Activation of NOTCH1 or NOTCH3 Signaling Skews Human Airway Basal Cell Differentiation toward a Secretory Pathway

Airway basal cells (BC) function as stem/progenitor cells capable of differentiating into the luminal ciliated and secretory cells to replenish the airway epithelium during physiological turnover and repair. The objective of this study was to define the role of Notch signaling in regulating human airway BC differentiation into a pseudostratified mucociliated epithelium. Notch inhibition with γ-secretase inhibitors demonstrated Notch activation is essential for BC differentiation into secretory and ciliated cells, but more so for the secretory lineage. Sustained cell autonomous ligand independent Notch activation via lentivirus expression of the intracellular domain of each Notch receptor (NICD1-4) demonstrated that the NOTCH2 and 4 pathways have little effect on BC differentiation into secretory and ciliated cells, while activation of the NOTCH1 or 3 pathways has a major influence, with persistent expression of NICD1 or 3 resulting in a skewing toward secretory cell differentiation with a parallel decrease in ciliated cell differentiation. These observations provide insights into the control of the balance of BC differentiation into the secretory vs ciliated cell lineage, a balance that is critical for maintaining the normal function of the airway epithelium in barrier defense against the inhaled environment.     

Why is intracellular ice lethal? A microscopical study showing evidence of programmed cell death in cryo-exposed embryonic axes of recalcitrant seeds of Acer saccharinum

Background and Aims Conservation of the genetic diversity afforded by recalcitrant seeds is achieved by cryopreservation, in which excised embryonic axes (or, where possible, embryos) are treated and stored at temperatures lower than −180 °C using liquid nitrogen. It has previously been shown that intracellular ice forms in rapidly cooled embryonic axes of Acer saccharinum (silver maple) but this is not necessarily lethal when ice crystals are small. This study seeks to understand the nature and extent of damage from intracellular ice, and the course of recovery and regrowth in surviving tissues.Methods Embryonic axes of A. saccharinum, not subjected to dehydration or cryoprotection treatments (water content was 1·9 g H₂O g⁻¹ dry mass), were cooled to liquid nitrogen temperatures using two methods: plunging into nitrogen slush to achieve a cooling rate of 97 °C s⁻¹ or programmed cooling at 3·3 °C s⁻¹. Samples were thawed rapidly (177 °C s⁻¹) and cell structure was examined microscopically immediately, and at intervals up to 72 h in vitro. Survival was assessed after 4 weeks in vitro. Axes were processed conventionally for optical microscopy and ultrastructural examination.Key Results Immediately following thaw after cryogenic exposure, cells from axes did not show signs of damage at an ultrastructural level. Signs that cells had been damaged were apparent after several hours of in vitro culture and appeared as autophagic decomposition. In surviving tissues, dead cells were sloughed off and pockets of living cells were the origin of regrowth. In roots, regrowth occurred from the ground meristem and procambium, not the distal meristem, which became lethally damaged. Regrowth of shoots occurred from isolated pockets of surviving cells of peripheral and pith meristems. The size of these pockets may determine the possibility for, the extent of and the vigour of regrowth.Conclusions Autophagic degradation and ultimately autolysis of cells following cryo-exposure and formation of small (0·2–0·4 µm) intracellular ice crystals challenges current ideas that ice causes immediate physical damage to cells. Instead, freezing stress may induce a signal for programmed cell death (PCD). Cells that form more ice crystals during cooling have faster PCD responses.     

Microsatellite primers for Texas wild rice (<Emphasis Type="Italic">Zizania texana</Emphasis>), and a preliminary test of the impact of cryogenic storage on allele frequency at these loci

Seed collections in gene banks are useful for the preservation of wild germplasm, providing inexpensive insurance for species that survive in conventional cold storage (–18 °C). Seeds that cannot survive these conditions must be pretreated with cryoprotectants and stored at liquid nitrogen temperatures, which presents unique technical and methodological challenges. Implicit in this approach is the assumption that these added manipulations do not change the genetic diversity of the preserved collections. We used polymorphic microsatellite markers for an endangered aquatic grass, Texas wild rice (Zizania texana), to conduct a preliminary evaluation of the effects of cryogenic preservation of mature embryos on genetic diversity. Using several statistical approaches, we show that allele frequencies did not change in collections of seeds that underwent cryopreservation (cryoprotected) compared to those samples that was not exposed to cryopreservation (control). The retention of the allelic diversity at the five loci examined suggests that there were no significant changes in genetic diversity due to treatments and that these protocols may be appropriate for ex situ conservation of genetically diverse wild germplasm.     

Food availability and sex reversal in Mytella charruana,an introduced bivalve in the southeastern United States

We studied the reproductive biology of Mytella charruana to determine the potential reproductive success of this newly introduced bivalve species from Central/South America. We analyzed gonad morphology, gametogenesis, and the sex ratios of introduced populations throughout a 12 month period. In the non‐native habitat M. charruana shows the same strategy of gametogenesis that had been observed in its native environment, which is an opportunistic type of gonadal cycle with gametes produced throughout the year. Instead, the spawning period of M. charruana along the southeastern US coast is extended compared to that found in the native environment. We determined the minimum size (shell length) of sexually reproductive mussels to be 1.25 cm. Interestingly, throughout the year the population samples were typically composed of a higher proportion of females. The female to male sex ratio varied within a wide range from 1:0 to 1:3.3. Upon this discovery we tested the effects of food availability on the gametogenesis of adult animals. The sex ratio of mussels collected from different locations and maintained in the laboratory with or without food changed toward a male‐bias under starvation conditions within a month. This is the first study directly showing that food availability can trigger sex reversal in an adult bivalve. According to our data this mussel species will likely continue to spread along the east coast of the US. Moreover, M. charruana may prove to be a model organism in the study of alternative sexuality in bivalves. Mol. Reprod. Dev. 77: 222–230, 2010. © 2009 Wiley‐Liss, Inc.     

A new adaptive time step method for unsteady flow simulations in a human lung

The innovation presented is a method for adaptive time-stepping that allows clustering of time steps in portions of the cycle for which flow variables are rapidly changing, based on the concept of using a uniform step in a relevant dependent variable rather than a uniform step in the independent variable time. A user-defined function was developed to adapt the magnitude of the time step (adaptive time step) to a defined rate of change in inlet velocity. Quantitative comparison indicates that the new adaptive time stepping method significantly improves accuracy for simulations using an equivalent number of time steps per cycle.     

The identification and optimisation of novel and selective diamide neuropeptide Y Y2 receptor antagonists

A novel small molecule NPY Y2 antagonist (3) identified from high throughput screening is described. A subsequent SAR study and optimisation programme based around this molecule is also described, leading to the identification of potent and soluble pyridyl analogue 36.     

Urbanization,sedimentation, and the homogenization of fish assemblages in the Etowah River Basin,USA

We tested the hypothesis that urbanization alters stream sediment regimes and homogenizes fish assemblages in 30 sub-basins of the Etowah River. Sediment variables included average particle size (mean phi) of the stream bed, percent fines (<2 mm) in riffles, and baseflow turbidity (NTU). Homogenization was quantified as ratios of endemic to cosmopolitan species richness (E_r:C_r) and abundance (E_a:C_a). High NTU and fine stream beds were associated with homogenized assemblages (i.e., lower E:C ratios). Mean phi and NTU were significantly correlated with E:C ratios (r = –0.74 to –0.76) and, when combined using multiple regression, accounted for 73% of the variance in ratios. Stream slope strongly covaried with mean phi (r = –0.92) and percent fines in riffles (r = –0.79), but multiple regression models showed that urbanized sites had finer beds and riffles than predicted by slope alone. Urban land cover was the primary predictor of NTU (r ² = 0.42) and, combined with slope in multiple regression, explained 51% of the variance in NTU. Our results indicate that stream slope is a background variable predicting particle size and E:C ratios in these streams. Urbanization disrupts these relationships by transforming clear streams with coarse beds into turbid streams with finer beds. These conditions favor cosmopolitan species, ultimately homogenizing fish assemblages. Bed texture was linked to urbanization; however, NTU was the best indicator of urban impacts because it was statistically independent from slope.