Molecular sieving of red cell membranes during gradual osmotic hemolysis

Summary Rat red blood corpuscles were held stationary with respect to a continuously flowing solution in either a specially constructed centrifuge or in glass filters. The concentration of the solution was gradually decreased to cause the swelling and subsequent gradual osmotic hemolysis of the cells. The passage of the intracellular molecules —potassium, adenylate kinase, and hemoglobin—across the cell membranes and into the flowing solution was determined as a function of time. Ions and molecules begin passage across the membranes in the order of increasing molecular size. The initial flow of potassium is followed by the initial flows of hemoglobin and adenylate kinase. The flow of hemoglobin has been interpreted as the flows of hemoglobin monomers, dimers, and tetramers such that the time sequence is: potassium; hemoglobin monomer; adenylate kinase/hemoglobin dimer; and finally, hemoglobin tetramer. It is concluded that the stressed cell membrane has molecular sieving properties and that the exclusion limit (effective hole size) increases as a function of time during the initial stages of gradual osmotic hemolysis. The process of gradual osmotic hemolysis is discussed in terms of molecular sieving through stress-induced effective membrane holes. It is suggested that a portion of the membrane protein might form an elastic network which would account for the gradual increase in size and apparent homogeneity of the effective holes.This work was prepared under the auspices of the U.S. Atomic Energy Commission.     

Participant understanding and recall of informed consent for induced pluripotent stem cell biobanking

The ability to generate human induced pluripotent stem cells (iPSCs) has opened new avenues for human disease modelling and therapy. The aim of our study was to determine research participants’ understanding of the information given when donating skin biopsies for the generation of patient-specific iPSCs. A customised 35-item questionnaire based on previous iPSC consent guidelines was sent to participants who had previously donated samples for iPSC research. The questionnaire asked pertinent demographic details, participants' motivation to take part in iPSC research and their attitudes towards related ethical issues. 234 participants were contacted with 141 (60.3 %) complete responses received. The median duration between recruitment and follow-up questioning was 313 days (range 10–573 days). The majority of participants (n = 129, 91.5 %) believed they understood what a stem cell was; however, only 22 (16.1 %) correctly answered questions related to basic stem cell properties. We found no statistically significant difference in responses from participants with different levels of education, or those with a health sciences background. The poor understanding amongst participants of iPSC research is unlikely to be unique to our study and may impact future research if not improved. As such, there is a need to develop an easily understood yet comprehensive consent process to ensure ongoing ethical progress of iPSC biobanking.     

The starch‐binding domain family CBM41—An in silico analysis of evolutionary relationships

Within the CAZy database, there are 81 carbohydrate‐binding module (CBM) families. A CBM represents a non‐catalytic domain in a modular arrangement of glycoside hydrolases (GHs). The present in silico study has been focused on starch‐binding domains from the family CBM41 that are usually part of pullulanases from the α‐amylase family GH13. Currently there are more than 1,600 sequences classified in the family CBM41, almost exclusively from Bacteria, and so a study was undertaken in an effort to divide the members into relevant groups (subfamilies) and also to contribute to the evolutionary picture of family CBM41. The CBM41 members adopt a β‐sandwich fold (～100 residues) with one carbohydrate‐binding site formed by the side‐chains of three aromatic residues that interact with carbohydrate. The family CBM41 can be divided into two basic subdivisions, distinguished from each other by a characteristic sequence pattern or motif of the three essential aromatics as follows: (i) “W‐W‐～10aa‐W” (the so‐called Streptococcus/Klebsiella‐type); and (ii) “W‐W‐～30aa‐W” (Thermotoga‐type). Based on our bioinformatics analysis it is clear that the first and second positions of the motif can be occupied by aromatic residues (Phe, Tyr, His) other than tryptophan, resulting in the existence of six different carbohydrate‐binding CBM41 groups, that reflect mostly differences in taxonomy, but which should retain the ability to bind an α‐glucan. In addition, three more groups have been proposed that, although lacking the crucial aromatic motif, could possibly employ other residues from remaining parts of their sequence for binding carbohydrate. Proteins 2017; 85:1480–1492. © 2017 Wiley Periodicals, Inc.     

Chemical communication,sexual selection,and introgression in wall lizards

Divergence in communication systems should influence the likelihood that individuals from different lineages interbreed, and consequently shape the direction and rate of hybridization. Here, we studied the role of chemical communication in hybridization, and its contribution to asymmetric and sexually selected introgression between two lineages of the common wall lizard (Podarcis muralis). Males of the two lineages differed in the chemical composition of their femoral secretions. Chemical profiles provided information regarding male secondary sexual characters, but the associations were variable and inconsistent between lineages. In experimental contact zones, chemical composition was weakly associated with male reproductive success, and did not predict the likelihood of hybridization. Consistent with these results, introgression of chemical profiles in a natural hybrid zone resembled that of neutral nuclear genetic markers overall, but one compound in particular (tocopherol methyl ether) matched closely the introgression of visual sexual characters. These results imply that associations among male chemical profiles, sexual characters, and reproductive success largely reflect transient and environmentally driven effects, and that genetic divergence in chemical composition is largely neutral. We therefore suggest that femoral secretions in wall lizards primarily provide information about residency and individual identity rather than function as sexual signals.     

Comparison of reproductive investment in native and non‐native populations of common wall lizards reveals sex differences in adaptive potential

Non‐native animals can encounter very different environments than those they are adapted to. Functional changes in morphology, physiology and life‐history following introduction show that organisms can adapt both fast and efficiently. It remains unclear, however, if female reproductive characters and male sexually selected behaviour show the same adaptive potential. Furthermore, the invasion success and evolutionary trajectory of non‐native species might often depend on the ability of the sexes to coordinate shifts in characters associated with reproductive strategy. The common wall lizard, Podarcis muralis, has been repeatedly introduced from southern Europe to England over the past 80 years. Lizards in England experience a cool, seasonal climate that effectively restricts recruitment to the first clutch of the season, whereas in their native range up to three clutches per season recruit. As a consequence, both females and males in non‐native populations should benefit from reducing or even eliminating their reproductive investment in second clutches. Using a combination of field data and experiments, we show that non‐native females produce relatively larger and heavier first seasonal clutches and smaller and lighter second seasonal clutches compared to native females. In contrast, non‐native and native males do not differ in their territorial and sexual behaviour later in the season. An adaptive shift in male seasonal reproductive investment may be constrained because males use breeding females as cues for sexual behaviour. If this is so, we expect a general pattern across climatic regimes whereby female reproductive investment evolves first, with responses in males lagging behind.     

A model invalidation-based approach for elucidating biological signalling pathways,applied to the chemotaxis pathway in R. sphaeroides

Background  

Developing methods for understanding the connectivity of signalling pathways is a major challenge in biological research. For this purpose, mathematical models are routinely developed based on experimental observations, which also allow the prediction of the system behaviour under different experimental conditions. Often, however, the same experimental data can be represented by several competing network models.