Bacteriophage Mu-1-induced mutation to mutT in Escherichia coli.

Of approximately 10,000 independent phage Mu-1 lysogens, 3 had a mutator phenotype. One (mutation designated mut-49) resembled mutT1 in the frequency and types of mutations induced. mut-49 was mapped between leu and ace and was not separable from the Mu prophage. mut-49 was recessive and did not complement mutT1. mut-49, like mutT1, did not increase the reversion of the frameshift mutation lac Z (ICR48). mut-49 and mutT1 induced the same two classes of trpA78 revertants, indicating that mut-49 induced adenine-thymine leads to cytosine-guanine transversions. The results support previous work indicating that the mutational specificity of mutT is gene and not allele specific.     

Characterization of Dahl salt-sensitive rats with genetic disruption of the A2B adenosine receptor gene: implications for A2B adenosine receptor signaling during hypertension

The A_2B adenosine receptor (AR) has emerged as a unique member of the AR family with contrasting roles during acute and chronic disease states. We utilized zinc-finger nuclease technology to create A_2BAR gene (Adora2b)-disrupted rats on the Dahl salt-sensitive (SS) genetic background. This strategy yielded a rat strain (SS-Adora2b mutant rats) with a 162-base pair in-frame deletion of Adora2b that included the start codon. Disruption of A_2BAR function in SS-Adora2b mutant rats was confirmed by loss of agonist (BAY 60-6583 or NECA)-induced cAMP accumulation and loss of interleukin-6 release from isolated fibroblasts. In addition, BAY 60-6583 produced a dose-dependent increase in glucose mobilization that was absent in SS-Adora2b mutants. Upon initial characterization, SS-Adora2b mutant rats were found to exhibit increased body weight, a transient delay in glucose clearance, and reduced proinflammatory cytokine production following challenge with lipopolysaccharide (LPS). In addition, blood pressure was elevated to a greater extent (∼15–20 mmHg) in SS-Adora2b mutants as they aged from 7 to 21 weeks. In contrast, hypertension augmented by Ang II infusion was attenuated in SS-Adora2b mutant rats. Despite differences in blood pressure, indices of renal and cardiac injury were similar in SS-Adora2b mutants during Ang II-augmented hypertension. We have successfully created and validated a new animal model that will be valuable for investigating the biology of the A_2BAR. Our data indicate varying roles for A_2BAR signaling in regulating blood pressure in SS rats, playing both anti- and prohypertensive roles depending on the pathogenic mechanisms that contribute to blood pressure elevation.     

Effects of increased intracellular pH-buffering capacity on the light response of Limulus ventral photoreceptor

Aspects of a possible involvement of hydrogen ions in the electrophysiological responses to light of Limulus ventral photoreceptors were investigated. A I M solution of either a zwitter-ionic pH buffer or a weakly-buffering control substance was pressure injected through a micropipette into a ventral photoreceptor cell. To estimate the amount injected, ³⁵SO₄ was included in the solution. Membrane currents induced by light flashes were measured by a voltage-clamp technique. The buffer-filled micropipette passed current and a 3 M KCl filled micropipette monitored membrane voltage. The sensitivity (peak light-induced current/stimulus energy) was measured, after dark adaptation, before and after injection. Injections of buffers, pH 6.3–7.2, to intracellular concentrations of at least 40–200 mM produced only a small mean decrease in sensitivity, approximately equal to that caused by injections of control substances. Excitation, therefore, apparently is not mediated by a change in intracellular pH. Buffers with pH values 5.4–8.4 were also injected. The time to peak of the response depended on pH, being shortened by up to 20% at pH values below 7.7 and lengthened at higher pH values. The time to peak of the response appeared to be shortened by an increase in intracellular pH-buffering capacity even when there was no change in intracellular pH.     

FITNESS CONSEQUENCES OF SEASONAL POLYPHENISM IN WESTERN WHITE BUTTERFLIES

The western white butterfly, Pontia occidentalis, has distinctly different wing phenotypes during spring and summer generations as a result of phenotypic plasticity (seasonal polyphenism). We experimentally generated different seasonal phenotypes in the lab by altering photoperiodic conditions during rearing, and released the resulting butterflies in the field. Mark-recapture studies were then used to estimate the effects of the polyphenism on activity patterns and adult survival in both late-spring (one study) and summer (two studies) conditions. There were no significant effects of rearing treatment on temporal patterns of behavioral activity during either the late-spring or the summer field studies. Recapture probabilities were consistently higher for males than females in all three field studies; in the summer 1992 study, recapture probabilities were higher for long-day (LD) than for short-day (SD) treatment groups. During the late-spring 1992 study, there were no significant differences between LD and SD treatment groups for survival probabilities. In the two summer studies, there were significant effects of photoperiodic treatment on survival probabilities; in the summer 1992 study, LD individuals consistently had higher survival probabilities than SD individuals; in the summer 1991 study, there was a significant interaction between treatment and time period on survival probabilities, such that survival probabilities were higher for LD than for SD individuals in two of four time periods. The consistent differences in survival probabilities between treatment groups in the summer 1992 study can be accounted for by the differences in wing traits between the treatment groups. Micrometeorological data from the study site showed that midday ambient temperatures averaged ~3°C hotter during the 1992 than the 1991 summer study and that ambient conditions during the late-spring 1992 study were relatively warm and sunny for the season. These results document the varying relationships between phenotype and fitness in the temporally fluctuating environments experienced by this population.     

Production of rhamnolipids in solid-state cultivation: Characterization,downstream processing and application in the cleaning of contaminated soils

Pseudomonas aeruginosa UFPEDA 614 produced a rhamnolipid biosurfactant when grown on sugarcane bagasse impregnated with a solution containing glycerol. Biosurfactant levels reached 40 g of rhamnolipid per kilogram of dry initial substrate after 12 days. On the basis of the volume of liquid used, the biosurfactant levels were similar to those obtained in submerged liquid culture of a medium identical to the impregnating solution. The properties of the biosurfactant were very similar to those obtained with rhamnolipids produced in submerged culture, with a critical micelle concentration of 46.8 mg/L and an emulsification index at 24 h of over 90% against gasoline. The surface properties were maintained after autoclaving of the fermented solids, meaning that it is possible to minimize safety risks by killing the producing organism with a heat treatment of the solids prior to product extraction. The biosurfactant was used in the washing of soils contaminated with gasoline. An aqueous biosurfactant solution was 3.2-fold more efficient than water in leaching organic material from the soil, demonstrating the viability of application of rhamnolipids in the bioremediation of soils contaminated with gasoline.