Generation of New Hairless Alleles by Genomic Engineering at the Hairless Locus in Drosophila melanogaster

Hairless (H) is the major antagonist within the Notch signalling pathway of Drosophila melanogaster. By binding to Suppressor of Hairless [Su(H)] and two co-repressors, H induces silencing of Notch target genes in the absence of Notch signals. We have applied genomic engineering to create several new H alleles. To this end the endogenous H locus was replaced with an attP site by homologous recombination, serving as a landing platform for subsequent site directed integration of different H constructs. This way we generated a complete H knock out allele H ^attP, reintroduced a wild type H genomic and a cDNA-construct (H ^gwt, H ^cwt) as well as two constructs encoding H proteins defective of Su(H) binding (H ^LD, H ^iD). Phenotypes regarding viability, bristle and wing development were recorded, and the expression of Notch target genes wingless and cut was analysed in mutant wing discs or in mutant cell clones. Moreover, genetic interactions with Notch (N ⁵⁴¹⁹) and Delta (Dl ^B2) mutants were addressed. Overall, phenotypes were largely as expected: both H ^LD and H ^iD were similar to the H ^attP null allele, indicating that most of H activity requires the binding of Su(H). Both rescue constructs H ^gwt and H ^cwt were homozygous viable without phenotype. Unexpectedly, the hemizygous condition uncovered that they were not identical to the wild type allele: notably H ^cwt showed a markedly reduced activity, suggesting the presence of as yet unidentified regulatory or stabilizing elements in untranslated regions of the H gene. Interestingly, H ^gwt homozygous cells expressed higher levels of H protein, perhaps unravelling gene-by-environment interactions.     

Outcome,transport times,and costs of patients evacuated by helicopter versus fixed-wing aircraft.

We determined the differences in transport times and costs for patients transported by fixed-wing aircraft versus helicopter at ranges of 101 to 150 radial miles, where fixed-wing and helicopter in-hospital transports commonly overlap. Statistical analysis failed to show a significant difference between the trauma-care patients transported by helicopter (n = 109) and those transported by fixed-wing (n = 86) for age, injury severity score, hospital length of stay, hospital mortality, or discharge disability score. The times in returning patients to the receiving hospital by helicopter (n = 104) versus fixed-wing (n = 509) did not differ significantly. Helicopter transport costs per mile ($24), however, were 400% higher than those of fixed-wing aircraft with its associated ground ambulance transport costs ($6). Thus, helicopter transport is economically unjustified for interhospital transports exceeding 100 radial miles when an efficient fixed-wing service exists.     

COVID-19 and “natural” experiments arising from physical distancing: a hypothetical case study from chronobiology

ABSTRACT

With countless “natural” experiments triggered by the COVID-19-associated physical distancing, one key question comes from chronobiology: “When confined to homes, how does the reduced exposure to natural daylight arising from the interruption of usual outdoor activities plus lost temporal organization ordinarily provided from workplaces and schools affect the circadian timing system (the internal 24 h clock) and, consequently, health of children and adults of all ages?” Herein, we discuss some ethical and scientific facets of exploring such natural experiments by offering a hypothetical case study of circadian biology.     

X-ray absorption spectroscopy of selenium-containing amino acids

Received: 2 April 1999 / Accepted: 17 September 1999     

Characterization and partial purification of <Emphasis Type="Italic">Candida albicans</Emphasis> Secretory IL-12 Inhibitory Factor

Background  

We have previously shown that supernatant from Candida albicans (CA) culture contains a Secretory Interleukin (IL)-12 Inhibitory Factor (CA-SIIF), which inhibits IL-12 production by human monocytes. However, the effect of CA-SIIF on secretion of other cytokines by monocytes is unknown, and detailed characterization of this factor has not been performed.     

Two new variants of the lipocalin allergen Bos d 2

Allergens from various sources have been shown to comprise several isoforms. In the present study, a series of chromatographic steps was carried out to separate the lipocalin allergen Bos d 2 isoforms present in cow dander. Subsequent HPLC-MS–MS analyses revealed two new Bos d 2 variants. In one of the proteins, tyrosine (Y83) was substituted by aspartic acid, and in the other protein valine (V102) was replaced by alanine. We propose the three Bos d 2 variants be named as Bos d 2.0101 (previously sequenced Bos d 2), Bos d 2.0102 and Bos d 2.0103. Our results suggest that molecular polymorphism is a common property among lipocalin allergens. Since allergen isoforms may show variation in their IgE binding and/or T-cell reactivity, all of the many allergen forms should be taken into account when planning preparations for immunotherapy.     

Explicit links among physical stress, habitat heterogeneity and biodiversity

We tested the links among biodiversity, habitat heterogeneity and physical stress in a system of artificial rock pools on the north coast of Jamaica that mimic natural aquatic invertebrate communities. The experimental design consisted of three tiers of small plastic pools arranged at increasing distances from the shore. As a result of community development over six months (January to June 1997), we observed considerable differentiation of physical conditions among replicate habitats at the benign end of the physical gradient, with a concurrent increase in biodiversity (species richness per habitat unit). The most probable explanation for this observed gradient is self-generated habitat heterogeneity that, in turn, promotes biodiversity, likely through species interactions. Using additional analyses, including randomization techniques, we excluded the effects of sample size and external factors as sources for the observed increase in biodiversity in the third tier (furthest from the sea). We interpret this result as evidence for the complex causal relationship among physical stress, habitat heterogeneity and biodiversity.