Gamma-irradiated human amniotic membrane decellularised with sodium dodecyl sulfate is a more efficient substrate for the ex vivo expansion of limbal stem cells

yesThe gold standard substrate for the ex vivo expansion of human limbal stem cells (LSCs) remains the human amniotic membrane (HAM) but this is not a defined substrate and is subject to biological variabil-ity and the potential to transmit disease. To better define HAM and mitigate the risk of disease transmis-sion, we sought to determine if decellularisation and/or c-irradiation have an adverse effect on culture growth and LSC phenotype. Ex vivo limbal explant cultures were set up on fresh HAM, HAM decellularised with 0.5 M NaOH, and 0.5% (w/v) sodium dodecyl sulfate (SDS) with or without c-irradiation. Explant growth rate was measured and LSC phenotype was characterised by histology, immunostaining and qRT-PCR (ABCG2, DNp63, Ki67, CK12, and CK13). Ƴ-irradiation marginally stiffened HAM, as measured by Brillouin spectromicroscopy. HAM stiffness and c-irradiation did not significantly affect the LSC phe-notype, however LSCs expanded significantly faster on Ƴ-irradiated SDS decellularised HAM (p < 0.05) which was also corroborated by the highest expression of Ki67 and putative LSC marker, ABCG2. Colony forming efficiency assays showed a greater yield and proportion of holoclones in cells cultured on Ƴ-irradiated SDS decellularised HAM. Together our data indicate that SDS decellularised HAM may be a more efficacious substrate for the expansion of LSCs and the use of a c-irradiated HAM allows the user to start the manufacturing process with a sterile substrate, potentially making it safer

Undecidability in number theory

These lecture notes cover classical undecidability results in number theory, Hilbert's 10th problem and recent developments around it, also for rings other than the integers. It also contains a sketch of the authors result that the integers are universally definable in the rationals.Comment: 48 pages. arXiv admin note: text overlap with arXiv:1011.342

Differentially expressed genes associated with dormancy or germination of Arabidopsis thaliana seeds

Differential display analysis using dormant and non-dormant Arabidopsis thaliana (L.) Heynh seeds resulted in a set of genes that were associated with either dormancy or germination. Expression of the germination-associated genes AtRPL36B and AtRPL27B, encoding two ribosomal proteins, was undetectable in the dry seed, low in dormant seed, and high under conditions that allowed completion of germination. Expression of these genes was also found to be light-regulated and to correlate with germination speed. Expression of the dormancy-associated genes ATS2 and ATS4, encoding a caleosin-like protein and a protein similar to a low-temperature-induced protein respectively, was high in the dry seed and decreased during germination. Expression of ATS2 and ATS4 was high in primary and secondary dormant seed but low in after-ripened or chilled seed. The expression of both genes was also light-regulated, but no relationship with temperature-dependent germination speed was found

A Global analysis of water and nitrogen relationships between mistletoes and their hosts : broad-scale tests of old and enduring hypotheses

Mistletoes use far more water per unit carbon fixed during photosynthesis than their hosts (i.e. they have lower 'water use efficiency', WUE). The widely cited 'nitrogen-parasitism hypothesis' posits that N is the most limiting resource for mistletoes and that they use their faster transpiration rates to acquire sufficient N from the host xylem. In a rather different context, the 'mimicry hypothesis' arose in the literature suggesting that some mistletoes mimic the morphology of host leaves in order to deploy higher N leaves without suffering higher levels of herbivory. These two non-exclusive hypotheses share the common goal of trying to explain patterns of mistletoe leaf N concentration. We set out to test the generality of both hypotheses at broad geographic scale using data for 168 mistletoes-host pairs, from 39 sites, encompassing all continents except Antarctica. We drew together data from published literature and our own field data on two key plant functional traits, leaf N concentration (Nmass) and leaf carbon isotopic composition (δ¹³C) (representing long-term WUE and degree of stomatal control over photosynthesis). Key findings included (i) little or no support for the N-parasitism hypothesis: differences in mistletoe and host Nmass explained only 3% variation in differences in leaf δ¹³C, and mistletoe-host differences in leaf δ¹³C were unrelated to whether or not the hosts were N-fixers (presumed to have higher N concentration in xylem sap); (ii) partial support for the mimicry hypothesis: mimic mistletoes generally had higher Nmass when associated with N-fixing hosts (but, on non-N-fixing hosts there was no such pattern); and (iii) more broadly, mistletoes showed similar trait responses as their hosts to environmental drivers; for example, they showed similar-magnitude shifts in Nmass and δ¹³C in relation to site aridity. Contrary to current belief, our findings suggest that nitrogen is not the limiting nutrient for mistletoes, at least not the main component driving the faster transpiration rates. Our results also give insight into the evolution of mimicry in mistletoes and show, for the first time, that mistletoes are also constrained by local water availability, exhibiting clear trait adaptations to environmental gradients. By reconsidering these issues at broad geographic scale and across a large number of species, our findings substantially modify current knowledge on the ecology and physiology of mistletoes and their hosts.11 page(s