy turnover and calcium binding and is conserved among marine invertebrates

Sponges (phylum Porifera) are early-branching animals, whose outwardly simple body plan is underlain by a complex genetic repertoire. The transition from a mobile larva to an attached filter-feeding organism occurs by metamorphosis, a process accompanied by a radical change of the body plan and cell transdifferentiation. The continuity between larval cells and adult tissues is still obscure. In a previous study, we have produced polyclonal antibodies against the major protein of the flagellated cells covering the larva of the sponge Halisarca dujardini, used them to trace the fate of these cells and shown that the larval flagellated cells transdifferentiate into the choanocytes. In the present work, we identified the sequence of this novel protein, which we named ilborin. A search in the open databases showed that multiple orthologues of the newly identified protein are present in sponges, cnidarians, flatworms, ctenophores and echinoderms, but none of them has been described yet. Ilborin has two conserved domains: triosephosphate isomerase-barrel, which has enzymatic activity against macroergic compounds, and canonical EF-hand, which binds calcium. mRNA of ilborin is expressed in the larval flagellated cells. We suggest that the new protein is involved in the calcium-mediated regulation of energy metabolism, whose activation precedes metamorphosis.