New family of regulators in the environmental signaling pathway which activates the general stress transcription factor sigma(B) of Bacillus subtilis

Expression of the general stress regulon of Bacillus subtilis is controlled by the alternative transcription factor sigma(B), which is activated when cells encounter growth-limiting energy or environmental stresses. The RsbT serine-threonine kinase is required to convey environmental stress signals to sigma(B), and this kinase activity is magnified in vitro by the RsbR protein, a positive regulator important for full in vivo response to salt or heat stress. Previous genetic analysis suggested that RsbR function is redundant with other unidentified regulators. A search of the translated B. subtilis genome found six paralogous proteins with significant similarity to RsbR: YetI, YezB, YkoB, YojH, YqhA, and YtvA. Their possible regulatory roles were investigated using three different approaches. First, genetic analysis found that null mutations in four of the six paralogous genes have marked effects on the sigma(B) environmental signaling pathway, either singly or in combination. The two exceptions were yetI and yezB, adjacent genes which appear to encode a split paralog. Second, biochemical analysis found that YkoB, YojH, and YqhA are specifically phosphorylated in vitro by the RsbT environmental signaling kinase, as had been previously shown for RsbR, which is phosphorylated on two threonine residues in its C-terminal region. Both residues are conserved in the three phosphorylated paralogs but are absent in the ones that were not substrates of RsbT: YetI and YezB, each of which bears only one of the conserved residues; and YtvA, which lacks both residues and instead possesses an N-terminal PAS domain. Third, analysis in the yeast two-hybrid system suggested that all six paralogs interact with each other and with the RsbR and RsbS environmental regulators. Our data indicate that (i) RsbR, YkoB, YojH, YqhA, and YtvA function in the environmental stress signaling pathway; (ii) YtvA acts as a positive regulator; and (iii) RsbR, YkoB, YojH, and YqhA collectively act as potent negative regulators whose loss increases sigma(B) activity more than 400-fold in unstressed cells.

iACP-GAEnsC: Evolutionary genetic algorithm based ensemble classification of anticancer peptides by utilizing hybrid feature space

Cancer is a fatal disease, responsible for one-quarter of all deaths in developed countries. Traditional anticancer therapies such as, chemotherapy and radiation, are highly expensive, susceptible to errors and ineffective techniques. These conventional techniques induce severe side-effects on human cells. Due to perilous impact of cancer, the development of an accurate and highly efficient intelligent computational model is desirable for identification of anticancer peptides. In this paper, evolutionary intelligent genetic algorithm-based ensemble model, 'iACP-GAEnsC', is proposed for the identification of anticancer peptides. In this model, the protein sequences are formulated, using three different discrete feature representation methods, i.e., amphiphilic Pseudo amino acid composition, g-Gap dipeptide composition, and Reduce amino acid alphabet composition. The performance of the extracted feature spaces are investigated separately and then merged to exhibit the significance of hybridization. In addition, the predicted results of individual classifiers are combined together, using optimized genetic algorithm and simple majority technique in order to enhance the true classification rate. It is observed that genetic algorithm-based ensemble classification outperforms than individual classifiers as well as simple majority voting base ensemble. The performance of genetic algorithm-based ensemble classification is highly reported on hybrid feature space, with an accuracy of 96.45%. In comparison to the existing techniques, 'iACP-GAEnsC' model has achieved remarkable improvement in terms of various performance metrics. Based on the simulation results, it is observed that 'iACP-GAEnsC' model might be a leading tool in the field of drug design and proteomics for researchers.

Homologous pairs of regulatory proteins control activity of Bacillus subtilis transcription factor sigma(b) in response to environmental stress

In Bacillus subtilis, activity of the general stress transcription factor sigma B is controlled posttranslationally by a regulatory network that transmits signals of environmental and metabolic stress. These signals include heat, ethanol, or osmotic challenge, or a sharp decrease in cellular energy levels, and all ultimately control sigma B activity by influencing the binding decision of the RsbW anti-sigma factor. In the absence of stress, RsbW binds to sigma B and prevents its association with RNA polymerase core enzyme. However, following stress, RsbW binds instead to the RsbV anti-anti-sigma factor, thereby releasing sigma B to direct transcription of its target genes. These two principal regulators of sigmaB activity are encoded in the eight-gene sigB operon, which has the gene order rsbR-rsbS-rsbT-rsbU-rsbV-rsbW-sig B-rsbX (where rsb stands for regulator of sigma B). Notably, the predicted rsbS product has significant amino acid identity to the RsbV anti-anti-sigma factor and the predicted rsbT product resembles the RsbW anti-sigma factor. To determine the roles of rsbS and rsbT, null or missense mutations were constructed in the chromosomal copies or each and tested for their effects on expression of a sigma B-dependent reporter fusion. On the basis of this genetic analysis, our principal conclusions are that (i) the rsbS product is a negative regulator of or" activity, (ii) the rsbT product is a positive regulator, (iii) RsbS requires RsbT for function, and (iv) the RsbS-RsbT and RsbV-RsbW pairs act hierarchically by a common mechanism in which key protein-protein interactions are controlled by phosphorylation events.

Cold preservation of fatty liver grafts: prevention of functional and ultrastructural impairments by venous oxygen persufflation

BACKGROUND/AIMS

The incidence of steatosis in livers retrieved for organ transplantation is up to 30%. Due to the shortage of donor organs, many of these livers are accepted for clinical transplantation, although a high rate of graft dysfunction is associated with ischemic preservation of steatotic livers. The present study was intended to reduce the ischemia/reperfusion injury of steatotic grafts by the use of venous systemic oxygen persufflation during cold storage.

METHODS

A histologically-documented mild to moderate steatosis was induced in livers of Wistar rats by fasting for 2 days and subsequent feeding of a fat-free diet enriched in carbohydrates. Fatty livers were retrieved and flushed via the portal vein with 60 ml of HTK. In group A, livers were then stored ischemically at 4 degrees C for 24 h. Livers of group B were additionally connected to a gaseous oxygen supply and persufflated with O2 via the venous vascular system during the cold storage period. Viability of the livers was then assessed upon isolated perfusion in vitro with oxygenated Krebs-Henseleit buffer.

RESULTS

Venous systemic oxygen sufflation resulted in a relevant and significant reduction of parenchymal (ALT: 132+/-90 vs 434+/-172 U/l; p<0.01) and mitochondrial (GLDH: 116+/-57 vs 633+/-241 U/l; p<0.001) enzyme release during reperfusion. Moreover, Kupffer cell activation, as evaluated from acid phosphatase activity in the perfusate, was reduced to about 1/3 (4.0+/-1.3 vs 11.9+/-5.3 U/l; p<0.01). Electron microscopic analysis revealed that the liver mitochondria and sinusoidal endothelial lining were better preserved after oxygen persufflation, which was in line with the data on enzyme release and the increased portal perfusion pressure in the untreated group, while normal values were found after venous systemic oxygen sufflation.

CONCLUSION

Venous oxygen persufflation may thus represent a useful tool for the safe and improved preservation of ischemia-sensitive steatotic livers.

iMethyl-STTNC: Identification of N6-methyladenosine sites by extending the idea of SAAC into Chou's PseAAC to formulate RNA sequences

N⁶- methyladenosine (m⁶A) is a vital post-transcriptional modification, which adds another layer of epigenetic regulation at RNA level. It chemically modifies mRNA that effects protein expression. RNA sequence contains many genetic code motifs (GAC). Among these codes, identification of methylated or not methylated GAC motif is highly indispensable. However, with a large number of RNA sequences generated in post-genomic era, it becomes a challenging task how to accurately and speedily characterize these sequences. In view of this, the concept of an intelligent is incorporated with a computational model that truly and fast reflects the motif of the desired classes. An intelligent computational model "iMethyl-STTNC" model is proposed for identification of methyladenosine sites in RNA. In the proposed study, four feature extraction techniques, such as; Pseudo-dinucleotide-composition, Pseudo-trinucleotide-composition, split-trinucleotide-composition, and split-tetra-nucleotides-composition (STTNC) are utilized for genuine numerical descriptors. Three different classification algorithms including probabilistic neural network, Support vector machine (SVM), and K-nearest neighbor are adopted for prediction. After examining the outcomes of prediction model on each feature spaces, SVM using STTNC feature space reported the highest accuracy of 69.84%, 91.84% on dataset1 and dataset2, respectively. The reported results show that our proposed predictor has achieved encouraging results compared to the present approaches, so far in the research. It is finally reckoned that our developed model might be beneficial for in-depth analysis of genomes and drug development.

Modulator protein RsbR regulates environmental signalling in the general stress pathway of Bacillus subtilis

Bacillus subtilis responds to signals of environmental and metabolic stress by inducing over 40 general stress genes under the control of the sigma B transcription factor. sigma B activity is regulated post-translationally by a multi-component network composed of two coupled partner-switching modules, RsbX-RsbS-RsbT and RsbU-RsbV-RsbW, each containing a serine phosphatase (X or U), an antagonist protein (S or V), and a switch protein/serine kinase (T or W). The upstream module (X-S-T) is required to transmit signals of environmental stress. In contrast, the downstream module (U-V-W) is required to transmit signals of energy stress as well as the environmental signals conveyed to it from the upstream module. Until now the function of the rsbR gene product was unknown. RsbR shares significant sequence similarity with the RsbS and RsbV antagonist proteins whose phosphorylation states control key protein-protein interactions within their respective modules. Here we present evidence that RsbR is associated with RsbS in the upstream, environmental-sensing module. To investigate RsbR function, we constructed deletion and point mutations within rsbR and tested their effects on expression of sigma B-dependent reporter fusions, both singly and in combination with other rsb mutations. To determine the possible interaction of RsbR with other Rsb proteins, we tested the ability of wild-type or mutant RsbR to activate transcription in the yeast two-hybrid system in conjunction with other Rsb regulators. On the basis of this genetic analysis, we conclude that RsbR is a positive regulator which modulates sigma B activity in response to salt and heat stress. Our data further suggest that: (i) RsbR influences the antagonist function of RsbS by direct protein-protein interaction; and (ii) this interaction with RsbS is likely controlled by the phosphorylation state of RsbR.

Fibrinolytic preflush upon liver retrieval from non-heart beating donors to enhance postpreservation viability and energetic recovery upon reperfusion

BACKGROUND

Our objective was to evaluate graft equilibration with high viscosity (University of Wisconsin solution [UW]) or low viscosity (Bretschneider's histidine-tryptophan-ketoglutarate [HTK]) during liver procurement from non-heart beating donors (NHBD) and the potential impact of a preceding fibrinolysis with streptokinase on postpreservation viability.

METHODS

After 60 min of cardiac arrest, rat livers were perfused by gravity (60 cm H2O) via the portal vein with either 60 ml of HTK, 20 ml of UW, or 20 ml of Ringer's solution (22 degrees C including 7500U of streptokinase) and, subsequently, 20 ml of UW. After 24 h of storage at 4 degrees C, viability of the livers was assessed upon isolated reperfusion in vitro.

RESULTS

Magnetic resonance imaging revealed severe perfusion deficits, which were mildly attenuated with HTK, upon flush-out with UW. After preflush with streptokinase, a mostly homogenous distribution of the preservation solution was observed throughout the liver tissue. The choice of the flush-out solution (UW or HTK) had no influence on parenchymal enzyme leakage, hepatic bile production, or tissue levels of ATP after reperfusion of the livers. Fibrinolytic preflush, however, resulted in a relevant and significant improvement of structural integrity as well as functional and metabolic recovery.

CONCLUSIONS

Compromised vascular tissue perfusion upon organ harvest in NHBD triggers graft dysfunction after cold storage and can easily be circumvented by temporary fibrinolysis before graft retrieval.

DP-BINDER: machine learning model for prediction of DNA-binding proteins by fusing evolutionary and physicochemical information

DNA-binding proteins (DBPs) participate in various biological processes including DNA replication, recombination, and repair. In the human genome, about 6-7% of these proteins are utilized for genes encoding. DBPs shape the DNA into a compact structure known chromatin while some of these proteins regulate the chromosome packaging and transcription process. In the pharmaceutical industry, DBPs are used as a key component of antibiotics, steroids, and cancer drugs. These proteins also involve in biophysical, biological, and biochemical studies of DNA. Due to the crucial role in various biological activities, identification of DBPs is a hot issue in protein science. A series of experimental and computational methods have been proposed, however, some methods didn't achieve the desired results while some are inadequate in its accuracy and authenticity. Still, it is highly desired to present more intelligent computational predictors. In this work, we introduce an innovative computational method namely DP-BINDER based on physicochemical and evolutionary information. We captured local highly decisive features from physicochemical properties of primary protein sequences via normalized Moreau-Broto autocorrelation (NMBAC) and evolutionary information by position specific scoring matrix-transition probability composition (PSSM-TPC) and pseudo-position specific scoring matrix (PsePSSM) using training and independent datasets. The optimal features were selected by the support vector machine-recursive feature elimination and correlation bias reduction (SVM-RFE + CBR) from fused features and were fed into random forest (RF) and support vector machine (SVM). Our method attained 92.46% and 89.58% accuracy with jackknife and ten-fold cross-validation, respectively on the training dataset, while 81.17% accuracy on the independent dataset for prediction of DBPs. These results demonstrate that our method attained the highest success rate in the literature. The superiority of DP-BINDER over existing approaches due to several reasons including abstraction of local dominant features via effective feature descriptors, utilization of appropriate feature selection algorithms and effective classifier.

Electrochemical determination of folic acid: A short review

Folic acid (FA) is an electroactive compound of biological origin. It helps our body to produce and maintain healthy cells. It can significantly reduce the occurrence of neural tube defects and also prevents change in DNA structure. FA deficiency can lead to various health risks. Therefore, a sensitive, specific, and reproducible way of FA detection is essential. A number of analytical methods are in practice for the quantification of FA. However, electroanalytical methods are attracting much attention because of their advantage over conventional methods, as they are fast, simple, sensitive, and cost effective. Moreover, modification of electrodes offers control over size and morphology which allows miniaturization for applicability in portable electrochemical devices.

iAtbP-Hyb-EnC: Prediction of antitubercular peptides via heterogeneous feature representation and genetic algorithm based ensemble learning model

Tuberculosis (TB) is a worldwide illness caused by the bacteria Mycobacterium tuberculosis. Owing to the high prevalence of multidrug-resistant tuberculosis, numerous traditional strategies for developing novel alternative therapies have been presented. The effectiveness and dependability of these procedures are not always consistent. Peptide-based therapy has recently been regarded as a preferable alternative due to its excellent selectivity in targeting specific cells without affecting the normal cells. However, due to the rapid growth of the peptide samples, predicting TB accurately has become a challenging task. To effectively identify antitubercular peptides, an intelligent and reliable prediction model is indispensable. An ensemble learning approach was used in this study to improve expected results by compensating for the shortcomings of individual classification algorithms. Initially, three distinct representation approaches were used to formulate the training samples: k-space amino acid composition, composite physiochemical properties, and one-hot encoding. The feature vectors of the applied feature extraction methods are then combined to generate a heterogeneous vector. Finally, utilizing individual and heterogeneous vectors, five distinct nature classification models were used to evaluate prediction rates. In addition, a genetic algorithm-based ensemble model was used to improve the suggested model's prediction and training capabilities. Using Training and independent datasets, the proposed ensemble model achieved an accuracy of 94.47% and 92.68%, respectively. It was observed that our proposed "iAtbP-Hyb-EnC" model outperformed and reported ~10% highest training accuracy than existing predictors. The "iAtbP-Hyb-EnC" model is suggested to be a reliable tool for scientists and might play a valuable role in academic research and drug discovery. The source code and all datasets are publicly available at https://github.com/Farman335/iAtbP-Hyb-EnC.

AFP-CMBPred: Computational identification of antifreeze proteins by extending consensus sequences into multi-blocks evolutionary information

In extremely cold environments, living organisms like plants, animals, fishes, and microbes can die due to the intracellular ice formation in their bodies. To sustain life in such cold environments, some cold-blooded species produced Antifreeze proteins (AFPs), also called ice-binding proteins. AFPs are not only limited to the medical field but also have diverse significance in the area of biotechnology, agriculture, and the food industry. Different AFPs exhibit high heterogeneity in their structures and sequences. Keeping the significance of AFPs, several machine-learning-based models have been developed by scientists for the prediction of AFPs. However, due to the complex and diverse nature of AFPs, the prediction performance of the existing methods is limited. Therefore, it is highly indispensable for researchers to develop a reliable computational model that can accurately predict AFPs. In this connection, this study presents a novel predictor for AFPs, named AFP-CMBPred. The sequences of AFPs are formulated via four different feature representation methods, such as Amphiphilic pseudo amino acid composition (Amp-PseAAC), Dipeptide Deviation from Expected Mean (DDE), Multi-Blocks Position Specific Scoring Matrix (MB-PSSM), and Consensus Sequence-based on Multi-Blocks Position Specific Scoring Matrix (CS-MB-PSSM) to collect local and global descriptors. In the next step, the extracted feature vectors are evaluated via Support Vector Machine (SVM) and Random Forest (RF) based classification learners. The prediction performance of both classifiers is further assessed using three validation methods i.e., jackknife test, 10-fold cross-validation test, and independent test. After examining the prediction rates of all validation tests, it was found that our proposed model achieved the higher prediction accuracies of ∼2.65%, ∼2.84%, and ∼3.37% using jackknife, K-fold, and independent test, respectively. The experimental outcomes validate that our proposed "AFP-CMBPred" predictor secured the highest prediction results than the existing models for the identification of AFPs. It is further anticipated that our proposed AFP-CMBPred model will be considered a valuable tool in the research academia and drug development.

AIPs-SnTCN: Predicting Anti-Inflammatory Peptides Using fastText and Transformer Encoder-Based Hybrid Word Embedding with Self-Normalized Temporal Convolutional Networks

Inflammation is a biologically resistant response to harmful stimuli, such as infection, damaged cells, toxic chemicals, or tissue injuries. Its purpose is to eradicate pathogenic micro-organisms or irritants and facilitate tissue repair. Prolonged inflammation can result in chronic inflammatory diseases. However, wet-laboratory-based treatments are costly and time-consuming and may have adverse side effects on normal cells. In the past decade, peptide therapeutics have gained significant attention due to their high specificity in targeting affected cells without affecting healthy cells. Motivated by the significance of peptide-based therapies, we developed a highly discriminative prediction model called AIPs-SnTCN to predict anti-inflammatory peptides accurately. The peptide samples are encoded using word embedding techniques such as skip-gram and attention-based bidirectional encoder representation using a transformer (BERT). The conjoint triad feature (CTF) also collects structure-based cluster profile features. The fused vector of word embedding and sequential features is formed to compensate for the limitations of single encoding methods. Support vector machine-based recursive feature elimination (SVM-RFE) is applied to choose the ranking-based optimal space. The optimized feature space is trained by using an improved self-normalized temporal convolutional network (SnTCN). The AIPs-SnTCN model achieved a predictive accuracy of 95.86% and an AUC of 0.97 by using training samples. In the case of the alternate training data set, our model obtained an accuracy of 92.04% and an AUC of 0.96. The proposed AIPs-SnTCN model outperformed existing models with an ∼19% higher accuracy and an ∼14% higher AUC value. The reliability and efficacy of our AIPs-SnTCN model make it a valuable tool for scientists and may play a beneficial role in pharmaceutical design and research academia.

Outpatient management of deep vein thrombosis

OBJECTIVE

To assess whether patients with deep vein thrombosis (DVT) could be satisfactorily treated on an outpatient basis with low molecular weight (LMW) heparin and warfarin.

DESIGN

A 22 month prospective study of adults attending St Peter's Hospital accident and emergency department with DVT.

RESULTS

1093 patients were referred and assessed; 160 were venogram positive, of which 159 patients between the ages of 22 and 89 years of age have now been treated with LMW heparin as outpatients. Direct liaison with community nurses has minimised the impact on general practitioner workload.

CONCLUSIONS

1272 bed days were saved during this period (an estimated 320,000 pounds). The outpatient treatment of thromboembolism has been shown to be effective and safe.

Experimental liver preservation with Celsior: a novel alternative to University of Wisconsin and histidine-tryptophan-alpha-ketoglutarate solutions?

Celsior, a low viscosity and low potassium preservation solution, has recently been tested successfully in the cold preservation of heart, lung, kidney and small intestine. The purpose of the present study was to evaluate the potential of Celsior in the cold preservation of the liver. Livers were harvested from male Wistar rats and then flushed with either Celsior (CE), University of Wisconsin solution (UW) or histidine-tryptophan-alpha-ketoglutarate solution (HTK) and stored for 24 h at 4 degrees C in the respective solution. The reperfusion was performed in vitro using a recirculating model with oxygenated (95% O(2), 5% CO(2)) Krebs-Henseleit buffer at 37 degrees C. To simulate the slow rewarming during the surgical implantation in vivo, all livers were stored for 30 min at room temperature prior to reperfusion. After ischemic storage and also after reperfusion some samples were freeze-clamped for analysis of tissue metabolites while others were tested for structural and functional integrity by the isolated perfusion. CE vs. UW vs. HTK: Metabolic preservation of tissue ATP (micromol/g dry weight) during cold storage was best with Celsior (0. 46 +/- 0.17 vs. 0.26 +/- 0.03 vs. 0.35 +/- 0.07; p < 0.05 CE vs. UW), but upon reperfusion energetic recovery was comparable in the three groups (3.45 +/- 0.66 vs. 4.27 +/- 0.41 vs. 3.63 +/- 0.64 micromol/g/dry weight). There appeared to be structural integrity during reoxygenation irrespective of the used preservation solution with comparable values of parenchymal enzyme release (ALT: 575 +/- 82 vs. 547 +/- 106 vs. 593 +/- 38 mU/g/l), bile production (18.0 +/- 1.0 vs. 18.5 +/- 2.5 vs. 18.7 +/- 1.4 microl/g/ min), and the release of acid phosphatase, an indicator for activated Kupffer cells (89 +/- 13 vs. 90 +/- 5 vs. 123 +/- 21 mU/g/l) in this in vitro model. Vascular flow characteristics were approximated by the portal perfusion pressure, which tended to be elevated upon initial reperfusion in the UW group (8.4 +/- 0.6 mm Hg) compared to 6.6 +/- 1.0 and 7.3 +/- 0.4 mm Hg in Celsior and HTK, respectively. However, the pressure values decreased to the normal range even in the UW group with ongoing perfusion. The sensitivity of our model in detecting protective effects of the tested solution was confirmed by a negative control group of livers stored in Ringer's solution at 4 degrees C, yielding an impaired recovery which differed by one magnitude from the three other groups. Within the limits of an in vitro study it is concluded from these results that Celsior may become a suitable alternative for liver preservation and further studies including a transplantation in vivo are strongly encouraged.

Isolation and characterization of csbB, a gene controlled by Bacillus subtilis general stress transcription factor sigma B

In the bacterium Bacillus subtilis (Bs), the alternative transcription factor sigma B is activated by environmental stresses to control the expression of a large set of unlinked genes. However, the range of physiological functions mediated by these sigma B-controlled genes is presently unknown. We report here that the newly identified gene csbB is under the dual control of a sigma B-dependent and a sigma B-independent promoter. The predicted product of csbB is a 329 residue protein containing two potential membrane-spanning segments in its C-terminal region, leading us to speculate that one class of sigma B-controlled genes acts to modify the cell envelope as part of the general stress response.

Enhancement of endogenous cyclic AMP signal: a new approach to allow for cold preservation of rat livers from non-heart-beating donors?

BACKGROUND

The organ donor shortage has led to a reconsideration of the use of non-heart-beating donors (NHBDs). However, graft injury due to warm ischemia in NHBD livers strongly affects posttransplant outcome. The present study was aimed at investigating the role of the cellular cyclic (c)AMP second messenger signal with regard to hepatic viability after cold preservation of NHBD livers.

METHODS

Cardiac arrest was induced in Wistar rats by frenotomy of the anesthetized nonheparinized animal. After 30 min, the livers were excised and flushed with 20 ml of heparinized saline solution, rinsed with 10 ml of University of Wisconsin (UW) solution, and stored submerged in UW solution at 4 degrees C for 24 hr. In half of the experiments, UW solution was supplemented with glucagon (0.5 microg/ml) to increase the cAMP signal in the liver. Reperfusion was carried out in vitro after all livers were incubated at 25 degrees C in saline solution to replicate the period of slow rewarming during surgical implantation in vivo.

RESULTS

Hepatic levels of cAMP (nmol/g dry weight) declined from 1.21+/-0.05 to 0.53+/-0.03 (P<0.01) at 30 min after cardiac arrest. Subsequent storage in UW solution resulted in a further decline to 0.35+/-0.04 after 24 hr in group A, whereas glucagon treatment enhanced cellular cAMP signal to 0.64+/-0.06 (P<0.01). Upon reperfusion, liver integrity was significantly improved after glucagon administration, with 66% reduction in alanine aminotransferase release and a threefold increase in hepatic bile production as compared with untreated livers. Moreover, liver ATP tissue levels were restored to only 2.19+/-0.51 micromol/g in the untreated group but reached 4.97+/-0.41 micromol/g (P<0.05) after treatment with glucagon.

CONCLUSIONS

Posthoc conditioning of predamaged livers by glucagon enhances cAMP tissue levels during ischemic preservation and improves hepatic integrity upon reperfusion. This may represent a promising approach for the use of livers from non-heart-beating donors in clinical transplantation.

Significance and molecular targets of protein kinase A during cAMP-mediated protection of cold stored liver grafts

The use of marginal donor livers is followed by a higher frequency of primary dys- or nonfunction after transplantation. The present study was designed to test the hypothesis that stimulation of the cAMP second-messenger signal pathway might protect the liver from ischemic injury, laying emphasis on the role of protein kinase A-mediated signal transduction. Rat livers were harvested after 45 min of cardiac arrest and preserved in HTK solution for 24 h. Hepatic integrity was assessed thereafter using a blood-free reperfusion model. Supplementation of the preservation solution with dibutyryl-cAMP (db-cAMP) promoted phosphorylation of BAD at Ser 112 and concomitantly mitigated mitochondrial release of cytochrome c into the cytosol. Apoptotic cell transformation was evident in reperfused livers by positive TUNEL-staining of sinusoidal lining cells and the detection of cleaved poly(ADP-ribose) polymerase (PARP) in tissue homogenates by western analysis. Treatment with db-cAMP was effective in minimizing both TUNEL staining and PARP cleavage and significantly reduced postischemic enzyme leakage of alanine aminotransferase to one half, while hepatic bile production was enhanced by approximately 60% when compared to untreated livers. This functional improvement was accompanied by a net amelioration of portal vascular conductivity. Inhibition of A kinase-anchoring protein with HT31 completely reversed any of the observed effects obtained by db-cAMP. We conclude that enhancement of cellular cAMP signal maintains hepatic integrity during and after ischemic preservation which may be attributed to protein kinase A dependent phosphorylation of BAD in line with subsequent inhibition of mitochondria-initiated apoptosis of sinusoidal lining cells.

Laparoscopic Excision of Retroperitoneal Schwannoma

Schwannomas are tumours that arise from the myelin sheath of the nerves. A very unusual location for schwannoma is the retro peritoneal areas (less than 2%). We present herewith a patient who had a 4x5cm Schwannoma arising from the nerve root of L2 on the right side, which presented as a lump in the psoas major muscle. This was treated by total laparoscopic excision after splitting open the psoas major. In the published english medical literature we could find only 16 cases of laparoscopic resection of retroperitoneal schwannoma and we believe ours to be the first case that was done through a psoas muscle split technique. Technical and histopathological details are discussed elaborately in this article.

Defect ferromagnetism induced by lower valence cation doping: Li-doped SnO2 nanoparticles

To explore the role of Li in establishing room-temperature ferromagnetism in SnO₂, the structural, electronic and magnetic properties of Li-doped SnO₂ compounds were studied for different size regimes, from nanoparticles to bulk crystals. Li-doped nanoparticles show ferromagnetic ordering plus a paramagnetic contribution for particle sizes in the range of 16-51 nm, while pure SnO₂ and Li-doped compounds below and above this particular size range are diamagnetic. The magnetic moment is larger for compositions where the Li substitutes for Sn than for compositions where Li prevalently occupies interstitial sites. The observed ferromagnetic ordering in Li-doped SnO₂ nanoparticles is mainly due to the holes created when Li substitutes at a Sn site. Conversely, Li acts as an electron donor and electrons from Li may combine with holes to decrease ferromagnetism when lithium mainly occupies interstitial sites in the SnO₂ lattice.

Cellular accumulation of Cys326-OGG1 protein complexes under conditions of oxidative stress

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Novel use of BiFC to study a component of base excision repair pathway.

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First time that OGG1 complex formation has been observed inside of cells.

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Complexes restricted to the Cys326 variant and conditions of oxidative stress.

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Evidence supports role of OGG1 dimer formation in reduced repair capacity.

The common Ser326Cys polymorphism in the base excision repair protein 8-oxoguanine glycosylase 1 is associated with a reduced capacity to repair oxidative DNA damage particularly under conditions of intracellular oxidative stress and there is evidence that Cys326-OGG1 homozygous individuals have increased susceptibility to specific cancer types. Indirect biochemical studies have shown that reduced repair capacity is related to OGG1 redox modification and also possibly OGG1 dimer formation. In the current study we have used bimolecular fluorescence complementation to study for the first time a component of the base excision repair pathway and applied it to visualise accumulation of Cys326-OGG1 protein complexes in the native cellular environment. Fluorescence was observed both within and around the cell nucleus, was shown to be specific to cells expressing Cys326-OGG1 and only occurred in cells under conditions of cellular oxidative stress following depletion of intracellular glutathione levels by treatment with buthionine sulphoximine. Furthermore, OGG1 complex formation was inhibited by incubation of cells with the thiol reducing agents β-mercaptoethanol and dithiothreitol and the antioxidant dimethylsulfoxide indicating a causative role for oxidative stress in the formation of OGG1 cellular complexes.

In conclusion, this study has provided for the first time evidence of redox sensitive Cys326-OGG1 protein accumulation in cells under conditions of intracellular oxidative stress that may be related to the previously reported reduced repair capacity of Cys326-OGG1 specifically under conditions of oxidative stress.