Controlled Fuzzy Parallel Rewriting

We study a Lindenmayer-like parallel rewriting system to model the growth of filaments (arrays of cells) in which developmental errors may occur. In essence this model is the fuzzy analogue of the derivation-controlled iteration grammar. Under minor assumptions on the family of control languages and on the family of fuzzy languages in the underlying iteration grammar, we show (i) regular control does not provide additional generating power to the model, (ii) the number of fuzzy substitutions in the underlying iteration grammar can be reduced to two, and (iii) the resulting family of fuzzy languages possesses strong closure properties, viz. it is a full hyper-AFFL, i.e., a hyper-algebraically closed full Abstract Family of Fuzzy Languages

LYVE1 Marks the Divergence of Yolk Sac Definitive Hemogenic Endothelium from the Primitive Erythroid Lineage.

The contribution of the different waves and sites of developmental hematopoiesis to fetal and adult blood production remains unclear. Here, we identify lymphatic vessel endothelial hyaluronan receptor-1 (LYVE1) as a marker of yolk sac (YS) endothelium and definitive hematopoietic stem and progenitor cells (HSPCs). Endothelium in mid-gestation YS and vitelline vessels, but not the dorsal aorta and placenta, were labeled by Lyve1-Cre. Most YS HSPCs and erythro-myeloid progenitors were Lyve1-Cre lineage traced, but primitive erythroid cells were not, suggesting that they represent distinct lineages. Fetal liver (FL) and adult HSPCs showed 35%-40% Lyve1-Cre marking. Analysis of circulation-deficient Ncx1-/- concepti identified the YS as a major source of Lyve1-Cre labeled HSPCs. FL proerythroblast marking was extensive at embryonic day (E) 11.5-13.5, but decreased to hematopoietic stem cell (HSC) levels by E16.5, suggesting that HSCs from multiple sources became responsible for erythropoiesis. Lyve1-Cre thus marks the divergence between YS primitive and definitive hematopoiesis and provides a tool for targeting YS definitive hematopoiesis and FL colonization

CtBP impedes JNK- and Upd/STAT-driven cell fate misspecifications in regenerating Drosophila imaginal discs.

Regeneration following tissue damage often necessitates a mechanism for cellular re-programming, so that surviving cells can give rise to all cell types originally found in the damaged tissue. This process, if unchecked, can also generate cell types that are inappropriate for a given location. We conducted a screen for genes that negatively regulate the frequency of notum-to-wing transformations following genetic ablation and regeneration of the wing pouch, from which we identified mutations in the transcriptional co-repressor C-terminal Binding Protein (CtBP). When CtBP function is reduced, ablation of the pouch can activate the JNK/AP-1 and JAK/STAT pathways in the notum to destabilize cell fates. Ectopic expression of Wingless and Dilp8 precede the formation of the ectopic pouch, which is subsequently generated by recruitment of both anterior and posterior cells near the compartment boundary. Thus, CtBP stabilizes cell fates following damage by opposing the destabilizing effects of the JNK/AP-1 and JAK/STAT pathways

Closing the feedback loop: physics undergraduates’ use of feedback comments on laboratory coursework

The laboratory notebooks of physics undergraduates taking two second-year practical courses were audited to discover whether they had used feedback comments in their subsequent coursework. Ninety-five per cent of the 37 students on the first course and 100% of the 14 students on the second course whose work was audited had used feedback. The marker’s comments were classified into two groups based on whether they addressed simple (mastery) or complex (developmental) learning outcomes. Mastery comments were more likely to be acted on than developmental comments which aimed to extend students’ skills and understanding to higher levels. This has implications for the use of feedback audit as a quality control process, since the feedback which is most commonly applied by students is not the most valuable for the development of higher order skills. Following reflection on the results for the first course, students taking the second course were given responsibility for checking their peers’ notebooks against preset criteria. Peer checking improved students’ marks but did not eliminate the need for mastery feedback. It is argued that a direct audit of students’ use of feedback is particularly valuable when undertaken by the teacher who provides the feedback

Cell lineage analysis of the avian neural crest

Neural crest cells migrate extensively and give rise to diverse cell types, including cells of the sensory and autonomic nervous systems. A major unanswered question concerning the neural crest is when and how the neural crest cells become determined to adopt a particular fate. We have explored the developmental potential of trunk neural crest cells in avian embryos by microinjecting a vital dye, lysinated rhodamine dextran (LRD), into individual cells within the dorsal neural tube. We find that premigratory and emigrating neural crest cells give rise to descendants with distinct phenotypes in multiple neural crest derivatives. These results are consistent with the idea that neural crest cells are multipotent prior to their emigration from the neural tube and become restricted in phenotype after emigration from the neural tube either during their migration or at their sites of localization. To determine whether neural crest cells become restricted during their migration, we have microinjected individual trunk neural crest cells with dye shortly after they leave the neural tube or as they migrate through the somite. We find that a majority of the clones derived from migrating neural crest cells appear to be multipotent; individual migrating neural crest cells gave rise to both sensory and sympathetic neurons, as well as cells with the morphological characteristics of Schwann cells, and other nonneuronal cells. Even those clones contributing to only one neural crest derivative often contained both neurofilament-positive and neurofilament-negative cells. These data demonstrate that migrating trunk neural crest cells, like their premigratory progenitors, can be multipotent. They give rise to cells in multiple neural crest derivatives and contribute to both neuronal and non-neuronal elements within a given derivative. Thus, restriction of neural crest cell fate must occur relatively late in migration or at the final destinations

Comparative Study of Life Histories, Laboratory Rearing, and Immature Stages of \u3ci\u3eEuschistus Servus\u3c/i\u3e and \u3ci\u3eEuschistus Variolarius\u3c/i\u3e (Hemiptera: Pentatomidae)

A comparative study was conducted of the field life histories of Euschistus servus and E. varialarius in southern Illinois, their life cycles under controlled laboratory conditions, and their immature stages. The results indicate that E. servus is bivoltine and E. variolarius is univoltine. Adults of both species emerged from overwintering sites during early April, began feeding and copulating on leaves of common mullein (Verbascum thapsus) and surrounding vegetation, and reproduced shortly thereafter. Neither eggs and first instars of either species, nor second instars of E. variolarius, were collected in the field. Seasonal occurrences of the adults and subsequent immature stages are discussed for each species. No individuals were found after the first week of November. Both species were reared on green beans (Phaseolus vulgaris) under a 16L:8D photoperiod and constant temperature of 23 ± 0.06° C. The incubation period averaged 5.8 days for E. servus and 5.4 days for E. variolanus. Durations of the 5 subsequent stadia averaged, respectively, 5, 6, 6.7, 9.3, and 11.5 days for E. servus, and 4.9,5.7,7.8,9.7, and 13.3 days for E. varialarius. Comparisons of incubation period and stadia between the two species showed that only the stadia for the first instars were not statistically different. Total developmental period was longer for E. varialarius than for E. servus. The external anatomy of the egg and each of the five nymphal instars is described for each species

Developmental potential of trunk neural crest cells in the mouse

The availability of naturally occurring and engineered mutations in mice which affect the neural crest makes the mouse embryo an important experimental system for studying neural crest cell differentiation. Here, we determine the normal developmental potential of neural crest cells by performing in situ cell lineage analysis in the mouse by microinjecting lysinated rhodamine dextran (LRD) into individual dorsal neural tube cells in the trunk. Labeled progeny derived from single cells were found in the neural tube, dorsal root ganglia, sympathoadrenal derivatives, presumptive Schwann cells and/or pigment cells. Most embryos contained labeled cells both in the neural tube and at least one neural crest derivative, and numerous clones contributed to multiple neural crest derivatives. The time of injection influenced the derivatives populated by the labeled cells. Injections at early stages of migration yielded labeled progeny in both dorsal and ventral neural crest derivatives, whereas those performed at later stages had labeled cells only in more dorsal neural crest derivatives, such as dorsal root ganglion and presumptive pigment cells. The results suggest that in the mouse embryo: (1) there is a common precursor for neural crest and neural tube cells; (2) some neural crest cells are multipotent; and (3) the timing of emigration influences the range of possible neural crest derivatives