The municipal council, my neighbors and me: Social environmental influences in the city.

This study seeks to examine the extent to which the level of municipal environmental management affects and complies with the behavioral norms of urban communities (city norms), and to what extent these affect environmental behavior at the individual level. We used a two-step, mixed-methods approach: a quantitative study of a representative sample of the urban sector (n = 1000) in Israel, followed by a qualitative in-depth interview process (n = 20). Municipal environmental management was found to be strongly correlated with city norms. Multiple regression analyses revealed that the residents' environmental behavior was strongly influenced solely by city norms (and not by the municipal council's conduct). However, our interviews revealed that residents explicitly attributed their pro- or anti-environmental behavior almost solely to the municipal council's conduct (and not to city norms). These relative contributions of municipal environmental management versus city norms on environmental behavior varied across environmental domains. In the Discussion section, we offer an explanation to the seemingly contradictory findings, and offer specific recommendations for several actions and initiatives that local authorities can adopt to promote pro-environmental behavior among its residents' and thus reduce the ecological footprint of the city as a whole.

Chromosomal duplication is a transient evolutionary solution to stress.

Aneuploidy, an abnormal number of chromosomes, is a widespread phenomenon found in unicellulars such as yeast, as well as in plants and in mammalians, especially in cancer. Aneuploidy is a genome-scale aberration that imposes a severe burden on the cell, yet under stressful conditions specific aneuploidies confer a selective advantage. This dual nature of aneuploidy raises the question of whether it can serve as a stable and sustainable evolutionary adaptation. To clarify this, we conducted a set of laboratory evolution experiments in yeast and followed the long-term dynamics of aneuploidy under diverse conditions. Here we show that chromosomal duplications are first acquired as a crude solution to stress, yet only as transient solutions that are eliminated and replaced by more efficient solutions obtained at the individual gene level. These transient dynamics of aneuploidy were repeatedly observed in our laboratory evolution experiments; chromosomal duplications gained under stress were eliminated not only when the stress was relieved, but even if it persisted. Furthermore, when stress was applied gradually rather than abruptly, alternative solutions appear to have emerged, but not aneuploidy. Our findings indicate that chromosomal duplication is a first evolutionary line of defense, that retains survivability under strong and abrupt selective pressures, yet it merely serves as a "quick fix," whereas more refined and sustainable solutions take over. Thus, in the perspective of genome evolution trajectory, aneuploidy is a useful yet short-lived intermediate that facilitates further adaptation.

Adaptive prediction of environmental changes by microorganisms.

Natural habitats of some microorganisms may fluctuate erratically, whereas others, which are more predictable, offer the opportunity to prepare in advance for the next environmental change. In analogy to classical Pavlovian conditioning, microorganisms may have evolved to anticipate environmental stimuli by adapting to their temporal order of appearance. Here we present evidence for environmental change anticipation in two model microorganisms, Escherichia coli and Saccharomyces cerevisiae. We show that anticipation is an adaptive trait, because pre-exposure to the stimulus that typically appears early in the ecology improves the organism's fitness when encountered with a second stimulus. Additionally, we observe loss of the conditioned response in E. coli strains that were repeatedly exposed in a laboratory evolution experiment only to the first stimulus. Focusing on the molecular level reveals that the natural temporal order of stimuli is embedded in the wiring of the regulatory network-early stimuli pre-induce genes that would be needed for later ones, yet later stimuli only induce genes needed to cope with them. Our work indicates that environmental anticipation is an adaptive trait that was repeatedly selected for during evolution and thus may be ubiquitous in biology.

Gene expression profiles of AML derived stem cells; similarity to hematopoietic stem cells.

Tumors contain a fraction of cancer stem cells that maintain the propagation of the disease. The CD34(+)CD38(-) cells, isolated from acute myeloid leukemia (AML), were shown to be enriched leukemic stem cells (LSC). We isolated the CD34(+)CD38(-) cell fraction from AML and compared their gene expression profiles to the CD34(+)CD38(+) cell fraction, using microarrays. We found 409 genes that were at least twofold over- or underexpressed between the two cell populations. These include underexpression of DNA repair, signal transduction and cell cycle genes, consistent with the relative quiescence of stem cells, and chromosomal aberrations and mutations of leukemic cells. Comparison of the LSC expression data to that of normal hematopoietic stem cells (HSC) revealed that 34% of the modulated genes are shared by both LSC and HSC, supporting the suggestion that the LSC originated within the HSC progenitors. We focused on the Notch pathway since Jagged-2, a Notch ligand was found to be overexpressed in the LSC samples. We show that DAPT, an inhibitor of gamma-secretase, a protease that is involved in Jagged and Notch signaling, inhibits LSC growth in colony formation assays. Identification of additional genes that regulate LSC self-renewal may provide new targets for therapy.

The UVB-induced gene expression profile of human epidermis in vivo is different from that of cultured keratinocytes.

In order to obtain a comprehensive picture of the molecular events regulating cutaneous photodamage of intact human epidermis, suction blister roofs obtained after a single dose of in vivo ultraviolet (UV)B exposure were used for microarray profiling. We found a changed expression of 619 genes. Half of the UVB-regulated genes had returned to pre-exposure baseline levels at 72 h, underscoring the transient character of the molecular cutaneous UVB response. Of special interest was our finding that several of the central p53 target genes remained unaffected following UVB exposure in spite of p53 protein accumulation. We next compared the in vivo expression profiles of epidermal sheets to that of cultured human epidermal keratinocytes exposed to UVB in vitro. We found 1931 genes that differed in their expression profiles between the two groups. The expression profile in intact epidemis was geared mainly towards DNA repair, whereas cultured keratinocytes responded predominantly by activating genes associated with cell-cycle arrest and apoptosis. These differences in expression profiles might reflect differences between mature differentiating keratinocytes in the suprabasal epidermal layers versus exponentially proliferating keratinocytes in cell culture. Our findings show that extreme care should be taken when extrapolating from findings based on keratinocyte cultures to changes in intact epidermis.

Isolation and purification of viable Ureaplasma urealyticum cells free from medium components.

A procedure was devised to produce Ureaplasma urealyticum preparations free of adsorbed components of the growth medium, which contains high concentrations of serum. The ureaplasmas were cultivated in a medium containing PPLO-serum fraction as a replacement for horse serum. High titres of ureaplasmas (greater than 10(7) c.f.u. ml-1) were obtained. Harvested cells were then purified by Urografin density gradient centrifugation. By use of 3H-labelled ureaplasma cells and 125I-labelled medium components, a distinct band of viable cells devoid of serum constituents was demonstrated. The absence of medium components was verified by immunoblotting cells from this band with antiserum to medium components. Medium components that had been present before the purification procedure were undetectable in the purified cell fraction obtained. The viability of the purified ureaplasma cells represented an 85% recovery rate and their antigenicity, examined with anti-serotype specific antiserum, remained intact. This easy and reproducible procedure can be used to prepare purified ureaplasmas for investigation of ureaplasmal antigens and their expression and/or role in disease.