Keratinocyte galvanotaxis in combined DC and AC electric fields supports an electromechanical transduction sensing mechanism

Sedentary keratinocytes at the edge of a skin wound migrate into the wound, guided by the generation of an endogenous electric field (EF) generated by the collapse of the transepithelial potential. The center of the wound quickly becomes more negative than the surrounding tissue and remains the cathode of the endogenous EF until the wound is completely re‐epithelialized. This endogenous guidance cue can be studied in vitro. When placed in a direct current (DC) EF of physiological strength, 100 V/m, keratinocytes migrate directionally toward the cathode in a process known as galvanotaxis. Although a number of membrane‐bound (e.g., epidermal growth factor receptor (EGFR), integrins) and cytosolic proteins (cAMP, ERK, PI3K) are known to play a role in the downstream signaling mechanisms underpinning galvanotaxis, the initial sensing mechanism for this response is not understood. To investigate the EF sensor, we studied the migration of keratinocytes in a DC EF of 100 V/m, alternating current (AC) EFs of 40 V/m at either 1.6 or 160 Hz, and combinations of DC and AC EFs. In the AC EFs alone, keratinocytes migrated randomly. The 1.6 Hz AC EF combined with the DC EF suppressed the direction of migration but had no effect on speed. In contrast, the 160 Hz AC EF combined with the DC EF did not affect the direction of migration but increased the migration speed compared to the DC EF alone. These results can be understood in terms of an electromechanical transduction model, but not an electrodiffusion/osmosis or a voltage‐gated channel model. Bioelectromagnetics 34:85–94, 2013. © 2012 Wiley Periodicals, Inc.     

Side chain SAR of bicyclic β-lactamase inhibitors (BLIs). 2. N-Alkylated and open chain analogs of MK-8712

The bridged monobactam β-lactamase inhibitor MK-8712 (1) effectively inhibits class C β-lactamases. Side chain N-alkylated and ring-opened analogs of 1 were prepared and evaluated for combination with imipenem to overcome class C β-lactamase mediated resistance. Although some analogs were more potent inhibitors of AmpC, none exhibited better synergy with imipenem than 1.     

Thiophenyl oxime-derived phosphonates as nano-molar class C beta-lactamase inhibitors reducing MIC of imipenem against Pseudomonas aeruginosa and Acinetobacter baumannii

The preparation and characterization of a series of thiophenyl oxime phosphonate beta-lactamase inhibitors is described. A number of these analogs were potent and selective inhibitors of class C beta-lactamases from Pseudomonas aeruginosa and Enterobacter cloacae. Compounds 3b and 7 reduced the MIC of imipenem against an AmpC expressing strain of imipenem-resistant P. aeruginosa. A number of the title compounds retained micromolar potency against the class D OXA-40 beta-lactamase from Acinetobacter baumannii and at high concentrations compound 3b was shown to reduce the MIC of imipenem against a highly imipenem-resistant strain of A. baumanii expressing the OXA-40 beta-lactamase. In mice compound 3b exhibited phamacokinetics similar to imipenem.     

Trehalose-6-phosphate synthase 1, which catalyses the first step in trehalose synthesis, is essential for Arabidopsis embryo maturation

Despite the recent discovery that trehalose synthesis is widespread in higher plants very little is known about its physiological significance. Here we report on an Arabidopsis mutant (tps1), disrupted in a gene encoding the first enzyme of trehalose biosynthesis (trehalose-6-phosphate synthase). The tps1 mutant is a recessive embryo lethal. Embryo morphogenesis is normal but development is retarded and stalls early in the phase of cell expansion and storage reserve accumulation. TPS1 is transiently up-regulated at this same developmental stage and is required for the full expression of seed maturation marker genes (2S2 and OLEOSN2). Sucrose levels also increase rapidly in seeds during the onset of cell expansion. In Saccharomyces cerevisiae trehalose-6-phosphate (T-6-P) is required to regulate sugar influx into glycolysis via the inhibition of hexokinase and a deficiency in TPS1 prevents growth on sugars (Thevelein and Hohmann, 1995). The growth of Arabidopsis tps1-1 embryos can be partially rescued in vitro by reducing the sucrose level. However, T-6-P is not an inhibitor of AtHXK1 or AtHXK2. Nor does reducing hexokinase activity rescue tps1-1 embryo growth. Our data establish for the first time that an enzyme of trehalose metabolism is essential in plants and is implicated in the regulation of sugar metabolism/embryo development via a different mechanism to that reported in S. cerevisiae.     

Molecular cloning and expression analysis of chicken MyD88 and TRIF genes.

Toll-like receptors (TLRs) trigger the innate immune system by responding to specific components of microorganisms. MyD88 and TRIF are Toll/interleukin (IL)-1 (TIR)-domain containing adapters, which play essential roles in TLR-mediated signalling via the MyD88-dependant and -independent pathways, respectively. Genes encoding several TLRs have been identified in the chicken genome, however, elements of their signalling pathways have not been well characterized. Here we describe the cloning of chicken MyD88 and TRIF orthologs, and examine the spatial and temporal expression of these genes. The chicken MyD88 cDNA was shown to have an open reading frame (ORF) of 1104 bp, encoding a predicted protein sequence of 368 aa, 8 aa short of a previously published coding sequence due to a premature stop codon. MyD88 gene expression was detected in each tissue tested except in muscle. The chicken TRIF cDNA possessed an ORF of 2205 bp, encoding a predicted protein sequence of 735 aa, which shared 37.3% similarity and 28.9% identity to human TRIF protein sequence. TRIF was ubiquitously expressed in all tissues.     

Case studies of motion-sensing cameras to study clutch survival and fate of real and artificial ground-nests in Australia

Capsule: Trail cameras monitoring clutches of ground-nesting birds in Australia revealed survival rates and new causes of egg loss. We also show that nests with artificial eggs versus real eggs do not reveal the same information on predators.

Aims: We describe the application of trail cameras for monitoring real and artificial clutches of ground-nesting birds through a series of case studies. We rate the degree of inference used when defining nest outcomes and assigning fates.

Methods: Four case studies are presented, based on 326 deployments of cameras on real and artificial nests.

Results: The probability of hatching varied between species and populations (40.0–83.3% hatched), but not between urban and rural habitats. The ‘degree of inference’ scores did not differ between species and contexts. Two case studies which examined habitat-mediated survival (ecological hypotheses) found no difference in survival between urban and rural habitats, nor between open and covered microhabitats. Another case study (a management hypothesis) found that predator exclusion cages increased clutch survival even though predators sometimes breached the cages and cages altered the assemblage of predators visiting the area. A fourth study revealed that the assemblage of predators eating eggs differed between real and artificial nests.

Conclusion: Cameras enabled the survival and fate of most nests to be determined.     

4,7-Dichloro benzothien-2-yl sulfonylaminomethyl boronic acid: First boronic acid-derived beta-lactamase inhibitor with class A,C, and D activity

4,7-Dichloro-1-benzothien-2-yl sulfonylaminomethyl boronic acid (DSABA, Compound I) was discovered as the first boronic acid-based class D beta-lactamase inhibitor. It exhibited an IC₅₀ of 5.6 μM against OXA-40. The compound also inhibited class A and C beta-lactamases with sub to low μM IC₅₀, and synergized with imipenem against Acinetobacter baumannii.