Cloning of murine transformed cell lines in suspension culture with efficiencies near 100%

Addition of 3 × 10⁶ thymus cells from either syngeneic, allogeneic or xenogeneic animals increases the cloning efficiencies of murine thymomas (EL-4, WC-2), B-lymphomas (McPC 1748, 38C-13), Abelson-virus transformed cell lines (F and K), mastocytomas (P815), myelomas (AbPC22, X63-AG8, 5563, MOPC 104 E, RFC 5, W 3469) and hybrids of myelomas and normal B-lymphocytes (Sp-1), all adapted to tissue culture, to near 100%. Thymus cells also increase the efficiencies of growth initiation in primary in vitro cultures of myeloma tumor cells (S117) transplanted in vivo, and of cells fused between the azaguanine-resistant X63-AG8 myeloma cell line and normal, LPS-stimulated B-lymphocyte blasts.     

The Impact of Hepatitis A Virus Infection on Hepatitis C Virus Infection: A Competitive Exclusion Hypothesis

We address the observation that, in some cases, patients infected with the hepatitis C virus (HCV) are cleared of HCV when super-infected with the hepatitis A virus (HAV). We hypothesise that this phenomenon can be explained by the competitive exclusion principle, including the action of the immune system, and show that the inclusion of the immune system explains both the elimination of one virus and the co-existence of both infections for a certain range of parameters. We discuss the potential clinical implications of our findings.     

Trial-by-trial changes in a priori informational value of external cues and subjective expectancies in human auditory attention

Background

Preparatory activity based on a priori probabilities generated in previous trials and subjective expectancies would produce an attentional bias. However, preparation can be correct (valid) or incorrect (invalid) depending on the actual target stimulus. The alternation effect refers to the subjective expectancy that a target will not be repeated in the same position, causing RTs to increase if the target location is repeated. The present experiment, using the Posner''s central cue paradigm, tries to demonstrate that not only the credibility of the cue, but also the expectancy about the next position of the target are changedin a trial by trial basis. Sequences of trials were analyzed.

Results

The results indicated an increase in RT benefits when sequences of two and three valid trials occurred. The analysis of errors indicated an increase in anticipatory behavior which grows as the number of valid trials is increased. On the other hand, there was also an RT benefit when a trial was preceded by trials in which the position of the target changed with respect to the current trial (alternation effect). Sequences of two alternations or two repetitions were faster than sequences of trials in which a pattern of repetition or alternation is broken.

Conclusions

Taken together, these results suggest that in Posner''s central cue paradigm, and with regard to the anticipatory activity, the credibility of the external cue and of the endogenously anticipated patterns of target location are constantly updated. The results suggest that Bayesian rules are operating in the generation of anticipatory activity as a function of the previous trial''s outcome, but also on biases or prior beliefs like the “gambler fallacy”.     

Environmental factors affecting chemical variability of essential oils in Thymus piperella L.

Environmental factors affecting essential oils variability in Thymus piperella L. are studied. The relationship between the bioclimatics index and edaphic factors with three chemotypes is determined through the application of multivariate analysis (CANOCO) and other statistical processes to both ecological and the essential oil data set components. Chemotype p-cymene γ-terpinene carvacrol shows a positive relationship with the aridity index (I_a) and Altitude. The p-cymene thymol chemotype is related to factors affecting water balance in both the soils and plants. The influence of climatic factors over p-cymene carvacrol is less evident. The compound p-cymene, common to the three chemical groups and the most abundant of all, presents positive correlation with the organic matter in the soil.     

A systematic investigation of multiheme c-type cytochromes in prokaryotes

Multiheme c-type cytochromes (MHCs) are metalloproteins that can play various biochemical roles, including enzymatic activity and electron transfer. As electron transfer proteins, the presence of multiple heme cofactors in the vicinity allows electrons to rapidly travel relatively long distances. MHCs are often characterized by relatively low structural complexity, with the heme cofactors being largely responsible for maintaining the structure in place, owing to the protein–heme covalent linkages. In this work, we analyzed an extensive ensemble of 594 complete prokaryotic proteomes, amounting to more than 1.9 million sequences, to characterize their content in MHCs. We identified 1,659 MHCs in 258 organisms. The presence of MHCs was found to correlate quite well with the capability of an organism to synthesize or take up heme. For two organisms, the presence of MHCs in the proteome could be taken as a hint to the presence of divergent heme uptake pathways. The most common numbers of heme-binding motifs in a sequence were four (25%) and two (23%), followed by five (13%) and ten (9.8%). The average protein-to-heme ratio was relatively similar for all MHCs, except diheme proteins, regardless of the number of motifs at around 60 ± 30. The latter ratio could in favorable cases be a useful indicator for functional assignments of novel MHCs. Finally, we showed that the amount of structural information currently available for MHCs is limited with respect to the diversity of this broad class of metalloproteins. Experimental efforts in the structural investigation of MHCs are thus warranted.     

Change in conformation with reduction of alpha-helix content causes loss of neutrophil binding activity in fully cytotoxic Shiga toxin 1

Shiga toxins (Stx) play an important role in the pathogenesis of hemolytic uremic syndrome, a life-threatening renal sequela of human intestinal infection caused by specific Escherichia coli strains. Stx target a restricted subset of human endothelial cells that possess the globotriaosylceramide receptor, like that in renal glomeruli. The toxins, composed of five B chains and a single enzymatic A chain, by removing adenines from ribosomes and DNA, trigger apoptosis and the production of pro-inflammatory cytokines in target cells. Because bacteria are confined to the gut, the toxins move to the kidney through the circulation. Polymorphonuclear leukocytes (PMN) have been indicated as the carriers that "piggyback" shuttle toxins to the kidney. However, there is no consensus on this topic, because not all laboratories have been able to reproduce the Stx/PMN interaction. Here, we demonstrate that conformational changes of Shiga toxin 1, with reduction of α-helix content and exposition to solvent of hydrophobic tryptophan residues, cause a loss of PMN binding activity. The partially unfolded toxin was found to express both enzymatic and globotriaosylceramide binding activities being fully active in intoxicating human endothelial cells; this suggests the presence of a distinct PMN-binding domain. By reviewing functional and structural data, we suggest that A chain moieties close to Trp-203 are recognized by PMN. Our findings could help explain the conflicting results regarding Stx/PMN interactions, especially as the groups reporting positive results obtained Stx by single-step affinity chromatography, which could have preserved the correct folding of Stx with respect to more complicated multi-step purification methods.     

Hybrid physics-based and data-driven modeling for bioprocess online simulation and optimization

Model-based online optimization has not been widely applied to bioprocesses due to the challenges of modeling complex biological behaviors, low-quality industrial measurements, and lack of visualization techniques for ongoing processes. This study proposes an innovative hybrid modeling framework which takes advantages of both physics-based and data-driven modeling for bioprocess online monitoring, prediction, and optimization. The framework initially generates high-quality data by correcting raw process measurements via a physics-based noise filter (a generally available simple kinetic model with high fitting but low predictive performance); then constructs a predictive data-driven model to identify optimal control actions and predict discrete future bioprocess behaviors. Continuous future process trajectories are subsequently visualized by re-fitting the simple kinetic model (soft sensor) using the data-driven model predicted discrete future data points, enabling the accurate monitoring of ongoing processes at any operating time. This framework was tested to maximize fed-batch microalgal lutein production by combining with different online optimization schemes and compared against the conventional open-loop optimization technique. The optimal results using the proposed framework were found to be comparable to the theoretically best production, demonstrating its high predictive and flexible capabilities as well as its potential for industrial application.     

Structure elucidation of new compounds from acidic treatment of the progestins gestodene and drospirenone

Gestodene acidic treatment afforded a single rearrangement product, namely 13-beta-ethyl-18,19-dinorpregna-4,14,16-trien-3,20-dione 3, which was originated through HCl-catalyzed Rupe rearrangement. Drospirenone acidic treatment yielded two epimeric lactones by addition of HCl to the 6beta,7beta-cyclopropane ring, namely 7beta-(chloromethyl)-15beta,16beta-methylene-3-oxo-17beta-pregn-4-ene-21,17-carbolactone 4 and 7beta-(chloromethyl)-15beta,16beta-methylene-3-oxo-17alpha-pregn-4-ene-21,17-carbolactone 5. The structure of the compounds was assessed by spectroscopic and crystallographic methods.